JP2011102731A - Ellipsometry device - Google Patents

Abstract

In addition to being able to observe the microstructure of an object with high contrast and high magnification, it is for a measuring means or an operating means used in contact with or close to the object surface at a position on the normal direction observation side with respect to the object surface. To provide an ellipsometry device that can secure a working space.
An ellipsometry microscope includes a light source, a polarizer, and a phase compensator, and an oblique illumination system that obliquely illuminates illumination light L4 onto a sample surface SP, an imaging system, an analyzer 23, And an image sensor 24 that detects an image formed by the imaging system on the detection surface 25. The imaging system includes a plurality of stages of a primary imaging system 10 including an objective lens 21 and a secondary imaging system 11 including an imaging lens 22. By setting the magnification M1 (for example, 1 ×) of the objective lens 21 to be relatively smaller than the magnification M2 (for example, 100 ×) of the imaging lens 22, the optical axis AX1 of the objective lens 21 and the primary imaging system An angle θ1 formed with 10 image planes P1 is set to be relatively large.
[Selection] Figure 2

Description

  The present invention relates to an ellipsometry apparatus such as an ellipsometer or an ellipsometry microscope using an ellipsometric method (ellipsometry) capable of observing the film thickness distribution of an object such as a thin film.

  In next-generation hard disk drives, it is expected that the head will move to a lubrication system that travels in contact with the disk. In this case, a uniform lubricating film with a thickness of about 1 nm is required to be applied to the surface of the disk. . Further, in nanoimprint lithography, a uniform thin film for transferring a fine pattern using a liquid thin film of the order of nm is required. Even in polymer electronics, a uniform liquid molecule thin film that needs to be patterned to form fine elements is required. In either case, the ultra-thin film thickness distribution must be quantitatively measured accurately and efficiently.

  Conventionally, a scanning ellipsometer (ellipsometer) as shown in FIG. 6 has been widely used to observe the distribution of a liquid or solid thin film (for example, Patent Document 1). Such an ellipsometer 101 is converted into parallel light by a light collimation lens 103 irradiated from a light source 102, converted into linearly polarized light by a polarizer 104, converted into circularly polarized light or elliptically polarized light by a λ / 4 plate 105, and used for scanning a sample. Illumination light 109 is applied to a thin film 108 (liquid film or solid film) on a substrate 107 placed on the stage 106. The sample thin film 108 is sequentially scanned by the sample scanning stage 106. The illumination light 109 is reflected by the thin film 108, and the reflected light 110 passes through the objective lens 111, passes through the analyzer 112, enters the light detection device 114 through the imaging lens 113, and is measured.

  In an ellipsometry apparatus, when light is reflected at a certain incident angle at the interface between a sample and air or the like, a complex amplitude reflection of a polarized light component parallel to the incident plane (p-polarized light) and a vertical polarized light component (s-polarized light). Since the rate depends on the film thickness that determines the refractive index of the sample thin film, a light reflection intensity image corresponding to the film thickness distribution of the thin film can be obtained, and the film thickness distribution at each point of the sample can be observed.

By the way, in the ellipsometry apparatus, when light is reflected at the interface between the sample (refractive index ns) and air (refractive index no), the Brewster angle in which the incident angle of light is obtained by θB = tan ⁻¹ (ns / no). It is set and used near θB. In this setting, since the reflectance for p-polarized light takes the minimum value, the difference between the complex-amplitude reflectances of p-polarized light and s-polarized light becomes the largest, and a film distribution image having the best contrast can be obtained. Since the Brewster angle θB is generally in the vicinity of 60 to 70 degrees for liquids and solids, in an ellipsometry microscope, a relatively large incident of about 60 to 70 degrees from the normal so as to minimize the reflectance for p-polarized light. It was necessary to irradiate the sample with illumination light at an angle and to observe the reflected light reflected at an angle of reflection similar to the incident angle from an oblique direction. Therefore, in the ellipsometry apparatus, it is necessary to employ an oblique illumination system as shown in FIG. 6 and to arrange the optical axis of the objective lens 111 of the imaging system obliquely with respect to the sample surface of the thin film.

  When the sample is observed obliquely in this way, there is a problem that only a narrow field of view can be obtained due to the depth of focus. Thus, in the observation system in which the optical axis of the objective lens 111 is arranged obliquely with respect to the sample surface, a practically useful field of view cannot be secured, and suitable high-magnification observation is difficult.

  In addition, a high-power objective lens generally has a small working distance. For this reason, in an observation system in which the optical axis of the objective lens 111 is arranged obliquely with respect to the sample surface, in order to avoid contact between the objective lens and the sample substrate, the sample is observed away from the lens at a low magnification, or p-polarized light. It was necessary to irradiate light at an angle of incidence that deviated from the condition that the reflectance with respect to the minimum was observed, and to observe with low contrast.

  In order to solve this kind of problem, Patent Document 1 has proposed an ellipsometry microscope (ellipsometer) shown in FIG. In the ellipsometry microscope 121 shown in FIG. 7, the oblique illumination system includes a light source 122, an optical fiber 123, a collimating lens 124, a polarizer 125, a phase compensator 126, a condensing lens 127, a beam splitter 128, and the like. Further, the imaging system is configured by an objective lens 129, an imaging lens 130, an analyzer 131, and a detection surface 133 of the imaging device 132. The oblique illumination system and the imaging system share the same objective lens 129, and the optical axis of the objective lens 129 is arranged perpendicular to the sample surface 134 of the sample S.

  The diffused light emitted from the light source 122 through the optical fiber 123 is converted into parallel light by the collimator lens 124, linearly polarized light by the polarizer 125, and elliptically polarized light (including circularly polarized light) by the phase compensator 126 made of a λ / 4 plate. It is said.

  Illumination light composed of elliptically polarized light collected by the condenser lens 127 is bent by the beam splitter 128 and irradiates the sample S as parallel light through a position shifted from the optical axis of the objective lens 129. The reflected light R1 specularly reflected by the sample S passes through the beam splitter 128 through the position shifted to the objective lens 129 to the side different from the incident time with respect to the optical axis, and passes through the imaging lens 130 and the analyzer 131. After that, the detection surface 133 of the imaging device 132 is irradiated. Then, the sample image picked up by the image pickup device 132 is displayed on the monitor 135.

  Thus, since the optical axis of the objective lens 129 is arranged perpendicular to the sample surface 134 of the sample S, the problem of narrowing the field of view is solved. In addition, since the incident angle of light with respect to the sample surface can be set in the vicinity of the Brewster angle θB, a film distribution having a minute film thickness difference can be observed with high sensitivity and high contrast (high resolution).

JP 2009-192331 A

  By the way, since the ellipsometry microscope is an optical observation method, non-contact observation is possible and it is not necessary to contact the sample. Therefore, with the apparatus having the configuration shown in FIG. 6, a working space for other measurement or operation means can be secured at a position on the normal direction observation side with respect to the sample surface. Many functions can be realized by the combination. One example is a microscope that combines a scanning probe microscope and an ellipsometry microscope. In this microscope, taking advantage of the high-speed image acquisition speed of an ellipsometry microscope, a wide area of the sample surface is observed, and a narrow area of interest is observed in detail with a probe microscope, enabling efficient and accurate observation. it can. In some cases, it is desired to dynamically observe the state of the response by performing an operation of applying a mechanical stimulus by sliding an operating means such as a probe on a thin film having viscoelasticity.

  However, in the ellipsometry microscope shown in FIG. 7 described in Patent Document 1, since the objective lens is arranged perpendicularly to the sample surface, this objective lens hinders the scanning for contacting the sample surface. There has been a problem that work spaces such as measuring means such as probes and operating means such as sliding probes cannot be secured.

  The present invention has been made paying attention to such problems existing in the prior art, and its purpose is to enable observation of the microstructure of an object with high contrast and high magnification, and to apply a method to the object surface. An object of the present invention is to provide an ellipsometry apparatus capable of ensuring a work space for measuring means, operating means, etc. used in contact with or close to an object surface at a position on the line direction observation side.

  In order to solve the above-mentioned problem, the present invention according to claim 1 is an ellipsometry apparatus capable of magnifying and observing an image of an object to be observed using ellipsometry, and a polarizer on the optical path of a light source. And a phase compensator, and an oblique illumination system that obliquely irradiates the object with parallel light that has passed through the polarizer and the phase compensator. An imaging system for imaging, an analyzer provided in the middle of the optical path of the reflected light in the imaging system, and an imaging device for imaging an image formed by the imaging system, The system includes a primary imaging system including at least one lens that forms an object image at a first magnification by incident reflected light from the object, and an object image formed by the primary imaging system. Secondary imaging including at least one lens that magnifies at a second magnification greater than the first magnification When, and summarized in that with a.

  According to this configuration, the imaging system includes a primary imaging system that forms an object image at a first magnification by incident reflected light from the object, and an object at a second magnification that is greater than the first magnification. Since it is composed of a plurality of stages with the secondary imaging system for enlarging the image, the first magnification in the primary imaging system that receives the reflected light from the object can be set relatively small. For this reason, it is possible to relatively increase the angle between the optical axis of the primary imaging system and its imaging plane, which depends on the first magnification. Then, the object image formed on the imaging plane that forms a relatively large angle with respect to the optical axis of the primary imaging system is magnified at the second magnification by the secondary imaging system. Therefore, it is possible to observe the microstructure of the object with high contrast and high magnification, as well as for measuring means and operating means used in contact with or close to the object surface at a position on the normal direction observation side with respect to the object surface. Work space can be secured.

  According to a second aspect of the present invention, in the ellipsometry apparatus according to the first aspect, the optical axis of the secondary imaging system is arranged so as to be substantially perpendicular to the imaging plane of the primary imaging system. In addition, the gist of the present invention is that the imaging element is arranged so that the imaging plane of the secondary imaging system substantially overlaps the detection plane of the imaging element.

  According to this configuration, when the angle between the object plane and the optical axis of the primary imaging system is an acute angle as in the primary imaging system, the reflectance of light to the lens of the secondary imaging system is increased. There is a limit to the magnification that can be set in the primary imaging system because of the need to reduce it. On the other hand, since the optical axis of the secondary imaging system is arranged so as to be substantially perpendicular to the imaging surface of the primary imaging system, there is no such restriction and the secondary imaging system is high. Can be set to magnification. Since the imaging device is arranged so that the imaging surface of the secondary imaging system substantially overlaps the detection surface, the imaging device can capture an image with high contrast, high magnification, and more uniform luminance distribution.

  According to a third aspect of the present invention, in the ellipsometry apparatus according to the first or second aspect, an angle θo between the optical axis of the primary imaging system and the object plane, the optical axis and the primary imaging system. The angle M1 of the primary imaging system is set to a value that allows the angle θ1 to be 20 degrees or more when M1 = tan θo / tan θ1. .

  According to this configuration, since the primary imaging system is set to a magnification M1 (= tan θo / tan θ1) that can make the angle θ1 20 degrees or more, the angle θ1 is set to a relatively large value of 20 degrees or more. By doing so, it is possible to reduce the reflectance of light incident on the lens of the secondary imaging system from the primary imaging system. Therefore, a bright image can be formed on the image sensor by the secondary imaging system.

  According to a fourth aspect of the present invention, in the ellipsometry apparatus according to any one of the first to third aspects, the magnification M1 of the primary imaging system is a value within a range of 0.3 to 3 times. The gist is that it is set.

  According to this configuration, since the magnification M1 is set to a value within the range of 0.3 to 3 times, the angle formed between the optical axis of the primary imaging system and the imaging plane of the primary imaging system is set. It can be set to a relatively large value. Therefore, the reflectance of light incident on the lens of the secondary imaging system from the primary imaging system can be reduced, and a bright image can be formed on the image sensor by the secondary imaging system.

  According to a fifth aspect of the present invention, in the ellipsometry apparatus according to the third or fourth aspect, an angle θo between the optical axis of the primary imaging system and the object plane, the optical axis and the primary imaging. The angle θ1 formed with the imaging plane of the system satisfies θo ≧ θ1, and the magnification M1 of the primary imaging system determined by M1 = tan θo / tan θ1 is set to 1 or more.

  According to this configuration, for example, if the magnification of the primary imaging system is less than 1, even if the magnification of the secondary imaging system is increased, the magnification of the entire imaging system is the same as that of the secondary imaging system. Although the magnification cannot be obtained, since the magnification of the primary imaging system is 1 or more, a magnification higher than that of the secondary imaging system can be obtained as the magnification of the entire imaging system.

  According to a sixth aspect of the present invention, in the ellipsometry apparatus according to any one of the first to fifth aspects, the illumination light is applied to the object at an incident angle such that the reflectance of the object with respect to p-polarized light is substantially minimized. Observation or film thickness distribution measurement is performed by irradiation, and the optical axis of the primary imaging system is the optical axis when the optical axis of the reflected light from the object plane assumes a minimum reflection angle. The gist of the present invention is that they are inclined by a twist angle Δθ in a direction away from the object plane.

  According to this configuration, a large angle θo formed by the optical axis of the primary imaging system and the object plane can be secured, so that the primary imaging system represented by M1 = tan θo / tan θ1 for a large angle θ1. The magnification M1 is not so small.

  According to the present invention, the microstructure of an object can be observed with high contrast and high magnification, and the measuring means and operating means used in contact with or in proximity to the object surface at a position on the normal direction observation side with respect to the object surface The effect that the work space for such as can be secured is obtained.

The schematic side view which shows the whole structure of the ellipsometry microscope of 1st Embodiment. The schematic side view which shows the principal part of an ellipsometry microscope. The schematic side view which shows an imaging system. The schematic side view which shows the principal part of the ellipsometry microscope in 2nd Embodiment. The schematic side view which shows an imaging system. Schematic diagram showing a conventional scanning ellipsometer. FIG. 7 is a schematic cross-sectional view showing a conventional scanning ellipsometer different from FIG. 6.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is embodied in an ellipsometry microscope will be described with reference to FIGS. In the present embodiment, the ellipsometry microscope constitutes a part of the composite microscope.

  FIG. 1 is a schematic diagram showing an overall configuration of an ellipsometry microscope in a composite microscope. As shown in FIG. 1, an ellipsometry microscope 1 as an ellipsometry apparatus constitutes a composite microscope 80 in combination with a scanning probe microscope 70 (Scanning Probe Microscope (SPM)). In the composite microscope 80, the ellipsometry microscope 1 observes the thin film 3 formed on the substrate 2 of the sample S at a low magnification in a relatively wide field of view, and particularly a spot of interest for which a fine structure is to be observed is a scanning probe microscope. 70 enables observation at a high magnification. In the present embodiment, an atomic force microscope (AFM) is employed as an example of the scanning probe microscope 70.

  As shown in FIG. 1, the ellipsometry microscope 1 includes an oblique illumination system 4 and an imaging system 5. The imaging system 5 of the present embodiment includes a primary imaging system 10 and a secondary imaging system 11. Hereinafter, the oblique illumination system 4 and the imaging system 5 will be described in this order.

  As shown in FIG. 1, the oblique illumination system 4 includes a light source 12, an optical fiber 13, a collimating lens 14, a polarizer 15, a phase compensator 16, and a lens 17. The illumination light generated by the light source 12 is guided by the optical fiber 13 and is emitted as illumination light L1 that is diffuse light as a substantially point light source at a predetermined position, and is converted into illumination light L2 that is parallel light by the collimator lens 14. The illumination light L2 becomes the illumination light L3 that has been linearly polarized by the polarizer 15. The illumination light L4 that is elliptically polarized light (including circularly polarized light) is obtained by the phase compensator 16 formed of a λ / 4 plate. The illumination light L4 is irradiated on the sample surface of the sample S as parallel light through the collimating lens 17.

The thin film 3 formed on the substrate 2 of the sample S is a liquid film or a solid film. In addition, the ellipsometry microscope 1 is configured to irradiate the sample S by configuring a stage (not shown) on which the sample S is placed to be tiltable or changing the light irradiation angle of the oblique illumination system 4. The incident angle of light can be adjusted. This incident angle is adjusted according to the refractive index determined by the material of the thin film 3, and normally, the Brewster angle θB = tan ⁻¹ (ns / no) (however, so that the reflectance for p-polarized light takes the minimum value. ns is set to a value in the vicinity of the refractive index ns of the sample, and no is the refractive index of air). For example, when the sample S is a silicon substrate, the Brewster angle θB is about 74 degrees. When the sample S includes a material that absorbs light such as metal, the reflectance for p-polarized light is not completely zero, but generally the reflectance for p-polarized light has a minimum value at an incident angle of about 60 to 70 degrees. . For this reason, the illumination light L4 is irradiated to the sample surface of the sample S at a relatively large incident angle of usually 60 to 80 degrees.

  Next, the imaging system 5 will be described. As shown in FIG. 1, the imaging system 5 includes a primary imaging system 10 and a secondary imaging system 11. The primary imaging system 10 has one objective lens 21. The secondary imaging system 11 has one imaging lens 22. As the imaging lens 22, an objective lens for secondary imaging is used.

  Here, as shown in FIG. 1, the primary imaging system 10 is an imaging system including an objective lens 21 on which reflected light from the sample S first enters, and its magnification M1 (first magnification). Is a relatively low magnification. The secondary imaging system 11 enlarges an object image formed on the imaging surface of the primary imaging system 10 (hereinafter referred to as “primary imaging plane P1”) to a desired magnification, This is an imaging system that forms the enlarged object image on the detection surface 25 of the image sensor 24 that coincides with the imaging plane (hereinafter referred to as “secondary imaging plane P2”), and its magnification M2 (second magnification) ) Is a relatively high magnification. The primary imaging system 10 and the secondary imaging system 11 each include at least one imaging lens. In particular, in the present embodiment, the primary imaging system 10 and the secondary imaging system 11 are connected to each other. In this example, one image lens is provided.

As shown in FIG. 1, illumination light L <b> 4 (hereinafter also referred to as “incident light L <b> 4”) irradiated on the sample S is reflected by the sample S to become reflected light R <b> 1 that is reflected light, and enters the objective lens 21. The reflected light R1 (however, only the optical path of the reflected light (scattered light) at the optical axis of the incident light L4 is shown in FIG. 1) is once condensed by the objective lens 21 and then diffused again. Become. The lens barrel 26 that holds the objective lens 21 also functions as a diaphragm of the imaging system 5. The diffused reflected light R2 is incident on a range in the lens barrel 27 of the imaging lens 22, is condensed by the imaging lens 22 to be reflected light R3, and the reflected light R4 that has passed through the analyzer 23 is imaged. The detection surface 25 of the element 24 is irradiated. The reflected light R4 applied to the detection surface 25 of the image sensor 24 is converted into an electrical signal, and an enlarged object image (enlarged image of the thin film 3) is displayed on the monitor 28 formed of a liquid crystal display.
Next, each component of the present ellipsometry microscope will be described in detail with reference to FIGS.
(light source)

The light source 12 is configured by an SLD (Super Luminescent Diode). If a light source such as a He-Ne laser or a laser with a long coherence distance (coherence length) such as an LD (Laser Diode) is used as the light source, part of the light is reflected by the optical elements that make up the device optical system. As a result, optical interference occurs and an interference fringe image appears. For example, it is assumed that light reflected by the phase compensator 16 composed of a λ / 4 plate and traveling backward is further reflected by the polarizer 15 and travels forward again to reach the detection surface. At this time, there is also light that reaches the detection surface at the same time by light traveling straight without passing through these reflections. Since the light that has passed through these reflections and the light that has traveled straight without passing through the light travels through different optical path lengths, the phases are different and optical interference occurs on the detection surface. That is, at this time, an interference fringe image is generated on the detection surface, and a noise image is generated by being superimposed on the thin film image. Here, in general, lights having an optical path difference larger than the coherence distance do not interfere with each other. Therefore, when a light source whose coherence distance is sufficiently smaller than the distance between optical elements constituting the apparatus is used, generation of interference fringe images can be suppressed. This light source 12 is constituted by a laser SLD having a short coherence distance. The distance between the optical elements constituting the apparatus optical system is on the order of 1 mm to 10 cm, whereas the coherence distance of the SLD is on the order of 10 μm and is sufficiently small. Instead of the SLD, the light source 12 may be configured by a white light source using a fiber laser or a halogen lamp, an ASE (Amplified Spontaneous Emission), an LED (Light Emitting Diode), or the like.
In FIG. 1, the single collimating lenses 14 and 17 are schematically illustrated, but various optical elements and optical instruments that generate accurate parallel light may be used.
(Polarizer)

The polarizer 15 can convert the illumination light L2 into a linearly polarized light using a known polarizing plate, is provided so as to be rotatable with respect to the optical axis of the illumination light L2, and can change the direction of the linearly polarized light within a range of 90 degrees. .
(Phase compensator)

The phase compensator (compensation center) 16 converts linearly polarized light into elliptically polarized light. The phase compensator 16 of this embodiment is composed of a λ / 4 plate (¼ wavelength plate). Although it depends on the light source, in this embodiment, since an SLD light source having a wide spectrum is used, an uncolored achromatic retarder is used. An ideal phase compensator is an optical phase retarder whose retardation is exactly 90 degrees (or ¼ wavelength), but the exact retardation changes depending on the optical axis and wavelength. Difficult to use for Therefore, in the present embodiment, a combination of the rotating polarizer 15 and the rotating phase compensator 16 is used, and unpolarized light can be converted into any elliptically polarized light.
(Image sensor)

The image sensor 24 is an array element in which charge coupled devices (CCD) are arranged in a matrix. The imaging device is not limited to the CCD, and may be configured using a CMOS (complementary metal oxide semiconductor) image sensor. Further, a cooled CCD camera is preferable because it has less thermal noise.
(Imaging system)

  Next, the primary imaging system 10 and the secondary imaging system 11 which are characteristic configurations in the present embodiment will be described. FIG. 2 is a schematic side view of portions related to the primary imaging system and the secondary imaging system. As shown in FIG. 2, the objective lens 21 constituting the primary imaging system 10 has an angle θo formed between the optical axis AX1 and the sample surface SP (in other words, the sample mounting surface of the stage) so that the reflected light R1. The optical axis AX1 is slightly inclined with respect to the optical axis AX2 so as to be larger than the reflection angle θref that is an angle formed by the optical axis AX2 and the sample surface SP. That is, a “twist” is added to incline the optical axis AX1 of the objective lens 21 toward the side away from the sample surface SP by an angle Δθ (= θo−θref) with respect to the optical axis AX2 of the reflected light R1. Hereinafter, the angle Δθ is referred to as a twist angle.

  The reflected light R2 collected through the objective lens 21 forms an image in a space before reaching the imaging lens 22. That is, the imaging plane (primary imaging plane P1) of the objective lens 21 is formed in the space between the objective lens 21 and the imaging lens 22. The imaging lens 22 is arranged so that its optical axis AX3 is perpendicular to the primary imaging plane P1 (θ2 = 90 ° in FIG. 2). The image sensor 24 is arranged such that the center axis AX4 of the detection surface 25 coincides with the optical axis AX3 of the imaging lens 22.

When the focal length of the imaging lens 22 is set to f1, the imaging lens 22 has a principal plane whose rear side is the normal direction (optical axis AX3 direction) with respect to the primary imaging plane P1 (right side in FIG. 2). Are arranged so as to be separated by a distance (x1 + f1). The imaging element 24 is arranged such that the detection surface 25 is located a distance (f1 + x2) away from the main plane of the imaging lens 22 in the normal direction (optical axis AX3 direction). Yes. It should be noted that, in x1, x2 is, a relationship of x1 · x2 = f1 ^2.

  The imaging lens 22 has a function of enlarging the object image formed on the primary imaging plane P <b> 1 and forming an image on the detection surface 25 of the image sensor 24. For this reason, the image sensor 24 is arranged so that its detection surface 25 coincides with the secondary imaging plane P2. That is, the distance x2 in FIG. 2 is set to a distance obtained by subtracting the focal length f1 of the imaging lens 22 from the distance between the main plane of the imaging lens 22 and the secondary imaging plane P2.

In this embodiment, the magnification M1 of the objective lens 21 constituting the primary imaging system 10 is set smaller than the magnification M2 of the imaging lens 22 constituting the secondary imaging system 11 (M1 <M2). . The reason for this setting is as follows.
When the angle formed by the optical axis AX1 of the objective lens 21 and the primary imaging plane P1 is θ1, the following relationship is established between the magnification M1 of the objective lens 21 and the angles θo and θ1.
tanθ1 / tanθo = 1 / M1 (1)

From this equation (1), as the magnification M1 of the objective lens 21 is increased, the angle θ1 becomes smaller than the angle θo. As the angle θ1 decreases, the primary imaging plane P1 gradually tilts clockwise in FIG. 2 around the intersection with the optical axis AX1. Since this angle θ1 is equal to the angle formed between the main plane of the imaging lens 22 and the optical axis AX1, the smaller the angle θ1, the incident angle of the reflected light R2 with respect to the imaging lens 22 (with the main plane of the imaging lens 22). The angle formed by the reflected light R2 is increased. When the incident angle of the reflected light R2 increases, the light reflectance at the imaging lens 22 increases.

  For example, when the angle θo is set to 30 degrees, if the magnification M1 is increased to 100 times, the reflected light R2 that is substantially parallel to the main plane of the imaging lens 22 with an angle θ1 = 0.3 degrees is obtained from the equation (1). End up. In this case, the reflected light R <b> 2 is blocked by the lens barrel 26 of the imaging lens 22, and the reflected light R <b> 2 can not enter even the imaging lens 22. Even if the reflected light R2 can be incident on the imaging lens 22 without being blocked by the lens barrel 26, the incident angle is considerably large. Therefore, the reflectance of the reflected light R2 on the surface of the imaging lens 22 is s. It increases significantly to about 0.98 for polarized light and about 0.96 for p-polarized light. In this case, the image formed on the detection surface 25 becomes extremely dark.

  For this reason, in this embodiment, in order to avoid this kind of increase in reflectance, the magnification M1 of the objective lens 21 is set to be relatively small, and the angle θ1 determined from the magnification M1 and the equation (1) is set as a relative value. Is set to a large value. In order to keep the reflectance of the reflected light R2 within a permissible range, the angle θ1 is preferably set to 20 degrees or more, for example. In the present embodiment, the angle θ1 is set to 45 degrees as an example.

  For example, when the incident angle of the incident light L4 is 60 to 80 degrees near the Brewster angle θB, the reflection angle θref of the optical axis AX2 of the reflected light R1 specularly reflected by the sample surface SP is 60 to 80 degrees. At this time, the optical axis AX1 of the objective lens 21 (that is, the optical axis of the primary imaging system 10) is set to be larger than the optical axis AX2 at the assumed minimum reflection angle θrefmin (= 60 degrees) of the regular reflection light R1. They are arranged so as to be inclined by a twist angle Δθ (> 0) in a direction away from the sample surface SP (counterclockwise in FIG. 2). For this reason, when the incident light L4 with respect to the sample surface SP is used at an assumed incident angle (60 to 80 degrees), the optical axis AX1 of the objective lens 21 is always farther from the sample surface SP than the optical axis AX2 of the reflected light R1. An angle θo larger than the reflection angle θref can be secured. When the twist angle Δθ is added in this way, the reflected light R1 from the sample surface SP passes through the position shifted from the center of the objective lens 21 to the sample S side as shown in FIGS. Is incident on the objective lens 21.

  In this embodiment, as an example, the twist angle Δθ is set to 15 degrees, and the angle θo (= 90 ° −θrefmin + Δθ) is set to 45 degrees. In this case, the magnification M1 at which the angles θo and θ1 are both 45 degrees is 1 since M1 = tan θo / tan θ1 from the equation (1). For this reason, in the present embodiment, the objective lens 21 having a magnification M1 of 1 is used. Of course, the magnification M1 is not limited to 1. The magnification M1 that can make the angle θ1 a relatively large value (for example, 20 degrees or more) can be adopted from the relationship between the angle θo and the equation (1). Further, the angle θ1 is not limited to 20 degrees or more, and the reflected light R2 can enter the imaging lens 22 without being blocked by the lens barrel 27, and the reflectance of the reflected light R2 at the imaging lens 22 can be suppressed to a certain extent. For example, it may be less than 20 degrees.

  The angle θo is preferably in the range of 20 to 60 degrees. At this time, the twist angle Δθ is not necessarily set. For example, when the angle θo is set in a range of 20 ≦ θo <30, the twist angle Δθ may be 0 degree. When the angle θo is set in the range of 30 ≦ θo ≦ 60, the twist angle Δθ may be set in the range of 0 <Δθ ≦ 30. Then, when the angle θo takes a value within the range of 20 to 60 degrees, the magnification M1 (= tan θo /) that ensures the angle θ1 within the range of 20 to 70 degrees, preferably within the range of 30 to 60 degrees. It is desirable to set to tan θ1).

  The magnification M1 is, for example, in the range of 0.1 to 5 times, preferably 0.3 to 3 times. Of course, the magnification M1 is not limited to this range, and may be less than 0.1 times (0 <M1 <0.1) or more than 5 times. However, if the magnification M1 of the objective lens 21 is set to a value less than 1, it is necessary to increase the magnification M2 of the imaging lens 22 in order to secure a desired magnification M in the ellipsometry microscope 1, and the magnification M2 is also increased. Since there is a limit, it is not preferable to make the magnification M1 too small. In this respect, the magnification M1 is preferably 0.8 times or more, particularly preferably 1 time or more.

  Further, since the magnification M1 is determined from M1 = tan θo / tan θ1, it is necessary to satisfy θo ≧ θ1 in order to make the magnification M1 1 or more. At this time, by adding the twist angle Δθ to increase the angle θo, the upper limit of the angle θ1 that can ensure a magnification M1 of 1 or more can be increased. In the present embodiment, as an example, an upper limit of the angle θ1 that can ensure a magnification M1 of 1 or more is employed (θo = θ1). Of course, even when the magnification M1 is less than 1, by setting the angle θo by adding the twist angle Δθ, the magnification M1 is unlikely to be reduced for a larger angle θ1. Therefore, it is desirable to set the angle θo to 30 degrees or more.

  As shown in FIG. 2, in the secondary imaging system 11, the distance between the main plane of the imaging lens 22 and the primary imaging plane P <b> 1 is represented by x <b> 1 + f <b> 1. The distance to is indicated by f1 + x2. That is, x1 is a value obtained by subtracting the focal length f1 (front focal length) of the imaging lens 22 from the distance between the main plane of the imaging lens 22 and the primary imaging plane P1, and x2 is the imaging lens 22. This is a value obtained by subtracting the focal length f1 (rear focal length) of the imaging lens 22 from the distance between the main surface and the detection surface 25.

Here, the ratio of the heights of the primary object image formed on the primary imaging plane P1 and the secondary object image formed on the detection plane 25 (secondary imaging plane P2). That is, the image magnification M2 of the secondary imaging system 11 is given by the following equation, where f1 is the focal length of the imaging lens 22 and x1 is the distance given in FIG.
M2 = f1 / x1 (2)

From this equation (2), the image magnification M2 can be set without depending on the angle θ1, and high magnification observation becomes possible. That is, the image magnification M2 of the secondary imaging system 11 can be set by the focal length f1 and the distance x1 of the imaging lens 22.

  As described above, an objective lens having a magnification (for example, 100 times) larger than the magnification M1 of the objective lens 21 is used for the imaging lens 22. The magnification M of the ellipsometry microscope 1 is expressed by M = M1 × M2 using the magnification M1 of the primary imaging system 10 and the magnification M2 of the secondary imaging system 11. In this embodiment, the distance x1 (= f1 / M2) determined from the focal length f1 of the imaging lens 22 and the equation (2) is set so that the magnification M2 (= M / M1) is obtained. . When the magnification M of the ellipsometry microscope 1 is 100 times, for example, in this example in which the magnification M1 of the objective lens 21 is 1, the distance x1 (= f1 / M2) is adjusted so that the magnification M2 is 100 times. This distance x1 is represented by x1 = f1 · M1 / M using magnifications M1 and M. In addition, it is preferable to adjust the distance x1 so that all the reflected light R2 that has passed through the objective lens 21 enters the range of the imaging lens 22. The magnification M2 is not limited to 100 times, and an appropriate magnification can be set such that M1 × M2 becomes the magnification M required for the ellipsometry microscope 1. In setting the magnification M of the ellipsometry microscope 1 to an appropriate high magnification, the magnification M2 is preferably a magnification that is 10 times or more and 10 times or more of the magnification M1.

  As described above, the configuration of the ellipsometry microscope 1 of the present embodiment is such that a secondary imaging system is added to the imaging system of FIG. 6 described in the prior art, and the film distribution of the thin film 3 is spatially (primary imaging). The image is formed as a primary object image on the plane P1), and is magnified and observed by the secondary imaging system 11. The optical axis AX3 of the secondary imaging system 11 is arranged so as to be perpendicular to the imaging plane P1 of the primary imaging system 10 (θ2 = 90 ° in FIG. 2). As a result, the primary imaging surface P1 and the secondary imaging surface P2 can be arranged as surfaces perpendicular to the optical axis AX3 of the secondary imaging system 11. Although the magnification M1 of the primary imaging system 10 cannot be increased due to the reason described using the equation (1), the secondary imaging system 11 uses the primary object image and the secondary object image as light. Since it can be arranged in the planes P1, P2 perpendicular to the axis AX3, a large value can be set as the image magnification. In the secondary imaging system 11, the primary object image and the secondary object image can be arranged in a plane perpendicular to the optical axis AX3 regardless of the magnification M2 (that is, even when the magnification M changes). For example, when at least one of the primary imaging plane P1 and the secondary imaging plane P2 is at an angle deviating from the perpendicular to the optical axis AX3, the secondary imaging plane P2 is detected by the change in the magnification M2. This makes an angle with 25. In this case, as the angle formed becomes larger, the high-contrast visual field region becomes narrower or the luminance distribution becomes uneven. However, in this example, even if the image magnification M2 (= f1 / x1) is changed, the primary image formation plane P1 and the secondary image formation plane P2 are always kept parallel. Widely secured.

  Further, the objective lens 21 needs to have a larger numerical aperture NA as its magnification increases. Generally, as the magnification increases, the lens diameter increases and the working distance decreases. For this reason, the lens constituting the imaging system 5 is divided into an objective lens 21 constituting the primary imaging system 10 and an imaging lens 22 (objective lens) constituting the secondary imaging system 11. By setting the magnification M1 of 21 small, the numerical aperture NA of the objective lens 21 can be reduced. For this reason, a small lens having a small lens diameter can be used as the objective lens 21, and a long working distance WD can be secured. From this point, it becomes easy to avoid interference (contact) between the objective lens 21 and the sample S.

In the present embodiment, a space in which the oblique illumination system 4 and the imaging system 5 are not arranged is secured at a position on the normal direction observation side with respect to the sample surface SP (that is, the sample placement surface of the stage). In this space, a probe 71 of the scanning probe microscope 70 and a displacement system 72 for displacing the probe 71 are arranged. That is, a space on the normal direction observation side with respect to the sample surface SP is secured as a work space (arrangement space) for the probe 71 of the scanning probe microscope 70 and its displacement system 72.
(Measurement procedure)
Next, the procedure of sample observation and film thickness distribution measurement in the ellipsometry microscope 1 configured as described above will be described.

First, the sample S is set, and the light source 12 and the monitor 28 are turned on. Subsequently, the polarizer 15, the phase compensator 16, and the analyzer 23 are set to initial positions. Then, while the polarizer 15 and the phase compensator 16 are rotated relative to each other, the contrast is confirmed on the monitor 28, and when a predetermined portion disappears, recording is performed. Alternatively, a series of operations are automatically performed, and the film thickness is calculated by a predetermined procedure using an image having the best contrast.
Here, the quenching ellipsometry, which is the principle of the present invention, will be described.

  When light is reflected at a certain interface between the sample and air at a certain incident angle, the complex amplitude reflectivity (rexp) for the polarized light component (p-polarized light) and the vertical polarized light component (s-polarized light) in the incident plane. (iδ) is different, and this difference depends on the refractive index of the thin film 3 on the surface of the sample S. Since the refractive index of the thin film 3 depends on the film thickness of the thin film 3, the ellipsometry microscope 1 uses p-polarized light. The film thickness distribution is obtained by measuring the distribution of the amplitude ratio Ψ (= rp / rs) and the phase difference Δ (= δp−δs) of the complex amplitude reflectance of s-polarized light and s-polarized light at each point of the sample. And δ subscripts p and s indicate p-polarized light and s-polarized light, respectively, and light intensity I (x, y) obtained from a point (x, y) of the sample detected by an ellipsometry microscope. y, θ) is given by:

ここで、ｒsはｓ偏光に対する振幅反射率、Ｉoは入射光強度、θは照明光の入射角、Ｐ、Ａはそれぞれ偏光子、検光子の回転角の設定値である。

Here, rs is the amplitude reflectivity for s-polarized light, Io is the incident light intensity, θ is the incident angle of the illumination light, and P and A are the set values of the polarizer and analyzer rotation angles, respectively.

  When the film distribution is measured using the quenching ellipsometry technique, first, the reflected light intensity from the substrate surface on which the sample thin film is not formed is adjusted to “0”. That is, the incident light is converted into linearly polarized light by the polarizer and changed to elliptically polarized light by the reflection on the substrate surface, and the quarter wavelength plate and the analyzer polarizing plate are again adjusted so as to be completely quenched. Explaining using Expression (3), the polarizer angle P and the analyzer angle A are adjusted so that 2P + Δ = π / 2 and ψcosA + sinA = 0, and the reflected light from the substrate surface is brought close to “0”. . Since the substrate surface has a substantially uniform reflectance distribution, this step is a step of quenching the light regularly reflected on the substrate surface (incident angle = reflected light having a reflection angle).

  Here, in the ellipsometry microscope 1, the vicinity of the incident angle that minimizes the reflectance with respect to p-polarized light is the incident angle that realizes the best image contrast. Since the complex amplitude reflectivity of p-polarized light and s-polarized light depends on the incident angle, and the amplitude ratio Ψ and the phase difference Δ depend on the incident angle θ, an image obtained by an ellipsometry microscope as shown in Equation (3). The light intensity also depends on the incident angle θ. Therefore, in the ellipsometry microscope 1, an incident angle θ = θB is set near the incident angle that minimizes the reflectance for p-polarized light, and then the polarizer angle P and the analyzer angle A are adjusted so as to obtain an optimum contrast. To do.

If the sample is made of a material that does not absorb light, such as a dielectric, and light is reflected at the interface between the sample (refractive index ns) and air (refractive index no), then θB = tan ⁻¹ (ns / no) At the Brewster angle θB, the reflectivity for p-polarized light is 0, but the incident angle dependence of the reflectivity for s-polarized light is smaller than that for p-polarized light, so the difference in reflectivity between p-polarized light and s-polarized light is the largest. growing. For this reason, in the ellipsometry microscope 1, the film distribution image having the best contrast is obtained by setting the incident angle in the vicinity of the Brewster angle θB.

  Next, the thin film 3 on the substrate 2 is observed using P and A adjusted above. Since the reflectance is different from that of the substrate 2 alone, that is, the amplitude ratio Ψ and the phase difference Δ are different from those of the substrate 2 alone, and the reflected light does not satisfy the extinction condition for P and A adjusted above. Is not 0. Since the amplitude ratio Ψ and the phase difference Δ depend on the refractive index of the thin film 3, that is, the film thickness, the intensity of the reflected light depends on the film thickness. Thus, a light intensity image corresponding to the film thickness distribution of the sample thin film is obtained. Thus, in the method using ellipsometry, the sample is irradiated with illumination light at a large incident angle of about 60 to 80 degrees from the normal so that the reflectance of the sample with respect to p-polarized light is minimized, and the reflected light is incident. Observe from an oblique direction near the reflection angle.

  In addition, in the ellipsometry microscope 1 using parallel light as illumination, the amplitude ratio Ψ and the phase difference Δ are obtained from the light intensity for the point (x, y) of the sample, and Ψ, Δ and the film of the sample thin film are further obtained. By using the thickness relationship, the light intensity of the image can be converted into a film thickness. For example, by measuring the light intensities I1 and I2 with respect to two polarizer angles P = P1 and P = P2 and substituting them into the equation (3) to solve the simultaneous binary equations, Ψ (x, y at each point of the sample , Θ), Δ (x, y, θ) can be obtained. The relationship between Ψ, Δ and the film thickness of the sample thin film is obtained by a general method such as an ordinary ellipsometer. From the relationship between Ψ, Δ and the film thickness of the sample thin film, the light intensity distribution I (x, y, θ) is converted into a film thickness distribution. Thus, the film thickness distribution of the thin film 3 can be measured by the ellipsometry microscope 1.

  In the composite microscope 80, the ellipsometry microscope 1 observes a wide field of view of the sample thin film 3 at a high magnification, and particularly a point of interest where a fine structure is to be observed is observed at a higher magnification by the scanning probe microscope 70. At this time, the displacement system 72 of the scanning probe microscope 70 is driven to lower the probe 71 and bring it into contact with the surface of the sample thin film 3. When the observation with the ellipsometry microscope 1 becomes unnecessary due to the switching to the observation with the scanning probe microscope 70, the objective lens 21 is retracted to the side away from the sample S within the operating range, and the probe 71 is wide. A work area may be secured. At this time, since the working distance WD of the objective lens 21 having a low magnification M1 is long, the working space of the probe 71 can be secured by retracting the objective lens 21.

Further, when the thin film 3 is a viscoelastic solid film or liquid film, the probe thin film 3 is contacted and slid by the probe 71 to give a mechanical stimulus, and the response state is moved by the ellipsometry microscope 1. It is also possible to obtain characteristics such as viscoelasticity of the thin film 3 by observing the target. Using the ellipsometry microscope 1 of the present embodiment, when the probe 71 is slid on the thin film 3 to give a mechanical stimulus, it is confirmed that the response of the thin film 3 to the mechanical stimulus of the probe 71 can be observed. It was done.
In the present embodiment, the following effects can be obtained.

  (1) In the ellipsometry microscope 1 of the present embodiment, the oblique illumination system 4 is adopted, and the imaging system 5 is composed of a plurality of stages of a primary imaging system 10 and a secondary imaging system 11. For this reason, the film thickness distribution of the thin film 3 can be observed with high contrast and high magnification, and the probe of the scanning probe microscope 70 is positioned at a position on the normal direction observation side with respect to the sample surface SP (the sample mounting surface of the stage). A working space for operating means such as 71, its displacement system 72, or a sliding probe can be secured. Therefore, the combined microscope 80 can be configured by combining the ellipsometry microscope 1 and the scanning probe microscope 70. In this case, the film thickness distribution and the like of the thin film 3 can be observed with a wide field of view at a high magnification with the ellipsometry microscope 1, and a point of interest where a fine structure is particularly desired can be observed with a scanning probe microscope 70 at a higher magnification. . In addition, a mechanical stimulus is applied to the thin film 3 having viscoelasticity by the probe 71, and the response state can be dynamically observed with high contrast and high magnification. In this case, if the film thickness distribution is measured, characteristics such as viscoelasticity of the sample thin film can be obtained.

  (2) In the primary imaging system 10, the angle θ 1 is set so that the light incident on the imaging lens 22 at the subsequent stage is not blocked by the lens barrel 27 and the reflectance of the light to the imaging lens 22 can be reduced. Is relatively large (for example, 20 degrees or more), and there is a restriction on the magnification M1 depending on the angle θ1. On the other hand, since the optical axis AX3 of the secondary imaging system 11 is arranged so as to be substantially perpendicular to the primary imaging plane P1, there is no restriction on magnification as in the primary imaging system 10, and the secondary imaging system The imaging system 11 can be set at a high magnification. Further, since the image pickup device 24 is disposed so that the image formation plane P2 of the secondary image formation system 11 substantially overlaps the detection surface 25, the image pickup device 24 provides an image with light contrast, high magnification, and more uniform luminance distribution. Can be imaged.

  (3) The magnification M1 of the primary imaging system 10 (that is, the objective lens 21) is set to a value that allows the angle θ1 to be 20 degrees or more when M1 = tan θo / tan θ1. Therefore, the angle θ1 can be set to a relatively large value of 20 degrees or more, and the reflectance of light incident from the primary imaging system 10 to the imaging lens 22 of the secondary imaging system 11 can be reduced. Therefore, a bright image can be formed on the detection surface 25 of the image sensor 24 by the secondary imaging system 11.

  (4) Especially when the magnification M1 of the primary imaging system 10 is set to a value in the range of 0.3 to 3 times, the connection between the optical axis AX1 of the primary imaging system 10 and the primary imaging system 10 is established. The angle θ1 formed with the image plane P1 can be set to a relatively large value. Therefore, the reflectance of light incident from the primary imaging system 10 to the imaging lens 22 of the secondary imaging system 11 can be effectively reduced.

  (5) The optical axis AX1 of the objective lens 21 in the primary imaging system 10 is twisted in a direction away from the sample surface SP with respect to the optical axis at the maximum reflection angle of the reflected light R1 with respect to the sample surface SP (object surface). It is arranged to be inclined by an angle Δθ. For this reason, since the angle θo formed by the optical axis AX1 of the primary imaging system 10 and the sample surface SP can be set large, the primary imaging system represented by M1 = tan θo / tan θ1 for a large angle θ1. The magnification M1 of 10 (that is, the objective lens 21) does not have to be so small.

(6) The primary imaging system 10 has one objective lens, and the secondary imaging system 11 has one imaging lens 22 made of an objective lens. Since the primary imaging system 10 and the secondary imaging system 11 are each provided with one objective lens in this way, the configuration of the imaging system 5 is simple even though the imaging system 5 is configured in multiple stages. Just do it.
(Second Embodiment)

  Next, a second embodiment will be described based on FIGS. This second embodiment is an example in which an afocal system is adopted as the imaging system of the ellipsometry microscope 1 in order to solve the problem of noise images due to background light. Note that only the imaging system of the ellipsometry microscope 1 is different from the first embodiment, and other configurations in the composite microscope 80 (such as the scanning probe microscope 70 and the oblique illumination system 4) are the same as those in the first embodiment. It is. For this reason, the imaging system of the ellipsometry microscope will be described below.

  As shown in FIG. 4, the imaging system 30 in the ellipsometry microscope 1 in the second embodiment has a primary imaging system 31 and a secondary imaging system 32. The primary imaging system 31 includes a pair of objective lenses 33 and 34, and the secondary imaging system 32 includes an objective lens 35 and an imaging lens 36 that form a pair. The set of objective lenses 33 and 34 is arranged so that the optical axes AX5 and AX6 coincide with each other and the focal planes of the objective lenses 33 and 34 coincide with each other. Further, the objective lens 35 and the imaging lens 36 forming a set are arranged so that the optical axes AX7 and AX8 coincide with each other and the focal planes of the objective lens 35 and the imaging lens 36 coincide with each other. In other words, the imaging system 30 is an afocal imaging system in which the focal planes of the pair of objective lenses 33 and 34 coincide and the focal planes of the objective lens 35 and the imaging lens 36 that form a pair coincide. It has become.

The lens barrel 37 of the objective lens 33 functions as a stop for the reflected light R1, and the reflected light R2 that has passed through the objective lens 33 is condensed to the focal plane FP1 of both lenses 33 and 34, and then diffused from the focal plane FP1. Then, the light enters the range in the lens barrel 38 of the objective lens 34. The reflected light R3 that has passed through the objective lens 34 becomes parallel light and forms a primary image of the object image on the primary imaging plane P1, and a lens barrel 39 of the objective lens 35 that constitutes the secondary imaging system 32. Incident in the range. The reflected light R4 that has passed through the objective lens 35 is condensed to the focal plane FP2 of both lenses 35 and 36, then diffused from the focal plane FP2 and incident on the imaging lens 36, and the reflected light that has passed through the imaging lens 36. The light R5 enters the analyzer 40 as parallel light. The parallel reflected light R6 that has passed through the analyzer 40 is incident on the detection surface 25 (secondary imaging surface P2) of the image sensor 24, and an object image is formed on the detection surface 25 as a secondary image.
Also in the second embodiment, the magnification M1 of the primary imaging system 31 is set smaller than the magnification M2 of the secondary imaging system 32 (M1 <M2).

  FIG. 5 is a schematic side view of the primary imaging system 31. As shown in FIG. 5, in this embodiment, the angle formed between the optical axis AX5 of the objective lens 33 and the sample surface SP is θo, and the angle formed between the optical axis AX6 of the objective lens 34 and the primary imaging plane P1. When θ1 is set, the relationship of the expression (1) shown in the first embodiment is established between the magnification M1 of the primary imaging system 31 and the angles θo and θ1. For this reason, also in the second embodiment, the angles θo and θ1 are both set to 45 degrees only when at least one lens constituting the primary imaging system 31 becomes a set of objective lenses 33 and 34. Has been. The magnification M1 of the primary imaging system 31 is set to 1. As an example, the objective lenses 33 and 34 are both objective lenses having a magnification of 1 ×. Also in the present embodiment, the angle θo is twisted to the angle (that is, the reflection angle θref) formed by the optical axis AX2 of the reflected light R1 and the sample surface SP at the assumed minimum reflection angle (= 60 degrees). It is set as a value obtained by adding the angle Δθ. Therefore, also in the present embodiment, the reflected light R3 that is parallel light that has passed through the primary imaging system 31 can be incident on the objective lens 35 at a relatively small incident angle (for example, about 60 °). .

  By setting the angles θo and θ1 and the magnification M1 to such conditions, the primary imaging plane P1 is formed in the space between the objective lens 34 and the objective lens 35 as shown in FIGS. Is done. As shown in FIGS. 4 and 5, the objective lens 35 and the imaging lens 36 constituting the secondary imaging system 32 have their optical axes AX7 and AX8 perpendicular to the primary imaging plane P1. It is arranged to be. The image sensor 24 is arranged such that the center axis AX4 of the detection surface 25 coincides with each of the optical axes AX7 and AX8, and the detection surface 25 overlaps with the secondary imaging plane P2. Yes.

  By the way, in the ellipsometry microscope 1, the intensity of the regular reflection light from the substrate 2 out of the reflection light from the sample S is stronger than the scattered light from the thin film 3. The light from the microstructure of the thin film 3 to be detected is this scattered light. For this reason, the image sensor 24 detects an image in which the image of the thin film 3 having a microstructure and the image formed by the specularly reflected light are superimposed. The specularly reflected light does not include information regarding the minute film thickness structure of the sample surface SP, and an unnecessary light intensity distribution corresponding to the intensity distribution of the light source 12 is generated. This becomes image noise due to background light.

  According to the present embodiment, in addition to the same effects as those of the first embodiment, the following effects can be obtained. By adopting the afocal imaging system 30, the specularly reflected light from the substrate 2 serving as background light enters the detection surface 25 of the image sensor 24 as parallel light and is reflected from the fine structure of the thin film 3. Enters and images as convergent light having various angles. The intensity distribution image of the light source 12 by the specularly reflected light from the sample surface SP is equivalent to imaging at infinity, and the luminance distribution can be made more uniform. Thereby, the problem regarding the noise image by background light can be solved.

  Further, the imaging system 30 has an object (sample S) and a primary object image (image on the primary imaging plane P1) to be imaged in the primary imaging system 31 and the secondary imaging system 32. , It can be arranged closest to the respective objective lenses 33, 35. That is, the arrangement can collect light scattered from the object most efficiently. In the present ellipsometry microscope 1 in which the angle formed by the scattered light with respect to the optical axis from the object to be imaged is large, it is also effective for securing a sufficient amount of light.

As described above, with respect to the thin film 3 on the substrate 2, it is possible to ensure a work space for other measurement or operation means and a high in-plane resolution, and to suppress a noise image due to background light. it can.
In addition, you may change embodiment as follows.

  In the above embodiment, an example in which the angles θo and θ1 are set to θo = θ1 is shown, but the minimum relationship between the angles θo and θ1 may be set as appropriate. Although θo ≧ θ1 is preferable, for example, θo <θ1 may be set.

  In the embodiment, a configuration in which the twist angle Δθ is not added to the objective lens constituting the primary imaging system can also be adopted. That is, the objective lens may be arranged so that the optical axis of the objective lens coincides with the optical axis of the reflected light R1.

  In the embodiment, the ellipsometry microscope 1 is not limited to configuring a composite microscope in combination with a scanning probe microscope. For example, a configuration in which the sample S is combined with an operation means such as a sliding probe for applying a dynamic stimulus to the sample S may be used. According to the ellipsometry microscope having this configuration, it is possible to dynamically observe a response state when a mechanical stimulus is applied to a thin film having viscoelasticity with high contrast and high magnification. Further, the measuring means and the scanning means do not necessarily need to contact the sample, and may be used close to the sample. As this kind of operation means, a thermal spray is applied to a sample thin film (solid thin film or liquid thin film), a nozzle for spraying a fluid (for example, gas such as air, or liquid such as acid or alkali) to a sample thin film (for example, liquid thin film). Examples thereof include a light heating means and a heater.

In the embodiment, at least one of the primary imaging system and the secondary imaging system may be configured by a plurality of stages of imaging systems. That is, at least one of the primary imaging system and the secondary imaging system can be configured by arranging a plurality of imaging systems having at least one lens. For example, in the case of a secondary imaging system, the number of imaging planes is the same as the number of stages, and the final imaging plane is a secondary imaging plane so that the detection plane of the image sensor coincides with the secondary imaging plane. What is necessary is just to arrange | position an image pick-up element. In addition, it is preferable that the optical axes of the lenses of the multistage imaging system constituting the secondary imaging system are arranged perpendicular to the primary imaging plane.
The primary imaging system and the secondary imaging system are not limited to one or two lenses, and may include a plurality of three or more lenses.
-You may provide the stop which restrict | squeezes the light beam of illumination light. The contrast can be improved by reducing the diameter of the light beam depending on the object.

  The phase compensator 16 may be a quartz photoelastic modulator instead of the λ / 4 plate. As a phase modulation type, the phase compensator can be modulated at high speed. Processing in combination with a CCD camera can be performed at high speed.

  -Both the oblique illumination system and the imaging system are explained with schematic diagrams, and it goes without saying that an optical system equivalent to this can be obtained. Further, it goes without saying that the configuration can be added, omitted, or replaced by those skilled in the art.

The ellipsometry apparatus of the present invention can be applied not only to an ellipsometry microscope having a function of observing a sample in an enlarged manner, but also to an ellipsometer that performs film thickness distribution measurement. For ellipsometry equipment, for example, in industrial applications, film thickness distribution measurement of thin films such as lubricating films on disk surfaces, liquid thin films in nanoimprint lithography, and liquid molecular thin films in polymer electronics, ellipsometry is used. Also included are thin film inspection devices that are used.
Hereinafter, the technical idea grasped from the respective embodiments and modifications will be described below.

  (1) The primary imaging system has one objective lens as the lens, and the secondary imaging system has one objective lens as the lens. The ellipsometry apparatus according to any one of the above. According to this configuration, since one objective lens is provided for each of the primary imaging system and the secondary imaging system, the configuration of the imaging system can be simplified even though the imaging system is divided into a plurality of stages. .

  (2) The primary imaging system and the secondary imaging system each include at least one set of lenses, and the at least one set of lenses is an afocal system having a configuration in which focal planes coincide with each other. The ellipsometry apparatus according to any one of claims 1 to 6. According to this configuration, since the primary imaging system and the secondary imaging system are afocal systems, the background light regularly reflected by the part other than the observation target in the object enters the detection surface of the image sensor as parallel light. The reflected light from the object is incident and imaged as convergent light having various angles. The intensity distribution image by the regular reflection light from the object plane is equivalent to imaging at infinity, and the luminance distribution can be made more uniform. Thereby, the noise image by background light can be reduced.

  (3) The ellipsometry apparatus according to any one of claims 1 to 6, wherein the second magnification is 10 times or more and 10 times or more of the first magnification. According to this configuration, even when the first magnification is low, the object image can be observed at high magnification by the ellipsometry apparatus.

  (4) The operation unit according to any one of claims 1 to 6, further comprising an operation unit capable of performing an operation of contacting the object surface at a position on a normal direction observation side with respect to the object surface. The ellipsometry apparatus described. According to this configuration, the oblique illumination system and the imaging system are arranged at the position on the incident source side of the illumination light with respect to the object plane and the position on the reflection destination side of the reflected light, respectively, and the normal direction observation side with respect to the object plane The space created at the position can be used as a work space for the operation means. For example, it is possible to perform dynamic observation of the object surface while performing an operation of bringing the operating means into contact with the object.

  (5) An ellipsometry microscope as the ellipsometry apparatus according to any one of claims 1 to 6, and a probe capable of contacting the object plane at a position on the normal direction observation side with respect to the object plane A combined microscope equipped with a scanning probe microscope. According to this composite microscope, an object can be observed at a high magnification in a wide field of view with an ellipsometry microscope, and a point of interest where a fine structure is particularly desired can be observed at a higher magnification with a scanning probe microscope.

  DESCRIPTION OF SYMBOLS 1 ... Ellipsometry microscope as an ellipsometry apparatus, 2 ... Board | substrate, 3 ... Thin film, 4 ... Oblique illumination system, 5 ... Imaging system, 10 ... Primary imaging system, 11 ... Secondary imaging system, 12 ... Light source DESCRIPTION OF SYMBOLS 13 ... Optical fiber, 14 ... Collimating lens, 15 ... Polarizer, 16 ... Phase compensator ((lambda) / 4 plate), 17 ... Collimating lens, 21 ... Objective lens which comprises the lens of a primary imaging system, 22 ... Imaging lens constituting a secondary imaging system lens, 23... Analyzer, 24... Image sensor, 25... Detection surface, 26. Image system, 31... Primary imaging system, 32... Secondary imaging system, 33, 34... Objective lens constituting the primary imaging system lens, 35... Objective lens constituting the secondary imaging system lens 36... Imaging lenses constituting secondary imaging system lenses, 40... Analyzer, 70. Inspection probe microscope, 71 ... probe, 72 ... displacement system, 80 ... composite microscope, M1 ... magnification as first magnification, M2 ... magnification as second magnification, S ... sample as object, SP ... object As sample surfaces, L1 to L4... Illumination light, R1 to R3... Reflected light (first embodiment), R1 to R5... Reflected light (second embodiment), P1. Primary imaging plane, P2 ... secondary imaging plane as the imaging plane of the secondary imaging system, θo ... angle, θ1 ... angle, θref ... reflection angle, θrefmin ... minimum reflection angle, Δθ ... twist angle, AX1, AX3, AX5, AX6, AX7, AX8: optical axis of lens, AX2: optical axis of reflected light, AX4: central axis of image sensor, FP1, FP2: focal plane.

Claims (6)

An ellipsometry apparatus capable of magnifying and observing an image of an object to be observed using ellipsometry,
A slant illumination system having a polarizer and a phase compensator on an optical path of a light source, and obliquely illuminating the object with parallel light passing through the polarizer and the phase compensator;
An imaging system for enlarging an object image by incident reflected light from the object;
An analyzer provided in the middle of the optical path of the reflected light in the imaging system;
An image pickup device for picking up an image formed by the image forming system,
The imaging system is
A primary imaging system that includes at least one lens that receives reflected light from the object and forms an object image at a first magnification;
A secondary imaging system including at least one lens for enlarging an object image formed by the primary imaging system at a second magnification larger than the first magnification;
An ellipsometry apparatus characterized by comprising: The ellipsometry apparatus according to claim 1,
The optical axis of the secondary imaging system is arranged so as to be substantially perpendicular to the imaging surface of the primary imaging system, and the imaging surface of the secondary imaging system is connected to the detection surface of the image sensor. An ellipsometry apparatus in which the imaging elements are arranged so as to substantially overlap. The ellipsometry apparatus according to claim 1 or 2,
When the angle θo formed between the optical axis of the primary imaging system and the object plane and the angle θ1 formed between the optical axis and the imaging plane of the primary imaging system,
An ellipsometry apparatus characterized in that the magnification M1 of the primary imaging system is set to a value that allows the angle θ1 to be 20 degrees or more when M1 = tan θo / tan θ1. The ellipsometry apparatus according to any one of claims 1 to 3,
An ellipsometry apparatus characterized in that the magnification M1 of the primary imaging system is set to a value within a range of 0.3 to 3 times. The ellipsometry apparatus according to claim 3 or 4,
The angle θo formed by the optical axis of the primary imaging system and the object plane and the angle θ1 formed by the optical axis and the imaging plane of the primary imaging system satisfy θo ≧ θ1, and M1 = tan θo / An ellipsometry apparatus characterized in that the magnification M1 of the primary imaging system determined by tan θ1 is set to 1 or more. The ellipsometry apparatus according to any one of claims 1 to 5,
It is a configuration in which observation or film thickness distribution measurement is performed by irradiating the object with illumination light at an incident angle such that the reflectance of the object with respect to p-polarized light is substantially minimum
The optical axis of the primary imaging system is tilted by a twist angle Δθ in a direction away from the object plane with respect to the optical axis when the optical axis of the reflected light from the object plane takes the assumed minimum reflection angle. An ellipsometry device characterized by being arranged.

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