JPH0772013A - Ellipsometer - Google Patents

Abstract

PURPOSE:To make it possible to simultaneously measure plural positions of a sample by arranging a beam expander to make light incident on the surface of the sample turn into thick parallel light while an image sensor comprising a plurality of photodetecting members is used as detector. CONSTITUTION:A beam expander 16 which is adapted to make light made incident on a sample 13 turn into thick parallel light in an optical path immediately before light from a light source 11 enters the sample 13 and an image sensor 15 is used as detector for detecting the reflected light from the sample 13. Moreover, a rotation holding mechanism for holding the sensor 15 is provided so as to keep the surface of the sample 13 parallel with a photodetecting surface of the sensor 15 regardless of the incident angle of the light on the surface of the sample 13 to prevent the deformation of the sample 13 developed free from changes in the angle of incidence at which the light emitted from the expander 16 enters the sample 13. This makes simultaneously measure the sample 13 at a plurality of measuring points and dispenses with correction processing in the image display, thereby allowing the lowering of costs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is based on a change in the polarization state of light emitted from the surface of the substrate and the inside of the substrate to determine the physical constants such as optical constants, film thickness and birefringence of the film attached to the substrate or the surface of the substrate. An ellipsometer for measuring quantity.

[0002]

2. Description of the Related Art In polarization analysis, measurement light is incident on the surface of a sample, and Δ indicating the phase difference due to the physical properties of the sample from the change in the polarization state of the emitted light and Ψ indicating the amplitude reflectance ratio. Then, the refractive index, the absorptivity, the birefringence and the film thickness of the sample or the film attached to the sample surface are identified from these values.

The rotation analyzer method is generally used as a method for obtaining the above Δ and Ψ at high speed, and an optical system for realizing the rotation analyzer method is shown in FIG.

The illustrated optical system includes a light source 81 and a polarizer 8.
2, the analyzer 84 and the detector 85, the light emitted from the light source 81 passes through the polarizer 82,
After being reflected by the sample 83, it passes through the analyzer 84 and enters the detector 85 (P-S-A).
system).

At the time of measuring Δ and Ψ, the polarizer 82 is set in a predetermined direction and linearly polarized light is incident on the sample, and the analyzer 8
From the change in the output intensity of the detector 85 when 4 is rotated, a Fourier coefficient in which Δ and Ψ are represented as a function of variables is obtained, and this is solved to calculate Δ and Ψ.

Another optical system of the rotation analyzer method is shown in FIG.
, An optical phase plate (λ / 4 plate) 91 is provided between the polarizer 81 and the sample 83, and the polarizer 82 and the optical phase plate 9 are provided.
1 is set to a predetermined azimuth and the light incident on the sample 83 is circularly polarized light or elliptically polarized light, and Δ, Ψ from the output intensity change of the detector 85 when the analyzer 84 or the phaser 91 is rotated. To obtain a Fourier coefficient expressed as having a variable and calculate Δ and Ψ (P-C-S-A system) or an optical phase plate 91 on the outgoing light side as shown in FIG. Some are provided (P-S-C-A system).

A sample table (not shown) on which the sample 83 is placed is constructed so as to be movable in parallel with the sample surface. In actual measurement using the above-mentioned optical systems, the sample is measured at a desired measurement point of the sample. Light is emitted. When measuring a plurality of points on the sample, the sample stage is moved to sequentially perform the measurement at each measurement point.

[0008]

The above-described conventional ellipsometer has a structure in which, when a plurality of measurement points are present on the same sample, the measurement at each measurement point is sequentially performed. In the case of measuring the thickness of the film, there is a problem that the film thickness changes during the movement of the measurement point, which makes the measurement meaningless.

The present invention has been made in view of the problems of the above-described conventional technique, and an object of the present invention is to realize an ellipsometer capable of simultaneously measuring a plurality of points of a sample.

[0010]

The ellipsometer of the present invention is characterized in that light is incident on the surface of a sample, and the refractive index, absorptivity, and birefringence of the film adhered to the sample or the sample surface are determined by the change in the polarization state of the emitted light. In an ellipsometer consisting of an arithmetic processing system for measuring the film thickness and the like, a beam expander is provided to make the light incident on the sample surface into a thick parallel light, and to detect changes in the polarization state of the emitted light. An image sensor including a plurality of light receiving members is used as a detector.

In this case, a rotation holding mechanism for holding the image sensor may be provided so that the surface of the sample and the light receiving surface of the image sensor are kept parallel to each other regardless of the angle of incidence of light on the surface of the sample.

Further, among the light receiving members constituting the image sensor, the one used for measurement may be determined according to the angle at which the light is incident on the sample surface.

Further, an optical system for injecting light on the sample surface and detecting a change in the polarization state of the emitted light, and a refractive index, an absorptivity, and a complex index of a film attached to the sample or the sample surface based on the change in the polarization state. In an ellipsometer composed of an arithmetic processing system for measuring refractivity and film thickness, etc., the optical system is provided with a beam expander for making the light incident on the sample into thick parallel light, and the polarization state of the outgoing light An image sensor including a plurality of light receiving members is used as a detector for detecting a change, and the arithmetic processing system includes a plurality of digital converters for converting an input signal into a digital value and the image sensors sequentially outputting the digital signals. An output signal of the light receiving member is input, and a signal output from a predetermined light receiving member is sequentially switched to a specific digital converter of the plurality of digital converters and output. A changeover switch, the refractive index of the film deposited on the sample or specimen surface for each output of said plurality of digital converter, absorption rate, and a calculation processing unit for calculating the birefringence and the film thickness and the like are provided that.

[0014]

[Function] The light irradiating the sample surface is thick parallel light,
Since the image sensor is used as the detector that detects the reflected light, it is possible to perform measurement at a plurality of measurement points within the same time.

When a plurality of digital converters and changeover switches are provided, one digital converter can be used for each measuring point, and therefore, at the same measurement time as that for measuring one measuring point. The measurement is made.

Further, the distribution of the film thickness and the refractive index can be measured without moving the sample.

In the case where the rotation holding mechanism is provided, the shape of the light on the sample surface and the shape of the light on the light receiving surface of the image sensor are the same regardless of the angle at which the light is incident on the sample surface. It is not necessary to perform correction processing when displaying an image using the detection result of each light receiving member.
The same applies to the case where the light receiving member used for measurement is determined according to the angle at which light is incident on the sample surface.

[0018]

Embodiments of the present invention will now be described with reference to the drawings.

FIGS. 1 to 3 respectively correspond to FIGS.
(P-S-A system), (P-C) similar to the conventional example shown in FIG.
It is a figure which shows the structure of the Example which used the structure of this invention for the optical system of -S-A system) and (P-S-C-A system).

Light source 11, polarizer 12 and sample 1 in each figure
3, the analyzer 14 and the optical phase plate 21 are the same as the light source 81, the polarizer 82, the sample 83, the analyzer 84, and the optical phase plate 91 in FIGS. 8 to 9, respectively. In each of the embodiments shown in FIG. 1, a beam expander 16 for making the incident light on the sample 13 into a thick parallel light is provided in the optical path immediately before entering the sample 13, and the sample 1
The image sensor 15 is used as a detector that receives the light emitted from the light source 3.

FIG. 4 is a block diagram showing the arrangement of an arithmetic processing system for obtaining the values of Δ and Ψ from the measured light intensities detected by the above optical systems.

This arithmetic processing system is composed of a changeover switch 31, a digital conversion processing section 32 composed of digital converters 32 ₁ , 32 ₂ , ..., 32 _n , an arithmetic processing section 33 and a display section 34. Has been done.

The operation of reading the signals from the respective light receiving members of the image sensor 15, the operation of switching the changeover switch, and the converting operation of each of the digital converters 32 _{1 to} 32 _n are controlled by a controller (not shown). In addition to this, the control device also rotates the analyzer 14 shown in FIGS. 1 to 3 (the polarizer 12 and the optical phase plate 21 are rotated if necessary).
The output value of the image sensor 15 is digitally converted every time the analyzer 14 is rotated by a predetermined angle.

The light receiving signals sequentially read from the plurality of light receiving members forming the image sensor 15 are changeover switches 31.
Entered in. The changeover switch 31 selects the signals from the light receiving members provided at a plurality of target measurement points and selects the digital converter 3 in the digital conversion processing unit 32.
2 _{1 to} 32 _n are sequentially switched and output. Each of the digital converters 32 _{1 to} 32 _n includes a sample hold circuit and an A / D converter, and the above-mentioned multi-bit signal is converted into a digital signal by each of the digital converters 32 _{1 to} 32 _n . And is output to the arithmetic processing unit 33.
The arithmetic processing unit 33 obtains the values of Δ and Ψ at each measurement point from the change in light intensity indicated by the input value, generates a display signal for displaying the values, and outputs the display signal to the display unit 34. Display unit 34
Then, the display operation is performed according to the display signal, and the measurement result is displayed to the measurer.

In the operation of selecting the light-receiving member of the image sensor 15 corresponding to the measurement point, the control means changes the switch 31 in accordance with the reading timing of the image sensor 15 according to the operator's input to the input means (not shown). Is done by switching.

It is of course possible to select arbitrarily distant points as the measurement points, but as shown by the shaded area in FIG. 5, by collectively selecting the light receiving members 51 in a predetermined area,
It is also possible to reduce measurement error and improve measurement accuracy.

By using the optical system and the arithmetic processing system as described above, it is possible to measure a plurality of measurement points at the same time, and it is possible to obtain Δ and Ψ at the same time. When the film thickness is identified using Δ and Ψ, it is possible to confirm the shape of the sample surface at the same time.

In the configuration of the optical system of the present invention, since the beam expander 16 is inserted, the arithmetic processing unit 33 considers the error (depending on the configuration of the beam expander) caused by inserting the beam expander 16. Then, Δ and Ψ are calculated.

Further, in any of the optical systems shown in FIGS. 1 to 3, the shape of the light with which the sample 13 is irradiated depends on the shape of the light emitted from the beam expander 16 and the light receiving surface of the image sensor 15. The shape will be different. The shape of the light emitted from the beam expander 16 is shown in FIG.
Assuming that the sample 13 has a circular shape, the shape of the irradiation light on the sample 13 becomes an elliptical shape extending along the traveling direction of the light, as shown in FIG. 6B. The elliptical shape in this case is
The light emitted from the beam expander 16 at the time of measurement varies depending on the angle of incidence on the sample 13 (incident angle). Therefore, when the incident angle is changed, the light reflected at the same location on the sample 13 is received by the light receiving member 51 (see FIG. 5) provided at a different location. When the display is performed in this state, the measurer may erroneously recognize each measurement point of the sample 13, so that the measurement result shown in FIG.
The arithmetic processing unit 33 shown in FIG. 3 includes position correction data for each incident angle, and when the incident angle is changed,
The light receiving member 51 (and the digital converter output) is selected according to the incident angle, and deformation of the sample 13 displayed on the display unit 34 is prevented.

When the above-described correction is performed, the amount of correction data for each incident angle becomes large, and the manufacturing cost of the device may increase.

In FIG. 7, without using the position correction data,
FIG. 7 is a diagram showing an optical system for preventing a measurer from erroneously recognizing each measurement point of the sample 13.

The image sensor 15 in FIG. 7 is arranged so that its light receiving surface 71 is parallel to the measurement surface of the sample 13. When the incident angle is changed, the image sensor 15 also moves (rotates) along with other optical elements such as the analyzer 14, but the image sensor 15 rotates in a rotation holding mechanism (not shown) opposite to the moving direction. Is provided to prevent the sample 13 displayed on the display unit 34 from being deformed regardless of the change of the incident angle.

In each of the above-mentioned embodiments, a plurality of digital converters are provided and the signal from the image sensor is switched by the changeover switch. This is because the measurement time is the same as the conventional one. Of course, the configuration may be such that the signals from the light receiving members placed at the measurement points are sequentially input to one digital converter and converted. In this case, although the measurement time becomes long, there is an advantage that the cost for the arithmetic processing system becomes almost the same as the conventional one.

Further, a plurality of measuring points are simultaneously irradiated with light,
Further, although the beam expander and the image sensor are used as the structure for receiving the measurement light, the cylindrical lens that causes the converging action only on one plane is used as the light irradiating means, and the line sensor is used as the light receiving means. The sample stage may be moved in a direction perpendicular to the convergent light by the cylindrical lens.
In this case, it is necessary to move the sample stage, but the intensity of generated light required for the light source can be weakened because the light irradiated on the sample is converged.

Further, a lens may be provided immediately before the image sensor. Since the diameter of the light incident on the image sensor can be adjusted by providing the lens, it is possible to prevent the size of the image sensor used from being limited. In particular, by using a lens having a magnifying effect and using a large-area image sensor, it is possible to magnify a minute area of the sample and perform polarization analysis.

In the above-mentioned embodiments, the description has been made assuming that Δ and Ψ are obtained by the rotation analyzer method. However, in the measurement method, the optical phase plate and the analyzer, or the polarizer and the analyzer are alternately rotated in addition to this. From the rotation angle when the light is extinguished by
There are an extinction method for obtaining Ψ, a rotating phaser method in which an analyzer is fixed and an optical phase plate is rotated, and the like.

The present invention is naturally applicable to the rotary retarder method and also applicable to the extinction method.

In the quenching method, for example, as shown in FIG.
-C-S-A) optical system is used, the optical phase plate 21 is fixed to a predetermined azimuth angle, and then the azimuth angle of the polarizer 12 is adjusted so that the reflected light of the sample 13 becomes linearly polarized light. Adjust. As a result, the angle of the analyzer 14 can be adjusted to extinguish the light. Polarizer 12 and analyzer 1 at the time of extinction
Δ and Ψ are obtained from the azimuth angle of 4. The extinction state can be detected by the image sensor 15, and the polarizer is in a stopped state when the analyzer is rotated to search for the extinction point. Therefore, by detecting the rotation angle of the analyzer when the light detection intensity of each light receiving member of the image sensor 15 becomes the minimum, Δ and Ψ at a plurality of measurement points can be simultaneously measured as in the rotation analyzer method. You can

Furthermore, in recent years, in addition to the above-described rotation analyzer method, rotation phaser method, and extinction method, a polarization analysis method using a PEM (Photo Elastic Modulator) modulator that produces birefringence when a force is applied is available. Proposed. Also in this case, the configuration of the present invention can be applied.

The range of measurement points that can be set is limited by the effective area of the analyzer and the light receiving area of the image sensor in addition to the capability of the beam expander. Of course, the moving mechanism of the sample stage may be used together.

[0041]

Since the present invention is constructed as described above, it has the following effects.

According to the first aspect of the invention, there is an effect that the measurement at a plurality of measurement points can be performed simultaneously.

According to the second aspect of the present invention, there is an effect that a correction process is unnecessary when an image is displayed by using the detection result of each light receiving member, and the cost can be prevented from increasing.

According to the third aspect, there is an effect that it is possible to prevent the deformation due to the incident angle from occurring in the image display using the detection result of each light receiving member.

According to the fourth aspect of the invention, since the measurement is performed in substantially the same measurement time as that for measuring one measurement point, there is an effect that the measurement time can be shortened in addition to the above effect. .

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an optical system according to an example of the present invention.

FIG. 3 is a diagram showing a configuration of an optical system according to an example of the present invention.

FIG. 4 is a diagram showing a configuration of an arithmetic processing system according to an embodiment of the present invention.

FIG. 5 is a diagram showing an example of setting measurement points when performing measurement using the embodiment of the present invention.

6A and 6B are diagrams showing the shape of light emitted from the beam expander 16 and the shape of irradiation light on the sample 13. FIG.

FIG. 7 is a diagram showing a configuration of an optical system according to another embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a conventional optical system.

FIG. 9 is a diagram showing a configuration of an optical system of a conventional example.

FIG. 10 is a diagram showing a configuration of an optical system of a conventional example.

[Explanation of symbols]

11 light source 12 polarizer 13 sample 14 analyzer 15 image sensor 16 beam expander 21 optical phase plate 31 changeover switch 32 digital conversion processing unit 32 _{1 to} 32 ₃ digital converter 33 arithmetic processing unit 34 display unit 51 light receiving member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chitomi Tomita 5-4-1, Dobashi, Miyamae-ku, Kawasaki-shi, Kanagawa Photo Device Co., Ltd.

Claims (4)

[Claims] 1. An arithmetic processing system in which light is incident on a sample surface and the refractive index, absorptivity, birefringence, film thickness, etc. of the sample or a film attached to the sample surface are measured from changes in the polarization state of the emitted light. In the ellipsometer, the beam expander is provided to convert the light incident on the sample surface into thick parallel light, and an image composed of multiple light-receiving members is used as a detector to detect changes in the polarization state of the emitted light. An ellipsometer characterized in that a sensor is used. 2. The ellipsometer according to claim 1, wherein the rotation holding mechanism holds the image sensor so that the surface of the sample and the light receiving surface of the image sensor remain parallel to each other regardless of the angle at which the light is incident on the surface of the sample. An ellipsometer characterized by having. 3. The ellipsometer according to claim 1, wherein among the light receiving members constituting the image sensor, one used for measurement is determined according to an angle at which light is incident on the sample surface. . 4. An optical system in which light is incident on a sample surface and a change in the polarization state of the emitted light is detected, and a refractive index, an absorptivity, and a complex index of a film attached to the sample or the sample surface based on the change in the polarization state. In an ellipsometer consisting of an arithmetic processing system that measures refractivity, film thickness, etc., the optical system is equipped with a beam expander for making the light incident on the sample into thick parallel light and An image sensor consisting of a plurality of light receiving members is used as a detector for detecting changes, and the arithmetic processing system has a plurality of digital converters for converting an input signal into a digital value and each output from the image sensor in sequence. The output signal of the light receiving member is input, and the signal output from the predetermined light receiving member is sequentially switched and output to a specific digital converter among the plurality of digital converters. A changeover switch and an arithmetic processing unit for calculating the refractive index, absorptivity, birefringence, film thickness, etc. of the sample or a film attached to the sample surface for each output of the plurality of digital converters are provided. Characteristic ellipsometer.