JPH02237012A - Aligner - Google Patents

Abstract

PURPOSE:To contrive improvement in the utilization efficiency of a laser beam by a method wherein a photo-extraction part, with which the laser beam which is made incident on the circumference of the photo-transmitting section of a luminous flux shaping member is guided to a light-detector, is formed in the vicinity of the photo-transmitting part, and the unnecessary light which is not transmitted to the substrate to be exposed is guided to the light detector. CONSTITUTION:The title aligner is constituted in such a manner that the laser beam, which is extracted from the pinhole 29 formed on the circumference of the circular aperture 23A of a luminous flux shaping member 23 used to shape up the cross-sectional shape of the laser beam, is detected by a line sensor 27. As a result, the efficiency of utilization of the laser beam used for exposure of wafer can be enhanced, and also the exposure time when the wafer is exposed can be reduced. Also, as the light flux diameter, spreading angle and the like can always be monitored by a laser beam flux monitoring device 31, the change in luminous flux diameter and the spreading angle of the laser beam made incident on the optical system of illumination are detected, and necessary correction can be conducted automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an exposure apparatus, and more particularly to an exposure apparatus that uses a laser such as an excimer laser as an exposure light source. [Prior Art] In recent years, as integrated circuits such as LSIs have become highly integrated, exposure apparatuses that can accurately form fine patterns of 1 μm or less on wafers have been used.

Furthermore, in order to further refine the resolution line width of the equipment, there is active development of exposure equipment equipped with an excimer laser that emits high-intensity light in the far ultraviolet region as an exposure light source. In this type of exposure equipment, after shaping the cross-sectional shape of the laser beam, a beam splitter is installed obliquely in the optical path of the laser beam in order to control the exposure amount to the exposed substrate or correct positional deviation of the laser beam. However, a portion of the laser light may be guided to a photodetector via this beam splitter. However, guiding the laser light to the photodetector in this manner is undesirable because it reduces the utilization efficiency of the laser light used for exposure. Summary of the Invention The present invention has been made in view of the above-mentioned problems, and it is possible to guide a part of the laser beam to a photodetector without obliquely installing a beam splitter or the like in the optical path of the laser beam. The purpose is to provide a possible exposure device. In order to achieve this object, the exposure apparatus of the present invention includes a beam shaping member including a light transmitting section of a predetermined shape that shapes the cross-sectional shape of laser light, and a beam shaping member that controls the laser beam from the light transmitting section of the beam shaping member. It has an optical system directed toward the substrate to be exposed, and a light extraction section formed near the light transmission section of the light beam shaping member to guide laser light incident around the light transmission section to a photodetector. It is characterized by being configured so that unnecessary light that is not transmitted to the exposed substrate via the light transmission section of the light beam shaping member is guided to the photodetector. On the other hand, it is possible to improve the utilization efficiency of laser light, and it is possible to shorten the exposure time when exposing a substrate to be exposed such as a wafer.

The specific form and further features of the exposure apparatus of the present invention are described in the Examples described below. (Embodiment) FIG. 1 is an overall configuration diagram showing an embodiment of the exposure apparatus of the present invention. A indicates the main body of the exposure apparatus. 1 is the wavelength λw24
It is a KrF excimer laser that emits a laser beam of 8.4 nm, and is fixed on an XYθ stage 2 installed on a laser constant plate 3 on a vibration-proof cushion 4. B is a transmission optical system that transmits the laser beam 2o from the laser 1 to the optical system of the exposure apparatus main body 1, and the mirror 5 shown in the figure
It is composed of multiple optical components including. Details of this transmission optical system will be described later. 6 is an illumination optical system, 9 is a reticle on which a circuit pattern for semiconductor manufacturing is drawn, 90 is a reticle holder, 1o is a projection lens for projecting the circuit pattern of the reticle 9, 11 is a lens support, and 12 is a wafer (
13 is a chuck for suctioning and fixing the wafer 12, 14 is an XY stage, 15 is a stepper fixed plate, 16
is an anti-vibration cushion. Laser light 20 emitted from excimer laser 1 passes through transmission system optics B and enters illumination optical system 6 of exposure apparatus main body A.

After the beam diameter is expanded by the illumination optical system 6, the beam passes through the reticle 9 and the projection lens 10, and then reaches the wafer 12. An exposure optical system consisting of an illumination optical system 6 and a projection lens 1o is mounted on a lens support stand 1 fixed to a stepper fixed plate 15.
1, the relative positions of each optical system within the exposure apparatus main body A remain substantially unchanged. A circuit pattern is drawn on the reticle 9 as described above, and by illuminating the circuit pattern with laser light, the pattern reduced to 1/5 is transferred onto the wafer 12 by the projection lens 10.

The wafer l2 is vacuum-adsorbed onto a wafer chuck 13, and the wafer chuck 13 is fixed on a movable XY stage 4 provided on a stage plate 15. The wafer 12 can be transported by the NY stage 14 in two mutually orthogonal directions, X and Y, and the reduced pattern can be transferred to any position on the wafer.

Normally, several dozen shots of a reduced pattern are transferred onto the wafer 12, so by moving the XY stage 14 stepwise in the X or Y direction, laser light is irradiated onto each shot through the reticle 9 and the projection lens 10. Then, the process of transferring the pattern to each shot is repeated. Reference numeral 17 denotes an illuminance meter consisting of a photodetector fixed on the XY stage 14. By driving the XY stage 14, it is positioned on the image plane of the projection lens 10 and measures the illuminance on the image plane of the projection lens 10. Measure. This illumination meter 1
The illuminance measured in step 7 is regarded as the illuminance on the surface of the wafer 12, and is used as control data for controlling the exposure amount during exposure.

FIG. 2 is an enlarged view showing the specific configuration of the transmission optical system shown in FIG. 1, and depicts the characteristic configuration of the present exposure apparatus. Further, in FIG. 2, the same members as those depicted in FIG. 1 are designated by the same reference numerals as in FIG. 21
is a concave lens, and 22 is a convex lens. Lenses 21 and 22 constitute an anamorphic beam expander system. 23
is a light beam shaping member having a circular aperture (light transmission part);
As shown in the figure, two pinholes 29 are formed at predetermined positions around the light transmission section 23A of the light beam shaping member 23. Reference numeral 24 denotes an image rotation prism that receives laser light having a circular cross-sectional shape after passing through the circular opening 23A of the beam shaping member 23, and is rotatable about the optical axis of the transmission optical system B by a rotation mechanism (not shown). (see arrow W). A small reflecting mirror 25 receives the laser beam that has passed through the pinhole 29 of the beam shaping member 29 via the image rotation prism 24, and reflects the laser beam from the pinhole 29 toward the condenser lens 26. A condensing lens 26 condenses the laser beam reflected by the reflecting mirror 25 onto a line sensor 27.
A photoelectric conversion signal from the line sensor 27 is input to a laser beam monitor device 31 via a signal line 30. 28
is a beam expander system, which receives the laser beam that has passed through the circular aperture 23A of the beam shaping member 23 and the image rotation prism 24, expands the beam diameter of this laser beam, and then sends it to the illumination optical system 6 of the exposure apparatus main body A. Direct. The laser beam emitted from the excimer laser 1 is reflected by the reflecting mirror 5.
The beam is reflected by the beam and enters a beam expander system consisting of a concave lens 21 and a convex lens 22. The cross-sectional shape of the laser beam from the excimer laser 1 is determined depending on the shape of the discharge part of the laser, and usually has a rectangular shape. In this embodiment, in order to change the cross-sectional shape of the laser beam from a rectangle to a substantially square, the concave lens 2l and the convex lens 21 are each constructed of toric lenses, creating an anamorphic beam expander system. Therefore, this beam expander system (
The cross-sectional shape of the laser beam that has passed through 21.22) is approximately square. The laser beam from the beam expander system (21, 22) is reflected by the reflecting mirror 5, and the beam shaping member 23
is incident on . The diameter of the circular aperture 23A of the beam shaping member 23 is set smaller than the length of one side of the square cross section of the incident laser beam, and the center of the circular aperture 23A and the center of the laser beam are on the optical axis of the transmission optical system B. To position. Therefore, the circular aperture 23A of the beam shaping member 23 converts the cross-sectional shape of the laser beam into a circular shape, and moreover, a portion near the center of the laser beam where the power density is relatively uniform is extracted.

On the other hand, a portion of the laser light that enters around the circular opening 23A of the beam shaping member 23 and is blocked by the beam shaping member 23 passes through the two pinholes 29. Luminous flux shaping member 23
The laser beam that has passed through the circular opening 23A and the two laser beams that have passed through the two pinholes 29 are incident on the image rotation prism 24, and the laser beam that has passed through the circular opening 23A is directed to the beam expander system 28 and pinned. hall 2
The two laser beams that have passed through 9 are directed toward a reflecting mirror 25. When the image rotation prism 24 is rotated by the aforementioned rotation mechanism, the laser beam that passed through the circular aperture 23A and the two laser beams that passed through the pinhole 29 are rotated, and the laser beam is emitted from the light exit side of the image rotation prism 24. When observed, the fourth
The shape will be as shown in the figure. In FIG. 4, 41 is a cross section of the laser beam that has passed through the circular aperture 23A of the beam shaping member 23, and 42 is the locus of the laser beam that has passed through the pinhole 29. When the image rotating prism 24 is rotated, the two laser beams that have passed through the pinholes 2 and 9 rotate while drawing a ring-shaped trajectory, as shown in FIG. Trajectory of light (light path)
It is installed at a predetermined position on the top so that two laser beams can be reflected at the same time. In order to match the trajectories of the two laser beams, in this embodiment, two laser beams are placed at positions that are the same distance apart from the center of the circular aperture 23A of the beam shaping member 23.
Two pinholes were formed.

In this embodiment, the rotatable image rotation prism is provided in the optical path of the laser beam in order to equalize the cross-sectional intensity distribution of the laser beam used for exposure that passes through the circular aperture 23A of the beam shaping member 23. ．． That is, the light beam shaping member 23
By extracting the light near the center of the laser beam emitted from the laser 1, a laser beam with relatively uniform power density can be obtained, but the cross-sectional intensity distribution of the laser beam is not completely uniform. In particular, since the laser beam emitted from the excimer laser 1 has an asymmetric intensity distribution with respect to the optical axis, it is necessary to make this intensity distribution at least symmetrical with respect to the optical axis. Therefore, the laser beam that has passed through the circular aperture 23A of the beam shaping member 23 is incident on the image rotation prism 24, and the image rotation prism 24 is rotated about the optical axis to rotate the laser beam around the optical axis. It forms a laser beam that is symmetrical about the optical axis and has a nearly uniform cross-sectional intensity distribution. Therefore, on the exposure surface of this embodiment shown in FIG. 1, when exposing the wafer 12 with laser light, the image rotation prism 24 is rotated, and the laser light with a substantially uniform cross-sectional intensity distribution is emitted by the illumination optical system 6. It is enlarged and directed towards the reticle 9.

Now, the two laser beams from the pinhole 29 that enter the reflecting mirror 25 are reflected by the reflecting mirror 25 and converged, and the optical lens 2
6 and converge onto the line sensor 27, respectively. The laser beam emitted from the laser 1 is a parallel beam or a beam spread (or converged) at a predetermined angle, and the anamorphic beam expander system (21.22) not only expands this laser beam but also converts it into a parallel beam. Configured to eject. Therefore, the laser light incident on the beam shaping member 23 is a parallel beam as long as the laser 1 is operating normally, and after passing through the circular opening 23A of the beam shaping member 23, the pinhole 29, and the image rotation prism 24, Each laser beam also becomes a parallel beam of light. In this embodiment, the positional relationship between the two is determined so that the light receiving surface of the line sensor 27 is at the focal point of the condensing lens 26, and the condensing lens 26
6 is reflected by the reflecting mirror 25 and each receives a laser beam consisting of a parallel beam, so the laser 1 is operating normally and each member (5, 21, 22, 23, 24) is accurately If set, these two laser beams are focused by the condensing lens 26 onto the same position on the light receiving surface of the line sensor 27. The illuminance distribution on the light receiving surface of the line sensor 27 at this time is shown in FIG. 5(A). Figure 5 (
In A), the illuminance is plotted as the output level of the line sensor 27 on the vertical axis of the graph, and the incident position of the laser beam on the light receiving surface is plotted on the horizontal axis of the graph, and the illuminance distribution on the light receiving surface of the line sensor 27 is drawn. .

Furthermore, as described above, the output signal from the line sensor 27 is input to the laser beam monitor device 31 via the signal line 30. In this embodiment, the laser beam monitor device 3
The maximum illuminance on the light receiving surface of the line sensor 27 (peak value of the output signal from the line sensor 27) and the maximum illuminance on the light receiving surface in the state shown in FIG. (The peak position of the output signal is stored as the reference intensity and reference position, respectively.Then, by detecting the peak value and the deviation of the output signal from the line sensor 27 from the reference intensity and reference position, , monitors changes in the beam system and spread angle (parallelism) of the laser beam.For example, changes in the operating characteristics of the laser 1 or changes in the setting position of the member (5.21.22) may cause the beam shaping member to change. As the spread angle of the laser beam incident on the pinhole 23 increases, the incident angle of the laser beam incident on the two pinholes 29 also changes, so the output signal from the line sensor 27 becomes as shown in FIG. 5(B). Furthermore, when the beam diameter of the laser beam incident on the beam shaping member 23 increases due to the same reason (however, the laser output is constant and the laser beam is a parallel beam), the intensity of the laser beam incident on the two pinholes 29 increases. becomes smaller, so the line sensor 27
The output signal from is shown in Figure 5 (C). In this way, if the line sensor 27 detects the laser beam extracted through the pinhole 29 formed around the circular aperture 23A of the beam shaping member 23 that shapes the cross-sectional shape of the laser beam, the wafer of the laser beam can be detected. The utilization efficiency for exposing the wafer 12 can be increased, and the exposure time when exposing the wafer 12 can be shortened. Also,
Since the laser beam monitor device 31 can constantly monitor the beam diameter and divergence angle of the laser beam, fluctuations in the beam diameter and divergence angle of the laser beam incident on the illumination optical system 6 are detected and automatically corrected. It also becomes possible. Particularly, as in this embodiment, when the laser 1 and the exposure apparatus main body A are installed on different bases, and the laser beam from the laser is guided to the exposure apparatus main body A via the transmission optical system B, which has a relatively long optical path. Since the transmission optical system B must be set with high precision, it is effective to use the output signal of the line sensor for adjusting the transmission optical system B. Furthermore, since fluctuations in the operating characteristics of the laser 1 itself can be detected, there is also the advantage that abnormalities in the laser 1 can be detected early.

In this embodiment, in order to more efficiently guide the laser light from the laser 1 to the exposure apparatus main body A, the lenses (21, 22, 28) and the image rotation prism 2 constituting the transmission optical system B are used.
9 is made up of Sin2. Further, the lenses in the illumination optical system 6 of the exposure apparatus main body A and the projection lens 10 are also in the Sin. It is made of a glass material that has good transmittance to laser light such as.

In FIG. 2, the reflecting mirror 25 simultaneously reflects the laser beams from the two pinholes 29 and directs them toward the condensing lens 2. However, the size of the reflection ut25 is further reduced, and the laser beams from the two pinholes 29 are directed to the condensing lens 2. It is also possible to configure the laser beam to be sequentially reflected by the reflecting mirror 25, directed toward the condenser lens 26, and received alternately by the line sensor. Furthermore, although the beam shaping member 23 transmits the laser beam through the circular aperture 23A, an elliptical reflective surface may be formed on the opaque substrate instead of the circular aperture 23A to make it a reflective beam shaping member. You can also. In this case as well, the elliptical reflective surface reflects near the center of the incident laser beam, and the laser beam with a circular cross section is directed toward the illumination optical system 6 through at least one pinhole provided around the reflective surface. Aim the laser beam at the line sensor 26. The reflective light beam shaping member is, for example, a second
It is sufficient to obliquely install the reflecting mirror 5 located between the beam expander system (21, 22) and the image rotation prism 24 in the figure so as to reflect the laser beam in the direction of the image rotation prism 24. It becomes possible to directly collect the laser light that has passed through the pinhole with a condenser lens and direct it to a photodetector such as a line sensor. Therefore, a member for bending the optical path, such as the reflecting mirror 25 shown in FIG. 2, becomes unnecessary.

On the other hand, by slightly changing the configuration of FIG.
5 and the condenser lens 26 can be omitted. That is, if the laser beam from the pinhole 29 of the beam shaping member 23 is directly received by a two-dimensional sensor array such as a CCD without directing it to the image rotation prism 24, and the output of this sensor array is input to the laser beam monitor device 31. good.

Regardless of the configuration described above, it is possible to obtain the same effect as the exposure apparatus shown in FIGS. 1 and 2, and as shown in FIG. The present invention is applicable to various types of exposure apparatuses, including not only an exposure apparatus that projects a pattern onto a substrate to be exposed, but also one that scans a substrate to be exposed with a laser beam to draw a pattern. The embodiments described above use a line sensor or a two-dimensional sensor array as a photodetector to detect variations in the beam diameter and divergence angle of laser light, but the present invention uses a photodetector. It is not limited to the form used for such purposes. For example, a configuration may be adopted in which a photoelectric conversion element receives laser light from a pinhole in a beam shaping member, and an output signal from the photoelectric conversion element is input to an integrating exposure meter to control the exposure amount. In this case as well, since the laser beam that is cut off by the beam shaping member and directed toward the illumination optical system is detected, it is possible to improve the utilization efficiency of the laser beam used for exposure.

Also, instead of forming a pinhole in the beam shaping member to guide the laser beam to the photodetector, a minute reflective surface is formed at a predetermined location around the aperture of the beam shaping member, and this minute reflective surface guides the laser beam. It is also possible to extract it by reflection and direct it to a photodetector.

(Effects of the Invention) As described above, according to the present invention, since the light extraction part is formed near the light transmission part to guide the laser light incident around the light transmission part of the light flux shaping member to the photodetector, the laser Exposure equipment that improves laser light usage efficiency by guiding unnecessary light that is not transmitted to the substrate to be exposed, such as Kuehashi, to a photodetector without installing a beam splitter or the like in the optical path of the light. Therefore, the exposure time when exposing the substrate to be exposed can be shortened, resulting in an exposure apparatus with high throughput.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an exposure apparatus according to the present invention. FIG. 2 is an enlarged view showing a specific configuration of the transmission optical system shown in FIG. 1. FIG. 3 is a plan view of the beam shaping member. FIG. 4 is a schematic diagram showing the state of laser light emitted from a rotating image rotating prism. FIGS. 5(A) to 5(C) are graphs showing examples of output from the line sensor. 1... Laser 6... Illumination optical system, 9
... Reticle, 10... Projection lens, 1
2... Wafer, 20... Laser light,
23 Luminous flux shaping member, 23A... circular aperture, 2
4--Image rotation prism, 26--Line sensor, 29--Pinhole 2q lv day (Afu ζβ)

Claims (7)

[Claims] (1) In an exposure apparatus that exposes a substrate to be exposed with laser light from a laser, a light beam shaping member includes a light transmission section of a predetermined shape that shapes the cross-sectional shape of the laser light, and a light transmission section of the light flux shaping member. an optical system that directs the laser beam from the substrate toward the exposed substrate; and a light extractor formed near the light transmission section of the beam shaping member to guide the laser beam incident around the light transmission section to a photodetector. An exposure apparatus comprising: (2) Exposure according to claim (1), characterized in that the light extraction section is made of a pinhole, and further includes a reflecting mirror that guides the light that has passed through the pinhole to the photodetector. Device. (3) The exposure apparatus according to claim (2), wherein the laser is an excimer laser, and the light transmission section is configured with a circular aperture. (4) The photodetector is composed of a sensor array, and further includes a condenser lens between the sensor array and the reflector that focuses the light reflected by the reflector onto the sensor array. An exposure apparatus according to claim (2). (5) The optical system has an image rotating prism that is rotatable about the optical axis of the optical system, and the reflecting mirror receives light from the pinhole via the image rotating prism. An exposure apparatus according to claim (2). (6) The exposure apparatus according to claim (2), wherein the photodetecting section is comprised of a plurality of pinholes. (7) The patent further comprises a detection means for receiving a signal obtained by photoelectric conversion by the photodetector and detecting a variation in the beam diameter of the laser beam according to the magnitude of the signal. An exposure apparatus according to claim (1).