JPH07115047A - Vertical detection device, horizontal detection device, illumination optical device and aligner wherein they are used - Google Patents

Abstract

PURPOSE:To realize a focal device which is free from deterioration of measurement accuracy caused by difference of local reflectance of a substrate, inclusion of diffraction light by a fine pattern on a substrate, waviness of a local substrate surface, etc., and an illumination optical system which restrains generation of local speckles and has further uniform illumination light intensity distribution. CONSTITUTION:An aligner comprises a projection lens 4 which carries out projection for transferring a pattern to be exposed generated in a reticle 3 to a substrate by reduction, an illumination optical system 2 which treats projected light from a laser light source 1 to become exposure light suitable for exposure, a stage 9 which mounts and moves the reticle 3 and a substrate, respectively and an alignment mechanism which aligns the reticle 3 and a substrate. A focal device comprises a vertical detection device 6 which measures a position of a substrate to a focal position of the projection lens 4 and a horizontal detection device 8 which measure an angle of a substrate surface to an optical axis of the projection lens 4 for arranging the image surface of the reticle 3 reduced by the projection lens 4 parallel to a substrate surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus that transfers a pattern onto an object via a projection optical system.

[0002]

2. Description of the Related Art In recent years, semiconductor devices, which have been the driving force of technological innovation, are becoming more and more dense, and the fine pattern of each element is about 0.5 μm or less. As a semiconductor pattern manufacturing means, an exposure device that reduces and transfers a pattern drawn on a reticle onto a wafer by a projection lens is used. When pattern transfer is performed using the above exposure apparatus, the wafer surface must be placed on the focal plane of the projection lens prior to exposure, but the focal depth of the projection lens becomes shallower as the transfer pattern becomes finer, so the focal plane Accurate wafer placement technology is important.

Further, as the transfer pattern becomes finer, the wavelength of exposure light is becoming shorter, and in recent years, excimer laser light having a wavelength of 250 nm or less is about to be used as exposure light. In general, the beam diameter of the light emitted from the excimer laser is small and the intensity distribution is large. Therefore, in order to perform a uniform pattern transfer over the entire exposure area, the beam diameter should be increased to a beam with a uniform intensity distribution. An illumination optical system for correction is required.

A conventional exposure apparatus will be described below with reference to FIG. In FIG. 9, 101 is a focusing device, 1
Reference numeral 02 is an illumination optical system.

First, the structure of the focusing device 101 will be described. In FIG. 9, 103 is a wafer, and 104 is a wafer stage for moving the wafer 103 three-dimensionally. In focusing adjustment, movement in the direction along the optical axis of the projection lens and angle adjustment of the wafer surface are performed. . 105 is a reticle,
Reference numeral 106 is a projection lens for projecting and exposing the pattern of the reticle 105 onto the surface of the wafer 103, 107 is a light emitting element such as an LED, and 108 is a lens system for converting the light emitted from the light emitting element 107 into parallel rays. Reference numeral 109 denotes a light-sending slit, which is provided with a rectangular slit for passing a part of the parallel rays and is arranged so that the center of gravity of the slit coincides with the optical axis. 110 is a lens system for forming an image of the light beam selected by the light-sending slit 109 on the surface of the wafer 103, 111 is a lens system for forming an image of the light beam reflected on the wafer 103 again, and 112 is a lens system 11
1, a PSD element for detecting the position of reflected light from the wafer 103, which is provided at the image forming position of 1, a position detection circuit 93,
A wafer stage control drive circuit 94 controls the amount of movement of the wafer stage 104.

The operation of the focusing device of the exposure apparatus configured as described above will be described below. In FIG. 9, the reticle 105, the projection lens 106, the wafer 10
In the optical system of No. 3, the focal plane of the reticle pattern is the wafer 103.
It shows the state of matching with the surface of. Light emitting element 10
The light from 7 is collimated by the lens 108. Of this parallel light, the light near the optical axis passes through the light transmission slit 109,
The lens 110 forms a real image of the sending slit near the intersection of the optical axis of the projection lens 106 and the wafer surface. This image is reflected on wafer 103, passes through lens 111 and again PS
An image is formed on the surface of the D element 112, and the slit image position is detected. When the angle and height of the surface of the wafer 103 change, the image forming position of the light-sending slit on the light receiving surface of the PSD element 112 moves, and this is utilized to move the wafer surface in the optical axis direction (hereinafter referred to as the wafer height). ) And the tilt of the surface with respect to the optical axis. In advance, the position Z ₀ of the image of the light-sending slit in the state where the wafer surface and the focal plane of the projection lens coincide with each other is measured. From the next, by moving the wafer stage 104 so that the position Z of the light-transmitting slit image coincides with Z ₀ , it becomes possible to coincide the focal plane of the projection lens with the wafer surface.

Next, the structure of the illumination optical system 102 will be described. In FIG. 9, 113 is a laser light source, for example, a light source such as an excimer laser. 114, 115,
Reference numerals 116 and 117 are reflection mirrors for ultraviolet light, 118 is an optical system including a cylindrical lens, 119 is a reflection mirror for ultraviolet light, and 120 is a beam expander and the beam diameter of the laser is approximately the first fly-eye lens 121.
It expands to the size of the opening. Reference numerals 122 and 124 are lenses, and 123 is an ultraviolet light reflection mirror. 12
5 is a second fly-eye lens, 121, 122 and 1
24 and 125 are called an optical integrator for uniformly illuminating the reticle. Reference numeral 126 is a condenser lens, 127 is a reflection mirror for ultraviolet light, and 1
Reference numeral 28 denotes a main condenser lens which collects the beams emitted from the optical integrators 121 and 125. 9
9 is a pupil position of the projection lens 106.

Next, the operation of the illumination optical system in the conventional example of the present invention will be described. In FIG. 9, the laser beam 129 oscillated by the excimer laser light source 113 is
The light enters the optical system 118 including a cylindrical lens through the ultraviolet light reflection mirrors 114, 115, 116, 117, and is shaped into a substantially square beam LBo from a beam LBi having a rectangular cross section. The beam LBo is bent by the reflection mirror for ultraviolet light and enters the beam expander 120. The parallel beam LBo having a substantially square cross-section emitted from the beam expander 120 passes through the first fly-eye lens 121 and the lens 122, and the reflection mirror 12 for ultraviolet light.
It is incident on 3. The beam reflected by the mirror 123 passes through the lens 124 and the second fly-eye lens 125.
To the main condenser lens 1 after being condensed into a large number of spot lights and then diverged, and then condensed again by the condenser lens 126 and reflected by the reflection mirror 127 for ultraviolet light.
It is incident on 28. Each of a large number of spot lights that are excessively condensed by the main condenser lens 128 are all superposed on the reticle 105 to have a uniform illuminance distribution and illuminate the reticle 105. This allows the reticle 105
The upper circuit pattern is projected onto the wafer 10 by the projection lens 106.
3 is reduced and projected, and the pattern is exposed.

Here, the projection lens 106 is telecentric on both sides, and the spot light formed on both emission sides of the second fly-eye lens 125 is located at the position of the pupil 99 of the projection lens 106 by the condenser lens 126, the main condenser lens 128 and the like. Is almost conjugated with. In other words, the spot light source (focusing point of the beam) of the spot light is formed in the pupil 99 by the product of the number of lens elements of each of the first and second fly-eye lenses 121 and 125. This is also advantageous in terms of making the intensity distribution of the light source image at the pupil 99 uniform.

Further, the first and second fly-eye lenses 12
Reference numerals 1 and 125 denote first and second fly-eye lenses 121 and 12 with an optical axis as a rotation axis by a rotation driving unit (not shown).
5, or only the second fly-eye lens 125 is rotationally driven, and a rotational driving control system (not shown) works only when laser oscillation is generated by a trigger from the excimer laser light source 113, and every time the pulsed light is emitted. Since the fly-eye lenses 121 and 125 are rotated, the interference fringes generated by the spot light can be rotated to uniformize the interference fringes, and apparently uneven illumination due to the interference fringes can be reduced.

Next, as a method for improving the uniformity of the output illuminance of the conventional proof optical system, Japanese Patent Laid-Open No. 62-115119.
FIG. 10, FIG. 11, and FIG.
2 and FIG. 13 will be described. FIG. 10 is a cross-sectional view as seen from a direction along the optical axis direction of a fly-eye lens in a conventional illumination optical system. In FIG. 10, 140 is a housing, and 130 is a clamp element for fixing the fly-eye lens 131. A blocking mask 132 blocks the output beam, and
It is fixed at 0. FIG. 11 is a schematic perspective view of the fly-eye lens 131, FIG. 12 is a front view of a blocking mask, and FIG. 13 is a block diagram in which the center of some fly-eye lenses 131 is blocked by metal deposition and other fly-eye lenses are used. It is a front view showing the state where eye lens 131 is blocked.

The operation of the fly-eye lens constructed as described above will be described below. In FIG. 10, FIG. 11, FIG. 12, and FIG. 13, the output illuminance distribution from the light source (not shown) is detected by photodetectors (not shown) at various points on the image plane (wafer surface) (not shown). Etc. The output intensity non-uniformity is then taken as the difference between the maximum and minimum normalized photodetector readings and divided by the average of all normalized readings. And a weighting function related to the light contribution of the output illuminance. This is accomplished by measuring the intensity of the light input from the light source to the fly-eye lens 131.

Next, an appropriate fly-eye lens 131 for a block is selected from the fly-eye lenses 131 having a weighting function, and the selected fly-eye lens 131 is selected.
The central portion of the optical input surface 1311 can be blocked by a method such as metal deposition. FIG. 13 shows an example of the blocking patterns 1312 and 1313.

Next, in another embodiment of the method for improving the uniformity of output illuminance, a mask element 132 having a special shape is arranged at the input portion of the fly-eye lens 131 and positioned at a single portion of the fly-eye lens 131. Multiple fly-eye lenses 1
By partially blocking 31 it is possible to obtain a substantially equivalent improvement in output illuminance uniformity. Mask element 1
An example of 32 is shown in FIGS. Mask 1
The outer shape of 32 is a shape convenient for mounting on the housing 140, and the mask 132 has an open inner portion 1321 and a plurality of mask protrusions 1322, 1323 protruding into the open inner portion 1321. Protrusion 13
Reference numerals 22 and 1323 denote fly-eye lenses 1 arranged around the lens.
It has a function of partially blocking 31, and the output illuminance can be made uniform by partially blocking the fly-eye lens 131 arranged around it.

[0015]

However, in the configuration of the conventional focusing device described above, the spot of the incident light flux on the surface of the wafer 101 has a finite size because the light-transmitting slit has a finite slit width. When the spot extends over a boundary having different reflectance, the intensity distribution within the reflected light flux changes. As a result, the barycentric position of the light intensity distribution in the spot on the PSD element 109 moves by a certain amount from the barycentric position (light beam center) when the reflectance is uniform. Therefore, although the height and angle of the surface of the wafer 101 are not changed, the position of the center of gravity of the light intensity distribution measured by the PSD element 109 is changed, which causes an error at the time of focusing, resulting in an accurate correction. There is a problem that it becomes difficult to adjust the focus position.

Further, in the above-mentioned configuration of the conventional illumination optical system, when a highly coherent light beam such as an excimer laser is used as the exposure light for the exposure light, the fly-eye lens is rotated or the mask is used for blocking. Only with this, speckle patterns and interference fringes are generated on the reticle surface, and it is not possible to guarantee that the exposure light intensity is uniform on the reticle surface. This illuminance distribution cannot be dealt with simply by blocking with metal vapor deposition or the like, which has been a problem in transferring a fine pattern of 1 μm or less.

The present invention is to solve the above-mentioned problems of the prior art. In the focusing device, the focusing surface of the projection lens of the material to be exposed is not affected by the nonuniformity of the reflectance of the material to be exposed such as a semiconductor wafer. It is an object of the present invention to provide an exposure apparatus capable of accurately arranging. Further, in the illumination optical system, it is possible to provide an exposure apparatus having a uniform illumination optical system by suppressing the generation of speckles, detecting the light intensity distribution on the reticle surface, and controlling the luminous flux intensity in a region with high illuminance. The purpose is to

[0018]

To achieve this object, the present invention comprises a projection lens for projecting a pattern of a reticle on which a pattern to be exposed is drawn for reduction and transfer to a substrate, and a laser from a laser light source. In an exposure apparatus including an illumination optical system that corrects emitted light into exposure light suitable for exposure, a stage that mounts and moves a reticle and a substrate, and an alignment mechanism that aligns the reticle and the substrate,
The alignment mechanism has a focusing device that matches the focal plane of the projection lens and the substrate surface, and the focusing device arranges the reduced image plane of the projection lens of the reticle and the substrate surface in parallel to each other. It consists of a vertical detector that measures the position of the substrate with respect to the focus position and a horizontal detector that measures the angle of the substrate surface with respect to the optical axis of the projection lens.

The horizontal detecting device includes one light source,
An illumination optical system configured to illuminate a light beam emitted from a light source on a substrate by a parallel light beam, an optical glass substrate having a finite thickness disposed in the light beam, and an axis perpendicular to the optical glass substrate. A rotating mechanism that can freely rotate around, a reflection mirror that reflects specularly reflected light from the substrate in the opposite direction, and a part of the reflected light that is arranged after the reflected light is reflected by the substrate again and again passes through the optical glass substrate. A beam splitter that reflects light, a detector that photoelectrically converts the collected light, a drive part of the rotation mechanism, and signal processing that calculates the tilt of the substrate from the synchronization signal of rotation from this drive circuit and the detection signal from the detector. It is composed of a circuit section.

Further, the vertical detection apparatus includes an optical element that functions as a lens provided on the reticle, a light source that emits coherent light having a wavelength different from that of the exposure light and illuminates the optical element, and the reticle and the projection. A signal for detecting the position of the substrate in the direction parallel to the optical axis of the projection lens from the detection signals from the plurality of detection optical systems that detect the intensity of the light beam reflected by the substrate via the lens and the plurality of verification optical systems. It is composed of a processing circuit unit. Furthermore, the illumination optics
First light source image generating means for generating a large number of light source image groups from a beam emitted from a laser light source, and second light source image for generating a large number of light source images using the beams from the first light source image generating means. Generating means, irradiating means for illuminating a surface to be irradiated in a state where the beams emitted from the second light source image generating means are superposed, illuminance distribution detecting means for detecting an illuminance distribution on the surface to be irradiated, and the illuminance distribution The light quantity adjusting means adjusts the irradiation light quantity according to the output signal from the detecting means, and the control means controls the light quantity adjusting means according to the output signal detected by the illuminance distribution detecting means. .

[0021]

In the vertical detection apparatus of the present invention, the optical element acting as a lens provided on the reticle is illuminated with coherent light having a wavelength different from the exposure light to generate scattered light. Part of the generated scattered light passes through the projection lens,
After that, the light is reflected by the substrate surface, passes through the projection lens again, and is incident on the optical element that functions as a lens provided on the reticle. The light beam that has passed through the optical element forms an image at a specific position depending on the relative positions of the reticle, the projection lens, and the substrate. The image forming position of the light beam is detected by detection optical systems arranged at a plurality of different positions, and accordingly, the deviation between the focal position of the projection lens and the position of the substrate is detected. This makes it possible to perform focusing without causing deterioration in measurement accuracy due to differences in local reflectance of the substrate, mixing of diffracted light due to a fine pattern on the substrate, and local waviness of the substrate surface.

Further, in the horizontal detection device of the present invention,
By continuously or intermittently scanning a plurality of locations in the exposure area on a substrate with a light beam for horizontal measurement, it is possible to measure the surface inclination at a plurality of locations in the exposure area. Differences in reflectance, mixing of diffracted light due to fine patterns on the substrate, and deterioration of measurement accuracy due to local waviness on the substrate surface, etc. Averaging measured values at multiple points, weighted averaging, majority processing It is possible to perform highly accurate horizontal alignment by performing statistical processing such as.

Further, in the illumination optical system of the present invention, the N light beams generated by the N lens groups forming the fly-eye lens, which is the first light source image generating means, are generated into the second light source image. Inject the means. Here, the M small lens groups forming the fly-eye lens, which is the second light source image generating means, split the beam into N × M beams. The separated beams are incident on the light amount adjusting means composed of M electro-optical elements corresponding to the second light source image generating means composed of M small lens groups. Here, the electro-optical element is controlled by the control unit that controls the irradiation light amount according to the output signal detected by the illuminance distribution detection unit that detects the illuminance distribution on the illuminated surface, and the uniformity of the entire light amount is of course Further, it is possible to suppress the occurrence of partial speckles and obtain an illumination optical system having a more uniform illumination light intensity distribution.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an exposure apparatus in one embodiment of the present invention. In FIG. 1, reference numeral 1 is a laser light source section for generating exposure light, and 2 is an illumination optical system for correcting a light beam emitted from the laser light source section 1 into a light beam suitable for exposure. 3 is a reticle, 4 is a projection lens, and 5 is a wafer. The projection lens 4 transfers the pattern on the surface of the reticle 3 onto the surface of the wafer 5 coated with the photosensitive material. Reference numeral 6 denotes a vertical detection unit that measures the surface distance between the focal plane of the projection lens 4 and the wafer 5 surface. An exposure position detection unit 7 measures the relative positional relationship between the real image position of the pattern on the surface of the reticle 3 by the projection lens 4 and the exposure position on the surface of the wafer 5. A horizontal detection unit 8 measures the parallelism between the focal plane of the projection lens 4 and the wafer 5 surface. 9 is the stage, 1
Reference numeral 0 denotes a stage control drive circuit, which determines the detection results of the vertical detection unit 6, the exposure position detection unit 7, and the horizontal detection unit 8 by the stage control drive circuit 10, and sets the exposure surface of the wafer 5 to the focal plane of the projection lens 4. The stage 9 is moved so that the patterns of the reticle 3 are aligned and exposed to a predetermined position.

In the exposure apparatus configured as described above, the apparatus configuration of the vertical detection unit 6 will be described next with reference to FIG.
This will be described with reference to the schematic configuration diagram of the vertical detection unit shown in FIG.
First, 11 is a focusing light source that generates a coherent plane wave having a wavelength different from that of the exposure light. Reference numeral 12 denotes an optical element provided on the surface of the reticle 3, which has a function of converging and diverging a light beam like an ordinary lens. The cross-sectional size of the light flux emitted from the focusing light source 11 is about the same as the effective diameter of the optical element 12. Reference numerals 13 and 14 are half mirrors, 15 is a total reflection mirror, and 16 is a lens system, and the light emitted from the focusing light source 11 is introduced into the optical element 12 by the half mirror 13. The light flux that has passed through the optical element 12 passes through the projection lens 4, is reflected by the wafer 5, and then passes through the projection lens 4, the optical element 12, and the lens system 16 again. The light flux after passing is split into two light fluxes by the half mirror 14 and the total reflection mirror 15. Reference numerals 17 and 18 denote apertures, and reference numerals 19 and 20 denote light receiving elements. A part of the light flux from the half mirror 14 and the total reflection mirror 15 is used as an aperture 17, 18
The light intensity is measured by the light receiving elements 19 and 20. Reference numeral 21 is a signal strength comparison circuit,
The light intensity measured at 0 is compared to calculate where the wafer 5 is located with respect to the focal position of the projection lens 4. Reference numeral 10 denotes a stage control drive circuit, which is based on the measurement result from the signal intensity comparison circuit 21 and causes the wafer 5 to project onto the projection lens 4.
The stage 9 is controlled and driven so as to be positioned at the focal point of.

The principle of wafer position detection of the vertical detection unit 6 configured as described above will be described below with reference to FIG. The light flux emitted from the focusing light source 11 passes through the optical element 12 and the projection lens 4, and the combined focal length of the two is f1. Further, the light flux reflected by the wafer 5 again passes through the projection lens 4 and the optical element 12 and is converged by the lens system 16, and the combined focal length of the projection lens 4, the optical element 12 and the lens system 16 is f2. .
Considering as described above, the luminous flux emitted from the focusing light source 11 reaches the light receiving elements 19 and 20 until the focal length f.
It is equivalent to passing two lenses of 1 and f2.
Here, if the distance between the two lenses is D, and the position of the wafer 5 is moved away from the projection lens 4 by d, the focal length f
Since the lens interval of 1 and f2 is D + 2d, the focal position of the light emitted from the focusing light source 21 changes. The light intensities at different positions are measured by the apertures 17 and 18 and the light receiving elements 19 and 20. By comparing them, the focus position when the light emitted from the focusing light source 11 passes through the lens system 16 is determined. It is calculated. If the focus position of the light emitted from the focusing light source 11 when the reticle 3, the projection lens 4, and the wafer 5 are in the correct positions is registered in advance, the wafer 5 is always adjusted so that the focus positions will be the same thereafter. Focusing becomes possible by moving.

Focusing can be performed by the same device configuration as in FIG. 2 without the optical element 12, but by providing the optical element 12 at the reticle position, the projection lens 4
The information of the reticle position with respect to can also be extracted, and the projection magnification of the projection image of the reticle 3 on the surface of the wafer 5 can be made constant. The lens system 16 is provided to shorten the combined focal length of all the lens systems, and amplifies a change in light intensity measured by the two light receiving elements as the wafer 5 moves. By inserting the lens system 16 as described above, more accurate focusing becomes possible.

The optical element 12 may have any structure as long as it has a function of converging and diverging a light beam like a lens. For example, as shown in FIG. 3, it is advisable to provide a Fresnel pattern on a part of the transfer pattern on the reticle by chrome plating similarly to the transfer pattern. The transmitted diffracted light in the Fresnel pattern forms one focal point and has the same function as a lens.

As described above, in the vertical detection unit 6 in the exposure apparatus of the present embodiment, an optical element having the same function as a lens is provided on the reticle, and the optical element is illuminated with a coherent light beam so that the transmitted light is By measuring the focal position formed after passing through the projection lens and being reflected by the wafer and passing through the projection lens and the optical element again, the partial reflectance difference of the wafer, the local waviness of the wafer surface, and the wafer surface Focusing that is not affected by the diffraction of fine patterns and speckles becomes possible.

Here, in the embodiment of the vertical detection unit 6 described above, the number of apertures and light receiving elements is two, but three or more may be provided. By providing a large number of light receiving elements,
It becomes possible to measure the light intensity at multiple points at different positions, and by statistically processing the measurement results, it is possible to obtain a vertical detection unit capable of an accurate focusing operation that is not affected by changes in the light intensity due to residual aberration of the lens. You can

Next, the device configuration of the horizontal detection unit 7 in the embodiment of the present invention will be described with reference to the schematic configuration diagram of the horizontal detection unit shown in FIG. FIG. 4 is a configuration diagram of the horizontal position detection unit 8 of the exposure apparatus in one embodiment of the present invention. In FIG. 4, 5 is a wafer, and 9 is a stage for moving the wafer 5 three-dimensionally. The tilt adjustment mainly moves in the tilting direction. 4 is a projection lens for projecting and exposing a pattern of a reticle (not shown) on the surface of the wafer 5, 22 is a light emitting element (light source) such as an LED, and 23 is for correcting light emitted from the light emitting element 22 into parallel rays. The light emitting element 22 is provided in the vicinity of the focal point of the lens 23. Reference numeral 24 denotes a light-sending slit of the irradiation optical system, which is provided with a slit for passing a part of the parallel light beam, and is provided so that the center of this slit coincides with the optical axis. Reference numeral 25 is an optical glass substrate parallel shifter that shifts the optical axis to irradiate different positions on the wafer 5 with the slit light emitted from the light-transmitting slit 24, and 26 is the same slit light reflected on the wafer 5. A mirror for reflecting the light so as to pass through the optical path, 27 is a mirror 26
A lens for condensing the reflected light partially reflected by the half mirror 28, a PSD for detecting the position of the center of gravity of the condensed light, 30 a position detection circuit, and 10 a position detection A wafer stage control drive circuit for moving the wafer stage 9 in two tilt directions based on the output of the circuit 30. Reference numeral 31 denotes a shifter drive circuit, which controls the tilting operation of the parallel shifter 25.

The operation of the above arrangement will be described below with reference to FIG. FIG. 5 is a schematic diagram for explaining the operation principle of the horizontal detection unit. In FIG. 5, the reticle (not shown), the projection lens 4, and the wafer 5 are optical systems, and the focal plane of the reticle pattern is the wafer 5.
Is shown on the surface of the light-receiving surface, and the light receiving position on the PSD element surface of the image by the lens 27 of the light transmitting slit 24 at this time is Z0. The light from the light emitting element 22 is collimated by the lens 23. Of this parallel light, the light near the optical axis passes through the light-sending slit 24, passes through the parallel shifter 25, immediately below the center of the projection lens 4, and on the surface of the wafer 5 in parallel with the opening shape of the light-sending slit 24. The luminous flux is emitted. This light flux is reflected on the surface of the wafer 5, reflected by the mirror 26, again reflected by the wafer 5, again passed through the parallel shifter 25, and partially reflected by the half mirror 28, resulting in PSD.
The element 29 receives the light and detects the spot position of the light beam.
Since the wafer 5 is located at the horizontal position Z = Z0 as described above, the output signal from the position detection circuit 30 becomes zero.
Then, the inclination of the wafer 5 surface can be detected from an output signal from the position detection circuit 30 (for example, an optical path like a dotted line when deviated from the horizontal position) obtained corresponding to the movement amount of the wafer stage 9.

Here, as shown in FIG. 4, the parallel shifter 25 can be rotated by a shifter drive circuit 31 along an axis perpendicular to the optical axis, and by rotating the parallel shifter 25, light is transmitted. Since the light flux after passing through the slit 24 can be moved parallel to the optical axis, the slit light can be irradiated to different positions on the wafer 5. At this time, since the light flux shifted by the parallel shifter 25 moves in parallel, if the angle of the wafer 5 surface is constant, the wafer 5
The PSD element 29 of the light beam spot imaged by the condenser lens 27 even if the light beam is irradiated to any position on the surface.
Since the position above does not change, the tilt amount of the wafer 5 can be measured regardless of the irradiation position on the wafer 5.

The parallel shifter 25 is provided in the horizontal detection unit 8 in this embodiment for the following reason. In the situation where some pattern has already been transferred to the exposure area on the wafer 5, the illumination area on the surface of the wafer 5 may sometimes straddle an area having different reflectance.
The slit width of the light sending slit 24 is infinitely small, and the lens 2
If 3 and 27 have no aberration and the image forming surface of the lens 27 and the light receiving surface of the PSD element 29 coincide with each other, even if the above situation is encountered, the measurement of the angle of the wafer 5 surface is not affected. But,
Actually, the light transmitting slit 24 has a finite slit width,
The lenses 23 and 27 have aberrations. Further PSD element 2
It is difficult to completely position the light receiving surface of 9 on the image forming surface of the lens 27. Therefore, since the spot of the slit light on the light receiving surface of the PSD element 29 has a finite size, in the above situation, the measurement of the tilt of the wafer 5 surface is affected by the change of the reflectance in the illumination area on the wafer 5 surface. To be done. Further, the surface of the wafer 5 is not a perfect flat surface but has a slight undulation. Therefore, even if the local surface angle of the wafer 5 is measured, it cannot be said that the surface angle of the exposure region is necessarily measured.

As described above, in the illumination area of the slit light on the wafer 5 surface, when there is a change in the reflectance with respect to the slit light or when there is undulation on the wafer 5 surface, the reliability of the angle measurement value of the wafer 5 surface is relied upon. Sex decreases. Therefore, the horizontal detection unit 8 in this embodiment includes the parallel shifter 25, and by changing the angle of the parallel shifter 25, the illumination area of the slit light on the wafer 5 surface is changed, and the measured values in different areas are statistically processed. This eliminates the influence on the measurement such as the aberration of the lenses 23 and 27, the mismatch between the light receiving surface of the PSD element 29 and the image forming surface of the lens 27, and the waviness of the wafer 5 surface.

As described above, according to this embodiment, the parallel light is irradiated onto the wafer, and the reflected light is reflected back by the mirror PS.
When light is received by the D element, by rotating the parallel shifter to scan multiple positions on the wafer, sufficient horizontal position adjustment is possible even if there are regions with different local reflectances on the wafer. Is.

In the embodiment, the parallel shifter 25 is set to 1
Although the structure is such that it can rotate only in the axial direction, the parallel shifter 25 may be capable of scanning the wafer 5 with a higher degree of freedom if it can rotate in the two axial directions. Further, a structure may be adopted in which two parallel shifters 25 are provided and scanning is performed in different directions.

Next, the illumination optical system 2 in the embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a schematic configuration diagram of the illumination optical system 2 in one embodiment of the present invention. In FIG. 6, reference numeral 32 is an exposure mechanism section. A laser light source 33 is a light source such as an excimer laser. 34
Is a mirror for ultraviolet reflection, 35 is a concave lens, 36 is a convex lens, the concave lens 35 and the convex lens 36 have a role of a beam expander as one lens system,
The beam diameter of the laser is approximately the first fly-eye lens 3
It is expanded to the size of 7. 37 is a first fly-eye lens for uniformly illuminating the reticle,
As shown in the plan view of FIG. 7, the fly-eye lens 37 is configured by joining a large number of quadrangular prisms (5 × 5 = 25 in FIG. 7), and each end face of each quadrangular prism is formed into a convex spherical surface. And has the function of a convex lens. Reference numeral 38 is a convex lens, and 39 is an ultraviolet reflection mirror that bends the beam emitted from the first fly-eye lens 37. Reference numeral 40 denotes a convex lens which, together with the convex lens 38, also serves as a collimator lens for collimating the beam emitted from the first fly-eye lens 37. Reference numeral 41 is a second fly-eye lens for uniformly illuminating the reticle.
It has the same configuration as the fly-eye lens 37 of
The entrance surface of the fly-eye lens 37 and the exit surface of the second fly-eye lens 41 are maintained in a substantially conjugate relationship. Here, 37, 38 and 40, 41 are collectively called an optical integrator for uniformly illuminating the reticle.

Reference numeral 42 is a light quantity adjusting means composed of an electro-optical element corresponding to the second fly-eye lens 41, which is a liquid crystal element composed of, for example, quartz glass, and 43 is the illuminance of the irradiated surface (wafer surface). The control unit controls the irradiation light amount in accordance with the output signal detected by the illuminance distribution detection unit 44 that detects the distribution. Reference numeral 45 is an ultraviolet reflecting mirror, and 46 is a condenser lens that collects the beams emitted from the two-stage optical integrators 37 and 41. 3 is a reticle on which a transfer pattern is drawn, 4
Reference numeral 7 is a reticle holder for sucking and holding the reticle 3, 4 is a projection lens for projecting the pattern of the reticle 3, and 5 is a wafer on which the pattern is printed. Reference numeral 9 denotes a stage, which moves and focuses the wafer 5 when sucking and holding the wafer 5 and baking the wafer 5. Reference numeral 45 is a surface plate of the exposure mechanism section. 44
Is an illuminance distribution detecting means for detecting the illuminance distribution on the irradiated surface (wafer surface), for example, an ultraviolet photosensor.

The operation of the illumination optical system 2 configured as described above will be described below with reference to FIG. First, the laser beam oscillated from the excimer laser light source 33 is reflected by the ultraviolet reflection mirror 34 and enters the beam expanders 35 and 36. The laser beam emitted from the beam expanders 35 and 36 and expanded into a parallel beam having a substantially square cross section enters a fly-eye lens 37 which is a first light source image generating means. Fly eye lens 37
The focal length of the convex surface on the incident surface side of
Since the beam incident on the fly-eye lens 37 is condensed by each quadrangular prism lens element in the vicinity of each convex surface on the exit surface side, N (25 in FIG. 7) spot images are formed. It The formed spot light is condensed as N × M spot lights by the fly-eye lens 41 which is the second light source image generating means, and then the diverged laser beam is bent by the ultraviolet reflection mirror 45 and the condenser lens 46.
Incident on. The incident laser beam is appropriately condensed by the condenser lens 46, and the lights from each of the multiple spot lights are all superimposed on the reticle 3 to irradiate the reticle 3 with a uniform illuminance distribution. As a result, the circuit pattern drawn on the reticle 3 is reduced and projected on the wafer 5 by the projection lens 4, and the pattern is printed.

Further, the laser beam emitted from the fly-eye lens 41, which is the second light source image generating means, is M electro-optical corresponding to the second fly-eye lens 41 composed of M small lens groups. It is incident on the element 42. As shown in FIG. 8, the structure of the electro-optical element 42 is composed of M electro-optical elements of the same number as the number of small lenses in the second fly-eye lens 41, and each electro-optical element is a laser independently. It is possible to change the light transmittance. Here, by controlling the electro-optical element 42 by the illuminance distribution control circuit 43 that controls the irradiation light amount according to the output signal detected by the ultraviolet photosensor 44 that detects the illuminance distribution on the irradiated surface, the total light amount is Of course, the uniformity of
It is possible to obtain a more uniform illumination optical device in which the generation of partial speckles is suppressed.

As described above, according to the illumination optical system of the present embodiment, the illuminance distribution detecting means provided on the illuminated surface and the illuminance distribution for controlling the illuminating light quantity according to the output signal detected by the illuminance distribution detecting means. By providing the control means and the light quantity adjusting means for adjusting the irradiation light quantity by the illuminance distribution controlling means immediately after the second fly-eye lens, it is possible to obtain uniform and uniform illumination without a decrease in the light quantity.

In this embodiment, the electro-optical element 4
The number of two electro-optical element units is the same as the number of small lenses of the fly-eye lens 41, but it is also possible to adopt a structure in which the number of electro-optical element units is larger than the number of small lenses.

As described above, the vertical detection unit 6, the horizontal detection unit 8, and the illumination optical system 2 in this embodiment cause a difference in local reflectance of the wafer surface, mixing of diffracted light due to a fine pattern on the substrate, And exposure that has a more uniform illumination light intensity distribution that can perform focusing operation that is not affected by local waviness on the wafer surface and that suppresses partial speckle generation as well as the uniformity of the overall light intensity. A device can be provided. The vertical detection unit 6, the horizontal detection unit 8, and the illumination optical system 2 can be used for various purposes as independent devices having the configurations shown in FIGS. 2, 4, and 6, respectively.

[0045]

As described above, according to the present invention, by providing a mechanism for moving a light beam in parallel with the optical axis, a plurality of exposure areas in one shot on the wafer surface are continuously or intermittently applied to the wafer surface. It is possible to measure the parallelism at a plurality of positions within the exposure area by scanning the parallel measurement light beam of. In addition, an optical element that acts like a lens is provided on the reticle, and a light source having a wavelength different from that of the exposure light is used to illuminate the focal point of the reflected light from the wafer, which is generated by scattered light. It is possible to match the position of the exposure area on the wafer surface with the focus of the projection lens by detecting with. With the above configuration, focusing can be performed without being affected by the difference in reflectance locally on the wafer surface, the local waviness of the surface, the diffracted light generated by the fine pattern existing in the exposure area, and the speckle. An excellent exposure apparatus can be realized.

Further, the illumination optical device according to the present invention comprises an illuminance distribution detecting means provided on the wafer surface, and an illuminance distribution controlling means for controlling the irradiation light quantity of the exposure light according to the output signal detected by the illuminance detecting means, By providing the light quantity adjusting means for adjusting the irradiation light quantity by the illuminance distribution controlling means immediately after the second fly's eye lens, there is no decrease in the light quantity and uniform illumination without being affected by speckles generated in the lens system in the middle. It is possible to realize an excellent exposure apparatus that can obtain

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a vertical detection unit in the same embodiment.

FIG. 3 is a schematic view of an optical element pattern acting as a lens provided on a reticle in the vertical detection unit in the same embodiment.

FIG. 4 is a schematic configuration diagram of a horizontal detection unit in the same embodiment.

FIG. 5 is a schematic diagram for explaining the operation principle of the horizontal detection unit in the embodiment.

FIG. 6 is a schematic configuration diagram of an illumination optical system in the example.

FIG. 7 is an external view of the fly-eye lens viewed from the optical axis direction in the example.

FIG. 8 is an external view of an electro-optical element in the example.

FIG. 9 is a schematic configuration diagram of a focusing device and an illumination optical system in a conventional exposure apparatus.

FIG. 10 is a cross-sectional view of a fly-eye lens in a conventional illumination optical system as seen from a direction along an optical axis direction.

FIG. 11 is a schematic perspective view of a fly-eye lens in a conventional illumination optical system.

FIG. 12 is a front view from the optical axis direction of a blocking mask of a fly-eye lens in a conventional illumination optical system.

FIG. 13 is a schematic diagram for explaining the action of a blocking mask of a fly-eye lens in a conventional illumination optical system.

[Explanation of symbols]

 1 Laser Light Source Section 2 Illumination Optical System 3 Reticle 4 Projection Lens 5 Wafer 6 Vertical Detection Unit 7 Exposure Position Detection Unit 8 Horizontal Detection Unit 9 Stage 10 Stage Control Drive Circuit 11 Focusing Light Source 12 Optical Elements 13, 14 Half Mirror 15 All Reflecting mirror 17, 18 Aperture 19, 20 Light receiving element 21 Signal intensity comparing circuit 22 Light emitting element 24 Light transmitting slit 25 Parallel shifter 29 PSD element 30 Position detecting circuit 31 Shifter driving circuit 34, 39, 45 UV reflection mirror 35 Concave lens 36, 38, 40 Convex Lens 37 First Fly-Eye Lens 41 Second Fly-Eye Lens 42 Electro-Optical Element 43 Illuminance Distribution Control Circuit 44 UV Photo Sensor 46 Condenser Lens

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoshiyuki Sugiyama 3-10-1 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Matsushita Giken Co., Ltd. (72) Hiroshi Yamashita 3-chome, Higashimita, Tama-ku, Kawasaki City, Kanagawa No. 10-1 Matsushita Giken Co., Ltd. (72) Inventor Toshiyuki Iwasawa 3-10-1 Higashisanda, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd.

Claims (6)

[Claims] 1. A pattern drawn on a first object is a second pattern.
In the apparatus for transferring to the object, an optical element that acts as a lens provided on the first object, a light source that emits alignment light having a wavelength different from the exposure light and illuminates the optical element, and passes through the optical element. And a plurality of detection optical systems for detecting alignment light obtained via the second object,
A vertical detection device comprising means for comparing the outputs of the plurality of detection optical systems and means for adjusting the position of the second object based on the signals from the comparison means. 2. The vertical detection device according to claim 1, wherein a Fresnel zone lens is used as the optical element. 3. In an object having an approximate plane, one light source, an irradiation optical system configured to irradiate a light beam emitted from the light source with parallel rays on the object plane, and arranged in the light beam. An optical glass substrate having a finite length, a rotation mechanism that rotatably supports the optical glass substrate with respect to the direction in which light rays pass, a reflection mirror that vertically reflects specularly reflected light from the object plane, A beam splitter in which the reflected light is again reflected by the object plane and passed through the optical glass substrate, and a part of the reflected light is reflected again,
From the lens that collects the reflected parallel light from the beam splitter, the detector that photoelectrically converts the collected light, the drive circuit of the rotation mechanism, the rotation synchronization signal from this drive circuit, and the detection signal from the detector A horizontal detection device comprising a signal processing circuit unit for calculating the inclination of the object plane. 4. A light source which emits pulsed laser light for illuminating an object, a first light source image generating means which generates a large number of light source images using a beam emitted from the light source, and the first light source image generating means. Second light source image generating means for generating a large number of light source images using the beam from the light source image generating means of
Irradiating means for irradiating the irradiated surface in a state where the beams from the light source image generating means are overlapped, illuminance distribution detecting means for detecting the illuminance distribution on the irradiated surface, and an output signal from the illuminance distribution detecting means An illumination optical device comprising a light amount adjusting means for adjusting an irradiation light amount. 5. The first and second light source image generating means are composed of a condenser lens and a fly-eye lens, and the incident surface of the first light source image generating means and the second light source image generating means. 5. The illumination optical apparatus according to claim 4, wherein the light quantity adjusting means is arranged outside the focal plane of the second light source image generating means while being maintained in a substantially conjugate relationship with the emission surface. 6. A projection lens for projecting an exposure pattern drawn on a reticle so as to be reduced and transferred onto a substrate.
A light source that emits pulsed laser light for illuminating the reticle, an illumination optical system for performing exposure, a stage that mounts and moves the reticle and the substrate, respectively, and alignment of the reticle and the substrate are performed. In the exposure apparatus including an alignment mechanism, the alignment mechanism has a focusing device that arranges a substrate surface on a real image plane of a pattern on the reticle formed by the projection lens, and the focusing device includes a substrate in the optical axis direction of the projection lens. It is composed of a vertical detection device for measuring the distance between the projection lenses and a horizontal detection device for measuring the horizontal plane of the substrate. The horizontal detection device irradiates one light source and light rays emitted from the light source on the substrate as parallel light rays. The irradiation optical system configured as described above, the optical glass substrate having a finite length arranged in the light beam, and the light beam passing through the optical glass substrate. A rotation mechanism that rotatably supports the direction of reflection, a reflection mirror that vertically reflects the specularly reflected light from the substrate, and a position where the reflected light is reflected by the substrate again and passes through the optical glass substrate. A beam splitter that partially reflects again, a lens that collects the reflected parallel light from the beam splitter, a detector that photoelectrically converts the collected light, a drive circuit of the rotation mechanism, and a rotation circuit from this drive circuit. The vertical detection device is composed of a signal processing circuit unit that calculates the tilt of the substrate from the synchronization signal and the detection signal from the detector, and the vertical detection device includes an optical element acting as a lens provided in a part of the reticle and the exposure light. A light source that emits alignment light having different wavelengths and illuminates the optical element, a plurality of detection optical systems that detect the alignment light that passes through the optical element and is obtained via the substrate, and the detection optical system. And a means for adjusting the position of the substrate based on the signal from the comparison means, and the illumination optical system emits pulsed laser light for illuminating the object. First light source image generating means for generating a large number of light source images using a beam emitted from a light source, and second light source image for generating a large number of light source images using a beam from the first light source image generating means. The generating means, the irradiating means for irradiating the surface to be irradiated with the beams from the second light source image generating means superimposed on each other, the illuminance distribution detecting means for detecting the illuminance distribution on the surface to be irradiated, and the illuminance distribution detecting means. An exposure apparatus comprising a light amount adjusting means for adjusting an irradiation light amount according to an output signal from the exposure device.