JPH023907A - Projection aligner - Google Patents

Abstract

PURPOSE:To always obtain a luminous distribution excellent in uniformity by operating a flare rate and a maximum flare rate, from the transmittance of a reticle and the reflectivity of a wafer, and selectively using a luminous distribution correcting filter corresponding with the above operated results. CONSTITUTION:A reticle R and a wafer W are loaded, and the transmittance TR of the reticle R and the reflectivity EW of the wafer W stored in a storing means 4 are input in an operating means 2. Based on the transmittance TR and the reflectivity RW, the means 2 operates the ratio of a flare rate F and a maximum flare rate Fmax, and discriminates which one of three regions whose boundaries are 0.6 and 0.2 the value F/Fmax exsists in. A controlling means 3 sets a luminous distribution correcting filter 16 corresponding with the discriminated region, and exposure is executed. Thereby, without directly measuring the luminous distribution on a wafer, the luminous distribution is corrected according to the reticle and the wafer to be used, and a uniform luminous distribution can be always obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection exposure apparatus capable of controlling illumination conditions, particularly illuminance distribution on an illuminated object.

[Conventional technology]

Exposure equipment is used in the manufacture of semiconductor devices, particularly highly integrated semiconductor devices such as VLSIs, and display devices that require fine patterning, and is used in various illumination optical systems for exposure. For example, as in U.S. Pat. No. 3,296,923, the basic structure is an elliptical mirror, a cold mirror, a divergent collimation lens, two fly-eye lenses, and a convergent collimation lens. There is a configuration that uniformly illuminates the object surface to be illuminated. By using such fly-eye lenses, it is possible to form a number of secondary light sources corresponding to the number of fly-eye lenses on the object surface to be illuminated, and these can illuminate the object surface to be illuminated in a superimposed manner from multiple directions. It is possible to reduce the non-uniformity of the illuminance distribution on the surface of the object to be illuminated to several percent or less.

[Problem to be solved by the invention]

However, with the recent increase in the degree of integration of VLSIs, greater uniformity of illumination is required for printing exposure of circuit patterns, and fly-eye integrators are being adopted. It is becoming difficult to obtain sufficient uniformity by using only the following methods. Moreover, in a so-called reduction projection exposure apparatus that projects and exposes a circuit pattern on a reticle onto an illuminated object, such as a wafer, through a projection lens, problems occur between the wafer surface, reticle surface, illumination optical system, and projection optical system. Flare light that reaches the wafer surface due to reflection is generally concentrated in the center around the optical axis, and there is a risk that the reflected light from various surfaces will be integrated, resulting in uneven illuminance where the illuminance at the center will be high. be. This is called the so-called 6-hot spot, and the illuminance unevenness caused by this cannot be ignored in some cases, and it has become necessary to correct the uneven illuminance distribution caused by such flare. .

Of the various surfaces that produce the reflected light that causes this flare, the reticle transmittance and the reflectance on the wafer surface are the most important factors, and the intensity of the flare light is determined by the reticle transmittance and the wafer surface reflectance. It varies greatly depending on the reflectance.

The transmittance of the reticle changes depending on its pattern,
Further, when the wafer is made of different materials, or when the wafer is made of the same material but coated with a different resist, its reflectance changes, and these changes cause a large change in the illuminance on the wafer surface. For this reason, the illuminance distribution is greatly affected by the conditions of the reticle and wafer used, and it has become necessary to correct the illuminance distribution according to the conditions of the reticle and wafer used.

Therefore, an object of the present invention is to provide a projection exposure apparatus that can maintain an optimal illumination state depending on the projection original plate such as a reticle used, or an object to be illuminated such as a wafer, and can provide more uniform illumination. It is about providing.

[Means for solving problems]

A projection exposure apparatus according to the present invention includes an illumination optical system for illuminating a projection original plate such as a reticle or a mask having a predetermined pattern, and a projection system for projecting an image of the pattern on the projection original plate onto an illuminated object such as a wafer. an optical system, an illuminance distribution correction means arranged in the illumination optical system for correcting the illuminance distribution on the illuminated object, and a transmittance value of the projection original plate; calculation means for determining the illuminance distribution state on the surface of the illuminated object from the reflectance value of the illuminated object;
and control means for converting the correction state by the illuminance distribution correction means in accordance with the output from the calculation means.

[Effect]

In the present invention as described above, an illumination optical system and a projection optical system are fixedly provided in a general exposure apparatus, and a reticle or mask as a projection original plate and a wafer as an object to be illuminated are always exchanged. Because it is a flat surface, the illuminance distribution on the wafer surface, known as the so-called hot spot, has a nearly constant tendency, and even if the reticle or wafer is replaced, the illuminance distribution will have the same tendency, but only the intensity will change. This is based on the knowledge that although the illuminance distribution on the wafer surface tends to change as the reticle or wafer is replaced, the standardized characteristics of that distribution do not change much.

According to the configuration of the present invention as described above, the illuminance distribution characteristic unique to a certain projection type exposure apparatus, that is, the characteristic characteristic of the illuminance distribution determined by the illumination optical system and projection optical system of the apparatus, is By providing two elements, the transmittance and the reflectance of the illuminated object, it is possible to estimate the illuminance distribution on the surface of the illuminated object, and it is possible to accurately correct the illuminance distribution using the illuminance correction means. It is.

That is, based on the transmittance of the reticle and the reflectance of the wafer, a calculation means estimates what kind of illuminance distribution is in the illuminance distribution characteristics specific to the projection exposure apparatus, and the calculation result is used to estimate the illuminance distribution state. Since the illuminance distribution correction means is controlled based on this, it is possible to correct the uniformity on the illuminated object surface without directly measuring the illuminance distribution on the illuminated object surface. Therefore, by giving the transmittance of the projection original plate used and the reflectance of the illuminated object to be exposed, no matter what reticle or wafer is used,
It becomes possible to always stably maintain a highly uniform illuminance distribution.

In the illumination optical system of the exposure apparatus according to the present invention, since the purpose is to correct the increase in illuminance at the central part of the object surface to be illuminated, which is called the real spot, the illuminance distribution correction means uses the illuminance at the center of the optical axis. To this end, it is effective to correct the illuminance distribution by shielding a portion of the entrance surface of the fly's eye integrator used for uniform illumination.

For this purpose, the illumination optical system in the present invention includes a light source means that supplies illumination light of a substantially parallel light flux, and a light source means arranged in the parallel light flux from the light source means to form a plurality of light converging points and superimpose the object surface to be illuminated. A fly's eye integrator has a small lens group for illuminating the object, and the incident surface of the fly's eye integrator is made almost conjugate with the surface of the object to be illuminated, and the light flux from the fly's eye integrator is guided to the surface of the object to be illuminated. It is preferable to adopt a configuration having a condenser lens for As illuminance distribution correction means, a parallel plane transparent member on which a light shielding part is formed that partially blocks the light beam incident on at least one of the small lens groups of the fly's eye integrator is used. It is effective to arrange them at a predetermined distance on the light side.

In this case, the number N of small lenses that are blocked by the light blocking part among the small lens groups that make up the fly-eye integrator
By increasing , it is possible to increase the degree of decrease in illuminance. Therefore, by appropriately converting to a parallel plane member having a different number N of small lenses for blocking light, it is possible to always maintain a uniform illumination state even if the state of the reticle or wafer used changes.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

FIG. 1 is an optical configuration diagram showing a general configuration of an embodiment of a projection type exposure apparatus according to the present invention. The luminous flux from the ultra-high pressure mercury lamp 11 is reflected by the elliptical mirror 12 and condensed onto the second focal point F of the elliptical mirror 12, and is focused by the convergent collimation lens 14.
is converted into a parallel beam of light by

An interference filter 15 that passes light in a predetermined wavelength range for exposing a resist coated on a wafer W as an object to be illuminated is disposed in this parallel light beam, and a conical convex surface and a conical convex surface having the same apex angle are disposed. A cone prism C having a concave surface
P is placed. This cone prism CP displaces the peripheral light flux of the incident parallel light flux to the center in order to compensate for the weak intensity on the axis of the light flux condensed by the elliptical mirror 14, thereby creating a dense and uniform light intensity distribution. It has the function of converting it into luminous flux. These ultra-high pressure mercury lamps 11 and elliptical mirrors 12
, the collimation lens 14, the interference filter 15, and the cone prism CP constitute a light source means 1 that supplies illumination light of a substantially parallel beam. The optical path is opened and closed by rotating a mirror shutter Ms obliquely disposed above the second focal point F, and the exposure time for the wafer is controlled TJ.

In the parallel light beam from the light source means 1, a patterned filter 16 and a fly's eye integrator 20 are arranged adjacent to the patterned filter 16. The patterned filter 16 will be described later, but the fly-eye integrator 20
Therefore, a number of secondary light sources equal to the number of small lenses constituting this side surface P are formed in the vicinity of the light emitting side surface P. The light beam from this secondary light source is reflected by the microink mirror 13, then converted into a substantially parallel light beam by the first relay lens L1, passes through the blind B, and is directed to the surface P! by the second relay lens Lz. The light is focused on the top. After being reflected by the optical path bending mirror 17, the converging condenser lens 18
The light is focused by and illuminates a reticle R serving as a projection original plate. Then, a predetermined pattern formed on the reticle as a projection original plate is projected at a predetermined magnification onto the surface of the wafer W as an object to be illuminated by a projection objective lens L0,
The resist coated on the wafer surface is exposed to light.

Here, the exit surface P1 of the fly-eye integrator 20
A plurality of light source images formed in the vicinity of become a substantial surface light source, and the image of the surface light source formed on the surface P2 by the relay lenses L+ and Lx is transferred to the entrance pupil plane P0 of the projection objective lens L0 via the condenser lens 18. The light is projected onto the wafer W surface as an object to be illuminated to perform so-called Koehler illumination. The exit pupil of the projection pair and object lens L0 is located at almost infinity, and it goes without saying that it is formed into a telescopic link on the wafer side. The blind B consists of a plurality of movable blades, and has a variable field of view whose image is formed on the reticle R surface by the second relay lens L2 and the condenser lens 18, and which regulates the area necessary for exposure on the reticle R surface. It functions as an aperture.

In FIG. 1, the light rays representing the conjugate relationship between the light source and the entrance pupil P of the objective lens are shown by solid lines, and the light rays representing the conjugate relationship between the blind B, reticle R, and wafer W are shown by broken lines. Further, in the above configuration, the illumination optical system is configured from the light source means 1 to the converging condenser lens 18.

Incidentally, a plan view of the patterned filter 16 and the fly's eye integrator 20 as seen from the incident light side is shown in FIG. 2A, and a side view thereof is shown in FIG. 2B. The lens surface 20a on the incident light side is made up of a combination of small lenses.
The rear focal point is approximately at the position of the exit light side lens surface 20b, and the front focal point of the exit light side lens surface 20b is located at the position of the input light side lens surface 20a. Therefore, the parallel light beam incident on the fly's eye integrator is focused near the exit light side lens surface of each small lens, and near the exit surface of the fly's eye integrator, a number of secondary A light source is formed. Outgoing light side lens surface 20b of each small lens
functions as a field lens for each secondary light source,
The entrance surface 20a of the fly's eye integrator 20 is formed to be conjugate with the blind B by the relay lenses L+ and Lx, and is substantially conjugate with the reticle R and the surface of the wafer W as the object to be illuminated by the condenser lens 1B.

Therefore, the light beams from a large number of secondary light sources formed near the exit surface of the fly-eye integrator 20 illuminate the reticle R as an object to be illuminated and the wafer W as an object to be illuminated, so that the wafer surface is overlapped. evenly illuminated.

As illustrated in FIG. 2A, the patterned filter 16 made of quartz glass as a parallel plane transparent member includes:
A circular light-shielding portion 31.32 is formed as a light-shielding member for shielding the central portion of the light beam incident on two of the many small lenses 21.22. For this reason,
The light flux that passes through the small lens that is affected by this light shielding part creates a circular low-illuminance area at the center of the object surface to be illuminated, and the uneven illuminance distribution (so-called hot spot) where the center area becomes higher due to flare is corrected. , uniform illuminance distribution can be achieved over the entire illuminated object surface. Light shielding part 30.
Reference numeral 31 is formed by vapor depositing metal such as chromium on a parallel plane transparent member.

Here, as shown in Fig. 3, if the number N of small lenses shielded by the light shielding member among the small lens groups constituting the fly's eye integrator increases, the illuminance on the wafer surface will decrease at the center of the exposure area. The degree of decline increases. Specifically, as mentioned above, the entrance surface of the fly's eye integrator is configured to be conjugate with the reticle and wafer surface, which are the object surfaces to be illuminated, so the entrance surface of each small lens making up the fly's eye integrator is conjugate with the reticle and the wafer surface. and the exposure area on the wafer surface, and by blocking the light beam at the center of the incident surface of each of these small lenses, it is possible to reduce the light intensity at the center on the reticle and wafer surface. and,
The more the number of small lenses that block the light beam at the center increases, the more the light intensity at the center can be reduced in the exposure area on the surface of the object to be illuminated.

Therefore, although the patterned filter 16 shown in FIG. 2A has a configuration in which light shielding members are provided in two small lenses, it is also possible to correct the illuminance distribution to a desired one by increasing the number of light shielding members. For this reason, in this embodiment, as shown in the plan view of FIG. 4, three patterned filters having different numbers of light shielding members are used - No. 1, No. 2. No. 3 is configured to be replaceable, and is configured to provide an appropriate illumination state depending on the replacement of the reticle or wafer.

The patterned filter 16 is as shown in the plan view of FIG. 4, and includes three patterned filters No. 1, No. 2, and 3, housed in a support body 16b that can be rotated by a drive motor M around a shaft 16a. It is composed of No.3.

Nol filter is Fly Eye Integrator 20
The center part of four of the plurality of reticle elements constituting the reticle is shielded from light, the No. 2 filter shields two of them, and the No.
The third filter does not have a light shielding member. FIG. 5 shows Nol + No2. FIG. 7 is a diagram showing correction characteristics of illuminance distribution by each of No. 3 filters. As shown in the figure, the Nol filter has the greatest correction effect,
The No. 3 filter has no correction effect, and the No. 2 filter has an intermediate correction effect. Since the illuminance distribution is rotationally symmetrical about the optical axis, the characteristic diagram of FIG. 5 shows the origin as the optical axis and the distance from the optical axis as the horizontal axis.

The same applies to the illuminance distribution explanatory diagram of FIG. 6, which will be described later.

In addition, all the light shielding parts necessary for the patterned filter are
It is desirable to form a metal such as chromium in a desired shape on a parallel plane transparent member such as quartz glass by vapor deposition. Although it is possible to apply a light-absorbing paint to a predetermined shape, the material must be able to sufficiently withstand the heat generated by light absorption.

Next, correction of the illuminance distribution in the projection exposure apparatus having such a configuration will be explained.

In the practical use of the above exposure apparatus, as mentioned above,
Flare light generated by reflection on each lens surface of the illumination optical system and projection optical system and reflection on the reticle R and wafer W surface may cause non-uniform illuminance called a hot spot. The conditions in which flare light is generated are determined by the lens configurations that make up the illumination optical system and the projection optical system, so the characteristics of the illuminance distribution, known as a hot spot, are largely determined by the configuration of the optical system. It has unique illuminance distribution characteristics determined by the configuration.

The intensity of the hot spot is determined mainly by the i3 pass rate of the reticle and the reflectance of the wafer.

Therefore, the flare rate F with respect to the amount of illumination light on the wafer surface is
F=kxT, xR.

It can be defined as Here, k is a constant corresponding to the unique illuminance distribution characteristic determined by the configuration of the optical system of the projection exposure apparatus, TI1 is the transmittance of the reticle, and R8 is the reflectance of the wafer.

Then, the reticle R is fully transparent with no pattern at all, and each blade of the blind is moved to illuminate the maximum exposed area, that is, the reticle has maximum transmittance. The flare rate F is maximum.

The state of the illuminance distribution is estimated by calculating this maximum flare rate F max in advance and calculating the ratio (F/F, □) to the flare rate F when performing exposure using a reticle with a desired pattern. can do. That is, as shown in FIG. 6, if the illuminance distribution on the wafer surface at the time of maximum flare rate F, 1 is expressed as curve a, then F/
When the value of F□8 is 0.6, it is a curve, and when it is 0.2, as shown by a curve C, the vertical axis of the figure is in a state of being reduced in accordance with the value of the ratio.

Then, the area between curves a and b is 1, and the songs NIAb and C
Let n be the slope between , and let ■ be the area below curve C,
The state of the illuminance distribution is roughly divided into these three states, and illuminance distribution correction means corresponding to these conditions are provided.

As this illuminance distribution correction means, the above-mentioned three patterned filters No. 1, No. 2. Use No.3.

The correction characteristics of the illuminance distribution by each filter are as shown in FIG. N
It is assumed that o2 has such a characteristic that the illuminance distribution corresponding to F/FoX=-0, 4 can be uniformly corrected. As a result, in the case of F/F□, -0°6 to 1.0 region ■, the flare rate ratio F/F□ can be corrected to ±20% or less by using the Nol patterned filter. In the case of region ■ where F/F, □ = 0.2 to 0.6, the flare rate ratio F/FoX can be corrected to below ±20% by using No. 2 patterned filter. . In the case of region (2) where F/F, . Here, since the unevenness of the illuminance distribution on the wafer surface due to the true spot that may generally occur is about a few percent or less in the center compared to the peripheral area, the flare rate ratio F/F due to the true spot is as described above. It is clear that if □8 is corrected to ±20% or less, the actual illuminance unevenness on the wafer surface is corrected to 2% or less, and the illuminance distribution is corrected to be extremely uniform.

Next, a method of correcting the illuminance distribution as described above will be explained. FIG. 7 is a flowchart showing a sequence related to correction of the illuminance distribution on the wafer surface using the patterned filter as described above.

First, a reticle to be used for exposure is loaded into a predetermined position of a projection exposure device (51), and the pre-measured transmittance T of the reticle is input (S2). Load the wafer coated with the resist (S3), and if the wafer is the first of a series of lofts (S4), input the pre-measured reflectance Rw of the wafer (S5), flare rate F and F/F, , calculate yo ($6). And F/F...
As mentioned above, the value of 8 is determined to be in one of the three regions with boundaries of 0.6 and 0.2 (571872),
It is determined whether or not the necessary illuminance distribution correction filter is installed in each area.S81°S82. 383
), replace with the necessary filter (S91, S9
2. 393).

Through such operations, the illuminance distribution on the wafer surface is appropriately corrected despite the presence of the real spot, and exposure is performed (S10). In this exposure, exposure of several tens of resists is sequentially repeated on one wafer at -M, and the wafer is transported by a stage, the exposure of one wafer is completed, and the exposure is performed from the exposure position, assuming that the wafer has been exposed. It is transported to a predetermined position outside the area (S11). For the first wafer in a series of wafer lofts, patterned filters Nof, No2+ are applied based on the calculations described above.
An appropriate one among No. 3 is used, and exposure is performed under the same conditions as the first wafer until the series of lots is completed (312).

If the exposure of one loft is completed and there is no need to replace the reticle, the exposure ends, and if the reticle is replaced and exposure is performed again (S13), the reticle is unloaded and another reticle is used for coding. (31), and the above operation is repeated.

In the above sequence, the flare rate and F/F, □
The calculation step (S6) to the step (571, 372) of determining the value of the flare rate into three regions are performed by the calculation means 2, and the step of determining whether a predetermined filter is arranged (S81, S82. 583
) and each filter replacement step (391, 392,
393) is performed by the control means 3.

In the above explanation, it is assumed that the reticle transmittance T7 and the wafer reflectance R11 are known in advance, and these values can be entered manually or saved from the predetermined storage means 4 when replacing the reticle and wafer. It is possible to read and input them automatically, but it is also possible to measure them just before exposure to ensure accuracy. It is also possible to provide a monitoring device for measuring the reticle l ratio and wafer reflectance in order to appropriately monitor whether there are any fluctuations in each value during exposure of a series of lofts.

Furthermore, in the above embodiment, three filters are used as patterned filters to perform three-stage correction, but as a configuration in which more filters can be replaced, correction can be made to a more uniform illuminance distribution by multi-stage correction. is possible. The method of replacing each filter is not limited to the turret type as in the above embodiments, but may also be configured as a sliding type. Furthermore, in the above embodiment, the flare rate ratio was calculated and corrected for the first wafer in one loft, but when changing the exposure area by moving the blind even within one lot. At that point, it is preferable to calculate the ratio of flare rates and perform optimal correction.

Below, a specific example of the structure for measuring the pass rate of a reticle and the reflectance of a wafer will be explained based on FIG. 8. In order to explain the apparatus for measuring the transmittance of the reticle and the reflectance of the wafer, FIG. 8 shows the configuration of each measuring device in the optical configuration shown in FIG. This is shown in addition.

First, the transmittance T of the reticle is defined as the amount of light irradiated on the wafer surface when a completely transparent reticle with no pattern is placed and the blind B is expanded to the maximum exposure area, and Irradiation on the wafer surface when a reticle with a pattern used for actual exposure (hereinafter referred to as the reticle in actual use) is placed and blind B is adjusted to the same size range as that during exposure of the reticle. It is expressed as a percentage of the amount of light. For this reason, the amount of irradiation light when irradiating the maximum exposure range with a completely transparent reticle,
The illuminance meter 50 placed on the wafer stage 40 is placed at the exposure position to measure the amount of irradiation light when the reticle in actual use is placed in the same illumination state as that at the time of exposure, and the measurement output in each case is calculated. The transmittance Tm of the reticle is calculated from the ratio.

If the light-receiving surface of the illuminance meter 50 is smaller than the exposure area, the illuminance meter 50 is moved within the exposure area by the wafer stage 40 and divided measurements are repeated at multiple locations, and the illuminance over the entire exposure area is determined by the sum of the illuminances. It can be easily measured by finding it as .

By the way, in the above-mentioned measurements, a completely transparent reticle without a pattern is required for each IF rate measurement of the actual reticle, but when a completely transparent reticle without a pattern is placed, The amount of light irradiated is
It does not change unless the amount of light supplied from the light source means changes. Therefore, if we set the irradiation light amount on the wafer surface when a completely transparent reticle is placed at a certain standardized light amount as an equipment constant, we can measure when a completely transparent reticle is placed. Without a doubt,
The reticle passing rate T7 can be determined. For this purpose, the amount of light supplied from the light source means is detected, for example, by a light amount detector 51 placed on the transmitted light path of the optical path bending mirror 17, and the measured value is normalized when a reticle for actual use is placed. It is necessary. That is, by measuring the amount of irradiated light when the reticle in actual use is placed and measuring the amount of light supplied from the light source means, the amount of light on the wafer with the reticle in actual use is determined by calculating the constant values on both sides. The reticle transmittance TR is determined from the ratio of this value to the amount of light irradiated on the wafer surface when a non-transparent particle is placed on the entire surface at a predetermined standardized light amount.

Note that if the exposure range of a reticle in actual use changes, the transmittance will differ even for the same reticle, so when changing the exposure range, it is necessary to remeasure the transmittance in the same way as above. preferable.

It is also possible to measure the reticle transmittance T immediately before exposure, but once the reticle pattern is determined, the transmittance will not change, so the exposure data for the reticle is shown in Figure 1. If it is stored in the storage means 4, it becomes unnecessary to repeat the measurement every time the reticle is replaced or every time the exposure range is changed by moving the blind, and throughput is not reduced.

Now, in order to accurately measure the reflectance R0 of a wafer, it is necessary to use the same wavelength as the exposure light, but since the resist is not sensitive to light, it is generally reflected by light of a wavelength other than the sensitive wavelength. It is necessary to measure the ratio and use or correct this value for conversion. For this purpose, for example, a reflectance measuring device is used which is provided in parallel with the projection objective L0 as shown in FIG. In this example, a light beam from a predetermined light source 60 that emits light with a wavelength that does not sensitize the resist is focused by a positive lens 61 on the incident surface of the fiber 62 and guided to the exit surface of the fiber 62. The light is guided through a mirror 65 to a measurement objective lens 66 and irradiated onto the wafer W. The reflected light from the wafer is focused by a measurement objective lens 66 and guided to a semi-transparent mirror 64 via a mirror 65, and the transmitted light of the semi-transparent Pi mirror 64 is focused onto a photoelectric conversion element 68 by a condensing lens 67.

The output of the photoelectric conversion element 68 when the base reflecting member 69 provided on the stage 40 is placed under the measurement objective lens, and when the wafer to be exposed is placed under the measurement objective lens 66 on the stage 40 photoelectric conversion element 68
The reflectance R8 of the wafer can be determined by the ratio to the output of .

Further, although the reflectance measuring apparatus described above is a method of measuring through a measurement objective lens different from the projection objective lens, so-called TTL measurement in which measurement is performed through the projection objective lens is also possible. To this end, a photoelectric conversion element 51 is arranged on the transmitted optical path of the optical path bending mirror 17 in the illumination optical system, and the reflected light from the wafer is detected through the projection objective lens L0, thereby reducing the reflectance of the wafer. It is possible to measure.

Note that the measurement of the reflectance of the wafer is not performed every time immediately before exposure, but the reflectance is generally determined once the wafer material and resist are specified, so it is necessary to measure the reflectance for each combination of wafer material and resist. It is desirable to have a configuration in which the reflectance is measured in advance, these values are stored in the storage means shown in Figure 1, and the flare rate is calculated by appropriately inputting these stored values. .

As described above, the transmittance of the reticle and the reflectance of the wafer can be determined, and the illuminance distribution can be accurately corrected according to the present invention.

By the way, in the description of the above embodiment, it was assumed that the characteristics of the illuminance distribution in a certain projection exposure apparatus are almost constant as long as the illumination optical system and the projection optical system are constant. Even if the illuminance distribution characteristics change as a result of changing the configuration of the projection optical system, it is possible to correct the illuminance distribution to make it uniform in the above configuration. That is, as shown in FIG. 9, the parallel plane member on which the light shielding member is formed and the fly's eye
As the distance between the integrator and the incident surface increases, it is possible to reduce the rate of decrease in illuminance on the surface of the object to be illuminated and widen the region of decrease. Therefore, by changing the distance between the incident surface of the fly-eye integrator and the parallel plane member on which the light shielding part is formed, it is possible to correct illuminance distributions with different characteristics and always maintain a uniform illuminance distribution. Become.

In addition, in the above embodiment, a parallel plane transmitting member provided with a desired number of light shielding members is arranged on the incident light side of the fly-eye integrator as illuminance distribution correction means, but the invention is not limited to this, and the characteristics shown in FIG. As shown in the curve, various ND filters with continuously changing concentrations are used to attenuate the light intensity at the center more than at the periphery. It is also possible to have a configuration in which they are replaced.

〔Effect of the invention〕

As described above, according to the present invention, by providing the transmittance of a projection original plate such as a reticle and the reflectance of an illuminated object such as a wafer, there is no need to directly measure the illuminance distribution on the surface of the illuminated object. It is possible to correct the uniformity of illuminance on the illuminated object plane. No matter what kind of projection original plate or object to be illuminated is used, it is possible to perform optimal illuminance distribution correction according to the reticle or wafer used, and always obtain a stable and highly uniform illuminance distribution. becomes.

[Brief explanation of the drawing]

FIG. 1 is an optical configuration diagram showing an embodiment of a projection exposure apparatus according to the present invention, and FIG. 2A is a position of a parallel plane transparent member having a light shielding member as illuminance distribution correction means and a fly's eye integrator. Figure 2B is a plan view showing the relationship, Figure 2B is a side view thereof, Figure 3 is an explanatory diagram of the change characteristics of illuminance distribution due to the parallel plane transparent member (illuminance distribution correction means), and Figure 4 is a diagram showing the patterned plate as illuminance distribution correction means. Top view of the filter,
Fig. 5 is a characteristic curve diagram of three patterned filters as illuminance distribution correction means, Fig. 6 is an explanatory diagram of illuminance unevenness on the illuminated object surface, and Fig. 7 is a flowchart for correcting the illuminance distribution. Figure 8 is an explanatory diagram of a device for measuring the i14 ratio of the reticle and the reflectance of the wafer, and Figure 9 is an explanatory diagram of the change characteristics of the illuminance distribution by the parallel plane transparent member (illuminance distribution correction means). be. [Explanation of symbols of main parts] 1... Light source means 16... Illuminance distribution correction means (parallel plane transparent member, patterned filter) R... Projection original plate (reticle) W... Illuminated object (wafer) ) Lo...Projection objective lens

Claims (1)

[Scope of Claims] 1) A projection exposure apparatus according to the present invention includes an illumination optical system for illuminating a projection original plate having a predetermined pattern, and a projection system for projecting an image of the pattern on the projection original plate onto an object to be illuminated. an optical system, an illuminance distribution correction means arranged in the illumination optical system for correcting the illuminance distribution on the illuminated object, and 1. A projection type exposure apparatus comprising: a calculation means for determining an illuminance distribution state on an illumination object; and a control means for converting a correction state by the illuminance distribution correction means in accordance with an output from the calculation means. 2) The illumination optical system includes a light source means that supplies illumination light of a substantially parallel light beam, and is arranged in the parallel light beam from the light source means to form a plurality of converging points to illuminate the surface of the object to be illuminated in a superimposed manner. a fly-eye integrator having a small lens group for illuminating the object surface; and a fly-eye integrator for making the incident surface of the fly-eye integrator substantially conjugate with the object surface to be illuminated, and guiding the light flux from the fly-eye integrator to the object surface to be illuminated. Claim 1 characterized in that it has a condenser lens.
Projection type exposure apparatus described in Section 2. 3) The illuminance distribution correction means has a light shielding part that partially blocks the light beam incident on at least one of the small lens groups of the fly's eye integrator, and has a light shielding part on the incident light side of the fly's eye integrator. 3. The projection exposure apparatus according to claim 2, wherein the projection exposure apparatus is a parallel plane transparent member arranged at a predetermined distance. 4) The illuminance distribution correction means includes a plurality of parallel plane transparent members each having a different number of light shielding members that block the light flux incident on the small lens group of the fly's eye integrator, and the control member 3. The projection exposure apparatus according to claim 2, wherein the projection exposure apparatus is configured so that the members can be replaced. 5) The illumination device according to claim 2, wherein the parallel plane transparent member of the illuminance distribution correction means is movable along the optical path of the parallel light beam.