JPH09171956A - Exposure system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and precisely evaluate image forming property of a projected image in a photosensitive material which is actually used, even when an exposure light is not regarded a monochromatic light. SOLUTION: A blended light of g-ray and h-ray is selected as an exposure light IL via a wavelength selection filter 31 from illuminating lights from a mercury lamp 1. At the time of exposure, the pattern of a reticle is projected and exposed on a plate 13 coated with a photoresist, via a projection optical system PL under the exposure light IL. At the time of measuring image forming property, a luminous flux of a projected image of an evaluation mark 25 on the reticle 11 is received by a photoelectric detector 22 via a reference pattern 17, and on the basis of a detection signal GA thereof, the best focusing position and distortion, etc., of the projected image are found. In this case, the spectral sensitivity of the detection signal SA to the exposure light IL matches the spectral sensitivity of the photoresist to the exposure light IL by a color correction filter 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used in a photolithography process for manufacturing, for example, a semiconductor element, a liquid crystal display element, an image pickup element (CCD, etc.), a thin film magnetic head, etc. Is suitable for use in an exposure apparatus that uses a light flux having a plurality of wavelengths or a predetermined bandwidth.

[0002]

2. Description of the Related Art Conventionally, in a photolithography process for manufacturing a semiconductor device or the like, a stepper method is used to transfer a pattern of a reticle as a mask onto a substrate such as a wafer or a glass plate coated with a photosensitive material. Projection exposure apparatus is used. Further, in order to cope with the increase in the area of the transfer pattern, the step-and-scan projection exposure in which the reticle and the substrate are scanned with respect to the projection optical system and the reticle pattern is sequentially transferred to each shot area on the substrate. The device is also being developed.

Recently, when manufacturing a liquid crystal display device such as a liquid crystal panel, a projection exposure apparatus of a stepper system or the like has come to be used in order to cope with the miniaturization of circuit patterns and the like. However, since, for example, one liquid crystal panel is considerably larger than one chip of a semiconductor element, in a projection exposure apparatus for manufacturing a liquid crystal display element, the magnification of the projection optical system is increased (equal magnification, further enlargement). Etc.)
When a mercury lamp is used to increase the power of the exposure light, bright lines with a plurality of wavelengths such as g-line (wavelength 436 nm) and h-line (wavelength 405 nm) may be used.

In response to the further miniaturization of patterns of semiconductor elements and the like, projection exposure apparatuses are required to transfer a reticle pattern image onto a substrate with higher resolution. Therefore, conventionally, the reticle pattern for evaluation is actually exposed through a projection optical system onto a substrate coated with photoresist, and the best focus position and linearity of the projected image (optical image) are determined based on the obtained resist image. A magnification error, distortion, etc. are measured, and the focus position of the substrate and the image forming characteristic of the projection optical system are corrected based on the measurement result.

However, it takes a lot of time for the measurement to actually measure the image forming characteristics of the projected image by performing the test print, and it is necessary to perform various steps for the measurement. There was a problem that it could not be easily measured at any time. Therefore, in order to deal with these problems, for example, in Japanese Patent Publication No. 2-27811, a projection image (optical image) by a projection optical system is directly detected via a photoelectric conversion element embedded in a stage on the substrate side. Therefore, a method of measuring the image formation characteristics of the projected image quickly and with high accuracy has been proposed.

[0006]

However, as described above, the best focus position, the linear magnification error, the distortion, etc. measured by the method of directly detecting the projection image (optical image) obtained through the projection optical system as described above. There is a disadvantage that the image forming characteristic does not always match the target projected image, that is, the image forming characteristic at the stage of the resist pattern obtained by developing the photoresist on the substrate. This is an inconvenience which is remarkable when a light flux having a plurality of wavelengths is used as the exposure light, for example, as in some projection exposure apparatuses for manufacturing liquid crystal display elements. explain.

FIG. 11A shows the shift of the focus position in the optical axis direction (axial chromatic aberration) in the light beams of different wavelengths, and FIG. 11B shows the lateral focus position of the light beams of different wavelengths. This is a representation of deviation (chromatic aberration of magnification). In FIG. 11A, assuming that the exposure light is composed of light fluxes of wavelengths λ ₁ and λ ₂ , the light flux 51 of wavelength λ ₁ and the light flux 52 of wavelength λ ₂ that have passed through the projection optical system PL are
Due to the axial chromatic aberration remaining in the projection optical system PL, the optical axis A
The image is formed with a shift of ΔZ in the direction along X. Therefore, if the illuminances of the light fluxes of wavelengths λ ₁ and λ ₂ are equal,
When the photoresists have the same sensitivity to the light fluxes of wavelengths λ ₁ and λ ₂ , the best focus position 53 in the resist pattern is the midpoint of the focus positions of the light fluxes 51 and 52, but at the photoresist wavelength λ ₁ . When the sensitivity is lower than the sensitivity at the wavelength λ ₂ , the best focus position 53 on the resist pattern is shifted to the focus position side of the light beam 52.

However, when the spectral sensitivity of the photoelectric conversion element for directly detecting the projected image is different from the spectral sensitivity of the photoresist, the best focus position measured by processing the detection signal of the photoelectric conversion element is the resist. It will be different from the best focus position in the pattern. for that reason,
Even if the focus position of the substrate is controlled based on the best focus position measured based on the detection signal of the photoelectric conversion element, a predetermined defocus remains.

Further, in FIG. 11B, the light flux 54 having the wavelength λ ₁ and the light flux 55 having the wavelength λ ₂ that have passed through the projection optical system PL are moved to the optical axis AX due to the lateral chromatic aberration remaining in the projection optical system PL. The image is shifted by ΔY in the vertical direction. Therefore, the best focus position 56 in the resist pattern is a position between the focus positions of the light beams 51 and 52, depending on the sensitivity of the photoresist to the light beams of the wavelengths λ ₁ and λ ₂ . Also in this case, when the spectral sensitivity of the photoelectric conversion element for directly detecting the projected image is different from the spectral sensitivity of the photoresist, based on the lateral shift amount of the projected image measured based on the detection signal of the photoelectric conversion element. Even if the magnification error and the distortion of the projection optical system are corrected by the above method, an error that cannot be corrected remains.

In view of the above, the present invention provides a projection image onto a photosensitive substrate such as a substrate coated with a photoresist easily and with high accuracy even when the exposure light cannot be regarded as monochromatic light. It is an object of the present invention to provide an exposure apparatus capable of evaluating the image forming characteristics of the.

[0011]

An exposure apparatus according to the present invention forms a transfer pattern with a wide band exposure light (IL) containing a plurality of wavelength components separated by a predetermined wavelength width or more from an exposure light source (1). Illumination optical system (1 to 1
10, 31), a projection optical system (PL) for projecting the pattern of the mask onto the photosensitive substrate (13) under the exposure light, and a substrate stage (14) for positioning the substrate (13). In an exposure apparatus having a reference member (16) formed on a substrate stage (14) on which a predetermined reference pattern (17) is formed, and a projection optical system (PL) under the exposure light. For example, the reference pattern (17; 17A) within the optical image of the pattern (25) on the predetermined mask (11) for evaluation projected on the reference member (16).
Photoelectric conversion element (22; 29) for receiving the light flux passing through
And a spectral sensitivity characteristic of the detection signal output from the photoelectric conversion element with respect to the exposure light, the photosensitive substrate (13)
And a sensitivity control means (32; 37) for adjusting the spectral sensitivity characteristic to the exposure light of the photoelectric conversion element (2.
2; 29), the position of the optical image of the pattern on the mask (11) is detected based on the detection signal.

According to the present invention, the photosensitive substrate (1
With respect to the spectral sensitivity characteristic of the exposure light of 3), the photoelectric conversion element (22; 2) is controlled by the sensitivity control means (32; 37).
By adjusting the spectral sensitivity characteristics of the detection signal of 9) to the exposure light so as to have similar characteristics, the best focus position of the projected image (optical image) measured based on the detection signal of the photoelectric conversion element, the linear The image forming characteristics such as magnification error or distortion are almost equal to the actual image forming characteristics of the projected image on the photosensitive substrate (13). That is, the actual image forming characteristics of the projected image on the photosensitive substrate (13) can be evaluated with high accuracy by an easy method of detecting an optical image.

In this case, an example of the sensitivity control means is a color correction member (32) arranged on the optical path of the exposure light from the exposure light source (1) to the photoelectric conversion element (22),
At this time, the product of the spectral attenuation factor (FIG. 6A) of the color correction member (32) for the exposure light and the spectral sensitivity characteristic (FIG. 5) of the photoelectric conversion element (22) for the exposure light (FIG. 6).
(B)) is set to be substantially proportional to the spectral sensitivity characteristic (FIG. 4) of the photosensitive substrate (13) with respect to the exposure light. As a result, the spectral sensitivity characteristic of the detection signal of the photoelectric conversion element (22) with respect to the exposure light becomes proportional to the spectral sensitivity characteristic of the photosensitive substrate (13) with respect to the exposure light (similar shape).

Further, it is desirable that the spectral attenuation factor of the color correction member (32) with respect to the exposure light be variable according to the spectral sensitivity characteristic of the photosensitive substrate to be exposed. This makes it possible to evaluate the imaging characteristics of the projected image on each photoresist with high accuracy when various photoresists are used. In these cases, the predetermined wavelength width of the exposure light is 20 nm as an example. In this way, when the predetermined wavelength width is 20 nm or more,
For example, a plurality of bright lines selected from the bright line group consisting of i-line (wavelength 365 nm), h-line (wavelength 405 nm), and g-line (wavelength 436 nm) of a mercury lamp are used as exposure light.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of an exposure apparatus according to the present invention will be described below with reference to FIGS.
In this example, the present invention is applied to a stepper type projection exposure apparatus for manufacturing a liquid crystal display element. FIG. 1 shows a schematic configuration of a projection exposure apparatus of this example. In FIG. 1, the illumination light from an ultrahigh pressure mercury lamp 1 as a light source for exposure is
After being condensed by the elliptical mirror 2 and reflected by the mirror 3, the light enters the wavelength selection filter 31 through the input lens 4. Then, the exposure light IL composed of the g-line of wavelength 436 nm and the h-line of wavelength 405 nm selected by the wavelength selection filter 31 from the illumination light enters the fly-eye lens 5. The exposure light IL has a wavelength of 365 nm i
Line and h line mixed light, i line and g line mixed light, or i
A mixed light of lines, h lines, and g lines can be used. Further, as the exposure light, bright lines having a plurality of wavelengths from other discharge lamps, broadband illumination light, or laser light having a plurality of wavelengths such as excimer laser light may be used.

At the time of exposure, the exposure light IL emitted from the fly-eye lens 5 is a first relay lens 6, a variable field stop (reticle blind) 7, a second relay lens 8, an optical path bending mirror 9, and a condenser lens. Then, the pattern area on the lower surface (pattern forming surface) of the reticle held on the reticle stage 12 is illuminated with a uniform illuminance distribution. A reticle 11 for evaluation, which will be described later, is arranged on the reticle stage 12 in FIG. The arrangement surface of the variable field diaphragm 7 is conjugate with the pattern formation surface of the reticle, and the variable field diaphragm 7 sets the illumination area on the reticle. Under the exposure light IL, the device pattern of the reticle is projected and exposed to one shot area on the plate 13 at equal magnification, for example, via the projection optical system PL which is telecentric on both sides (or one side on the wafer side).
The plate 13 is made of, for example, a glass substrate, and a photoresist is applied on the plate 13. In the following description, the Z axis is taken parallel to the optical axis AX of the projection optical system PL, the X axis is taken parallel to the plane of FIG. 1 in the plane perpendicular to the Z axis, and the Y axis is taken perpendicular to the plane of FIG. To do.

The plate 13 is held on a plate stage 14, and the plate stage 14 positions the plate 13 in the X and Y directions by a step-and-repeat method, and also in the Z direction within a predetermined range.
Perform positioning. The X-direction and Y-direction coordinates of the plate stage 14 are measured by an X-axis laser interferometer 15X and a Y-axis laser interferometer (not shown), and the measured X-coordinates MD and Y-coordinates are the operation of the entire apparatus. Is supplied to the main control system 24 that controls the control of the. Laser interferometer 1
The "stage coordinate system" is a coordinate system that is determined based on measured values such as 5X.

Although not shown, a slit image is obliquely projected on the surface of the plate 13 or the like, the reflected light from the surface is condensed, and the slit image is re-imaged. A focus position detection system for detecting the focus position (position in the Z direction) on the surface of the plate 13 or the like is also arranged. Then, based on the detection result of the focus position detection system, normally, the Z of the plate stage 14 is adjusted so that the surface of the plate 13 coincides with the image plane of the projection optical system PL.
The directional position is controlled.

Further, a lens controller LC is connected to the projection optical system PL, and the lens controller LC finely moves a predetermined lens in the projection optical system PL in a direction parallel to the optical axis AX or moves the lens to the optical axis AX. By tilting or tilting with respect to a vertical plane, it is possible to change the linear magnification of the projection optical system PL and the imaging characteristics such as predetermined distortion characteristics. In the present example, the main control system 24 forms an image of the projection optical system PL via the lens controller LC based on the image forming characteristics measured by the projection image (optical image) through the projection optical system PL as described later. The characteristics of the plate 1 can be controlled or the plate stage 14 can be driven.
Correct the focus position of 3.

In this example, a light-transmissive reference member 16 made of a glass substrate is fixed in the vicinity of the plate 13 on the plate stage 14 and is held so as to have the same height as the surface of the plate 13. A reference pattern 17 is formed on the surface of the member 16. 2B shows an example of the reference pattern 17, and as shown in FIG. 2B, the reference pattern 17 is formed by a cross-shaped opening pattern in the light shielding film on the surface of the reference member 16. .

When measuring the image forming characteristics of the projected image by the projection optical system PL, the reticle 11 for evaluation is loaded on the reticle stage 12 in FIG. This reticle 11
In the pattern area, the evaluation marks 25 are arranged at a predetermined pitch in the X and Y directions. FIG. 2A shows a projected image 2 of the evaluation mark 25 by the projection optical system PL.
5W, and as shown in FIG. 2A, the projected image 25W has, for example, a cross-shaped dark pattern in the bright portion. Then, in the best focus state, the projected image 2
The size of the evaluation mark 25 is set so that 5 W has the same size as the reference pattern 17. In this case, when the reference pattern 17 is scanned in the X direction or the Y direction and the reference pattern 17 matches the projected image 25W of the evaluation mark 25 in the X direction or the Y direction, the amount of light passing through the reference pattern 17 Is the smallest. Thereby, the position of the projected image 25W can be detected.

Further, while changing the position of the plate stage 14 in the Z direction, the projected image 25W is X-rayed by the reference pattern 17.
Direction and the Y direction, the contrast of the light amount change corresponding to the projected image 25W for each scan is the reference pattern 17
Is the largest when is in the best focus position.
By utilizing this, the best focus position of the projected image 25W can be detected.

Returning to FIG. 1, inside the plate stage 14 at the bottom of the reference member 16, there is arranged a relay optical system for receiving the light flux passing through the reference pattern 17 from the projection optical system PL side. That is, in the relay optical system, the light flux that has passed through the reference pattern 17 of the reference member 16 is reflected by the mirror 19, then passes through the condenser lens 20 and the color correction filter 32, and then passes through a silicon photo diode as a photoelectric conversion element. The light enters the light receiving surface of the photoelectric detector 22 formed of a diode. The color correction filter 32 is an optical filter plate in which the ratio of the transmittance of the g-line and the h-line to the luminous flux is set to a predetermined value. Then, the detection signal SA obtained by photoelectrically converting the incident light by the photoelectric detector 22 is supplied to the main control system 24.

In this case, the numerical aperture of the relay optical system including the mirror 19, the condenser lens 20, and the color correction filter 32 is the information of the projected image (optical image) of the evaluation pattern 25 of the reticle 11 by the projection optical system PL. It is desirable to set so that all can be detected. That is, it is desirable that the numerical aperture of the relay optical system be at least larger than the numerical aperture of the projection optical system PL.

Next, the spectral transmittance of the color correction filter 32 used in this example will be described. First, assuming that the photoresist used in this example is a so-called g-line resist, the spectral sensitivity of the g-line resist is obtained. FIG. 3 shows g
The transmittance of the line resist is shown, and the horizontal axis of FIG. 3 is the wavelength λ.
[Nm], the vertical axis is the transmittance, the solid curve 33 shows the distribution of the transmittance with respect to the wavelength at the start of exposure (spectral transmittance), and the chain double-dashed curve 34 shows the value after sufficient exposure. The spectral transmittance is shown. Further, on the horizontal axis, the wavelength λ _i indicates the i-line wavelength 365 nm, the wavelength λ _h indicates the h-line wavelength 405 nm, and the wavelength λ _g indicates the g-line wavelength 436 nm. In this case, it is considered that the difference between the curve 34 and the curve 33 represents the ratio of the light flux absorbed by the photoresist, that is, the relative sensitivity which is the relative value of the degree of photosensitivity per unit incident energy with respect to the photoresist. Therefore, a light having a wavelength having a lower relative sensitivity requires a larger exposure amount to expose the photoresist.

A curve 35 in FIG. 4 shows the relative sensitivity of the g-line resist obtained by subtracting the curve 33 from the curve 34 in FIG. 3. The horizontal axis in FIG. 4 is the wavelength λ [nm], and the vertical axis is the relative sensitivity. It is P1. From the curve 35 of FIG. 4, the relative sensitivity P1 _i at the wavelength λ _i , the relative sensitivity P1 _h at the wavelength λ _h (= 0.62),
The relative sensitivity P1 _g (= 0.48) at the wavelength λ _g is obtained.

Next, in this example, a silicon photodiode is used as the photoelectric detector 22, and the spectral sensitivity of the silicon photodiode is as shown by the curve 36 in FIG. Figure horizontal axis 5 Wavelength [nm], the vertical axis represents the relative sensitivity P2 is a relative value of the photoelectric conversion signal per unit incident energy, from the curve 36 in FIG. 5, the relative sensitivity P2 _i of the wavelength lambda _i, Relative sensitivity at wavelength λ _h P2 _h (= 0.3
4), the relative sensitivity P2 _g (= 0.42) at the wavelength λ _g is obtained.

Therefore, in FIG. 1, the wavelengths λ _h and λ in the reference member 16, the mirror 19 and the condenser lens 20 are set.
Assuming that the transmittance or the reflectance for the light flux of _g is equal, the transmittances for the light fluxes of wavelengths λ _h and λ _{g in} the color correction filter 32 are T2 _h and T2 _g , respectively. In this case, the spectral sensitivity for the light flux with wavelength lambda _h and lambda _g of the detection signal SA output from the photoelectric detector 22 (the value of the detection signal per unit incident energy), the wavelength lambda _h of the photoresist on the plate 13 and In order to match the spectral sensitivity with respect to the luminous flux of λ _g , that is, to obtain a similar shape, the value obtained by multiplying the spectral sensitivity of the silicon photodiode of FIG. 5 by the spectral transmittance of the color correction filter 32 is the g line of FIG. It should be similar to the spectral sensitivity of the resist. The conditions for that are as follows.

P1 _h : P1 _g = P2 _h T2 _h : P2 _g T2 _g (1) By substituting the numerical values of FIGS. 4 and 5, the transmittances T2 _h and T2 _{g of the} color correction filter 32 can be obtained. The ratio of is as follows. T2 _h : T2 _g = P1 _h P2 _g : P1 _g P2 _h ≈0.26: 0.16 (2)

Therefore, when the transmittance T2 _g at the wavelength λ _g in the color correction filter 32 is set to 0.4, for example,
(2) the transmittance T2 _h at a wavelength lambda _h from Equation is about 0.65. FIG. 6A shows the spectral transmittance of the color correction filter 32 thus determined. Then, by multiplying the relative sensitivity P2 of FIG. 5 by the transmittance T2 of FIG. 6A, the total relative sensitivity PH representing the relative sensitivity with respect to the wavelength of the detection signal SA output from the photoelectric detector 22 of FIG. 1 is obtained. To be

FIG. 6B shows the total relative sensitivity PH. In this FIG. 6B, the horizontal axis shows the wavelength [nm], the vertical axis shows the total relative sensitivity PH, and the total relative sensitivity at the wavelength λ _h . and PH _h, combined relative sensitivity PH _g at a wavelength λ _g
And the value of the ratio of the relative sensitivity P1 _{h at} the wavelength λ _h of the g-line resist in FIG. 4 and the value of the relative sensitivity P1 _g at the wavelength λ _g are substantially equal. Therefore, the spectral sensitivity of the detection signal SA of the photoelectric detector 22 of the present example to the exposure light IL composed of the h line and the g line is similar to the spectral sensitivity of the photoresist on the plate 13 to the exposure light IL.

Next, the reference pattern 1 on the reference member 16
An example of the operation of actually measuring the image forming characteristics of the projected image (optical image) through the projection optical system PL by using 7 and the photoelectric detector 22 will be described. In this case, as described above, FIG.
The reticle 11 in which the evaluation marks 25 are formed on the reticle stage 12 at predetermined pitches in the X and Y directions.
Is mounted and the plate stage 14 is driven to drive the reference member 1
The reference pattern 17 of No. 6 is scanned in the X and Y directions within the exposure field of the projection optical system PL. For example, when the projected image of the evaluation mark 25 and the reference mark 17 match in the X direction or the Y direction, the level of the detection signal SA becomes the minimum, so the main control system 14 determines that the level of the detection signal SA is the minimum. The value of the coordinate (stage coordinate system) of the plate stage 14 at that time is the X coordinate of the projected image of the evaluation mark 25,
Alternatively, the Y coordinate is used. Then, the X-coordinate and the Y-coordinate of the projected image are obtained for each of the plurality of evaluation marks, and these are compared with the target position when the projection optical system PL has no aberrations to obtain the projected image of the projected optical system PL. The linear magnification error and distortion of are measured.

Further, while the plate stage 14 is driven in the Z direction and the focus position on the surface of the reference member 16 is changed by a predetermined step, the reference pattern 17 is set in the X direction or the image of the evaluation mark. The contrast of the change in the detection signal SA obtained by scanning in the Y direction is calculated,
The focus position when this contrast becomes the highest can be obtained as the best focus position. In these cases, the spectral sensitivity of the detection signal SA of the photoelectric detector 22 of this example to the exposure light IL is similar to the spectral sensitivity of the photoresist on the plate 13 to the exposure light. The image forming characteristics such as the best focus position, the linear magnification error, and the distortion obtained as described above are substantially equal to the image forming characteristics at the stage of the resist pattern obtained by actually developing the photoresist on the plate 13. Therefore, according to this example, even when the exposure light IL having a plurality of wavelengths is used, the photoresist actually used can be easily and accurately used by the method of linearly detecting the projection image (optical image) by the projection optical system PL. Can be evaluated.

After that, the plate stage 14 is driven to adjust the focus position of the plate 13 to be exposed according to the best focus position obtained based on the detection signal SA of the photoelectric detector 22, and based on the detection signal SA. By correcting the image forming characteristic of the projection optical system PL via the lens controller LC according to the obtained linear magnification error and distortion, a high resolution pattern image is transferred to the photoresist layer on the plate 13 at an accurate position. it can.

Next, another example of the embodiment of the exposure apparatus according to the present invention will be described with reference to FIGS. 7 and 8. In this example, the present invention is applied when an image sensor is used as a photoelectric conversion element. In FIG. 7, parts corresponding to those in FIG. 1 are denoted by the same reference numerals and detailed description thereof will be omitted.
FIG. 7 shows a main part of the projection exposure apparatus of this example. In FIG. 7, as the exposure light IL, a mixed light of h line and g line of a mercury lamp is used. Then, in the vicinity of the plate 13 on the plate stage 14, a light-transmissive reference member 16 is provided.
A is fixed, and a reference mark 17A having a cross-shaped light-shielding pattern is formed on the surface of the reference member 16A as an example. The reference member 16A is in the exposure field of the projection optical system PL, and the evaluation mark 2 of the reticle 11 is present.
The exposure light IL transmitted from the projection optical system PL side through the reference member 16A in the state where the projected image of 5 is projected on the reference member 16A is transmitted from the two-dimensional CCD as a photoelectric conversion element via the relay optical system 26. On the image pickup surface of the image pickup element 29
The image of the reference pattern 17A on the reference member 16A and the projected image of the evaluation mark 25 are formed in an overlapping manner. The relay optical system 26 of this example is a magnifying optical system in order to increase the detection resolution, and as a result, the evaluation mark has the same resolution and accuracy as the method of scanning the photoelectric detector 22 as shown in FIG. The position and contrast of the 25 projected images can be detected.

That is, in the relay optical system 26, the exposure light IL that has passed through the reference member 16A reaches the color correction filter 37 via the mirror 19, the first relay lens 27A, and the aperture stop 28. The color correction filter 37 is an optical filter plate in which the ratio of the transmittance of the g-ray and the h-ray to the luminous flux is set to a predetermined value. The light flux that has passed through the color correction filter 37 passes through the second relay lens 27B and then passes through the image sensor 2
An enlarged image of the pattern on the reference member 16A and the projected image is formed on the image pickup surface of No. 9. Then, the image pickup signal SB from the image pickup device 29 is supplied to the main control system 24, and the main control system 24 processes the image pickup signal SB to detect the positional deviation amount of the projected image of the evaluation mark 25 with respect to the reference pattern 17A. Then
The position of the projected image of the evaluation mark 25 is obtained by adding this positional deviation amount to the coordinates of the plate stage 14 (coordinates of the stage coordinate system). Furthermore, the main control system 2
In 4, the contrast of the image pickup signal SB is evaluated as needed. Other configurations are the same as those in the example of FIG.

Next, the color correction filter used in this example
The spectral transmittance at 37 will be described. First, in this example
The photoresist used also has a relative spectral sensitivity characteristic.
It is assumed that the resist is a g-line resist represented by the curve 35 in FIG.
Further, the image pickup device 29 used in this example is configured.
The spectral sensitivity of the CCD is as shown by the curve 38 in FIG.
You. The horizontal axis of FIG. 8 is the wavelength [nm], and the vertical axis is the unit of each pixel.
Relative sense, which is the relative value of the imaging signal per incident energy
Showing the degree P3, and from the curve 38 in FIG._iRelative in
Sensitivity P3_i, Wavelength λ_hRelative sensitivity at P3 _h(= 0.5
5), wavelength λ_gRelative sensitivity at P3_g(= 0.90) found
Can be

Therefore, assuming that the reference member 16A shown in FIG. 7 and the optical members other than the color correction filter 37 in the relay optical system 26 have the same transmittance or reflectance with respect to the light fluxes of the wavelengths λ _h and λ _g , the color correction is performed. The transmittance of the filter 37 for the light beams of wavelengths λ _h and λ _g is T3 _h , respectively.
And T3 _g . In this case, the spectral sensitivity (the value of the image pickup signal per unit incident energy) of the image pickup signal SA outputted from the image pickup device 29 with respect to the light flux of the wavelengths λ _h and λ _g
Are the wavelengths λ _h and λ of the photoresist on the plate 13.
_In order to match the spectral sensitivity with respect to the light flux of _g , that is, to obtain a similar shape, the value obtained by multiplying the spectral sensitivity of the CCD in FIG. 8 by the spectral transmittance of the color correction filter 37 is the spectral distribution of the g-line resist in FIG. It should be similar to sensitivity. The conditions for that are as follows.

P1 _h : P1 _g = P3 _h T3 _h : P3 _g T3 _g (3) By substituting the numerical values shown in FIGS. 4 and 8, the transmittances T3 _h and T3 _{g of the} color correction filter 37 can be obtained. The ratio of is as follows. T3 _h : T3 _g = P1 _h P3 _g : P1 _g P3 _h ≈0.56: 0.26 (4)

Therefore, when the transmittance T3 _g at the wavelength λ _g in the color correction filter 37 is set to 0.4, for example,
(4) the transmittance T3 _h at a wavelength lambda _h from Equation is about 0.86. FIG. 9A shows the spectral transmittance of the color correction filter 37 thus determined. Then, by multiplying the relative sensitivity P3 of FIG. 8 by the transmittance T3 of FIG. 9A, the image pickup signal S output from the image pickup device 29 of FIG.
An overall relative sensitivity PI indicating the relative sensitivity to the wavelength of B is obtained.

FIG. 9B shows the total relative sensitivity PI.
Then, in FIG. 9B, the wavelength λ _hGeneral phase in
Sensitivity PI_hAnd the wavelength λ_gRelative sensitivity PI in_g
The value of the ratio is the wavelength λ of the g-line resist in FIG._hIn
Relative sensitivity P1_hAnd the wavelength λ_gRelative sensitivity P1_gWhen
It is almost equal to the ratio value of. Therefore, the imaging of this example
Exposure light composed of h line and g line of the image pickup signal SB of the element 29
The spectral sensitivity to IL is determined by the photoresist on the plate 13.
Stroke sensitivity is similar to the exposure light IL.
You.

Next, in FIG. 7, by using the reference pattern 17A on the reference member 16A, the image pickup device 29, etc., the image forming characteristics of the projected image (optical image) actually transmitted through the projection optical system PL are measured. An example of the operation will be described. In this case, the evaluation mark 25 is X-marked on the reticle stage 12 in FIG.
1 formed in a predetermined pitch in the Y direction and the Y direction
1 is mounted, the plate stage 14 is driven, and the reference pattern 17A of the reference member 16A is sequentially positioned near the formation position of the projected image of each evaluation mark. In that state, the main control system 24 processes the image pickup signal SB from the image pickup device 29 to obtain the X coordinate and the Y coordinate of the projected image of the evaluation mark. Then, by comparing the positions of the projected images of the plurality of evaluation marks with the target position when the projection optical system PL has no aberration, the linear magnification error of the projected image of the projection optical system PL,
And the distortion is measured.

Further, in a state where the focus position on the surface of the reference member 16A is changed by a predetermined step, the image of the evaluation mark and the reference pattern 17A substantially match each other, and a portion corresponding to the image of the evaluation mark. Image pickup signal S of
The contrast of B is obtained, and the focus position when this contrast becomes the highest is obtained as the best focus position. In these cases, the image pickup device 29 of the present example
Since the spectral sensitivity of the image pickup signal SB to the exposure light IL is similar to the spectral sensitivity of the photoresist on the plate 13 to the exposure light, the best focus position determined based on the image pickup signal SB, the linear magnification error, and The image forming characteristics such as distortion are substantially equal to the image forming characteristics at the stage of the resist pattern obtained by actually developing the photoresist on the plate 13. Therefore, according to this example as well, when the exposure light IL having a plurality of wavelengths is used, the photoresist actually used can be easily and highly accurately used by the method of linearly detecting the projection image (optical image) by the projection optical system PL. Can be evaluated.

Next, for example, in the projection exposure apparatus of FIG. 1, a plurality of color correction filters similar to the color correction filter 32 but different in spectral transmittance may be selected. FIG. 10A shows an example of the color correction filter selection mechanism. In FIG. 10A, for example, six color correction filters having different spectral transmittances are fixed to the side surface of the rotary plate 39. ing. In FIG. 10A, only two of the color correction filters 32A and 32B among them appear, and by rotating the rotary plate 39 via the drive motor 40, the six color correction filters are A desired color correction filter can be arranged in the optical path of the exposure light IL (for example, immediately before the photoelectric detector 22 in FIG. 1).

The spectral transmittances of the six color correction filters are the six types of frequently used photoresists applied on the plate to be exposed in the projection exposure apparatus of FIG. The spectral sensitivity of the detection signal SA of the photoelectric detector 22 of FIG. 1 is set to match the spectral sensitivity of the photoresist. In this case, the rotating plate 39 is automatically rotated according to the photoresist used, and the corresponding color correction filter is set, so that even if the photoresist is replaced, the corresponding image is accurately formed. Characteristic can be measured. Instead of automatically switching a plurality of color correction filters, the color correction filters may be replaced corresponding to the photoresist, for example, by a manual switching method.

Further, for example, in the projection exposure apparatus of FIG. 1, instead of the color correction filter 32, an optical filter plate that transmits only the g-line and an optical filter plate that transmits only the h-line are arranged, respectively. The lateral shift amount of the projected image of the evaluation mark and the best focus position may be measured. By obtaining the difference between these measurement results, the axial chromatic aberration and the lateral chromatic aberration remaining in the projection optical system PL can be measured, and the projection optical system PL is based on this measurement result.
The aberration can be adjusted.

Further, for example, the color correction filter 32 shown in FIG.
Instead of, a pair of wedge-shaped color absorption filters may be used in combination. FIG. 10B shows a color correction filter in which such a pair of wedge-shaped color absorption filters 41A and 41B are arranged so that their one surfaces are parallel to each other.
0 (b), one of the color absorption filters 41A has a transmittance characteristic of absorbing only the g-line with a predetermined transmittance and allowing the h-line to pass through as it is, and the other color absorption filter 41B.
On the contrary, it has a transmittance characteristic that only the h-line is absorbed with a predetermined transmittance and the g-line is transmitted as it is. Further, in this example, the other color absorption filter 41B is connected via the drive unit 42,
It is configured so that it can move in the direction perpendicular to the optical axis of the exposure light IL.

In the example of FIG. 1, since the exposure light IL is incident on the light receiving portion of one photoelectric detector 22 as a whole, the exposure light IL shown in FIG.
The transmittances for the g-line and the h-line by the color correction filter of (b) are respectively the color absorption filter 4 in the exposure light IL.
It may be considered to be proportional to the volume of 1A or 41B. Therefore, by shifting the other color absorption filter 41B with respect to the exposure light IL, the value of the ratio of the transmittance of the exposure light IL to the g-line and the h-line can be set to a desired value. This FIG.
Since the spectral transmittance can be adjusted according to the photoresist used by using the color correction filter of (b), the spectral sensitivity of the detection signal of the photoelectric detector 22 can be obtained no matter what photoresist is used. Can be matched to the spectral sensitivity of the photoresist.

Further, instead of the color correction filter 32 in the projection exposure apparatus of FIG. 1, for example, a minute g-line filter that passes only g-line and a minute h-line filter that passes only h-line are provided. You may use the color correction filter of the structure which combined the matrix-shaped color filter arrange | positioned at the grid | lattice form, and the liquid crystal shutter which opens and closes independently the light flux which passes each area | region of a grid | lattice. In this case, by controlling the value of the ratio between the number of g-line filters in the open state and the number of h-line filters in the open state via the liquid crystal shutter, the transmission for the g-line and the h-line can be easily performed. The ratio value can be set to a desired value.

Note that, for example, in FIG. 1, the color correction filter 32 is arranged at any position on the optical path of the exposure light IL between the light source for exposure (super high pressure mercury lamp 1) and the photoelectric detector 22. May be. Similarly, in FIG. 7, the color correction filter 37 may be arranged at any position on the optical path of the exposure light IL between the light source for exposure and the image pickup device 29.

Further, in the above-mentioned embodiment, the reference marks 17, 17A made of the opening pattern or the light-shielding pattern.
However, a reference mark may be formed from a reflection pattern formed in a non-reflective film, and the illumination light reflected by the reference mark may be received. Further, in the above-described embodiment, the exposure light IL having a plurality of wavelengths is used. However, even when a light flux having a single wavelength such as an i-line is used as the exposure light, leakage light having a different wavelength is used as the photoresist. In such a case, the color correction filter of the present invention can be used to accurately evaluate the imaging characteristics of the projected image on the photoresist even by the method of detecting the projected image.

Further, it is clear that the projection exposure apparatus according to the present invention can be widely used not only for liquid crystal display elements but also for manufacturing semiconductor elements and the like. As described above, the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the gist of the present invention.

[0053]

According to the exposure apparatus of the present invention, sensitivity control means for adjusting the spectral sensitivity characteristic of the detection signal from the photoelectric conversion element to the exposure light to the spectral sensitivity characteristic of the photosensitive substrate to the exposure light is provided. Therefore, even if the exposure light cannot be regarded as monochromatic light, the imaging characteristics of the projected image on the photosensitive substrate such as the substrate coated with the photoresist can be evaluated easily and accurately. There are advantages.

In this case, the sensitivity control means is a color correction member arranged on the optical path of the exposure light from the exposure light source to the photoelectric conversion element, and the spectral attenuation rate of the color correction member with respect to the exposure light and its If the product of the photoelectric conversion element's spectral sensitivity characteristic to the exposure light is substantially proportional to the photosensitive substrate's spectral sensitivity characteristic to the exposure light, the photoelectric conversion element can be converted into a simple structure from the photoelectric conversion element. It is possible to match the spectral sensitivity characteristic of the detection signal with respect to the exposure light with the spectral sensitivity characteristic of the photosensitive substrate with respect to the exposure light.

When the spectral attenuation factor of the color correction member with respect to the exposure light is variable according to the spectral sensitivity characteristic of the photosensitive substrate to be exposed, for example, when the type of photoresist is changed. However, there is an advantage that the imaging characteristics of the projected image when the changed photoresist is used can be accurately evaluated easily. Further, when the predetermined wavelength width of the exposure light is 20 nm, a case where a plurality of bright lines selected from, for example, g-line, h-line and i-line from a mercury lamp are used as the exposure light is included. The present invention is particularly effective.

[Brief description of the drawings]

FIG. 1 is a partially cutaway schematic configuration view showing a projection exposure apparatus as an example of an embodiment of the present invention.

2A is an enlarged plan view showing an example of a projected image of the evaluation mark 25 in FIG. 1, and FIG. 2B is an enlarged plan view showing an example of a reference pattern 17 on the reference member 16 in FIG. .

FIG. 3 is a characteristic diagram showing a change in transmittance due to exposure of a photoresist used in the embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a relative value (relative sensitivity) of the spectral sensitivity of the photoresist obtained from the change in transmittance shown in FIG.

5 is a photoelectric detector 2 used in the projection exposure apparatus of FIG.
3 is a characteristic diagram showing a relative value (relative sensitivity) of the spectral sensitivity of the silicon photodiode that constitutes No. 2. FIG.

6A is a diagram showing a spectral transmittance of a color correction filter 32 used in the projection exposure apparatus of FIG. 1, and FIG. 6B is a diagram of FIG.
It is a figure which shows the relative value (total relative sensitivity) of the total spectral sensitivity of the detection signal SA output from the photoelectric detector 22 of this projection exposure apparatus.

FIG. 7 is a partially cutaway schematic configuration view showing a projection exposure apparatus as another example of the embodiment of the present invention.

8 is an image pickup device 29 used in the projection exposure apparatus of FIG.
FIG. 6 is a characteristic diagram showing a relative value (relative sensitivity) of the spectral sensitivity of the CCD constituting the above.

9A is a diagram showing a spectral transmittance of a color correction filter 37 used in the projection exposure apparatus of FIG. 7, and FIG. 9B is a diagram showing FIG.
6 is a diagram showing a relative value (total relative sensitivity) of the total spectral sensitivity of the image pickup signal SB output from the image pickup device 29 of the projection exposure apparatus of FIG.

FIG. 10A is a cross-sectional view showing a main part of a modified example in which a plurality of color correction filters are switchably arranged, and FIG. 10B is a color correction composed of a pair of wedge-shaped color absorption filters. It is a block diagram which shows the filter for.

11A is an optical path diagram showing axial chromatic aberration, and FIG. 11B is an optical path diagram showing lateral chromatic aberration.

[Explanation of symbols]

 1 Ultra-high pressure mercury lamp 11 Reticle PL Projection optical system LC lens controller 13 Plate 14 Plate stage 15X Laser interferometer 16, 16A Reference member 17, 17A Reference pattern 22 Photoelectric detector 29 Image sensor 31 Wavelength selection filter 32, 37 For color correction filter

Claims (4)

[Claims] 1. An illumination optical system for illuminating a mask on which a transfer pattern is formed with a wide band exposure light including a plurality of wavelength components separated by a predetermined wavelength width or more from an exposure light source, and the source of the exposure light. In an exposure apparatus having a projection optical system for projecting the mask pattern onto a photosensitive substrate and a substrate stage for positioning the substrate, a reference having a predetermined reference pattern formed on the substrate stage. A member and a photoelectric conversion element that receives a light flux that has passed through the reference pattern in an optical image of a pattern on a predetermined mask that is projected onto the reference member through the projection optical system under the exposure light. And sensitivity control means for matching the spectral sensitivity characteristic of the detection signal output from the photoelectric conversion element with respect to the exposure light to the spectral sensitivity characteristic of the photosensitive substrate with respect to the exposure light,
An exposure apparatus, comprising: an optical image position of a pattern on the predetermined mask based on a detection signal of the photoelectric conversion element whose spectral sensitivity characteristic is controlled by the sensitivity control means. 2. The exposure apparatus according to claim 1, wherein the sensitivity control means is a color correction member arranged on the optical path of the exposure light from the exposure light source to the photoelectric conversion element, The product of the spectral attenuation rate of the color correction member for the exposure light and the spectral sensitivity characteristic of the photoelectric conversion element for the exposure light is substantially proportional to the spectral sensitivity characteristic of the photosensitive substrate for the exposure light. An exposure apparatus characterized by the above. 3. The exposure apparatus according to claim 2, wherein a spectral attenuation factor of the color correction member with respect to the exposure light is variable according to a spectral sensitivity characteristic of a photosensitive substrate to be exposed. Exposure equipment. 4. The exposure apparatus according to claim 1, 2, or 3, wherein the predetermined wavelength width of the exposure light is 20 nm.