JPH08316133A - Exposure system - Google Patents

Abstract

PURPOSE: To measure the distribution of illuminance on the wafer of an exposure system quickly and to reduce the installation space of an illuminance detecting system. CONSTITUTION: In a scanning-type exposure system, which relatively scans a reticle and a wafer and projects and exposes the pattern of the reticle on the wafer, a slit-shaped light receiving part 58 of a illuminance nonuniformity sensor for detecting the illuminance of an exposure region 47 on the wafer is provided on a wafer stage, on which the wafer is mounted. A width D in the scanning direction of the light receiving part 58 is formed as the size of (L + fading width)/2 with regard to a width L of the scanning direction of the exposure region 47. The exposure region 47 is divided into two partial exposure regions 47a and 47b, which are equal in the scanning directions, by a dividing line N extending in the non-scanning direction. Scanning is performed so that the light receiving part 58 is not overlapped on the neighboring exposure region. The distributions of the illuminances of the partial exposure regions 47a and 47b are separately measured. The results are averaged, and the distribution of the illuminance of the exposure region 47 is obtained.

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 for manufacturing a semiconductor device, a liquid crystal display device or the like in a photolithography process, and in particular, for scanning a mask and a photosensitive substrate in synchronization. The present invention relates to a scanning exposure type exposure apparatus such as a so-called slit scan method or a step-and-scan method that sequentially exposes a pattern on a mask onto the substrate.

[0002]

2. Description of the Related Art An exposure apparatus used for transferring and exposing a pattern of a reticle as a mask onto each shot area of a wafer (or a glass plate etc.) coated with a photoresist when manufacturing a semiconductor device or the like. Generally, an illuminance control mechanism is provided to keep the exposure amount for each shot area on the wafer within an appropriate range. The illuminance control mechanism in such an exposure apparatus mainly has an illuminance distribution control mechanism for suppressing unevenness of the illuminance distribution in the illumination area of the reticle, and an integrated exposure amount for each shot area on the wafer to be an appropriate exposure amount. Exposure dose control mechanism for

In this regard, the conventional exposure apparatus is mainly arranged such that each shot area of the wafer is positioned at the exposure position by the step-and-repeat method, and then the reticle pattern is set in a stationary state via the projection optical system. A batch exposure type projection exposure apparatus (stepper or the like) for transferring to a shot area has been used. In the collective exposure method, first, the illuminance distribution control is performed by superimposing light fluxes from a large number of light source images using an optical integrator (fly eye lens or the like) provided in the illumination optical system.
Further, in the batch exposure method, since each shot area is exposed in a static state, the integrated exposure amount for each shot area is calculated by dividing the light flux for monitoring obtained by branching the illumination light for exposure into the actual exposure time. It is calculated by multiplying a signal obtained by continuously receiving light inside and integrating the photoelectric conversion signal of the monitoring light flux by a predetermined coefficient which is experimentally obtained in advance.

Therefore, the exposure amount control mechanism for the projection exposure apparatus of the batch exposure system includes a photoelectric detector (integrator sensor) that receives the light flux for monitoring, and an integrating means that integrates the detection signal of the integrator sensor. It can be easily configured by the control means for controlling the illuminance of the illumination light or the exposure time so that the difference between the integration result by the integration means and the target value becomes small.

Further, in order to improve the resolution and the depth of focus for a fine periodic pattern, for example, a modified light source method (for example, a special light source method) in which the aperture stop of the illumination system is formed of a plurality of apertures eccentric with respect to the optical axis. Kaihei 4-225358), or an annular illumination method in which the shape of the illumination system aperture stop is annular. Even when the shape of the aperture of the illumination system aperture stop changes in this way, by arranging the light receiving surface of the integrator sensor on the detection surface that is substantially conjugate with the wafer surface, The illuminance of can be accurately monitored. Therefore, for example, by controlling the exposure time so that the value obtained by integrating the detection signal of the integrator sensor converges to a predetermined target value, the integrated exposure amount in each shot area of the wafer can be easily adjusted to an appropriate value. Can fit in range.

On the other hand, recently, a single chip pattern such as a semiconductor element tends to be large in size, and in a projection exposure apparatus, a large area for efficiently exposing a pattern of a larger area onto a wafer. Is required. In order to achieve such a large area, it is particularly necessary to keep the distortion within a predetermined amount or less on the entire surface. Therefore, in order to reduce the distortion over the entire wide exposure area, after stepping each shot area on the wafer to the scanning start position, the reticle and the wafer are synchronously scanned with respect to the projection optical system, so that the reticle on the reticle is scanned. An exposure apparatus of a so-called step-and-scan method, which sequentially exposes each pattern on each shot area on the wafer, has been attracting attention. This step-and-scan type projection exposure apparatus uses a conventional projection optical system of the same size to synchronously scan a reticle and a wafer, thereby sequentially exposing the reticle pattern onto the entire surface of the wafer. This is an extension of the slit scan type projection exposure apparatus (aligner, etc.).

Among the illuminance control mechanisms of the projection exposure apparatus of the scanning exposure system such as the slit scan system or the step-and-scan system, the illuminance distribution control system is an optical integrator as in the case of the collective exposure system. in use. However, when a fly-eye lens is used as an optical integrator, the incident surface of each lens element of the final stage fly-eye lens is conjugated with the pattern surface of the reticle. Further, in the scanning exposure method, the illumination area on the reticle is an elongated rectangular or arcuate area (hereinafter referred to as “slit-shaped illumination area”). The cross-sectional shape of each lens element forming the lens is preferably an elongated rectangle that is substantially similar to the slit-shaped illumination area.

On the other hand, as the exposure amount control mechanism for the scanning exposure system, it is difficult to directly apply the exposure amount control mechanism for the collective exposure system. In the scanning exposure method, since each shot area of the wafer is scanned with respect to a slit-shaped exposure field shorter than the length of these shot areas, the cumulative exposure amount in each shot area is controlled by It is executed so that the integrated exposure amount is constant at all points on the wafer. If the integrated exposure amount at each point on the wafer is different, unevenness of the integrated exposure amount occurs in each shot area, which is similar to the uneven illuminance in the illumination area in the batch exposure type exposure apparatus. There will be an error.

Further, as one method for controlling the integrated exposure amount in the batch exposure method, the exposure time is controlled by opening and closing a shutter, for example, but in the scanning exposure method, the exposure is continuously performed, so that the wafer is exposed. The integrated exposure amount at each point above cannot be controlled by opening and closing the shutter. Therefore, in the scanning exposure method, for example, the reticle and the wafer are each scanned at a predetermined constant speed to control the integrated exposure amount. With such a method of controlling the scanning speed, it is difficult to finely adjust the integrated exposure amount in terms of time. Therefore, in the scanning exposure method, it is further necessary to perform illuminance control so that the illuminance is continuously maintained temporally during the exposure of each shot area. In this regard, in the case of the batch exposure method, as a control method for keeping the illuminance constant, the illuminance of the illumination light is constantly monitored, the result is fed back to the power source of the exposure light source, and the power source is supplied to the exposure light source. There is known a constant illuminance control method for controlling electric power.

When the illuminance is controlled to be constant in this way, the illuminance of the illumination light on the wafer (energy per unit area, unit time) is E, the scanning speed of the wafer is V, and the slit on the wafer is If the width of the exposure field in the scanning direction in the scanning direction is L and the sensitivity (photosensitive energy per unit area) of the photoresist on the wafer is P, the following conditions must be satisfied in order to obtain an appropriate exposure amount.

P = E (L / V), that is PV = EL In this case, if the width L of the slit-shaped exposure field is fixed and the sensitivity P of the photoresist is set to an arbitrary value, the wafer scanning speed V or the illumination is set. By varying the illuminance E of light, proper exposure can be achieved for photoresists having different sensitivities.

Therefore, for example, the illuminance E of the exposure illumination light is changed to control the integrated exposure amount. In that case,
It is necessary to measure the illuminance on the wafer with an uneven illuminance sensor (photoelectric detector, etc.) quickly and accurately, and based on that, control the output of the light source of the illumination light for exposure, or the amount of dimming at the dimming unit in the middle. There is. FIG. 9 shows an example of a light receiving portion of an illuminance unevenness sensor provided on a conventional wafer stage, and FIG.
Shows an example in which the shape of the light receiving portion is a slit. In FIG. 9A, the effective exposure field 1 of the projection optical system
With respect to a rectangular exposure field 102 having a long side in the non-scanning direction (Y direction) that is almost inscribed with 01, a slit-shaped light receiving unit 103 of the illuminance unevenness sensor having a long side in the scanning direction.
Is scanned in the non-scanning direction as indicated by the solid arrow to measure the illuminance unevenness in the non-scanning direction. In this case, the width DA of the light receiving unit 103 of the uneven illuminance sensor in the long side direction is the width L of the exposure field 102 because the exposure amount is measured by one scanning.
It is formed larger than A. On the other hand, FIG.
(B) shows an example in which the shape of the light receiving portion is a pinhole. In FIG. 9B, a pinhole-shaped light receiving portion 104 is two-dimensionally scanned with respect to the exposure field 102 as indicated by a scanning line 105, and the exposure amount distribution is measured over the entire exposure field 102. Is.

[0013]

However, as shown in FIG.
When the slit-shaped light receiving unit 103 wider than the width of the exposure field 102 in the scanning direction shown in (a) is used, the processing speed is high, but there is a disadvantage that a large installation space is required on the wafer stage. Furthermore, because the light receiving part is long,
There is also a disadvantage that the accuracy of the measurement result is low due to the uneven sensitivity. On the other hand, the pinhole-shaped light receiving unit 1 shown in FIG.
When 04 is used, the installation space on the wafer stage is small, but the processing speed is slow because of the large number of measurement points.

In view of the above problems, an object of the present invention is to provide a scanning exposure type exposure apparatus having a measuring unit for measuring illuminance unevenness, which has a short measuring time and a relatively small installation space.

[0015]

In the exposure apparatus according to the present invention, a part of a pattern formed on a mask (R) is projected onto the substrate (W), and the mask (R) and the substrate (W). In a scanning type exposure apparatus for sequentially transferring and exposing the pattern formed on the mask (R) onto the substrate (W) by scanning the substrate (W). The direction (X direction) is the longitudinal direction,
Further, the photoelectric detection means (49) having a slit-shaped light receiving portion (58) narrower than the exposure area (47) of the pattern formed on the mask (R) in the scanning direction and the exposure area (47) are provided. On the other hand, relative movement means (48) for relatively moving the photoelectric detection means (49) in the direction (Y direction) perpendicular to the scanning direction of the substrate (W), and the photoelectric detection means (48) by this relative movement means. 49) and its exposure area (4
7) and a signal processing means (19) for taking in the photoelectric conversion signal output from the photoelectric detection means (49) when it is relatively moving.

In this case, the width (D) of the slit-shaped light receiving portion (58) of the photoelectric detecting means (49) in the scanning direction of the substrate (W) is wider than the blur width of the exposure area (47). It is preferable.

[0017]

According to the exposure apparatus of the present invention, since the slit-shaped light receiving portion (58) of the photoelectric detecting means (49) is narrower than the exposure area (47) in the scanning direction, the photoelectric detecting means (49) is provided.
The installation space can be made smaller than in the conventional case where a light receiving portion wider than the exposure area (47) is used.

When the width (D) of the slit-shaped light receiving portion (58) of the photoelectric detecting means (49) in the scanning direction of the substrate (W) is wider than the blur width of the exposure area (47), the light receiving is performed. The unevenness of the illuminance in the blurred area can be accurately grasped by moving the blurred area in the exposure area (47) by the portion (58) and moving in the non-scanning direction.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exposure apparatus according to the present invention will be described below with reference to FIGS. In this embodiment, the present invention is applied to a step-and-scan type projection exposure apparatus. FIG. 1 shows a projection exposure apparatus of this embodiment. In FIG. 1, the illumination light from a mercury lamp 1 is condensed by an elliptical mirror 2. A shutter 4 which is opened and closed by a shutter control mechanism 5 is arranged in the vicinity of the converging point, and when the shutter 4 is in an open state, the illumination light is converted into a substantially parallel light flux via a mirror 3 and an input lens 6, Reach field stop 7. Immediately after the field stop 7,
A light-reducing plate 23 is arranged so that it can be freely taken in and out, and the light-reducing plate 23 can change the amount of illumination light passing through the field stop 7 stepwise or continuously within a predetermined range.

The light-reducing plate 23 is, for example, a plurality of reflective half mirrors arranged so as to be switchable, and the inclination of each half mirror with respect to the optical axis is set so that the overall transmittance becomes a predetermined transmittance. Has been done. Then, the dimming plate 2 is driven by the dimming plate driving mechanism 24 including the driving motor.
By moving 3 in steps, the amount of illumination light is adjusted. In this embodiment, it is the exposure amount control system 20 that controls the exposure amount for the wafer W, and the exposure amount control system 2
0 controls the operation of the dimming plate drive mechanism 24 and also controls the operation of the shutter control mechanism 5. Further, the exposure amount control system 20 controls the current supplied to the mercury lamp 1 via the power supply system 22 for the mercury lamp 1.

After passing through the aperture of the field stop 7, the dimming plate 2
The illumination light whose amount of light is adjusted by 3 enters the first fly-eye lens 9 of the two-stage fly-eye lens group via the first relay lens 8. Illumination light from the plurality of light source images by the first fly-eye lens 9 is emitted by the second relay lens 12
It is guided to the second fly-eye lens 14 via A. In this example, the light quantity diaphragm 10 is arranged near the exit surface of the first fly-eye lens 9, that is, the surface on which the light source image is formed.
The size of the opening can be adjusted to any size by the light amount diaphragm drive mechanism 11. The operation of the light amount diaphragm drive mechanism 11 is also controlled by the exposure amount control system 20. In this example, by adjusting the size of the aperture of the light amount diaphragm 10, the light amount of the illumination light traveling from the first fly-eye lens 9 to the second fly-eye lens 14 can be continuously adjusted.

FIG. 2A shows an example of the light quantity diaphragm 10. In FIG. 2A, the light quantity diaphragm 10 is composed of an iris diaphragm. In this case, for example, by moving a lever around the iris diaphragm, the size of the substantially circular opening of the iris diaphragm can be continuously adjusted as shown in FIG. Returning to FIG. 1, recently, by narrowing the numerical aperture (NA) of the illumination optical system, that is, by reducing the coherence factor (σ value), which is the ratio of the numerical aperture of the illumination optical system to the numerical aperture of the projection optical system, , Techniques for improving the depth of focus for a given pattern have been developed. When the σ value is reduced in this way, the illuminance of the illumination light that illuminates the reticle decreases. In this example, an adjusting mechanism for adjusting the size of the illumination area on the incident surface of the second fly-eye lens 14 is provided as a means for preventing such a decrease in illumination light intensity.

The adjusting mechanism is the second relay lens 12A.
And a second relay lens 12B having a refractive power larger than that of the second relay lens 12A and an exchange mechanism 13 for switching between the two second relay lenses 12A and 12B. The operation of the exchange mechanism 13 is controlled by a main control system 19 which controls the operation in a centralized manner. Then, when performing illumination with a normal σ value, one second relay lens 12A is provided between the first fly-eye lens 9 and the second fly-eye lens 14 via the exchange mechanism 13.
Is arranged, whereby almost the entire incident surface of the second fly-eye lens 14 is illuminated by the illumination light. On the other hand, when the illumination is performed with a small σ value (the numerical aperture of the illumination optical system is narrowed), the second fly-eye lens 9 and the second fly-eye lens 14 are connected to each other via the exchange mechanism 13. The two relay lens 12B is arranged so that the central portion of the incident surface of the second fly-eye lens 14 is partially illuminated with the illumination light. Therefore, when the σ value is reduced, the illuminance of the illumination light at the stage of the second fly-eye lens 14 increases, so that the illuminance of the illumination light on the reticle and the wafer is substantially constant regardless of the σ value. Maintained.

Although the adjusting mechanism of this embodiment is of a switching type, the adjusting mechanism is the same as that of the first fly-eye lens 9 and the second fly-eye lens 9.
The zoom lens system may be arranged between the fly-eye lens 14 and the zoom lens system, and a zooming mechanism for zooming the zoom lens system. By using the zoom lens system as described above, the size of the illumination visual field on the incident surface of the second fly-eye lens 14 can be continuously changed. Therefore, even when the σ value is continuously changed, there is an advantage that the illuminance on the reticle and the wafer can always be kept high.

Next, the second fly-eye lens 14 of this example
Are two lens bundles 14a and 1a each having a flat surface on one side in which the lens elements are closely arranged in a mosaic shape.
4b are arranged close to each other so that their flat portions face each other. Therefore, the second fly-eye lens 14 is hereinafter referred to as a "mosaic type fly-eye lens 14".

FIG. 3 (a) is a side view of the mosaic type fly's eye lens 14 of this example. In FIG. 3 (a),
Each flat surface portion FB along the optical axis AX1 of the illumination optical system
A mosaic fly-eye lens 14 is composed of two lens bundles 14a and 14b arranged so that FC and FC face each other at a distance δ. In this case, each lens element forming the first lens bundle 14a on the light source side has a refracting power on the incident surface FA side, and each lens element forming the second lens bundle 14b on the reticle side emits surface respectively. It has a refractive power on the FD side.

Further, the parallel light flux which is incident on the first lens bundle 14a from the light source side is the exit surface F of the second lens bundle 14b.
The refractive power of each lens element is such that the parallel light flux that is condensed on D and that is incident on the second lens bundle 14b from the reticle side is condensed on the incident surface FA of the first lens bundle 14a. Has been defined. That is, the second lens bundle 14b
The exit surface FD is the focal plane of the mosaic fly-eye lens 14, and a large number of light source images are formed on the exit surface FD. Therefore, the lens bundles 14a and 14b act as one fly-eye lens only when the two are combined. The two lens bundles 14a and 14b of the mosaic fly-eye lens 14 shown in FIGS.
The number of lens elements constituting the above is an example, and the number of lens elements is determined according to the required accuracy of the uniformity of the illuminance distribution that is actually required.

FIG. 3B is a front view showing the first lens bundle 14a taken along line AA of FIG. 3A, and FIG. 3C is taken along line CC of FIG. 3A. FIG. 4 is a front view showing the second lens bundle 14b, and in FIGS. 3A and 3C, the direction corresponding to the scanning direction of the reticle during scanning exposure of the projection exposure apparatus of this example is defined as X1 direction, and The direction corresponding to the non-scanning direction perpendicular to the scanning direction is the Y1 direction.

In this case, as shown in FIG. 3B, the first
The lens bundle 14a of No. 1 has the first row by arranging the lens elements 61 each having a slender rectangular cross-sectional shape with a width dx in the X1 direction and a width dy (dy> dx) in the Y1 direction in close contact with each other in the Y1 direction. 62A, 2nd row 62B, 3rd
A lens group of each row of the rows 62C, ... And an odd-numbered lens group of the first row 62A, the third row 62C, ... And an even-numbered second row 62B, the fourth row 62D ,. And are shifted in the Y1 direction by 1/2 of the width dy of the lens element.

In this example, as shown in FIG. 3A, the entrance surface of the mosaic fly-eye lens 14, that is, the first lens bundle 1
When the incident surface FA of 4a is conjugate with the pattern surface of the reticle, and the cross-sectional shape of the lens element 61 forming the first lens bundle 14a is similar to the slit-shaped illumination area on the reticle, the illumination efficiency is the highest. Becomes higher. Therefore, the width d in the X1 direction of the cross-sectional shape of the lens element 61
The value of the ratio of x to the width dy in the Y1 direction is set to be substantially equal to the value of the ratio of the width in the scanning direction of the slit-shaped illumination area on the reticle to the width in the non-scanning direction. Therefore, the cross section of the lens element 61 is Y corresponding to the non-scanning direction.
It is a rectangle elongated in one direction. As an example, dx:
dy is set to about 1: 3.

Further, as shown in FIG. 3C, the second lens bundle 14b has a width ex (= 2 · dx) in the X1 direction and a Y value.
By arranging the lens elements 65 having a substantially square cross section with a width ey (= dy / 2) in one direction in close contact with each other in the X1 direction, the first row 66A and the second row
A lens group of each row of the row 66B, the third row 66C, ... And an odd-numbered first row 66A, a third row 66C, ... and an even-numbered second row 66B, the fourth row 66D,
The lens group of ... is the width ex of the lens element in the X1 direction.
It is configured to be shifted by 1/2. Incidentally, when the cross-sectional shape of the lens element 61 of the first lens bundle 14a is about dx: dy = 1: 3, the cross-sectional shape of the lens element 65 of the second lens bundle 14b is ex: ey = 2: Since 1.5 = 4: 3, the lens element 65 has a substantially square cross section.

In such an arrangement, the center of a certain lens element of the first lens bundle 14a and the center of a certain lens element of the second lens bundle 14b are further aligned in the X1 direction and the Y1 direction. This allows
The centers 63 of all the lens elements 61 forming the first lens bundle 14a and the centers 67 of all the lens elements 65 forming the second lens bundle 14b are arranged at the same position in the X1 direction and the Y1 direction. ing.

Thus, the mosaic type fly-eye lens 1
The mosaic type fly-eye lens 14 of the present embodiment is a fly-eye lens of the second stage, and the operation and effect when 4 is divided into two lens bundles 14a and 14b will be described.
The individual light source images formed on the exit surface of the fly-eye lens in the first stage are the same as the light source images formed in the aperture of the light quantity diaphragm 10 on the exit face of the fly-eye lens 9 in the first stage. It is a statue. That is, each light source image formed on the exit surface of the mosaic fly-eye lens 14 is a large number of minute light source images uniformly distributed in, for example, a circular area.

Accordingly, the light source image formed by projecting the light source image formed on the exit surface of the mosaic type fly-eye lens 14 onto the end surface of the first lens bundle 14a as shown in FIG. A minute light source image is distributed in a circular area 64 centered on the center 63 of each lens element 61. The circular area 64 is the light amount diaphragm 1 shown in FIG.
It is similar to the shape of the 0 opening. However, since the cross-sectional shape of each lens element 61 of the first lens bundle 14a of this example is an elongated rectangular shape, when the aperture of the light quantity diaphragm 10 is set to be large, the circular area 63 forms an end surface of each lens element 61. It will stick out. Therefore, when a fly-eye lens in which lens elements having the same cross-sectional shape as the lens element 61 are bundled is used instead of the mosaic type fly-eye lens 14, vignetting of the light source image occurs on the exit surface and the illumination efficiency decreases. .

On the other hand, in this example, the first lens bundle 1
Immediately after 4a, as shown in FIG. 3C, a second lens bundle 14b composed of lens elements 65 each having a substantially square cross-sectional shape is arranged, and a circle having a center 67 of each lens element 65 as a center. The light source image is formed so as to be distributed in the area 64 of the. In this case, since the cross-sectional shape of the lens element 65 is close to a square, even when the aperture of the light quantity diaphragm 10 in FIG. 2 is set large, the circular region 64 is substantially within the cross section of the lens element 65. Therefore, the mosaic fly-eye lens 14
Vignetting of a large number of light source images formed on the exit surface of is reduced, and the illumination efficiency is improved. The illumination light from a large number of light source images formed on the exit surface of the mosaic fly-eye lens 14 illuminates the illumination light in a superimposed manner, resulting in extremely high uniformity of the illuminance distribution on the reticle and the wafer. .

Further, in FIG. 1, the second lens bundle 14b on the reticle side of the mosaic type fly-eye lens 14 is shifted in the direction perpendicular to the optical axis AX1 and the lens bundle 14b An adjusting mechanism 15 for adjusting the tilt angle (inclination angle) within a predetermined range is attached. In this example, the shift amount of the lens bundle 14b and the tilt angle are adjusted via the adjusting mechanism 15 to correct the shift amount of the telecentricity in the illumination optical system. For example, the main control system 19 controls the operation of the adjusting mechanism 15 when the mercury lamp 1 is replaced or when the illumination conditions are switched (switching between the normal illumination and the modified light source, etc.), so that the telecentricity is automatically achieved. Will be corrected.

In FIG. 1, an illumination system aperture stop plate 16 having a plurality of types of illumination system aperture stops is installed near the exit surface of the mosaic fly-eye lens 14. FIG. 4 shows the aperture stop plate 16 of the illumination system. In FIG. 4, the aperture stop 18A of a normal circular aperture and the coherence aperture of a small circular aperture are formed on the illumination system aperture stop plate 16 at substantially equal angular intervals. An aperture stop 18B for reducing the σ value that is a factor, a ring-shaped aperture stop 18C for annular illumination, and a modified aperture stop 18D in which a plurality of apertures are eccentrically arranged for the modified light source method are arranged. ing. By rotating the illumination system aperture stop plate 16, a desired aperture stop can be selected from the four aperture stops.

Returning to FIG. 1, the main control system 19 controls the rotation angle of the illumination system aperture diaphragm plate 16 via the illumination system diaphragm drive mechanism 17 composed of a drive motor. After being emitted from the mosaic fly-eye lens 14, the illumination system aperture stop plate 16
The illumination light IL that has passed through the aperture stop selected from the inside enters the beam splitter 31 having a transmittance of about 98%. Then, the illumination light transmitted through the beam splitter 31 passes through the first relay lens 34 and the two movable blades 3
Reach a movable blind (variable field stop) with 5A and 35B. Hereinafter, the movable blind will be referred to as “movable blinds 35A and 35B”. Movable blind 35A,
The arrangement surface of 35B is the Fourier transform surface of the exit surface of the mosaic fly-eye lens 14. That is, the arrangement surface of the movable blinds 35A and 35B is conjugate with the pattern formation surface of the reticle R described later,
A fixed blind 37 having a fixed opening shape is arranged near 35B.

The fixed blind 37 is, for example, a mechanical field stop that surrounds a rectangular opening with four knife edges, and the rectangular opening defines the shape of a slit-shaped illumination area on the reticle R. . That is, the illumination light IL limited by the movable blinds 35A and 35B and the fixed blind 37 is evenly distributed over the slit-shaped illumination area 41 on the reticle R via the second relay lens 38, the condenser lens 39, and the mirror 40. Illuminate with illuminance distribution.

In this case, the arranging surface of the fixed blind 37 is slightly defocused in the front or rear direction from the conjugate surface of the pattern forming surface of the reticle R, so that the illuminance of the contour portion of the slit-shaped illumination area 41 is increased. The distribution changes with a certain slope. In addition, the movable blinds 35A and 35B
Serves to prevent the slit-shaped illumination area from covering an area of the reticle R which should not be exposed at the start and end of the scanning exposure. Therefore, the movable blade 35A
And 35B are slide mechanisms 36A and 36B, respectively.
It is supported so that it can be opened and closed. The slide mechanisms 36A and 36B constitute a movable blind drive mechanism,
The operation of the movable blind drive mechanism is controlled by the stage control system 46.

The image of the pattern in the illumination area 41 on the reticle R is slit-shaped exposed on the wafer W through the projection optical system PL at a projection magnification β (β is, for example, 1/4 or 1/5). It is projected on the field 47. Here, the Z axis is taken parallel to the optical axis of the projection optical system PL, the X axis is taken parallel to the scanning direction of the reticle R and the wafer W at the time of scanning exposure in the plane perpendicular to the Z axis, and the axis perpendicular to the Z axis. The Y axis is taken in a direction (non-scanning direction) perpendicular to the X axis in the plane. In this example, Reticle R
Are held on the reticle base 43 via the scanning stage 42 which is slidable in the X direction, and the wafer W is held on the wafer stage 48 which scans the wafer W in the X direction and positions it in the Y direction. . The wafer stage 48 also incorporates a Z stage or the like for positioning the wafer W in the Z direction.

Scan stage 42 and wafer stage 48
A stage drive mechanism is constituted by the stage drive mechanism, and the operation of the stage drive mechanism is controlled by the stage control system 46.
During scanning exposure, the stage control system 46 controls the scanning stage 4
2 in synchronism with scanning the reticle R at a predetermined speed V _R with respect to the illumination region 41 + X direction (or -X direction) via the predetermined shot area on the wafer W via the wafer stage 48 The exposure field 47 is scanned in the −X direction (or + X direction) at the speed V _W (= β · V _R ). As a result, the pattern of the reticle R is successively transferred and exposed onto the shot area. Further, the stage control system 46 controls the positions of the movable blinds 35A and 35B via the slide mechanisms 36A and 36B during scanning exposure. A control method in this case will be described with reference to FIG.

First, immediately after the start of scanning exposure, as shown in FIG.
As shown in (a), the image 37R of the opening portion of the fixed blind 37 of FIG. 1 is exposed to the outside with respect to the light-shielding band 88 surrounding the pattern region 87 of the reticle R. Therefore, in order to avoid exposure to an unnecessary portion, the position of the movable blade 35B in FIG. 1 is moved so that one edge portion 35Ra of the image 35R of the movable blinds 35A and 35B is put in the light shielding band 88. After that, as shown in FIG. 6B, when the image 37R of the fixed blind 37 is within the pattern area 87 in the scanning direction, the movable blinds 35A and 35B.
Image 35R is set so as to surround the image 37R. Then, at the end of the scanning exposure, as shown in FIG. 6C, when the image 37R of the fixed blind 37 appears outside the light-shielding band 88, the position of the movable blade 35A in FIG. 1 is moved, Image 35R of movable blinds 35A and 35B
The other edge portion 35Rb of the above is put in the light-shielding band 88. By such an operation, the slit-shaped illumination region 41 on the reticle R is prevented from coming out of the light-shielding band 88, and the exposure of an unnecessary pattern on the wafer W is prevented.

Further, in FIG. 1, the wafer stage 48
An illuminance nonuniformity sensor 49 including a photoelectric detector having a light receiving surface at the same height as the exposure surface of the wafer W near the upper wafer W.
Is installed, and the detection signal output from the uneven illuminance sensor 49 is supplied to the main control system 19. The uneven illuminance sensor 49 will be described in detail later. Further, a reference mark plate 50 used when performing reticle alignment or the like is provided on the wafer stage 48, and a reference mark 50a having an opening pattern is formed on the reference mark plate 50, which also corresponds to the reticle R. The alignment mark is formed so that. For example, when the reticle R is exchanged, the reference mark plate 50 is moved into the effective exposure field of the projection optical system PL, and the reference mark 50a of the reference mark plate 50 is illuminated by the light source 51 from the bottom side with the same wavelength band as the illumination light IL. Illuminate with light. Under this illumination light,
The images of the reference mark 50a and the alignment mark on the reticle R are observed by the reticle alignment microscope 44 via the mirror 45 above the reticle R. And
The reticle R is aligned with the fiducial mark plate 50 based on the observation result.

Further, a reference mark for focus calibration is also formed on the reference mark plate 50, and a detection system is arranged at the bottom of this reference mark. Figure 5
FIG. 5A shows the reference mark for focus calibration and the detection system, and in FIG.
A reference mark 50b having, for example, a cross-shaped opening pattern is formed in the light-shielding film on the reference mark plate 50, and the detection system 54 is arranged at the bottom of the reference mark 50b. Using the reference mark 50b, the projection optical system P is
The position of the L image plane is obtained. That is, the detection system 54
At the wafer stage 48 via the optical fiber 81.
Illumination light having the same wavelength band as the illumination light IL of FIG. 1 is guided into the interior of the reference mark 50, and the illumination light causes the reference mark 50 to pass through the collimator lens 82, the half mirror 83, and the condenser lens 84.
Illuminate b from the bottom side. The illumination light passing through the reference mark 50b forms an image of the reference mark 50b on the pattern forming surface of the reticle R via the projection optical system PL, and the reflected light from the pattern forming surface passes through the projection optical system PL. To return to the reference mark 50b. Then, the illumination light passing through the reference mark 50b passes through the condenser lens 84, the half mirror 83, and the condenser lens 85 in the detection system 54, and then the photoelectric detector 8 is detected.
It is incident on 6.

The detection signal (photoelectric conversion signal) S6 of the photoelectric detector 86 is supplied to the main control system 19 of FIG. In this case, when the Z stage in the wafer stage 48 is driven to change the position of the reference mark 50b in the Z direction,
As shown in (b), the detection signal S6 is the reference mark 50b.
Changes so that it has a peak when the Z coordinate of is coincident with the position of the image plane of the projection optical system PL. Therefore, the detection signal S
The position of the image plane of the projection optical system PL can be obtained from the change of 6, and thereafter the exposure surface of the wafer W is set at that position, so that the exposure is performed in a good state. Therefore, by using the reference mark 50b of the reference mark plate 50, the position of the image plane of the projection optical system PL is calibrated (focus calibration).

Returning to FIG. 1, the leaked light reflected by the beam splitter 31 having a transmittance of about 98% is collected by the condenser lens 3
An integrator sensor 3 consisting of a photoelectric detector through 2
It is condensed on the light receiving surface of No. 3. Integrator sensor 3
The light receiving surface of 3 is conjugate with the pattern forming surface of the reticle R and the exposure surface of the wafer W, and the integrator sensor 33
Detection signal (photoelectric conversion signal) is supplied to the exposure amount control system 20 and the power supply system 22 for the mercury lamp 1. The exposure amount control system 20 supplies a drive signal corresponding to the target illuminance on the wafer to the power supply system 22, so that the detection signal from the integrator sensor 33 in the power supply system 22 becomes a value corresponding to the target illuminance. Then, the mercury lamp 1 is driven to light. As a result, exposure is performed in the constant illuminance control mode.

When the aperture stop plate 16 for illumination system is rotated to set the aperture stop 18C for annular illumination or the modified aperture stop 18D shown in FIG. 4 on the exit surface of the second-stage fly-eye lens 14, Since the light receiving surface of the integrator sensor 33 is conjugate with the exposure surface, the incident angle of the illumination light on the integrator sensor 33 becomes large, and a sensitivity error may occur due to the incident angle. In order to reduce such a sensitivity error, for example, a diffuser plate that diffuses a light flux is arranged immediately before the light receiving surface of the integrator sensor 33 (or a conjugate surface with the exposure surface), and the light flux diffused by this is integrated. Light may be received by the sensor 33.

A memory 21 is connected to the exposure amount control system 20, and a conversion coefficient for obtaining the exposure energy on the wafer W from the output signal of the integrator sensor 33 is stored in the memory 21. However, in this embodiment, the output signal of the integrator sensor 33 is calibrated using, for example, a predetermined reference illuminance meter, and a correction coefficient for correcting the output signal of the integrator sensor 33 is also stored in the memory 21 based on the calibration result. Remembered in.

The light-receiving surface of the integrator sensor 33 is arranged at a position conjugate with the pattern surface of the reticle, so that even when the shape of the illumination-system aperture stop is changed by rotating the illumination-system aperture stop plate 16, the integrator sensor 33 is rotated. Sensor 3
No error occurs in the detection signal of 3. However,
The light receiving surface of the integrator sensor 33 is connected to the projection optical system PL.
Fourier transform plane (pupil plane) of the reticle pattern at
It may be arranged on an observation surface that is substantially conjugate with, so that all the light fluxes passing through this observation surface can be received. Furthermore,
If a lemon skin or the like is arranged at a position conjugate with the pattern surface of the reticle, and the output light thereof is relayed by a fiber or the like and then an integrator sensor is provided, the problem of heat generation is reduced.

Further, in this example, the integrator sensor 33 is used for the beam splitter 31 having a transmittance of about 98%.
A condenser lens 52 and a wafer reflectivity monitor 53 including a photoelectric detector are installed on the opposite side to the light receiving surface of the wafer reflectivity monitor 53, which is substantially conjugate with the surface of the wafer W by the condenser lens 52. . In this case, of the illumination light that passes through the reticle R and is irradiated onto the wafer W via the projection optical system PL, the reflected light on the wafer W is the projection optical system PL,
The wafer reflectivity monitor 53 receives the light via the reticle R and the like, and the detection signal (photoelectric conversion signal) is supplied to the main control system 19. The main control system 19 passes through the projection optical system PL based on the light amount of the illumination light IL applied to the reticle R side and the light amount of the reflected light on the wafer W calculated from the detection signal of the wafer reflectance monitor 53. The amount of light (power) of the illumination light to be obtained is obtained. Further, the main control system 19 predicts the thermal expansion amount of the projection optical system PL based on the thermal energy obtained by multiplying the light amount thus obtained by the exposure time, and the projection based on this predicted thermal expansion amount. The amount of change in the image forming characteristics such as distortion of the optical system PL is obtained. And the main control system 1
Reference numeral 9 corrects the image formation characteristic of the projection optical system PL to the original state via an image formation characteristic correction mechanism (not shown) connected to the projection optical system PL.

Next, the structure and operation of the uneven illuminance sensor 49 will be described with reference to FIG. FIG. 7A is a diagram for explaining the operation of the uneven illuminance sensor 49. In FIG. 7A, the light receiving unit 58 of the uneven illuminance sensor 49 is formed in a slit shape having a long side in the scanning direction. The width D in the long side direction is the width L in the scanning direction of the rectangular exposure field 47 having a long side in the non-scanning direction (Y direction) that is substantially inscribed in the circumference of the effective exposure field 55 of the projection optical system PL. On the other hand, it is formed so as to satisfy the following expression (1).

Α <D <L (1) Here, α represents the blur width of the end portion of the exposure field 47 in the scanning direction, and varies depending on the defocus amount of the fixed blind 37 in FIG. 1, but as an example, α = L / 10 is set. FIG. 8 shows the distribution of the illuminance E (X) in the scanning direction (X direction) of the slit-shaped exposure field 47 of FIG. 7A. In FIG. 8, the illuminance E (X) changes to a substantially trapezoidal shape. are doing. Then, the illuminance E (X) is the maximum value E _0.
The distance in the X direction at the position of 1/2 of the X-direction becomes the width L of the exposure field 47 in the scanning direction, and the widths of the portions (blurred portions) where the illuminance at both ends of the exposure field 47 is inclined and changed are α. Has become. Further, including the blur portion, the width of the exposure field 47 in the scanning direction is (L + α).

The illuminance unevenness measuring method according to the present invention divides the exposure field 47 into a plurality of parts in the scanning direction, and scans the plurality of divided exposure fields with a slit-shaped light receiving portion in the non-scanning direction. The illuminance in each divided area is measured, and the measurement is performed so that the light receiving unit does not overlap other divided areas during the measurement. Therefore, the width D of the light receiving portion of the uneven illuminance sensor satisfies the range of the above formula (1), and the illuminance of each divided area is formed in a size that can be measured in substantially the same state.

In the case of this example, the exposure field 47 is divided into two, the uneven illuminance of each of the divided exposure regions is measured, and the exposure field 4 is determined based on the measured values.
7 for calculating the illuminance unevenness, and the width D of the light receiving portion 58
Is formed to be slightly wider than (L + α) / 2. This considers the blur width α of the exposure field 47.

Returning to FIG. 7A, the two exposure regions divided by the dividing line N passing through the central portion (X coordinate value x ₀ ) of the exposure field 47 in the scanning direction (X direction) are respectively defined as the partial exposure field 47a. And 47b. The uneven illuminance is first measured for the partial exposure field 47a. First, the light receiving portion 58 is adjacent to the adjacent partial exposure field 47b.
The right end of the light receiving portion 58 is exactly the dividing line N so that it does not overlap
The wafer stage 48 is driven so as to come into contact with
Position 8. Then, the partial exposure field 47a
The wafer stage 48 is driven from the position y ₁ at the end portion in the −Y direction to scan the light receiving portion 58 in the non-scanning direction along the arrow 56A. Meanwhile, the output signal of the illuminance unevenness sensor 49 is set to Y.
The illuminance is measured by sampling at a predetermined pitch in the direction. Note that sampling may be performed on a time basis.

When the light receiving portion 58 moves to the position y ₂ at the end of the partial exposure field 47a in the + Y direction and the scanning of the partial exposure field 47a is completed, the light receiving portion 58 is next scanned along the arrow 56C. In the direction, the scanning is performed at the scanning start position of the partial exposure field 47b to start scanning for measuring the illuminance of the partial exposure field 47b. Also in this case, as in the case of the partial exposure field 47a, the wafer stage 48 is driven so that the left end of the light receiving portion 58 is just in contact with the dividing line N so that the light receiving portion 58 does not overlap the partial exposure field 47a, and the wafer stage 48 is moved in the Y direction. In order to measure the illuminance at a predetermined pitch, the light receiving portion 58 is scanned in the non-scanning direction along the arrow 56B. The measurement value of the uneven illuminance sensor 49 is supplied to the main control system 19, and the uneven illuminance is calculated based on the measured value. Further, the uneven illuminance sensor may generate heat when illuminated for a long time, which may cause sensitivity drift.
Therefore, the influence may be reduced by cooling the sensor unit or by setting the scanning direction of the light receiving unit 58 to the same scanning direction for both of the divided partial exposure fields 47a and 47b.

FIG. 7B shows the illuminance distribution measured by the illuminance unevenness sensor 49, where the horizontal axis represents the position in the Y direction and the vertical axis represents the illuminance E (Y). In FIG. 7B, an output curve 71 indicated by a one-dot chain line shows the illuminance distribution in the non-scanning direction (Y direction) regarding the partial exposure field 47a, and an output curve 72 indicated by a dotted line indicates a non-scanning direction regarding the partial exposure field 47b. The illuminance distribution of is shown. Here, the illuminance E (Y) of the output curves 71 and 72 can be expressed as a function of the position Y in the non-scanning direction, and f (Y) and g (Y), respectively.
And The output curve 73 shown by the solid line is the output curves 71, 7
2 is the average value, and the illuminance function φ (Y) is φ
It is calculated from (Y) = (f (Y) + g (Y)) / 2.
By deriving this illuminance function φ (Y), it is possible to detect the illuminance unevenness of the exposure field 47 as a whole in the non-scanning direction. The above series of calculations are performed by the main control system 19, and based on this, the main control system 19 outputs the output of the mercury lamp 1 and opens the dimming plate 23 via the exposure amount control system 20 so as to prevent uneven exposure. And the degree of opening of the light amount diaphragm 10 are controlled.

The difference (f (Y) -g (Y)) between the illuminances of the two output curves 71 and 72 is mainly due to the fixed blind 37.
This is due to the difference in the shape of the edges. Figure 7 (b)
From the result of the above, f (Y) <g (Y) is satisfied over the entire non-scanning direction except for the vicinity of the position y ₁ , and it is concluded that the upper edge shape of the fixed blind 37 in FIG. 1 needs to be corrected. Is derived. Further, for example, if there is a portion where the illuminance is extremely reduced between the positions y ₁ and y ₂ , the state of the corresponding portion of the fixed blind 37 can be known based on it.
Based on that, the edge can be corrected. Conventionally, the illuminance distribution of the exposure field 47 is measured by one scanning, so even if there is a part where the illuminance is extremely low, which part of the fixed blind is responsible for the edge? Although it could not be specified, according to this example, since the exposure field 47 is divided in the scanning direction and the illuminance thereof is measured, it is possible to specify which part of the fixed blind 37 is caused by the edge shape. .

As described above, according to the exposure apparatus of the present embodiment, the illuminance unevenness sensor 49 having the slit-shaped light receiving portion 58 narrower than the width of the exposure field 47 in the non-scanning direction is used to scan the non-scanning direction a plurality of times. Since the illuminance distribution can be detected, the influence of sensitivity unevenness of the photoelectric conversion element is small, and the processing speed is faster than the conventional illuminance unevenness sensor having a pinhole-shaped light receiving portion. In addition, there is an advantage that a large space is not required on the wafer stage unlike a conventional illuminance unevenness sensor having a slit-shaped light receiving portion wider than the width of the exposure field in the scanning direction. Furthermore, not only can the processing speed and the installation space on the wafer stage of the prior art be solved, but the state of the edge of the fixed blind 37 that determines the width of the illumination area can be detected. Therefore, it is possible to quickly cope with the case where the illuminance unevenness occurs.

As described above, the present invention is not limited to the above-mentioned embodiments, and various configurations can be adopted without departing from the gist of the present invention.

[0062]

According to the exposure apparatus of the present invention, since the light receiving portion of the photoelectric detecting means is smaller than the conventional one using the light receiving portion covering the entire scanning direction, the installation space of the photoelectric detecting means can be reduced. There is an advantage that it is possible and the influence of sensitivity unevenness is small. Further, there is an advantage that the measurement time is shorter than that of the conventional method using the pinhole-shaped light receiving unit.

Further, when the width of the slit-shaped light receiving portion of the photoelectric detecting means in the scanning direction of the substrate is wider than the blur width of the exposure area, the state of the blur width can be accurately grasped, for example, the illumination range. The state of the edge of the field stop to be limited can be detected.

[Brief description of drawings]

FIG. 1 is a partially cutaway view showing a scanning exposure type projection exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a light amount diaphragm 10 used in an embodiment.

3A is an enlarged side view showing a mosaic type fly-eye lens (second fly-eye lens) 14 of FIG.
3B is a front view taken along the line BB of FIG. 3A, and FIG. 3C is a front view taken along the line CC of FIG. 3A.

4 is a view showing a plurality of illumination system aperture stops arranged on the illumination system aperture stop plate 16 of FIG.

5A is a diagram of a main part showing a mechanism for performing focus calibration, and FIG. 5B is a waveform diagram of a detection signal obtained by the mechanism of FIG. 5A.

FIG. 6 is a diagram which is used to explain movable blinds 35A and 35B when performing scanning exposure in the embodiment.

7A is a diagram showing a method of measuring illuminance by the illuminance unevenness sensor 49 of the embodiment of FIG. 1, and FIG. 7B is a diagram showing an illuminance distribution obtained by the measuring method of FIG. 7A. .

8 is a diagram showing an illuminance distribution in the scanning direction of the exposure field 47 of FIG.

FIG. 9A is a diagram showing an example of a measurement method using an uneven illuminance sensor using a conventional long slit-shaped light receiving unit;
(B) is a figure which shows the example of the measuring method by the illuminance unevenness sensor which uses the conventional pinhole-shaped light-receiving part.

[Explanation of symbols]

R Reticle PL Projection optical system W Wafer 1 Mercury lamp 4 Shutter 23 Light-reducing plate 9 First fly-eye lens 10 Light quantity diaphragm 12A, 12B Second relay lens 14 Mosaic type fly-eye lens (second fly-eye lens) 16 Illumination system aperture diaphragm Plate 19 Main control system 20 Exposure amount control system 22 Power supply system 33 Integrator sensor 37 Fixed blind 42 Reticle stage 47 Exposure field 48 Wafer stage 49 Illuminance unevenness sensor 58 Light receiving part α Blurred width D Light receiving part 58 width

Claims (2)

[Claims] 1. A pattern formed on the mask is sequentially scanned by relatively synchronously scanning the mask and the substrate in a state where a part of the pattern formed on the mask is projected onto the substrate. In a scanning type exposure apparatus for transferring and exposing onto the substrate, there is provided a slit-shaped light receiving unit having a scanning direction of the substrate as a longitudinal direction and narrower than an exposure region of a pattern formed on the mask with respect to the scanning direction. Photoelectric detection means, relative movement means for relatively moving the photoelectric detection means in a direction perpendicular to the scanning direction of the substrate with respect to the exposure area, and the photoelectric detection means and the exposure area by the relative movement means. And a signal processing unit that captures a photoelectric conversion signal output from the photoelectric detection unit when the unit is relatively moving. 2. The exposure apparatus according to claim 1, wherein a width of the slit-shaped light receiving portion of the photoelectric detection unit in the scanning direction of the substrate is wider than a blur width of the exposure region. Exposure equipment.