JPH0992593A - Projection exposure system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a projection exposure system, wherein a focal point is accurately detected or aligned in a scanning direction, and various sensors to provide are lessened in number. SOLUTION: Either of illumination fields 21a and 21b is selectively formed at a prescribed interval in a scanning direction in an effective exposure field of a projection optical system by a reticule blind provided between a light source system and a reticule. An AF beam of a focal point detecting system is so set as to irradiate a pre-read region 22 located nearly at a middle point between the illuminating fields 21a and 21b as a slit light. The alignment illuminating lights of two alignment sensors are so set as to irradiate alignment regions 23a and 23b located at the ends of the pre-read region 22. When a shot region 25a is scanned in a -X direction, the illuminating field 21a located on a -X direction side is used, and when a shot region 25b is scanned in a +X direction, the illuminating field 21b located on a +X direction side is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used for manufacturing a semiconductor element, a liquid crystal display element, an image pickup element (CCD or the like), a thin film magnetic head or the like in a photolithography process, and more particularly to a rectangular exposure apparatus. Or a so-called slit scan method or step of sequentially exposing the pattern on the mask onto the substrate through the projection optical system by scanning the mask and the photosensitive substrate synchronously with respect to an illumination area having an arc shape or the like. It is suitable for application to a scanning exposure type projection exposure apparatus such as an AND scan method.

[0002]

2. Description of the Related Art Conventionally, an exposure apparatus used for manufacturing a semiconductor device or the like mainly uses a reticle (or photomask, etc.) pattern through a projection optical system to form a photoresist by a step-and-repeat method. It was a projection exposure apparatus (stepper etc.) of a batch exposure system which exposes each shot area on a wafer (or glass plate etc.) coated with. On the other hand, recently, one chip pattern such as a semiconductor element tends to be large, and in a projection exposure apparatus, a pattern having a larger area can be efficiently exposed to each shot area on a wafer. Is required. Even when such an increase in area is performed, it is necessary to keep the distortion of the projected image within a predetermined amount over the entire area of each shot area. Therefore, in order to reduce the distortion over the entire area of each shot area and to increase the area,
After stepping each shot area on the wafer to the scanning start position, for example, an illumination area having a rectangular shape, an arc shape, or a plurality of trapezoids (this is called a "slit-shaped illumination area")
On the other hand, attention is focused on a scanning exposure type exposure apparatus such as a so-called step-and-scan method that sequentially exposes a pattern on a reticle to each shot area by scanning a reticle and a wafer in synchronization.

Even in such a scanning exposure type exposure apparatus, normally, the focal position of the wafer (the position in the optical axis direction of the projection optical system).
There is provided a focus position detection system for detecting, and an alignment sensor used for aligning each shot area between the reticle and the wafer. Then, the focus position detection system and the alignment sensor irradiate the wafer with a focus position detection light beam (hereinafter referred to as “AF beam”) and alignment illumination light, respectively, to perform autofocus and position adjustment of each shot area of the wafer. Was going on.

FIG. 4 shows an irradiation area of an AF beam and alignment illumination light on a wafer in a conventional scanning exposure type exposure apparatus. In this case, the alignment sensor may be, for example, an LSA (Lase (Lase) that irradiates a laser beam on a wafer mark in a dot array on the wafer and detects the position of the mark using the light diffracted or scattered by the mark.
r Step Alignment) type alignment sensor is used. In FIG. 4, pre-reading areas 32a and 32b on the front side in the scanning direction of the slit-shaped illumination field field 31 formed with a predetermined width in the scanning direction (X direction) on the wafer.
Further, the AF beams from the two focus position detection systems are respectively irradiated as a plurality of slit lights (not shown). In addition, the pre-reading area 32a of the Teruno field 31 in the -X direction
Alignment region 3 near the non-scanning direction (± Y direction) of
3a and 34a are set so as to be irradiated with the alignment illumination light from the alignment sensor, respectively. Similarly, a pair of alignment regions 33b and 34b in the non-scanning direction of the + X direction prefetch region 32b of the illumination field 31 are similarly provided. The alignment illumination light from the alignment sensor is set to be emitted.

Then, for example, when the shot area 30a is exposed by scanning the shot field 30a in the + X direction shown by the arrow B with respect to the illumination field 31, the focus position of the wafer detected in the preread area 32a on the −X direction side. Autofocus is performed on the basis of the
The alignment is performed based on the position information of the wafer mark detected in a. On the other hand, when the shot area 30b is scanned with respect to the illumination field 31 in the −X direction indicated by the arrow A to perform exposure, the preread area 32 on the + X direction side.
The autofocus and the alignment are performed based on the information detected in the b and the alignment areas 33b and 34b.

[0006]

In the prior art as described above, in order to cope with the switching of the scanning direction, 2
Since one focus position detection system and two pairs of alignment sensors are used, if an offset occurs between the detection results of the focus position detection systems and between the alignment sensors, defocus and alignment errors occur depending on the scanning direction. There was an inconvenience. Also, Teruno Field 31
Since two focus position detection systems and two pairs of alignment sensors are required on both sides in the scanning direction, there is a disadvantage that the mechanism including the focus position detection system and the alignment sensor becomes large and complicated.

In view of the above point, the present invention does not cause a focus position detection error or an alignment error in the scanning direction,
An object of the present invention is to provide a projection exposure apparatus which can perform autofocus or alignment accurately regardless of the scanning direction and has a small number of sensors such as a focus position detection system or an alignment sensor.

[0008]

In a projection exposure apparatus according to the present invention, a part of a transfer pattern on a mask (1) is projected onto a substrate (2) via a projection optical system (3). ,
In synchronization with scanning the mask (1) with respect to the projection optical system in a predetermined direction (+ X direction or −X direction), the substrate (2) is moved with respect to the projection optical system (3) in the predetermined direction. In the projection exposure apparatus that sequentially transfers the image of the transfer pattern of the mask (1) onto the substrate (2) by scanning in the direction corresponding to the direction (-X direction or + X direction), Effective exposure field of system (3) (2
0) in the scanning direction of the substrate (2) or a plurality of exposure areas (21
a, 21b) for setting the exposure area switching means (10,
11) and a plurality of exposure areas (21a, 21b)
A surface for detecting the position of the substrate (2) in the direction of the optical axis (AX) of the projection optical system (3) and controlling the height or inclination angle of the substrate (2) based on the detection result. Position control means (8a, 8b, 5, 7, 17) and its substrate (2)
Control means (1) for switching the exposure area of the projection optical system (3) via the exposure area switching means (10, 11) according to the scanning direction of the projection optical system (3).
7) and.

According to the projection exposure apparatus of the present invention, for example, as shown in FIG. 3, when the shot area (25a) is scanned in the direction of arrow A, one of the exposure areas (21
When the shot area (25b) is scanned in the direction of the arrow B using a), the other exposure area (21b) is used. In addition, regardless of the scanning direction, autofocusing or autoleveling is commonly performed using the surface position control means. Therefore, since the detection value at the common detection position is used regardless of the scanning direction, an error of the detection value depending on the scanning direction does not occur, and the surface position can always be detected with high accuracy. Further, it is not necessary to provide sensors such as a focus position detection system on both sides of the exposure area, and the number of sensors installed can be reduced.

In this case, the plurality of exposure areas (21
a, 21b), an alignment sensor (9a) for detecting the position of the alignment mark on the substrate (2) is provided in a region near the substrate (2) and the mask thereof. It is preferable to perform the alignment with (4). Accordingly, the position of the alignment mark on the substrate (2) is detected by the common alignment sensor (9a) regardless of the scanning direction, and the alignment is performed.

Further, the exposure area switching means (10,
11) selectively sets a collective exposure area (21e) including all of the plurality of exposure areas (21a, 21b) in the effective exposure field of the projection optical system (3), and the collective exposure area (21e) is set. 21e), the exposure may be performed with the mask (1) and the substrate (2) kept stationary.

As a result, the projection exposure apparatus of the present invention can be used not only as a scanning exposure type but also as a batch exposure type such as a stepper.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an embodiment of a projection 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 step-and-scan type projection exposure apparatus. FIG. 1 shows a schematic configuration of the projection exposure apparatus of this example. In FIG. 1, the illumination light IL emitted from a light source system 13 including a mercury lamp for exposure, an optical integrator, and the like is the first relay lens 12a. After passing through, the light enters a reticle blind (variable field stop) 10 arranged on a surface substantially conjugate with the reticle 1 described later. The reticle blind 10 is composed of four movable blades for setting the position and shape of the passage area of the illumination light IL to a desired state, and the blind drive device 11 changes the positions of these four movable blades. It can be controlled. The reticle blind 10 is controlled by a main control system 17 via a blind drive device 11. As the illumination light for exposure, other than the i-line (wavelength: 365 nm) of a mercury lamp,
Excimer laser light (wavelength: 248 nm, 193 nm, etc.)
Etc. can also be used. Further, a shutter is installed in the light source system 13, and the illumination light IL can be emitted only for a desired period by the shutter.

The illumination light IL formed by the reticle blind 10 passes through the second relay lens 12b and enters the dichroic mirror 14. The illumination light IL bent downward by the dichroic mirror 14 is irradiated onto the reticle 1 via the condenser lens 15, and the image of the pattern in the illumination area on the reticle 1 is projected through the projection optical system 3 to the projection magnification β. (Β is 1/4, 1/5, etc.)
Is projected onto the illumination field on the wafer 2. here,
The Z axis is taken parallel to the optical axis of the projection optical system PL, and the X axis is parallel to the scanning direction of the reticle 1 and the wafer 2 during scanning exposure in the plane perpendicular to the Z axis (direction parallel to the paper surface of FIG. 1). Take
Direction perpendicular to the X-axis in the plane perpendicular to the Z-axis (non-scanning direction)
Take the Y axis to. In this example, the reticle 1 is a reticle stage 1 that is slidable in the X direction on a reticle base (not shown).
6, the wafer 2 is placed on the Z stage 5 for driving the wafer holder 4 in the optical axis AX direction of the projection optical system 3 via the wafer holder 4, and the Z stage 5 is
The wafer 2 is held on an XY stage 18 which scans the wafer 2 in the X direction and positions it in the Y direction. The Z stage 5 and the XY stage 18 are controlled by the main control system 17 via the Z stage drive system 7 and the wafer stage drive system 19, respectively.

Reticle stage 16 and XY stage 1
8 stage driving mechanism is composed of the main control system 17 during scanning exposure, in synchronism with scanning the reticle R via the reticle stage 16 + X direction (or -X direction) at a predetermined speed V _R, XY through the stage 18 is scanned in the -X direction a predetermined shot area on the wafer 2 with respect to the illumination field field (or + X direction) velocity _{V W (= β · V R} ). As a result, the pattern of the reticle 1 is successively transferred and exposed onto the shot area.

Further, in the apparatus of FIG. 1, slit images 24a to 24c are slanted toward the exposure surface of the wafer 2 (FIG. 2 (a)).
Measurement beams (hereinafter, referred to as “A”) for forming
An irradiation optical system 8a for irradiating LF (referred to as “F beam”);
A light receiving optical system 8 which receives the reflected light beam of the focus beam LF on the exposed surface of the wafer 2 and re-images each slit image.
and an oblique incidence type focus position detection system (hereinafter referred to as "focus position detection systems 8a and 8b").

2 (a) to 2 (e) respectively show the effective exposure field 20 of the projection optical system 3 of the present example, and among them, as shown in FIG. 2 (a), the central portion of the effective exposure field 20. The AF beam LF from the focus position detection systems 8a and 8b of FIG. 1 is evenly spaced in the Y direction within the slit-shaped preread area 22 set to cross the Y direction (non-scanning direction).
Are emitted as slit images 24a to 24c. Then, from the light receiving optical system 8b of FIG.
The three focus signals corresponding to the lateral shift amount of the re-formed image of 24c are supplied to the main control system 17,
Then, the average focus position in the prefetch area 22 of the wafer 2 is obtained from the supplied focus signal. Then, the main control system 17 performs pre-reading autofocus control of the wafer via the Z stage drive system 7 so that the focus position always matches the focus position of the image plane of the projection optical system 3. Further, in the vicinity of both end portions of the prefetch area 22 in the non-scanning direction (Y direction), alignment areas 23a and 23 are respectively irradiated with alignment illumination light from an alignment sensor described later.
b is set.

Here, an example of the illumination field of this example that can be set to a desired state by controlling the reticle blind 10 in FIG. 1 will be described with reference to FIGS. 2 (a) to 2 (e). First, the illumination field is the illumination area set on the pattern formation surface of the reticle 1 by the reticle blind 10 of FIG. 1 and the wafer 2 that is conjugate with respect to the projection optical system 3.
The upper exposure area, that is, the projection area of the pattern of the reticle 1 onto the wafer 2 at a certain point of time.

In this example, the reticle blind 10
2A, a slit-shaped illumination field field 21a can be set in the effective exposure field 20 in the −X direction (scanning direction) with a predetermined separation from the prefetch area 22 as shown in FIG. 2A. In addition, as shown in FIG.
It is also possible to set a slit-shaped illumination field field 21b symmetrical to the illumination field field 21a by separating the prefetch area 22 for a predetermined distance in the + X direction. Further, by controlling the reticle blind 10, the illumination field fields 21c and 21d can be set so as to include the prefetch area 22 as shown in FIGS. 2C and 2D, and are shown in FIG. As shown in FIG. 2A and FIG.
It is also possible to set an illumination field 21e having a size that covers 1a and 21b. Teruno field 2 of the last large area
If 1e is used, it is possible to perform the exposure by the normal batch exposure method in a stationary state.

In the vicinity of the upper side surface of the projection optical system 6 and below the reticle stage 16, as an example, TTL is used.
(Through the lens) method and LSA (Laser Step)
An alignment sensor 9a of the Alignment type is installed. The alignment sensor 9a is used for final alignment (alignment) between the reticle 1 and each shot area of the wafer 2. Therefore, as shown in FIG. 3A, on the side surface of the shot area 25a on the wafer 2, wafer marks 28a to 28d composed of dot-row-shaped wafer marks 27a and 27b are arranged at predetermined intervals.
Wafer marks 29a to 29d are also symmetrically arranged on the side surface opposite to the shot area 25a.

When the wafer is aligned, the alignment sensor 9a emits the alignment illumination light La in the wavelength region having a weak sensitivity to the photoresist layer on the wafer 2. The alignment illumination light La emitted from the alignment sensor 9 a passes through the projection optical system 3 and the wafer 2
The upper alignment region 23a (see FIG. 3A) is irradiated with cross-shaped slit lights 26a and 26b. In that state, the XY stage 18 is driven to drive the XY stage 18, for example, as shown in FIG.
The wafer mark 28a in the dot row of
When a and 26b are crossed in the X direction, diffracted light from the wafer mark 28a is generated when the wafer mark 28a hits the slit lights 26a and 26b. The diffracted light from the wafer mark 28a reverses the incident optical path,
It again returns to the alignment sensor 9a via the projection optical system 3 and enters the internal light receiving sensor. The alignment sensor 9a generates a detection signal obtained by photoelectrically converting the amount of light incident on the light receiving sensor. The detection signal is supplied to an alignment processing system (not shown), and in the alignment processing system, the XY stage 18 when the light amount becomes the maximum.
The two-dimensional position of the wafer mark 28a is detected from the X coordinate of. In the projection exposure apparatus of this example, a biaxial LSA type alignment sensor (not shown) is arranged symmetrically with the alignment sensor 9a, and this alignment sensor allows, for example, the shot area 25a of FIG.
The two-dimensional positions of the wafer marks 29a to 29d are detected, and the scanning position and the rotation angle of the wafer 2 are finely adjusted based on the detection results.

The operation of the projection exposure apparatus of this example constructed as described above will be described mainly with reference to FIG. The scanning type exposure apparatus is usually configured to be capable of scanning in both directions (± X directions). In this example, for example, the illumination field 21a of FIG. 2A and the illumination field 21a of FIG. The Teruno field 21b is switched and used. After the illumination field 21a or 21b is set as described above, the main control system 17 of FIG.
By driving the stage 18 to position the shot area of the wafer 2 to be exposed at the scanning start position, irradiation of the illumination light IL for exposure is started, and the reticle stage 1
6 and the XY stage 18 relative to each other to scan the reticle 1
Pattern images are sequentially transferred to the shot area.

In this case, first, as shown in FIG.
When the shot area 25a on the wafer 2 is scanned and exposed in the −X direction indicated by the arrow A, the illumination field 21a on the −X direction side of the preread area 22 is used.
Then, the shot area 25 detected in the prefetch area 22
The wafer is automatically focused on the basis of the focal position of a, and the reticle 1 and the shot area 25a are aligned on the basis of the positions of the wafer marks 28a to 28d and 29a to 29d detected in the alignment areas 23a and 23b. Be seen.

On the other hand, as shown in FIG.
When scanning another upper shot area 25b in the + X direction indicated by arrow B to perform exposure, the illumination field field 21b on the + X direction side of the prefetch area 22 is used. Also in this case, the shot area 25 detected in the prefetch area 22
The wafer is automatically focused on the basis of the focal position of b, and the reticle 1 and the shot area 25b are aligned on the basis of the positions of the wafer marks detected in the alignment areas 23a and 23b.

As described above, according to this embodiment, the two reticle fields 21 are formed by the reticle blind 10 according to the scanning direction.
Since one of a and 21b is formed by switching, the shot area is scanned and exposed while performing autofocus and alignment based on the focal position of the shot area and the position information of the wafer mark at the intermediate position of these two illumination field. The detection results of the focus position detection system and the alignment sensor are not offset depending on the scanning direction. Further, it is sufficient to install half the number of focus position detection systems and alignment sensors as compared with the conventional example.

In this example, two Teruno fields 2
1a and 21b are separated from each other in the scanning direction, but as shown in FIGS. 2 (c) and 2 (d), two illumination field fields 21c and 21d which are overlapped with each other are used by switching. You may. Also, reticle blind 1
Although 0 is provided in front of the second relay lens 12b in this example, the reticle blind 10 may be located below the reticle 1, for example, as long as the reticle blind 10 is located on a surface substantially conjugate with the reticle surface.

Further, in this example, as the alignment sensor, a TTL system and an LSA system using the projection optical system 3 are used, but, for example, an off-axis alignment sensor not using the projection optical system 3, Alternatively, a TTR type alignment sensor via the reticle 1 and the projection optical system 3 may be used. Alternatively, a two-beam interference type (LIA type) or an image pickup type alignment sensor may be used.

Further, as shown in FIG. 2 (e), a wide illumination field 2 covering the two illumination fields 21a and 21b.
1e may be set, and the pattern on the reticle 1 may be collectively exposed to each shot area on the wafer 2 with the reticle 1 and the wafer 2 stationary. Therefore, the projection exposure apparatus of this example is not limited to the scanning exposure type, but can be used also as a batch exposure type projection exposure apparatus such as a stepper that collectively exposes the reticle pattern onto the shot area of the wafer.

The present invention is not limited to the above-described embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0030]

According to the projection exposure apparatus of the present invention, since the exposure area is switched according to the scanning direction and the common surface position control means is used, the focus position detection for the surface position control means is performed. In addition to the need to install a small number of sensors for the system,
There is an advantage that a detection error such as a focus position (height) does not occur depending on the scanning direction. Therefore, there is no need to perform offset correction of the focus position detection system used in the surface position control means, and there is an advantage that a simple device configuration can be achieved.

Further, an alignment sensor for detecting the position of the alignment mark on the substrate is provided in a region near the plurality of exposure regions, and the alignment between the substrate and the mask is performed based on the detection result of this alignment sensor. In this case, the number of alignment sensors installed can be reduced. Further, similar to the case of the surface position control means, there is an advantage that the detection error (alignment error) of the alignment sensor does not occur depending on the scanning direction and the mask and the substrate can be aligned with high accuracy.

Further, the exposure area switching means selectively sets a collective exposure area including all of the plurality of exposure areas in the effective exposure field of the projection optical system, and when the collective exposure area is set, the mask is set. When the exposure is performed with the substrate and the substrate kept stationary, there is an advantage that the projection exposure apparatus of the present invention can also be used as a projection exposure apparatus of a batch exposure system.

[Brief description of drawings]

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

FIG. 2 is a diagram showing various examples of an illumination field that can be set by controlling a reticle blind 10 in FIG.

FIG. 3A is a plan view showing an illumination field field used when scanning a shot area in the −X direction, and FIG. 3B is an illumination field field used when scanning a shot area in the + X direction. FIG.

FIG. 4 is a plan view showing an arrangement of an illumination field field and a look-ahead area of a focus position in a conventional projection exposure apparatus.

[Explanation of symbols]

 1 reticle 2 wafer 3 projection optical system 5 Z stage 8a irradiation optical system (focus position detection system) 8b light receiving optical system (focus position detection system) 9a alignment sensor 10 reticle blind 11 blind drive device 16 reticle stage 17 main control system 18 XY Stages 21a to 21e Teruno field 22 Look-ahead area 23a, 23b Alignment area 25a, 25b Shot area

Claims (3)

[Claims] 1. In a state where a part of a transfer pattern on a mask is projected onto a substrate through a projection optical system, the mask is scanned in a predetermined direction in synchronization with the projection optical system. A projection exposure apparatus that sequentially transfers an image of a transfer pattern of the mask onto the substrate by scanning the substrate in a direction corresponding to the predetermined direction with respect to the projection optical system, Exposure area switching means for setting a plurality of exposure areas so as to be switchable to positions apart from each other in the scanning direction of the substrate within the effective exposure field, and the projection optical system of the substrate for the substrate between the plurality of exposure areas. Surface position control means for detecting a position in the optical axis direction and controlling the height or inclination angle of the substrate based on the detection result; and the exposure area switching according to the scanning direction of the substrate with respect to the projection optical system. And a control unit for switching the exposure region by the projection optical system via a means. 2. The projection exposure apparatus according to claim 1, further comprising an alignment sensor that detects a position of an alignment mark on the substrate in a region in the vicinity of the plurality of exposure regions, A projection exposure apparatus, which aligns the substrate and the mask based on a detection result of a sensor. 3. The projection exposure apparatus according to claim 1, wherein the exposure area switching means sets a collective exposure area including all of the plurality of exposure areas within an effective exposure field of the projection optical system. A projection exposure apparatus, which is selectively set, and performs exposure while the mask and the substrate are stationary when the collective exposure region is set.