JPH09306833A - Exposing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to eliminate defocusing on a chipped shot region by a method wherein a plurality of detection points in a multipoint focus sensor are selectively used based on the position information of the peripheral part of a wafer an the moving position information of a wafer stage. SOLUTION: A memory 17 stores the positional information of the peripheral part of a wafer W and the information of the moving position of an X-Y stage 11. Accordingly, a main control system 20 succesively selects the detecting point of the presead sensor on the wafer W based on the positional information of the edge of the wafer W and the positional information of the X-Y stage 11 stored in the memory 17. To be more precise, the number of detecting point positioned on the wafer W in the course of conducting a scanning exposing operation, is increased and all the detecting points positioned on the wafer W are selected successively. As a result, a highly reliable and highly precise focus control can be accmplished. Using she above-mentioned selected detection points, the focus position (position in optical axis direction) or the inclined condition of the wafer W can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention sequentially scans a pattern on a mask by scanning a mask and a photosensitive substrate (sensitive substrate) in synchronization with an illumination area such as a rectangle or an arc. The present invention relates to an exposure method and an exposure apparatus that are suitable for a so-called step-and-scan exposure apparatus that exposes light on the top.

[0002]

2. Description of the Related Art Conventionally, in step-and-scan type exposure, a response delay in position control in the direction of the optical axis is avoided with respect to an exposure region on the outer peripheral portion of a photosensitive substrate (hereinafter referred to as a wafer). Therefore, an exposure sequence has been proposed in which scanning exposure is performed from the inner side to the outer side of the photosensitive substrate (Japanese Patent Laid-Open No. 7-16164).

[0003]

In the above-described exposure sequence, the entire exposure area (hereinafter referred to as a defective shot area) on the outer peripheral portion of the wafer is transferred from the inside to the outside of the photosensitive substrate. Since there is a limit to the scanning exposure direction, which is a fixed direction, it is necessary to increase the movement distance of the wafer stage that occurs due to the devising of the exposure sequence, and to scan the mask stage once to return it (empty scan of the mask stage). There was a drawback that Further, when an exposure sequence in which scanning exposure is performed from the outer side to the inner side of the wafer in the defective shot area is used to prevent a decrease in throughput, the detection point for detecting the position of the wafer in the optical axis direction is detected from the outer side of the wafer to the peripheral portion of the wafer. When the (edge) is reached, the followability in the optical axis direction does not catch up and a response delay in position control occurs.
Therefore, the defective shot area is in a defocused state, resulting in unnecessary exposure.

[0004]

In order to solve the above-mentioned problem, according to the present invention, a non-defective shot area on a wafer as a photosensitive substrate is scanned and exposed from the outside to the inside of the wafer. A multi-point focus sensor that detects the focus position (position in the optical axis direction) of the wafer at a plurality of detection points arranged in the scanning direction is provided, and based on position information of the peripheral portion of the wafer and movement position information of the wafer stage. We decided to selectively use multiple detection points in the multi-point focus sensor.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a plurality of detection points for detecting the focus position (position in the optical axis direction) of a wafer as a photosensitive substrate are defined as position information of the peripheral portion of the wafer and movement position information of the wafer stage. Therefore, the exposure sequence of scanning from the outer side to the inner side of the wafer is possible without lowering the throughput. As a result, the defective shot area can be exposed without defocusing, and the exposure of the entire wafer can be position-controlled in the optical axis direction while alternately switching the scanning direction for each shot area. Therefore, the movement of the wafer stage or the mask stage can be minimized and a high throughput can be achieved.

A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. In this embodiment, a refraction-type projection optical system including a plurality of refraction lens elements is used as the projection optical system. Is assumed. However, it goes without saying that the present invention is not limited to this, and a reflection-refraction type projection optical system in which a refractive lens element and a reflective element (such as a concave mirror) are combined can be used.

FIG. 1 shows a projection exposure apparatus of the present embodiment. Illumination in a slit shape on the pattern surface (lower surface) of the reticle R is performed by exposure light IL from an exposure light source (not shown) and an illumination optical system in FIG. Region 1 is illuminated with a substantially uniform illuminance. The reticle R is held on the upper surface of the reticle holder 2 by a vacuum chuck, the reticle holder 2 is fixed on the reticle stage 3, and the reticle stage 3 is supported on the reticle guide 4 by an air guide or the like and is movable in the X direction. It has been placed.

The reticle stage 3 scans the reticle guide 4 at a constant speed in the + X direction or the -X direction by a linear motor system or the like during scanning exposure. That is, the scanning direction of the reticle R is the ± X direction in the left-right direction within the plane of the paper in FIG. Now, the movable mirror 5 is fixed to one end of the reticle stage 3 in the X direction, and the measurement laser beam Lbr from the reticle interferometer monitor unit 13 is projected thereon. Then, the reticle interferometer monitor unit 13 receives the beam reflected by the movable mirror 5 and successively measures the position change of the reticle stage 3 in the X direction. Reticle interferometer monitor unit 1
The position measurement result of No. 3 is supplied to the main control system 20 that controls the operation of the entire apparatus, and the main control system 20 controls the moving speed and the moving position of the reticle stage 3 via the reticle stage drive unit 14.

The reticle interferometer monitor unit 13 shown in FIG.
Shows only one axis in the X direction, a similar interferometer monitor is provided for the Y axis perpendicular to the plane of FIG. 1, and the positional change of the reticle stage 3 in the Y direction is also measured sequentially. There is. Further, the reticle stage drive unit 14 controls the position of the reticle stage 3 in the Y direction generated during scanning exposure based on the measurement result from the interferometer monitor unit in the Y axis direction.

An image of a part of the circuit pattern formed on the reticle R in the illumination area 1 is imaged as a slit-shaped exposure area 6 on the wafer W via the projection optical system PL. Here, the optical axis of the projection optical system PL is a surface defined by the X axis and the Y axis (the pattern surface of the reticle R and the surface of the wafer W).
It is assumed to be parallel to the Z axis which is perpendicular to. Then, the wafer W is held on the wafer holder 8 by a vacuum chuck, and the wafer holder 8 is placed on a Z leveling stage (including a driving unit) 10 as a correction mechanism of the exposure surface of the wafer W, and the Z leveling stage 10 is XY. Stage 1
1.

The Z leveling stage 10 adjusts the expansion and contraction amounts of, for example, three actuators and a Z stage that roughly positions the wafer W in the Z direction parallel to the optical axis of the projection optical system PL, and adjusts the expansion and contraction amounts of the three actuators. Of the Z leveling stage 10 and the XY stage 11 includes a leveling table for finely adjusting the position (focus position) and the tilt angle.
(And thus the wafer W) is positioned in a two-dimensional plane (XY plane) perpendicular to the optical axis of the projection optical system PL, and ± X
It has a function of scanning the Z leveling stage 10 in the direction.

A moving mirror 1 is mounted on the Z leveling stage 10.
2 is fixed, and the measuring laser beam LBw from the wafer interferometer monitor unit 15 is projected on the movable mirror 12 along each of the X direction and the Y direction. The beam reflected by the movable mirror 12 is received by the receiver in the wafer interferometer monitor unit 15, and the wafer interferometer monitor unit 15 successively measures the coordinate position of the Z leveling stage 10 (wafer W) in the XY plane. ing. The measurement result is supplied to the main control system 20, and the main control system 20 controls each operation of the XY stage 11 and the Z leveling stage 10 via the wafer stage drive unit 16.

Further, the main control system 20 controls the operation of the XY stage 11 via the wafer stage driving section 16 during scanning exposure to move the wafer W in the X direction (or -X direction) at a constant speed. In this case, assuming that the projection magnification of the projection optical system PL is β, the reticle R moves in the −X direction (or the X direction).
In synchronism with the scanning of the wafer W at the speed VR0,
The scanning is performed at the speed VW0 (= β · VR0) in the direction (or −X direction).

In the present embodiment, as a sensor for detecting the state of the exposed surface of the wafer W, an optical focus position detection system for autofocus (hereinafter referred to as "AF sensor").
To use. The AF sensor is composed of a light transmitting system 7a and a light receiving system 7b, and the detection illumination light AL from the light transmitting system 7a.
(Wavelength range where the resist on the wafer is practically difficult to be exposed)
Is projected as a slit image on the exposure surface of the wafer W in the exposure area 6 obliquely (for example, 10 ° or less with respect to the wafer surface) with respect to the optical axis of the projection optical system PL.

The reflected light from this slit image is received by the light receiving system 7b.
The reflected light from the wafer, which has been re-imaged as a slit image inside the slit portion of the vibrating slit plate and has passed through the slit of the vibrating slit plate, is photoelectrically converted by the photoelectric converter. This photoelectric conversion signal is synchronously detected by the drive signal of the vibrating slit plate in the light receiving system 7b, and the light receiving system 7b shifts the position of the surface of the exposure region 6 on the wafer W in the Z direction, that is, the best image formation of the projection optical system PL. A focus signal that linearly corresponds to the positional deviation of the wafer surface within a predetermined Z range with respect to the surface (focus position) is generated.

This focus signal is supplied to the main control system 20 and used for adjusting the position of the Z leveling stage 10 in the optical axis direction (Z direction) or adjusting the tilted state. In this case, the focus signal has a predetermined reference value (for example, zero) when the exposure surface of the wafer W matches the best image plane of the projection optical system PL within an allowable range of, for example, ± 0.1 μm. It shall be calibrated beforehand so that

By the way, an example of the detailed structure of the AF sensor is disclosed in, for example, Japanese Patent Application Laid-Open No. 60-168112 by the present applicant. Further, in the present invention, in order to improve the focus controllability on the wafer exposure surface during scanning exposure, the AF sensor (7a, 7b) is provided in a large number in a local area including a part of the exposure area 6 on the front side in the scanning direction. Measurement point (detection point)
An AF sensor of a so-called multipoint type pre-reading detection method (for example, Japanese Patent Laid-Open No. 6-283403 by the applicant of the present application) that detects a positional deviation (focus position) in the Z direction is used.

An input / output device (keyboard, display, etc.) 18 is connected to the main control system 20, and an operator can input various information via the input / output device 18. The information input here includes offset information of the focus signal of the AF sensor, which is found by test printing or the like. A lens controller 19 is connected to the main control system 20. The lens control unit 19 is disclosed in Japanese Patent Application Laid-Open No. 58-179834 and Japanese Patent Application Laid-Open No.
61-183928, JP 62-183522, JP 62-2
As disclosed in Japanese Patent No. 29838, changes in the position of the image plane of the projection optical system PL caused by changes in atmospheric pressure and changes in energy of exposure light absorbed in the projection optical system PL during exposure. Is calculated at any time, and the calculation result is supplied to the main control system 20.

Next, referring to FIG. 2, a control system using a multipoint autofocus sensor will be described. In FIG. 2, in the exposure area 6, two rows (L0a, L0b) of detection rows in which eight detection points are arranged in the non-scanning direction (Y direction) are arranged in the scanning direction (X direction) for servo control. A focus sensor AD0 is arranged. Further, in both the outside of the exposure area 6 in the scanning direction, 8 in the Y direction, respectively.
Pre-reading focus sensors AD1a and AD1b having detection rows L1a and L1b in which individual detection points are arranged are arranged. In FIG. 2, each of the short diagonal lines shown on the wafer W represents a slit image forming each detection point of the focus sensor.

Now, assuming that the scanning exposure direction is the direction of the arrow in FIG. 2 (X direction), the sensor AD1a located above the exposure area 6 in FIG. 2 is selected as the preread sensor. By the way, in this embodiment, focus control (Z
In addition to position adjustment), tilt control in both the non-scanning direction and the scanning direction is also performed. When these focus control and tilt control are actually performed, the above-mentioned sensors AD0, AD1a, AD1
Each detection sequence L0a, L0b, L1a, L included in each b
It is also possible to select and use only focus signals detected from a plurality of preset detection points from 1b.

In this embodiment, focus control and two directions (X
In order to perform tilt control around the axis and around the Y-axis, not only the focus sensor AD0 for servo control including the two detection rows L0a and L0b in the exposure area 6 shown in FIG. 2 but also another detection row ( It is desirable to select and use at least one detection line from L1a, L1b, etc.) or at least one detection point in another detection line.

Each focus signal from the servo control sensor AD0 is input to a calculation circuit 100, which calculates the control target surface Zt and the actual wafer surface Zp.
The difference ΔZf between the positions in the Z direction is calculated, and the result is sent to the main control system 20. Generally, since the wafer has irregularities, the calculation circuit 100 uses the least squares method based on the focus information detected at each of a plurality of detection points in the servo control sensor AD0 to approximate the wafer surface. Is calculated, and it is effective to perform a calculation process to obtain the difference ΔZf between the approximate plane and the control target surface Zt.

The focus sensor AD for prefetching
Two detection columns L also shown from 1a (AD1b)
1a (L2a), L1b (L2b), or more sensors are selected and used. The focus signal detected at each of the detection points from the focus sensor AD1a (AD1b) for prefetching is calculated by the calculation circuit 11 in FIG.
Input to 0. Then, the calculation circuit 110 sends the information about the wafer flatness to the main control system 20 prior to the exposure. As a result, the main control system 20 causes the calculation circuit 110 to operate.
The response delay when controlling each of the three actuators 22 that drive the Z leveling stage in response to a signal (ΔZf) from It can be easily avoided based on the wafer flatness information from 110.

Then, when the scanning exposure by the exposure area 6 is completed for one shot area on the wafer W, as shown in FIG.
The inner reticle stage 3 reaches almost one end side of the movement stroke in the X direction, and the XY stage 11 performs stepping for exposure to the adjacent (or next) shot area. At that time, the scanning movement direction of the XY stage 11 is opposite to that of the previous shot area with respect to the next shot area. Therefore, the sensor for pre-reading is provided from the sensor AD1a of the upper detection row L1a in FIG. , The sensor AD1b of the detection row L1b on the lower side of the exposure area 6 is switched to be selected.

In this way, the wafer W is exposed before the exposure depending on the moving direction (+ X direction or −X direction) of the wafer W during the scanning exposure.
By using the side capable of detecting the surface position of as a sensor for pre-reading, it becomes possible to perform exposure while alternately switching the scanning directions of all shot areas on the wafer W. FIG. 3 shows an example of the exposure sequence at that time, and a plurality of shot areas SA shown on the wafer W in FIG.
For each of the n, it is possible to set the scanning directions alternately as indicated by the arrows. In other words,
During the exposure processing of one wafer W, the reticle stage 3
This means that the idle scanning is unnecessary for the movement in the X direction. That is, during the scanning exposure process, the reticle stage 3
When a scan is moved once in the + X direction, one shot area is always exposed, and once a scan movement is performed in the -X direction, the adjacent (next) shot area is always exposed. For this reason, useless idle scanning of the reticle stage 3 is eliminated, and 1
The exposure time of the wafers W is shortened, and the throughput is improved.

In the above-described exposure apparatus, since the read-ahead sensors AD1a and AD1b are alternately switched to expose all the shot areas of the wafer W while alternately switching the scanning directions, the wafer W is exposed from the outside to the inside. An exposure sequence in which scanning exposure is performed is essential. The focus control (Z position adjustment) when scanning and exposing the wafer W from the outer side to the inner side will be described below with reference to FIG.

As is apparent from the state of FIG. 3, the shot areas SA1 to SA5 and the like are shot areas partially missing by the circular edge of the wafer W, ie, missing shot areas. When the shot area, which is the missing shot area, is scanned and exposed from the outer side to the inner side of the wafer W, only the detection point that has reached the edge of the wafer W and has been placed on the wafer W among the plurality of detection points of the pre-reading sensor. Select and use. For example, as shown in FIG.
When scanning and exposing A1 in the direction of the arrow in the figure, the FP mounted on the wafer W among the detection points FP1 to FP8 of the prefetch sensor
7 and FP8 are selected and focus control is performed. Then, as the number of detection points placed on the wafer W during scanning exposure increases, the number of selected detection points also increases. Similarly, in the shot area SA5, the FP1 mounted on the wafer W is
And FP2 are selected to perform focus control. Each of the detection points FP1 to FP8 shown in FIG. 3 corresponds to one of the detection rows composed of the detection points with short diagonal lines shown on the wafer W in FIG. Therefore, when the detection points FP1 to FP8 shown in FIG. 3 are used as the detection points for prefetching, they correspond to the detection row L1a or L1b in FIG.

Now, the memory 17 will be described in more detail with reference to the conceptual diagram for explaining the selection of the detection points of the pre-reading sensor shown in FIG. The moving position information of the stage 11 is stored in advance. Therefore, the main control system 20 detects the detection points FP1 to FP1 of the pre-reading sensor mounted on the wafer W based on the edge position information of the wafer W and the position information of the XY stage 11 stored in the memory 17 as shown in FIG. FP8 is sequentially selected. That is, the number of detection points located on the wafer W during scanning exposure increases, and all the detection points located on the wafer W are sequentially selected. This makes it possible to realize more reliable and highly accurate focus control. The selected detection points (in the positional relationship between the detection row of the pre-reading sensor and the wafer W shown in FIG. 3 are FP7 and F).
P8) is used to detect the focus position (position in the optical axis direction) or the tilted state of the wafer W. The main control system 20 is
Based on the detection result, the position of the Z leveling stage 10 in the optical axis direction or the tilted state is adjusted. That is, the focus control is performed without being selected for the detection points that have not reached the position intersecting the edge of the wafer W. As a result, the wafer W
Even when the scanning exposure is performed from the outside to the inside, the exposure can be performed without defocusing, and the defective shot area can be effectively used.

Since the positions where all the detection points of the pre-reading sensor are placed on the wafer W are known in advance, the main control system 20 determines the focus signal for the wafer flatness measurement by the pre-reading after all the detection points are placed. Focusing may be started and focus control and tilt control may be performed. By the way, in the above-described embodiments, the case where the refraction system is used as the projection optical system has been described, but the present invention is the same even when the reflection type projection optical system or the catadioptric projection optical system is used as the projection optical system. Can adapt to. Further, scanning exposure can be applied to contact exposure and proximity exposure that do not require a projection optical system. Furthermore, in the above-described embodiment, not only focus control but also tilt control in two directions is performed, but the present invention can be applied to focus control alone.
In this case, the number of sensors used can be small. It is also possible to openly control the attitude of the Z leveling table 10 by using only the wafer flatness information from the pre-reading sensors AD1a and AD1b without using the servo control sensor AD0.

[0030]

According to the present invention, a plurality of detection points for detecting the position of the photosensitive substrate such as a wafer in the optical axis direction, that is, the position in the Z direction perpendicular to the surface are used as the position information of the peripheral portion of the wafer and the wafer stage. The position of the wafer W in the direction of the optical axis or the tilted state can be accurately detected by selectively using it based on the movement position information of the wafer W, so that an exposure sequence for scanning from the outer side to the inner side of the wafer is possible. did. This makes it possible to perform position control or tilt control in the optical axis direction while alternately switching the scanning direction for the exposure of the entire wafer for each shot area, and the total amount of movement of the wafer stage or mask stage with respect to one photosensitive substrate. Can be minimized and high throughput can be achieved. Further, since there is no dummy scan of each stage, it is possible to suppress unnecessary behavior in the reaction force generated in the exposure apparatus and to minimize the heat generation of the drive motor for driving each stage. It becomes possible to

[Brief description of drawings]

FIG. 1 is a view showing the arrangement of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of focus / tilt control according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of an exposure sequence according to the present invention.

FIG. 4 is a conceptual diagram for explaining selection of detection points of a prefetch sensor.

[Explanation of symbols]

 1 ... Slit-shaped illumination area R ... Reticle W ... Wafer PL ... Projection optical system 3 ... Reticle stage 7a ... AF sensor light-transmitting system 7b ... AF sensor light-receiving system 10 ... Z leveling stage 11 ... XY stage 20 ... Main control System 22 ... Actuator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/30 520A 525X

Claims (5)

[Claims] 1. A pattern of the mask is obtained by scanning a mask having a transfer pattern formed on an illumination area having a predetermined shape in a predetermined direction and scanning a sensitive substrate in the predetermined direction on the illumination area. An image on the sensitive substrate, wherein after the mask stage on which the mask is placed and the substrate stage on which the sensitive substrate is placed are aligned in a predetermined positional relationship, An exposing step of scanning and exposing toward the inside, and a detecting step of detecting the focus position of the sensitive substrate at each of a plurality of detecting points arranged in the non-scanning direction during the exposing step, wherein the detecting step is Selecting the plurality of detection points based on position information of a peripheral portion of the sensitive substrate intersecting with the scanning direction and movement position information of the substrate stage. An exposure method characterized by the following. 2. The exposure method according to claim 1, wherein in the selecting step, a detection point located on the sensitive substrate is selected from the plurality of detection points. 3. The exposure method according to claim 1, wherein the plurality of detection points are positioned before and after the illumination area with respect to the scanning direction. 4. The pattern of the mask is obtained by scanning a mask having a transfer pattern formed on an illumination area having a predetermined shape in a predetermined direction and scanning a sensitive substrate in the predetermined direction on the illumination area. A step of exposing the image on the sensitive substrate by aligning the mask and the sensitive substrate in a predetermined positional relationship, and then performing scanning exposure from the outer side to the inner side of the sensitive substrate, During the exposure step, there is a control step of detecting the focus position of the sensitive substrate at a plurality of detection points arranged in the non-scanning direction, and controlling the focus state of the pattern image with respect to the sensitive substrate based on the detection result. The control step may start the detection operation or the control operation when at least one of the plurality of detection points reaches the inside of the peripheral portion of the sensitive substrate. A characteristic exposure method. 5. The exposure method according to claim 1, wherein the detecting step is a step of detecting an inclined state of the sensitive substrate.