JPH0982636A - Projection exposure device and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a high follow-up property to a sensitive substrate having less irregularities, while effecting a stable focusing to a sensitive substrate of high irregularities without breaking the control. SOLUTION: In a judging part 28, whether respective deviations of inclination amounts around X axis and Y axis are within allowance range or not are judged according to θx', θy', z' and θx, θy, z. Next, while the judging part 28 is making an affirmative judgement, high precious focus and levelling control are performed according to the θx, θy, z and θx', θy', z' by a controller 31. On the other hand, while the judging part 28 is making a negative judgement, the focus control is performed according the θx, θy, z and θx', θy', z' while keeping the inclination constant.

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 and a projection exposure method, and more particularly to a projection exposure apparatus characterized by a focusing mechanism control method and a projection exposure suitable for application to this projection exposure apparatus. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, when a semiconductor device or the like is manufactured by using a photolithography technique, a wafer or glass coated with a photosensitive material such as a photoresist through a projection optical system of a pattern image of a mask or reticle. A projection exposure apparatus that exposes light onto a photosensitive substrate such as a substrate is used. In general, a projection exposure apparatus uses a projection optical system having a large numerical aperture (NA) and a shallow depth of focus. Therefore, in order to transfer a fine circuit pattern at a high resolution, the surface of the photosensitive substrate is not covered by the projection optical system. A mechanism for adjusting to the image plane is required. Therefore, the projection exposure apparatus has a focusing mechanism for bringing the surface of the photosensitive substrate into the range of the depth of focus of the projection optical system. This is a focus / leveling detection system that detects the position and inclination of the photosensitive substrate surface in the optical axis direction (Z direction) of the projection optical system, and the position and orientation of the photosensitive substrate surface based on the detected height and inclination. It is composed of an adjusting mechanism for adjusting (hereinafter referred to as "ZT stage").

Conventionally, a so-called step-and-repeat type stepper has been mainly used, but recently, a chip of a semiconductor element tends to be large, and a pattern having a larger area is projected and exposed on a photosensitive substrate. Is required. Therefore, by scanning the reticle and the photosensitive substrate in synchronization with the projection optical system, a so-called step-and-scan projection that enables exposure to a shot area wider than the effective exposure field of the projection optical system. Exposure equipment has been developed. The pattern of the reticle is illuminated as a slit-shaped area by the light defined by the blind of the illumination system. This area is the "lighting field"
Call. On the other hand, an area illuminated on the photosensitive substrate, that is, an area conjugate with the illumination field via the projection optical system is called an “exposure field”. For these terms, the large area onto which the entire pattern image of the reticle is sequentially projected is called the “exposure area”.

In such a step-and-scan projection exposure apparatus, in order to expose a certain area on the surface of the photosensitive substrate, this area should be exposed while the positional relationship between the photosensitive substrate and the reticle is synchronized. It is necessary to move at a constant speed at a speed commensurate with the amount of energy. For this reason, the stage (XY stage) on which the photosensitive substrate is mounted starts running before the area to be exposed and is synchronized with the stage on which the reticle is placed during the running, and then the exposure area on the photosensitive substrate is changed. The procedure includes performing exposure when the exposure position is reached. As for the focusing operation, as part of this procedure, the focusing position is searched and the photosensitive substrate surface is moved to that position at the start of running, and then the focusing operation is performed by following the moving photosensitive substrate surface. Is done.
This focusing operation is usually performed in the optical axis direction of the projection optical system (Z direction).
And the so-called leveling operation, which is the focusing operation in the tilting directions around the X and Y axes, are performed simultaneously, and thereby the exposure field on the surface of the photosensitive substrate and the image plane of the projection optical system are formed. The difference between is minimized.

[0005]

In the step-and-scan projection exposure apparatus, since the photosensitive substrate to be exposed moves during the exposure, the image plane of the projection optical system and the surface of the photosensitive substrate are sequentially exposed. The control is repeated to bring the field closer. Further, since the exposure field is narrower than that of a batch exposure type projection exposure apparatus such as a stepper, when performing such control, a high speed is required as the drive speed of the ZT stage.

Here, regarding the driving speed of the ZT stage, when the unevenness of the surface of the photosensitive substrate is severe, for example, the width of the exposure field in the scanning direction is 8 mm, and the difference in the unevenness of the surface of the photosensitive substrate between them is 0. An example will be described for the case of 0.5 μm. In this case, since there is a height difference of 0.5 μm during 8 mm scanning, the inclination angle is 0.5 μm / 8 mm = about 62 μrad. Here, the scanning speed of the photosensitive substrate is 80 mm /
If it is sec, the time required for the photosensitive substrate to pass through the exposure field is 0.1 sec, which is 62 μrad.
The leveling operation must be performed at a speed of /0.1 sec = 620 μrad / sec. The equivalent distance between the fulcrums (pivots) of the ZT stage that is driven to perform leveling is a maximum of 2 for an 8-inch wafer stage.
Since it is about 50 mm, the driving speed in the Z direction at the pivot position is 250 mm × 620 μrad / sec.
= 155 μm / sec. On the other hand, the Z-direction control amount for focus control is 0.5 μm / 0.1 sec.
It is sufficient to allow for c = 5 μm / sec. Therefore, the ratio of the control amounts in the leveling and the focus operation is 30:
It will be about 1.

This ratio restricts the relationship between the resolution of the speed command and the maximum speed in the speed control system within a certain range. A 12-bit D / A converter is usually used to give a speed command to an analog-controlled speed control system. In this case, the ratio between the resolution of the speed command value and the maximum value of the speed command value is 1: 2048. It is usual to design the speed command value to be the value obtained by multiplying the resolution of the focus detection system by the servo gain of the position servo system.
Therefore, when the resolution of the focus detection system is 0.01 μm and the gain of 10 (1 / sec) is considered, the resolution of the speed command value is 0.1 μm / sec, and the maximum value of the speed command is about 205 μm / sec.

Under this condition, 80 μrad (0.64
In the case of a photosensitive substrate having irregularities exceeding (μm / 8 mm), the Z-direction drive speed at the fulcrum position reaches the limit, and the decoupling control based on the linear control fails. As a result, not only in the tilt direction but also in the Z direction, a large defocus occurs, which is a cause of disturbing the image formation.

The present invention has been made under the above circumstances, and an object thereof is to ensure high followability for a photosensitive substrate having few irregularities and control for a photosensitive substrate having a large degree of irregularities. It is an object of the present invention to provide a projection exposure apparatus and a projection exposure method capable of performing a stable focusing operation without causing a failure.

[0010]

According to a first aspect of the present invention, a mask (R) on which a pattern is formed is illuminated and an image of a part (1) of the pattern of the mask is projected by a projection optical system (P).
L), the mask (R) and the photosensitive substrate (W) are projected onto the exposure field (6) on the photosensitive substrate (W) mounted on the substrate table (10). A projection exposure apparatus for scanning in synchronization with a system (PL), the exposure field (6) on the surface of the photosensitive substrate.
First detecting means (7A, 7B) for detecting the position of the projection optical system (PL) in the optical axis direction within the inside; and the position of the surface of the photosensitive substrate in the optical axis direction and the inclination with respect to the optical axis orthogonal plane. Adjusting means (60) for adjusting; a first position (z) of the exposure field (6) on the surface of the photosensitive substrate in the optical axis direction, based on detection information from the first detecting means (7A, 7B). And a calculation means (2) for calculating a first inclination amount (θx, θy) of the exposure field from the plane orthogonal to the optical axis.
7) and; a target position (z ′) and a target tilt amount (θx ′, θy ′) in the optical axis direction of the exposure field on the surface of the photosensitive substrate.
A target value output means (25) for outputting the difference between the target position and the first position, based on the target value from the target value output means (25) and the calculation result of the calculation means (27). Determination of whether or not the command value of the control amount for the adjusting means (60) determined based on at least one of the difference between the target inclination amount and the first inclination amount is within the control range of the adjusting means Means (28); and an exposure field (6) on the surface of the photosensitive substrate based on the target position and the target tilt amount and the first position and the first tilt amount while the judgment means makes an affirmative judgment. So as to match the image plane of the projection optical system (PL).
0) is controlled, and the inclination of the surface of the photosensitive substrate (W) is kept constant while the determination unit makes a negative determination, the surface of the photosensitive substrate is determined based on the target position and the first position. Control means (29, 31, 32) for controlling the adjusting means so that the position of the exposure field in the optical axis direction coincides with the center of the image plane of the projection optical system in the optical axis direction.

According to this, when the substrate table is scanned for exposure, the positions of, for example, three or more points in the exposure field on the surface of the photosensitive substrate in the optical axis direction of the projection optical system are detected by the first detecting means. Based on the detection information from the first detecting means, the arithmetic means detects the first position in the optical axis direction of the exposure field on the surface of the photosensitive substrate and the first inclination of the exposure field from the plane orthogonal to the optical axis based on the detection information from the first detecting means. Calculate the amount. At this time, the target value output means outputs the target position and the target tilt amount in the optical axis direction of the exposure field on the surface of the photosensitive substrate. The determination means is based on at least one of the difference between the target position and the first position and the difference between the target tilt amount and the first position, based on the target value from the target value output means and the calculation result of the calculation means. It is determined whether or not the command value of the control amount for the adjusting means determined by the above is within the control range of the adjusting means. Here, when the unevenness of the surface of the photosensitive substrate is small, a command of the control amount to the adjusting means determined based on at least one of the difference between the target position and the first position and the difference between the target tilt amount and the first tilt amount. Since the value is within the control range of the adjusting means (in this case, the inclination amount deviation, which is the difference between the target inclination amount and the first inclination amount, is within the allowable range), the determining means makes an affirmative determination to determine the surface of the photosensitive substrate. When the degree of unevenness is severe, the command value of the control amount to the adjusting means is out of the control range of the adjusting means (in this case, the deviation of the tilt amount is out of the allowable range), and therefore the determining means makes a negative determination. become.

Then, while the judgment means makes an affirmative judgment, that is, while the area with less unevenness on the surface of the photosensitive substrate is in the exposure field, the control means controls the target value from the target value output means and the calculation means. Based on the calculation result, the adjusting means is controlled so that the exposure field on the surface of the photosensitive substrate coincides with the image plane of the projection optical system. As a result, the position of the surface of the photosensitive substrate in the optical axis direction and the inclination with respect to the optical axis direction are adjusted by the adjusting means, and highly accurate focus and leveling control is performed.

On the other hand, while the determination means of the control means makes a negative determination, that is, while the region of the surface of the photosensitive substrate where the unevenness is severe is in the exposure field, the control means keeps the inclination of the photosensitive substrate constant. While maintaining the target value output means, the position in the optical axis direction of the exposure field on the surface of the photosensitive substrate is projected based on the target position in the optical axis direction of the exposure field on the surface of the photosensitive substrate and the first position calculated by the calculating means. The adjusting means is controlled so as to coincide with the center of the image plane of the optical system in the optical axis direction. As a result, the focus control of the surface of the photosensitive substrate is performed by the adjusting means. In this case, since the inclination of the surface of the photosensitive substrate is maintained constant, a stable focusing operation is performed without causing control failure.

In this case, as in the second aspect of the present invention, the second detecting means (for detecting the second inclination amount (Θx, Θy) from the plane orthogonal to the optical axis of the substrate table (10) ( 21B, 22B, 23B, 30) are further provided, and the target value output means (25) is detected by the second detection means when the determination result of the determination means (28) changes from a positive determination to a negative determination. Alternatively, the second inclination amount (Θx, Θy) may be sent to the control means. With this configuration, the control unit adjusts the inclination amount detected by the second detection unit to match the target value of the inclination amount from the target value output unit while the determination unit makes a negative determination. Control means (60). This keeps the inclination of the surface of the photosensitive substrate (W) constant.

In this case, when the judgment of the judgment means is changed from the negative judgment to the positive judgment, the control means and the first detection means start the focus and leveling control. In the determination circuit, the first axis and the second axis
Both deviations of the tilt amount about the axis are within the allowable range, deviations of the tilt amount about the first axis and the second axis are both outside the allowable range, and other deviations of the tilt amount about the first axis and the second axis. It is also possible to determine that one of the two is outside the allowable range.

Here, as the command value of the control amount, a speed command value for the adjusting means (60) may be used as in the invention of claim 3, or a displacement command value may be used. .

According to a fourth aspect of the present invention, a mask (R) on which a pattern is formed is illuminated, and an image of a part (1) of the pattern of the mask is projected on a substrate table (PL) via a projection optical system (PL). 10) A projection exposure apparatus which scans the mask and the photosensitive substrate in synchronization with the projection optical system in a state of being projected on an exposure field (6) on a photosensitive substrate (W) placed on the substrate. First detecting means (7A, 7B) for detecting the position of the projection optical system in the optical axis direction within the exposure field (6) of the photosensitive substrate surface; and the position of the photosensitive substrate surface in the optical axis direction. And adjusting means (60) for adjusting the inclination from a plane orthogonal to the optical axis; and the exposure field (6) on the surface of the photosensitive substrate based on the detection information from the first detecting means (7A, 7B). ) The first position (z) in the optical axis direction and Computing means (27) for calculating a first tilt amount (θx, θy) from a plane orthogonal to the optical axis; and a target position (z ′) of the exposure field (6) on the surface of the photosensitive substrate in the optical axis direction. And a target value output means (25) for outputting a target tilt amount (θx ′, θy ′); a second tilt amount (θ) from a surface of the substrate table (10) orthogonal to the optical axis.
x ', Θy') second detection means (21B, 22)
B, 23B, 30); and based on the target value from the target value output means and the calculation result of the calculation means, the difference between the target position and the first position, the target tilt amount, and the first tilt amount. Determination means (28) for determining whether or not the command value of the control amount for the adjusting means (60) determined based on at least one of the difference between and is within the control range of the adjusting means.
A first control mode for controlling the adjusting means (60) based on the target position and the target tilt amount and the first position and the first tilt amount according to the judgment result of the judging means; and the photosensitive substrate. The position in the optical axis direction of the exposure field on the surface of the photosensitive substrate coincides with the center of the image plane of the projection optical system in the optical axis direction based on the target position and the first position while keeping the surface inclination constant. Control means for switching the second control mode for controlling the adjusting means so that
31 and 32).

According to this, when the substrate table is scanned for exposure, the positions of, for example, three or more points in the exposure field on the surface of the photosensitive substrate in the optical axis direction of the projection optical system are detected by the first detecting means. Based on the detection information from the first detecting means, the arithmetic means detects the first position in the optical axis direction of the exposure field on the surface of the photosensitive substrate and the first inclination of the exposure field from the plane orthogonal to the optical axis based on the detection information from the first detecting means. Calculate the amount. At this time, the target value output means outputs the target position and the target tilt amount in the optical axis direction of the exposure field on the surface of the photosensitive substrate. The second detection means detects the second tilt amount from the plane orthogonal to the optical axis of the substrate table. The determination means, based on the target value from the target value output means and the calculation result of the calculation means, based on at least one of the difference between the target position and the first position and the difference between the target inclination amount and the first inclination amount. It is determined whether or not the command value of the control amount for the determined adjusting means is within the control range of the adjusting means. Then, the control means controls the adjusting means based on the target position and the target inclination amount and the first position and the first inclination amount according to the determination result of the determination means, and the inclination of the photosensitive substrate surface. Based on the target position and the first position while keeping constant, the adjusting means is controlled so that the position of the exposure field on the surface of the photosensitive substrate in the optical axis direction coincides with the center of the image plane of the projection optical system in the optical axis direction. Switch to the second control mode.

When the control mode is switched to the first control mode, the adjusting means adjusts the position of the surface of the photosensitive substrate in the optical axis direction and the inclination with respect to the optical axis direction, thereby performing highly accurate focus and leveling control. Further, when the second control mode is switched, the focus control of the surface of the photosensitive substrate is performed by the adjusting means. In this case, since the inclination of the photosensitive substrate is kept constant, a stable focusing operation is performed without any failure in control.

In this case, the first tilt amount is the first X tilt amount (θx) in the X-axis direction which is the scanning direction of the photosensitive substrate on the surface of the photosensitive substrate, and the X-axis. Including a first Y-tilt amount (θy) in the Y-axis direction that is orthogonal to the second Y-tilt amount, the second tilt amount is the second X-tilt amount (Θx) in the X-axis direction of the substrate table (10) and the second Y-tilt amount in the Y-axis direction. The target inclination amount may include (Θy) and the target X inclination amount (θx ′) in the X-axis direction and the target Y inclination amount (θy ′) in the Y-axis direction. Further, the determination means (28) has the target position (z ′) as the determination condition, as in the invention described in claim 6.
And the first position (z), the target X tilt amount (θx ') and the first
Adjusting means (60) based on the difference between the X tilt amount (θx) and the difference between the target Y tilt amount (θy ′) and the first Y tilt amount (θy).
It may have a first condition for determining whether or not the speed command value for the speed exceeds the first speed. In this case, the control means (29, 31, 3) as in the invention according to claim 7 is provided.
In 2), using the first condition as a judgment condition, it is possible to switch to the first control mode when the first condition is not satisfied and to switch to the second control mode when the first condition is satisfied.

Further, in the above-mentioned case, as in the invention described in claim 8, the judging means (28) sets the difference between the target position (z ') and the first position (z) and the target X as the judgment condition. The second condition for determining whether or not the speed command value for the adjusting means (60) based on the difference between the tilt amount (θx ′) and the first X tilt amount (θx) exceeds the second speed, and the target position ( z ′) and the first position (z) and the target Y tilt amount (θ
y ') and a third condition for judging whether or not the speed command value to the adjusting means (60) based on the difference between the first Y tilt amount (θy) exceeds the third speed. Is desirable. In this case, various control modes can be switched using the first condition, the second condition, and the third condition. For example, as in the invention described in claim 9, the control means (29, 3)
1, 32), if the first and second conditions are satisfied and the third condition is not satisfied, the target position, the target X tilt amount, and the target Y
Based on the tilt amount and the first position, the second X tilt amount, and the first Y tilt amount, switching to the third control mode for controlling the adjusting means, and when the first condition is satisfied and the second condition is not satisfied, the target position, It is possible to switch to the fourth control mode in which the adjusting means is controlled based on the target X tilt amount, the target Y tilt amount, and the first position, the first X tilt amount, and the second Y tilt amount. In the third control mode, the focus control and the leveling control in the Y direction of the surface of the photosensitive substrate are performed while the amount of inclination of the photosensitive substrate in the X direction is kept constant by the adjusting means, and the fourth mode. In the case of, the focus control and the X-direction of the surface of the photosensitive substrate are performed while the tilt amount of the photosensitive substrate in the Y direction is kept constant by the adjusting means.
Directional leveling control is performed. In these cases, X
Since the tilt amount in the direction or the tilt amount in the Y direction is maintained constant, the control does not break down.

According to a tenth aspect of the present invention, a mask (R) on which a pattern is formed is illuminated, and an image (1) of a part of the pattern of the mask is projected through a projection optical system (PL) onto a substrate table (. 10) A projection exposure apparatus that scans the mask and the photosensitive substrate in synchronization with the projection optical system in a state where the mask and the photosensitive substrate are projected onto a predetermined exposure field (6) on the photosensitive substrate (W) mounted on the substrate. In the exposure field on the surface of the photosensitive substrate, the first optical axis direction of the projection optical system.
A first detector (7A, 7B, 27) for detecting a position (z) and a first tilt amount (θx) from a plane orthogonal to the optical axis.
And; adjusting means (6) for adjusting the position of the substrate table in the optical axis direction and the amount of inclination from a plane orthogonal to the optical axis.
0) and; second detection means (21B, 22) for detecting a second tilt amount from the surface of the substrate table orthogonal to the optical axis.
B, 23B, 30); and a target position (z) in the direction of the optical axis of the exposure field (6) on the surface of the photosensitive substrate and a target inclination amount (θx ′, θy ′) from a plane orthogonal to the optical axis. Target value output means (25) for outputting; the first position and the first position
Based on the tilt amount and the target position and the target tilt amount,
The first tilt amount (θx, θy) or the second tilt amount (θ
switching means (3 for switching and outputting either x or Θy)
2) and; control means (29, 3) for controlling the adjusting means based on either the first tilt amount or the second tilt amount, the first position, the target position and the target tilt amount.
1).

According to this, when the substrate table is scanned for exposure, the first detection unit causes the first detection unit to be orthogonal to the first position in the optical axis direction of the projection optical system in the exposure field on the surface of the photosensitive substrate and the optical axis. The first tilt amount from the surface is detected.
Further, the second detecting means detects the second tilt amount from the plane orthogonal to the optical axis of the substrate table. At this time, the target value output means outputs the target position and the target tilt amount in the optical axis direction of the exposure field on the surface of the photosensitive substrate. The switching means switches and outputs either the first tilt amount or the second tilt amount based on the first position and the first tilt amount and the target position and the target tilt amount. Then, the control means controls the adjusting means based on either the first tilt amount or the second tilt amount, the first position, the target position and the target tilt amount.

In this case, as in the invention described in claim 11, for example, the first detection unit includes a plurality of sensors (71 to 7n) for obtaining the position in the optical axis direction within the exposure field on the surface of the photosensitive substrate. , A calculation unit (27) that calculates the first position and the first inclination amount based on the detection positions from the plurality of sensors, and the second detection unit is the substrate table (10). ) Multiple encoders (21B, 22B, 23B) for obtaining the position in the optical axis direction
And a coordinate conversion unit (30) that calculates the tilt amount of the substrate table from the encoder.

In each of the above inventions, a second target value (for example, Θx ', Θy') may be set in addition to the first target value, and the actual amount of inclination is set as the second target value. It is also possible to set a target value that corresponds to a deviation in the amount of inclination that is much smaller than the deviation, and in such a case, leveling control that does not cause a failure in control is also possible. In addition,
In this case, it is desirable to change the second target value according to how much the deviation in inclination exceeds the allowable range.

According to a twelfth aspect of the present invention, a mask (R) having a pattern formed thereon is illuminated, and an image of a part (1) of the pattern of the mask is placed on a substrate table via a projection optical system. Exposure field (6) on the exposed photosensitive substrate (W)
A projection exposure method for scanning the mask and the photosensitive substrate in synchronization with the projection optical system (PL) in a state of being projected onto a target surface, the target position in the optical axis direction of an exposure field on the surface of the photosensitive substrate. (Z ') and the target tilt amount (θx',
a first step of outputting θy ′); a second step of detecting the position of the projection optical system in the optical axis direction within the exposure field (6) on the surface of the photosensitive substrate; and a result detected in the second step. And a third step of calculating a first position (z) of the exposure field on the surface of the photosensitive substrate in the optical axis direction and a first tilt amount (θx, θy) of the exposure field from the plane orthogonal to the optical axis, Controlling the position of the photosensitive substrate in the optical axis direction and the inclination from the plane orthogonal to the optical axis, which is determined based on at least one of the difference between the target position and the first position and the difference between the target inclination amount and the first inclination amount. A fourth step of determining whether or not the amount is within a predetermined control range; if the determination is affirmative, the photosensitive substrate surface is based on the target position and the target tilt amount and the first position and the first tilt amount. Exposure field coincides with the image plane of the projection optics The position / orientation of the photosensitive substrate is controlled as described above, and if a negative determination is made, based on the target position and the first position while keeping the inclination of the surface of the photosensitive substrate constant, the direction of the optical axis of the exposure field is changed. A fifth step of controlling the position of the photosensitive substrate so that the position coincides with the center of the image plane of the projection optical system in the optical axis direction.

According to this, the target position and the target tilt amount in the optical axis direction of the exposure field on the surface of the photosensitive substrate are output,
Further, the position of the projection optical system in the optical axis direction within the exposure field on the surface of the photosensitive substrate is detected. Next, based on the detected result, the first field in the optical axis direction of the exposure field on the photosensitive substrate surface is
The first tilt amount of the exposure field from the position and the plane orthogonal to the optical axis is calculated. Then, the control amount of the position of the photosensitive substrate in the optical axis direction and the inclination from the plane orthogonal to the optical axis, which is determined based on the difference between the target position and the first position and the difference between the target inclination amount and the first inclination amount, is predetermined. It is determined whether it is within the range.

Here, when the unevenness of the surface of the photosensitive substrate is small, the difference between the target position and the first position and the target tilt amount and the first position.
The control amount of the tilt from the optical axis direction position of the photosensitive substrate and the optical axis orthogonal plane, which is determined based on at least one of the differences from the tilt amount, falls within the control range (in this case, the target tilt amount and the first tilt amount). The inclination amount deviation, which is the difference, is within the allowable range), so if a positive determination is made and the degree of unevenness on the surface of the photosensitive substrate is severe, the control amount is outside the control range (in this case, the inclination amount deviation is within the allowable range). Outside), so a negative decision is made.

Then, if the determination is affirmative, based on the target position and the target tilt amount and the first position and the first tilt amount, the exposure field on the surface of the photosensitive substrate coincides with the image plane of the projection optical system. The position and orientation of is controlled. As a result, highly accurate focus and leveling control is performed. On the other hand, if the determination is negative, the position of the exposure field in the optical axis direction is the optical axis direction of the projection optical system based on the target position and the first position while keeping the inclination of the photosensitive substrate surface constant. The position of the photosensitive substrate is controlled so as to coincide with the center. As a result, focus control of the surface of the photosensitive substrate is performed. In this case, since the inclination of the surface of the photosensitive substrate is maintained constant, a stable focusing operation is performed without causing control failure.

According to a thirteenth aspect of the present invention, in the projection exposure method according to the twelfth aspect, the substrate table (1
0) second tilt amount (Θx, Θy) from the plane orthogonal to the optical axis
Further including a sixth step of detecting, when the determination result in the fourth step is changed from a positive determination to a negative determination, in the fifth step, the attitude of the photosensitive substrate is determined based on the second tilt amount. It is characterized by keeping it constant. According to this, control is performed so that the second tilt amount matches the target value of the tilt amount, and the tilt of the surface of the photosensitive substrate is kept constant.

Here, as the control amount, the control amount according to claim 14 is used.
As in the invention described in (1), a speed command value for controlling at least one of the position and orientation of the photosensitive substrate may be used,
Alternatively, a displacement command value may be used.

In a fifteenth aspect of the present invention, a mask (R) on which a pattern is formed is illuminated, and an image (1) of a part of the pattern of the mask is projected through a projection optical system (PL) onto a substrate table (PL). 10) A projection exposure method for scanning the mask and the photosensitive substrate in synchronization with the projection optical system in a state where they are projected onto a predetermined exposure field (6) on the photosensitive substrate (W) placed on A first step of outputting a target position (z ′) in the optical axis direction of an exposure field on the surface of the photosensitive substrate and a target inclination amount (θx ′, θy ′) from a plane orthogonal to the optical axis; A first position (z) in the optical axis direction of the projection optical system within an exposure field (6) on the surface of the photosensitive substrate and a first tilt amount (θ from a plane orthogonal to the optical axis).
a second step of detecting (x, θy); the substrate table (1
0) the second tilt amount (Θx, from the plane orthogonal to the optical axis)
Θy) is detected in a third step; the first tilt amount or the second tilt amount for controlling the attitude of the substrate table based on the first position and the first tilt amount and the target position and the target tilt amount. The fourth which switches and outputs one of the tilt amounts
Steps; the first tilt amount or the second tilt amount output in the fourth step, the target position, and the position of the substrate table in the optical axis direction and the tilt amount from a plane orthogonal to the optical axis. And a fifth step of controlling based on the target tilt amount and the first position.

According to this, in the first step, the target position in the optical axis direction of the exposure field on the surface of the photosensitive substrate and the target tilt amount from the plane orthogonal to the optical axis are output. Further, in the second step, the first position in the optical axis direction of the projection optical system in the exposure field on the surface of the photosensitive substrate and the first tilt amount from the plane orthogonal to the optical axis are detected, and in the third step,
The second tilt amount from the plane orthogonal to the optical axis of the substrate table is detected. In the fourth step, either the first tilt amount or the second tilt amount is switched and output for controlling the attitude of the substrate table based on the first position and the first tilt amount and the target position and the target tilt amount. Then, in the fifth step, the position of the substrate table in the optical axis direction and the tilt amount from the plane orthogonal to the optical axis are the first tilt amount or the second tilt amount output in the fourth step, the target position, and the target tilt. It is controlled based on the quantity and the first position.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.
7 will be described with reference to FIG.

FIG. 1 schematically shows the structure of a step-and-scan type projection exposure apparatus according to an embodiment.

In FIG. 1, reticle R as a mask
Are placed on the reticle stage 3 via the reticle holder 2. This reticle stage 3 is moved by the reticle stage drive unit 14 to make the reticle stage guide 4
It is adapted to be driven in the scanning direction (X direction in FIG. 1) along the guide surface. A movable mirror 5 is provided at one end of the reticle stage 3 in the scanning direction so as to extend in the direction orthogonal to the paper surface (Y direction). A reticle interferometer 13 is arranged facing the moving mirror 5 to irradiate the moving mirror 5 with laser light and receive the reflected light to measure the position of the reticle stage 3. Reticle interferometer 13
The measured value of is input to the main control system 20,
Reference numeral 0 controls the position and speed of the reticle stage 3 via the reticle stage drive section 14 based on the measurement value of the reticle interferometer 13.

A moving mirror (not shown) extending in the X direction is provided on the reticle stage 3 in order to detect a deviation amount in the Y direction, and a reticle interferometer (not shown) faces the moving mirror. Is provided.

The illumination field 1 on the reticle R is substantially uniformly illuminated by illumination light from an illumination optical system (not shown), and the projected image is projected on the wafer W as a photosensitive substrate via the projection optical system PL. Is formed in the exposure field 6 of.

The wafer W is suction-held on the wafer holder 8 by a vacuum chuck (not shown). The wafer holder 8 is placed on the substrate table 10. The substrate table 10 is, as shown in FIG.
It is supported on the XY stage 11 at three points by the three Z position driving units 21, 22, and 23. These Z position driving units 21, 22, 23 are actuators 21A, 22A for driving the supporting points of the respective Z position driving units on the lower surface of the substrate table 10 in the optical axis direction (Z direction) of the projection optical system PL.
23A and encoders 21B, 22B, and 23B that detect the Z-direction position of each Z-position drive unit (see FIG. 5).

Here, the structure of the Z position drive units 21, 22, and 23 will be described in detail. FIG. 6 shows a vertical cross-sectional view of one configuration example of the Z position drive unit 21, and in this FIG. 6, the actuator 21A is the drive mechanism housing 4
0, feed screw 41, coupling 44, nut 39, column 38, slider 35, wedge member 36A, rotating body 36B
And a linear guide 37 and the like.

This will be described in more detail. The drive housing 4
0 is not shown in FIG. 6, but is actually XY in FIG.
It is fixed on the stage 11. Inside the drive mechanism housing 40, a feed screw 41 is arranged in the horizontal direction (left and right direction of the paper surface in FIG. 6), and both ends thereof are pivotally supported by the drive mechanism housing 40. A rotary motor 45 is connected to one end (the right end in FIG. 6) of the feed screw 41 via a coupling 44. Further, a screw portion is formed on the outer periphery of the central portion of the feed screw 41, and a nut 39 fixed to the lower end of the column 38 is screwed into the screw portion. At the upper end of the column 38,
The slider 35 is fixed, and a wedge member 36A is fixed to the upper portion of the slider 35. This wedge member 36A
The rotating member 36B attached to the substrate table 10 of FIG. 1 in a state where only rotation about the axis in the direction orthogonal to the paper surface of FIG. ing. Further, the slider 35 is movable along a linear guide 37 extending in parallel with the feed screw 41.

The other end of the feed screw 41 (the left end in FIG. 6)
An encoder 21B, which constitutes the Z position drive unit 21 together with the actuator 21A, is connected via a coupling 42. As the encoder 21B, a rotary encoder that detects the rotation angle of the feed screw is used.

Therefore, the controller 3 shown in FIG.
The control signal indicating the drive speed from the rotary motor 45
Is supplied to the rotary motor 45, the rotary motor 45 rotates the feed screw 41 at the instructed drive speed (angular speed). As a result, the nut 39 moves in the X direction along the feed screw 41, and the slider 35 moves along the feed screw 41 integrally with the wedge member 36A. Therefore, the rotating body 36B that is in contact with the inclined surface of the upper surface of the wedge member 36A is displaced in the vertical direction (Z direction) with respect to the drive mechanism housing 40 while rotating. In addition, the rotational angular velocity of the feed screw 41 is determined by the encoder 21.
The vertical movement speed of the rotating body 36B can be detected based on the output of the encoder 21B.

The other Z position driving units 22 and 23 are also the above Z
It is configured similarly to the position drive unit 21.

As the actuators 21A to 23A, a rotary motor may be used as a drive source as shown in FIG. 6, but the present invention is not limited to this. For example, a laminated piezoelectric element (piezo element) or the like is used. You may. When a linearly displacing driving element is used as the actuators 21A to 23A, a linear encoder such as an optical type or a capacitance type is used as an encoder for detecting the position in the Z direction. To be done.

In the present embodiment, the substrate table 10 and the above-described three actuators 21A, 22A and 23A adjust the position of the surface of the wafer W in the optical axis direction (Z direction position) and the inclination with respect to the optical axis orthogonal plane. And a Z tilt stage 60 is configured (see FIG. 2).

Returning to FIG. 1, the XY stage 11 on which the substrate table 10 is mounted is driven by the wafer stage drive section 16 in the X-axis and Y-axis directions, whereby the wafer W is moved in the Y-direction. It is designed to be moved and scanned in the X direction. As shown in FIG. 2, the movable mirror 12X is mounted on the substrate table 10 at one end in the X-axis direction.
An X-axis wafer interferometer 15X is provided extending in the axial direction and facing the movable mirror 12X. Similarly, at one end in the Y-axis direction on the substrate table 10, the movable mirror 12Y is attached to the X-axis.
A Y-axis wafer interferometer 15Y is arranged so as to extend in the axial direction and face the movable mirror 12Y. The wafer interferometers 15X and 15Y measure the position of the substrate table 10 in the two-dimensional X and Y directions. In FIG. 1, the movable mirrors 12X and 12Y are representatively shown as the movable mirror 12, and the wafer interferometers 15X and 15Y are shown as the wafer interferometer 15. Wafer interferometer 15
Of the wafer stage drive unit 1 is input to the main control system 20.
The position and speed of the XY stage 11 are controlled via 6. At the time of scanning for exposure, the main control system 20 synchronously controls the reticle stage 3 and the wafer stage 11.

The position of the surface of the wafer W in the Z direction is determined by the light transmission system 7A.
Photoelectric detection is performed by a focus sensor (hereinafter collectively referred to as “focus sensor 7” as appropriate) serving as a first detection unit including a light receiving system 7B and a light receiving system 7B. FIG. 3 shows the detection principle of the focus sensor 7. As shown in FIG. 3A, the incident position of the reflected light on the surface of the wafer W of the light beam emitted from the light transmitting unit 7a is determined by the light receiving unit 7b according to the Z-axis direction position on the surface of the wafer W. The S-curve signal that changes on the surface and corresponds to this, as shown in FIG. 3B, is output from the light receiving unit 7b. Therefore, the position of the surface of the wafer W in the Z-axis direction is photoelectrically detected based on the S-curve signal. In this embodiment, the focus sensor 7 is
As shown in FIG. 4, it is composed of a plurality of sensors 71 to 7n. Then, the plurality of sensors 71 to 7n are arranged on the exposure field 6 on the wafer W on the optical axis A of the projection optical system PL.
They are arranged two-dimensionally with X as the center. Since a plurality of Z-axis direction positions are detected by the plurality of sensors 71 to 7n, an approximate plane is obtained by a calculation process such as the least square method using the plurality of Z-axis direction positions, and the wafer W surface is obtained by the inclination of the approximate plane. (Strictly speaking, exposure field 6) inclination angle (θ
x, θy) is also known.

In this embodiment, a plurality of sensors 71 to 7n are used to detect the tilt angle and the focus position of the exposure field 6 on the wafer W, but one measuring point is used instead of the plurality of sensors. An AF sensor may be used. In this case, a parallel light beam oblique incidence type leveling sensor is used which obliquely irradiates the surface of the wafer W with a parallel light beam and detects the tilt angle of the surface from the lateral deviation amount of the condensed position of the reflected light.

In FIG. 1, the main control system 20 controls the Z tilt stage 60 (more specifically, the actuators 21A, 22A and 23A for driving the substrate table 10) by using the measured value by the focus sensor 7. , The position of the front surface of the wafer W is controlled.

The above-mentioned actuators 21A, 22A,
The Z-direction position of each support point of the substrate table 10 driven by 23A is measured by the encoders 21B, 22B, 23B incorporated in the Z-position drive units 21, 22, 23. The measured values PZ1, PZ2, PZ3 and the XY two-dimensional coordinate positions (X
1, Y1), (X2, Y2), (X3, Y3), the position of the substrate table 10 is defined by the following equation (1).

[0052]

[Equation 1]

Where Θx: inclination in the X direction (inclination around the Y axis) Θy: inclination in the Y direction (inclination around the X axis) Z: position in the Z axis direction. Note that the coordinate system of the surface of the wafer W by the focus sensor 7 and the coordinate system of the position of the substrate table 10 by the encoders 21B, 22B, and 23B are calibrated in advance so that their origins and scales match.

FIG. 5 shows the configuration of the focus control system in this embodiment. This focus control system includes a target value output unit 25 as a target value output unit, a least squares approximation unit 27 as a calculation unit, a control mode determination unit 28 as a determination unit, a decoupling unit 29, and a coordinate conversion unit 3.
0, a controller 31, a multiplexer 32 as switching means, three subtractors 33A to 33C, and the like. Explaining each part in detail, the target value output part 25
Z-position target value z ', X-direction inclination (first Y-axis inclination (Y-axis inclination) first target value θx', Y-direction inclination (X-axis inclination) first value θx ' The target value θy ′ is constantly sent to the control mode determination unit 28. Further, the target value output unit 2
5 outputs a target value z ′ of the Z direction position as a target value for position control of the controller 31 and, according to a result of control mode determination by the control mode determination unit 28, which will be described later, X
The first target value θx ′ or the second target value θx ′ of the inclination in the direction (inclination around the Y axis) is output as the target value for the position control of the controller 31, and the inclination in the Y direction (inclination around the X axis). Of the first target value θy ′ or the second target value θy ′ of the controller 3
It is output as the target value of the position control of 1.

Here, the Z-direction position target value z ', the first target value θx' of the X-direction inclination (inclination around the Y-axis) and the first target value θx 'of the Y-direction inclination (inclination around the X-axis). The target value θy 'is
The original target values of focus control obtained by calibrating the image plane of the projection optical system PL in advance by trial burning or the like. The second target values Θx ′ and Θy ′ are tilts in the X direction. (Inclination around the Y-axis) and Y-direction inclination (inclination around the X-axis) are convenient target values set for maintaining. In the present embodiment, as will be described later, the second target position Θ
As x ′ and Θy ′, the inclination of the substrate table 10 immediately before switching the control mode is used.

The least-squares method approximating unit 27 approximates the detection signals of the Z-direction position of the surface of the wafer W detected by the individual sensors 71 to 7n constituting the focus sensor 7 in a plane using the so-called least-squares method. , The Z direction position z on the optical axis AX of the projection optical system PL on the surface of the wafer W, the inclination in the X direction (inclination around the Y axis) θx, and the inclination in the Y direction (inclination around the X axis) θy are obtained. . That is, the least-squares approximation unit functions as a calculation unit, and in this embodiment, the least-squares approximation unit 27 and the focus sensor 7 cause the optical axis of the projection optical system PL in the exposure field on the surface of the wafer (photosensitive substrate). A first detector is configured to detect a first position in the direction and a first tilt amount from a plane orthogonal to the optical axis.

The control mode determination unit 28 is connected to the target value output unit 2
Target values z ′, θx ′, θy ′ from 5 and the least-squares approximation unit 2
The control mode is determined based on the deviations (Δθx, Δθy, Δz) from the current value information z, θx, θy from 7. This will be described later.

The coordinate conversion unit 30 includes three Z position drive units 2.
Encoders 21B, 22 incorporated in 1, 22, 23
The measured values PZ1, PZ2, and PZ3 of B and 23B are expressed by the formula (1).
In accordance with the above, the coordinates are converted into the Z direction position Z, the inclination in the X direction (inclination around the Y axis) Θx, and the inclination in the Y direction (inclination around the X axis) Θy, and the Θx and Θy of them are sent to the multiplexer 32.

The three subtractors 33A, 33B and 33C are
Z-direction position deviation Δzz (Δz), which is the difference between the target value z ′ from the target value output unit 25 and the Z-direction position (current value z) from the least-squares approximation unit 27, the target from the target value output unit 25 Tilt in the X direction (tilt about Y axis) deviation Δθxx, which is the difference between the value θx ′ (or Θx ′) and the current value θx (or Θx) output from the multiplexer 32, the target value θy ′ (or Θy ′) And a current value θy (or Θy), a tilt (tilt about the X axis) deviation Δθyy in the Y direction is obtained.

The controller 31 is a controller of a position control loop and performs so-called P operation, PI operation or PID operation using the Z direction position deviation Δzz, the X direction inclination deviation Δθxx, and the Y direction inclination deviation Δθyy as operation signals. It is configured to include a PID controller. The controller 31 gives the gains to the deviations Δzz, Δθxx, and Δθyy as speed commands to the actuators 21A, 22A, and 23A.

The decoupling device 29, which depends on the linearity, can be independently controlled by inserting the decoupling device 29 in the servo loop. It is like this. This decoupling device 2
9 is a decoupling calculation for distributing the speed command given by the three components in the Z direction and the inclination around the X and Y axes based on the XY two-dimensional coordinate values of the current position of each Z position drive unit. , The calculation result is actually the actuator 21A, 22
It outputs to A and 23A.

That is, in the controller 31, the deviation Δ
Position servo loop gains Kθx, Kθy, and K for θxx, Δθyy, and Δzz with respect to tilts around the XY axes and components in the Z direction.
actuators 21A, 22A, 2 by multiplying z respectively
Kθx Δθxx, Kθy Δθy as speed command values to 3A
Get y and Kz Δzz. Then, in the decoupling device 29, the speed commands Vz1 and Vz of each Z position drive unit are calculated from the speed command values.
2, the following equation (2) is calculated to obtain Vz3.

[0063]

[Equation 2]

Here, (X1, Y1), (X2, Y
2) and (X3, Y3) are the projection optical system P of each Z position drive unit.
The position is based on L.

In response to a command from the control mode determination section 28, the multiplexer 32 outputs the two components (θx, θy) of the current value from the least-squares approximation section 27 or the current value from the coordinate conversion section 30. Two components in the tilt direction (Θx, Θy)
Either of the above is switched and output. That is, as the current position, the position of the surface of the wafer W detected by the focus sensor 7 and the encoders (21B to 23B) of each Z position drive unit
The multiplexer 32 is prepared so that both of the positions of the substrate table 10 detected in step 3 can be used.

3-axis actuator (21A-23A)
Has a speed minor loop (current minor loop) and uses a built-in speed detector (tacho generator) to follow a given speed command by applying servo. That is, the Z position drive units 21, 22, and 23 are configured as sub-units controlled by a speed loop using a tacho generator built into the actuators 21A, 22A, and 23A as a speed sensor. It is designed to follow it.

Next, with reference to FIG. 7, the determination of the control mode in the control mode determination unit 28 and the switching of the control modes associated therewith will be described in detail.

The speed command values Vz1 and Vz are calculated by the above equation (2).
When either 2 or Vz3 exceeds the limit and becomes saturated, the equation (2) no longer functions as a decoupling device.

Here, assuming that the maximum value of the speed command value is Vmax, the condition that the speed command value to the actuator of each Z position drive unit does not exceed the limit is the following condition A. Becomes In the following description, the speed command value Vzn will be described as VznA, VznB, VznC in order to distinguish between the determination conditions.

Condition A. VznA = Kθx · Δθx · Xn + Kθy · Δθy · Yn
At + Kz.multidot..DELTA.z (where n = 1, 2, 3), either VznA exceeds Vmax.

Therefore, the control mode determination unit 28 first determines whether or not any of VznA exceeds Vmax (step 100 in FIG. 7). Then, when this determination is negative (when the condition A. is negative, the control mode determination unit 28 determines that it is the first control mode, and the multiplexer 32 obtains it based on the detection value of the focus sensor 7. A command for outputting θx, θy (that is, the output from the least-squares approximation unit 27) is given, whereby the multiplexer 32 outputs the current values θx, θ.
y is output. At this time, the target value output unit 25 outputs z ′ and the first target values θx ′ and θy ′ in the tilt direction as target values of the position control loop.

Therefore, in the case of this first control mode,
A positional deviation Δz in the Z direction, an inclination (inclination around the Y axis) deviation Δθx in the X direction, and an inclination (inclination around the X axis) deviation Δθy in the Y direction are input to the controller 31. That is, in the first control mode, the difference between the target value and the current position of the surface of the wafer W detected by the focus sensor 7 (represented by the three components of the Z direction on the optical axis of the projection optical system and the tilt around the XY axes) is deviated ( As a motion signal), the controller 28 performs a control operation, and the controller 31 applies a gain to each component in the Z direction and the tilt direction around the XY axis to generate a speed command. This speed command is converted by the decoupling device 29 into a speed command for the actuator at the position of each Z position drive unit in accordance with the control rule of equation (2), and is given to the actuator having a speed minor loop. The result of the movement of the actuator is detected by the focus sensor 7 as the displacement of the surface of the wafer W, and the position control of the closed loop is performed there (step 106 in FIG. 7).

On the other hand, when the determination in step 100 is negative, that is, the condition A. If holds,
Proceeding to step 102, the following condition B. Is determined.

Condition B. At VznB = Kθx · Δθx · Xn + Kz · Δz (where n = 1, 2, 3), any of VznB exceeds Vmax.

When the determination in step 102 is negative, that is, the condition A. And the condition B. Is not satisfied (in this case, regardless of whether condition C described later is satisfied or not satisfied), the control mode determination unit 28
Then, the fourth control mode is determined and a command value for outputting θx and Θy is given to the multiplexer 32. As a result, the least-squares approximation unit 27 from the multiplexer 32.
From the coordinate conversion unit 30 is output.
At this time, the target value output unit 25 outputs z ′ and target values θx ′ and Θy ′ in the tilt direction as target values of the position control loop. Therefore, in the case of the fourth control mode, the controller 31 has a position deviation Δz in the Z direction, an inclination (inclination around the Y axis) deviation Δθx in the X direction, and an inclination (inclination around the X axis) deviation Δθy in the Y direction. '= Θy'-Θy is input. As a result, in the decoupling device 29, the control law of the equation (2) is set so that the deviation Δθyy is not the difference between the target value and the current position, but the position of the substrate table 10 immediately before switching the control and the current position of the substrate table 10. Replace with the difference and execute. This allows
The tilt in the Y direction, that is, the attitude in the tilt direction around the X axis is controlled so as to maintain the attitude immediately before switching the control regardless of the state of the surface of the wafer W. Regarding the inclination in the X direction (inclination around the Y axis) and the Z direction, the difference between the target value and the current value is given as a deviation, so that the current value matches the target value by normal servo control based on the output of the focus sensor. Is controlled (step 108 in FIG. 7).

On the other hand, if the judgment in step 102 is affirmative, the routine proceeds to step 104, where it is judged whether the following condition C is satisfied.

Condition C. At VznC = Kθy · Δθy · Yn + Kz · Δz (where n = 1, 2, 3), one of VznC exceeds Vmax.

When the determination in step 104 is affirmative, that is, the condition B. And C.I. If both of the above are satisfied, the control mode determination unit 28 determines that the second
It is determined that the control mode is the control mode No., and a command value for outputting Θx and Θy is given to the multiplexer 32. Accordingly, the multiplexer 32 outputs the values Θx and Θy from the coordinate conversion unit 30. At this time, the target value output unit 25
Outputs z'as target values for the position control loop and second target values Θx ', Θy' in the tilt direction. Therefore, in the case of this second control mode, the controller 31 is
Position deviation Δz, tilt in X direction (tilt around Y axis)
The deviation Δθx ′ = Θx′−Θx and the inclination in the Y direction (inclination around the X axis) deviation Δθy ′ = Θy′−Θy are input. As a result,
By the decoupling device 29, Δθx and Δθy as deviations
Instead of the difference between the target value and the current position, the difference between the position of the substrate table 10 immediately before the control is switched and the current position of the substrate table 10 (Δθx ′ = Θx′−θx, Δθy ′ = Θy ′).
−Θy) is used to implement the control law of equation (2). Thereby, the actuators 21A, 22A, 23
The result of the movement of A is detected by the encoders 21B, 22B, 23B as the displacement of the Z position drive units 21, 22, 23. The detected displacement is coordinate-converted into the current value of the substrate table 10 by the coordinate conversion unit 30, and the component in the tilt direction around the XY axes becomes a feedback signal to the controller 31. Here, closed-loop position control is performed on the tilt component around the XY axes, and the tilt posture around the XY axes is controlled so as to maintain the posture immediately before the control is switched, regardless of the state of the wafer surface. With respect to the Z direction, the difference between the target value and the current value is given as a deviation, so that the current value is controlled by normal servo control so as to match the target value (step 110 in FIG. 7).

On the other hand, if the determination at step 104 is negative, that is, condition A. And condition B. And the condition C. If is not established, the control mode determination unit 2
At 8, it is determined that the third control mode is set, and a command for outputting Θx and θy is given to the multiplexer 32. As a result, the multiplexer 32 to the coordinate conversion unit 30
To θx from the least-squares approximation unit 27. At this time, the target value output unit 25 outputs z'as the target value of the position control loop and the target values Θx 'and θy' in the tilt direction.
Is output. Therefore, in the case of this third control mode,
The controller 31 includes a positional deviation Δz in the Z direction, an inclination (inclination around the Y axis) deviation Δθx ′ = Θx′−Θx, Y in the X direction, Y
The tilt (tilt about the X-axis) deviation Δθy in the direction is input. As a result, in the decoupling device 29, the control law of the equation (2) is set so that the deviation Δθx is not the difference between the target value and the current position, but the position of the substrate table 10 immediately before switching the control and the current position of the substrate table 10. Replace with the difference and execute. As a result, the tilt in the X direction, that is, the attitude in the tilt direction around the Y axis is controlled so as to maintain the attitude immediately before switching the control, regardless of the state of the surface of the wafer W. Regarding the inclination in the Y direction (inclination around the X axis) and the Z direction, since the difference between the target value and the current value is given as a deviation, control is performed by normal servo control so that the current value matches the target value ( Step 112 of FIG. 7).

The focus control system of the present embodiment normally operates in the first control mode, the degree of unevenness on the surface of the wafer W is large, and each Z position drive unit for tilt correction about the X axis and the Y axis is corrected. When it is determined that the speed command value given to the actuator exceeds the limit, switching to the second to fourth control modes is performed. The determination based on the conditions A, B, and C continues even during the operation in the second to fourth control modes, and the control modes are sequentially switched according to the change of the conditions. In this case, since the condition A and the condition C are determined after the condition A is determined first, if the degree of unevenness on the surface of the wafer W is reduced and the speed command value falls within the limit. Immediately switched to the first control mode,
Focus / leveling control is started.

As is clear from the above description, in the present embodiment, the encoders 21B, 22B, 23B and the coordinate converter 30 constitute the second detecting means, and the multiplexer 32, the controller 31 and the non-interfering means. Chemicalizer 2
9 and 9 constitute a control means.

As described above, according to this embodiment, the surface of the wafer W in the exposure field is projected by the projection optical system as long as the unevenness of the surface of the wafer W is relatively small and the leveling can be followed in view of the capability of the apparatus. By controlling so as to match the image plane of the system PL, the defocus for the entire exposure field can be controlled to the minimum and the depth of focus of the projection optical system can be maximized. Further, even when the surface of the wafer W has a relatively large unevenness and the ability of the apparatus is not able to follow the leveling, focus control can be realized without seriously degrading the control and causing a fatal defocus.

Also in the latter case, if the inclination about one of the X-axis and the Y-axis can be sufficiently tracked by the ability of the apparatus by the two-stage condition determination, the inclination posture about the other axis is set. It is possible to control the Z-direction position while keeping the same, and to control the inclination around the one axis to follow the target value.

In the above embodiment, the case where the four types of modes, the first control mode to the fourth control mode, are finely switched has been described, but the third and fourth control modes are not necessarily provided and are practically used. The above merit is considered sufficient. When the unevenness of the surface of the wafer W in the exposure field is too large to be covered by the leveling control, the depth of focus of the projection optical system PL is greatly consumed, and the effectiveness of the leveling control is reduced, which is practically used. This is because focus control is often sufficient. In this case, the condition A. First based only on
It suffices to switch between the control mode and the second control mode.

Further, the condition A.1 for determining the control mode switching described in the above embodiment is used. , B. , C.I. Is an example, and the present invention is not limited to this. For example, the deviation (difference between the target value and the current value) itself is limited,
It is also possible to adopt a method of switching the control when a deviation more than a predetermined value is detected after the completion of the pull-in.

In the above embodiment, the judgment condition A. ,
B. , C.I. Was a speed condition, but when using a laminated piezoelectric element, it is easier to make a judgment based on a displacement condition rather than a speed condition.

Further, in the above embodiment, the closed loop servo control is performed, and the target value itself is switched corresponding to the switching of the control mode in order to keep the tilt posture constant.
The present invention is not limited to this. Therefore, any control method may be adopted as long as it can maintain the posture in the tilt direction around one axis and can adjust the Z direction position and the tilt around the other axis.

[0088]

As described above, according to the present invention,
While the determination means in the control means makes an affirmative determination, the exposure field on the surface of the photosensitive substrate coincides with the image plane of the projection optical system based on the target value from the target value output means and the calculation result of the calculation means. The adjustment means is controlled so that the target value in the optical axis direction from the target value output means and the calculation result of the calculation means are maintained while the determination means makes a negative determination. The adjusting means is controlled so that the position in the optical axis direction of the exposure field on the surface of the photosensitive substrate coincides with the center of the image plane of the projection optical system in the optical axis direction. As a result, there is an unprecedented excellent effect that a high follow-up property can be secured and a stable focusing operation can be performed on a photosensitive substrate having a large degree of unevenness without causing control failure.

In particular, according to the invention described in claims 8 to 9, in addition to the above effects, when only the inclination deviation in either the X-axis direction or the Y-axis direction is outside the allowable range, the control means The position of the exposure field on the surface of the photosensitive substrate in the optical axis direction and the inclination of the other axial direction are detected by the target value from the target value output means and the second detecting means while keeping the control mode constant in the one axial direction inclination. Since the mode is switched to the third and fourth control modes for controlling the adjusting means based on the tilt amount,
There is an effect that a more accurate and fine focus and leveling operation can be executed without causing a failure in control.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a step-and-scan projection exposure apparatus according to an embodiment.

FIG. 2 is a perspective view showing details of a substrate table and a drive mechanism thereof in FIG.

FIG. 3 is a diagram for explaining the detection principle of the focus sensor of FIG.

FIG. 4 is a diagram showing an arrangement of individual sensors forming the focus sensor of FIG.

5 is a block diagram showing a configuration of a focus control system of the apparatus shown in FIG.

FIG. 6 is a cross-sectional view showing a specific configuration example of the Z position drive unit in FIG.

FIG. 7 is a flowchart for explaining the control mode determination in the control mode determination unit and the switching of the control modes associated therewith.

[Explanation of symbols]

 7 Focus Sensor 10 Substrate Table 21A, 22A, 23A Actuator 21B, 22B, 23B Encoder 25 Target Value Output Section 27 Least Square Approximation Section 28 Control Mode Determining Section 29 Decoupling Unit 30 Coordinate Converter 31 Controller 32 Multiplexer 60 Z Tilt Stage W Wafer R Reticle PL Projection optical system

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/30 525L 525X

Claims (15)

[Claims] 1. Illuminating a patterned mask,
With the image of a part of the pattern of the mask projected onto the exposure field on the photosensitive substrate placed on the substrate table through the projection optical system, the mask and the photosensitive substrate are projected to the projection optical system. A projection exposure apparatus that scans in synchronization, comprising: first detection means for detecting a position of the projection optical system in an optical axis direction within an exposure field of the photosensitive substrate surface; and the optical axis direction of the photosensitive substrate surface. And a first position in the optical axis direction of the exposure field of the photosensitive substrate surface based on the detection information from the first detecting means, Computing means for calculating a first tilt amount of the exposure field from an axis orthogonal plane; target value output means for outputting a target position and a target tilt amount of the exposure field on the photosensitive substrate surface in the optical axis direction; Based on the target value from the target value output means and the calculation result of the calculation means, based on at least one of the difference between the target position and the first position and the difference between the target tilt amount and the first tilt amount. Determination means for determining whether or not the command value of the control amount for the adjustment means defined within the control range of the adjustment means; and the target position and the target while the determination means makes a positive determination. Based on the tilt amount and the first position and the first tilt amount, the adjusting means is controlled so that the exposure field on the surface of the photosensitive substrate coincides with the image plane of the projection optical system, and the judging means makes a negative result. While performing the determination, the position of the exposure field on the photosensitive substrate surface in the optical axis direction of the projection optical system is determined based on the target position and the first position while keeping the inclination of the photosensitive substrate surface constant. Optical axis of image plane Projection exposure apparatus and a control means for controlling said adjusting means so as to coincide with the center of the. 2. A second detection means for detecting a second inclination amount from a plane of the substrate table orthogonal to the optical axis, the target value output means being positive in the determination result of the determination means. The projection exposure apparatus according to claim 1, wherein when the positive determination is changed to the negative determination, the second tilt amount detected by the second detection means is sent to the control means. 3. The projection exposure apparatus according to claim 1, wherein the command value of the control amount is a speed command value for the adjusting means. 4. Illuminating the patterned mask,
With the image of a part of the pattern of the mask projected onto the exposure field on the photosensitive substrate placed on the substrate table through the projection optical system, the mask and the photosensitive substrate are projected to the projection optical system. 1. A projection exposure apparatus that scans in synchronization, comprising: first detection means for detecting a position in the optical axis direction of the projection optical system within an exposure field on the surface of the photosensitive substrate; Adjusting means for adjusting the position and the inclination from a plane orthogonal to the optical axis; and a first means in the optical axis direction of the exposure field of the photosensitive substrate surface, based on detection information from the first detecting means. Computing means for calculating a position and a first tilt amount from a plane orthogonal to the optical axis; target value output means for outputting a target position and a target tilt amount in the optical axis direction of an exposure field on the surface of the photosensitive substrate; The substrate Second detection means for detecting a second amount of inclination from a surface of the table orthogonal to the optical axis; and the target position based on the target value from the target value output means and the calculation result of the calculation means. Whether the command value of the control amount for the adjusting means, which is determined based on at least one of the difference from the first position and the difference between the target inclination amount and the first inclination amount, is within the control range of the adjusting means. A first control mode for controlling the adjusting means based on the target position and the target tilt amount, and the first position and the first tilt amount according to the determination result of the determination means; Based on the target position and the first position while keeping the inclination of the surface of the photosensitive substrate constant, the position in the optical axis direction of the exposure field on the surface of the photosensitive substrate is the center of the image plane of the projection optical system in the optical axis direction. Said to match Second controlling means
A projection exposure apparatus having control means for switching between control modes. 5. The first tilt amount includes a first X tilt amount in an X-axis direction which is a scanning direction of the photosensitive substrate on a surface of the photosensitive substrate and a first Y tilt amount in a Y-axis direction orthogonal to the X-axis. , The second tilt amount is a second amount in the X-axis direction of the substrate table.
An X tilt amount and a second Y tilt amount in the Y axis direction are included, and the target tilt amount includes a target X tilt amount in the X axis direction and a target Y tilt amount in the Y axis direction. 4. The projection exposure apparatus according to item 4. 6. The determination means, as the determination conditions, the difference between the target position and the first position, the difference between the target X tilt amount and the first X tilt amount, and the target Y tilt amount and the first Y tilt amount. 6. The projection exposure apparatus according to claim 5, wherein the projection exposure apparatus has a first condition for determining whether or not a speed command value for the adjusting means exceeds a first speed based on a difference between and. 7. The control means switches to the first control mode when the first condition is not satisfied, and switches to the second control mode when the first condition is satisfied. 6. The projection exposure apparatus according to item 6. 8. The speed determining command value for the adjusting means based on the difference between the target position and the first position and the difference between the target X tilt amount and the first X tilt amount as the judgment conditions. To the adjusting means based on a second condition for determining whether the speed exceeds a second speed, a difference between the target position and the first position, and a difference between the target Y tilt amount and the first Y tilt amount. 7. A third condition for determining whether or not the command value of 4 exceeds the third speed.
3. The projection exposure apparatus according to claim 1. 9. The control means, when the first and second conditions are satisfied and the third condition is not satisfied, the target position, the target X tilt amount, the target Y tilt amount, the first position, and the first position, Based on the 2X tilt amount and the first Y tilt amount, switching to a third control mode for controlling the adjusting means,
When the condition is satisfied and the second condition is not satisfied, the adjusting unit is controlled based on the target position, the target X tilt amount, the target Y tilt amount, and the first position, the first X tilt amount, and the second Y tilt amount. 9. The projection exposure apparatus according to claim 8, wherein the projection exposure apparatus is switched to the fourth control mode. 10. A pattern-formed mask is illuminated, and an image of a part of the pattern of the mask is projected through a projection optical system onto a predetermined exposure field on a photosensitive substrate mounted on a substrate table. A projection exposure apparatus that scans the mask and the photosensitive substrate in synchronization with the projection optical system in a state, wherein the first position in the optical axis direction of the projection optical system within the exposure field on the surface of the photosensitive substrate. And a first detector for detecting a first tilt amount from a plane orthogonal to the optical axis; an adjustment for adjusting a position of the substrate table in the optical axis direction and a tilt amount from a plane orthogonal to the optical axis. Means; second detecting means for detecting a second tilt amount from a plane of the substrate table orthogonal to the optical axis; orthogonal to the target position in the optical axis direction of the exposure field on the surface of the photosensitive substrate and the optical axis. From the surface Target value output means for outputting a target tilt amount; switching output of either the first tilt amount or the second tilt amount based on the first position and the first tilt amount and the target position and the target tilt amount Projection exposure having switching means for controlling the adjusting means based on either the first tilt amount or the second tilt amount, the first position, the target position, and the target tilt amount. apparatus. 11. The first detecting unit includes a plurality of sensors for obtaining a position in the optical axis direction within an exposure field on the surface of the photosensitive substrate, and the first position and the first position based on the detection positions from the plurality of sensors. A second calculation unit that calculates a first tilt amount, and the second detection unit calculates a tilt amount of the substrate table from the plurality of encoders that obtain a position of the substrate table in the optical axis direction. The projection exposure apparatus according to claim 10, further comprising: 12. A state in which a mask having a pattern formed thereon is illuminated and an image of a part of the pattern of the mask is projected onto an exposure field on a photosensitive substrate mounted on a substrate table through a projection optical system. A projection exposure method for scanning the mask and the photosensitive substrate in synchronization with the projection optical system, which outputs a target position and a target tilt amount in the optical axis direction of an exposure field on the surface of the photosensitive substrate. 1 step; a second step of detecting the position of the projection optical system in the optical axis direction within the exposure field of the surface of the photosensitive substrate; and an exposure field of the surface of the photosensitive substrate based on the result detected in the second step. A third step of calculating a first position in the optical axis direction and a first tilt amount of the exposure field from the plane orthogonal to the optical axis;
The optical axis direction position of the photosensitive substrate and the control amount of the inclination from the plane orthogonal to the optical axis, which are determined based on at least one of the difference between the target position and the first position and the difference between the target inclination amount and the first inclination amount. For determining whether or not is within a predetermined control range
Step; if the determination is affirmative, the exposure field on the surface of the photosensitive substrate matches the image plane of the projection optical system based on the target position and the target tilt amount and the first position and the first tilt amount. Control the position and orientation of the photosensitive substrate,
If a negative determination is made, the position of the exposure field in the optical axis direction is the optical axis of the image plane of the projection optical system based on the target position and the first position while keeping the inclination of the photosensitive substrate surface constant. A fifth step of controlling the position of the photosensitive substrate so as to coincide with the center of the direction. 13. The method further comprises a sixth step of detecting a second amount of inclination of the substrate table from the plane orthogonal to the optical axis, wherein the determination result in the fourth step changes from a positive determination to a negative determination, The projection exposure method according to claim 11, wherein, in the fifth step, the posture of the photosensitive substrate is kept constant based on the second tilt amount. 14. The projection exposure method according to claim 12, wherein the control amount is a speed command value for controlling at least one of a position and a posture of the photosensitive substrate. 15. A mask on which a pattern is formed is illuminated, and an image of a part of the pattern of the mask is projected onto a predetermined exposure field on a photosensitive substrate mounted on a substrate table through a projection optical system. In this state, a projection exposure method for scanning the mask and the photosensitive substrate in synchronization with the projection optical system, comprising: a target position in the optical axis direction of an exposure field on the surface of the photosensitive substrate and a direction orthogonal to the optical axis. A first step of outputting a target tilt amount from the surface to be processed; a first position in the optical axis direction of the projection optical system in the exposure field on the surface of the photosensitive substrate, and a first tilt amount from a surface orthogonal to the optical axis. And a third step of detecting a second tilt amount from a plane of the substrate table orthogonal to the optical axis; a first position and a first tilt amount, and a target position and a target tilt amount. On the basis of, Wherein in order to control the attitude of the serial substrate table first
A fourth step of switching and outputting either the tilt amount or the second tilt amount; and outputting the tilt amount from the position of the substrate table in the optical axis direction and the plane orthogonal to the optical axis in the fourth step. And a fifth step of controlling based on the first tilt amount or the second tilt amount, the target position, the target tilt amount, and the first position which have been performed.