JPH0845812A - Surface position setting device - Google Patents

Abstract

PURPOSE:To provide a surface position setting device for a scanning exposure device, which has a relatively low gain and high follow-up performance without requiring high-level tuning in a servo system. CONSTITUTION:A deviation DELTAz (t) obtained by subtracting a focus position z (t) detected in a focus position detecting system from the target value zr (t) of a focus position in a subtracting part 69 is supplied to a position loop controller 56, and velocity vz (t) obtained by multiplying it by a predetermined gain in the position loop controller 56, predicted tilt velocity vz' (t) corresponding to a tilt angle in the surface of a wafer and predicted step difference velocity vz'' (t) corresponding to a step difference between the exposure region of the surface of the wafer and an estimated region are supplied to an adding part 57. An actuator 68 is driven through a velocity loop controller 63 on the basis of velocity Vz (t) obtained by integration in the adding part 57.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface position setting device for setting a height or a tilt angle of a photosensitive substrate to a predetermined state in a projection exposure apparatus for manufacturing a semiconductor device or a liquid crystal display device, for example. In particular, it is suitable for application to an autofocus mechanism or an autoleveling mechanism of a scanning exposure apparatus such as a slit scan method or a step and scan method.

[0002]

2. Description of the Related Art In a projection exposure apparatus used in a lithography process for manufacturing a semiconductor device, etc.
In a projection exposure apparatus that uses a batch exposure method such as the AND / REPEAT method (stepper, etc.), the wafer to be focused is stationary, so autofocus or autoleveling is performed by servo control for a fixed target value. Will be seen.

FIG. 12 is a simplified view of a conventional autofocus mechanism. In FIG. 12, the target value of the focus position of the wafer (the position in the optical axis direction of the projection optical system) is input to one input unit of the subtraction unit 69. z _r (t) is supplied, and the actual focus position z (t) measured by a focus position detection system (AF sensor) (not shown) is supplied to the other input unit, and the difference Δz ( t) is output. Then, the difference Δz
By multiplying (t) by a predetermined gain by the position loop controller 56, a driving speed v _z (t) in the direction of the focus position of the wafer for making the deviation Δz (t) 0 can be obtained. v _z (t) is supplied to one input section of the subtraction section 62. Further, the actual input speed of the actuator 68 for driving the wafer is supplied to the other input section of the subtraction section 62, and the difference output from the subtraction section 62 is multiplied by a predetermined gain in the speed loop controller 63 to obtain the difference. The drive signal to be supplied is supplied to the actuator 68. That is, the conventional autofocus mechanism for a projection exposure apparatus of the batch exposure type is a relatively simple closed-loop position control system that uses a focus position detection system (AF sensor) as a position detector. The accuracy and the prescribed settling time were obtained.

On the other hand, in recent years, the size of one chip pattern such as a semiconductor element tends to be large, and therefore an exposure apparatus that exposes a larger reticle pattern onto a wafer is required. Therefore, as an exposure apparatus that exposes a large-area pattern without imposing a heavy burden on the projection optical system, while scanning the reticle, the reticle is scanned in a first direction across the optical axis of the projection optical system. In sync,
A scanning type exposure apparatus such as a slit scan method or a step-and-scan method that sequentially exposes a pattern of a reticle to each shot area of the wafer by scanning the wafer in a second direction corresponding to the first direction is provided. Attention has been paid. In the case of such a scanning type exposure apparatus, as shown in FIG. 13, since the exposure is performed by scanning the wafer 69 with respect to a predetermined exposure area 70 in the exposure field of the projection optical system, projection with the same diameter is performed. Exposure to larger shot areas is possible using optics.

When, for example, auto-focusing a wafer in such a scanning type exposure apparatus, the wafer to be focused moves, so that, for example, the wafer 69 in FIG.
In order to focus the point 69a and the like on the upper step, it is necessary to configure a follow-up system that accurately follows the inclination, unevenness, step, etc. of the wafer.

[0006]

However, in the conventional general control, it is known that a steady deviation is inevitably generated when trying to follow the change of the focus position due to the tilt of the wafer by the closed loop control. In order to keep this steady-state deviation within the required accuracy, it is necessary to increase the control gain of the position loop and to configure a higher-order closed-loop servo system (so-called type II) that has an integrator in the position loop. .
However, raising the control gain and inserting an integrator both tend to destabilize the loop, so this servo system requires careful tuning and is stable (robust). It tended to be lacking.

Further, if the control gain is increased to improve the followability, the control band is inevitably widened, and the response of the servo system becomes oscillating, which adversely affects the formation of a projected image by the projection optical system. there were. In view of such points, the present invention is
An object of the present invention is to provide a surface position setting device for a scanning type exposure apparatus having a relatively low gain and a high tracking capability without requiring a high-level tuning of a servo system.

[0008]

A first surface position setting device according to the present invention illuminates a mask (7) on which a transfer pattern is formed with an illuminating light for exposure, and the pattern of the mask is projected by a projection optical system. Through the system (11), the substrate stage (15
X) is projected onto the exposure area (13) on the photosensitive substrate (12) and the mask is scanned in a predetermined direction (+ X direction) in synchronization with the substrate (1) through the substrate stage.
By scanning 2) in a predetermined direction (-X direction),
It is provided in a scanning type exposure apparatus that sequentially exposes the pattern of the mask (7) on the substrate (12), and the position of the surface of the substrate (12) in the optical axis direction (Z direction) of the projection optical system (11) is set to a predetermined value. In the position setting device, the substrate stage (15X)
Above, the projection optical system (11) according to the drive signal supplied
Height adjusting means (1) for controlling the position of the projection optical system (11) of the substrate (12) in the optical axis direction at a driving speed in the optical axis direction of
6A to 16C) and the projection optical system (1
1) The focus position detection means (64) for detecting the position of the projection optical system (11) in the optical axis direction at the measurement point P ₃₂ in the exposure area (13).

Further, according to the present invention, the substrate stage (15) in a predetermined measurement area including the measurement point P ₃₂ in the exposure area (13) is provided.
X) an inclination angle detecting means (65) for detecting an inclination angle with respect to the running surface, a target position in the optical axis direction of the projection optical system of the substrate (12), and a position detected by the focus position detecting means (64). The predicted tilt speed v _z ′ according to the product of the driving signal indicating the target speed v _z according to the difference between the tilt angle detected by the tilt angle detection means (65) and the scanning speed of the substrate stage (15X). Speed signal supply means (52, 53, 56 to 58, 60) for supplying a drive signal obtained by adding the drive signals shown to the height adjusting means (16A to 16C).

In this case, the focus position pre-reading means (66) pre-reads the position in the optical axis direction of the projection optical system at the measurement point P ₅₂ which precedes the exposure area (13) on the substrate (12) in the scanning direction. ) Is provided, and the speed signal supply means uses the sum signal of the drive signal indicating the target speed v _z and the drive signal indicating the predicted tilt speed v _z ′, and the position pre-read by the focus position look-ahead means. It is desirable to supply a drive signal obtained by adding a drive signal indicating the predicted step velocity v _z ″ according to the difference between the position detected by the focus position detection means and the height adjustment means.

[0011]

First, the principle of the present invention will be described with reference to FIGS. In FIG. 9, above the exposure area (13) by the projection optical system on the photosensitive substrate (12), a focus position detecting means (64) for detecting the displacement of the projection optical system in the optical axis direction (Z direction). ) And an inclination angle detecting means (65) are arranged. Further, the focus position pre-reading means (66) is arranged at a position (hereinafter referred to as "pre-reading position") (35A) that can be detected in advance in the scanning direction (-X direction) with respect to the exposure region (13). . Here, the moving speed (scanning speed) of the substrate (12) in the scanning direction (-X direction) is v, and the interval between the detection position and the prefetch position in the exposure area (13) is d.
And Further, the focus position detecting means (64) and the focus position pre-reading means (66) are calibrated so as to detect the deviation amount from the running surface of the substrate (12) in the scanning direction as a reference. It is assumed that At this time, one point on the substrate (12) has two means (64, 6).
The time τ required to cross the interval d of 6) is as follows.

[0012]

Τ = d / v Further, as shown in FIG. 10, the tilted substrate (12
Assuming A), the displacement in the Z direction at the measurement point in the exposure area at a certain time t on this substrate (12A) is z.
(T) and the inclination angle is θ (t). Similarly, the displacement in the Z direction at the look-ahead position at time t is z _p (t)
And Then, from the displacement and tilt angle in the Z direction at the measurement point (focus point) in the exposure area at time t, the time (t +
The displacement z (t) in the Z direction at the measurement point in the exposure area at (τ)
Consider predicting + τ). As shown in FIG.
If there are no irregularities or steps on the surface of the substrate (12A), the displacement z
(T + τ) is given by the following equation.

[0013]

## EQU00002 ## z (t + .tau.). Apprxeq.z (t) +. Theta. (T) .d This means that in order to always focus during scanning of the substrate (12A), the substrate (12A) is moved in the Z direction by {z ( t) -z (t +
It shows that it is sufficient to move at the predicted inclination velocity v _z '(t) such that τ)} / τ. Therefore, the following equation is established from (Equation 1) and (Equation 2).

[0014]

Equation 3] _{v z '(t) ≒ -θ} (t) · d / τ = -θ (t) · v Next, if the substrate (12B) there is a step δz the surface as shown in FIG. 11 focus If we consider the case of
z is given by the following equation.

[0015]

Equation 4] _{δz ≒ z p (t) -z} (t) -d · θ (t) the stepped portion on the substrate (12B), the time (t + tau) because according to the exposure area of the projection optical system, Before that, it is considered that the surface of the substrate (12B) is smoothly moved in the Z direction. For that purpose, in addition to the velocity v _z ′ (t) corresponding to the inclination angle θ (t), at the time t, the predicted step velocity v _z ″ (t) expressed by the following equation is applied to the substrate (12B) in the Z direction. You can start driving to.

[0016]

The Equation 5] _{v z "(t) ≒ -δz} / τ this, since the step portion of the substrate (12B) is to reach the exposure area along a trajectory (67) indicated by the dotted line in FIG. 11, precisely at the step portion It can be seen that the focusing is performed in the case of (4) and (5) in this case.

[0017]

[Mathematical formula-see original document] v _z "(t) ≈-{(z _p (t) -z (t) -d.
θ (t)) / d} v These velocity v _z '(t), and v _z "using a (t), in. FIG. 8 constituting the control system shown in FIG. 8, the target position z _r ( The target velocity v _z (t) is obtained by the position loop controller (56) from the deviation Δz (t) between the position t (t) and the position z (t) actually measured by the focus position detecting means (64). v _z speeds above the _{(t) v z '(t} ), and v _z "(t) is summed driving speed V _z (t) is obtained. Then, the actuator (68) as an example of the height adjusting means (16A to 16C) is driven by the speed servo system (62, 63) so that this drive speed V _z (t) can be obtained.

When the predicted tilt velocity v _z '(t) is added in this way, it is approximately equivalent to the case where the constant input is followed, and the normal I-type servo system, that is, PI control (proportional) Integral control) Even in the servo system, the steady-state error can be driven to almost zero, and the tracking error can be reduced. Further, the predicted step velocity v _z "based on the detection result by the focus position prefetching means (66) as the prefetch sensor.
By adding (t), it is possible to improve the followability even for a substrate having irregularities or steps.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a surface position setting device according to the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to an autofocus mechanism and an autoleveling mechanism in a step-and-scan type projection exposure apparatus. FIG. 1 shows a projection exposure apparatus of the present embodiment. In FIG. 1, an illumination light I for exposure from a light source system 1 including a light source, an optical integrator, etc.
L is a slit-shaped illumination area 8 on the reticle 7 with a uniform illuminance via the first relay lens 2, the reticle blind (variable field diaphragm) 3, the second relay lens 4, the mirror 5, and the main condenser lens 6. Illuminate. The arrangement surface of the reticle blind 3 is conjugate with the pattern formation surface of the reticle 7, and the shape of the illumination area 8 on the reticle 7 is set by the position and shape of the opening of the reticle blind 3.

The image of the pattern in the illumination area 8 on the reticle 7 is projected and exposed through the projection optical system 11 into the slit-shaped exposure area 13 on the wafer 12 coated with the photoresist. The Z axis is taken in parallel with the optical axis of the projection optical system 11, the X axis is in the direction parallel to the paper surface of FIG. 1 and the Y axis is in the direction perpendicular to the paper surface of FIG. 1 within a two-dimensional plane perpendicular to the optical axis. I take the. The reticle 7 is held on the reticle stage 9, and the reticle stage 9 is driven on the reticle base 10 in the X direction which is the scanning direction by, for example, a linear motor. The X coordinate of the reticle 7 is measured by the moving mirror 18 on the reticle stage 9 and the external laser interferometer 19, and this X coordinate is measured.
The coordinates are supplied to the main control system 20 that controls the operation of the entire apparatus, and the main control system 20 controls the position and the moving speed of the reticle 7 via the reticle stage drive system 21 and the reticle stage 9.

On the other hand, the wafer 12 is held on the focus / leveling stage 14 via a wafer holder (not shown), and the focus / leveling stage 14 is moved to the Y stage via three actuators 16A to 16C movable in the Z direction. 15Y mounted on the Y stage 15Y
Is mounted on the X stage 15X by, for example, a feed screw method so as to be moved in the Y direction, and the X stage 15X is mounted on the apparatus base 17 by, for example, a feed screw method so as to be moved in the X direction. ing. 3 actuators 16
By expanding and contracting A to 16C in parallel, the position (focus position) of the focus / leveling stage 14 in the Z direction is adjusted, and the three actuators 16A to 16C
The tilt angle of the focus / leveling stage 14 is adjusted by individually adjusting the expansion / contraction amount of 16C.

Further, the focus / leveling stage 1
The X-coordinate of the wafer 12 is constantly monitored by the X-axis moving mirror 22X fixed to the upper end of the wafer No. 4 and the external laser interferometer 23X, and as shown in FIG.
Y and the external laser interferometer 23Y, the wafer 12
Is always monitored, and the detected X and Y coordinates are supplied to the coordinate detection unit 59 in the main control system 20.

Here, a configuration example of the actuators 16A to 16C will be described. FIG. 7 shows the actuator 16A.
7 is a cross-sectional view of FIG. 7, in which the drive mechanism housing 40 is fixed on the Y stage 15Y of FIG. 1, the feed screw 41 is rotatably accommodated in the drive mechanism housing 40, and the cup is provided at the left end of the feed screw 41. A rotary motor 43 is connected via a ring 42, and a rotary encoder 45 for detecting a rotation angle is connected to the right end of the feed screw 46 via a coupling 44. Further, a nut 39 is screwed onto the feed screw 41, a sloped portion 36A having an upper end inclined is fixed to the nut 39 via a support 38, and a rotary body 36B is in contact with the upper end of the sloped portion 36A. The rotator 36B is embedded in the focus / leveling stage 14 of FIG. 1 so as to be rotatable and immovable in the lateral direction.

The inclined surface portion 36A is supported so as to be movable along the linear guide 37 in a direction parallel to the feed screw 41. In this case, the wafer stage control system 2 of FIG.
The control signal indicating the driving speed from the rotary motor 43
The rotary motor 43 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 slope portion 36A also moves along the feed screw 41. Therefore, the rotating body 36B, which is in contact with the upper end of the inclined surface portion 36A, is displaced in the vertical direction (Z direction) with respect to the drive mechanism housing 40 while rotating. Further, by measuring the rotational angular velocity of the feed screw 43 with the rotary encoder 45, the vertical moving velocity of the rotating body 36B is detected. The other actuators 16B and 16C have the same configuration.

The actuators 16A to 16C are
In addition to the method using a rotary motor as shown in Fig. 7,
For example, it may be composed of a piezo element or the like. Returning to FIG. 1,
The main control system 20 controls the operations of the X stage 15X, the Y stage 15Y, and the focus / leveling stage 14 via the wafer stage drive system 24 based on the supplied coordinates. For example, when performing exposure by a scanning exposure method, it is assumed that the projection optical system 11 projects an inverted image at a projection magnification β, and the reticle 7 is moved through the reticle stage 9 in the + X direction (or −X direction) with respect to the illumination area 8. Direction) speed V _R
In synchronism with the scanning in step S1, the wafer 12 is scanned through the X stage 15X in the −X direction (or + X direction) at a speed v (= β · V _R ).

Next, the structure of a multipoint focus position detection system (hereinafter referred to as "multipoint AF sensor") 25 for detecting the position (focus position) of the surface of the wafer 12 in the Z direction will be described. In this multi-point AF sensor 25, detection light that is non-photosensitive to the photoresist emitted from the light source 26 illuminates a large number of slits in the light-sending slit plate 28 via the condenser lens 27, and The image passes through the objective lens 29 and is oblique to the optical axis of the projection optical system 11, and the 15 measurement points P ₁₁ of the exposure area 13 on the wafer 12 and the pre-reading areas 35A and 35B (see FIG. 2) before and after this are provided. To P ₅₁ .

FIG. 2 shows those measurement points P ₁₁ on the wafer 12.
2 to P _{51. In} FIG. 2, preread areas 35A and 35B are set on the + X direction side and the −X direction side of the slit-shaped exposure area 13, respectively. Then, in the exposure area 13, measurement points P _{21 to} P ₄₃ of 3 rows × 3 columns are arranged.
Is set, and the three measurement points P ₁₁ to
P ₁₃ is set, and three measurement points P are set in the prefetch area 35A.
_{51 to} P ₅₃ are set. In this embodiment, the exposure area 1
The average focus position in the exposure area 13 and the tilt angle are obtained from the information of the focus positions at the nine measurement points in 3. Further, when the scanning direction of the wafer 12 is the −X direction, the level difference is corrected by using the focus position information at the three measurement points in the prefetch area 35A, and the wafer 12 is scanned as described later. When the direction is the + X direction, the step difference is corrected using the information on the focus positions at the three measurement points in the prefetch area 35B.

Returning to FIG. 1, the reflected light from these measurement points is condensed on the oscillating slit plate 31 via the condenser lens 30, and the slit image projected on the oscillating slit plate 31 at these measuring points. Are re-imaged. Vibration slit plate 31
Is vibrated in a predetermined direction by the shaker 32 driven by the drive signal DS from the main control system 20. Light passing through many slits of the vibration slit plate 31 is detected by the photoelectric detector 3
Each of the photoelectric conversion elements is photoelectrically converted by a large number of photoelectric conversion elements, and these photoelectric conversion signals are supplied to the signal processing system 34.

FIG. 3 shows the light-sending slit plate 28 in FIG. 1, and in this FIG. 3, the light-sending slit plate 28 is located at positions corresponding to the measurement points P _{11 to} P ₅₃ on the wafer in FIG. Slits 28 _{11 to} 28 ₅₃ are formed. Also, FIG.
Also on the vibrating slit plate 31 inside, as shown in FIG.
Slits 31 _{11 to} 31 ₅₃ are formed on the wafer at positions corresponding to the measurement points P _{11 to} P ₅₃ , respectively, and the vibrating slit plate 31 is vibrated by the vibrator 32 in the measurement direction orthogonal to the longitudinal direction of each slit. ing.

Next, FIG. 5 shows the photoelectric detector 33 in FIG.
5 shows a signal processing system 34. In FIG. 5, the photoelectric conversion elements 33 _{11 to} 33 ₁₃ in the first row on the photoelectric detector 33 are reflected from the measurement points P _{11 to} P _{13 in} FIG.
And the light is incident having passed through the corresponding slits in the vibrating slit plate 31, 2 to fourth rows of the photoelectric conversion elements 33 ₂₁ to
Lights reflected from the measurement points P _{21 to} P _{43 in} FIG. 2 and passing through the corresponding slits in the vibration slit plate 31 are incident on the reference numeral 33 ₄₃ , and the photoelectric conversion elements 33 ₅₁ to
Lights reflected from the measurement points P _{51 to} P _{53 in} FIG. 2 and passed through the corresponding slits in the vibration slit plate 31 are incident on the reference numeral 33 ₅₃ . Then, the photoelectric conversion element 33 ₁₁
The detection signals from 33 33 ₅₃ are supplied to the synchronous rectifiers 47 ₁₁ 47 ₅₃ via the amplifiers 46 ₁₁ 46 ₅₃ . The synchronous rectifiers 47 _{11 to} 47 ₅₃ are driving signals D for the vibrator 32, respectively.
By synchronously rectifying the input detection signal using S, a focus signal that is substantially proportional to the focus position of the corresponding measurement point within a predetermined range is generated. In this embodiment, the focus signals output from the synchronous rectifiers 47 _{11 to} 47 ₅₃ are 0 when the corresponding measurement points in FIG. 1 coincide with the image plane (best focus plane) of the projection optical system 11. Is calibrated so that

The focus signals output from the synchronous rectifiers 47 _{11 to} 47 ₅₃ are supplied in parallel to the multiplexer 48, and the multiplexer 48 synchronizes with the switching signal from the microprocessor (MPU) 50 in the main control system 20. , The focus signals sequentially selected from the supplied focus signals are converted into analog / digital (A / D) converters 49.
, And the digital focus signal output from the A / D converter 49 is sequentially stored in the memory 51 in the main control system 20.

FIG. 6 shows the three actuators 16 of FIG.
A drive system of A to 16C is shown, and in the main control system 20 of FIG. 6, in each address 51 _{11 to} 51 ₅₃ in the memory 51, a digital indicating the focus position at the measurement points P _{11 to} P ₅₃ of FIG. The focus signal of is stored. It should be noted that these focus signals are sequentially rewritten at a predetermined sampling period. Focus signals read from the address 51 _{11-51 53} is supplied to the least square approximation calculation unit 52 and the correction amount calculating unit 53 in parallel. The least-squares approximation calculation unit 52 matches the exposure region 13 in a least-squares manner based on the nine focus signals corresponding to the nine measurement points P _{21 to} P ₄₃ in the exposure region 13 of FIG. The plane is determined, the Z coordinate z at the center of the determined plane, the tilt angle θ _x in the XZ plane, and YZ
Find the tilt angle θ _y in the plane.

In addition, the least-squares approximation calculation unit 52 has a Z coordinate z _r at the center of the image plane of the projection optical system 11, a tilt angle θ _xr in the XZ plane, and a target value setting unit (not shown). The inclination angle Δθ _yr in the YZ plane, that is, the target value of the wafer surface position is also supplied. However, in this embodiment, the target value z _r ,
θ _xr and θ _yr are each 0. Therefore, the least-squares approximation calculation unit 52 calculates the Z coordinate deviation Δz (= −z) obtained by subtracting the actual measurement value from the target value, and the inclination angle deviation Δθ.
_{The x} (= −θ _x ) and the inclination angle deviation Δθ _y (= −θ _y ) are supplied to the gain units 56, 54 and 55, respectively. The Z coordinate deviation Δz, the inclination angle deviation Δθ _x , and the inclination angle deviation Δθ _y are obtained by the following calculations.

[0034]

(Equation 7)

Here, the coordinates of the measurement points P _{21 to} P ₄₃ in FIG. 2 in the X and Y directions with the optical axis of the projection optical system 11, for example, as the origin are (x _i , y _i ) (i = 1 to 1). n; n = 9)
The focus position (Z coordinate) measured at the measurement point of coordinates (x _i , y _i ) is defined as z _i . These Z coordinate deviation Δz, inclination angle deviation Δθ _x , and inclination angle deviation Δθ _y
Are position loop controllers 56, 54 and 55, respectively.
To position loop controllers 56, 54 and 5
5 are multiplied by the appropriate gains k _z , kθ _x and kθ _y , respectively. Then, the position loop controllers 54 and 55
And 56 show the angular velocity ΔVθ in the XZ plane, respectively.
A control signal corresponding to _x , the angular velocity ΔVθ _y in the YZ plane, and the velocity v _z in the Z direction is output, and the angular velocity ΔVθ _x
And the control signal corresponding to ΔVθ _y is the coordinate conversion calculation unit 58.
And the control signal corresponding to the speed v _z is supplied to the adder 57.
Is supplied to.

Further, in FIG. 2, the current scanning of the wafer is performed.
Assuming that the direction is the -X direction, the prefetch area is on the right side of the prefetch area.
The reading area 35A is used to measure the center of the exposure area 13.
Point P ₃₂And the measurement point P at the center of the prefetch area 35A₅₂X direction with
The distance in the direction (this is referred to as d) is calculated in advance by the correction amount calculation in FIG.
It is stored in the unit 53. The correction amount calculation unit 53
Scanning speed of the wafer 12 in the −X direction from the coordinate detection unit 59.
v is also supplied, and the correction amount calculation unit 53 first exposes
Based on focus signals at 9 measurement points in area 13
And the exposure area 13 can be approximated by, for example, a least square method.
Z coordinate z (t) at the center of the surface (hereinafter, the time t is omitted
And the inclination angle θ of the plane in the XZ plane.
It The tilt angle θ in this case is determined by the X-station on the wafer side in FIG.
As a deviation based on the running surface of the 15X in the scanning direction
Desired. After that, the correction amount calculation unit 53
Predicted tilt speed v_zAsk for.

Next, the correction amount calculation unit 53 causes the prefetch area 3
5A based on the focus signal at the center measurement point
Z coordinate z at the measurement point_p And the predicted step speed from (Equation 6)
Degree v _z"And the predicted tilt speed v_z'And the prediction stage
Differential speed v_zThe control signal corresponding to "is supplied to the addition unit 57.
Then, the addition unit 57 sends the speed to the coordinate conversion calculation unit 58.
v_z, V_z'And v_z"V which is obtained by adding"_zAgainst
A corresponding control signal is output. Inclination angle deviation Δ
θ_x, Tilt angle deviation Δθ_y, Z coordinate deviation Δz, and velocity v
_z', V_z"And the angular velocity ΔVθ_x, Angular velocity ΔVθ_y, And fast
Degree ΔV_zThe relationship with is as follows.

[0038]

(Equation 8)

The coordinate conversion calculation unit 58 of FIG. 6 includes three actuators 16 at the time t from the coordinate detection unit 59.
(X ₁ , Y ₁ ), (X ₂ , Y ₂ ), and (X ₃ , Y ₃ ), which are the (X, Y) coordinates of A, 16B, and 16C, are supplied. These (X, Y) coordinates are the X stage 15
It is a value that changes as X moves in the X direction. Then, the coordinate conversion calculation unit 58 calculates the angular velocity ΔVθ _x and the angular velocity Δ.
Actuator 1 for obtaining Vθ _y and velocity ΔV _z
Driving speeds Δv ₁ , Δv ₂ and Δv ₃ of 6A, 16B and 16C in the Z direction are obtained by the following equations.

[0040]

[Equation 9]

The coordinate conversion calculation unit 58 calculates the driving speed Δ
The control signals corresponding to v ₁ , Δv ₂ and Δv ₃ are supplied to the velocity loop controller 60 of the proportional control system. The speed loop controller 60 drives the actuators 16A to 16C via the power amplifiers 61A to 61C. Further, inside the actuators 16A to 16C, speed sensors 45A to 45C (same as the rotary encoder 45 in FIG. 7) for detecting the moving speed are provided, and speed detection signals from these speed sensors 43A to 43C are speed loops. It is fed back to the controller 60. As a result, the actuators 16A to 16C are driven in the Z direction at their tip portions at the driving speeds Δv _{1 to} Δv ₃ . Then, the position and tilt angle of the surface of the wafer 12 after being driven by the actuators 16A to 16C are measured by the multipoint AF sensor 25 in FIG. 1, and the measurement result is fed back to the control system in FIG.

FIG. 8 shows a simplified control unit for the Z coordinate in the control system of FIG. 6, and in FIG.
The target value z _r (t) of the coordinate and the Z coordinate z (t) measured by the multipoint AF sensor are supplied, and the subtraction unit 69 supplies the deviation Δz (t) to the position loop controller 56. Further, the velocity v _z (t) obtained by multiplying the input value by the position loop controller 56 by a predetermined gain is the addition unit 5
7 and the estimated tilt speed v _z
(T) and the predicted step speed v _z "(t) are also supplied, and the speed V obtained by integrating the three speeds by the adder 57
_z (t) is supplied to the subtraction unit 62, and the subtraction unit 62 is also supplied with the speed detected by the speed sensor in the actuator 68 (which is a combination of the actuators 16A to 16C in FIG. 6). That is, the predicted tilt velocity v _z ′ (t) and the predicted step velocity v _z ″ (t) are feed forward.

Then, the speed deviation obtained by subtracting the measured value by the speed sensor from the speed V _z (t) is supplied from the subtraction unit 62 to the speed loop controller 63 of the proportional control system, and the speed loop controller 63 causes the actuator 6 to operate.
8 is supplied with a control signal for driving the actuator 68 at the driving speed V _z (t). Further, the Z coordinate z of the wafer changed by the drive of the actuator 68.
(T) is measured by the multipoint AF sensor, and the measurement result is fed back to the subtraction unit 69.

As described above, according to this embodiment, the wafer 1
Inclination angle θ is detected for scanning plane in the X direction of the X stage 15X 2 on the exposure area 13, the prediction based on the inclination angle inclined velocity v _z 'is obtained, this prediction ramp rate v _z'
The control signal corresponding to is fed forward.
Therefore, when performing the exposure by the scanning exposure method, even if the surface of the wafer 12 is inclined with respect to the running surface of the stage, the exposure region 13 of the wafer 12 always matches the image plane of the projection optical system 11. Exposure is performed in this state, and the entire pattern of the reticle 7 is exposed on the wafer 12 with high resolution.

Further, the focus position in the exposure area 13,
The predicted step speed v _z "is obtained based on the focus position in the prefetch areas 35A and 35B, and the control signal corresponding to the predicted step speed v _z " is fed forward. Therefore, when the exposure is performed by the scanning exposure method, the wafer 1
Even if there is a step on the surface of No. 2, the exposure is performed without the exposure region 13 of the wafer 12 being largely deviated from the image plane of the projection optical system 11.

Although the measurement points P _{21 to} P ₄₃ for tilt detection are distributed in the exposure area 13 in FIG. 2, even if the measurement points P _{21 to} P ₄₃ are out of the exposure area 13. Good. Further, the number and arrangement of the entire measurement points P _{11 to} P ₅₃ are not limited to those in FIG. 2, and the measurement points may be arranged in different steps in the X direction, for example. Further, in the above embodiment, the wafer 12
The multi-point AF sensor 25 is used to detect the tilt angle of the upper exposure area 13. Instead, for example, the surface of the wafer 12 is obliquely irradiated with a parallel light beam and the converging position of the reflected light is changed. A parallel light beam oblique incidence type leveling sensor that detects the inclination angle of the surface from the lateral shift amount may be used.

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

[0048]

According to the present invention, the inclination angle detecting means detects the inclination angle of the photosensitive substrate as an object to be focused,
The predicted tilt speed obtained based on this tilt angle is taken into consideration. Therefore, even when the substrate is tilted when the exposure is performed by the scanning exposure method, the speed signal supply means drives the height adjusting means by a simple closed loop control of only proportional control, thereby relatively There is an advantage that the autofocus of the substrate can always be performed with high accuracy without causing a steady deviation with a small gain. Therefore, since it is not necessary to configure a high-order servo system, the servo system can be easily tuned and the stability (robustness) can be improved.

Further, when the focus position pre-reading means is provided and the predicted step speed based on the step between the exposure area on the substrate and the pre-reading area is taken into consideration, even if there are irregularities or steps on the surface of the substrate, Smooth follow-up of the image plane of the projection optical system is possible, and improvement in auto-focus followability can be expected.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a scanning exposure type projection exposure apparatus to which an embodiment of a surface position setting apparatus according to the present invention is applied.

FIG. 2 is a plan view showing a distribution of measurement points of focus positions on the wafer 12 of FIG.

FIG. 3 is a diagram showing a light-sending slit plate 28 in FIG.

FIG. 4 is a diagram showing a vibrating slit plate 31 in FIG.

5 is a photoelectric detector 33 and a signal processing system 34 in FIG.
FIG.

6 is a configuration diagram including a partial perspective view showing a focus / leveling mechanism of a wafer 12 in FIG. 1 and a control system thereof.

FIG. 7 is a partial cross-sectional configuration diagram showing a configuration example of an actuator 16A in FIG.

8 is a block diagram showing a simplified control system of the focus / leveling mechanism of FIG.

FIG. 9 is a diagram for explaining the principle of the present invention.

FIG. 10 is a diagram showing a case where the surface of the photosensitive substrate is inclined.

FIG. 11 is a diagram showing a case where there is a step on the surface of a photosensitive substrate.

FIG. 12 is a block diagram showing a control system of a conventional autofocus mechanism.

FIG. 13 is a diagram showing a case where there is a step on the surface of the wafer in the scanning exposure apparatus.

[Explanation of symbols]

7 reticle 9 reticle stage 11 projection optical system 12 wafer 13 exposure area 14 focus / leveling stage 15Y Y stage 15X X stage 16A to 16C actuator 19, 23X, 23Y laser interferometer 20 main control system 25 multipoint AF sensor P _{11 to} P ₅₃ measurement point 33 photoelectric detector 34 signal processing system 35A, 35B look-ahead region 52 least square approximation calculation unit 53 correction amount calculation unit 54, 55, 56, 57 position loop controller 58 coordinate conversion calculation unit 59 coordinate detection unit 60 speed loop controller 63 Velocity loop controller 68 Actuator

Claims (2)

[Claims] 1. A mask on which a transfer pattern is formed is illuminated with exposure illumination light, and the pattern of the mask is projected into an exposure area on a photosensitive substrate on a substrate stage via a projection optical system. Then, in synchronization with scanning the mask in a predetermined direction, the substrate is scanned in the predetermined direction via the substrate stage to sequentially expose the pattern of the mask on the substrate. Provided on the device,
An apparatus for setting the position of the surface of the substrate in the optical axis direction of the projection optical system to a predetermined position, in which the projection optical system is driven in the optical axis direction on the substrate stage according to a drive signal supplied. Height adjusting means for controlling the position of the substrate in the optical axis direction of the projection optical system at a speed; a position in the optical axis direction of the projection optical system at a measurement point in an exposure area of the projection optical system on the substrate A focus position detecting means for detecting a tilt angle detecting means for detecting a tilt angle of a predetermined measurement area including a measurement point in the exposure area with respect to a running surface of the substrate stage; and light of the projection optical system of the substrate. A drive signal indicating a target speed according to a difference between a target position in the axial direction and a position detected by the focus position detection means, a tilt angle detected by the tilt angle detection signal, and a scanning speed of the substrate stage. According to the product A surface position setting device comprising: a speed signal supply unit that supplies a drive signal obtained by adding a drive signal indicating a predicted tilt speed to the height adjusting unit. 2. A focus position pre-reading means for pre-reading the position in the optical axis direction of the projection optical system at a measurement point preceding the exposure area on the substrate in the scanning direction is provided, and the speed signal supplying means is According to the sum signal of the drive signal indicating the target speed and the drive signal indicating the predicted tilt speed, further, the difference between the position pre-read by the focus position pre-reading means and the position detected by the focus position detecting means. 2. The surface position setting device according to claim 1, wherein a drive signal obtained by adding a drive signal indicating a predicted step speed is supplied to the height adjusting means.