JPH06275518A - Aligner for periphery of substrate - Google Patents

Abstract

PURPOSE:To stably perform the marginal exposure with high precision by a method wherein, when an irradiating means reaches a detected control unstable region in order to relatively shift the irradiating means along the marginal part of a substrate, the servo-gain to deflection signal of a relative position control means is decreased. CONSTITUTION:The title marginal aligner of substrate is provided with an irradiating means 101 capable of irradiating a substrate 100 with exposure flux E and a deflection signal output means 102 outputting the deflection signal corresponding to the deflection from the target value of the relative positions in the exposure width direction of the irradiating means 101 and the substrate 100. Furthermore, an unstable region detecting means 104 detecting a control unstable region on the marginal part of the substrate 100 according to the deflection signal, a gain changing means 105 decreasing the servo-gain to the deflection signal of a relative position control means 103 when the irradiating means 101 reaches the detected control unstable region are provided. Through these procedures, the deterioration in the stability of a control system due to the enlarged deflection can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for exposing a peripheral portion of a substrate such as a semiconductor wafer for manufacturing a semiconductor element.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor wafer, in order to prevent the resist from peeling off at the peripheral edge of the substrate, the peripheral edge of the substrate may be exposed with a predetermined exposure width (for example, about 1 to 7 mm). As an apparatus used for this type of exposure, for example, as described in Japanese Patent Laid-Open No. 4-72614,
An irradiation unit capable of irradiating an exposure light beam toward the substrate, a moving mechanism for moving the irradiation unit in the radial direction of the substrate, and a control mechanism for servo-controlling the drive amount of the moving mechanism are provided. It is known that when the substrate is rotated while irradiating the peripheral portion of the substrate, the moving mechanism is servo-controlled so that the deviation between the irradiation width of the substrate and the target value becomes zero.

[0003]

In the above-mentioned device, when the servo gain of the control mechanism is increased, the followability of the irradiation unit to the change of the outer peripheral position of the substrate is improved, but the position where the outer peripheral shape of the substrate changes discontinuously, For example, at the boundary portion of an orientation flat (hereinafter referred to as OF) formed for aligning the wafer, a V-shaped notch formed instead of OF, or a defective portion formed at the peripheral portion of the wafer, deviation is caused. Of the exposure section excessively responds to the rapid expansion of the exposure area and hunting occurs, and the control system becomes unstable and the exposure width varies. If the servo gain is lowered in order to avoid this, the control system becomes stable, but the followability of the irradiation unit with respect to changes in the outer peripheral position of the substrate decreases, and the exposure accuracy deteriorates.

It is an object of the present invention to provide a substrate edge exposure apparatus capable of stably and accurately performing edge exposure even on a substrate having a portion whose outer peripheral shape changes discontinuously.

[0005]

The present invention will be described with reference to FIG. 1. In the present invention, an irradiation means 101 capable of irradiating a substrate 100 with an exposure light flux E, and an irradiation means 101 for the substrate 100.
When the relative movement is performed along the peripheral portion of the
And a deviation signal output means 10 for outputting a deviation signal corresponding to the deviation of the relative position of the substrate 100 in the exposure width direction from the target value.
2 and the relative position control means 103 for controlling the relative position so as to reduce the deviation based on the deviation signal. The above-described purpose is to move the irradiation region 101 relative to the unstable region detection unit 104 that detects the control unstable region on the peripheral region of the substrate 100 based on the deviation signal and the irradiation unit 101. This is achieved by providing gain changing means 105 that lowers the servo gain for the deviation signal of the relative position control means 103 when the irradiation means 101 reaches the detected control unstable region. The unstable region detecting means 104 determines that the control signal is an unstable region when the deviation signal exceeds a predetermined value or when the deviation signal tends to diverge.

[0006]

When the irradiation means 101 reaches the control unstable area detected by the unstable area detecting means 104, the gain changing means 1
Reference numeral 05 reduces the servo gain for the deviation signal of the relative position control means 103, and prevents the stability of the control system from being deteriorated due to the expansion of the deviation.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 2 is a diagram showing a schematic configuration of an exposure apparatus according to the present embodiment. Reference numeral 1 is a wafer to be exposed, 2 is a turntable (hereinafter, abbreviated as a table) that sucks and holds the wafer 1, and 3 is a table 2. A motor 4 for rotational driving, a rotational position detector such as a rotary encoder for outputting a signal corresponding to a rotational position of the motor 3, and a reference numeral 5 are bases for rotatably supporting the table 2. The motor 3 rotationally drives the table 2 so that the wafer 1 rotates in a plane substantially perpendicular to the rotation axis of the motor 3. 6 is a light source using an ultra-high pressure mercury lamp or the like, the illumination light of which is an elliptical mirror 7, a mirror 8,
The light enters the lens 11 via the shutter 9 and the wavelength selection filter 10, is condensed on the end face of the optical fiber 12, and is guided to the irradiation unit 14. Reference numeral 13 denotes a drive unit for inserting the wavelength selection filter 10 in the optical path or for retracting it from the optical path. When the filter 10 is inserted in the optical path, the illumination light in the wavelength range having high sensitivity to the resist of the wafer 1 is cut. It
The light flux in the wavelength range cut by the filter 10 is the exposure light flux, and hereinafter, the light flux that has passed through the filter 10, that is, the light flux that does not include the exposure light flux is referred to as a non-exposure light flux.

Reference numeral 15 is a diaphragm for shaping the illumination light beam 16 emitted from the irradiation unit 14 into a desired shape (rectangular shape in this embodiment), and 17 is a light receiving device for receiving the illumination light beam 16 and outputting a signal according to the light receiving state. And 18 are an irradiation unit 14 and a light receiving unit 1.
It is a holder that integrally holds 7. The holder 18 is movable along with a slider 22 on a linear guide 21 attached to the base 5, and when the holder 18 is brought closer to the wafer 1 side, a peripheral portion of the wafer 1 is provided between the irradiation section 14 and the light receiving section 17. Goes in. When the holder 18 is moved to the region farthest from the wafer 1, the dummy wafer 20 is inserted between the irradiation unit 14 and the light receiving unit 17. 19 is a holder 18
Is a position detector for detecting the position of the holder 18 when the position is within a certain range from the left end position in the figure.

As shown in FIG. 3, the light receiving portion 17 has a pair of rectangular light receiving elements 17a extending in the moving direction of the holder 18 (direction of arrow S) and a predetermined edge from the edge of the illumination light beam 16 on the wafer 1 side. It has a pinhole-shaped edge sensor 17b spaced apart by a distance L, and a light-receiving element 17c arranged near the edge of the illumination light beam 16 on the side opposite to the wafer 1. A part of the light receiving element 17a is covered by the peripheral portion of the wafer 1 or the edge 20a of the dummy wafer 20 according to the movement of the holder 18, and the illumination light beam 16 reaches the light receiving portion 17 without being shielded by these (see FIG. 2). ) The signal Se corresponding to the light intensity of The edge sensor 17b outputs a signal B having a different level depending on whether or not the illumination luminous flux 16 is received. The light-receiving element 17c always receives the illumination light beam 16 on its entire surface regardless of the position of the holder 18, and outputs a signal C corresponding to the intensity of the illumination light beam 16.

As shown in FIG. 2, the moving block 23 attached to the lower surface of the slider 22 is constantly urged to the right in the drawing by a spring (not shown), and the rollers 25, 26 are responsive to the rotational position of the rotary arm 24. Press contact with any of. Accordingly, when the rotating arm 24 is rotated by the motor 27, the moving block 23 moves on the linear guide 21 according to the rotating direction and the amount of rotation, and the position of the holder 18 changes. The rotational position of the motor 27 is detected by a rotational position detector 28 such as a rotary encoder shown in FIG.

FIG. 4 is a block diagram of a control system of the exposure apparatus of this embodiment. The control unit 30 outputs a drive signal to the drive circuits 31 and 32 to control the rotation of the motors 3 and 27, and outputs a drive signal to the drive unit 13 to control the operation of the filter 10. As information for control, the control unit 30 outputs the motors 3, 27 output by the rotational position detectors 4, 28.
, A signal corresponding to the position of the holder 18 output by the position detector 19, and a signal corresponding to the light receiving state output by the light receiving unit 17 are input, and control is performed based on these signals. The unit 30 executes various processes described below.
33 is an external memory of the control unit 30. The control unit 3
Information about the type of wafer 1 and exposure conditions is given to 0 by a commander (not shown). This information includes information about the diameter of the wafer 1, the presence / absence of OF, the shape and size of the OF, the exposure amount of the wafer 1, and the target exposure width of the peripheral portion.

The drive circuit 32 controls the motor 27 so that the deviation signal Sd or Sf given from the control unit 30 becomes zero.
To drive. The servo gain of the drive circuit 32 for the deviation signal Sf is set according to the servo gain setting signal from the second control unit 34. The deviation signals Sd and Sf and the processing in the second controller 34 will be described later.

Next, the processing by the control unit 30 will be described with reference to FIGS. 6 and 7. In addition, in the following description, FIG.
As an example, as shown in (a), the peripheral portion of the wafer 1 having OF is exposed with a constant width M. It is assumed that there is a substantially V-shaped defect D near the OF in the peripheral portion of the wafer 1.

FIG. 6 is a flow chart showing a series of processing by the control unit 30. The wafer 1 to be exposed is attracted to the table 2, and when the information regarding the type and the exposure condition is input, the illustrated process is started. First, in step S1, the rotation speed of the motor 3 is calculated based on the signal C from the light receiving element 17c of the light receiving unit 17 so that exposure is performed with an exposure amount suitable for the resist of the wafer 1, and the calculation result is obtained. It is stored as speed information.

In step S2, a calibration process for measuring the output signal of the light receiving section 17 corresponding to the target exposure width M is performed. That is, the edge 20 of the dummy wafer 20
a by gradually moving the holder 18 toward the edge 20a.
The position detector 19 detects a position at which the signal B has reached the edge sensor 17b and the level of the signal B has changed. Then, the holder 18 is moved to the wafer 1 side or the opposite side by the difference between the target exposure width M and the distance L (see FIG. 3), and the signal Se of the light receiving element 17a at that time is divided by the signal C of the light receiving element 17c. The calculated value Se / C is stored as the reference signal Sb. Signal Se
Is used to eliminate the influence of the change in the signal Se due to the change in the intensity of the illumination light beam 16. Hereinafter, for convenience, Se / C is referred to as an output signal from the light receiving unit 17.

In step S3, the OF position of the wafer 1 is detected. That is, with the holder 18 fixed at a position where a part of the illumination light beam 16 overlaps the peripheral edge of the wafer 1, and the filter 10 is inserted in the optical path of the illumination light to make the illumination light beam 16 a non-exposure light beam, 1 is rotated at a constant speed to record the change in the signal Se / C from the light receiving unit 17. The recorded waveform gradually changes according to the eccentricity state of the wafer 1 as shown in FIG. 7A, and the received light amount of the light receiving element 17a on the OF and the defect D changes sequentially. It changes rapidly. Which of the regions An in which the signal Se / C suddenly changes corresponds to the OF is given as O beforehand.
The determination is made based on the information regarding the shape and size of F. As the discrimination information, for example, the central angle θn of the change area An or Se /
The change amount δ of C is used. It may be determined by a waveform obtained by differentiating the signal Se / C. The center of the area A2 determined to be OF is stored as the center position of OF in association with the rotation position of the table 2. The stored information is used for indexing the rotational position of the wafer 1 and the like in the subsequent processing.

As shown in FIG. 5A, the exposure width of the contact portions 45a to 45c with the claw for holding the wafer of the exposure apparatus is made larger than the target exposure width M in preparation for contact with the claw for holding the wafer. When setting, the angles α1 to α3 from the center position of the OF of the contact portions 45a to 45c are given in advance as information regarding the wafer 1, and based on this information and the detected position of the OF, the contact portions 45a to 45c are set. Just figure out the position.

In step S4, dummy tracking processing is performed. In this process, the wafer 1 is rotated at least once while the filter 10 is inserted in the optical path of the illumination light, and the reference signal Sb (the signal Se / C corresponding to the target exposure width M) detected in the calibration process of step S2 is used. , The deviation signal Sd corresponding to the deviation from the output signal Se / C from the light receiving unit 17 at the present time is output to the drive circuit 32, and the holder 18 is moved according to the rotational position of the wafer 1 so that the deviation signal Sd becomes zero. Adjust the position of. At the time of dummy tracking, the wafer 1 is detected based on the output signal of the rotational position detector 28.
The position of the holder 18 in the radial direction is detected, and the detection result is stored in the memory 33 in association with the rotational position of the wafer 1. In the dummy tracking, since the holder 18 moves in the radial direction of the wafer 1 so that the target exposure width M is maintained, the data regarding the position of the holder 18 stored in the memory 33 is the exposure width of the wafer 1 as the target exposure width. The target position of the holder 18 for each rotational position of the wafer 1 required to maintain M is shown.

After completion of dummy tracking, step S5
Proceed to and perform exposure. In this exposure, the filter 10 is retracted from the optical path, the illumination light beam 16 is used as the exposure light beam, and the table 2 is rotated at the speed obtained in step S1. Then, the memory 3 corresponding to the rotation position of the table 2
3, the target position of the holder 18 is read, and the deviation signal Sf corresponding to the deviation between the target position and the current position of the holder 18 detected by the rotational position detector 28 is output to the drive circuit 32 and the second position.
To the control unit 34. At this time, the drive circuit 32
The motor 27 is driven so that the above-mentioned deviation signal Sf becomes zero by the servo gain according to the gain setting signal output from the second control unit 34. As a result, the holder 18 moves along the outer periphery of the wafer 1 and the exposure width is maintained at the target exposure width M.

FIG. 8 is a flow chart showing the processing of the second control section 34 during the above-mentioned exposure. Control unit 30
When the deviation signal Sf is output from, the illustrated process is started. In step S11, the servo gain is set to a predetermined initial value. This initial value is set relatively high, giving priority to the control accuracy of the exposure width. In step S12, the control unit 3
The deviation signal Sf is received from 0. In step S13,
Whether the absolute value of the deviation signal Sf is higher than a predetermined threshold value TH, and whether the difference ΔSf between the absolute value of the deviation signal Sf input this time and the absolute value of the previous deviation signal Sf is larger than zero is determined. If it is determined that either one is affirmative, the process proceeds to step S14. When step S13 is denied, it returns to step S11 and sets a servo gain to an initial value. It should be noted that whether or not the deviation between the target position and the current position of the holder 18 tends to diverge is determined by whether or not ΔSf is greater than zero. The divergence tendency of the deviation may be judged not only by the difference between the absolute values of the deviation signal Sf of the previous time and this time but also by comparing the absolute values of three or more deviation signals Sf that are consecutive.

At step S14, the current deviation signal Sf
And a servo gain corresponding to ΔSf are calculated, and a gain setting signal corresponding to the calculation result is output to the drive circuit 32 to reduce the servo gain from the initial value set in step S11. The correspondence between the deviation signals Sf and ΔSf and the change in the servo gain is that the servo gain continuously decreases as the deviation signals Sf and ΔSf increase, and the deviation signal Sf changes.
Or the servo gain may be reduced in two or more steps corresponding to ΔSf.

FIG. 7B shows the deviation signal Sf corresponding to the change in the outer peripheral position of the wafer 1 shown in FIG. As described above, since the outer peripheral position of the wafer 1 changes abruptly on the OF and the defect D (see FIG. 5), in the OF (area A2) that is long in the circumferential direction, the boundary position at both ends of the OF causes the circumferential direction in the circumferential direction. In the short defect D (area A1), the deviation signal Sf
Greatly increases and decreases. Therefore, when the processing of the second control unit 34 described above is performed based on the deviation signal Sf of FIG. 7B, the exposure light flux for the wafer 1 reaches the boundary portion between the defects D and OF as shown by the hatched lines in the figure. Deviation signal Sf
The absolute value of exceeds the threshold value TH, the servo gain of the drive circuit 32 decreases, and the responsiveness of the holder 18 to the deviation signal Sf decreases. Further, the servo gain also decreases in a region where the deviation signal Sf increases in the positive or negative direction.

As a result, as shown in FIG.
At the boundary portion of (3), the variation of the exposure width (width of the shaded portion in the figure) converges at an early stage. If the servo gain remains high, as shown by the chain double-dashed line in the figure, the convergence of the exposure width variation at the OF boundary is delayed. Further, on the defect D, the exposure light flux passes along the outer peripheral shape before and after the defect D with hardly following the defect D. For this reason, the exposure width does not unnecessarily expand toward the center of the wafer 1, the area of the region surrounded by the peripheral exposure portion of the wafer 1 increases, and the chip yield improves. By the way, if the servo gain on the defect D is still high, the holder 18 follows the wafer 1 in the radial direction of the wafer 1 with good response to match the exposure width with the target value even if the defect D should be ignored. As indicated by the two-dot chain line, the peripheral exposure portion expands toward the center of the wafer 1 and the chip yield deteriorates.

In the apparatus of the embodiment, as shown in FIG.
When the exposure width is changed by the contact portions 45a to 45c shown in (4), the data regarding the target position of the holder 18 obtained by the dummy tracking may be corrected at the positions of the contact portions 45a to 45c. In this case, the contact portions 45a to 45 are exposed at the time of exposure.
The deviation signal Sf expands even at the boundary portion of c and the second control unit 3
The change of the servo gain by 4 is executed. As a result,
Even at the boundaries between the contact portions 45a to 45c, the variation in the exposure width is quickly converged.

In the present embodiment, the apparatus for controlling the exposure width by the deviation signal Sd corresponding to the deviation between the target position of the holder 18 obtained by the dummy tracking process and the current position of the holder 18 at the time of exposure is taken as an example. The present invention is not limited to this. Even when the dummy tracking is omitted and the exposure width is controlled by the deviation signal Sd corresponding to the deviation between the reference signal Sb from the light receiving unit 17 obtained by the calibration process and the current output signal Se / C from the light receiving unit 17, , Deviation signal S
The servo gain may be changed according to d. Further, the servo gain may be changed based on the deviation signal Sd during the dummy tracking. The deviation signal Sd output from the control unit 30 during both dummy tracking and exposure
The servo gain may be changed based on Sf.

In the correspondence between the above embodiment and the claims,
The wafer 1 is the substrate, the irradiation unit 14 is the irradiation means, and the control unit 3
0 is the deviation signal output means, the drive circuit 32 and the motor 2
Reference numeral 7 constitutes a relative position control means, and the second control portion 34 constitutes an unstable area detection means and a gain changing means. Relative rotation between the light flux from the irradiation means and the substrate can be obtained by rotating the light flux side along the substrate. The relative movement of the light flux from the irradiation means and the substrate in the exposure width direction can be obtained even by moving the substrate side. The substrate is not limited to a circular shape and may be a polygonal one.

[0027]

According to the present invention, since the deviation between the relative position of the irradiation means and the substrate in the exposure width direction and the target value increases, the servo gain decreases in the area where the stability of the control system deteriorates. The original servo gain of is set to a high value to maintain high accuracy of the exposure width, while ensuring stability of the control system in the area where the outer peripheral shape of the substrate and the exposure width change discontinuously. High edge exposure can be stably performed. Also,
In particular, in a minute defective portion where it is not necessary to maintain the exposure width at the target value, the exposure light beam can be relatively moved so as to be ignored, and unnecessary expansion of the peripheral edge exposed portion of the substrate can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a diagram showing a schematic configuration of an exposure apparatus of an embodiment of the present invention.

FIG. 3 is a diagram showing details of a light receiving unit in FIG.

4 is a block diagram of a control system of the exposure apparatus of FIG.

5A and 5B are diagrams showing an example of a wafer to be exposed by the exposure apparatus of FIG. 2, FIG. 5A is a plan view of the wafer, and FIG. 5B is an enlarged view of the vicinity of OF after exposure.

6 is a flowchart showing a processing procedure in the control unit of FIG.

7A and 7B are diagrams showing input / output waveforms of the control unit when the wafer of FIG. 5 is an exposure target. FIG. 7A is an input waveform from the light receiving unit to the control unit during OF detection processing, and FIG. The waveform of the deviation signal Sf output from the control unit to the drive circuit and the second control unit during exposure is shown.

FIG. 8 is a flowchart showing a processing procedure of a second control unit in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wafer 6 Light source 14 Irradiation unit 16 Irradiation light flux 17 Light receiving unit 27 Motor 28 Rotation position detector 30 Control unit 32 Drive circuit

Claims (3)

[Claims] 1. An irradiation unit capable of irradiating a substrate with an exposure light beam, and a relative position of the irradiation unit and the substrate in an exposure width direction when the irradiation unit is relatively moved along a peripheral portion of the substrate. Edge exposure of a substrate provided with a deviation signal output means for outputting a deviation signal corresponding to a deviation from a target value, and a relative position control means for controlling the relative position so as to reduce the deviation based on the deviation signal. In the apparatus, an unstable area detection unit that detects a control unstable area on the peripheral edge of the substrate based on the deviation signal; and an irradiation unit when the irradiation unit is relatively moved along the peripheral edge of the substrate. And a gain changing means for reducing the servo gain of the relative position control means with respect to the deviation signal when the control unstable region is detected. Light equipment. 2. The substrate edge exposure apparatus according to claim 1, wherein the unstable area detecting unit determines the control unstable area when the deviation signal exceeds a predetermined value. 3. The substrate edge exposure apparatus according to claim 1, wherein the unstable area detecting unit determines the control unstable area when the deviation signal tends to diverge.