JPH0878302A - Exposure system - Google Patents

Abstract

PURPOSE: To improve the productivity of exposure operation by carrying out processing without diaplacing the place of the pre-alignment of a wafer at the time of delivery with a wafer carrier system in an exposure system. CONSTITUTION: Locating pins 10a, 10b pre-aligning a wafer and an alignment mechanism 11 are mounted on a wafer carrying arm 8 carrying the wafer 1 onto an exposure stage 9. Accordingly, positional displacement generated when the pre-alinged wafer is delivered to the wafer carrying arm 8 is prevented, and the exposure operation of the wafer can be conducted with stable pre- alignment accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus, and more particularly to a semiconductor wafer pre-alignment mechanism provided in the exposure apparatus for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art Photolithography technology is repeatedly used for semiconductor wafers in the process of manufacturing semiconductor devices.
This photolithography technique requires an exposure device for forming a pattern of a resist film applied on a semiconductor wafer. In this type of exposure apparatus, it is essential to set the semiconductor wafer at an accurate position on exposure, and the accuracy of this alignment is one of the factors that determine the degree of integration of the circuits in the semiconductor wafer.

A semiconductor wafer is provided with a linear notch on a part of its circumference, which is called an orientation flat (orientation flat for short). With the orientation flat portion as a reference, the rotation angle of the wafer can be adjusted to be constant.

Next, how much the semiconductor wafer deviates from the reference position can be expressed by an X axis and a Y axis along the main surface of the wafer and a Z axis perpendicular to the main surface of the wafer. If some kind of mark such as a resist film or a thin film left by this is formed on the surface, it is easy to detect the deviation of the X axis and the Y axis, but such a mark is still formed on the main surface. In the case of the first step, which has not been performed, a part on the circumference of this wafer must be used as a reference. Since the Z axis is determined by the height position of the stage having the plane formed by the X and Y axes on which this wafer is placed, it is easy to detect the deviation from the reference position.

As described above, it is necessary to accurately detect the position of the semiconductor wafer and to know the extent of the deviation before exposing the semiconductor wafer. Then, the deviation is accurately moved on the basis of this deviation. Control means are required.

In order to perform such accurate alignment,
There is a fine adjustment mechanism (also referred to as a fine alignment mechanism) for finally performing accurate alignment of the semiconductor wafer immediately before the exposure. Before this fine adjustment, a predetermined adjustment is made so that this mechanism can detect the displacement of the semiconductor wafer. Must be within the range. A semiconductor wafer that is misaligned outside the predetermined range is out of the dynamic range and can no longer be detected by the fine adjustment mechanism, and fine adjustment must be performed manually. This coarse adjustment mechanism at the previous stage is also called a pre-alignment mechanism.

Referring to the top view of FIG. 4 showing an exposure apparatus having such a fine and rough adjusting mechanism, this apparatus has a wafer transfer section 4 driven by a pulse motor 12 and the like,
A pre-alignment stage 5, a wafer transfer arm 8 driven by a pulse motor 13 and the like, and an exposure stage 9 are provided, and the main body and control means for fixing them are not shown.

The semiconductor wafer is placed in the wafer carrier 3.
A large number of sheets are vertically stacked at a predetermined interval and have openings so that they can be sequentially taken out one by one from the side surface of the carrier 3. The carrier 3 is manually or automatically placed at a fixed position in the exposure apparatus. Fixed. Wafer transfer unit 4
The semiconductor wafers 1 housed in the carrier 3 are sequentially adsorbed or pinched, taken out in the Y-axis direction, rotated 180 ° on a plane, and transferred onto the pre-alignment stage 5. Here, the orientation flat 2 of the semiconductor wafer 1 in the carrier is at a random position, and the orientation flat 2 of the wafer 1 on the stage 5 is also at a random position. The transferred wafer 1 is set so that the center of the wafer is aligned with the center of the wafer chuck 7, and is fixed to the wafer chuck 7 by suction. In this state, the wafer chuck 7 rotates and the wafer 1 also rotates. The orientation flat 2 is the orientation flat detector 6
The transmitted light obtained when passing through is converted into an electric signal, and the stop position of the wafer 1 is determined by this electric signal,
Coarse adjustment or pre-alignment is performed. When this pre-alignment is completed, the wafer chuck 7 moves the wafer 1
Then, the wafer 1 is gently released. Then, the wafer transfer arm 8 receives the wafer 1 in a suction-fixed form, and transfers the wafer 30 onto the exposure stage 9 in the Y-axis direction along the Y-axis direction.

Wafer 4 set on exposure stage 9
In the case of 0, the exposure operation is performed as it is in the first exposure, but in the second and subsequent exposures, the alignment mark on the main surface of the wafer 40 is detected by the electro-optical means, and the fine adjustment of the wafer position is automatically performed. (Fine alignment) (this part is not shown). Here, when the position adjustment by the pre-alignment on the stage 5 is bad, that is, when there is no alignment mark on the main surface of the wafer 1 within a fine adjustment range, for example, within ± 50 μm, this can be automatically detected. As a result, fine adjustment is not possible and must be done manually.

As a cause for making fine adjustment impossible,
Although there is accuracy of pre-alignment on the stage 5, in addition to this, positional displacement due to mechanical micro-vibration when the wafer transfer arm 8 adsorbs the wafer 20 and micro-vibration of the arm 8 during transfer of the wafer 30 are performed. Displacement due to
When the arm 8 sets the wafer 40 on the exposure stage 9, there is a positional deviation due to mechanical micro-vibration, etc. If a vector positional deviation that adds these causes occurs, fine adjustment becomes impossible, If there is a positional deviation of the vectors that cancel each other out, the range will be finely adjustable. When such a control system is operated at a high speed, an accident that fine adjustment is not possible frequently occurs, and the positional deviation of the wafer 40 is not always a fixed amount of deviation, but is different for each individual wafer. There was found.

On the other hand, when fine adjustment is performed, the amount of displacement of the wafer is measured, and the value is fed back to the pre-alignment controller as a correction amount at the pre-alignment stage. Referring to, when the wafer rotation angle 0 is corrected in the fine adjustment stage, the correction amount is directly corrected in the coarse adjustment stage,
The technique to eliminate the inability to make fine adjustments is described.

[0012]

In the former exposure apparatus described above, the wafer 20 is transferred to the wafer transfer arm 8 for transferring the wafer 20 to the exposure stage 9 after the completion of the pre-alignment. The wafer 20 is held in a free state by releasing the suction. Furthermore, depending on the flatness of the wafer and the surface condition of the wafer transfer arm 8,
When the wafer suction is released, the wafer 40 is displaced,
In particular, in the second exposure, there is a case that it is out of the automatic fine adjustment range, and there is a problem that the operator needs to perform manual adjustment. In particular, if a positional deviation occurs during pre-alignment or the like, the alignment mark position deviates from the detection range, that is, the searchable area. In that case, the device that was working automatically generated an error because alignment could not be done,
Waiting for operator assistance. The operation is stopped until the operator finds an error and manually adjusts (searches for the alignment mark and moves it within the detection range), and the productivity of the apparatus is significantly deteriorated.

In the exposure apparatus, since a plurality of different patterns, especially about 20 different patterns, are transferred in superposition to make one product, it is necessary to align the wafers for each pattern, and it is necessary to manually perform every step (other than 1st). Adjustments may be needed.

Further, in the latter exposure apparatus, since the fine adjustment amount is fed back to the coarse adjustment mechanism as it is, the positional deviation which occurs between the fine and coarse adjustment mechanisms described above and which has a different correction amount for each wafer is corrected. There is a drawback that you cannot do it. That is, the positional deviation that occurs when the wafer 30 is transferred onto the transfer arm 8 is not always a constant amount and a constant direction. This depends on the degree of warpage of the wafer 30 and the state of the contact surface between the transfer arm 8 and the wafer 30. Therefore, it is difficult to follow up with feedback control, the program control system becomes complicated, and man-hours are required for optimization. Further, there is no description about how to combine the automatic correction amount in the pre-alignment stage with the feedback correction amount, and there is a drawback that a complicated program control means is required.

In view of the above problems, the present invention has the following problems. (1) Make sure that all semiconductor wafers are within the fine adjustment range in the fine adjustment stage. (2) Make sure that there are no major structural changes that accompany changes in the design of the conventional pre-alignment stage, wafer transfer unit, etc. (3) To prevent misalignment during wafer transfer. (4) To improve productivity by eliminating manual operations.
(5) Shorten the pre-alignment time. (6) To reduce the occurrence of dust, dirt and the like on the stage due to the pressure between the back surface of the wafer and the wafer chuck, thereby preventing the alignment accuracy from deteriorating.

[0016]

The structure of the present invention comprises a pre-alignment stage for aligning a semiconductor wafer, and a wafer transfer means for transferring the wafer aligned by the stage to an exposure stage. In the exposure apparatus described above, the wafer transfer means is provided with an alignment mechanism for aligning the wafer, and in particular, the alignment mechanism sandwiches three side faces including an orientation flat of the semiconductor wafer to perform the alignment. It is a mechanism for performing.

In addition, in particular, the first pin having a flat surface for abutting the side surface of the orientation flat portion of the wafer and the line substantially parallel to the flat line passing through the approximate center of the wafer. A second pin that abuts a side surface of the wafer, and a third pin that elastically presses the wafer so that the first and second pins abut the side surface of the wafer. To do.

Further, in particular, the wafer transfer means has a control means for releasing the wafer sandwiched by the alignment mechanism after the wafer is adsorbed on the exposure stage.

Further, in particular, the control means separates the third pin from the side surface of the wafer and then separates the first and second pins from the side surface of the wafer when releasing the wafer. It is characterized by having means for controlling.

[0020]

1 is a top view showing an exposure apparatus according to an embodiment of the present invention. In FIG. 1, the exposure apparatus of the present embodiment has a positioning pin 10a that defines the position of the orientation flat 2 on the wafer transfer arm 8 and a line that passes through the center of the wafer 20 among the straight lines parallel to the side surfaces of the orientation flat 2. A positioning pin 10b that defines a point that intersects with the outer circumference of 20 and a positioning mechanism 11 that presses the wafer 20 against these positioning pins 10a and 10b are provided.

The parts other than the wafer transfer arm 8 and the wafer transfer control part are common to those of the conventional example shown in FIG. 1, and the description of the common parts will be omitted.

The wafer transfer arm 8 is shown in FIG.
As shown in the top view of (a) and the side view of (b), four through holes 35 are opened in the main surface of the U-shaped main body 50.

The positioning pin 10a is provided with a pair, that is, two cylindrical pins, and through holes 35 into which the pins 10a are inserted are opened in the main body 50, respectively. At least two pins are required to align the side faces of the orientation flat of the wafer 30 for contact. Placed wafer 30
In order to move these pins 10a toward the center of the wafer 30 to contact the orientation flat of the mounted wafer 30, it is necessary to move toward the center of the wafer 30. Each through hole 35 is formed.

When the wafer 30 is delivered, the wafer 3
Driving means 10a '(for example, a driving device including an air cylinder, a pulse motor, etc.) for driving the pin 10a in the direction opposite to the center direction of 0 is fixed to the back surface of the main body 50.

Since the maximum movement position of the wafer 30 in the center direction is related to the diameter of the wafer 30 prepared here, a known setting position such as a position adjusting device having a micrometer can be appropriately adjusted. Variable means may be further added.

A through hole 35 having a play is opened in the main body 50 so that the positioning pin 10b can move in the diameter direction of the wafer 30. The fixed position of the pin 10b is on a line passing through substantially the center of the wafer 30 among the lines parallel to the straight line connecting the contact points of the pair of pins with which the orientation flat abuts. is necessary. The driving means 10b 'of the pin 10b is fixed to the back surface of the main body 50. The structure of the other parts is the same as the structure of the pin 10a, and the description thereof is omitted.

With the pins 10b and 10a, the wafer 30
Is determined, but at this time, it is necessary to bring the side surface of the wafer 30 into contact with these pins, and therefore, the alignment mechanism 11 is provided. This mechanism 11 includes pins 10a,
The driving means 11 ′, which has a common pin with 10 b, is fixed to the back surface of the main body 50 so as to elastically press the side surface pressing force of the wafer 30 so as not to become larger than a certain value (for example, a spring or a spring). A rubber sheet or the like) is used. This is because the diameter of the wafer 30 is not always constant and variations in dimensions are absorbed.

Wafer 30 transferred to the main surface of main body 50
Prior to this, when receiving the pins 10a, 10
b, the alignment mechanism 11 is connected to each drive means 10a'10.
Driven in the direction away from the center of the wafer 30, that is, in the opening direction by b'and 11 ', and then the pins 10a and 10b.
Is driven to a predetermined position in the closing direction (toward the center of the wafer). Next, the alignment mechanism 11 is driven in the closing direction to move the wafer 3 to the preset desired position.
Fix 0. In this state, the wafer transfer arm 8 moves to the exposure stage 9. When releasing the wafer 30, immediately after the wafer 30 is sucked and fixed, the alignment mechanism 11 is first driven in the opening direction, and then the pin 1 is released.
0a and 10b are driven in the opening direction.

In this way, the alignment can be transferred to the suction-fixing means of the exposure stage 9 with a very small amount of misalignment, and all the fine alignment here is because the wafer is in the search area. Automatic adjustment is possible.

For the wafer 1 taken out of the wafer carrier 3, the position of the orientation flat 2 is confirmed at the wafer transfer section 5. At this time, if the orientation flat detector 6 cannot detect the rotation, the rotation angle is corrected by rotating the wafer chuck 7 that adsorbs the upper main surface of the wafer 20 and stopping the rotation at the position detected by the detector 6. Next, the wafer chuck 7 moves to the wafer transfer position and waits for the wafer transfer arm 8. The wafer transfer arm 8 moves to the wafer transfer position and is located below the wafer 20. Then, the wafer chuck 7 is lowered and the wafer 20 is transferred onto the wafer transfer arm 8. Positioning pins 10b, 10
At the time of handing over the wafer, b has a mechanism for retracting from the pre-alignment position to the outside of the wafer as described above.

With reference to FIGS. 3A, 3B and 3C, a procedure for transferring the wafer 30 onto the wafer transfer arm 8 and performing pre-alignment will be described. As shown in FIG. 3A, when the wafer 20 is transferred from the wafer chuck 7 to the wafer transfer arm 8, the positioning pins 10 a and 10 are used.
b and the alignment mechanism 11 are retracted from the pre-alignment position. Next, when the wafer 30 is received, the positioning pins 10a and 10b move to the pre-alignment position as shown in (b). Then, as shown in (c), the alignment mechanism 11 moves the wafer 30 to the positioning pins 10a,
Push to 10b. As a result, the pre-alignment operation is completed, and in that state, the wafer transfer arm 8 moves to the exposure stage 9.

At the exposure stage 9, the reverse operation is performed and the wafer 30 is transferred. At this time, the retracting operation is not performed until the wafer 30 is attracted and fixed by the chuck here. For this reason, there is no risk of positional displacement occurring during delivery at this time.

As described above, in this embodiment, pre-alignment is performed in two stages. The first stage is pre-alignment performed by the orientation flat detector 6, and the second stage is pre-alignment performed by the wafer transfer arm. By performing the alignment in two stages as described above, not only the automatic alignment error does not occur but also the adjustment time in the first stage can be shortened.
This pre-alignment time is shortened by 1.5 to 3.0 seconds during one operation. Moreover, since the second stage pre-alignment can be performed during the transfer of the arm 8, there is an advantage that the loss time is small.

Further, since the wafer transfer arm is pin-fixed, there is an advantage that the displacement of the suction surface due to dirt on the suction surface is small as in the suction fixing.

In this embodiment, the two pins that contact the side surface of the orientation flat of the wafer 30 are shown, but a flat plate having a flat surface that contacts this side surface may be used. Further, although the cylindrical pin is provided in the alignment mechanism 11, it may be a flat plate having a flat contact surface instead of the cylindrical pin.

Although the pins 10a and 10b are aligned by moving them in the direction of the main surface of the wafer 30, the pins 10a and 10b may be vertically moved along the through hole 35 to perform alignment. In this case, the pins 10a,
For 10b, a conical pin having a tapered shape is used instead of a cylindrical shape.

This embodiment describes the case where the wafer in the carrier is transported to the exposure stage, but conversely, it may be used when the wafer which has been exposed is stored in the carrier.

[0038]

As described above, according to the present invention, since the pre-alignment mechanism is provided on the wafer transfer arm to reduce the positional deviation of the wafer that occurs when the wafer is handed over, each of the above objects can be achieved. The variation in the pre-alignment of the wafer is within a range where there is practically no problem, the manual adjustment time by the operator is substantially eliminated, and the productivity of the exposure work is improved.

[Brief description of drawings]

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

2A and 2B are a top view and a side view showing a wafer transfer arm of the exposure apparatus of FIG.

3 (a), (b), and (c) are top views sequentially showing operation states of a wafer transfer arm of the exposure apparatus of FIG.

FIG. 4 is a top view showing a conventional exposure apparatus.

[Explanation of symbols]

 1, 20, 30, 40 Semiconductor wafer 2 Orientation flat (orientation flat) 3 Wafer carrier 4 Wafer transfer part 5 Wafer transfer part (pre-alignment stage) 6 Orientation flat detector 7 Wafer chuck 8 Wafer transfer arm 9 Exposure stage 10a, 10b Positioning pin 11 Positioning Mechanism 12, 13 Motor 11 ', 10a', 10b 'Drive Means 35 Through Hole 50 Main Body

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 21/68 GA H01L 21/30 503 Z

Claims (5)

[Claims] 1. An exposure apparatus comprising: a pre-alignment stage for aligning a semiconductor wafer; and a wafer transport means for transporting the wafer aligned by the stage to an exposure stage. An exposure apparatus comprising an alignment mechanism for aligning the wafer. 2. The exposure apparatus according to claim 1, wherein the alignment mechanism is a mechanism for performing alignment by sandwiching three side surfaces including an orientation flat of the semiconductor wafer. 3. A mechanism for performing the alignment includes a first pin having a flat surface that abuts a side surface of an orientation flat portion of the wafer, and a side surface of the wafer which is on a line passing through a substantially center of the wafer. 3. The exposure apparatus according to claim 2, further comprising: a second pin that comes into contact with the third pin; and a third pin that elastically presses the wafer so that the side surface of the wafer comes into contact with the first and second pins. 4. The exposure apparatus according to claim 1, wherein said wafer transfer means has means for controlling so that said wafer held by said alignment mechanism is released after said wafer is adsorbed on said exposure stage. . 5. The control means controls, when releasing the wafer, the first pin and the second pin to be separated from the side surface of the wafer after the third pin is separated from the side surface of the wafer. The exposure apparatus according to claim 3, further comprising: