JPH0529441A - Detection of wafer position and orientation flat direction - Google Patents

Abstract

PURPOSE:To detect a wafer position and an orientation-flat existence direction in a noncontact state and in a short time by a method wherein, by means of information obtained from a wafer detection sensor, the wafer position during a transfer operation and the orientation-flat existence direction are recognized or estimated and a wafer is turned in a scanning direction within a limited range. CONSTITUTION:A wafer 1 is transferred at a definite speed to the side of a wafer chuck 6 by using a transfer arm 2. A timing signal obtained when the wafer passes sensors 3 to 5 is analyzed and operated inside a control part 11. An orientation-flat direction is detected from the movement locus 14 of the central position 23 of the wafer 1 being transferred. Then, the control of the transfer arm 2 on a transfer-arm movement shaft 15 and the control of a sliding mechanism 10 on a chuck-center movement shaft 16 are executed in parallel. The center of the wafer 1 is aligned with the center of the wafer chuck 6; the wafer is turned coarsely. The orientation-flat direction is detected accurately by using a detection mechanism 8. Thereby, the yield and the throughput of the title method can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer position and orientation flat direction detecting method in a semiconductor manufacturing apparatus.

[0002]

2. Description of the Related Art In semiconductor manufacturing, as a method for detecting an orientation flat of a silicon wafer (hereinafter, simply referred to as "wafer"), a mechanical method, an optical method of tracing the periphery of a wafer, or the like is used. Has been adopted.

FIG. 10 schematically shows an example of a conventional detecting device. In this detection device, the wafer 1 is sandwiched between the chucks 61a and 61b of the centering mechanism 60 having the chucks 61a and 61b to perform centering, and then the wafer 1 is attracted to the wafer chuck 62, and the wafer 1 is held together with the wafer chuck 62. It is rotated by the rotating mechanism 63, and at the time of this rotation, the edge portion of the wafer 1 is detected by the optical orientation flat detecting mechanism 64, and the orientation flat is detected from this.

[0004]

However, in the conventional orientation flat detection method, the wafer 1
When the centering is performed, a method of directly contacting the chucks 61a and 61b of the centering mechanism 60 with the wafer 1 is used. However, when the detecting means is mechanically brought into contact with the wafer 1 as described above, dust is generated due to contact with the periphery of the wafer, which is easily attached to the surface of the wafer 1 to cause defective products, resulting in poor yield. There was a problem to say. Further, in the conventional detection method, the orientation flat position cannot be detected unless the wafer 1 is rotated once or more to detect the orientation flat. Therefore, there is a problem that the detection time is required and the throughput is reduced.

The present invention has been made in view of the above problems, and an object thereof is to provide a wafer position and orientation flat direction detecting method in a semiconductor manufacturing apparatus, which can improve yield and throughput. is there.

[0006]

In order to achieve the above object, a method for detecting a wafer position and orientation flat direction according to the present invention is provided with three or more non-contact type wafer detection sensors on a transfer path through which a wafer is transferred. And a control unit for controlling the movement of the transfer mechanism, the rotation of the wafer chuck, and the movement of the slide mechanism by processing the signal obtained when the wafer being transferred passes the position of the sensor. And a first step of recognizing or predicting a wafer position and an orientation flat direction during the transfer based on the calculation result, and the transfer based on the information obtained in the first step. The stop position of the mechanism and the slide amount of the slide mechanism are controlled to align the center of the wafer with the center of the wafer chuck. Based on the information obtained in the first step, and the third step of performing the coarse rotation of the wafer within a limited range to accurately detect the orientation flat direction near the orientation flat. This is done sequentially.

[0007]

According to this method, it is possible to recognize or predict the wafer position during transportation and the orientation flat existence direction from the information obtained from the wafer detection sensor, and make the direction of the wafer rotation scan within the limited range. Therefore, the wafer position and the orientation flat direction can be detected in a non-contact state in a short time.

[0008]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a conceptual diagram showing an embodiment of a detection apparatus in a semiconductor manufacturing facility to which the wafer position / orientation flat direction detection method according to the present invention is applied. Since the wafer used in this example is the same as the wafer 1 shown in FIG. 10, the same reference numerals are given.

In FIG. 1, this detection apparatus has a transfer arm 2 as a transfer mechanism for transferring the wafer 1 to a detection position at a constant speed V, and three wafer detection sensors (hereinafter simply referred to as "sensors"). 3, 4 and 5, the vacuum chuck type wafer chuck 6, the rotation mechanism 7, the optical orientation flat detection mechanism 8, the motor 9, and the rotation of the motor 9 causes the rotation mechanism 7 to move together with the wafer chuck 6 in FIG. The slide mechanism 10 is configured to move and adjust in the direction of arrow ab, that is, in a direction intersecting the moving direction of the transfer arm 2 at a right angle. Among these, the sensors 3, 4 and 5 are arranged on the transfer path of the wafer 1 transferred by the transfer arm 2 so as to cross the transfer path at a substantially right angle and arranged at substantially equal intervals within the width of the transfer path. It is arranged. Further, each of the sensors 3 to 5 here is of a transmitted light type, a reflected light type, or the like, and detects the wafer 1 in a non-contact state when the wafer 1 is transferred on the transfer path.
Information at this time is input to the control unit (CPU) 11. Further, the control unit 11 includes a motor 12 for reciprocating the transfer arm 2, a motor 9 for reciprocating the slide mechanism 10, and a motor (not shown) in the rotation mechanism 7 for rotating the wafer chuck 6. When,
The optical orientation flat detection mechanism 8 and the like are connected to each other.

The outline of the operation of this detecting apparatus will be described first. As shown in FIG. 2, the wafer 1 is moved by the transfer arm 2 from the position shown by the dotted line to the position shown by the solid line in FIG.
That is, when the wafer 1 is conveyed to the wafer chuck 6 side at a constant speed V, when the wafer 1 passes the sensors 3 to 5, signals are respectively obtained from the sensors 3 to 5. Further, the timing signals obtained from the respective sensors 3 to 5 are analyzed and calculated in the control unit 11, and the orientation flat direction is detected from the movement locus 14 of the central position 23 of the wafer 1 being transferred. Next, control of the transfer arm 2 on the transfer arm moving shaft 15 and control of the slide mechanism 10 on the chuck center moving shaft 16 are performed in parallel to align the center of the wafer 1 with the center of the wafer chuck 6, and The wafer 1 is roughly rotated to the vicinity of the orientation flat based on the orientation flat direction information, and the optical orientation flat detection mechanism 8 accurately detects the orientation flat direction.

FIGS. 3 to 5 show an example of an operation flowchart for the detection process according to the control procedure programmed in the control unit 11, and FIGS. 6 to 9 are shown.
FIG. 4 is a diagram for explaining a center position of wafer 1 and an orientation flat detection method. Therefore, the center position of the wafer 1 and the orientation flat detecting operation will be described in detail with reference to FIGS.
First, according to this detection method, the wafer 1 being transferred is largely
The first step (see FIG. 3) of detecting the center position of the wafer 1 and the orientation flat direction in a non-contact manner with respect to
Based on the information obtained in the first step, the second step of controlling the stop position of the transfer arm 2 and the slide amount of the slide mechanism 10 to align the center of the wafer chuck 6 with the center of the wafer 1 (see FIG. 4). ) And a third step of roughly rotating the wafer 1 on the basis of the information obtained in the first step to detect an accurate orientation flat near the orientation flat, which will be described step by step below. In the flow charts of FIGS. 3 to 5, “orientation flat” refers to the orientation flat, and “chuck” refers to the wafer chuck 6.

(A) In the first stage, the wafer 1 is moved by the transfer arm 2 from the right to the left in FIG. During this transfer, it is detected in step ST1 whether or not the wafer 1 has passed over the three sensors 3, 4, and 5. The detection here is performed as follows. First, in FIG. 6, the wafer 1 shown at the position of t = 0 is before passing through the sensors 3, 4, and 5, and the wafer 1 shown at the position of time t = T is after passing through the sensors 3, 4, 5. Suppose that Then, the time chart obtained from each of the sensors 3, 4 and 5 appears as a waveform as shown in FIG. 7 during the period from the time t = 0 to the time t = T.

Therefore, the signals from the sensors 3, 4, and 5 are replaced on the time chart of FIG.
The time when 5 starts to detect the wafer 1 is t3S, t4S, t5.
S, end time is t3E, t4E, t5E, midpoint time is t3
If C, t4C, and t5C, the relation of the following expression (1) is established. t5C = t4C ≠ t3C (1) Therefore, from this relationship, the wafer 1 at time t = T
, It can be determined that its center has passed at time t4C and the orientation flat has passed over the sensor 3.

Next, the wafer 1 for the central sensor 4
The offset amount LSC (see FIG. 6) of the center of is calculated. Here, in order to simplify the explanation, description will be given using FIG. 8 in which the time t is converted into the movement distance L of the wafer 1 and drawn. Note that the relationship between the time t and the distance L here is the relationship of the following equation.
(2) holds. L = V (t-t4C) (2) Therefore, in FIG. 8, the point corresponding to time t4C is A, the point corresponding to time t4E is B, the distance between points A and B is Lc, and the time is The point C corresponding to t5C, the point D corresponding to time t5E, the distance between the points C and D is LL, and the center of the wafer 1 is O. Further, in FIG. 8, assuming that the distance between points O and A is LSC and the distance between points O and C is LSL, the following equation (3)
The relationship of (5) holds.

[0015]

[Equation 1]

Since the distance between points A and B is LWL, if the following equation (6) is established, the center of the wafer 1 is offset to the right of the sensor 4 by the distance LSC. Become. LSL-LSC = LWL (6) On the other hand, when the following expression (7) is established, it is understood that the offset is to the left. LSL + LSC = LWL (7) From the above, the position of the wafer 1 is detected and the time t = T.
The center position of the wafer 1 at
It can be seen that it is offset by the distance LSC represented by (8). LSC = V {T-[(t4E-t4S) / 2]} (8)

Next, the orientation flat detection will be described. Again, for simplicity,
The time t is converted into the movement distance L of the wafer 1 and the description will be given with reference to FIG. 9 in which only the items related to the orientation flat are shown. Therefore, in FIG. 9, the center of the wafer 1 is O, the leg of the vertical line to the orientation flat is E, the distance between the points O and E is rF, and the angle between the line connecting the points O and E and the scanning line 17 is θ. , The intersection point of the perpendicular from the center O of the wafer 1 to the scanning line 18 of the sensor 3 is G, and the points O and G are
Assuming that the distance between them is LSR, the intersection of the scanning line 18 of the sensor 3 and the orientation flat is F (corresponding to time t3E in FIG. 7), and the distance between points F and G is LR, the distance LR is It is given in (9). LR = V (t3E-t3C) (9) From the above, the point E is (VFcos θ, rFsin θ) and the point F is (L
R, LSR). Here, the equation on the line EF of the orientation flat passing through the points E and F is the slope (-cos
By passing through the point E at θ / sin θ), the following equation (10) is obtained. y = (rF-cosθ · x) / sinθ (10) Further, since the point F passes on the line EF, LSR = (rF-cosθ · LR) / sinθ (11) LSRsinθ + LRcosθ = rF (12) If tan α = LR / LSR (13), the following equations (14) to (16) are established.

[0018]

[Equation 2]

Therefore, since the distance LSR between the points O and G is obtained from the distance LSC at the time of detecting the center position, the angle θ between the line connecting the points O and E and the scanning line 17, that is, the orientation flat position is also obtained. The judgment before and after the orientation flat is made by comparing (t4C-t3C) and (t3E-t4C) in the time chart of FIG.
That is, if (t4C-t3) is smaller than (t3E-t4C), it is determined to be the front side, and conversely, it is determined to be the rear side.

That is, in this first stage, the wafer 1
Is moved by the transfer arm 2 and is detected by the three sensors 3, 4, and 5 during the movement, whether or not the times t3C, t4C, and t5C match is detected in step ST2. Is wafer 1 in step ST3
Position and orientation flat direction detection. On the other hand, at step ST3, times t3C, t4C,
If t5C is the same, the position of the wafer 1 is detected from the data at the times t3C and t5C at both ends in step ST4. If the wafer 1 is not detected by the three sensors 3, 4, 5 in step ST1, the process proceeds from step ST1 to step ST5, and the midpoint times t3C, t4C of the sensors 3, 4 or the sensors 4, 5 are detected. Midpoint time t4C,
It is determined whether or not t5C matches, and if they match, the position of the wafer 1 is detected in step ST6. On the other hand, if it is not detected in step ST5, the process proceeds to step ST7 and the center point t of the sensor 3 (or sensor 5) is reached.
The position of the wafer 1 is predicted from 3C (or t5C). Then, the wafer 1 processed in steps ST3, 4, 6, and 7 is next processed in the second stage.

(B) In the second step, the wafer chuck 6 and the center of the wafer 1 are aligned with each other. Regarding the method of transferring the wafer 1 in the second step, in order to align the center of the wafer 1 with the chuck center moving axis 16 in FIG. 2, the center position 13 of the wafer 1 is transferred to the position obtained by the following equation (17). Drive the arm 2 (step ST8,
9, 10). V {T- (t4E-t4S) / 2} (17) Further, the chuck center moves by the offset LSC of the center of the wafer 1 with respect to the transfer arm moving shaft 15, and the wafer 1 is transferred from the transfer arm 2 to the wafer chuck 6. The grip is replaced (steps ST11, 12, 13). Further, when the wafer chuck 6 is gripped and changed from steps ST11 and ST12, the center of the wafer 1 is aligned with the center of the wafer chuck 6. On the other hand, steps ST1, 5, 7,
After passing through 10, the wafer 1 subjected to control to step ST13 proceeds to step ST14, slides the wafer chuck 6 up to the transfer arm moving shaft 15, and grabs it from the wafer chuck 6 to the transfer arm 2 (step ST15). .. Further, here, the transfer arm 2 that has grabbed the wafer 1 returns to the transfer start position (step ST16), and is transferred again to be processed again from step ST1. On the other hand, steps ST11 and ST12
The wafer 1 processed in step 3 advances to the third stage for further processing. (c) In the third stage, the orientation flats are aligned. In this third step, since the center of wafer 1 is aligned with wafer chuck 6 in steps ST11 and ST12, respectively, the orientation flat direction is obtained from the signal on the outer periphery of wafer 1 as described above. Therefore, the wafer 1 that has passed through step ST11 is roughly rotated in a limited range smaller than one revolution in the orientation flat direction obtained in the first step in order to improve the throughput, and the wafer 1 is roughly rotated, so that the orientation is improved. The flat is detected (steps ST17 and ST18). On the other hand, the wafer 1 that has gone through step ST12 roughly rotates the wafer chuck 6 within a limited range smaller than one rotation within the orientation flat search range at high speed (step ST19), and performs the orientation flat search (step ST19). ST20). If it is confirmed in step ST21 that an orientation flat exists,
This is confirmed in step ST22, and the detection ends.
On the other hand, if it is not confirmed in step ST21, the process returns to step ST19 via step ST23, and further rough rotation is performed within a limited range smaller than one rotation,
This is repeated until the orientation flat is detected, and when the orientation flat is confirmed, the process ends through step ST22.

Therefore, according to this embodiment, the position of the wafer being transferred and the orientation flat existence direction are recognized or predicted from the information obtained from the wafer detection sensors 3, 4, and 5, and the wafer rotation scan is performed by the rotating mechanism 7. Since it is possible to detect the wafer position and the orientation flat direction within a limited range, it is possible to detect the wafer position and the orientation flat direction in a short time.

In the above embodiment, the vacuum chuck type was disclosed as the wafer chuck, but it does not matter if it is not the vacuum chuck type.

[0024]

As described above, according to the wafer position / orientation flat direction detecting method of the present invention, the wafer position and orientation flat existing direction being conveyed are recognized or predicted from the information obtained from the wafer detection sensor. However, since the direction of the wafer rotation scan is performed within the limited range, the wafer position and the orientation flat direction can be detected in a short time. Therefore, comparing this with the conventional method, in the first step, the throughput is the same as in the conventional wafer transfer, and the throughput does not decrease. In the second step, the throughput is increased by sliding the wafer chuck during the wafer transfer. In the third stage, the centering time is shortened as compared with the conventional method, and the direction of the wafer rotation scan is performed within the limited range, so that the through top is significantly improved. Further, as compared with the conventional method, the effect that the configuration can be achieved by adding a simple device such as a wafer detection sensor arithmetic processing microprocessor can be expected.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a detection device to which a wafer position and orientation flat direction detection method according to the present invention is applied.

FIG. 2 is a diagram for explaining a method of aligning the center of the wafer with the center of the wafer chuck of the detection device shown in FIG.

FIG. 3 is a flowchart showing a processing procedure of a first stage in the wafer position and orientation flat direction detection method according to the present invention.

FIG. 4 is a flowchart showing a processing procedure of a second stage in the wafer position / orientation flat direction detection method according to the present invention.

FIG. 5 is a flowchart showing a processing procedure of a third step in the wafer position / orientation flat direction detection method according to the present invention.

6 is an operation state diagram for explaining a locus along which a wafer normally moves with respect to a sensor in the detection unit shown in FIG.

FIG. 7 is a time chart showing a signal change obtained from each sensor when the wafer moves in FIG.

FIG. 8 is a diagram for explaining a wafer center detection method in the wafer position and orientation flat direction detection method according to the present invention.

FIG. 9 is a diagram for explaining the orientation flat detection method in the wafer position and orientation flat direction detection method according to the present invention.

FIG. 10 is a conceptual diagram showing an example of a detection apparatus to which a conventional wafer position / orientation flat direction detection method is applied.

[Explanation of symbols]

1 Wafer 2 Transfer Arm (Transfer Mechanism) 3 Sensor 4 Sensor 5
Sensor 6 Wafer chuck 7 Rotation mechanism 8 Optical orientation flat detection mechanism 10 Slide mechanism 11 Control unit 1
3 Wafer center position 15 Transfer arm moving axis 16 Chuck center moving axis

Claims (1)

Claim: What is claimed is: 1. A wafer position and orientation in an apparatus in which a wafer transferred by a transfer mechanism is attracted to a wafer chuck and rotated, and an orientation flat direction of the wafer is detected by an optical orientation flat detection mechanism. In the flat direction detecting method, a slide mechanism for slidingly moving the wafer chuck with respect to the transfer mechanism, three or more non-contact type wafer detection sensors arranged on the transfer path of the wafer, The control unit includes a control unit that arithmetically processes a signal obtained when the wafer passes the position of the sensor to control the rotation of the transfer mechanism, the slide mechanism, and the wafer chuck, and the control unit performs the calculation. Wafer position during transfer based on the result And the first stage processing for recognizing or predicting the orientation flat direction, and based on the information obtained in this first step, the stop position of the transfer mechanism and the slide amount of the slide mechanism are controlled to set the center of the wafer. Based on the information obtained in the second step of aligning the center of the wafer chuck and the information obtained in the first step, the wafer is roughly rotated within a limited range to accurately detect the orientation flat direction in the vicinity of the orientation flat. A method for detecting a wafer position and orientation flat direction, characterized in that the third-stage processing to be performed is sequentially performed.