JP2002246444A - Method and device for detecting position of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer position detecting method/device for detecting the center position of a wafer, in a state that the influence of an error is less in few measurement positions. SOLUTION: In the method, the disk-like wafer 2, where a notch part 2a is formed is placed on a turn table 4 and a wafer center position 9 is detected. A detection sensor 11 arranged at the peripheral part of the turn table 4 measures the distance from the table center position 8 to a wafer outer peripheral edge 2b at three different measurement positions A, B and C. The wafer center position 9 with respect to the table center position 8 is obtained based on measurement distances x0, y0 and z0. A distance from the table center position 8 to the wafer outer peripheral edge 2b is measure at a detection position D which is different from the measurement positions A, B and C. The detection distance w0 is corrected based on the obtained waver center position 9 and a distance for correction/detection r1 is compared with a radius distance r2 of the wafer 2. Then, it is determined whether the obtained wafer center position 9 is appropriate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer position detecting method and a wafer position detecting device.

[0002]

2. Description of the Related Art Notches,
A disk-shaped wafer having a notch for alignment such as an orientation flat is transferred one by one into a vacuum chamber, and a predetermined reaction process is performed.

When a wafer is transferred into the vacuum chamber, it is necessary to form as many square chips as possible from the disk-shaped wafer or to improve the yield of processing in the vacuum chamber. It must be positioned in the vacuum chamber with the correct position and orientation.

However, in general, when a wafer is transferred to an apparatus, the transfer is rarely performed with high accuracy. For this reason, the position and direction of the wafer are measured in the apparatus, and the deviation is corrected.

Conventionally, as a place where such a mechanism for position correction is provided, another vacuum chamber is provided in the apparatus, and after correcting the position of a wafer in this vacuum chamber, a vacuum chamber for performing a reaction process is provided. Transported inside. Providing another vacuum chamber for positioning as described above is employed because it is advantageous in terms of tact and flexibility of conveyance.

A conventional position detecting device 41 shown in FIG. 5 detects a position of a wafer 42 and a position of a notch 42a placed on a rotary table 44 rotated by a driving motor 43, and thus, costs and system cost are reduced. From the demand for miniaturization,
A one-dimensional optical linear sensor 46 is arranged, and the wafer 42 is placed on the rotating table 44 and rotated, so that the wafer center position 4 with respect to the table center position 48 is adjusted.
9 are detected. 45 is a rotational position detector,
50 is a graph creation unit, 51 is a deviation amount deviation direction calculation unit, 5
Reference numeral 2 denotes a position control unit.

When detecting the deviation amount d,
By measuring the entire circumference of the wafer 42, a graph as shown in FIG. 6 was obtained, and the shift amount d and the shift direction a were obtained.

[0008]

However, according to the above-described position detection method, there is a problem that it takes a long time to perform the measurement in the case of full circumference measurement. In addition, when calculating from a plurality of measurement points, the calculation is performed using a trigonometric function or a complicated equation, so that errors during calculation tend to increase, and the influence of measurement errors tends to increase.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wafer position detecting method and a wafer position detecting device capable of detecting the center position of a wafer at a small number of measurement positions and with a small influence of an error.

[0010]

According to a first aspect of the present invention, there is provided a method for detecting a position of a wafer, comprising the steps of:
This is a method of mounting a disc-shaped wafer having a notch for orientation alignment on a rotary table and detecting the center position of the wafer, wherein different detection sensors are arranged at the periphery of the rotary table. At one of the measurement positions, the distance from the table center position of the rotary table to the outer peripheral edge of the wafer is measured. Based on the three measurement distances obtained by this measurement, the wafer center position with respect to the table center position is determined. Measure the distance from the table center position to the outer peripheral edge of the wafer at a check position different from the measurement position,
The verification distance is corrected based on the calculated wafer center position, and the corrected verification distance is compared with the wafer radial distance to determine whether the calculated wafer center position is an appropriate position. It is a method of judging.

Therefore, according to the position detecting method of the first aspect, the center position of the wafer can be accurately obtained only by measuring the outer peripheral edge of the wafer at four points. A wafer position detecting method according to a second aspect of the present invention is a method of mounting a disc-shaped wafer having a notch for orientation alignment on a rotary table and detecting the center position of the wafer. The distance from the table center position of the rotary table to the outer peripheral edge of the wafer is measured at three different measurement positions by the detection sensors arranged at the peripheral portion of the rotary table, and the three measurements obtained by the measurement are measured. Based on distance,
A shift amount of the wafer center position with respect to the table center position is obtained, and an actual wafer center position is obtained based on the shift amount.
In addition, the distance from the table center position to the outer peripheral edge of the wafer is measured at a check position different from the three measurement positions, and the check distance is corrected based on the obtained wafer center position. Compare whether the difference between the distance and the radial distance of the wafer is smaller than a set value, and if smaller than the set value, determine that the wafer center position obtained by the above measurement is appropriate and exceed the set value. Is a method of shifting the position of the wafer and measuring the center position of the wafer again.

Therefore, in the position detecting method according to the second aspect, similarly to the first aspect, the amount of deviation of the center position of the wafer from the center position of the rotary table can be obtained simply by measuring the outer peripheral edge of the wafer at four points. Can be determined accurately.

Further, the invention according to claim 3 of the present invention provides:
3. The wafer position detecting method according to claim 1, wherein three different measurement positions are set to 0 degree and 90 degrees, respectively.
This is a method in which the position is set to a position between 0 and 180 degrees, and the check position is set to a position between 0 and 180 degrees.

According to a fourth aspect of the present invention, in the method for detecting a wafer according to the second or third aspect, when the deviation amount is obtained, the deviation amount is set to an unknown value, and This is a method of applying the property of a circle that the center of the circle is on a vertical bisector of an arbitrary chord to each measurement distance between the table center position measured at one measurement position and the outer peripheral edge of the wafer.

Therefore, according to the third and fourth aspects of the present invention, since the four measurement positions are set to a relatively narrow range within 180 degrees, the time required for the measurement can be shortened without fail. In addition, since the center of the circle is located on the perpendicular bisector of an arbitrary chord to determine the amount of deviation, the property of the circle is used.
The shift amount can be obtained.

A wafer position detecting device according to a fifth aspect of the present invention detects a wafer center position of a disk-shaped wafer mounted on a rotary table and having a notch for alignment. A detection sensor disposed at the periphery of the rotary table for detecting the outer periphery of the wafer, and a distance calculation unit for receiving a detection signal from the detection sensor and obtaining a distance from the center position of the table to the outer periphery of the wafer When,
A shift amount calculating section for calculating a shift amount between the respective center positions based on the measured distances at the three different measurement positions obtained by the distance calculating section; and a wafer based on the shift amount obtained by the shift amount calculating section. A center position calculating unit for calculating the center position, and correcting the correction distance measured at a verification position different from the three measurement positions on the basis of the obtained shift amount to obtain a corrected verification distance. A determination unit configured to determine whether a difference between the verification distance and the radial distance of the wafer is smaller than a set value.

[0017] The invention according to claim 6 of the present invention provides:
6. The wafer position detecting device according to claim 5, wherein the two different measurement positions are set to 0 degree, 90 degrees, and 180 degrees, respectively, and the check position is set to a position between 0 degrees and 180 degrees. When calculating the shift amount, this shift amount is set to an unknown value, and the center of the circle is perpendicular to an arbitrary chord at each measurement distance between the table center position measured at the above three measurement positions and the wafer outer peripheral edge. This device applies the property of a circle that is on a bisector.

Therefore, claims 5 and 6 above.
Also in the position detecting device described in (1), the center position of the wafer can be accurately obtained with a small number of measuring points and a simple formula, as described in (1) to (4).

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a wafer position detecting apparatus and method according to an embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG.

The wafer position detecting apparatus 1 according to the present embodiment is, for example, a semiconductor wafer manufacturing apparatus having a disc-shaped wafer 2 in which a notch 2a for alignment is formed on a predetermined outer periphery.
Is provided in a vacuum chamber for performing a predetermined reaction process.

As shown in FIGS. 1 and 2, the position detecting device 1 is arranged along a radial direction from a table center position 8 of a rotary table 4 rotated by a drive motor 3, and is mounted on the rotary table 4. A detection sensor (for example, an optical linear sensor is used) 11 for detecting the outer peripheral edge 2b of the wafer 2 placed on the surface of the wafer 2, a detection signal 31 detected by the detection sensor 11, and a rotation position detector for the rotary table 4 5 and a plurality of predetermined positions (for example, indicated by A, B, C, and D).
, A distance calculation unit 12 for obtaining a distance (for example, indicated by x0, y0, z0, w0) from the table center position 8 to the wafer outer peripheral edge 2b, and three different measurement positions A obtained by the distance calculation unit 12. , B, C measurement distance x0, y
Based on 0 and z0, a shift amount calculating unit 13 for calculating a shift amount d between the center positions 8 and 9 of each other, and a center of the wafer 2 is calculated by a predetermined arithmetic expression based on the shift amount d obtained by the shift amount calculating unit 13. And a center position calculating unit 14 for obtaining coordinates (wafer center position) of the position 9 in the table coordinate system.

When the distance to the table center position 8 is determined by the detection sensor 11, if the measured position is in the notch 2a, the wrong center position is determined. To prevent this, a determination unit 15 is provided.

That is, the determination unit 15 determines whether
Different from the three measurement positions A, B, and C, for example, a measurement distance signal 33 (determined by the distance calculation unit 12) at a check position D intermediate between A and B, and the wafer center determined by the center position calculation unit 14. At the same time, the wafer center position signal 34 at the position 9 is input, and the verification distance w0 obtained at the verification position D is corrected by the shift amount d of the wafer center position 9 obtained by the calculation. Distance and 3
It is configured to compare the radius distance of the wafer 2 obtained from the three measurement positions A, B, and C and determine whether the difference is smaller than a set value (small value).

If it is determined that the value is smaller than the set value, the position correction signal 35 of the wafer center position 9 calculated by the calculation is transmitted to the position controller 16 for controlling the position of the wafer 2, for example. And alignment is performed so that the wafer center position 9 is at a predetermined position.

On the other hand, if the set value is exceeded, it is determined that one of the measurement positions A, B, and C is located at the notch 2a, and the position control unit 16 sends the drive motor 3 of the rotary table 4 An instruction signal 36 for slightly shifting the position of the wafer 2 is output, and the operation of detecting the wafer center position 9 is performed again. Of course, the amount of rotation of the wafer 2 is
Since the angle is set such that the notch 2a can be reliably avoided, only one detection operation is required.

Here, the detection operation of the wafer center position 9 will be described.
A specific description will be given based on FIG. 2 and FIG. When the wafer 2 is placed on the turntable 4, the detection sensor 11 in this state detects the table center position 8 of the turntable 4 at the first measurement position A (for example, the 0-degree position in FIG. 2) of the wafer outer peripheral edge 2b. , A distance x0 from the table center position 8 to the wafer outer peripheral edge 2b is measured at a check position D (α-degree position in FIG. 2) rotated by α degrees. The second rotated by β-α degrees
At the measurement position B (the β-degree position in FIG. 2), the table center position 8
Is measured from the table center position 8 to the wafer outer peripheral edge 2b at a third measurement position C (γ-degree position in FIG. 2) further rotated by γ-β degrees.
The distance z0 to b is measured.

The first, second and third measurement positions A,
Using the measured distances x0, y0, and z0 at B and C, the shift amount d between the table center position 8 and the wafer center position 9 is obtained as follows.

First, two of the three measurement positions A, B and C are measured.
From two combinations of points, two perpendicular bisectors between each measurement position are obtained. For example, a vertical bisector 17 is obtained from the first measurement position A and the second measurement position B, and a vertical bisector 18 is obtained from the second measurement position B and the third measurement position C. Then, since these intersections become the wafer center position 9, the displacement d of the wafer center position 9 can be obtained by solving the equations representing these two bisectors 17 and 18 as simultaneous equations.

For example, as shown in FIG.
Consider the case where C is 0 degree, 90 degrees, and 180 degrees. Here, the perpendicular bisector 19 at the measurement positions C and A in FIG.

[0030]

(Equation 1) Therefore, the shift amount dx in the x direction of the wafer center position 9 is obtained.

The vertical bisector 20 of the measurement positions A and B
Is

[0032]

(Equation 2) Substituting equation (1) into

[0033]

(Equation 3) The displacement dy in the y direction of the wafer center position 9 is obtained.

Next, the verification operation will be described. This check is performed by correcting the check distance w0 at the wafer center position 9 obtained above and correcting the corrected check distance r1 obtained at the wafer center position 9 and the measurement position A, B or C at the wafer center position 9. This is performed by comparing the calculated wafer radius distance r2. That is, it is checked whether or not the following equation (4) holds for a sufficiently small value of k.

[0035]

(Equation 4) If the above equation (4) is satisfied, it is determined that the wafer center position 9 obtained by the calculation is at an appropriate position. If not, any of the measurement positions A, B, and C or the verification position D is determined. Is located in the notch 2a, it is determined that the correct wafer center position 9 has not been determined. If it is determined that the wafer is not at the correct wafer center position 9, a little
The detection operation of the wafer center position 9 is performed again at the position where is rotated (shifted position).

Of course, the wafer 2 is provided with only one notch 2a. Therefore, by appropriately shifting the next measurement position, the measurement position can be set at a position that always deviates from the notch 2a. can do.

As described above, the wafer center position 9 can be accurately obtained by performing at most two detection operations. Incidentally, when the wafer 2 is transferred, usually, the alignment has already been performed to some extent when the wafer 2 comes out of the device in the preceding process, so the amount of deviation in the direction of the notch 2a is not so large. Mostly, the angle is within 10 degrees.

For this reason, if the detection sensor 11 is arranged so that the measurement is started from a direction without the notch 2a, for example, from the side opposite to the notch 2a, an accurate detection operation can be performed by one detection operation. The wafer center position 9 can be obtained.

Here, a schematic configuration of a semiconductor manufacturing apparatus using the wafer position detecting device 1 will be described with reference to FIG. As shown in FIG. 4, in this semiconductor manufacturing apparatus, the wafer 2 is first loaded into the load lock chamber 21,
After being evacuated here, it is sent to the position detection chamber 24 via the transfer chamber 23 by the transfer arm 22. In the position detection chamber 24, the detection of the center position of the wafer 2, that is, the position shift is measured based on the above-described position detection device and position detection method. Thereafter, the wafer 2 is moved in a direction opposite to the detected misalignment direction, the center of the wafer 2 is adjusted to a predetermined position, and the direction of the notch 2a is further adjusted to the predetermined direction. Thereafter, the wafer 2 is taken out by the transfer arm 22 and transferred to the process chamber 25 via the transfer chamber 23.

As described above, in the embodiment of the present invention, three measurement positions A and
In B and C, the outer peripheral edge 2 of the wafer 2 is shifted from the table center position 8.
b, and using the three measured distances x0, y0, and z0, and utilizing the property that the intersection of the vertical bisector of the chord is the center of the circle, the table center position 8
Of the wafer center position 9 with respect to
0, it is determined whether or not the obtained wafer center position 9 is appropriate. Therefore, an accurate wafer center position 9 can be obtained with a small number of measurements, and the intermediate position is not used because a complicated calculation is not used. Calculation errors are less likely to occur, and the effects of measurement errors are small.

In the above embodiment, when describing the configuration of the apparatus, it has been described that the apparatus includes a calculation section, an operation section, a judgment section, and the like. However, these sections are described focusing on functions. Yes, in an actual configuration, each function is integrated into the processor as needed.

Further, in the above embodiment, the detection sensor 11 has been described as being arranged along the radial direction of the turntable 4, but it is needless to say that the outer peripheral portion of the wafer 2 can be detected without being along the radial direction. Then, any arrangement may be used.

[0043]

According to the method and apparatus for detecting the position of a wafer according to the present invention, three points on the outer peripheral edge of the wafer are measured to determine the distances to the center of the rotary table, respectively. By using and to determine the actual wafer center position with respect to the table center position, and comparing the calculated distance measured at the verification position with the calculated center position and the distance between the measurement point, Since it is determined whether or not the obtained wafer center position is appropriate, the wafer center position can be accurately obtained only by measuring the outer peripheral edge of the wafer at four points. That is, as compared with the conventional position detection method, the influence of the measurement error is reduced and the number of measurements can be reduced, so that high-accuracy measurement can be performed in a short time, which leads to speedup of semiconductor manufacturing. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a wafer position detecting device according to an embodiment of the present invention.

FIG. 2 is a plan view of the wafer for describing an operation of detecting a center position of the wafer in the embodiment.

FIG. 3 is a plan view of the wafer for describing an operation of detecting the center position of the wafer in the embodiment.

FIG. 4 is a plan view showing a schematic configuration of a semiconductor manufacturing apparatus to which the wafer position detecting device of the embodiment is applied.

FIG. 5 is a schematic perspective view illustrating a conventional wafer position detection method.

FIG. 6 shows a shift amount and a shift amount in a conventional wafer position detection method.
It is a graph for obtaining a direction.

[Explanation of symbols]

 Reference Signs List 1 Wafer position detecting device 2 Wafer 2a Notch 2b Wafer outer peripheral edge 3 Drive motor 4 Rotary table 5 Rotary position detector 8 Table center position 9 Wafer center position 11 Detection sensor 12 Distance calculator 13 Shift amount calculator 14 Center position calculation Unit 15 Judgment unit 16 Position control unit 17 Vertical bisector 18 Vertical bisector 19 Vertical bisector 20 Vertical bisector A First measurement position B Second measurement position C Third measurement position D Calculation position x0 measurement distance y0 measurement distance z0 measurement distance w0 verification distance d shift amount dx x direction shift amount dy y direction shift amount r1 correction calculation distance r2 wafer radius distance

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA07 AA12 AA17 AA26 BB03 CC19 DD06 FF01 FF04 JJ02 JJ09 JJ25 MM04 PP13 UU05 5F031 CA02 GA44 JA28 JA29 JA34 JA35 KA11

Claims (6)

[Claims] 1. A method for placing a disc-shaped wafer having a notch for orientation alignment on a rotary table and detecting the center position of the wafer, wherein the detection is provided at a peripheral portion of the rotary table. The sensor measures the distance from the center position of the rotary table to the outer periphery of the wafer at three different measurement positions.
The wafer center position with respect to the table center position is obtained based on the three measurement distances, and the distance from the table center position to the outer peripheral edge of the wafer is measured at a check position different from the three measurement positions. The correction is performed based on the obtained wafer center position, and the correction check distance is compared with the radial distance of the wafer to determine whether the obtained wafer center position is an appropriate position. Of detecting the position of a wafer to be processed. 2. A method for mounting a disc-shaped wafer having a notch for orientation alignment on a rotary table and detecting the center position of the wafer, wherein the detection is provided at a peripheral portion of the rotary table. The sensor measures the distance from the center position of the rotary table to the outer periphery of the wafer at three different measurement positions.
The amount of deviation of the wafer center position with respect to the table center position is determined based on the three measurement distances, the actual wafer center position is determined based on this deviation amount, and the wafer is shifted from the table center position at a check position different from the three measurement positions. The distance to the outer peripheral edge is measured, this correction distance is corrected based on the obtained wafer center position, and it is determined whether or not the difference between the corrected correction distance and the radial distance of the wafer is smaller than a set value. In comparison, if it is smaller than the set value, it is determined that the wafer center position obtained by the above measurement is appropriate, and if it exceeds the set value, the position of the wafer is shifted and the wafer center position is measured again. A wafer position detecting method. 3. Each of three different measurement positions is set to 0 degree,
90 ° and 180 °, and the check position is 0
3. The method according to claim 1, wherein the position is between 180 degrees and 180 degrees. 4. When calculating the shift amount, the shift amount is set to an unknown value, and the center of the circle is arbitrary at each measurement distance between the table center position measured at three measurement positions and the outer peripheral edge of the wafer. 4. The method according to claim 2, wherein a characteristic of a circle that is located on a vertical bisector of the chord is applied. 5. An apparatus for detecting a center position of a wafer of a disc-shaped wafer mounted on a rotary table and having a notch for alignment, and disposed at a peripheral portion of the rotary table and outside the wafer. A detection sensor for detecting the periphery, a distance calculation unit for inputting a detection signal from the detection sensor to calculate the distance from the center position of the table to the outer periphery of the wafer, and three different measurement positions obtained by the distance calculation unit A shift amount calculating unit for calculating a shift amount between the respective center positions based on the measurement distance in the above, a center position calculating unit for obtaining a wafer center position based on the shift amount obtained by the shift amount calculating unit;
The correction distance measured at a verification position different from the two measurement positions is corrected based on the deviation amount obtained above to obtain a corrected correction distance, and the difference between the corrected correction distance and the radial distance of the wafer is calculated. A determination unit for determining whether the value is smaller than a set value. 6. Each of two different measurement positions is set to 0 degree,
90 ° and 180 °, and the check position is 0
When the position is between 180 degrees and 180 degrees, and the amount of deviation is obtained, the amount of deviation is set to an unknown value, and each measurement between the center position of the table measured at the three measurement positions and the outer peripheral edge of the wafer is performed. 6. The wafer position detecting apparatus according to claim 5, wherein a property of the circle that the center of the circle is on a vertical bisector of an arbitrary chord is applied to the distance.