JP2000208590A - Method and apparatus for detecting position of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of detecting the position of a wafer, which enables the center of the wafer to be detected with few measuring points. SOLUTION: In a method of detecting the position of a wafer, when the circular wafer 2 having a notch 2a for orientation is placed on a rotary table to detect the center 32 of the wafer, a detector sensor measures distances x0, y0, and z0 from the center 31 of the table to points A, B, and C on the periphery of the wafer, respectively, wherein the measuring points A and B form an angle of 90 deg. and the proving point C is at the midpoint between the points A and B. By applying the second cosine theorem using the two measured distances x0 and y0 and a radius r of the wafer to determine an amount d of deviation of the center 32 from the center 31, which allows the real center 32 of the wafer to be determined, the distance z0 for proving is adjusted by means of the determined center of the wafer. This method determines whether or not the determined center of the wafer is correct, depending on whether or not the difference between the amended distance for proving and the radius r of the wafer is smaller than set value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method and an apparatus for detecting a position of a wafer.

[0002]

2. Description of the Related Art Notches,
Disc-shaped wafers having notches for orientation alignment, such as an orientation flat, are transported one by one into a vacuum chamber and subjected to a predetermined reaction process.

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.

When detecting the position of the wafer and the position of the notch, as shown in FIG. 5, due to the cost and the demand for miniaturization of the system, the one-dimensional optical linear sensor 6 is required.
1, and the amount of displacement d of the wafer 51 is detected by mounting and rotating the wafer 51 on the turntable 62.

When detecting the amount of deviation, the wafer 51 is not perfectly circular but has a notch 51a.
By measuring four or more positions on the outer periphery of the wafer 51,
The center position of the wafer 51 has been determined.

[0009]

According to the position detecting method described above, the wafer is rotated by a half turn (180 degrees) or more in order to improve the position detecting accuracy, and the rotation for measurement is performed for each measuring position. There is a problem that the time required for the measurement is increased by stopping more than four times.

Accordingly, an object of the present invention is to provide a wafer position detection method and a position detection device capable of detecting the center position of a wafer at a small number of measurement positions.

[0011]

In order to solve the above-mentioned problems, a wafer position detecting method according to the present invention is directed to a method of rotating a disk-shaped wafer having a notch, an orientation flat or the like formed with a notch for alignment. A method of detecting the center position of the rotary table by detecting the distance from the center position of the rotary table to the outer peripheral edge of the wafer at two different measurement positions by a detection sensor arranged at the peripheral edge of the rotary table. Is measured, and the center position of the wafer with respect to the center position of the rotary table is obtained based on the two measurement distances obtained by the measurement and the known radial distance of the wafer, and at a verification position different from the two measurement positions. Measure the distance from the center position of the turntable to the outer peripheral edge of the wafer, and correct this correction distance based on the calculated center position of the wafer. Alms, by comparing the radial distance of the modified verification for distance and the wafer, a method of determining whether the center position of the wafer obtained is a proper position.

Also, the wafer position detecting device of the present invention is
A device for detecting the center position of a disk-shaped wafer having a notch placed on a rotary table, a notch for orientation alignment such as an orientation flat, and the like, which is arranged at a peripheral portion of the rotary table and has a A detection sensor for detecting the outer peripheral edge, a distance calculation unit for inputting a detection signal from the detection sensor to obtain a distance from the center position of the rotary table to the outer peripheral edge of the wafer, and a different calculation unit for calculating the distance. A shift amount calculating unit for calculating a shift amount between the center positions of the wafers based on the measured distance at the two measurement positions and the known radial distance of the wafer; and a center of the wafer based on the shift amount obtained by the shift amount calculating unit. A center position calculating unit for calculating a position; and a correction distance, which is corrected based on the determined shift amount, to a verification distance measured at a verification position different from the two measurement positions. Together determine the release is obtained by including a determination unit for determining whether the difference between the radial distance of the modified verification for distance and the wafer is smaller than the set value.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a disk-shaped wafer having notches for orientation alignment, such as a notch and an orientation flat, is placed on a rotary table, and the center of the wafer is placed. In this method, a distance between a center position of a rotary table and an outer peripheral edge of a wafer is measured at two different measurement positions by a detection sensor disposed at a peripheral portion of the rotary table. The actual center position of the wafer with respect to the center position of the rotary table is obtained based on the two measured distances and the known radius distance of the wafer, and the calculated center position of the rotary table is different from the two measurement positions. The distance to the outer peripheral edge of the wafer is measured, and the correction distance is corrected based on the calculated center position of the wafer. By comparing the radial distance of the wafer, a position detection method of the wafer to determine whether the center position of the wafer obtained is a proper position.

According to this position detecting method, the center position of the wafer can be accurately obtained only by measuring the outer peripheral edge of the wafer at three points.

The invention according to claim 2 of the present invention provides:
This is a method of placing a disc-shaped wafer having a notch for orientation alignment such as a notch and an orientation flat on a rotary table and detecting the center position of the wafer, and detecting the center position of the wafer at the periphery of the rotary table. A sensor measures the distance from the center position of the rotary table to the outer peripheral edge of the wafer at two different measurement positions, and based on the two measured distances obtained by this measurement and the known radial distance of the wafer, Of the center position of the wafer with respect to the center position of the wafer, the actual center position of the wafer is calculated based on this shift amount, and the outer peripheral edge of the wafer from the center position of the rotary table at a check position different from the two measurement positions. Is measured, and the correction distance is corrected based on the calculated center position of the wafer. Compare whether the difference with the radius distance of Eha is smaller than the set value, if smaller than the set value, judge that the center position of the wafer obtained by the above measurement is appropriate, and if it exceeds the set value, Is a wafer position detection method in which the position of the wafer is shifted and the center position of the wafer is detected again.

In this position detecting method, similarly to the first aspect, the deviation of the center position of the wafer from the center position of the rotary table can be accurately obtained only by measuring the outer peripheral edge of the wafer at three points. .

[0017] The invention according to claim 3 of the present invention provides:
A method according to claim 1 or 2, wherein the two different measurement positions are set to positions separated by 90 degrees from each other, and the check position is set to an intermediate position between these two measurement positions.

Further, the invention according to claim 4 of the present invention provides:
In the wafer detecting method according to claim 2 or 3, when calculating the shift amount, the shift amount is set to an unknown value, and the difference between the center position of the rotary table measured at two measurement positions and the outer peripheral edge of the wafer is determined. This is a method of applying the cosine theorem to each of the measured distances and the radial distance of the wafer.

According to the third and fourth aspects of the present invention, since the three measurement positions are within a relatively narrow range of 90 degrees or less, the time required for the measurement can be reliably shortened, and the displacement can be reduced. Since the cosine theorem is used to determine the amount, the amount of displacement can be determined by a simple formula.

Further, the invention according to claim 5 of the present invention detects the center position of a disc-shaped wafer having a notch, orientation flat, or other notch for orientation adjustment formed on a rotary table. Device for performing
A detection sensor disposed at the periphery of the turntable to detect the outer periphery of the wafer; and a distance calculation unit that receives a detection signal from the detection sensor and obtains a distance from the center position of the turntable to the outer periphery of the wafer. A shift amount calculating unit for calculating a shift amount between the center positions of the wafers based on the measured distances at the two different measurement positions obtained by the distance calculating unit and a known radial distance of the wafer; And a center position calculating unit for calculating the center position of the wafer based on the deviation amount obtained in step (a), and correcting the verification distance measured at a verification position different from the two measurement positions based on the deviation amount obtained. And a determining unit for determining whether a difference between the corrected verification distance and the radial distance of the wafer is smaller than a set value.

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 positions separated from each other by 90 degrees, and the check position is set to an intermediate position between these two measurement positions.
When calculating the shift amount, the shift amount is set to an unknown number, and the cosine theorem is used for each measurement distance between the center position of the rotary table and the outer peripheral edge of the wafer measured at the two measurement positions and the radial distance of the wafer. Is applied.

Also in the position detecting device according to the fifth and sixth aspects, as described in the first to fourth aspects, the center position of the wafer can be accurately determined by using a small number of measurement points and a simple formula. Can be sought.

Hereinafter, a wafer position detecting apparatus and position detecting method according to an embodiment of the present invention will be described with reference to FIGS.

The wafer position detecting apparatus 1 according to the present embodiment is, for example, a notch or an orientation flat notch (notch is shown in the drawing) 2a on a predetermined outer periphery in a semiconductor manufacturing apparatus, for example. Is provided in a vacuum chamber for performing a predetermined reaction process on the disc-shaped wafer 2 on which is formed.

As shown in FIGS. 1 and 2, the position detecting device 1 is arranged along a radial direction from a center position 31 of the turntable 4 rotated by the drive motor 3, and is mounted on the turntable 4. A detection sensor (for example, an optical linear sensor is used) 11 for detecting the outer peripheral edge of the placed wafer 2, a detection signal detected by the detection sensor 11, and a detection signal from the rotation position detector 5 of the turntable 3. A rotation position signal is input and a distance (for example, from the center position 31 of the rotary table 4 to the outer peripheral edge of the wafer 2 at a plurality of predetermined positions (for example, indicated by A, B, and C)).
x ₀ , y ₀ , z ₀ );
A shift amount calculating unit 13 for inputting the measured distance obtained by the distance calculating unit 12 and obtaining a shift amount d between the center position 32 of the wafer 2 and the table center position 31 based on a predetermined calculation formula; And a center position calculating unit 14 for obtaining the wafer center position 32 from the shift amount obtained by the unit 13.

By the way, when the distance to the table center position 31 is determined by the detection sensor 11, if the measured position is in the notch 2a, an incorrect center position is determined. To prevent this, a determination unit 15 is provided.

That is, the determination unit 15 determines whether
Different from the two measurement positions A and B, for example, the measurement distance (determined by the distance calculation unit) at the intermediate verification position C and the wafer center position 32 determined by the center position calculation unit 14
And the correction distance obtained at this verification position is corrected using the deviation amount of the wafer center position 32 obtained by the calculation, and the corrected verification distance and the known wafer radius distance are calculated. By comparing, it is configured to determine whether the difference is smaller than a set value (small value). If it is determined that the center position of the wafer 2 is smaller than the set value, the center position of the wafer obtained by the calculation is output to, for example, the control unit 16 for controlling the position of the wafer. Are positioned so that the position is at a predetermined position.

On the other hand, if the set value is exceeded, it is determined that any of the measurement positions is located at the notch 2a, and an instruction to slightly shift the position of the wafer to the drive motor 3 of the turntable 4 is output. At the same time, the operation of detecting the center position of the wafer 2 is repeated. Of course, wafer 2
Is set to such an angle that the notch 2a can be reliably avoided, so that only one detection operation is required.

Here, the operation of detecting the wafer center position 32 will be specifically described with reference to FIGS.

When the wafer 2 is placed on the turntable 4, the detection sensor 11 detects the position of the turntable 4 at the first measurement position A (for example, the 0-degree position in FIG. 2) on the outer peripheral edge of the wafer 2 in that state. A distance x ₀ from the center position 31 to the outer peripheral edge is detected, and then at a check position C rotated by 45 degrees,
The distance z ₀ from the table center position 31 to the outer periphery is measured, and the distance y ₀ from the table center position 31 to the outer periphery at the second measurement position B (the 90-degree position in FIG. 2) further rotated by 45 degrees. Measured.

Using the measured distances x ₀ and y ₀ at the first and second measurement positions, the shift amount d between the table center position 31 and the wafer center position 32 is obtained as follows.

First, when the cosine theorem is applied to the triangle AOP and the triangle BOP, the following equations (1) and (2) are obtained. In the following equation, α indicates an angle between a straight line connecting the table center position 31 and the wafer center position 32 and the straight line OA, and r indicates a known radial distance of the wafer.

[0033]

(Equation 1) By substituting the above equations (1) and (2) into the basic formula of the trigonometric function (sin ² α + cos ² α = 1) and eliminating α, the following equation (3) is obtained.

[0034]

(Equation 2) When the solution of the above equation (3) is obtained for d, and the unnecessary solution is discarded, the solution shown in the following equation (4) is obtained.

[0035]

(Equation 3) By multiplying the above solution d by sinα and cosα respectively,
X of wafer center position 32 with respect to table center position 31
Shift amount d _x in and y directions, d _y is determined as shown in the following equation (5) and (6).

[0036]

(Equation 4) Next, the verification operation will be described.

This check is performed by comparing the corrected check distance obtained by correcting the check distance at the wafer center position obtained above with the radial distance r of the wafer 2.

That is, it is checked whether or not the following equation (7) holds for a sufficiently small value of k.

[0039]

(Equation 5) If the above equation (7) is satisfied, it is determined that the center position of the wafer obtained by the calculation is at an appropriate position. If not, one of the measurement positions is located in the notch. It is determined that the correct center position is not required. If it is determined that the center position is not correct, the operation of detecting the center position of the wafer is performed again at a position where the wafer is slightly rotated (shifted position).

Of course, since only one notch is provided in the wafer, the next measurement position can be set at a position that is always off the notch by appropriately shifting the next measurement position. it can.

As described above, the center position of the wafer can be accurately obtained by performing at most two detection operations.

Incidentally, when the wafer is transferred, usually the alignment has already been performed to some extent when the wafer comes out of the apparatus in the preceding process, so that the amount of deviation in the direction of the notch is not so large. , Almost at an angle within a few tens of degrees.

For this reason, if the detection sensor is arranged so as to start the measurement from the direction without the notch, for example, from the side opposite to the notch, the center of the wafer can be accurately detected by one detection operation. The position can be determined.

Here, a schematic configuration of a semiconductor manufacturing apparatus using the above-described wafer position detecting device 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, where it is evacuated and then moved by the transfer arm 22 via the transfer chamber 23. It is sent to the detection chamber 24. In the position detection chamber 24, the detection of the center position of the wafer, that is, the displacement is measured based on the above-described position detection device and position detection method. Thereafter, the wafer is moved in the direction opposite to the detected misalignment direction, the center of the wafer is aligned with a predetermined position, and the direction of the notch 2a is aligned with 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, the distance from the center of the rotary table to the outer peripheral edge of the wafer is measured at two measurement positions where there is almost no notch, and the two measurement distances are measured. And the known radial distance of the wafer, and applying the cosine theorem and the basic formula of the trigonometric function, to determine the shift amount of the wafer center position with respect to the table center position, and obtain the actual wafer center position from the shift amount. In addition, since it is determined whether or not the obtained center position of the wafer is appropriate based on the calculation distance, an accurate center position of the wafer can be obtained with a small number of measurements.

In the above embodiment, when describing the configuration of the apparatus, it has been described that the apparatus includes a calculation unit, a calculation unit, a determination unit, and the like. Yes, in an actual configuration, each function is integrated into the processor as needed.

In the above embodiment, the detection sensor is described as being arranged along the radial direction of the rotary table. Of course, if the outer peripheral portion of the wafer can be detected without being along the radial direction, any other sensor can be used. Such an arrangement may be used.

[0049]

According to the wafer position detecting method and the position detecting apparatus of the present invention, two points on the outer peripheral edge of the wafer are measured to determine the distances to the center position of the rotary table, respectively. Using the known radial distance of the wafer, the actual center position of the wafer is determined from the amount of deviation between the center position of the rotary table and the center position of the wafer, and the verification distance measured at the verification position is known. Since it is determined whether or not the obtained center position of the wafer is appropriate using the radius distance of the wafer, the center position of the wafer can be determined simply by measuring the outer peripheral edge of the wafer at three points. Can be determined accurately. In other words, the number of measurements is smaller than that of the conventional position detection method, so that the measurement time can be shortened, which leads to the 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 an enlarged view of a central portion of the wafer of FIG. 2;

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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wafer position detecting device 2 Wafer 2a Notch 4 Rotary table 11 Detection sensor 12 Distance calculator 13 Center position calculator 14 Shift amount calculator 31 Table center position 32 Wafer center position

Claims (6)

[Claims] 1. A method for mounting a disc-shaped wafer having notches for orientation alignment, such as a notch and an orientation flat, on a rotary table and detecting the center position of the wafer, comprising the steps of: The distance from the center position of the rotary table to the outer peripheral edge of the wafer is measured at two different measurement positions by the detection sensor
The center position of the wafer with respect to the center position of the rotary table is determined based on the two measured distances obtained by this measurement and the known radial distance of the wafer, and the center of the rotary table at a check position different from the two measurement positions is determined. The distance from the position to the outer peripheral edge of the wafer is measured, this correction distance is corrected based on the obtained center position of the wafer, and the corrected correction distance is compared with the radial distance of the wafer. Determining whether the center position of the obtained wafer is an appropriate position. 2. A method for mounting a disc-shaped wafer having notches for orientation alignment, such as a notch and an orientation flat, on a rotary table and detecting a center position of the wafer, comprising: The distance from the center position of the rotary table to the outer peripheral edge of the wafer is measured at two different measurement positions by the detection sensor
Based on the two measured distances obtained by this measurement and the known radial distance of the wafer, a shift amount of the center position of the wafer with respect to the center position of the rotary table is obtained, and based on the shift amount, an actual center position of the wafer is obtained. And measuring the distance from the center position of the rotary table to the outer peripheral edge of the wafer at a check position different from the two measurement positions, and correcting the check distance based on the obtained center position of the wafer, Comparing whether the difference between the correction check distance and the radius distance of the wafer is smaller than a set value, and if smaller than the set value, it is determined that the center position of the wafer obtained by the above measurement is appropriate, A method for detecting the position of a wafer, comprising: shifting the position of the wafer if the set value is exceeded, and measuring the center position of the wafer again. 3. The wafer position detection according to claim 1, wherein the two different measurement positions are separated from each other by 90 degrees, and the check position is set to an intermediate position between the two measurement positions. Method. 4. The method according to claim 1, wherein when determining the amount of deviation, the amount of deviation is set to an unknown value, and each measured distance between the center position of the rotary table measured at two measurement positions and the outer peripheral edge of the wafer and the radial distance of the wafer. The method according to claim 2 or 3, wherein the cosine theorem is applied to: 5. A device for detecting a center position of a disk-shaped wafer having notches, orientation flats, and other notches for orientation adjustment formed on a rotary table, wherein the center position of the disk-shaped wafer is located at a peripheral edge of the rotary table. A detection sensor disposed to detect an outer peripheral edge of the wafer, a distance calculation unit that receives a detection signal from the detection sensor and obtains a distance from the center position of the rotary table to the outer peripheral edge of the wafer, and a distance calculation unit. Calculation unit for calculating the amount of deviation between the center positions of the wafers based on the measurement distances at the two different measurement positions and the known radial distance of the wafer, and the amount of deviation calculated by the deviation amount calculation unit A center position calculating unit for obtaining the center position of the wafer based on the above, and correcting the distance for verification measured at a verification position different from the two measurement positions based on the obtained deviation amount. With obtaining the correction verification for the distance,
A determination unit configured to determine whether a difference between the correction check distance and the radial distance of the wafer is smaller than a set value. 6. The method according to claim 1, wherein the two different measurement positions are separated from each other by 90 degrees, and the check position is defined as an intermediate position between the two measurement positions. The cosine theorem is applied to each measurement distance between the rotary table center position measured at the two measurement positions and the outer peripheral edge of the wafer and the radial distance of the wafer. Position detection device.