JPH01303737A - Positioning device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is applied to semiconductor device manufacturing '1. Regarding positioning devices for circular objects in M or inspection equipment, etc., in particular, it is used to position the wafer's orientation flat, notch, etc., and also to correct the eccentricity of the wafer and position it, or to place the wafer in a predetermined position with high precision in order to transfer it to the next process. This invention relates to a positioning device capable of positioning.

(Prior Art) Various positioning devices have been proposed for positioning a wafer at a predetermined position in a wafer λ exposure transfer process in a semiconductor device manufacturing apparatus.

FIG. 3 is a schematic diagram of a conventional positioning device.

In the figure, 30 is a detection system for detecting the edge of the wafer 37. In the detection system 30, a light beam from a light source 31 is focused by a lens 32, and is made to enter a wafer 37 via a mirror 33. The light beam that has passed through the processing and cutting portions of the wafer 37 is reflected by the mirror 34 and condensed by the lens 35 to the light receiving element 36.
It is receiving light.

Using the output signal from the light receiving element 36, the position of the orientation flat or notch of the wafer 37 is determined by a calculation means (not shown), and the wafer 37 is positioned by a driving means (not shown).

In this device, the wafer 37 is first rotated once by the rotating shaft 38 by the stepping motor 39, the amount of eccentricity of the wafer 37 is detected from the edge detection value at that time, the wafer is moved in the eccentric direction, the amount of eccentricity is corrected, and then the amount of eccentricity is corrected. , wafer 37 as 1
It was rotated to detect the position of the orientation flat or notch, and then transported to the next process. Therefore, the wafer has to be rotated twice in total, and in order to perform an eccentricity correction operation in the middle,
The drawback was that it was time consuming.

(Problems to be Solved by the Invention) The present invention includes two sets of detection systems for detecting the edge of the wafer, which are arranged 180 degrees opposite to the rotational axis of the wafer, and uses output signals from the two detection systems. One rotation of the wafer (usually 180 @ rotations) by performing predetermined calculation processing
more efficiently.

The object of the present invention is to provide a positioning device that detects the amount of eccentricity, the eccentric position, the eccentric direction, and the position a of the orientation flat or notch in mounting the wafer, and can significantly improve the throughput.

(Means for solving the problem) A wafer having an orientation flat or a notch on a part of its outer periphery is rotatably held on a rotating shaft, and two detection systems are installed to detect the amount of displacement of the wafer in the radial direction. A signal indicating the orientation flat or notch is detected using two output signals from the two detection systems when the wafer is rotated by 1/2 when the wafer is placed opposite to the center of rotation of the rotation axis at 180 degrees. means for calculating the position of the orientation flat or notch on the wafer from the rotation angle of the rotation axis when the signal is generated; The method is to position the wafer at a predetermined position based on each calculated value using a means for calculating an eccentric angle and an amount of eccentricity with respect to the rotation axis.

(Example) FIG. 1 is a schematic diagram of one embodiment of the present invention.

In the figure, reference numerals 100 and 101 are detection systems for detecting the edge portion of the wafer 7, each having the same configuration. Reference numeral 8 denotes a rotating shaft, and 8 a a rotating table, which attracts the wafer 7 and is rotated by a stepping motor 9 .

The two detection systems 100 and 101 are arranged to face each other by approximately 180 degrees with respect to the rotation axis 8 of the wafer 7. In the detection system 100, 1 is a light source such as an LED or a semiconductor laser. Reference numeral 2 denotes a condenser lens which allows the light beam from [1] to enter the edge portion on the surface of the sea urchin 8 through the mirror 3. Reference numeral 5 denotes an imaging lens which forms an image of the edge portion of the wafer 7 onto the surface of a detection element 6 such as a linear sensor via a mirror 4.

In this embodiment, the wafer 7 is rotated 180 degrees around the rotation axis 8, and at this time, the edge portion of the wafer 7 is passed through by two detection systems 100 and 101 installed at positions approximately 180 degrees opposite each other around the rotation axis 8. The eccentricity of the wafer 7 and the position δ of the orientation flat or notch are detected by a calculating means (not shown) using the output signals from the two detection elements 6.

FIG. 2 is an explanatory diagram showing calculation results obtained by two detection systems 100 and 101 and calculation processing described later in the present invention.

An example of the calculation method in this embodiment will be shown using FIG.

The detection system detected by the two detection systems 100 and 101 is rotated by the rotation axis 8.
The distances from the center of rotation of the wafer 7 to the center of rotation are a and b respectively, the angle e is the angle above the center of the wafer 7 with respect to the line passing through the center of rotation and connecting the two detection systems Zoo and 101, and the distance from the center of rotation to the center of the rotation of the wafer 7 is e. The distance (eccentricity) is E, and the radius of wafer 7 is R.
Then, the values of a and b are a>b and a −EX CO3θ−R′−E” SIN”e −・
・・・・・・−■b −−Ex CO3e + R−E
” 5IN2θ・・・・・・■.

The product, aX b -R"-E' -constant...
...■.

In addition, the value, local maximum value (a+aa++), local minimum value (li,,
) is θ=0°.

That is, the formulas ■,■ are all, I-E+R・・・・・・・・・■b,
,.・−E÷R・・・・・・・・・・・・■Therefore,■
, ■From Eq.

R-(a,,,◆b-,.)/2・・・・・・・・・・
■E -Ca-,,,-b-t,,) /2...
......■.

Furthermore, when the values from the two detection systems are equal to a, that is, aO = bof7), @ = 90° or 270+ and aO' = bO''-R' -E2...
...■. By substituting ■ and ■ expression into ■ expression, E
”(amj% −aO”) / (2X ama++
)=(aO'-1rai,,”)/(2x
b,,)・”・・■R-(ao” “away”)
/ (2X amay)--(aO” +b, in
”) / , (2X b@iR)・---・@.

In this embodiment, the detection system is movably arranged at a predetermined length for the purpose of efficiently using the detection system for each size of wafer. Describing the case where the second origins of the two detection systems are set at a distance of RO from the center of rotation, let the detected values be A and B, and if A>B, then a - A + ROlb - B + RO. .

Therefore, the ■formula is AXB◆(A◆B) x RO-R"-E2-RO"-
C-Constant...■.

In addition, the maximum value, the minimum E, and the value at which the values of the signals obtained from the detection systems 100 and 101 are equal are A, , , respectively.
,B, , ,Il,AO.

Equation 0 is E-(^, □-B+a+, l)'/ 2...
・00 type is R-(^,,8◆B,,,,+2・RO)/2・・
・・・@■ Formula is 2× (＾wmin◆RO) 2 X (Bmin + RO) 3φ formula is 2x (IL□◆RO) 2x (B,,.◆RO).

Next, in this state, rotate the wafer held on the rotating shaft, and
A method for performing alignment based on values from two detection systems will be described.

In this embodiment, the position of the wafer/edge is detected by the linear sensor 6 used as two detection systems, with a second origin (RO) equal to the rotation center of the wafer's rotation axis 8 (outside (opposite to the center direction)). side) is placed as a plus.

Further, one rotation angle is determined from the number of pulses supplied to the stepping motor 9 that drives the rotating shaft 8.

First, calculate the left side of equation (2) using the two detected values A and B, and use the fact that this calculated value is always a constant value (C) unless there is an orientation flat or notch to integrate the y4'IX result. Compare it with the previous calculation result and pay attention to the change.The angle at which the change started (θ.0.) is the angle at which the orientation flat or notch entered, and the angle corresponding to the minimum value of the change is the angle up to the orientation flat or notch. (θ..,), the angle at which the change ended (e a
+t. ) is detected as the angle at which the orientation flat or notch passes.

Also, the two detected values A, +1-, at the angle e, , ,
Bo, , - and calculated values C, , are stored.

Next, the local maximum values of the two detection systems (A + aax or B, ,
, ) and the local minimum (B , in or A, 111) are detected. As for the detection method, the value detected sequentially in each detection system is compared with the previous value, and the O position where it changes from increase to O and decrease is taken as the maximum value, and the 0 position where it goes from decrease to 0 and increases is taken as the minimum value. shall be. If there is a width at the O position, the start position and end position of the 0 position are memorized and the angle at the intermediate position is taken.

If either extreme value is outside the position of the orientation flat or notch, the eccentricity (E) is obtained from equation 0, and the angle to the eccentric position (θt) is the angle to the two extreme values (e-, , ,@,
,, ,Usually @-,,=θ□,,), e,=(θ
Find lIaw + emln ) /2 ・-@”c.

If either value is applied to the orientation flat or notch, the minimum value (A A,
, ll or BB-, ll), and the value (AO) where the two detected values are equal are detected, and the eccentricity (E) is calculated using the [phase] formula. The angle (e2) to the desired eccentric position is the angle (e sat or e, , n) to the extreme value (maximum or minimum value) used.

In addition, the angle to the eccentric position increases as the detected value increases.
90” ahead of the detection system, and
If it reaches AO while decreasing, it is determined that the eccentric position is located 90 degrees behind.

When eccentricity is generally corrected using a two-dimensional stage such as an x-Y stage, the eccentricity at that position is
After determining the displacement in the ring and Y-axis directions and moving in each direction, the wafer is transferred to another wafer support device and held there.
Return the X-Y stage to its original position and transfer the wafer onto the rotation axis again.Also, when making corrections on one axis using a handling arm, make sure that the eccentric direction of the wafer is in the direction of movement of the handling arm. Make sure it matches,
Transfer the wafer to another wafer support device, or make it possible to insert the handling arm, move the wafer to the handling arm, move the wafer outward if the eccentricity is 1t(E) or positive, or toward the center if it is negative, and then move it again. Hold it on the rotating shaft.

In order to locate the orientation flat or notch after replacing the wafer and correcting eccentricity, the position of the rotation center on the wafer is different from the position before correction, so if the same rotation axis is used, it is necessary to locate the orientation flat or notch. It is necessary to correct the angle of the orientation flat or notch.

FIG. 6 is a schematic view of the state when detecting wafer eccentricity, orientation flat, or notch in this embodiment, viewed from above.

In the figure, the wafer 7 is rotated clockwise by the rotating shaft 8.

The angle reference (0°) at this time is on the edge detection system side. Therefore, the starting point of the detection system 101 is 180°. Normally, the detection range of each detection system is 0″ to 180′ for the detection system lOO, and 180° to 360″ for the detection system 101.

Therefore, as mentioned above, the angle e. ,,m+@, etc. are the detection system l
If detected at OO, it is positive (+80°).

ec), and if detected by the detection system 101, it can be treated as a minus (-8°, , -θ, ,).

Furthermore, the orientation flat or notch angle Ce6 after correcting the eccentricity amount. , is obtained as follows.

First, the minimum distance (L) from the center of rotation of the wafer 7 to the orientation flat or notch is calculated as follows: If the radius of the wafer (R) and the radial length (DH) of the wafer or notch are known, then L = R-D) ! is required.

Even if it is unknown, R can be found from equation 0 or 6.

Further, the displacement amount DH is obtained by the following calculation as an approximate value that can ignore errors.

When an orientation flat or a notch is detected by the detection system 101, DH-(C-C,,)/(1. to RO 18) When an orientation flat or a notch is detected by the detection system 100, DI+-(C-C,, ) / (RO÷Bo, =) Next, if the correction angle is ee, then from the law of sine of triangles, L / 5IN (θ.,,, -θt) -E / 5l
)I(8C) Therefore, @ e=SIN-' ((E/L)・5IN(f3
．． , -- @t)) Therefore, co,, is co,,, -601□ order θ. is required.

Here, [111+1 and θ are assumed to be within 0@~±180'.

ec is 1e, , 1.1>1e, :I then plus 21 @
onlIl(l If θ-, it is set as negative.

As described above, according to this embodiment, by only rotating the wafer 7 by a maximum of 1/2, the amount of eccentricity, the angle of the eccentric part, and the angular displacement of the orientation flat and notch can be detected at high speed and with a simple control system. Can be done with precision.

In this embodiment, a linear sensor is used as the detection element of the detection system, but an analog or digital detection element such as a capacitance sensor or a laser scan may also be used.

Further, as a method of detecting one rotation angle, for example, a rotary encoder or the like may be used instead of the stepping motor.

In addition, in the processing of detection data, detection systems lOO and 1
In order to determine the detection state of the orientation flat or notch at 01, a method based on the number of maximum values or the number of inflection points may be used.

Further, it is used as a stage for correcting the eccentricity of the wafer 7 or for the purpose of handling the wafer. A so-called hand link arm or the like may be added to this configuration, and it may also be used in a closed system in which a stage is arranged on a rotating table, or in an oven system in which the wafer and data are transferred to the primary process.

FIG. 7 is a block diagram of an embodiment of the present invention in which the wafer is positioned by the detection system io0.101.

In the figure, if the edge detection values A and B detected by the two detection systems 71 and 72 are analog values, each A
The edge detection values A and B are converted into digital signals by the /D converter 74.75, and when the edge detection values A and B are digital signals, the edge detection values that change successively are compared in time series by the comparison calculation unit 76.77, and the changes are calculated. Local maximum values, local minimum values, and other values are detected based on changes in the sign of the values, and the angle corresponding to that position is detected by the angle detecting section 73 and stored in the storage section 78, 79. Later, the eccentricity and other calculations are performed. Store it as data for.

On the other hand, the detected values from the AD converters 74 and 75 are introduced into the calculation section 80 and subjected to calculation processing so that the influence of eccentricity of the wafer is canceled and only the information on the orientation flat or notch is easily obtained. Based on the changes in the calculated values, the position and dimensions related to the orientation flat, and the corresponding angle are detected by the angle detection section 73, and are stored in the storage section 82 as data for later calculation of correction of the orientation flat. Similarly A/
The two detection values from the D converters 74 and 75 are compared by the comparison section 83, and are stored in the storage section 84 together with the angle of the angle detection section 73 corresponding to the value where the two detection values are equal. Based on these data, the discrimination unit 85 searches for the state of the orientation flat position and the eccentric position, and the calculation unit 86 uses the corresponding calculation formula to determine the amount of eccentricity, eccentricity angle, orientation flat angle, orientation flat depth, and wafer curvature. Calculate radius etc.

Furthermore, in this embodiment, in order to perform alignment in the minimum time, the calculation unit 87 calculates the orientation flat angle after correcting the eccentricity, the drive unit 88 simultaneously controls the eccentricity and orientation flat positioning, and the corresponding actuator 89 is running.

(Effects of the Invention) According to the present invention, two detection systems are arranged at approximately 180 degrees with respect to the rotation axis.
By performing predetermined arithmetic processing using the signals obtained from the two detection systems, detection of wafer eccentricity and orientation flats or notches, which conventionally required two processes, can be performed in one process. It is possible to achieve a positioning device that can collect all the data and position the wafer at a predetermined position with high accuracy and high speed using a predetermined algorithm.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram showing detected values and processed values from the detection system when the wafer is rotated in the present invention, and FIG. 3 is a schematic diagram of a conventional positioning device. FIG. 4 is an explanatory diagram for explaining the orientation flat part of the wafer,
FIG. 5 is an explanatory diagram for explaining the notch portion of a wafer, FIG. 6 is an explanatory diagram for explaining the configuration and correction mechanism of an embodiment of the present invention, and FIG. 7 is an explanatory diagram for explaining an embodiment of the present invention. FIG. 2 is a block diagram of signal processing of FIG. In the figure, too and tot are detection systems, 7 is a wafer, 8 is a rotation axis, l is a light source, 2 is a condenser lens, 3.4 is a mirror, 5 is an imaging lens, 6 is a detection element, 41 is an orientation flat,
42 is a notch, 86.degree. 87 is a calculation section, and 88 is a drive section.

Claims (1)

[Claims] (1) A wafer having an orientation flat or notch on a part of its outer periphery is rotatably held on a rotating shaft, and two detection systems for detecting the amount of radial displacement of the wafer are placed at the center of rotation of the rotating shaft. The wafer is placed oppositely at 180 degrees, and the wafer is
A signal indicating the orientation flat or notch is detected using two output signals from the two detection systems when the wafer is rotated, and the orientation flat or notch on the wafer is determined from the rotation angle of the rotation axis at the time the signal is generated. Means for calculating position and said 2
Based on the output values of the two output signals at each rotation angle, etc., the wafer is positioned at a predetermined position based on each calculated value using means for calculating the eccentric angle and amount of eccentricity of the wafer with respect to the rotation axis. A positioning device characterized by: