JPH02205049A - Wafer positioning system - Google Patents

Abstract

PURPOSE:To correct the eccentricity of a wafer quickly and with high accuracy for positioning by a method wherein the variation curve of a pixel number detected by a linear sensor in regard to the circumference of the wafer and an angle signal are processed. CONSTITUTION:A detection signal is outputted from a pixel detected in accordance with the circumferential radial position in regard to the rotation center of a wafer 1 and the signal is inputted to a pixel number detecting circuit 7. The outputted pixel number is inputted to a microprocessor 4 together with an angle signal from an angle detector 8 and the angle of the center of the orientation flat(OF) of the wafer 1, the angle of the eccentricity of the wafer 1 from the center of the OF and the eccentricity are calculated and stored in a memory 4a. In accordance with the stored data read out of the memory 4a, the wafer 1 is turned until the angle of the center OFc of the OF agrees with a reference angel and stopped by a rotation control circuit 5 and a spindle motor 6a. Then the wafer 1 is attracted by an attracting mechanism 10 are shifted to the direction of the eccentricity. The shift distance can be obtained by multiplying the stored eccentricity by a suitable factor.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wafer positioning method, and in detail,
The present invention relates to a method of positioning the wafer by aligning the wafer's orientation O-flat (OF) with a reference position and correcting the eccentricity of the wafer with respect to the center of rotation.

[Prior Art] IC chips for semiconductor products are manufactured by projecting and exposing an IC pattern onto a wafer of silicon or the like using a mask, performing predetermined processing, and then cutting the wafer into individual chips. Since IC chips are correctly positioned and processed in each processing device, it is necessary to align the orientation flat (OF) provided on the wafer with the reference position of the processing device for positioning purposes. .

4(a), (b), and (e) show the format of the OF. In FIG. 4(a), one straight OF is provided on the outer periphery of the wafer 1, and in FIG. 4(b) In this case, an OFl and a shorter OF2 are provided at two positions perpendicular to each other. On the other hand, in Figure (c), a V-shaped notch is provided instead of OF2. For positioning, please refer to the figure (
In the case of a) and (C), the OF is targeted, and in the case of the wafer in FIG. 3(b), the OF is targeted, and their centers are made to coincide with the reference angle.

FIGS. 5(a) and 5(b) illustrate an embodiment of a conventional wafer positioning method. In FIG.
b + 2 c, rotate the wafer, detect the position where all the sensors receive light, and set this as the reference position (angle).
position as. In Figure (b), the number of the light receiving pixel of the linear sensor 3 changes at the OF position, so the OF is detected and positioned based on the change in number.

[Problem to be solved] In the positioning method shown in FIG. 5(a) described in -1-, OF matches the reference position, but as shown in FIG. 4(b), there is OF l + OF 2. In this case, it is necessary to determine the OFI by some method.

Further, when the wafer 1 has eccentricity, not only the direction but also the amount of eccentricity is not detected, and therefore the eccentricity cannot be corrected. On the other hand, in the method shown in FIG. 5(b),
First, the method is to align the OF with the level position, then check how the numbers of the light-receiving pixels of the linear sensor change due to the eccentricity of the outer periphery, move the wafer through some trial and error, and correct it so that the number changes are minimized. It is being done. For recent high-density IC chips, there is a drawback that it takes a long time to achieve high-precision alignment using the above correction method. In response, there is a need for a method for quick and highly accurate positioning.

This invention has been made in view of the above, and is shown in Figure 1 (
To provide a wafer positioning method that takes the linear sensor method of b) one step further and quickly and accurately corrects eccentricity and aligns a wafer with OFs provided at one or two locations. The purpose is to □
[Means for Solving the Problems] The present invention uses a linear sensor that detects the radial position of the outer circumference of the wafer with respect to the center of rotation in positioning a wafer having an orientation flat (OF) provided on the outer circumference of the disk. The wafer is rotated once by the rotation mechanism, and the angle of the center of the OF, the angle of the eccentric direction of the wafer with respect to this center angle, and the amount of eccentricity are determined using the rotation angle data and the change curve of pixel number with respect to the radial position detected by the linear sensor. is calculated and stored in a memory, the center angle, the angle in the eccentric direction, and the amount of eccentricity are read out from the memory, and the wafer is rotated by a rotation mechanism to stop the center of the OF at a reference angle, and The wafer is moved by the eccentric amount in the opposite direction to the eccentric direction.

The minimum and maximum values of the pixel number with respect to the outer periphery of the "urchin" are detected by the microprocessor's second-order differential processing with respect to the change curve of the pixel number, and the small centering angle of the OF is determined based on the minimum value or maximum value. Or calculate the angle of the eccentric direction of the wafer. : When the OF is provided at a location perpendicular to the wafer, ・
This is a conflict in which the OF corresponding to the smaller number among the pixel numbers corresponding to the radial position detected by the linear sensor is set as the OF for position 1 positioning.

[Operation] The operation of the wafer positioning method according to the present invention is shown in FIG.
); explained by (b), (c') and (d).

In Figure (a), a sensor 3 is provided on the outer periphery of the wafer 1 to detect the radial position from the center of rotation 0 of the wafer. Figure (b) shows a case where the center point OFc is at the reference angle, the wafer is eccentric in the direction of the diameter p2-+pl (dotted line), and the eccentricity is δ, rl=δr2. The diameter ct -C2 in the direction perpendicular to the diameters p and -p2 is non-eccentric. The center of the wafer has moved to 0' with respect to the rotation center O, and the diameter Pt -P2 with respect to the radius 0-OFc.
is in the direction of angle o1 or C2. Now, when the wafer is rotated once by the rotation mechanism, the pixel number with respect to the outer periphery detected by the linear sensor 3 changes depending on the OF and eccentricity. Here, the pixel numbers are assigned such that they increase in the radial direction from the inside, for example, and the smallest number among the pixels that receive light indicates the position on the outer periphery.

In the following, for convenience, the smallest number will be referred to as the pixel number.

Figure (c) is a change curve of pixel number against rotation angle θ,
For the pixel number Nc for the non-eccentric point CI + C2, pl, which shows the maximum value due to eccentricity, and p, which shows the minimum value, due to eccentricity.
2 appears. Further, the pixel number changes near OF and reaches a minimum value at the center point OFc. The figure shows a particularly large eccentricity; in reality, it is roughly centered and the eccentricity is small, but the amount of change in OFC is quite large.

Note that if the numbering is reversed from the above, the maximum, minimum, etc. will be swapped.

When a microprocessor performs second-order differential processing on the change curve data described in "-, the zero point indicates the minimum or maximum value of the curve, so the angle of OFc can be calculated using these minimum or maximum values and rotation angle data. Then, the angle freeze θ1 or 02 of 1)1 or p2 for OFc is calculated and stored in the memory.

After reading this data and rotating the wafer using a rotation mechanism to match OFc with the reference angle, the wafer is moved in the direction of angle θl (or C2).

The amount of movement δr is determined by multiplying the deviation δr1' (or δr2') of pt (or I)2) from the center line Nc by an appropriate coefficient.

When there are OF l* OF 2 in two places on the wafer,
As shown in Figure (d), the pixel number curve has a local minimum value Nl at two locations, each center point 0Fcl and 0Fc2.
and N2 appear, but as mentioned above, compared to OFt, OF
2 is short, so Ns < N2, and OFl is used for positioning.
is identified. Note that the same applies when a V-notch is provided instead of OF2.

The control of the rotation mechanism and movement of the wafer and the data processing of pixel numbers are performed by a microprocessor.

[Embodiment] FIG. 2 shows a circuit configuration diagram of an embodiment of the wafer positioning method according to the present invention, and FIGS. 3(a) and 3(b) are schematic flowcharts for FIG. 2.

In FIG. 2, a wafer 1 is attracted to a spindle 6 and rotated by a spindle motor 6a.

The rotation angle is detected by an angle detector 8 and an angle signal is output. A light beam is projected onto the outer periphery of the wafer 1 from a light projector 3a, and is received by a one-dimensional CCD linear sensor 3. A light reception signal is output from the light receiving pixel according to the radial position of the outer circumference with respect to the rotation center of the wafer 1,
This is input to the pixel number detection circuit 7. Numbers are assigned to pixels sequentially from the inside in the radial direction, and the lowest number among each pixel that receives light is detected and output as the pixel number. The output pixel number is input to the microprocessor (MPC) 4 along with the angle signal from the angle detector 8, and the angle of the center of the OF, the angle of the eccentric direction of the wafer relative to this, and the amount of eccentricity are determined by the method described above. These data are calculated and stored in the memory 4a. This data is read, and the rotation control circuit 5 and spindle motor 6a rotate the wafer 1 to an angle at which the center OFc coincides with the reference angle, and then the wafer 1 is stopped. Next, the spindle 6 is released from suction by a command from the microprocessor 4, and the wafer 1 is suctioned by the suction mechanism 10 of the moving mechanism 9 and moved in an eccentric direction. The amount of movement is determined by multiplying the stored eccentricity amount by an appropriate coefficient. Note that the movement method may be different from the above, for example, a method in which the entire rotating mechanism such as wafer 1 and spindle 6 is mounted on an XY movement mechanism and moved; in that case, wafer 1 remains attracted to spindle 6. Moving.

In the broach yard of FIG. 3(a), the wafer is first rotated (2), and the above-mentioned pixel number for the outer circumference of the wafer is detected and stored in the memory (2).

The microprocessor performs second-order differential processing on the pixel number curve and detects a zero point (2), which indicates the center OFc and the local maximum value pl and local minimum value p2 due to eccentricity. The distance between pl (or p2) and the center line Nc in FIG. 1(c), that is, the eccentricity δrl' (or δr2
′) is calculated■. % OF c with reference to the angle signal
and pt (or p2) angle θl (or θ2)
Calculate ■, rotate the wafer so that OFc matches the reference angle, and stop ■. The stopped wafer is moved by a movement amount δr1 in the direction opposite to the eccentric direction (diameter P1-P2), and positioning is completed. The amount of movement δrl can be obtained by multiplying the above δr1' by a coefficient determined by measurement in advance. Figure (b) is for a wafer with OFs provided at two locations, as described above, the center 0Fc1 and 0Fc1.
The smaller of the pixel numbers N1 and N2 for C2 is for the positioning OF, so compare the sizes.

When Nl is small, 0Fct and pl (or 1)
2) Calculate the angle θ1 (or θ2), and when N2 is small, calculate θ1 (or θ2) for 0FC2 [phase]. These steps (■) to [phase] are inserted between (2) and (2) instead of (2) in Figure (a).

[Effects of the Invention] As is clear from the above explanation, in the wafer positioning method according to the present invention, the center of the OF is The angle, the angle of the eccentric direction of the wafer with respect to the center of rotation, and the amount of eccentricity are determined, and the eccentricity is corrected by stopping the rotation of the OF at a reference angle based on the angle of the center, and moving the wafer in the opposite direction to the eccentric direction. The operation of each mechanism and data processing are performed by a microprocessor, and it has a great effect on quickly and highly accurate positioning for any wafer with one or two OFs. be.

[Brief explanation of the drawing]

FIGS. 1(a), (b), (c), and (d) are explanatory diagrams of the operation of the wafer positioning method according to the present invention, and FIG.
FIGS. 3(a) and 3(b) are circuit configuration diagrams in an embodiment of the wafer positioning method according to the present invention, and FIGS.
is the orientisilon j flat provided on the wafer (
Explanation/diagram of the arrangement of OF) and V-notch, Fig. 5(a)
and (b) are explanatory diagrams of a conventional positioning method for the wafer 1. 1... Wafer, 2... Optical sensor, 3
... Linear sensor, 3a... Floodlight, 4...
Microprocessor, 4a...Memory, 5...Rotation control circuit, 6...Spindle, 8,a...Spindle motor, 7...Pixel number detection circuit, 8...Angle detector, 9
...Movement mechanism, 10...Adsorption mechanism.

Claims (3)

[Claims] (1) In positioning a wafer with an orientation flat (hereinafter abbreviated as OF) on the outer circumference of a disk, a linear sensor is provided to detect the radial position of the outer circumference with respect to the rotation center of the wafer, and the sensor is controlled by a microprocessor. The wafer is rotated once by the rotation mechanism, and the angle of the center of the OF and the eccentricity of the wafer with respect to the center angle are determined based on the angle data of the rotation and the change curve of the pixel number with respect to the radial position detected by the linear sensor. The direction angle and the amount of eccentricity are calculated and stored in the memory, the stored center angle, the angle of the eccentric direction and the amount of eccentricity are read out, and the wafer is rotated by the rotation mechanism and stopped at the center of the OF at the reference angle. and moving the wafer by the eccentric amount in a direction opposite to the eccentric direction. (2) The minimum value and maximum value of the pixel number with respect to the outer circumference are detected by the microprocessor's second-order differential processing on the change curve of the pixel number, and the center of the OF is determined based on the minimum value or maximum value. The wafer positioning method according to claim 1, wherein an angle or an angle in an eccentric direction of the wafer is calculated. (3) For the OFs provided at two locations perpendicular to the wafer, position the OF that indicates the pixel number with the largest change among the pixel numbers corresponding to the radial position detected by the linear sensor. As OF for
The wafer positioning method according to claim 1.