JPH01169939A - Centering equipment for semiconductor wafer - Google Patents

Abstract

PURPOSE:To prevent the damage of wafer and the generation of dust, by rotating the wafer to detect edge position variation in the non-contacting manner, calculating the eccentricity quantity and direction of wafer according to the detected results, and performing positioning. CONSTITUTION:A wafer 1 is mounted on a turn table by a conveying equipment (not shown in figure). A table 2 is rotated by a motor 4. The edge position lx of the wafer 1 is detected every specified rotation angle of the table 2, by a detector 5 constituted of a light projector 5a and a photo sensor 5b. The position lx is stored in a memory circuit 7 together with a table rotation angle gammax from an encoder 6. An operating circuit 8 calculates eccentricity quantity (x, y) and eccentric direction theta of the wafer 1 according to thetax, lx in the memory circuit 7. A control circuit 9 drives the motor 4 according to theta, and a control circuit 11 drives an XY table 10 according to (x, y). Centering of wafer 1 is enabled without contacting of edge and siliding of wafer, so that the damage of wafer and the generation of dust can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for accurately aligning the center of a semiconductor wafer when the semiconductor wafer is transported in a semiconductor manufacturing apparatus.

[Conventional technology]

In semiconductor wafer manufacturing equipment, it is necessary to accurately center the wafer when transferring semiconductor wafers from one cassette to another, to each stage for inspection or processing, or between stages. be. Normally, the cassette and each stage do not have this centering function, so a method is used in which a centering device is added during transportation between them. FIG. 10 is an outline drawing showing an example of such a conventional device,
In the same figure (a), the sea urchin 102 is dropped into a container 101 called a centering cup whose inner diameter changes in a tapered shape, and in the same figure (b), the wafer 102 is held between the scroll chuck 103. This is for centering.

[Problem that the invention seeks to solve]

In the conventional equipment described above, because the centering is performed by rubbing against the edge or back side of a thin wafer, the generation of dust, which is the most hated thing in semiconductor manufacturing equipment, cannot be avoided, and there is also a risk of damaging the wafer. However, in order to prevent damage, it was necessary to carry out the centering operation several times (lithography), which had the disadvantage that high speed could not be achieved.

[Means for solving problems]

The present invention focuses on the fact that the wafer is processed in advance into a nearly perfect circle using an NC device, etc., rotates the wafer, detects and stores the edge position corresponding to one rotation angle, and generates a detection signal. maximum value.

Calculate the eccentricity and direction of the wafer position based on the minimum value,
The wafer is centered based on this bias data. Furthermore, the wafer has a flat part (or notch) at its periphery to indicate the crystal orientation, but the starting and ending points of these flat parts are smaller than those in other parts. Since the change in edge position becomes sudden, it is necessary to calculate the point where the rate of change in edge position data exceeds a certain level (therefore, this flat part, etc., must be set at a specific position relative to other stage numbers of the conveyance device, etc.). 9 [Function] The present invention has the above-mentioned configuration, and the centering of the wafer can be performed for each table on which the wafer is placed or from the edge position detector. This is done when transferring to another stage.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the apparatus of the present invention.

In the figure, reference numeral 1 denotes a semiconductor wafer to be centered, which is placed on a turntable 2. As shown in FIG. 3 is a turntable rotation mechanism for rotating the turntable 2, and is driven by an electric motor 4. , 5 is wafer 1
A detector for detecting the edge position of
It consists of a light projector 5a and a light sensor 5b. This sensor 5
b is one in which the output changes continuously while maintaining a specific relationship depending on the amount of light received;
It is desirable to use a detector whose output changes linearly by 1 with respect to the amount of incident light, which is called an ive detector. 6 is an encoder that detects the amount of rotation of the electric motor 4 corresponding to the rotation angle of the turntable 2 and outputs a digital signal;
is a storage circuit that stores the output of the sensor 5b and the output of the encoder 6 as a pair of data for every fixed rotation angle of the turntable 2. Here, if the output of the sensor 5b is an analog signal, A
/D converter may be provided.

8 is an arithmetic circuit that reads the output of the memory circuit 7, calculates the eccentric position and direction of the center position of the wafer l, and outputs correction signals (rotation angle and horizontal position signals), which is used by the microcomputer. can. When a microcomputer is used as the arithmetic circuit, the edge position detection special number table 9 is a servo control circuit for controlling the rotation of the turntable driving electric motor 4. This is a normal servo control circuit that drives the motor 4 and stops it when the rotational motion matches the output of the encoder 6. Reference numeral 10 denotes an XY table-type movement mechanism for moving the turntable 2 along with its rotational drive mechanism within the XY horizontal plane of the figure, which moves the table 2 according to the output of the arithmetic circuit 8 to correct the position of the wafer 1. The position is controlled by the XY child table operation control circuit 111.

The operation of the apparatus shown in FIG. 1 will be explained with reference to the flownayat shown in FIG. In FIG. 1, when a wafer 1 is placed on a turntable 2 by an m feeding device (not shown), an electric motor 4 rotates, and a turntable rotation mechanism 3 driven by this rotates the wafer at a predetermined angle (for example, 1 degree).
Rotate. During this process, the sensor 51 of the edge position detector 5 generates an output corresponding to the amount of light that is reduced by the wafer directly under the sensor and reaches the sea urchin, and this output is sent to the sea urchin along with a rotating violet signal as well as a pair of data (θ, , 1x ) is stored in the memory circuit 7.

Further, the turntable 2 is rotated a predetermined number of times, and the edge position detection and memorization are repeated, and the wafer is transferred to the employee ti! Continue until the rotation is 360 degrees from (θ = 0). When the detection of the edge position around the entire circumference of the wafer is completed, the arithmetic circuit 8 sequentially reads out the data stored in the memory circuit 7 and calculates the maximum value gmax and minimum value 'min' of the edge position signal and the corresponding wafer noise. ) rotation angle oInaX 'θm
Calculate in. The arithmetic circuit 8 also calculates a diametrically eccentric amount signal ΔA=(
A'max1min)/2 is obtained, an eccentric angle signal is obtained from θmax (or 0m1n), and a deviation signal (x, y)-(△ l CO3θmax,
Δ#sinθmax > or (x, y)=(△l s
inθmln, Δl cosθm1n) and supplies a correction signal determined by these to the XY table control circuit 11 to perform centering.

The wafer edge position detector 5 and the signals obtained therefrom will now be explained. FIG. 3 is an explanatory diagram showing an enlarged portion of the detection 45, and the same reference numerals are given to the same functions as in FIG. 1 in the figure. The light from the projector 5a is blocked by the wafer 1, as schematically indicated by the arrow in the figure, a part of it is reduced, and the rest reaches the sensor 5b. Therefore, if a sensor 5b whose output changes in direct proportion to the shear force and light pollution is used, its output will be a signal proportional to the length of l which changes depending on the position of the edge portion of the wafer 1. Therefore,
If the wafer is deviated toward the edge position detector with respect to the center of the turntable, the output signal will be small, and if it is deviated to the opposite side, the output signal will be large. Sensor 5 at this time
The state of the output change of b is shown in the diagram of FIG. In the figure, the horizontal axis represents the rotation angle θ of the wafer, and the vertical axis represents the output l of the optical sensor 5b. In addition, (a) in the same figure shows the output when the wafer 1 is aligned with the center of the turntable 2 as shown on the left. In this case, as mentioned earlier, the wafer 1 is Since it is machined into a perfect circle, the output of the optical sensor is linear. Figure fb) shows the output when the center of the wafer 1 is shifted from the rotation center of the turntable 2 to the first position of the XY plane of the XY child table 0 by a distance Δl at an angle θ. At this time, the output of the optical sensor 5b changes approximately sinusoidally as the wafer 1 rotates in the direction of the arrow in the figure. The amplitude of the change is the maximum value of the output llmax s i & the minimum value Nm1
If n is (emax gmin), it corresponds to twice the amount of eccentricity Δl. Further, the angle θmax when l''1m&X corresponds to the eccentric angle of the wafer 1 when the sensor direction on the XY plane is the rotation origin. (Note that g=
The effect is the same, except that the angle θm10 used when gmin is used and the positive direction is reversed. ) Therefore, from these signals, the current wafer center position is determined by the coordinates (x, y)
It can be seen that =(△l cos θmax, △/sin θmax >).

(When adopting 0m10, (x, y) = (Δg si
nθm10°Δl cosθm1n). ) Therefore, move the XY table in the X direction -△l cosσmax
If the wafer is moved in the -X direction by -l sinamaX, the wafer can be centered.

The present invention also provides the following advantages by devising the contents of the arithmetic circuit.
Centering and flat part (or notch S) when a flat part (or notch S) is provided at the periphery of the wafer
It is also possible to perform alignment at the same time.

FIG. 5 [al is a plan view of a wafer in which a flat portion (A) is provided on a part of the peripheral edge;
1 shows an example of the output waveform of the edge position detector when a wafer having such a shape is placed on the turntable eccentrically in various directions. When a wafer with a shape like that shown in Fig. 5 (al) is rotated,
), the flat part (or notch part) (a) of the wheel ζ exhibits a significantly different output change from the other circumferential parts. In particular, since the rate of change is extremely large at both ends, the position of the flat portion can be detected by monitoring the rate of change in the output of the edge position detector. Therefore, in the present invention, the arithmetic circuit 8 is configured so that a portion where the rate of change of the edge position detection signal exceeds a certain level is determined to be a flat portion. In this case, the limit of the rate of change is the difference between the maximum value and the minimum value of the output signal, because the maximum rate of change when detecting the circumference differs depending on the amount of eccentricity of the wafer, that is, the approximate amount of eccentricity, It may be determined accordingly. Furthermore, since the method for calculating the amount of eccentricity differs depending on the position of the flat portion (or notch) and the eccentric direction of the wafer, it is also necessary to determine this. Figure 6 shows the 70-nayat when this is done. Here, steps 1 to 7 are the same as in the case of FIG. 4 without a flat part. Among the output signals of the four optical sensors 5b, the maximum and minimum values are true values because of the existence of a flat part. Although there is a possibility that there is no difference, step 8 is the maximum value broken in step 7! 1max and the minimum value amlo, (#max ffm1nJ is obtained, and the upper limit value α of the rate of change is determined by this. The point of α (θl ~ θ
Find n). Next, it is determined whether the angle 'max when the output is maximum (#=l1max) is in the relationship θ□≦θ□, ≦θ□, and if θ□≦θmax≦0n holds true, then The position of the maximum value 'maX in step 7 obtained by rotating the wafer to
Since it is in a state like zubushu), it means that it is not superior to the true maximum A1. Therefore, the minimum value emi is used as a reference.

The angle θmin corresponding to #m1nl is set as the deflection direction (direction of center deviation), and a point 90 degrees away from this (when θmin≦270 degrees, θmin+90 degrees, θm
l, >270 antis, the output of θm1n-90 antis) is the midpoint l
. The wafer center deviation amount △1l=11c
Obtain 6m1n. From this result, the current position coordinates of the wafer center (x, y) = (Δ1 sin θml., Δl
0080m1n) is obtained. (However, the direction of the optical sensor 5b is ±X.) On the other hand, the angle θmaX at which the output l reaches the maximum value 1maX is θ, and θ. If the interval 4 does not come, the flat part is at another position, so step 7 is used as the amount of firework deviation.
Adopt l maX obtained in , and set θma as the deviation direction
Adopt X. (Fig. 5 fb), (d), (e
), then) the point θf next to emax by 90 degrees
It is determined whether or not is within the flat area, and if it is, the position 270 degrees ahead (4 or 90 degrees behind) is θ. , the value of l at that time, and if it is not a flat area, the point θf is θ
. The value of l at that time is the midpoint l. , and obtain the wafer deviation amount Δ(1=1ma, c-β0. At this time, the angle θ of the midpoint position. Then, the position θf to be determined of the flat part and the midpoint are determined by the value of θrnax. The corresponding angle θ of the output to be adopted is as shown in Table 1. An example of the output waveform of the detector at this time is shown in Figure 7. ) is shown in Table 7, 2.
(dl corresponds to 3 in Table τ Table 1 (however, when θ1 x θf x θ□).

From the above results, the current position coordinates (x, y) of the wafer center
=(△lCO3θmaxI△1sin amax)
get.

Note that the above is an example of a method for calculating the wafer eccentric position and deviation direction when the amax position is used as the reference, and this calculation method is compared with the method based on IPin and the standard sine wave. The method is arbitrary, such as calculating A'max −Nm1n −k by predicting it from the data of the flat part.

In the above, an example has been described in which all of the wafer turntables 2 are centered in accordance with the output of the arithmetic circuit 8 using an XY child table, but the present invention is not limited to the number of apparatuses having such a structure. No, for example xY
Instead of the table, a table movable only in one axis direction (for example, the X axis) may be used.

In this case, as in the previous explanation, rotate the wafer once, calculate e and direction θ to the eccentric position of the wafer center, and when centering, first move the wafer turntable in the direction (- 〇), and after aligning the deflection direction with the X-axis direction, move the entire turntable by 1△l (However, the order may be reversed or the rotation and X-direction correction may be performed at the same time.) , ) When doing this, the turntable position can be corrected only on one axis, which simplifies the structure and also simplifies control.

Further, in the embodiment shown in FIG. 1, centering and orientation were performed by moving the entire wafer turntable in the horizontal direction and rotating it, but the present invention is not limited to this. After calculating the amount, the wafer may be lifted from the turntable, separated from the turntable, moved horizontally one step in this state, and placed on the turntable again using a three-dimensional handling method. Furthermore, in cases where the wafer is transferred to another stage and processed after being centered,
If only the calculation of the center position of the wafer is performed following the edge detection, and the centering is performed by correcting the distance signal between devices for the amount of movement during transfer, the centering process and the transfer process can be integrated. Since this can be done in the process, the wafer moving means of the centering device can be omitted and the takt time can be shortened.

FIG. 8 is an external view showing another embodiment of the present invention, in which a three-dimensional robot is used as the wafer handling means.

In the figure, reference numeral 21 denotes a wafer stocker in which wafers collected on other stages (not shown) are stored.

A processing stage 22 is provided with processing equipment for performing predetermined processing on the centered wafer. 2
3 is a robot with 3 axes (X-axis = horizontal direction, 2-axis = rotational direction, 2-axis = upper F direction), and has a claw at the end of its arm for transferring the wafer. , 24 is a nine-piece center detection mechanism for detecting the center position, and is composed of the turntable 2, edge detector 5, and their accessories in Embodiment I of FIG. 1, and 27 indicates these. This is the base it is equipped with. In addition, the control device is not shown in the figure. The operation of the apparatus shown in FIG. 8 will be explained with reference to the flowchart shown in FIG. In the apparatus shown in FIG. 8, the robot 23 first rotates its arm to place the wafer stocker 2 on the wafer stocker 2.
One of the wafers 1 to 9 is taken out, rotated clockwise approximately 1800 degrees, and placed on the turntable 2 of the wafer center detection mechanism 24.

After the arm of the robot 23 is retracted, the wafer rotates once by the turntable 21ζ of the wafer center detection mechanism, and the center position is calculated from the direction of the edge position detector 5 as described above. Robot 23 whose calculation results are not shown
supply to the control circuit.

Here, if the wafer l has a flat part or a notch and it is necessary to align this direction in a certain direction I, the flat part position direction signal obtained by the previous edge position detection operation ( After the turntable 2 is further rotated according to the flowchart of FIG. If the movement value is determined by a signal corrected with respect to the true positional relationship between the wafer center detection mechanism 24 and the processing stage 22 using the signal calculated previously during center position detection, the wafer transferred to the processing stage will be The position is accurately centered with respect to the processing stage.

In the apparatus shown in FIG. 8, after an eccentricity signal is obtained by the center position detection operation), the wafer is once lifted from the turntable by the robot 231ζ, and the wafer is moved by the l-axis and l-axis of the robot 23 in response to the positive eccentricity signal. It is also possible to adopt a method in which the flea is moved and then placed on the turntable again for centering.

〔Effect of the invention〕

As described above, in the present invention, since the device rotates the wafer, calculates the eccentricity and direction of the wafer, and moves the wafer according to the calculation results, it does not damage the edge unlike the conventional device. There was no problem, and it was 9th and 11th.
Since there is no sliding movement, there is no generation of dust.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a 70-chart for explaining the operation of the device shown in Fig. 1, and the third factor is the detector 5 in the embodiment f of Fig. 1. 4 (al and (bl) are diagrams showing changes in the output of the sensor 5b, and FIG. 5 (al is a part of the periphery where a flat portion is provided. Figures 5(b) to 5(e) are plan views showing examples of wafers in which the wafer 1 (shaped like ``al'') is placed on a turntable with various orientation angles ζ eccentricity. A diagram showing an example of the output waveform of the edge position detector, FIG.
70-chart when calculating the eccentricity and direction of 1, Figure 7 (alt-[d) shows an example of the output waveform of the edge position detector when the flat part is included in one of the midpoints. 8 is an outline drawing showing another embodiment of the present invention, and FIG. 9 is a diagram showing 1...wafer, 2...turntable, 5...
9/1 Edge detector, 5a... Floodlight, 5b...
Optical sensor, 6... Encoder, 7... Memory circuit, 8
...Arithmetic circuit, 9...Servo control circuit, 10...
XY table, 11...XY table position control circuit,
21... Wae/-1 stocker, 23... Robot,
24... Waeno 1 center detection mechanism. Agent: Hiroshi Nakai, Patent Attorney Figure 6 Figure 10

Claims (1)

[Claims] 1. Wafer rotation means for mounting and rotating a circularly shaped semiconductor wafer, an edge position detector for obtaining a signal related to the edge position of the wafer in a non-contact manner, and the edge A storage means for storing the output signal of the position detector as data corresponding to the wafer rotation angle for each predetermined rotation angle; and a storage means for reading out the wafer edge position data stored in the storage means and storing the maximum value or the minimum value of the wafer edge position signal and the maximum value. and a wafer drive means for centering the wafer in accordance with the output of the calculation means. Wafer centering device. 2. The semiconductor wafer centering apparatus according to claim 1, wherein the wafer driving means is means for horizontally moving the entire rotating means on which the wafer is placed. 3. The wafer driving means is a mechanism for transferring the wafer from the wafer rotation means to another, and the centering of the wafer is performed by correcting the amount of wafer movement at the time of wafer transfer using the output of the calculation means. 2. A semiconductor wafer centering apparatus according to claim 1, wherein the centering apparatus is a means for performing centering of a semiconductor wafer. 4. The calculating means is means for calculating the eccentric direction of the wafer as an angle with respect to the original rotational position of the wafer, and the wafer rotating means calculates the eccentric direction of the wafer after rotating the wafer in order to detect the edge position. Means for further rotating the wafer according to the calculated eccentric direction signal until a specific axial direction of the wafer driving means and the eccentric direction match, and centering the wafer is performed using the specific axis of the driving means. The semiconductor wafer centering apparatus according to claim 1, which is performed by a chisel. 5. An apparatus for centering a semiconductor wafer that is shaped into a circle and has a flat part (or notch) on a part of the circumference, comprising: a wafer rotation means for rotating the wafer; and a wafer rotation means for rotating the wafer; an edge position detector for obtaining related signals in a non-contact manner; a storage means for storing the output signal of the edge position detector as data corresponding to a wafer rotation angle for each predetermined rotation angle; and a wafer edge position stored in the storage means. Read the data and set the maximum value of the wafer edge position signal,
a calculation means for calculating the eccentricity amount, eccentric direction, and center position of the flat portion (or notch portion) of the wafer by calculating the minimum value and rate of change; A semiconductor wafer centering device comprising a wafer drive means for aligning the center of a semiconductor wafer (or a notch) at a specific angle.