JPS60218853A - Wafer front aligning 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] This invention provides a method for pre-aligning silicon wafers.
ign).

[Conventional technology]

During the manufacture of integrated circuits, it is necessary to prealign silicon wafers before sending them to the processing shop. At the processing plant, the wafers are precisely aligned before the eight turns of circuitry are etched onto the wafers. Pre-alignment is important because the wafer must be accurately and sufficiently positioned within the precision alignment mechanism. [Problem that the invention seeks to solve] Currently available pre-alignment equipment does not center the wafer. That is, it is necessary to perform positioning in the X-Y directions before determining the angular orientation. 2. It moves the wafer to the pre-aligner stage.
This is because the feed is shifted by 546 In (1 inch) or more. This is outside the scope of currently available angular orientation techniques.

The present invention solves the problems mentioned above and provides an accurate pre-alignment device that can angularly orient the wafer without first having to center it in the X-Y directions. In other words, the present invention is a pre-alignment device that can angularly orient a wafer without requiring a full x-y centering stage.

[Means for solving problems]

The invention includes a shaft, a means for rotating the shaft, and a vacuum forming means for holding a wafer in association with the shaft during rotation thereof. A light source and a light sensor are placed on either side of the wafer.

[Effect]

Once the wafer has been rotated one complete revolution, the optical sensor detects the edge of the wafer and provides a signal representing the eccentricity, ie, the distance of the wafer from the center in the X-Y directions. This signal also indicates the angular position of the wafer by sensing depressions or protrusions in the wafer. The type of photosensor used has a linear dimension that ensures that the shadow created by the light source is such that the edge of the wafer is within the field of view of the photosensor. Signals from the optical sensor are fed to a computer where they are used to calculate the X-Y position and angular orientation of the f-wafer.

Since the wafer's angular orientation is known, the shaft is rotated to orient the wafer to the desired angular orientation. Information representing the X-Y position of the wafer can be used to center the wafer as it is transferred to the next stage.

〔Example〕

FIG. 1 shows the wafer pre-alignment (pre-alignment) of the present invention.
gnment) device 10 is shown. The wafer pre-alignment device 10 includes a shaft assembly 11;
The shaft assembly 11 has a housing 12. The shaft 13, with the help of a conventional bearing 14,
It is rotatably mounted within the housing 12. shaft 1
One end of 3 becomes a cup-shaped element 15. A funnel 16 is formed within the shaft 13, and this conduit 16 communicates with a tube 18 via a funnel 17 formed within the housing 12. Thus, a wafer 19 transferred to element 15 can be clamped to element 15 by vacuum applied through conduits 16 and 17 and tube 18 to the center of element 15.

The third motor 20 is arranged at the other end of the shaft 13,
and is used to rotate the shaft 13 when energized by the motor drive 21. A resolver 22 is also arranged at the other end of the shaft 13, and this resolver 22 supplies a signal representative of the angular orientation of the shaft 13. This signal is fed to a signal processor 23 where it is digitized into accurate numbers for the individual angular positions of the shaft 13. That is, a number indicating the angular position of the shaft 13 every 10 to 20 arc seconds is determined and input into the computer 27. Such resolvers and processing electronics are well known and commercially available.

On one side of the wafer 19 is a light source 24, which may be a light emitting diode, a laser diode or other conventional light source. On the other side of the wafer 19, placed virtually in the path of the light beam from this light source 24, is a light sensor 25, which may be a charge coupled device array. The light source 24 and the light sensor 25 are placed in the expected approximate position of the edge of the wafer 19 such that the light source 2 projects the shadow of the edge of the wafer 19 directly onto the light sensor 25 or indirectly by means of an optical system. Placed.

The optical sensor 25 is chosen to have a length that captures the shadow of the edge of the wafer 19 over a wide range of eccentricity. For example, when wafer 19 is transferred to shaft 13, 1.
It can be off-centered by more than 77 cm (0.5 inch).

An example of such a photosensor is a charge coupled device array manufactured by Texas Instruments, such as the TO103. Such a charge-coupled device array has 2
．． 200 with a detection length of 54 cIn (1 inch) or more
Since it is composed of zero or more charge-coupled devices, this charge-coupled device array can accommodate large variations in eccentricity, such as eccentricity variations of 1.77z or more, i.e., the amount of off-centering when the wafer 19 is transferred to the wafer pre-aligner 10. .

The illustrated lens array positioned between light source 24 and wafer 19 directs light in a radial line across the edge of wafer 19 . An optical lens between the wafer 19 and the optical sensor 25 telecentrically transmits the light beam to the optical sensor 25.
entric) gives an image. This provides a virtually collimated light beam on the sensing surface, so that the edge shadow cast on the sensing surface of the photosensor 25 is sharply defined. Other lens configurations may be used to achieve this purpose.

As shaft 13 rotates, optical sensor 25 is periodically electronically scanned to generate an analog output signal.

This analog output signal of photosensor 25 is provided to a linear array signal processing circuit 26 which represents the wave edge position at a given shaft angle and is input to a computer 27.

Digital information from the linear array signal processing circuit 26 is provided to a computer 27, which may be an Intel 8088 commercially available from Intel Corporation.

The digital linear output and appropriate resolver shaft angle data are stored in computer 27 until rotation of wafer 19 is complete. computer 27 is wafer 19
with sufficient information to calculate the X-Y position and angular orientation of.

Since the desired angular orientation of the wafer 19 is a known quantity and can be permanently stored in the computer 27, the motor driver 2
1 can be biased to rotate the wafer 19 to a desired angular orientation.

Since the eccentricity or deviation of the X-Y position from the center was also calculated by the computer 27, this information
Wafer 1 is supplied to the stage and positioned.
When the 9 is transferred, bring it to the center. As previously mentioned - the use of an optical sensor 25 capable of capturing the wafer edge over a wide range of eccentricity eliminates the need for a complete A pre-wafer alignment device IO is provided. Since in a typical system the wafer 19 is transferred to the wafer pre-aligner 1o at an unknown angle and up to 1.77 cIn off-center, the present invention provides accurate angular positioning of the wafer without centering the wafer first. Provides a method for aligning.

FIG. 2 illustrates signals obtained from line scanning of the wafer 19 by the optical sensor 25.

Curve A represents the optical sensor 25 obtained from the wafer 19 with the wafer 19 accurately moved to the center of the shaft 13, that is, with no eccentricity and without any concave or convex portions.
shows the signal.

On the other hand, curve B represents the signal when the wafer 19 is off-center and has four or four protrusions.

This curve B is nearly sinusoidal, and the amplitude at various points along the curve B represents the eccentricity or off-centering of the wafer 19 at various angles as the wafer 19 is rotated. The deviation S in this signal indicates the position of the depression or protrusion in the wafer 19 and thus its angular orientation.

The value Q on curve B indicates the corner position of the four parts or convex parts. D
is a guideline for the diameter of the wafer 19. E is wafer 19
A is a measure of the eccentricity of , and S is a measure of the depth of the quadrant or ridge, which together with the diameter determines the width of the quadrant or ridge. It can thus be seen that the signal from optical sensor 25 provides sufficient information to determine the angular position of wafer 19. Since the desired position of the wafer 19 is also known, the wafer 19 can be easily positioned to the desired angular position.

Since the signal from the optical sensor 25 also includes the deviation of the wafer 19 from the center, this information is used to preposition the X-Y stage into which the wafer 19 will be transferred so that it is centered when the wafer 19 is transferred. can be done.

As is clear from the above description, various modifications are possible within the scope of the claims.

[Effects of the Invention] According to the present invention, there is an advantage that it is not necessary to position the wafer in the X-Y directions before centering the wafer, that is, determining the angular orientation.

[Brief explanation of drawings]

FIG. 1 is a partial block diagram schematic diagram of an embodiment of the present invention, and FIG. 2 is a signal waveform diagram useful for understanding the operation of the present invention. 10... Wafer pre-alignment device, 11... Shaft.
Assembly, 13... shaft, 15... cup-shaped element of shaft, 16 and 17... conduit, 18...
...Tube, 19...Wafer, 20...Surge motor, 21...Motor driver, 24...Light source,
25... Optical sensor. υ−HO2e

Claims (1)

[Claims] 1. A wafer pre-alignment device for angularly orienting a wafer according to a desired reference position, comprising: a shaft means; and a wafer tightly attached to one end of the shaft means; a first means for rotating the shaft means; a photosensor means disposed on one side of the wafer; and a photosensor means disposed on the other side of the wafer for detecting an edge shadow of the wafer. a light source for projecting onto said photosensor means, said photosensor means having a linear dimension long enough to capture said edge shadow over a wide eccentricity range, and said photosensor means has a linear dimension long enough to capture said edge shadow over a wide range of eccentricity, and A wafer pre-alignment device that provides a signal representing the wafer pre-alignment device. 2. The optical sensor means is approximately 2.54CTn (1 inch)
The wafer pre-alignment system of claim 1, wherein the wafer pre-alignment device is a charge coupled device array having a linear dimension of . 3. A charge-coupled device array has approximately 10,
3. The wave pre-alignment device according to claim 2, comprising 1,000 photodetecting elements. A charge-coupled device array is positioned relative to the light source and the edge of the wafer to capture the shadow of the edge of the wafer when the wafer is approximately 0.5 inches off center of the shaft means. A wafer pre-alignment device according to claim 3. 5. The wafer pre-aligning apparatus according to claim 4, wherein the first means is a vacuum forming means located at one end of the shaft means for tightly attaching the wafer to the shaft means. 6. The wafer pre-aligning apparatus according to claim 5, wherein the second means is a motor means located at the other end of the shaft means and for rotating the shaft means. 7. The wafer pre-alignment device 8 as claimed in claim 6, wherein the shaft means has resolver means disposed at the other end for providing a signal representative of the angular position of the shaft means in predetermined increments.A charge-coupled device. 8. The way pre-alignment apparatus of claim 7 further comprising third means connected to the array for providing a digital output of the signal from the charge coupled device play. 9. computer means connected to the resolver means and to the shaft means for calculating the eccentricity and angular position of the wafer during one complete rotation of said shaft means; and connected between said computer means and motor means for directing said wafer to the desired 9. The wafer pre-alignment apparatus according to claim 8, further comprising motor driver means for positioning the wafer to a reference position.