JPS58210633A - Automatic wafer positioning apparatus - Google Patents

Abstract

PURPOSE:To realize automatic positioning with less influence of error in roundness of wafer itself without changing the sensor position in accordance with a size of wafer and any mechanical contact by providing a plurality of light sources and light sensors and by determining positioning operation in accordance with an electrical signal obtained in accordance with the difference of light detected by light sensors. CONSTITUTION:The light emitted from the light source 41 is detected by the light sensors 42, 43, an electrical signal obtained in accordance with difference of light is amplified by a differential amplifier 44 and is recognized as generation of signal 45 to be used actually. This signal is an analog signal but it is converted to a digital signal by the threshold circuit 46. The stop position 48 of orientation flat can be set by processing this digital signal 47. A number of pulses of stepping motor can be set 49 utilizing relation between a number of pulses obtaind by signal processing 47 and a rotating angle and thereby the orieintation flat of wafer can be positioned freely. Following the above processes, automatic positioning of wafer is completed 50.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic wafer alignment apparatus.

In general, there are two methods for automatic wafer alignment: a contact type and a non-contact type, and as shown in Figures 1 and 2, alignment using rollers and alignment using a photo sensor are listed as typical examples. It will be done.

In the case of positioning using rollers, as shown in Figure 1,
It uses three rotating rollers, and rotates when the circle is in contact with the roller, and stops at the flat part of the oriental scene. In the case of positioning using a photosensor, as shown in FIG. 2, the wafer positioning is determined by on-off signals of the photosensor accompanying the rotational movement of the wafer during orientation.

However, in positioning using contact rollers,
Mechanical problems such as wafer damage and scratches must be taken into consideration. Furthermore, positioning using a non-contact photo sensor has the disadvantage that the position of the precision positioning diode shown in FIG. 2(C) must be changed depending on the size of the various wafers. Further, there is a possibility that an erroneous signal is added to the on-off signal of the photosensor due to an error in the roundness of the wafer due to the shape of the wafer.

In order to achieve this purpose, the automatic wafer alignment method of the present invention includes a plurality of light emitting parts and light receiving elements on both sides of the wafer, and based on electrical signals generated by the difference in light intensity of the light receiving elements, It is characterized by operating and determining the alignment of various wafers without changing the position of the light receiving element whose length and width are set in advance for each type of wafer.Examples will be described in detail below. .

FIG. 3 is a diagram of an embodiment of the present invention, showing a part for automatically aligning a wafer, in which 31 is a light emitting section, 32 and 33 are light receiving elements, 34 is a stepping motor, and 35 is a wafer. Light from the light emitting section 31 is sensed by the light receiving elements 32 and 33, and the amount of light received by the light receiving elements 32 and 33 changes depending on the position of the orientation flat.

Here, the light-receiving The light-receiving element has a length that allows the straight portion to cross the light-receiving element, and a width that is sufficiently narrower than 1/2 the length of the orientation flat.

FIG. 4 is a block diagram of an embodiment of the present invention. The light from the light emitting section 41 is sensed by the light receiving elements 42 and 43, and the electrical signal due to the difference in light amount is amplified by the differential amplifier 44.
It is recognized as a signal generation 45 that is actually used. Although this stroke signal is an analog signal, it is converted into a digital signal by the threshold circuit 46. When this digital signal is subjected to signal processing 47, it is possible to set the stop position 4β of the orientation flat. Stepping motor pulse number setting 49 is determined by the signal processing 47 described above.
Using the relationship between the number of pulses and the rotation angle obtained from the above, it is possible to arbitrarily determine the position of the wafer orientation flat. The above process leads to the completion of automatic wafer alignment 50.

FIG. 5 specifically illustrates the signal processing 47 in FIG. 4, and the periods from point a to point C and from point d to point f are as follows:
The orientation flat causes a difference in the amount of light received between the light receiving elements, and an electrical signal is generated through the differential amplifier 44.

Points and points e are based on the orientation flat,
This is where a commercial amount of light hits between the light receiving elements.

The period from point C to point d is a period during which the portion other than the orientation flat, ie, the periphery of the circular arc of the wafer, extends over both light receiving elements. Waveform 1 is converted to waveform 2 through a 1, m2 value threshold circuit. Waveform 1
The waveform fluctuations seen in the wafer are mainly due to errors in the roundness of the wafer itself, but the influence of this roundness error can be reduced by performing an A/D conversion operation. Furthermore, by measuring the time and number of pulses from point g to point i or from point 1 to point 1, the degree of arc for one pulse of the stepping motor can be determined. From these measurements, it was possible to set the stop position of the orientation flat 48, set the number of pulses of the stepping motor 49, and complete automatic wafer alignment 50.
becomes possible.

As explained above, the present invention can be applied to a wafer without changing the position of the sensor depending on the size of the wafer, without mechanical contact with the wafer, and with less influence of errors on the roundness of the wafer itself. This is an automatic alignment device.

[Brief explanation of the drawing]

FIG. 1 is a diagram of wafer alignment using rollers. ra) is being aligned! D, (b) is a diagram showing the completion of alignment. FIG. 2 is a diagram of wafer alignment using a photosensor. 3(a) and 3(b) are six-dimensional diagrams of the automatic wafer positioning portion of the embodiment of the present invention, and FIG. 4 is a block diagram of the embodiment of the present invention. 5(a) and 5(tb) are diagrams specifically showing the A-D conversion of the waveform from the signal generation 45 to the signal processing 47 in FIG. 4. 21... Diode, 31... Light emitting part, 32° 33... Light receiving element, 34...
Stepping motor, 35...wafer. (c>(#ll
]Yaku Isen, 32. J, 3 Mulberry 3 Figure

Claims (1)

[Claims] In Zheng Eva's automatic alignment system, which detects the orientation scene flat of the wafer by arranging a plurality of pairs of light emitters and light receiving elements on both sides of the wafer, the orientation plane flat is vertically divided into two equal parts. The sensor is installed at a symmetrical position with respect to a line that Oriental scene flat 1/
Equipped with a light-receiving element that has a sufficiently narrow width and length,
a differential amplifier that converts a difference in light intensity between the plurality of light receiving elements caused by rotation of the wafer into an electrical signal; and a differential amplifier that detects the position of the orientation plane flat based on the output signal of the differential amplifier; An automatic wafer positioning device characterized by comprising a control circuit for determining a stop position of an orientation sheet flat.