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Browse Prior Art Database

Automatic Edge Location for Pneumatic Orientor

IP.com Disclosure Number: IPCOM000089353D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 4 page(s) / 82K

Publishing Venue

IBM

Related People

Gardineer, BG: AUTHOR [+2]

Abstract

In wafer orientors, such as described in the IBM Technical Disclosure Bulletin, Vol. 17, No. 8, January 1975, pages 2332-2333, the common mode of wafer positioning relies on the notch being located on a standard diameter pin and the wafer subsequently being located by two other points to substantially centralize the wafer about an imaginary line drawn bisecting the notch pin and the two alignment points.

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Automatic Edge Location for Pneumatic Orientor

In wafer orientors, such as described in the IBM Technical Disclosure Bulletin, Vol. 17, No. 8, January 1975, pages 2332-2333, the common mode of wafer positioning relies on the notch being located on a standard diameter pin and the wafer subsequently being located by two other points to substantially centralize the wafer about an imaginary line drawn bisecting the notch pin and the two alignment points.

As a result of the standard way of locating a notched wafer, any wafer within tolerance (+/-.020" diameter) can be located by a system of properly located and actuated notch pin and aligning pins on any pin chuck with assurance that features on the wafer are in essentially known positions. That is, they are within perhaps .003" of a "true" position. This allows measurements to be made and serial numbers to be read through "Dead Reckoning" systems that move the aligned wafer on its chuck to a specified position with no visual or other feedback from the wafer itself. This is necessary in any system that is automatically aligned without operator intervention.

A pneumatic orientor with jets located symmetrically about the center will locate varied size wafers about the center point, as shown in Fig. 3.

Such a pneumatic orientor, by virtue of its centralizing means, does not duplicate this positioning and, as a consequence, cannot locate the wafer in an acceptable position. It is readily apparent that a mark on the center line of the wafer, a distance of X units from the notch, will appear on all mechanical chucks at ~ distance of R-X from a theoretical center within the accuracy possible with the chuck and independent of the diameter of the wafer under consideration (R is the wafer radius).

This pneumatic chuck will locate varied size wafers, as shown in Fig. 3, essentially at their exact center. Consequently, only a wafer of nominal diameter will have its mark made on a conventional chuck at the proper location. Wafers of smaller size will have their marks R-X-delta/2 from center where delta represents the amount less than nominal that the diameter of the wafer is undersize (maximum of .020" if the wafer is within tolerance), and wafers of greater than nominal size will have their marks...