Browse Prior Art Database

Wafer Angular Alignment Detection and Positioning System

IP.com Disclosure Number: IPCOM000076650D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 4 page(s) / 54K

Publishing Venue

IBM

Related People

Jorgensen, RR: AUTHOR [+3]

Abstract

The system as shown, for semiconductor wafer handling, is formed of two basic subcombinations, e.g. a rough alignment and transfer system, and a means for detecting angular alignment and positioning of a substrate. The system is directed to handling of semiconductor wafers 1, as shown in Fig. 2.

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Wafer Angular Alignment Detection and Positioning System

The system as shown, for semiconductor wafer handling, is formed of two basic subcombinations, e.g. a rough alignment and transfer system, and a means for detecting angular alignment and positioning of a substrate. The system is directed to handling of semiconductor wafers 1, as shown in Fig. 2.

The rough alignment and transfer system is shown in Figs. 1 A & 1 B. The mechanical self-centering mechanism and wafer transfer system is comprised of the following elements:

An upstream air slide 2 for conveying a semiconductor wafer 1 to a centering cone 3; downstream airslide 4 for conveying rejected wafers; centering cone 1 to stop, receive and lower wafers for centering (cone 3 also acts as a plenum for down-stream blow-off of wafers and has the facility to contain a light source 5 for periphery degradation and/or operation initialization sensing by a detector 6); a rotating substage 7 to chuck a wafer and impart rotary motion thereto; a spindle 8 to supply positive or negative pressure to the substage 7 to key and guide cone 3, to provide bearing contact for substage 7 and impart concentric alignment between cone 3 and substage 7; a printed-circuit servomotor 9 for imparting rotary motion to substage 7 during centering operation and provide instantaneous stopping of the substage during angular alignment operation; and a transfer system which includes an access arm 10 with vacuum pick-up provision for picking up wafer 1 to remove it from the system and transfer it to other processing stages.

The key mechanical element in the alignment system is the conical selficentering mechanism, as illustrated in Fig. 1A. In this system, wafer 1 is driven to the cone 3 via the air slide 2. Once the wafer is within cone 3, the cone is lowered to the substage 7 which, during this operation, is rotating and is under negative pressure (vacuum) 11. The relative effects of substage rotation, vacuum pull-down, and the lowering of the wafer, while contained within the cone, causes a tangential tracking action and downward component, which results in nesting the wafer to its theoretical center (cone concentric to substage spindle with minimum run out). Once the wafer makes contact with substage 7, the vacuum holds it securely in place. Wafer 1, which is still rotating, can now be operated under computer control if desired. Operations such as periphery degradation checking for missing alignment patterns, wafer identification of machine readable code for mask selection and process control, and angular rough alignment can be readily accommodated using this system. The wafer, if accepted, is transferred from the system via the access arm 10. If rejected, the wafer is blown off down-stream via the air slide 4.

The alignment system of Fig. 2 is comprised of the following key elements:

A rotating substage 7 which chucks wafer 1 and is driven by a low-inertia servomotor 9. In this system there has been an ini...