Browse Prior Art Database

Fixture Design to Reduce Metal Mask Silicon Wafer Thermal Mismatch Effects

IP.com Disclosure Number: IPCOM000087081D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Benjamin, CE: AUTHOR

Abstract

This tooling reduces the misalignment problems inherent in heated-substrate metal-masked evaporation of semiconductor device wafer thin-film patterns by up to a factor of 2 over previous designs. It is a technique for constraining the clamped silicon wafer and metal evaporation mask to expand thermally only in a radial direction, without obscuring any mask or wafer active areas.

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Fixture Design to Reduce Metal Mask Silicon Wafer Thermal Mismatch Effects

This tooling reduces the misalignment problems inherent in heated-substrate metal-masked evaporation of semiconductor device wafer thin-film patterns by up to a factor of 2 over previous designs. It is a technique for constraining the clamped silicon wafer and metal evaporation mask to expand thermally only in a radial direction, without obscuring any mask or wafer active areas.

This technique forces the mask and spring to expand only radially. Three pins and oblong slots in both the mask and spring are used. They are roughly equally spaced (about 120 degrees apart) around the circle. If such spacings are uneven, this will assist in proper mask positioning, but no pair should be diametrically opposed. The long axes of the slots are radial, so that expansion of the mask and spring exert forces against the sides of the slots, making any movement only radial, with the centers effectively fixed with respect to the tooling. The peripheries of both the mask and spring "float" vertically and are horizontally constrained only by the pins in the radial slots, effectively tying the center of the wafer to the center of the tooling also, and permitting unconstrained radial expansion (at different rates) of all parts. The base makes contact with the top ring outside the peripheries of the mask, wafer, and spring so that the mask is only pressed against the bottom surface of the top ring by pressure (through the wafer) from the leaf spring.

The net result of constraining the centers of the mask and wafer together is that the maximum thermal mismatch during a hot-substrate evaporation will be only half that which exists when the mask and wafer are constrained at a point on (or nea...