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Improved Thermo Mechanical Mask Evaporation Process

IP.com Disclosure Number: IPCOM000040379D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Greer, SE: AUTHOR [+2]

Abstract

Two new techniques are reported for improving the quality of evaporated metallurgy by controlling the heat imparted to a metal mask during the evaporation process. The high temperature measured at the mask/wafer interface during deposition causes mask bowing and shifting. This results in a yield loss due to misalignment of the metal deposited on the wafer. To avoid high mask temperatures, a high temperature polyimide film material patterned to match the metal mask is aligned over and placed in contact with the mask so as to intercept evaporant that would normally strike the metal mask directly. The thin insulator facing film keeps the metal mask cooler, is patterned using standard photolithographic techniques and reduces the deleterious thermo mechanical effects on the mask.

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Improved Thermo Mechanical Mask Evaporation Process

Two new techniques are reported for improving the quality of evaporated metallurgy by controlling the heat imparted to a metal mask during the evaporation process. The high temperature measured at the mask/wafer interface during deposition causes mask bowing and shifting. This results in a yield loss due to misalignment of the metal deposited on the wafer. To avoid high mask temperatures, a high temperature polyimide film material patterned to match the metal mask is aligned over and placed in contact with the mask so as to intercept evaporant that would normally strike the metal mask directly. The thin insulator facing film keeps the metal mask cooler, is patterned using standard photolithographic techniques and reduces the deleterious thermo mechanical effects on the mask. A film pattern is made slightly larger than a mating mask pattern to accommodate film expansion during deposition. The film facing mask is a throw-away item and saves the cost of cleaning and stripping. Because less material is deposited on the metal mask, cleaning is less expensive. The insulating film, marketed under the name of KAPTON*, is available in sheet form. Some applications utilize KAPTON bonded to a thin film of copper which is also being marketed. A second technique for controlling heat build-up in a metal mask during evaporation is through the alteration of the metal mask clamping fixture 10, shown in Fig. 1, which is used to h...