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Lift Off Process for Hot Evaporations

IP.com Disclosure Number: IPCOM000086236D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Johnson, C: AUTHOR [+2]

Abstract

A double-layered lift-off structure is formed by successively depositing two refractory layers on a substrate. For example, a layer of molybdenum is deposited on a substrate such as thermal oxide and a layer of pyrolytic oxide is placed on top of the molybdenum.

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Lift Off Process for Hot Evaporations

A double-layered lift-off structure is formed by successively depositing two refractory layers on a substrate. For example, a layer of molybdenum is deposited on a substrate such as thermal oxide and a layer of pyrolytic oxide is placed on top of the molybdenum.

A desired pattern is formed on the pyro oxide using conventional photolithographic techniques and the resist material is stripped. Using the patterned pyro oxide as a mask, the molybdenum is then etched down to the substrate, at the same time undercutting the patterned pyro oxide and forming the desired lift-off structure. 5:1 buffered HF is suitable for patterning the pyro oxide, while standard phosphoric-nitric-aluminum etch is suitable for etching the molybdenum.

The material to be lifted off, such as polycrystalline silicon, is evaporated on the windowed pyro oxide. Substrate temperatures in excess of 600 degrees C during evaporation are withstood by the lift-off structure. Lift-off action is achieved in an aluminum etch which etches only the molybdenum, leaving the desired polysilicon pattern and the thermal oxide substrate intact.

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