Semiconductor device manufacturing: process – Forming bipolar transistor by formation or alteration of... – Having heterojunction
Patent
1998-05-07
1999-11-30
Fahmy, Wael
Semiconductor device manufacturing: process
Forming bipolar transistor by formation or alteration of...
Having heterojunction
438320, 438321, 438670, 438944, 438951, 148DIG72, 148DIG100, H01L 21331
Patent
active
059941944
ABSTRACT:
A relatively simple method for providing relatively close spacing between the emitter mesa and the base ohmic metal of a heterojunction bipolar transistor (HBT) on a relatively uniform basis. An emitter and base layer are epitaxially grown on a substrate. An emitter mesa is patterned with an i-line negative photoresist using conventional photolithography. Baking before and after exposure is used to form a resist pattern with a re-entrant profile having about a 0.1 .mu.m resist overhang. The emitter layer is then etched with a wet etch and or isotropic dry etch to expose a portion of the base ohmic metal to make contact with the base. A second layer of an i-line negative photoresist is applied over the first photoresist. The second layer is used to pattern the base ohmic metal mask. The base ohmic metal is deposited by evaporation. The resist is stripped from the emitter mesa and the non-base ohmic metal regions which lifts the metal deposited on the resist leaving the metal in the base ohmic metal regions, aligned to the emitter mesa at a uniform spacing.
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Fahmy Wael
Pham Long
TRW Inc.
Yatsko Michael S.
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