Active solid-state devices (e.g. – transistors – solid-state diode – Heterojunction device – Bipolar transistor
Patent
1996-09-30
1999-04-06
Fahmy, Wael
Active solid-state devices (e.g., transistors, solid-state diode
Heterojunction device
Bipolar transistor
257198, 257587, H01L 310328, H01L 310336, H01L 27082
Patent
active
058922482
ABSTRACT:
A heterojunction bipolar transistor and a method for fabricating an HBT with self-aligned base metal contacts using a double photoresist, which requires fewer process steps than known methods, while minimizing damage to the active emitter contact region. In particular, a photoresist is used to form the emitter mesa. The emitter mesa photoresist is left on and a double polymethylmethacrylate (PMMA) and photoresist layer is then applied. The triple photoresist combination is patterned to create a non-critical lateral alignment for the base metal contacts to the emitter mesa, which permits selective base ohmic metal deposition and lift-off. By utilizing the double photoresist as opposed to a metal or dielectric for masking, an additional photolithography step and etching step is eliminated. By eliminating the need for an additional etching step, active regions of the semiconductors are prevented from being exposed to the etching step and possibly damaged.
REFERENCES:
patent: 5219713 (1993-06-01), Robinson
patent: 5412233 (1995-05-01), Dubon-Chevallier et al.
patent: 5472886 (1995-12-01), Dautartas et al.
patent: 5665614 (1997-09-01), Hafizi et al.
Oki Aaron K.
Streit Dwight C.
Tran Liem T.
Umemoto Donald K.
Fahmy Wael
TRW Inc.
Yatsko Michael S.
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