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Copper-Based OHMIC Contracts for the Si/SiGe Heterojunction Bipolar Transistor StructureSilicon based heterojunction bipolar transistors (HBT) with SiGe base are potentially important devices for high-speed and high-frequency microelectronics. These devices are particularly attractive as they can be fabricated using standard Si processing technology. However, in order to realize the full potential of devices fabricated in this material system, it is essential to be able to form low resistance ohmic contacts using low thermal budget process steps and have full compatibility with VLSI/ULSI processing. Therefore, a study was conducted in order to better understand the contact formation and to develop optimized low resistance contacts to layers with doping densities corresponding to the p-type SiGe base and n-type Si emitter regions of the HBTS. These as-grown doped layers were implanted with BF(sub 2) up to 1 X 10(exp 16)/CM(exp 2) and As up to 5 x 10(exp 15)/CM2, both at 30 keV for the p-type SiGe base and n-type Si emitter layers, respectively, in order to produce a low sheet resistance surface layer. Standard transfer length method (TLM) contact pads on both p and n type layers were deposited using an e-beam evaporated trilayer structure of Ti/CufTi/Al (25)A/1500A/250A/1000A). The TLM pads were delineated by a photoresist lift-off procedure. These contacts in the as-deposited state were ohmic, with specific contact resistances for the highest implant doses of the order of 10(exp -7) ohm-CM2 and lower.
Document ID
19990111480
Acquisition Source
Glenn Research Center
Document Type
Conference Paper
Authors
Das, Kalyan
(Tuskegee Inst. AL United States)
Hall, Harvey
(Tuskegee Inst. AL United States)
Date Acquired
August 19, 2013
Publication Date
August 1, 1999
Publication Information
Publication: HBCUs/OMUs Research Conference Agenda and Abstracts
Subject Category
Electronics And Electrical Engineering
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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