Submicrometer self-aligned AlGaAs/GaAs heterojunction bipolartransistor process suitable for digital applications |
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Authors: | Lee W-S Enoki T Yamahata S Matsuoka Y Ishibashi T |
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Affiliation: | NTT LSI Lab., Kanagawa; |
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Abstract: | A self-aligned process is developed to obtain submicrometer high-performance AlGaAs/GaAs heterojunction bipolar transistors (HBTs) which can maintain a high current gain for emitter sizes on the order of 1 μm2. The major features of the process are incorporation of an AlGaAs surface passivation structure around the entire emitter-base junction periphery to reduce surface recombination and reliable removal of base metal (Ti/W) deposits from the sidewall by electron cyclotron resonance (ECR) plasma deposition of oxide and ECR plasma etching by NF3. A DC current gain of more than 30 can be obtained for HBTs with an emitter-base junction area of 0.5×2 μm2 at submilliampere collector currents. The maximum fT and fmax obtained from a 0.5×2 μm2 emitter HBT are 46 and 42 GHz, respectively at IC=1.5 and more than 20 GHz even at IC=0.1 mA |
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