| 摘要 |
PURPOSE: A fabrication method of HBT(heterojunction bipolar transistor) is provided to improve an emitter ohmic contact property and simplify the manufacturing process. CONSTITUTION: An HBT fabrication method comprises the following steps. An HBT epitaxial substrate sequentially formed a semiconductor(1), a buffer layer(2), a sub-collector(3), a collector(4), a base(5), an emitter(6), and emitter cap layers(7,8) is prepared by conventional processes. By using double mask layers(9,10) having different etching selectivity, surface protrusion patterns are formed on the HBT epitaxial substrate. The lower mask layer(9) made of a photoresist layer, and the upper mask layer(10) composed of a silicon nitride. Thereby, the surface protrusion pattern has s reverse T-shaped structure due to differency of etching selectivity. Using the surface protrusion pattern having reverse T-shaped structure, an emitter ohmic electrode is formed.
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