METHOD FOR FORMING OHMIC CONTACT LAYER OF HETERO-JUNCTION BIPOLAR TRANSISTOR

摘要

PURPOSE: A method for forming an ohmic contact layer of a hetero-junction bipolar transistor is provided to improve efficiency of a fabricating process and reduce a fabricating cost by forming simultaneously ohmic electrodes on an emitter, a base, and a collector. CONSTITUTION: A buffer layer, a sub-collector layer, a collector layer, a base layer, an emitter layer, and an emitter cap layer are grown on a compound semiconductor substrate. A surface of the base layer is exposed by etching the emitter cap layer and the emitter layer. A surface of the sub-collector layer is exposed by patterning the base layer and the collector layer. An ohmic electrode is formed simultaneously on an emitter region, a base region, and a collector region. A Ti metal layer(8), a Ti nitride metal layer, a compositionally graded tungsten nitride metal layer, and a tungsten metal layer are deposited sequentially on the substrate. A titanium metal layer(8) and a platinum metal layer are formed thereon. An n type emitter and an n type collector ohmic electrode and a p type base ohmic electrode are formed simultaneously by performing an etch process. An isolation region is formed by performing a mesa etch process. A dielectric insulating layer(17) is applied on a whole surface of the above structure. A metal line including the titanium layer and an aurum layer(18) is formed by performing selectively the etch process.