High yield scalable dry etch process for indium based heterojunction bipolar transistors

A dry etch process for fabricating high-performance In-based heterojunction bipolar transistors is described. The 2 mu m*4 mu m emitter was formed by electron cyclotron resonance CH/sub 4//H/sub 2//Ar plasma etch, thus minimizing damage and providing excellent pattern transfer of the emitter metal mask. In order to minimize parasitics and insure high yields, an SiO/sub 2/-filled trench base-mesa is used, under the self-aligned based contact pad, to define the active base area. As a further yield enhancement and to enable eventual submicron scaling of devices, planarization and reactive ion etchback of Futurrex PC2-1500 polymer were performed to expose emitter terminals. Devices with emitter sizes of 2 mu m*4 mu m demonstrated current gains of 50 with f/sub T/ (cutoff frequency) and f/sub max/ (maximum frequency of oscillation) values measured at >80 GHz and >60 GHz, respectively. By employing a two-stage collector structure, V/sub ceo/ in excess of 7 V is realized.<>