For GaInAs/InP junction field effect transistors as well as heterojunction bipolar transistors, the achievement of very low resistivity P type ohmic contact is a very critical step because the Schottky barrier height on these materials is quite high. The realization of a highly doped P+ layer by Zn diffusion in a semi-closed box and the use of MnAu alloy contact have allowed to solve these difficulties : in fact, a contact resistivity as low as 10-7 Ω cm2 has been obtained
Articles you may be interested inLow damage and low surface roughness GaInP etching in Cl 2 / Ar electron cyclotron resonance process Plasma etch-back planarization coupled to chemical mechanical polishing for sub 0.18 μm shallow trench isolation technology Low damage dry etching of III-V materials for heterojunction bipolar transistor applications using a chlorinated inductively coupled plasma We report on two new self-aligned processes intended for microelectronic devices realization exhibiting a significant reduction of the number of elementary technological levels. These processes allow to obtain a very short self-aligned contact separation without using spacers or wet etched mesa overhangs. As an example, only three lithographic masks are used to realize a triple mesa self-aligned heterojunction bipolar transistor ͑HBT͒. A bilayer resist process is used to define the specific shape of the upper contact that is used for self-alignment. A combination of selective, isotropic, or anisotropic processes and very simple selective lift-off processes are used to define the mesa and the contacts which are also used as masks during etching. The alloying of contacts may be performed just after deposition and lift-off. These processes can reduce the production cost and increase the reliability for integration in comparison with conventional self-alignment using the selective wet etched emitter overhang in the HBT application. Furthermore, the parasitic access resistance can be reduced both by using thin mesa active layers and decreasing the contacts separation. This separation length can be determined by the aspect ratio of the bilayer resist, the characteristics, and parameters of the contact deposition equipment. At last, low induced damage inductively coupled plasma dry etch processes are partly used to reduce the dry etch damages.
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