Progress Towards a Micromachined Thermoelectric Generator using PbTe and PbSnSeTe Thin Films

摘要

This paper presents etching techniques and metal contact resistance studies for vapor-deposited PbTe and PbSnSeTe films to enable micromachining of thermoelectric (TE) generators within integrated MEMS devices (e.g. micro heat engines, microcombustors). Films of up to 10 micrometers were achieved using (100) silicon substrates. Single-crystal films were achieved using CdTe or ZnTe buffer layers, while polycrystalline films were formed on thermally-oxidized silicon. Processes using a bromine-based wet etch and methane-based ICP plasma etch yielded etch rates of 3 micrometer/min and 0.65 micrometers/min, respectively, with high selectivities (>10:1) to photoresist, silicon and SiO2. Electrical resistivity (van der Pauw) and metal contact resistance (transfer length method) test structures were used to characterize patterned PbTe and PbSnSeTe films and the contact resistance with a variety of metals (Au/Cr, Au, Pt, Ni, Cu, Pt). Film resistivities of 5-300 m(omega)-cm and ohmic contacts with specific contact resistivities of 0.4-40 m(omega)-sq cm were achieved.