US Patent No. 9,142,626

STEPPED FIELD PLATE WIDE BANDGAP FIELD-EFFECT TRANSISTOR AND METHOD


Patent No. 9,142,626
Issue Date September 22, 2015
Title Stepped Field Plate Wide Bandgap Field-effect Transistor And Method
Inventorship Andrea Corrion, Oak Park, CA (US)
Keisuke Shinohara, Thousand Oaks, CA (US)
Miroslav Micovic, Thousand Oaks, CA (US)
Rongming Chu, Newbury Park, CA (US)
David F. Brown, Woodland Hills, CA (US)
Alexandros D. Margomenos, Pasadena, CA (US)
Shawn D. Burnham, Oxnard, CA (US)
Assignee HRL Laboratories, LLC, Malibu, CA (US)

Claim of US Patent No. 9,142,626

1. A method of making a stepped field-plate gate field effect transistor comprising:
forming a first passivation layer on a barrier layer;
defining a first field plate by using electron beam lithography and by depositing a first negative electron beam resist;
forming a second passivation layer over the first negative electron beam resist and the first passivation layer;
planarizing the first negative electron beam resist and the second passivation layer;
defining a second field plate by using electron beam lithography and by depositing a second negative electron beam resist,
the second negative electron beam resist connected to the first negative electron beam resist;

forming a third passivation layer over the second negative electron beam resist and the second passivation layer;
planarizing the second negative electron beam resist and the third passivation layer;
removing the first negative electron beam resist and the second negative electron beam resist; and
forming a stepped field gate by using lithography and plating, the stepped field gate having the first and second field plates
filling a void left by the removed first and second negative electron beam resists and having a third field plate connected
to the second field plate and extending over the third passivation layer;

wherein the first, second, and third field plates are one structure.