Cavity structure GaAs FETs with high humidity resistance


Yasuki Aihara1, Toshiaki Kitano1, Kazuyo Endo2, Kenji Hosogi1, Hiroshi Fukumoto2

1High Frequency & Optical Device Works, Mitsubishi Electric Corporation,

4-1, Mizuhara, Itami, Hyogo, 664-8641, Japan

2Advanced Technology R&D Center, Mitsubishi Electric Corporation,

8-1-1 Tsukaguchi-honmachi, Amagasaki, Hyogo, 661-8661, Japan



Keywords: Cavity, humidity resistance, HAST, SAM



We have developed new cavity structure GaAs FETs with high humidity resistance. The cavity is formed by sealing up with air bridges and polymers around the FETs and covering the surface of the polymers with thick SiN films. As the cavities formed by the newly-developed process are completely airfilled, the high frequency characteristics of FETs are unaffected by the parasitic capacitances of the polymer films and the thick SiN films. Highly reliable DC operation of the cavity FETs is demonstrated for more than 96 hrs under Ta = 130_C, RH = 85% and Vdg = 11 V.




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