Advanced multilayer interconnect technology for switch ICs using InP HEMTs

Suehiro Sugitani, Kazumi Nishimura, Kiyomitsu Onodera, and Hideki Kamitsuna
NTT Photonics Laboratories, NTT Corporation
3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa, 243-0198 Japan
E-mail:, Tel: +81-462-40-2312
Keywords: BCB, Au, interconnect, switch, InP

An advanced four-level interconnect technology has been developed to make high-impedance ITLs with a low crosstalk in compact switch ICs using InP HEMTs. The interconnect consists of a 2-μm-thick 3rd Au metal layer, 5-μm-thick 4th Au metal layer, and 5-μm-thick BCB insulator layers in addition to the ordinary 1st and 2nd metal layers. This technology has three key features: RIE using O2/CF4 gas to form via-holes with aspect ratio of over 1 in thick BCB film; selective electroplating with low current density to form thick Au layers with good thickness uniformity; and a pad stack structure with a viacontact array to improve the bonding reliability. Measured RF characteristics of TFMS lines indicate the usefulness of this technology in compact switch ICs.
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