An Application of Air-Bridge Metal Interconnections to High Speed GaAs LSI's

Minoru NODA  Hiroshi MATSUOKA  Norio HIGASHISAKA  Masaaki SHIMADA  Hiroshi MAKINO  Shuichi MATSUE  Yasuo MITSUI  Kazuo NISHITANI  Akiharu TADA  

IEICE TRANSACTIONS on Electronics   Vol.E75-C    No.10    pp.1146-1153
Publication Date: 1992/10/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Compound Semiconductor Integrated Circuits)
air-bridge,  interconnection,  propagation delay time,  GaAs LSI,  

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Air-bridge metal interconnection technology is used for upper level power supply line interconnections in GaAs LSI's to reduce the signal propagation delay time. This technology reduces both parasitic capacitance between the signal line and the power supply line, and propagation delay in the signal line to about 10% and about 50%, respectively, compared to conventional 3-level interconnections without air-bridges. Under standard load conditions (FI=FO=2, length of load line=2 mm), the air-bridge technique leads to gate propagation delays which are about 60% of those in conventional interconnections. We fabricated 2.1-k gate Gate Arrays and 4-kb SRAM's using the air-bridge structure to interconnect power supply lines. For a Gate Array with 0.7 µm gate Buried P-layer Lightly Doped Drain (BPLDD) FET's, the typical gate propagation delay under standard load conditions was about 110 ps with a dissipation power of 1.4 mW/gate. SRAM's with 05 µm gate BPLDD's had typical access time (tacc) of 1.5 ns with a dissipation power of 700 mW/chip.