Polyimide passivation of GaAs microwave monolithic integrated ci

Details Polyimide passivation of GaAs microwave monolithic integrated ci Polyimide passivation of GaAs microwave monolithic integrated ci

1994-10-04

1996-03-26

Fourson, George

Fishing, trapping, and vermin destroying

437184, 437192, H01L 21283, H01L 2156

Patent

active

055020020

ABSTRACT:
A process is provided for passivating surfaces (12') of III-V microwave monolithic integrated circuit (MMIC) flip chips (40). Essentially, two cured, patterned polyimide layers (10, 28) are applied, one on the chip surface supporting a gold-plated bridge (26) and passivating the surface and the other over the gold-plated bridge to passivate the bridge surface. Further, a silver-titanium composite layer (32) is deposited over a gold-plated bump-post (24), which is then covered by a silver-plated bump (38), in order to prevent scavenging of gold from the bump-post by a subsequent Pb-Sn reflow solder process used to mount the chip to a metallized ceramic substrate. The process of the invention facilitates a more compatible reflow solder silk-screening process with passivated III-V MMIC flip chips, resulting in a more uniform and consistent solder thickness and relieving a tight tolerance requirement on the plated silver bump height uniformity.

REFERENCES:
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patent: 4305974 (1981-12-01), Abe et al.
patent: 4459321 (1984-07-01), Kim
patent: 4859633 (1989-08-01), Bayraktaroglu
patent: 4916503 (1990-04-01), Uematsu et al.
patent: 5104820 (1992-04-01), Go et al.
patent: 5179041 (1993-01-01), Yano et al.

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