Reduction of Platinum Metal Usage in GaAs IC Metallization

 

L. Luu-Henderson, L. Rushing and S. Tiku

Skyworks Solutions, Inc.

2427 W. Hillcrest Dr. Newbury Park, CA. 91320, lam.luu@skyworksinc.com, (805) 480-4339

 

 

Keywords: Platinum, Schottky diodes, Ti/Pt/Au, metallization

 


Abstract

Ti/Pt/Au is a well established metallization scheme for GaAs IC processing that can be used for the first interconnect layer, FET gate layers, and Schottky contact for diodes. The platinum in this structure is utilized for its properties as a barrier against gold diffusion into the semiconductor, which occurs at processing temperatures above 260C. Good Schottky diode behavior must be maintained through high temperature processing as well as the life of the circuits. Conventional industry practice for the evaporated Pt layer thickness is to use around 400. However, due to the recent rise in the cost of precious metals, it has become important to optimize the thickness of this Pt barrier layer, without jeopardizing device performance and reliability. This paper explores the effect of varying Pt thickness between 0 and 400 on the electrical stability of Schottky diodes through extended testing at high temperature. Results are encouraging showing that a reduction of Pt may be possible. Reliability testing will continue to further verify the optimum thickness.

 

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