Reduction of Platinum Metal Usage in GaAs IC Metallization
Skyworks Solutions, Inc.
Hillcrest Dr. Newbury Park, CA. 91320, firstname.lastname@example.org,
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 260°C. 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 400Å. 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 400Å 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.