The Effects of Chemical Treatment and Storage Time on the Surface Chemistry of Semi-Insulating Gallium Arsenide

Thomas Mirandi* and Douglas J. Carlson M/A-COM Technology Solutions, A Cobham Company, 100 Chelmsford St., Lowell, MA 01851 carlsond@tycoelectronics.com, thomas@waferworld.com *currently at Wafer World, Inc., 1100 Technology Place, Suite 104, West Palm Beach, FL 33407

Keywords: Semi-insulating gallium arsenide, Monolithic microwave integrated circuits

ABSTRACT

The steps used to prepare semi-insulating Gallium Arsenide (SI-GaAs) surfaces for subsequent processing can have a profound effect on process line yields. This work explores the effect of acid/base treatment and storage time has on the surface chemistry of semi-insulating gallium arsenide. Distinctions are drawn between “freshly-processed” wafer surfaces and substrates prepared and stored over time. Specific points addressed include examination of pre-epi native oxide composition, wettability, and thickness. It is shown that although the oxide thickness increases slightly over time, the chemical bonding of the uppermost surface layers remains in an unstable condition.

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