Reducing Broken Thinned GaAs Wafers During Backside Processing

Fadi Bahouth et al
RFMD, 7628 Thorndike Road, Greensboro, NC 27409
Email: fbahouth@rfmd.com Telephone: (336) 678-8005

Keywords: Broken wafers, backside processing, thin wafers

Abstract
Because of the GaAs crystallographic structure, it seems that broken wafers are a fact of life in GaAs fabs. Whether these broken wafers are scrapped or shipped, they represent lost revenue to the company and a headache to the assembly houses that have to deal with them.

A team was assembled at RFMD to investigate, understand, and reduce the number of broken wafers after all backside processing has been completed. A number of factors across all backside operations were found to contribute to wafer breakage. Some factors were fairly obvious such as final wafer thickness, the rest required more effort to uncover and understand. Some of the important factors include the final glassivation dielectric thickness, bonding medium thickness, composition of the post-thin stress relief etch solution, gold plating fixture design, and others.

As a result of these efforts, we were successful in steadily reducing the level of broken wafers to a more tolerable level. Efforts must continue to maintain the present gains, and find additional solutions to continue the downward trend.

Paper 9a.4.pdf