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Making reliable through-die interconnects for three-dimensional (3-D) wafer stacking technologies requires a reduction in wafer thickness combined with a larger wafer diameter, which in turn requires new methods for wafer handling. Of the different wafer-level bonding techniques, temporary wafer bonding adhesives are becoming increasingly important in both integrated circuit and MEMS technologies. This new generation of adhesives must possess a variety of properties to be integrated into all the required processes, including adequate flow properties, mechanical strength, thermal stability, chemical resistance, and easy debonding and cleaning. The purpose of this paper is to demonstrate that, contrary to the tapes and waxes currently used for temporary bonding, a new removable high-temperature adhesive* meets all the requirements named above for reliable through-silicon via (TSV) processing on 8-inch wafers. After a presentation of the typical temporary wafer bonding process flow, the article will describe the development and the properties of the material. Secondly it will present the TSVs formed in a 70-mum thinned silicon wafer using the temporary bonding process.
Date of Conference: 9-12 Dec. 2008