IWLPC (Wafer-Level Packaging) Conference Proceedings


Author: Carl R. Kessel et al.
Company: 3M Company
Date Published: 10/10/2004   Conference: IWLPC (Wafer-Level Packaging)

Abstract: A new support system is described for wafer thinning applications in which a final die thickness of less than 100 microns is desired. Thinning to 20 microns has been demonstrated, and bumped wafers can be routinely thinned to a final thickness of less than 50 microns. The integrated system consists of mounting and demounting hardware along with associated consumables and is designed to allow users to backgrind wafers with their existing grinding equipment. Post-grind processes such as etching and polishing are possible, as is dicing before grinding. All wafer sizes through 300 mm are supported, and thinned wafers are output from the demounter on standard dicing tape frames.

The key elements of the support system are a UV curable liquid adhesive and a light-to-heat conversion (LTHC) layer between the glass plate and the adhesive. The liquid adhesive ensures conformity to the front side topography and, after hardening, provides uniform support of the entire wafer area during grinding. Since all areas of the wafer are supported during the grinding process, and the overall compliance of the glass plate-cured adhesive stack is much less than film-based tape systems, wafer cracking is reduced and yields are increased.

The adhesive also protects the wafer edge from chipping and is removed from the wafer surface with residue levels comparable to those seen with conventional backgrinding tapes. The proprietary LTHC layer between the rigid glass support plate and the adhesive allows for removal of the glass plate after grinding.

Key Words: wafer support, backgrinding, thinning, ultrathin, adhesive.

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