How to select adhesive materials for temporary bonding and de-bonding of 200mm and 300mm thin-wafer handling for 3D IC integration?

Handling and shipping thin wafers (≤200μm) through all the semiconductor fabrication and packaging assembly processes are very difficult since thin wafers lose the supporting strength. Usually, the thin wafer is attached to a supporting wafer with adhesive to increase its rigidity and bending stiffness. Thus, adhesive is the key enabling material for thin-wafer handling, and how to select adhesive materials for temporary bonding and de-bonding is the focus in this study. Two sizes of wafers are considered; the 200mm wafers are used to find out the important and unimportant parameters in selecting the adhesive and then apply them to the 300mm wafers. It will be shown that wafer thinning and PECVD (plasma enhanced chemical vapor deposition) in vacuum chamber are the two critical steps for thin-wafer handling. The 300mm wafers are thinned down to 50μm and evaluated in different structures including: (a) blanket wafers, (b) wafers with 80μm solder bumps, and (c) wafers with 20μm micro-bumps and TSVs in 10μm diameter and 40~50μm pitch. Based on this study, a set of useful process guidelines and recommendations is provided.