Delamination of Temporary Bonded Wafers: An Intuitive Study

Advanced packaging technologies (2.5D, 3D) require the thinning of device wafers, down to sub-<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$100\ \mu \mathrm{m}$</tex> in thickness. While using a temporary carrier for that purpose has become a very common approach, such process flow might face some yield concerns. Here, focus will be on the device wafer delamination during the backside (BS) grinding process. A qualitative model has been introduced and, applied to temporary-bonded wafers using Brewer Science's VersaLayer system. The adhesion strength of the laser release layer to the Backside End-Of-Line (BEOL) stack, under the loading conditions of the grinding process, has been identified, together with wafer warpage, and the target Si thickness, as the main factors weighing on the delamination risk. For fixed grinding conditions, optimizing the BEOL stack (as part of design for manufacturing), or/and improving the adhesion in play are the 2 main options to help addressing the delamination occurrence.