Effect of Different Defects in Temporary Bonding on Laser Debonding

Current 3D packaging technologies, such as Package-on-Package, Package-in-Package, Wafer-Level-Package, Through-Silicon-Via, require the use of ultra-thin wafers to increase integration, enhance heat dissipation and electrical performance. To address the warping or damage issues caused by mechanical or thermal stress during the processing of ultra-thin wafers, temporary bonding technology is usually used to temporarily bond the wafers to a rigid substrate for smoothly pass through the demanding back-side processes of such as mechanical grinding, chemical vapor deposition and reflow soldering. However, some defects (adhesive gaps, glass cracks, and snowflakes) occasionally occur in the layer of adhesive material during the wafer bonding process. To date, little has been reported in the literature on how these defects affect UV laser debonding and the possible damage risk to the device wafer. Here, temporary bonding pairs with different defects were debonded using a UV laser and the different morphologies of the photosensitive material after ablation were characterized. Furthermore, we evaluate the ease of cleaning of device wafers with residual adhesive. This work provides technical support and reference for the development of laser debonding processes in the field of advanced packaging of chips.