A Novel Process to Reduce the Warpage of Bond Pair for Temporary Bonding and De-bonding Technique

For temporary bonding and de-bonding (TBDB) process, a mismatch in coefficients of thermal expansion (CTE) between the carrier wafer and device wafer would produce additional mechanical stress when bonded at high temperature. Large warpage happens which results in the failure for the subsequent backside processes of thinning, chemical mechanical polishing (CMP) and PECVD. In view of these, studies on reducing the warpage of bonding pair are highly required. Herein, an innovative baking process to reduce the warpage is developed, which is firstly confirmed by a commercial thermal sliding material (TBM-1). The warpage shapes of initial wafers and bonding pairs were characterized by using a single line scanned film-stress measurement (FSM). And the results show that after baking at 200 °C for 10 min, the warpage could be greatly reduced from -112.14 μm to -55.18 μm, owing to the elimination of a large number of thermal stresses. However, the warpage variation becomes negligible (-54.61 μm) as the baking time is extended to 20 min. Additionally, this heating treatment process was successfully applied to another two thinner silicon wafer (200 μm and 300 μm) and a similar warpage decreasing behavior was observed or even more significant. More importantly, this heating process was highly suitable as well when it came to another thermal sliding material (TBM-2), showing largely decrease from -110.28 μm to -12.97 μm as baking for 10 minutes and thus proving its generality for reducing warpage comes from high temperature bonding process.