Although great effort has been made to improve the reliability of thin film structures, the effects of mechanical fatigue on thin film interfaces has thus far been difficult to quantify. Most industrial fatigue testing uses HAST (Highly Accelerated Stress Testing) protocols, which inherently convolute the effects of environment and fatigue. Our work focuses on studying separately the effects of mechanical fatigue and moisture on interface debonding. This study examines polymer interfaces that are of general interest to the microelectronics industry. The model system investigated involves the interface between benzocyclobutene (BCB) and silicon dioxide. BCB has been used in Multichip Modules as a stress buffer and passivation layer. Results are presented that explore the effect of interface chemistry, which was controlled through the addition of selected silane adhesion promoting layers, on macroscopic interface adhesion. THe effect of moisture was studied through static debonding tests performed in controlled environments. Preliminary results indicate that static-mode debonding of the BCB/silica interface is sensitive to moistur econtent. The effect of temperature between 10-50 deg C was seen to be less important on subcritical debonding. Finally, the detrimental action of mechanical fatigue loading on subcritical debond growth was documented. The goal of our work is to develop a methodology for understanding the contribution of both environment and fatigue to interface debonding.
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