Process Optimization For F Crystal Defect On The Al Pad Surface

This paper firstly introduces semiconductor process flow, then introduces the definition and impact of the pad crystal defect, which is from wafer manufacturing process and will impact the reliability of package.To solve the problem, we analyze Al pad process flow and study current lesson learn. Finally, we get the theory of reducing crystal defect, which is decreasing fluorine concentration of the pad surface.Many experiments are designed to verify those ideas about decreasing fluorine concentration, including Asher process time optimization, wet process time optimization, Asher process temperature optimization, argon plasma sputtering and double Asher process.Finally, we get there effective methods to decreasing fluorine concentration, which are extending wet process time, low temperature Asher and argon plasma sputtering process.According to the experiment result, we use 60 minutes wet process to replace the 40 minutes wet process in manufacturing. This action make Al pad crystal defect reduce from about 300 pieces per month to nearly 0. argon sputtering is not used due to potential risk concern. Low temperature Asher is also not used for no need, because the new wet process is effective.