倒装焊对探测器频响特性影响的理论分析及工艺优化

Analysis and Optimization of the Frequency Response of Flip-chip Bonded Photodiode

摘要:

针对光探测器在倒装焊过程中频响性能恶化的问题，建立等效电路模型分析出其原因，并通过优化倒装焊工艺条件予以有效解决。该电路模型包括探测器芯片、过渡热沉和倒装焊环节三个部分。基于倒装焊后探测器的S11参数和频响曲线提取出倒装焊环节特征参数，确认焊点接触电阻过大是引起探测器频响下降的主要原因。通过优化倒装焊工艺条件，有效减小了焊点接触电阻，基本消除了倒装焊对探测器频响特性的影响。

Abstract:

Frequency response degeneration of flip-chip bonded photodiodes is analyzed based on an equivalent circuit model and solved by optimizing the flip chip process. The circuit model takes such three parts into consideration as photodiode chip, heat sink and flip-chip bonding. The values of flip-chip bonding induced elements are extracted by fitting the S11 parameters and frequency response curves, and the large bonding contact resistance is verified as the main factor causing the frequency response degradation for flip-chip bonded devices. Therefore, the bonding process conditions are optimized to reduce the contact resistance of the metal bump significantly. As a result, the influence of flip chip bonding on the photodiode frequency response is eliminated.