Study on reflow process of SWIR FPA during flip-chip bonding technology

Abstract

Reflow soldering is the primary method for Flip-chip bonding without high bonding pressure. Reflow process during flip-chip technology in short wavelength infrared (SWIR) InGaAs/InP Focal Plane array (FPA) with indium solder was studied in this paper. In order to analyze the formation of Indium oxide and its effects on Indium bump reflow process. Indium bumps were investigated by X-ray Photoelectron Spectroscopy (XPS). The profiles of Indium bumps after reflow were observed by scanning electron microscopy (SEM). The interaction between Indium and the metal in under bump metallization (UBM) during reflow process was discussed. The current–voltage (I–V) curves of InGaAs/InP photodiodes were measured before and after the reflow process. The dark current density at 0.1 V reverse bias of InGaAs/InP photodiodes were studied. It was confirmed that the characteristics of InGaAs photodetectors haven’t degenerated after reflow in this paper.