In-line metrology of 3D interconnect processes

The continuous development of three-dimensional chip/wafer stacking technology has created the metrology requirements for in-line 3D manufacturing processes. This paper summarizes the developing metrology that has been used during via-middle & via-last TSV process development at ITRI (Industrial Technology Research Institute). An IR metrology tool including broadband infrared microscopic imaging module and a specific infrared laser confocal module is developed for the thinned wafers thickness measurement with spatial resolution of 0.5 mu m. An existing spectral reflectometer is used and enhanced by implementing novel theoretical model and measurement algorithm for HDTSV inspection. It is capable of measuring via depth/bottom roughness/bottom profile in one shot measurement. A metrology module based on two sets of dual-channel capacitive sensors for metallization film thickness measurement is applied to make critical process control in the fab. We will share real metrology results and discuss possible solutions for 3D interconnect processing.