Analyses of Pinned Photodiodes With High Resistivity Epitaxial Layer for Indirect Time-of-Flight Applications

Abstract

This paper analyzes the performance of pinned photodiode (PPD) for Time-of-Flight(ToF) applications on high resistivity epitaxial wafers. Due to its wide depletion region, high epitaxial resistivity PPDs feature some key advantages in collecting photogenerated charges. This paper compares the demodulation contrast of the same pixel design on epitaxial wafers with different resistivity at near-infrared wavelength to analyze their performance. By comparing the simulated profile of pixels with different epitaxial resistivity, the characteristics of the PPD pixel on high resistivity epitaxial wafer when collecting photogenerated charges are concluded. This paper also discusses the effects of using high resistivity epitaxial wafer with various design parameters. It is found that the use of high resistivity epitaxial wafer can greatly improve crosstalk performance, allow pixels to work at higher modulation frequencies, and enable largesized pixels to have good demodulation capabilities. INDEX TERMSPinned photodiode, time-of-flight, ToF, high resistivity, CMOS image sensor.

Design of a CMOS image sensor pixel with embedded polysilicon nano-grating for near-infrared imaging enhancement

“…To be 27 efficient, NIR detection with silicon needs significantly thicker 28 photosensitive layer than what standard CIS fabrication usually 29 allows. Therefore, some studies have investigated a detector 30 with a thicker active layer in silicon [14,15], making the photo-31 sensitive layer going deeper in the silicon with high resistivity 32 epitaxial layer [16,17] or by applying a negative voltage at the 33 back of the photodiode [12] . Unfortunately, these solutions re- extensively studied [18][19][20][21].…”