Monday, January 02, 2017

TSMC Proposes Pixel with No High Energy Implants

TSMC patent application US20160351604 "Implant damage free image sensor and method of the same" by Alexander Kalnitsky, Jhy-jyi Sze, Dun-nian Yaung, Chen-jong Wang, Yimin Huang, and Yuichiro Yamashita proposes pixel process flow with minimal usage of ion implantation, if at all. Instead, selective and non-selective epi growth, in-situ doping, and diffusion are used extensively:

"Conventional methods of addressing the dark current and cross-talk issues, such as deep trench isolation (DTI), require conducting an implant operation, which is likely to cause damage on the image sensor and is confined by an implant depth limitation. As such, additional defects and interference may be induced. It would therefore be desirable to be able to provide improved image sensor for capturing images.

Compared to an existing process, DTI without the use of high energy implants can reduce the chance of introducing defects to the pinned photodiode structure and allows for the formation of a much deeper P-N junction compared to the one formed by ion implantation. Very deep junction may be beneficial for the near infrared (NIR) sensor.

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