Sunday, May 24, 2020

4 Generations of Tower GS Pixels

Tower Semiconductor posts an article on its global shutter pixels development:
  • Gen 1: Our first generation of GS pixels went into production with relatively big (around ~5um) size, about ~20e of noise and a decoupling ratio between PD and MN of around 60dB. Despite being relatively lower performing than the best-in-class CCD pixels at that time, Tower Semiconductor’s GS technology was a huge market success, mainly because of much higher supported speeds at a higher resolution, which is hard to support using CCD technology. This initiated the shift in industrial cameras from CCD to CIS technology.
  • Gen 2: Our second-generation pixels were developed during our cooperation with Intel’s first RealSense™ IR camera. Originally intended for commercial applications like gesture control and 3D rendering, we adapted the technology in 2014 for industrial applications by combining 180nm periphery with 110nm metal lines in the pixel. This innovation enabled us to offer a pixel as small as 3.6um with noise of about 3e and rejection ratio of about 65dB (for the smallest pixel).
  • Gen 3: Our third generation of GS was developed using the 110nm Cu metallization technology in our TPSCo fab in Japan. In this version we had two embedded micro-lenses, that helped focus the light on the small diode area in this pixel, and also incorporated a tungsten shield (exactly like in best in class CCD), which helped in preventing light from reaching the MN, the pixel size was reduced down to 2.7um as well as a further reduction of the noise to 2e and increase in the rejection ratio to 70dB.
  • Gen 4: Our fourth, and the latest, generation of GS pixel was announced earlier this year. It is based on our 300mm wafer 65nm light pipe technology and improved tungsten shield, further enhancing the Gen3 performance. This technology allowed us to introduce the first 2.5um GS pixel with excellent performance (references IEDM, IISW), and are currently in the final development stage on further reduction of the pixel size to 2.2um.
  • Next-gen: Looking ahead, we are already developing our next generation GS pixel which will be based on Back-Side Illumination (BSI) technology. This generation would incorporate new innovations in process integration and device design to keep the MN isolated from unwanted light while maximizing light incidence on to the photo diode.

Tower "Looking Ahead" presentation also talks about other prospective markets:

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