Development of an indirect time-of-flight pixel for 3D imaging

Tuesday, November 25, 2025 at 1:30 p.m. 
Defense of doctoral thesis by Bruno Henrique LOPES , for the  University  Grenoble Alpes, speciality " NANO ELECTRONIC & NANO TECHNOLOGIES "

Keywords:
Time-of-flight,pixel,3D imaging,architecture

Abstract :
The growing popularity of 3D imaging originates from its vast potential applications, such as enhancing automotive safety and enabling secure facial recognition for device authentication. This PhD work aims to model, simulated, design and fabricate indirect time-of-flight (iToF) pixels used for 3D image sensing. The iToF technique employs intensity-modulated waves for distance measurement.

Technology Computer-Aided Design simulation tools are used to analyze pixel structures, evaluating key metrics such as power consumption, demodulation contrast (DMC), parasitic light sensitivity, and quantum efficiency (QE). Different pixel solutions are benchmarked using a multiphysics simulation setup.

Based on detailed simulation analysis, a new iToF pixel technology is proposed. This, the fast photogate (FPG) using transfer vertical gates (TVG), overcomes the limitations of planar gates. Simulations demonstrate an improved QE/DMC trade-off, with high QE (40%) at 940 nm, DMC above 80% at 200 MHz, and near-zero parasitic light sensitivity. The simulated DMC values obtained with this new pixel exceeds state-of-the-art specifications. Higher DMC values are achieved at reduced bias voltages for the FPG. The low bias voltages required for photogenerated charge transfer result in lower pixel power consumption.

• Anne Kaminski - Director - University Professor - Grenoble INP, UGA
• Maryline Bawedin - Co-director - Associate Professor (MCF) - Grenoble INP, UGA
• Pascal Fonteneau - Company supervisor - Engineer - STMicroelectronics
• Vincent Goiffon - Reviewer - University Professor - Institut supérieur de l'aéronautique et de l'espace (ISAE-SUPAERO)
• Francis Calmon - Reviewer - University Professor - CNRS - Institut des Nanotechnologies de Lyon (INL)
• Panagiota Morfouli - Examiner - University Professor - Grenoble INP, UGA