Setting up 3D sequential integration for back-illuminated CMOS image sensors with highly miniaturized pixels with low temperature fully depleted SOI transistors

This paper presents an innovative 3D architecture capable of overcoming pixel miniaturization drawbacks. Back-illuminated photodiodes are realized on a first silicon layer, while readout transistors are located on a second silicon layer. Implications of a sequential integration are evaluated in the perspective of low noise pixel performances with a comprehensive study on: 1/ setting the thermal budget limit to 700degC to preserve transfer gate performances, 2/ transferring high quality SOI by direct bonding 3/ processing HfO₂/TiN fully depleted transistors, exhibiting noise levels close to standard 2.2 mum pixels, with improvement solutions.