6533b82ffe1ef96bd1296203

RESEARCH PRODUCT

3D Integration : towards high-performance innovative imaging sensors

subject

description

Nowadays, CMOS image sensors are almost exclusively architectured around analog pixels. A transition to purely digital pixels would significantly improve the performances of imagers. Unfortunately, such an approach is difficult to consider because it causes an oversized and unusable pixel for the consumer market. One of the promising ways to solve this problem of pixel integration is to think not only in 2D dimensions, but in 3D dimensions by distributing the different functionalities on several interconnected wafers.Thus, the work presented in this manuscript describes the design of a purely digital image sensor in CMOS 3D-IC 130 nm Tezzaron technology. This sensor is architectured around a digital pixel integrating a first order sigma delta modulation on 10 bits of maximum resolution. The exhaustive study of the different blocks constituting the pixel allowed us to finally propose a solution guaranteeing a contained surface of silicon: final pixel size of 32.5 μm × 32.5 μm with a fill factor of at least 80 %. Regarding performances, the pixel simulations showed good results: 11 μA/pixel consumption, 60 dB signal-to-noise ratio, 7.2 effective number of bits, maximum and minimum differential nonlinearity of +1,37/-0,73 (for 10 bits) and a maximum and minimum integral nonlinearity of + 2,447/-3,5 (for 10 bits).