A 35 mm 13.89 Million Pixel CMOS Active Pixel Image Sensor

Abstract

This paper discusses a 13.89 million pixels CMOS image sensor for digital SLR cameras. The pitch of the 3-transistor active pixel is 8 microns. The sensor has a full well charge of 117K electrons and 33 electrons temporal noise, and a dynamic range of 71 dB. The fixed pattern noise is 0.14 % RMS, obtained by an on-chip correction circuit. Color filters have been optimized for best photographic performance. The pixel array area is equal to the size of 35 mm film (36 x 24 mm 2). Essentially, this means that the photographer gets the same image with the digital camera as with film, without lens magnification factor. Two technological challenges have to be overcome to make a sensor of this size. The sensor size exceeds the field area of steppers used to fabricate sub-micron CMOS chips. To solve this, a stitching technique has to be applied during processing of this device. A second problem of such large devices is the variation of the angle-of-incidence of the light on the silicon, causing the efficiency of micro lenses to vary along the focal plane. To avoid this problem, a pixel design with an inherently high fill factor is used. The product of fill fact or and quantum efficiency on this pixel is 30%, a number that cannot be further increased by the use of micro lenses. 1.