The State-of-the-Art of Mainstream CMOS Image Sensors

The steady growth of mobile phones sales (feature and smartphones) has been the primary driver for CMOS image sensor (CIS) unit shipment growth over the last 3-5 years. As CIS market revenue has grown, so have R&D spending and patent filings. This effort has resulted in advanced mobile camera systems containing phase detection pixel arrays for fast autofocus (AF), ~1 μm generation pixels with improved low-light sensitivity, advanced chip-stacking, featuring a back-illuminated CIS wafer joined with an image signal processor (ISP) wafer, and video recording up to 4K. Innovation for smartphone cameras will continue, although given the competition for these high-volume sockets, many IDMs and fabless companies are developing chips for emerging, higher margin imaging applications such as automotive, security, medical, etc. These emerging opportunities are driving technology transfers from mobile imaging to these growth areas. I. IMAGE SENSOR MARKET CONDITIONS The market for imaging chips continues to be in a growth phase. The consensus of many market research firms for the 2014 CIS market size is about $9 billion USD. Yole has predicted a 10.6% CAGR for the CIS market from 2014 to 2020 [1]. Of this total, it is estimated that Sony, Samsung, and OmniVision hold about two-thirds revenue market share, driven primarily by mobile phone and tablet camera chips. The mobile imaging market is expected to grow at a 13% CAGR from 2014 to 2020. The current market pull for mobile imaging systems includes: improved image quality, reduced power consumption, and