Integration and characterization of spin on dielectric materials in image sensor devices

Abstract

Continuously increasing performance requirements in CMOS image sensor based digital camera devices demand significant improvement of the optical part of the device as well as improved endurance to camera module assembly. Optical structures construction is the key element to improve the device efficiency and sensitivity. This is especially true for the small pixel size sensors used for mobile phone applications, wherein pitch size is reduced to integrate more pixels on the same area of semiconductor surface. Traditionally, the optical stack is based on organic photo-resist like materials. The introduction of inorganic Spin On Dielectric (SOD) materials opens several new options. Two novel applications of these materials are presented in this paper. In the first one, a waveguide is formed in the device backend and filled with high refractive index SOD (RI=1.652 @ 650nm) to improve optical performance. The second one employs a low refractive index SOD (RI~1.4 @650nm) topcoat, which enables easier micro lens engineering and optimization, and further offers advantage of organic micro lens mechanical protection. The two integration schemes are presented along with SOD material characteristics and processing details.