A Numerical Method of Aligning the Optical Stacks for All Pixels

Abstract

Reducing performance verification time is significant in product launch and production costs. This is especially true because aligning the optical stacks of off-axis pixels is a time-consuming task, but it is important to maintain sensitivity. In this paper, a numerical method to align the optical stacks of off-axis pixels is suggested in order to reduce performance test time. The components of the numerical method are the optical stack height, refractive index, and chief ray angle in order to calculate the optical stacks' optimal shift distance. The proposed method was investigated to confirm effectiveness by using optical simulation. The sub-micron backside illumination (BSI) pixels were simulated, having 2 × 2 microlens, quad-color filter array, and in-pixel deep trench isolation (DTI). Moreover, the proposed method was evaluated for various pixel pitches, microlens shapes, and CRAs. As a result, the optical stacks were optimized by using the numerical method and validated via optical simulation. Therefore, the proposed numerical method is expected to help reduce the time and cost.