A CMOS photodiode model

This paper utilizes the concepts of equilibrium equations and minority carrier continuity to build and derive a CMOS photodiode model. By using the TSMC 1P3M 0.5 μm CMOS technology, photodiodes with two different types of N_well-P_Epitaxial-P_substrate and N_diffusion-P_well-P_Epitaxial-P_{su bstrate} were fabricated. Measurements were done to test the photoresponse from 400 nm to 1000 nm. To simulate the photoresponses of N_well-P_Epitaxial-P_substrate and N_diffusion-P_well-P_Epitaxial-P_{su bstrate} photodiodes using the proposed model, if an inadequate value of the surface recombination velocity which is affected by the surface defects in the manufacture process is utilized, the proposed model would yield a little larger error in estimating the photoresponse in a shorter wavelength. To overcome this problem, the curve mapping scheme is applied to find the adequate boundary condition of the surface recombination velocity with the least mean squared error thus allowing the proposed model to achieve a good performance. The concept of the model proposed herein could be utilized in designing any CMOS photodiode for simulating its photo-electronic characteristics in various industrial applications