A CMOS Photodiode Model Wei-Jean Liu, Oscal T.-C. Chen Signal and Media Laboratories, Dept. of Electrical Engineering, National Chung Cheng University, Chia-Yi, 621Taiwan Li-Kuo Dai, Ping-Kuo Weng, Kaung-Hsin Huang, Far-Wen Jih Solid-State Devices Materials Section, Materials & Electro-Optics Research Division, Chung-Shan Institute of Science & Technology, Tao-Yuan, Taiwan

Outline Introduction Physics Phenomenon Analysis Measurement Setup Simulation and Experiment Comparison Conclusion

Introduction CMOS technology -Lower power consumption and compatible process. Goal -To achieve a general CMOS photodiode model.

Photo Current

CMOS Photodiode Construction

Parameter Definition Photon Flux Carrier Generation Rate Absorption Coefficient *Ref. D. Schroder, “Semiconductor Material and Device Characterization”, John Wiley and Sons, Inc., pp499, 1990

Photon Current Equation N-type Semiconductor Depletion Region P-type Semiconductor Total Current *NOTE : Jdark is the rest term when incident power is zero.

Boundary Condition(I) -Surface Top Bottom *NOTE : Sp(n) is surface recombination velocity of the hole(electron) in the N-type(P-type) semiconductor surface and the value is simplified to limit to infinite.

Boundary Condition(II) -Depletion Region Edge

Boundary Condition(III) -Between Different Layers Current Density Continuity Minority Carrier Concentration Continuity

Simulation Results

Simulation Results(Cont’d) Nwell-Epi-Psubstrate Ndiffusion-Pwell-Epi-Psubstrate

Measurement Setup

Measurement Procedure Standard Detector X Test Chips

Experiments v.s. Simulation

Surface Recombination Velocity @ 0

Surface Recombination Velocity @ ∞

Surface Recombination Velocity Effect

Reference(I) Ref. [1]“Semiconductor Material and Device Characterization”, D. Schroder, John Wiley and Sons,Inc., pp233, pp364, 1990

Reference(II) Ref. [1]“Physics of Semiconductor Devices ”, S. M. Sze, , New York: John Wiley and Sons, 1980.

Reference(III)

Reference(IV)

Conclusion A CMOS photodiode model useful in all kinds of structures was accomplished. This proposed photodiode model would be useful in various circuit simulators to understand the responses of the CMOS photodiodes.