SCIENTIFIC CMOS PIXELS JIM JANESICK SARNOFF CORPORATION JULY 1, 2004 CMOSCCD@AOL.COM

ACKNOWLEDGEMENTS Jim Andrews Sarnoff Corporation CN5300, 201 Washington Road Princeton, NJ 08543-5300 Benjamin Muto, Mark Muzilla DRS TECHNOLOGIES Sensors & Targeting Systems 3330 Miraloma Ave. Anaheim, CA 92806

■ CCD and CMOS imaging technologies will coexist. CMOS vs CCD ■ CCD and CMOS imaging technologies will coexist. ■ CCD is a mature technology. . . CMOS is currently not. ■ CMOS can compete with the CCD scientifically although major development is required. Ultimate performance is delivered by the pixel. ■ Hybrid sensors are combining technologies that can potentially deliver performance superior to CCD and CMOS bulk detectors.

CCD IMAGERS Qualities Deficiencies ■ Text book performance for all parameters (QE, read noise, MTF, dark current, linearity, etc.). Deficiencies ■ Low high-energy radiation damage tolerance. e.g. proton bulk damage and resultant CTE degradation. ■ Significant off-chip electronic support required. ■ Difficulty with high-speed readout (inherently a serial read out device).

CMOS IMAGERS Qualities Deficiencies ■ Very tolerant to high-energy radiation sources (long life time). ■ On- chip system integration (low power, low weight and compact designs). ■ High speed / low noise operation (inherently a parallel- random access readout device). Deficiencies ■ Currently lacks performance in most areas compared to the CCD (charge generation, charge collection, charge transfer and charge measurement).

CMOS PIXELS

SCIENTIFIC CMOS PIXEL CANDIDATES 3T PIXEL PINNED PHOTO DIODE DEEP N WELL PHOTO DIODE 5 T PIXEL CHARGE COUPLED PINNED PHOTO DIODE 6 T PIXEL BACKSIDE ILLUMINATED CHARGE COUPLED BURIED CHANNEL PHOTO GATE

CRITICAL CMOS PERFORMANCE PARAMETERS ■ Quantum Efficiency (QE) ■ Modulation Transfer Function (MTF) ■ Read Noise (Source Follower and Reset Noise) ■ Full Well ■ Non Linearity ■ Charge Transfer Efficiency (CTE) ■ Dark Current ■ RAD Hardness

QUANTUM EFFICIENCY PINNED PHOTO DIODE DELIVERS THE HIGHEST FRONTSIDE QE SENSITIVITY BACKSIDE ILLUMINATION DELIVERS THE HIGHEST QE POSSIBLE FOR ALL CMOS PIXEL ARCHITECTURES QE PINNING (100 % INTERNAL QE) HAS BEEN DEMONSTRATED BACKSIDE ACCUMULATION TECHNIQUES EMPLOYED: CHEMISORPTION UV CHARGING FLASH GATE ION IMPLANTATION MOLECULAR BEAM EPITAXIAL (MBE) NO FUNDAMENTAL BACKSIDE QE PROBLEMS HAVE BEEN IDENTIFIED

QUANTUM EFFICIENCY

BACKSIDE QE GOAL

FULLY DEPLETED A CONDITION REQUIRED FOR LOW PIXEL CROSS AND HIGH MTF PERFORMANCE DIFFICULT TO ACHIEVE BECAUSE CMOS OPERATING VOLTAGES ARE LOW FULL DEPLETION TECHNIQUES: HIGH RESITIVITY SILICON DEEP N-WELL TECHNOLOGY THIN EPI SILICON SUBSTRATE BIAS DEEP BORON IMPLANT FULL DEPLETION HAS BEEN DEMONSTRATED FOR 10 um BACKSIDE ILLUMINATED CMOS ARRAYS HIGH RESISTIVITY SILICON MAY BE A FUNDAMENTAL PROBLEM BECAUSE OF CMOS SWITCH LATCH UP (EXCEPT FOR HYBRID ARRAYS) DEPLETION vs SIGNAL PROBLEM

DEPLETION DEPTH vs SILICON RESISTIVITY

DEPLETION vs SIGNAL PROBLEM

DEPLETION vs SIGNAL PROBLEM

READ NOISE vs READOUT MODES 3T PIXEL ROLLING SHUTTER READOUT LIMITED BY RESET NOISE (TRUE CDS CANNOT BE PERFORMED) 5T/6T CHARGE COUPLED PIXELS PROGRESSIVE SCAN READOUT LIMITED BY SOURCE FOLLOWER NOISE (TRUE CDS PROCESSING) SNAP READOUT LIMITED BY RESET NOISE (TRUE CDS CANNOT BE PERFORMED)

SOURCE FOLLOWER READ NOISE LIMITED BY FLICKER (1/f) RANDOM TELEGRAPH NOISE (RTS) PIXEL TO PIXEL NOISE VARIANCE (2 e- < noise < 15 e- pp) FLICKER NOISE DEPENDENT ON SOURCE FOLLOWER GEOMETRY AND DRAIN CURRENT WHITE NOISE IS NEGLIGIBLE

PHOTO GATE PIXEL LOW LIGHT IMAGERY

SOURCE FOLLOWER NOISE RANDOM TELEGRAPH NOISE (RTS) RTS NOISE