A high sensitivity and high full well capacity CMOS image sensor using active pixel readout feedback operation with positions of pixel select switch, operation timings and initial bias conditions has been reported. 1/3-inch 5.6-μm pixel pitch 800(H) x 600(V) color CMOS image sensors with the switch X set on or under the pixel SF have been fabricated by a 0.18-μm 2-Poly 3-Metal CMOS technology. The comparison of the active pixel readout feedback operation between two CMOS image sensors, which only have the deference of the switch X's position, has performed. As to the result, the switch X set on the pixel SF is favor for the active pixel readout feedback operation to improve the readout gain and the S/N ratio. This CMOS image sensor achieves high readout gain, high conversion gain, low input-referred noise and high full well capacity by the active pixel readout feedback operation.
A temperature-resistant 1/3 inch SVGA (800×600 pixels) 5.6 μm pixel pitch wide-dynamic-range (WDR) CMOS image
sensor has been developed using a lateral-over-flow-integration-capacitor (LOFIC) in a pixel. The sensor chips are
fabricated through 0.18 μm 2P3M process with totally optimized front-end-of-line (FEOL) & back-end-of-line (BEOL)
for a lower dark current. By implementing a low electrical field potential design for photodiodes, reducing damages,
recovering crystal defects and terminating interface states in the FEOL+BEOL, the dark current is improved to 12 e-
/pixel-sec at 60 deg.C with 50% reduction from the previous very-low-dark-current (VLDC) FEOL and its contribution to the temporal noise is improved. Furthermore, design optimizations of the readout circuits, especially a signal-and noise-hold circuit and a programmable-gain-amplifier (PGA) are also implemented. The measured temporal noise is 2.4 e-rms at 60 fps (:36 MHz operation). The dynamic-range (DR) is extended to 100 dB with 237 ke- full well capacity. In order to secure the temperature-resistance, the sensor chip also receives both an inorganic cap onto micro lens and a metal hermetic seal package assembly. Image samples at low & high temperatures show significant improvement in image qualities.
A temperature resistant wide dynamic range (WDR) CMOS image sensor has been developed using the very low dark current front-end of line (VLDC FEOL) and the metal hermetic seal ceramic leadless chip carrier (CLCC) package suppressing the degradation of the spectra response of the on-chip micro lens and color filter (OCML/OCCF). A 1/4 inch VGA 5.6 &mgr;m pixel pitch WDR CMOS image sensor has been fabricated through 0.18 &mgr;m 2P3M process with the VLDC FEOL which contains the pinned photodiode with less electrical fields, the less plasma etching damages, the transfer gate with the suppressed current at Si-SiO2 interface and the furnace temperature process for the re-crystallization. The sensor chips with the conventional OCML/OCCF assembled into the metal hermetic seal package by the low residual oxygen vacuum welding machine has finally received the thermal stress test (150 deg.C/500 hours). The dark current is 350 pA/cm2 at 85 deg.C (50 pA/cm2 at 60 deg.C). No degradation of the spectra response in any of R/G/B pixels is observed after the thermal stress test. It is found that the thermal decomposition of the OCML/OCCF (phenol resin) is not caused easily in nitrogen with the low residual oxygen concentration. The sample images captured by the WDR CMOS image sensor assembled camera keep good quality up to 85 deg.C.