Doo-Won Kwon

Application of Plasma-Doping (PLAD) Technique to Reduce Dark Current of CMOS Image Sensors

Plasma doping (PLAD) was applied to reduce the dark current of CMOS image sensor (CIS), for the first time. PLAD was employed around shallow trench isolation (STI) to screen the defective sidewalls and edges of STI from the depletion region of photodiode. This technique can provide not only shallow but also conformal doping around the STI, making it a suitable doping technique for pinning purposes for CISs with sub-2-mum pixel pitch. The measured results show that temporal noise and dark signal deviation as well as dark level decrease

1/2.5" 8 mega-pixel CMOS Image Sensor with enhanced image quality for DSC application

Technology and characteristics of 8-mega density CMOS image sensor (CIS) with unit pixel size of 1.75times1.75mum2 are introduced. With recessed transfer gate (RTG) structure and other sophisticated process/device technology, remarkably enhanced saturation capacity and ultra-low dark current have been obtained, which satisfy the requirements of high density digital still camera (DSC) application

The features and characteristics of 5M CMOS image sensor with 1.9/spl times/1.9/spl mu/m/sup 2/ pixels

5 mega CMOS image sensor with 1.9mum-pitch pixels has been implemented with 0.13 mum low power CMOS process. By applying 4-shared pixel architecture, 2.5V operation voltage, and tight design rules for some critical layers in pixels, high fill factor and the corresponding high saturation could be obtained. Image lag was sufficiently suppressed by pulse-boosting of transfer gate voltage and electrical cross-talk was suppressed by use of n-type epitaxial layer. It is shown that several sophisticated processes improve sensitivity, temporal random noise, and dark current. With this technology, full 5-mega density CMOS image sensor chips have been successfully developed

Reduction of random noise in complementary metal oxide semiconductor image sensors by gate oxide interface control

Techniques to reduce random noise in complementary metal oxide semiconductor (CMOS) image sensor chips with pixel sizes as small as 2.2 ×2.2 µm2 are addressed. By applying dummy heat annealing and plasma nitrided (PN) oxide, random noise can be reduced by more than 40%. Measured results indicate that the gate oxide–Si interface is improved by a dummy heat treatment, and PN oxide is a good choice as a gate oxide for image sensors, since it has an optimal nitrogen profile as a gate oxide while it effectively suppresses boron penetration. The results show the importance of nitrogen profile control in gate oxides and of oxide curing for low noise characteristics in CMOS image sensors.

Decreasing Dark Current of Complementary Metal Oxide Semiconductor Image Sensors by New Postmetallization Annealing and Ultraviolet Curing

We demonstrate a new postmetallization annealing and ultraviolet (UV) treatment process for reducing the dark current of image sensors. The new method utilizes a large amount of hydrogen in a plasma-silicon nitride film (p-SiNx) as a hydrogen diffusion source. Through charge pumping measurement, it is proved that this method effectively reduces the interface trap density of pixel transistors, thereby decreasing the dark current of image sensors. Although the postetch process for removing p-SiNx films induces plasma damage during the etch step, the damage can be effectively cured by the subsequent UV annealing.