Selective Nitrided Gate-Oxide for RTS Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CMOS image sensors face challenges in reducing dark current and random telegraph signal noise due to silicon dangling bonds and nitrogen-induced carrier trapping at the semiconductor material-gate oxide interface, which affect pixel cell performance and lead to white pixel defects.
Innovation Solution
A pixel cell design with a nitrogen-implanted region at the semiconductor material-gate oxide interface above the photodiode, forming silicon-nitrogen bonds to reduce generation-recombination centers and eliminate nitrogen implantation in channel regions of transistors to prevent carrier trapping, thereby reducing dark current and random telegraph signal noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitrogen is implanted at the semiconductor material-gate oxide interface above the photodiode, then white pixel defects are reduced, but random telegraph signal noise increases
Solution Approach 1:
The patent applies selective nitrogen implantation only in specific regions: above the photodiode (to reduce white pixel defects) while excluding the transistor channel regions (to avoid RTS noise). This spatial differentiation of nitrogen treatment creates local quality variations that simultaneously address both white pixel defects and RTS noise concerns.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively decreases white pixel defects by 50% and dark current by 20%, and reduces random telegraph signal noise from 150 ppm to 70 ppm, improving the overall performance of the pixel cell.
Implementation Method 1
forming silicon-nitrogen bonds to reduce generation-recombination centers
Implementation Method 2
nitrogen-induced carrier trapping at the semiconductor material-gate oxide interface
Data Source
AI summary
A pixel cell includes a nitrogen-implanted region at a semiconductor material-gate oxide proximate interface located in a region above a photodiode. The pixel cell is further devoid of implanted nitrogen in channel regions of a plurality of pixel transistors. Thus, Si—N bonds are formed at the semiconductor material-gate oxide interface in the region above the photodiode, while the channel regions are protected from nitrogen implantation at the semiconductor material-gate oxide interface. Methods of forming the pixel cell are also described.