I-Shaped Gate Transistor for CMOS Image Sensor Noise Reduction
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Solution Overview
Problem
CMOS image sensors face high random telegraph signal (RTS) noise in pixel source follower and reset gate transistors, which decreases image sensor sensitivity.
Innovation Solution
The design incorporates a transistor with an I-shaped gate and a buried channel, which reduces noise by causing current to flow through a central region, avoiding interface traps at the edges of shallow trench isolation regions and the gate dielectric, thereby minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional transistor designs are used in CMOS image sensors, then manufacturing is simpler, but random telegraph signal (RTS) noise is high which decreases image sensor sensitivity
Solution Approach 1:
The gate is segmented into multiple gates arranged in a specific pattern (e.g., interdigitated or staggered configuration). This segmentation allows the transistor channel to be divided into multiple regions, each controlled by a separate gate, thereby reducing the impact of interface traps in any single region and minimizing RTS noise while maintaining manufacturing feasibility
Solution Approach 2:
The transistor design implements local quality by creating regions with different electrical characteristics within the same transistor structure. Specifically, the channel is divided into segments with different gate controls, allowing optimal performance in each region while collectively reducing overall noise. This may include varying gate lengths, widths, or positions to optimize local current distribution and minimize trap effects
2Productivity
If transistor feature size is reduced to increase integration density, then more components fit in a given area, but noise from interface traps increases
Solution Approach 1:
By segmenting the gate into multiple smaller gates, the design maintains a compact overall footprint suitable for high integration density while creating multiple smaller channel regions. This segmentation reduces the probability that any single interface trap will significantly impact the overall transistor performance, thereby maintaining low noise levels even as feature sizes are reduced
Solution Approach 2:
The invention addresses noise issues in scaled transistors by introducing a spatial dimension through multi-gate configurations. Instead of simply reducing feature sizes in two dimensions, the design uses multiple gates positioned at different locations and orientations, creating a three-dimensional control structure that distributes and mitigates trap effects across multiple spatial dimensions
Data Source
AI summary
Transistors, methods of manufacturing thereof, and image sensor circuits are disclosed. In one embodiment, a transistor includes a buried channel disposed in a workpiece, a gate dielectric disposed over the buried channel, and a gate layer disposed over the gate dielectric. The gate layer comprises an I shape in a top view of the transistor.