Backside Deep Trench Isolation for Image Sensor Leakage Paths
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Solution Overview
Problem
Current image sensors face issues with current leakage paths due to blanket deep N-doped wells, leading to high power consumption during standby mode, especially in small pixel designs where these paths can create unnecessary power usage.
Innovation Solution
Incorporating a backside deep trench isolation (DTI) structure region between devices and the guard ring region in the pixel array substrate to block current leakage paths, while maintaining a blanket deep N-doped well for maximizing full well capacity without complex manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If blanket deep N-doped wells are used to maximize pixel full well capacity, then photosensitivity and charge storage are improved, but current leakage paths form between peripheral devices and guard ring region
Solution Approach 1:
The patent segments the continuous blanket deep N-doped well into isolated sub-doped well portions by introducing deep trench isolation structures. These trenches physically divide the N-doped region, creating electrically isolated segments that prevent current leakage paths while preserving the charge storage capacity of each pixel's photodiode.
Solution Approach 2:
The deep trench isolation structures serve as intermediary elements between the peripheral devices and the guard ring region. These trenches, filled with dielectric material, act as electrical barriers that block current leakage paths without interfering with the photosensitive function of the pixels.
2Loss of energy
If deep trench isolation structures are introduced to block current leakage, then power consumption is reduced, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent merges the deep trench isolation structures with the existing blanket deep N-doped well formation process. By combining these functions into a single integrated structure, the patent reduces the need for separate isolation steps while achieving both charge storage and leakage prevention objectives.
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 DTI structure effectively reduces or prevents current leakage, thereby minimizing power consumption during low power modes and enhancing the overall efficiency of the imaging system.
Implementation Method 1
a backside deep trench isolation (BDTI) structure disposed between the guard ring region and the at least one device and proximate to the backside of the semiconductor substrate. The BDTI structure is configured to block current leakage paths
Data Source
AI summary
A pixel array substrate includes a semiconductor substrate including a pixel array, a first side, and a second side opposite the first side, a guard ring region in the semiconductor substrate, formed of a doped semiconductor, enclosing the pixel array, and extending into the semiconductor substrate from the first side, and a peripheral region in the semiconductor substrate and enclosing the guard ring region. The peripheral region includes at least one device and a deep trench isolation (DTI) structure region disposed between the guard ring region and the at least one device and proximate to the second side of the semiconductor substrate. The DTI structure region is configured to block an electric current path between a P-N junction in the guard ring region and the at least one device.