Tungsten-Filled Deep Trench Isolation for Global Shutter Pixels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Global shutter image sensors face inefficiencies due to parasitic light and electrical crosstalk, leading to image distortion and reduced performance in capturing fast-moving objects.
Innovation Solution
The implementation of deep trench optical isolation structures filled with tungsten around the storage transistor in pixel cells, which block parasitic stray light and charge, enhancing global shutter efficiency by preventing contamination and crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trench optical isolation structures filled with tungsten are implemented around the storage transistor, then global shutter efficiency is improved by blocking parasitic stray light and charge, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The pixel cell is segmented into isolated regions using deep trench structures that physically separate the storage transistor from surrounding areas. This segmentation prevents parasitic light and charge from affecting the storage region, thereby improving global shutter efficiency while maintaining a structured approach to isolation.
Solution Approach 2:
Tungsten-filled deep trench structures serve as intermediary elements between the storage transistor and the surrounding pixel cell environment. These trenches act as barriers that mediate the interaction between parasitic light/charge and the storage region, blocking harmful effects while allowing the storage transistor to function effectively.
2Object-affected harmful factors
If deep trench optical isolation structures are implemented, then parasitic light and charge contamination is reduced, but manufacturing process complexity increases
Solution Approach 1:
The deep trench isolation structures are formed preliminarily during the pixel cell fabrication process, before final assembly and operation. By establishing the isolation barriers early in the manufacturing sequence, the structure is prepared to inherently block parasitic light and charge from the outset, preventing contamination rather than attempting to correct it later.
3Manufacturing precision
If storage transistor isolation is enhanced to prevent crosstalk, then image capture quality for fast-moving objects is improved, but production cost and fabrication difficulty increase
Solution Approach 1:
The deep trench isolation structures provide localized quality enhancement specifically at the storage transistor region where isolation is most critical for capturing fast-moving objects. By concentrating the isolation effort where it is most needed rather than uniformly across the entire pixel cell, the solution achieves high manufacturing precision for image capture while managing overall device complexity.
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
This solution significantly improves global shutter efficiency by isolating the storage transistor from parasitic light and charge, reducing electron-hole pair generation and deep silicon electrical crosstalk, thereby enhancing image capture quality for fast-moving objects.
Implementation Method 1
deep trench optical isolation structures filled with tungsten around the storage transistor in pixel cells, which block parasitic stray light and charge
Implementation Method 2
deep trench optical isolation structures filled with tungsten around the storage transistor in pixel cells, which block parasitic stray light and charge
Data Source
AI summary
An imaging system includes a pixel array of pixel cells with each one of the pixel cells including a photodiode disposed in a semiconductor material, a global shutter gate transistor, disposed in the semiconductor material and coupled to the photodiode, a storage transistor disposed in the semiconductor material, an optical isolation structure disposed in the semiconductor material to isolate a sidewall of the storage transistor from stray light and stray charge. The optical isolation structure also includes a deep trench isolation structure that is filled with tungsten and a P+ passivation formed over an interior sidewall of the deep trench optical isolation structure. Each one of the pixel cells also include control circuitry coupled to the pixel array to control operation of the pixel array and readout circuitry coupled to the pixel array to readout image data from the plurality of pixels.