Image Sensor Transfer Gate Contact Layout for Smaller Pixels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image sensors face challenges in reducing damage to device components during the formation of via contacts and improving performance as pixel size decreases.
Innovation Solution
The image sensor design includes a first conductive layer with a width at least 1.5 times greater than the vertical contact width, spaced apart from the substrate, and a transfer gate vertically overlapping with the conductive layer to enhance the contact structure, reducing damage and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel size is decreased to increase the number of pixels, then the resolution is improved, but the damage to device components during via contact formation increases
Solution Approach 1:
The contact structure is divided into multiple segments: a first conductive layer forming an extended pattern, a second conductive layer, and a via contact. This segmentation allows the extended pattern to distribute the stress and damage during via contact formation, protecting the underlying transfer gate while maintaining electrical connectivity.
Solution Approach 2:
The extended pattern of the first conductive layer is formed in advance before the via contact is created. This preliminary structure serves as a protective buffer that prevents direct contact between the via and the transfer gate, thereby preventing damage before it occurs during the via formation process.
2Ease of manufacture
If the contact structure is simplified for easier manufacture, then the manufacturing process is improved, but the electrical connection reliability deteriorates
Solution Approach 1:
The contact structure extends in the horizontal dimension through the extended pattern of the first conductive layer, rather than only in the vertical dimension. This dimensional extension provides both mechanical robustness for manufacturing and electrical reliability through multiple parallel conduction paths.
3Reliability
If the conductive layer width is increased to reduce resistance, then the electrical connection is improved, but the device area increases
Solution Approach 1:
The first conductive layer has different widths at different locations: it is wider at the extended pattern region to provide low resistance and current distribution, and narrower at the via contact region to minimize area occupation. This local variation optimizes both electrical performance and space utilization.
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 design minimizes damage to the silicon material during contact formation, ensuring reliable electrical connections and maintaining low resistance, thereby enhancing the overall performance and reliability of the image sensor.
Implementation Method 1
a first photoelectric conversion region for a first pixel in the substrate
Implementation Method 2
a transfer gate configured to move charges generated in the first photoelectric conversion region to the floating diffusion region
Implementation Method 3
a first conductive layer configured to electrically connect to the transfer gate
Data Source
AI summary
An image sensor includes a substrate including a first surface and a second surface opposing the first surface; a first photoelectric conversion region; a floating diffusion region; a transfer gate configured to move charges generated in the first photoelectric conversion region to the floating diffusion region; a first conductive layer electrically connected to the transfer gate and vertically overlapping with the transfer gate; and a first vertical contact including a first surface and a second surface, wherein the first surface of the vertical contact is connected to the first conductive layer, wherein the first vertical contact is vertically overlapping with the first conductive layer, wherein the first surface of the first vertical contact has a first width in a second direction, wherein the first conductive layer has a second width at least 1.5 times greater than the first width.