Gettering Regions in CMOS Image Sensors
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Solution Overview
Problem
CMOS image sensors suffer from optical characteristic degradation due to contamination by metal atoms during the ion implantation process, which affects the semiconductor substrate and photodiode performance.
Innovation Solution
Incorporating gettering regions in the semiconductor substrate, formed using carbon atoms through ion implantation, adjacent to the source/drain regions to capture and prevent the migration of metal atoms, thereby maintaining the optical integrity of the image sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ion implantation is performed to form source and drain regions, then transistor formation is achieved, but metal atoms are implanted as contaminants into the semiconductor substrate
Solution Approach 1:
The patent extracts harmful metal atoms from the semiconductor substrate by introducing gettering regions that selectively capture and remove metal contaminants. The gettering regions act as extraction zones that pull out metal atoms from the active device regions, thereby separating the harmful contaminants from the functional transistor structures.
Solution Approach 2:
The patent introduces gettering regions as intermediary structures between the ion implantation process and the photodiode regions. These gettering regions serve as mediator zones that intercept metal atoms during diffusion, preventing direct contamination of the photodiode while allowing the ion implantation process to proceed for transistor formation.
2Reliability
If metal atoms diffuse into the photodiode, then contamination occurs, but optical characteristics are degraded
Solution Approach 1:
The patent converts the harmful effect of metal atom diffusion into a beneficial outcome by using the same diffusion mechanism to transport metal atoms toward gettering regions. Instead of preventing diffusion entirely, the invention harnesses diffusion to move contaminants away from photodiodes and into dedicated gettering zones, thereby transforming a harmful process into a contaminant removal mechanism.
Solution Approach 2:
The gettering regions function as intermediary zones positioned between the source/drain regions and photodiodes. These intermediaries intercept metal atoms during diffusion, capturing them before they can reach and degrade the photodiode's optical characteristics, thus protecting the sensitive photodetector regions.
3Object-affected harmful factors
If gettering regions are formed adjacent to source/drain regions, then metal atom capture is improved, but device complexity increases
Solution Approach 1:
The patent merges the formation of gettering regions with existing device structures by integrating them into the same fabrication process flow. The gettering regions are formed using the same ion implantation and thermal processing steps as the source/drain regions, combining multiple functions into unified process sequences and reducing overall manufacturing complexity.
Solution Approach 2:
The gettering regions serve multiple functions simultaneously: they act as metal atom sinks, provide thermal management during processing, and define structural boundaries for device regions. This multi-functionality reduces the need for separate dedicated structures, thereby minimizing the increase in device complexity while maximizing contaminant capture efficiency.
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 gettering regions effectively capture metal atoms, reducing their impact on the photodiode and enhancing the optical characteristics of the CMOS image sensor by preventing metal atom migration and maintaining image sensor performance.
Implementation Method 1
The gettering region may be formed by implanting carbon atoms through an ion implantation process. The carbon atoms may be implanted into the semiconductor substrate at a dose of about 1.0E14 atoms/cm2 to about 5.0E15 atoms/cm2, and with an energy of about 10 keV to about 100 keV.
Data Source
AI summary
Method of manufacturing image sensors having a plurality of gettering regions. In the method, a gate electrode may be formed on a semiconductor substrate. A source/drain region may be formed in the semiconductor substrate to be overlapped with the gate electrode. A gettering region may be formed in the semiconductor substrate to be adjacent to the source/drain region.