Offset Spacer Film Formation for Image Sensor Dark Current Reduction
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Solution Overview
Problem
Conventional image capturing devices suffer from increased dark current due to plasma damage caused by dry etching processes during the formation of offset spacer films, leading to reduced sensitivity and increased power consumption.
Innovation Solution
A method for manufacturing image capturing devices where the offset spacer film is formed using anisotropic etching on the side walls of gate electrodes while leaving a portion covering the photoelectric conversion unit intact, and subsequently removing it using wet etching to prevent damage to the photo diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dry etching process is used to form offset spacer film, then anisotropic etching is achieved, but plasma damage is caused to photo diode
Solution Approach 1:
The patent divides the offset spacer film formation process into two separate stages: first forming the offset spacer film by anisotropic etching, then selectively removing portions covering photoelectric conversion units through wet etching. This segmentation allows the beneficial anisotropic etching to occur while eliminating the harmful plasma exposure to photo diodes.
Solution Approach 2:
The patent extracts and removes the portions of the offset spacer film that cover photoelectric conversion units after the initial formation. By taking out these specific portions through wet etching, the harmful plasma damage is prevented while maintaining the offset spacer film's structural benefits in other regions.
2Reliability
If offset spacer film is formed by anisotropic etching, then sidewall coverage is improved, but dark current increases due to photo diode damage
Solution Approach 1:
The process is segmented into formation and selective removal stages, allowing reliable sidewall spacer formation through anisotropic etching while subsequently removing portions that would cause dark current in photoelectric conversion units.
Solution Approach 2:
The patent converts the potentially harmful plasma etching process into a beneficial formation step for the offset spacer film, then uses wet etching to remove only the harmful portions. The harmful plasma exposure is thus converted into a useful structural formation process that doesn't directly contact photo diodes.
3Productivity
If conventional manufacturing process is used, then production efficiency is maintained, but photo diode damage occurs leading to increased power consumption
Solution Approach 1:
The manufacturing process is segmented to add a selective wet etching step that removes offset spacer film portions over photoelectric conversion units. This additional step prevents dark current generation while maintaining overall production efficiency through optimized process flow.
Solution Approach 2:
The harmful portions of the offset spacer film are extracted via wet etching after formation, preventing dark current and subsequent power consumption issues without significantly impacting manufacturing throughput.
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 approach effectively suppresses dark current, enhancing the sensitivity and reducing power consumption by minimizing damage to the photo diode during the manufacturing process.
Implementation Method 1
The offset spacer film is formed on a side wall surface of the gate electrode by providing anisotropic etching process to the first insulating film
Implementation Method 2
The portion of the first insulating film covering the photoelectric conversion unit is removed by providing wet etching process
Implementation Method 3
a photo diode for converting incoming light into a charge
Data Source
AI summary
An offset spacer film (OSS) is formed on a side wall surface of a gate electrode (NLGE, PLGE) to cover a region in which a photo diode (PD) is disposed. Next, an extension region (LNLD, LPLD) is formed using the offset spacer film and the like as an implantation mask. Next, process is provided to remove the offset spacer film covering the region in which the photo diode is disposed. Next, a sidewall insulating film (SWI) is formed on the side wall surface of the gate electrode. Next, a source-drain region (HPDF, LPDF, HNDF, LNDF) is formed using the sidewall insulating film and the like as an implantation mask.