Silicided Light Receiving Surface for Backside Incident Imaging Sensitivity
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Solution Overview
Problem
Existing back side incident type solid state imaging devices suffer from reduced sensitivity due to signal electric charge recombination within the semiconductor substrate, and existing solutions either complicate the manufacturing process or reduce photoelectric conversion efficiency.
Innovation Solution
A solid state imaging device with a silicided surface on the light receiving portion, where light is reflected back through the semiconductor substrate for re-use, enhancing photoelectric conversion efficiency and improving sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a back side incident type solid state imaging device is used, then light can be incident on the back side of the semiconductor substrate, but sensitivity is reduced due to signal electric charge recombination
Solution Approach 1:
The patent converts the harmful effect of light transmission through the substrate (which causes charge recombination and signal loss) into a beneficial effect by introducing a reflective layer. This reflective layer redirects the transmitted light back through the photoelectric conversion layer, allowing the light to be utilized twice - once on its original path and again after reflection - thereby converting what was previously a loss mechanism into a signal-enhancing mechanism that improves sensitivity without increasing charge recombination
Solution Approach 2:
The reflective layer creates an optical feedback mechanism where light that has passed through the photoelectric conversion layer is reflected back and passes through the layer again. This feedback loop ensures that photons which initially failed to generate charge carriers on their first pass have another opportunity to contribute to signal generation, effectively reducing the impact of charge recombination losses and improving overall detection sensitivity
2Reliability
If existing solutions are applied to improve sensitivity, then sensitivity may increase, but the manufacturing process becomes complicated
Solution Approach 1:
The reflective layer is formed using the same silicide material and deposition process as the existing photoelectric conversion layer, maintaining material homogeneity throughout the device structure. This approach allows the reflective functionality to be integrated into the existing manufacturing flow without requiring additional material types or specialized deposition techniques, thereby improving sensitivity while avoiding manufacturing process complication
Solution Approach 2:
The silicide formation process that is already required for the photoelectric conversion layer is extended to also create the reflective layer. By making the existing photoelectric conversion material serve a dual purpose - both photoelectric conversion and light reflection - the patent eliminates the need for separate reflective layer deposition processes, thus improving sensitivity without increasing manufacturing complexity
3Reliability
If existing solutions are applied to improve sensitivity, then sensitivity may increase, but photoelectric conversion efficiency is reduced
Solution Approach 1:
The patent converts the previously wasted transmitted light (which contributed to neither signal generation nor caused harm) into a beneficial resource by reflecting it back through the photoelectric conversion layer. This ensures that photons are utilized twice - once on their original path and again after reflection - thereby improving sensitivity while maintaining photoelectric conversion efficiency because the same conversion mechanism is used for both passes
Solution Approach 2:
The reflective layer enables continuous utilization of incident light energy by redirecting transmitted photons back through the photoelectric conversion layer. This continuous action ensures that light energy is not lost after a single pass but is instead repeatedly utilized for charge carrier generation, thereby improving sensitivity without reducing photoelectric conversion efficiency as the conversion process remains optimal on both forward and reflected passes
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 solution increases photoelectric conversion efficiency and achieves higher sensitivity for the solid state imaging device while maintaining a simpler manufacturing process and wider usable wavelength range.
Implementation Method 1
the surface of the light receiving portion is silicided. Therefore, the photoelectric conversion is not performed and light reached to the surface of the light receiving portion through the semiconductor substrate is reflected at the surface
Implementation Method 2
light from an object to be imaged incident on a second surface of the semiconductor substrate is photoelectric-converted inside the semiconductor substrate
Data Source
AI summary
A solid state imaging device has a semiconductor substrate, a light receiving region provided on a surface layer on a first surface side of the semiconductor substrate, the light receiving region having a silicided surface, second impurity diffusion layer provided adjacent to the light receiving region on the surface layer on the first surface side of the semiconductor substrate, a gate insulating film provided adjacent to the second impurity diffusion layer on the first surface of the semiconductor substrate, a gate electrode provided on the gate insulating film, and a third impurity diffusion layer provided on an opposite side to the second impurity diffusion layer, with the gate insulating film and the gate electrode sandwiched.