Longitudinal Image Sensor Layout Without Light Shielding Films
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In longitudinal spectroscopic image sensors, color mixture occurs due to light leakage into implantation plugs, leading to decreased sensitivity and aperture ratio, which hinders the utilization of superior light use efficiency and color separation.
Innovation Solution
A solid-state imaging device with stacked photoelectric conversion units and a longitudinal transistor, where one photoelectric conversion unit is formed over the gate electrode embedded in the semiconductor layer, allowing charge reading without a light shielding film, thus preventing color mixture and increasing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light shielding film is formed on the implantation plug to prevent color mixture, then color separation is improved, but the aperture ratio on the photodiode decreases and sensitivity decreases
Solution Approach 1:
The patent extracts and removes the light shielding film from the implantation plug structure. By eliminating this component, the patent achieves both prevention of color mixture (through alternative means) and maintenance of high aperture ratio, thereby resolving the contradiction between color separation and sensitivity.
Solution Approach 2:
The patent transitions from a planar light shielding approach to a three-dimensional stacked photodiode structure. By stacking photodiodes at different depths in the silicon substrate, color separation is achieved through depth-based wavelength filtering rather than through lateral light shielding, thus maintaining aperture ratio while achieving color separation.
2Object-affected harmful factors
If the implantation plug is covered with a light shielding film to prevent light leakage, then color mixture is prevented, but the aperture ratio decreases
Solution Approach 1:
The patent converts the potentially harmful light leakage into a beneficial depth-based wavelength separation mechanism. By utilizing the vertical stacking of photodiodes at different depths, the patent transforms what would be a source of color mixture into a mechanism for achieving superior color separation through differential light absorption at various depths.
Solution Approach 2:
The patent moves the color separation function from the lateral dimension (light shielding film) to the vertical dimension (depth-stacked photodiodes). This dimensional transition allows light to be separated by wavelength through its interaction with photodiodes at different depths, eliminating the need for lateral light shielding and preserving aperture ratio.
3Reliability
If a longitudinal spectroscopic image sensor is used to improve light use efficiency, then sensitivity is improved, but color mixture occurs due to light leakage into the implantation plug
Solution Approach 1:
The patent segments the light detection function across multiple photodiodes stacked at different depths. Each photodiode is responsible for detecting specific wavelength ranges based on its depth position, creating a segmented approach to spectral detection that maintains high light use efficiency while preventing color mixture through depth-based wavelength assignment.
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 configuration achieves superior color separation and high sensitivity by preventing color mixture and enhancing the aperture ratio, resulting in improved image quality and sensitivity.
Implementation Method 1
the photodiodes are stacked at different depths in silicon to perform a color separation using that an absorption wavelength of light is different depending on a depth of the silicon substrate
Data Source
AI summary
A solid-state imaging device and an imaging apparatus that enable provision of a solid-state imaging device having superior color separation and high sensitivity are provided. The solid-state imaging device includes a semiconductor layer in which a surface side becomes a circuit formation surface, photoelectric conversion units PD1 and PD2 of two layers or more that are stacked and formed in the semiconductor layer, and a longitudinal transistor Tr1 in which a gate electrode is formed to be embedded in the semiconductor layer from a surface of the semiconductor layer. The photoelectric conversion unit PD1 of one layer in the photoelectric conversion units of the two layers or more is formed over a portion of the gate electrode of the longitudinal transistor Tr1 embedded in the semiconductor substrate and is connected to a channel formed by the longitudinal transistor Tr1.