Solid-State Image Sensor Depletion Layer Control via Fixed Charge Film
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Solution Overview
Problem
Existing solid-state image capturing devices using chalcopyrite compound semiconductors face challenges in controlling the thickness of the depletion layer, leading to issues with reset noise and photodiode depletion.
Innovation Solution
A solid-state image capturing element is designed with a photoelectric conversion film and a fixed charge film stacked on a semiconductor substrate, where the fixed charge film generates a predetermined fixed charge, allowing control over the depletion layer thickness through internal electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a photodiode is depleted to remove reset noise, then reset noise is reduced, but the thickness of the depletion layer becomes difficult to control
Solution Approach 1:
The invention changes the electrical parameters by introducing a fixed charge film with specific charge density and thickness. By adjusting the fixed charge amount and position, the depletion layer thickness can be precisely controlled while maintaining effective depletion for reset noise removal. This parameter adjustment resolves the contradiction between achieving depletion and controlling depletion layer thickness.
Solution Approach 2:
The fixed charge film acts as an intermediary layer between the photodiode and other structures. It mediates the electric field distribution, enabling controlled depletion of the photodiode without directly contacting or complicating the photodiode structure itself. This intermediary approach allows independent optimization of noise removal and depletion layer control.
2Device complexity
If a photodiode is not depleted to maintain simple structure, then device complexity is reduced, but reset noise cannot be removed
Solution Approach 1:
The invention extracts the depletion control function from the photodiode structure itself and places it in a separate fixed charge film. This allows the photodiode to maintain its simple structure while the fixed charge film provides the necessary depletion control and reset noise removal capability independently.
Solution Approach 2:
The fixed charge film serves as an intermediary that enables reset noise removal without requiring complex modifications to the photodiode structure. It provides the necessary electric field control while leaving the photodiode structure simple and straightforward.
3Manufacturing precision
If fixed charge film is added to control depletion layer thickness, then depletion layer thickness control is improved, but device complexity increases
Solution Approach 1:
By adjusting the fixed charge film parameters (charge density, thickness, position), precise depletion layer thickness control is achieved. The patent demonstrates that these parameter adjustments can be made within standard manufacturing capabilities, balancing precision with structural simplicity.
Solution Approach 2:
The fixed charge film is strategically positioned only where needed to control the depletion layer, rather than uniformly throughout the device. This localized approach provides precise control where required while minimizing overall device complexity and material usage.
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 enables precise control over the depletion layer thickness, improving the performance of the solid-state image capturing element by enhancing noise reduction and photodiode depletion management.
Implementation Method 1
a photoelectric conversion film configured to perform photoelectric conversion on incident light
Implementation Method 2
a fixed charge film configured to have a predetermined fixed charge
Data Source
AI summary
The present disclosure relates to a solid-state image capturing element, a manufacturing method therefor, and an electronic device, which are capable of controlling a thickness of a depletion layer. The solid-state image capturing element includes pixels each in which a photoelectric conversion film configured to perform photoelectric conversion on incident light and a fixed charge film configured to have a predetermined fixed charge are stacked on a semiconductor substrate. The technology of the present disclosure can be applied to, for example, back surface irradiation type solid-state image capturing elements, image capturing devices such as digital still cameras or video cameras, mobile terminal devices having an image capturing function, and electronic devices using a solid-state image capturing element as an image capturing unit.