Trench Pixel Capacitor Layout for CMOS Sensor Sensitivity
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Solution Overview
Problem
The integration of a capacitance element in imaging device pixels reduces the light receiving area of photo diodes, leading to decreased sensitivity of the imaging device.
Innovation Solution
Incorporating a capacitance element with a first electrode and second electrodes in trenches, where the second electrodes have a smaller cross-sectional area than contacts connected to gate electrodes, and using insulating films between these electrodes, allowing for charge accumulation without reducing the light receiving area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitance element is provided in the pixel to accumulate electric charges, then the dynamic range of the imaging device is enlarged, but the light receiving area of the photo diode decreases causing sensitivity to decrease
Solution Approach 1:
The capacitance element is configured as a trench-type structure extending in the vertical direction (depth dimension) rather than occupying horizontal plane area. The first electrode and second electrode are positioned at different vertical levels with insulating films between them, utilizing the third dimension (depth) to provide capacitance functionality without consuming additional light receiving area on the pixel surface.
Solution Approach 2:
The capacitance element is nested within the existing pixel structure by forming trenches in the semiconductor substrate or insulating layers. The first electrode and second electrode are embedded within the substrate or layered structure, with the capacitance-forming region integrated into the vertical stack of the pixel, effectively nesting the capacitance function within the photo diode's vertical architecture.
2Reliability
If the capacitance element is integrated into the pixel structure, then charge accumulation capability is improved, but the manufacturing complexity increases due to additional trenches and electrodes
Solution Approach 1:
The trench structure serves multiple functions simultaneously: it forms the capacitance element (first electrode and second electrode with insulating film), provides charge accumulation space, and can be integrated with existing pixel components such as photo diodes and transistors. The same trench formation process can be used for both capacitance elements and other pixel structures, reducing the need for separate manufacturing steps.
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 prevents the decrease in sensitivity of the imaging device by allowing charge accumulation while maintaining the light receiving area, thereby enhancing the imaging device's performance.
Implementation Method 1
a photoelectric conversion element; electric charges generated by the photoelectric conversion element
Implementation Method 2
a capacitance element configured to accumulate electric charges generated by the photoelectric conversion element
Data Source
AI summary
The present technology relates to an imaging device capable of preventing a decrease of sensitivity of the imaging device in a case where a capacitance element is provided in a pixel, a method of manufacturing an imaging device, and an electronic device. The imaging device includes, in a pixel, a photoelectric conversion element and a capacitance element accumulating an electric charge generated by the photoelectric conversion element. The capacitance element includes a first electrode including a plurality of trenches, a plurality of second electrodes each having a cross-sectional area smaller than a contact connected to a gate electrode of a transistor in the pixel, and buried in each of the trenches, and a first insulating film disposed between the first electrode and the second electrode in each of the trenches. The present technology can be applied, for example, to a backside irradiation-type CMOS image sensor.