Backside CMOS Pixel Trench Capacitors Without Light Area Loss
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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 them, allows for charge accumulation without reducing the light receiving area by positioning these elements in a manner that does not overlap with the photoelectric conversion element or by using trench type capacitors that increase capacitance without occupying more space.
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 vertically into the semiconductor substrate, utilizing the third dimension (depth) to provide capacitance functionality. This vertical arrangement allows the capacitance element to occupy space below the photo diode's light receiving surface, thereby enlarging dynamic range without reducing the horizontal light receiving area.
Solution Approach 2:
The capacitance element is nested within the pixel structure by positioning it in the semiconductor substrate beneath or adjacent to the photo diode. The trench-type capacitance element is embedded in the substrate, effectively nesting the charge accumulation function within the existing pixel footprint without requiring additional lateral space that would reduce light receiving area.
2Quantity of substance
If the capacitance element is provided in the pixel, then charge accumulation capability is improved, but the light receiving area decreases
Solution Approach 1:
The capacitance element utilizes vertical depth through trench structures in the semiconductor substrate to provide charge accumulation capability. By extending the capacitance element vertically into the substrate rather than horizontally across the surface, the design increases charge storage capacity without occupying lateral space that would reduce the photo diode's light receiving area.
Solution Approach 2:
The capacitance element is localized to specific regions within the pixel structure, with trench-type capacitors positioned in the semiconductor substrate at locations that do not interfere with the photo diode's active light receiving region. This localized placement allows charge accumulation functionality to be concentrated in specific areas while preserving the light receiving area in other areas.
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 while allowing for effective charge accumulation, enhancing the imaging device's performance by maintaining or increasing the light receiving area and capacitance.
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.