Insulated Pixel Contact for Noise Reduction
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Solution Overview
Problem
In semiconductor image pickup devices, noise is generated during charge transfer between the inside and outside of a semiconductor substrate, particularly due to the depletion layer formed between conductivity types, which affects image quality and sensitivity.
Innovation Solution
A semiconductor device is designed with a conductive region of a first conductivity type, a charge accumulation region of a second conductivity type separated by a separation section, and a contact connecting the charge accumulation region to an external wiring layer, reducing the size of the depletion layer in contact with the insulating film to suppress noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photoelectric conversion section is arranged outside the silicon substrate to increase sensitivity and saturated charge amount, then all incident photons can be used for photoelectric conversion improving image quality, but noise is generated during charge transfer from the outside photoelectric conversion section to inside the silicon substrate
Solution Approach 1:
An insulating film is introduced as an intermediary between the charge accumulation region and the external photoelectric conversion section. This insulating film prevents direct contact between the depletion layer and the insulating film, thereby eliminating the noise generation mechanism while still allowing charge transfer through the contact structure.
Solution Approach 2:
The charge accumulation region is segmented from the surface of the conductive region by introducing a separation section. This segmentation creates a physical barrier that prevents the depletion layer from contacting the insulating film, thus suppressing noise while maintaining the external photoelectric conversion section configuration.
2Manufacturing precision
If pixel size is reduced to increase the number of pixels, then the image pickup device can capture more detail, but the number of photons entering each unit pixel decreases leading to lowered sensitivity and saturated charge amount
Solution Approach 1:
The photoelectric conversion section is moved from inside the substrate to outside the substrate, utilizing the vertical dimension. This dimensional change allows larger photoelectric conversion areas without increasing pixel footprint, thereby maintaining sensitivity and saturated charge amount even as pixel density increases.
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 effectively decreases noise during charge transfer, enhancing image quality and sensitivity by minimizing the contact area between the depletion layer and the insulating film, thereby improving the overall performance of the semiconductor device.
Implementation Method 1
a contact disposed in the conductive region, the contact electrically connecting the charge accumulation region and an external wire of the multilayer wiring layer
Data Source
AI summary
A solid-state image pickup unit including a pixel section having a plurality of unit pixels two-dimensionally arranged in a matrix formation, wherein a unit pixel includes a conductive region of a first conductivity type having a surface adjacent to a multilayer wiring layer, a charge accumulation region of a second conductivity type formed within the first conductive region, wherein the charge accumulation region is separated from the surface of the conductive region adjacent to the multilayer wiring layer by a separation section, and a contact disposed in the conductive region, the contact electrically connecting the charge accumulation region and an external wire of the multilayer wiring layer.