Light Shielding Section for Solid-State Image Sensor Sensitivity
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Solution Overview
Problem
In solid-state image sensors, the provision of a charge retaining section within the pixel leads to reduced sensitivity of the photoelectric conversion element due to a smaller PD size and generates optical noise from light leakage into the charge retaining section, making it difficult to obtain a good pixel signal.
Innovation Solution
A light shielding section with an embedded section is formed between the photoelectric conversion element and the charge retaining section on the semiconductor substrate to block light and prevent leakage, allowing for a larger charge retaining section while maintaining the sensitivity of the PD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge retaining section is provided in the pixel to enable global shutter method, then distortion in image is prevented, but the aperture ratio is decreased and sensitivity of PD is reduced
Solution Approach 1:
The invention introduces a light shielding section that extends in the depth direction (third dimension) of the semiconductor substrate. This vertical extension blocks oblique light paths without occupying additional lateral space, thus preventing optical noise while maintaining the aperture ratio and sensitivity of the PD.
Solution Approach 2:
The light shielding section acts as an intermediary structure between the PD and the charge retaining section. It selectively blocks oblique light from reaching the charge retaining section while allowing normal light to reach the PD, thus preventing optical noise without affecting the aperture ratio.
2Reliability
If a charge retaining section is provided in the pixel, then global shutter function is achieved, but optical noise is generated from light leakage into the charge retaining section
Solution Approach 1:
The light shielding section acts as an intermediary structure between the PD and the charge retaining section. It selectively blocks oblique light from reaching the charge retaining section while allowing normal light to reach the PD, thus preventing optical noise without affecting the aperture ratio.
Solution Approach 2:
The light shielding section is strategically positioned only in the region where oblique light would leak into the charge retaining section. This localized shielding approach prevents optical noise without interfering with the normal operation of the PD and the charge retaining section.
3Reliability
If the PD size is reduced to accommodate charge retaining section, then global shutter is enabled, but sensitivity of PD is reduced
Solution Approach 1:
The light shielding section extends in the depth direction (third dimension) of the semiconductor substrate. This vertical extension blocks oblique light paths without occupying additional lateral space, thus preventing optical noise while maintaining the aperture ratio and sensitivity of the PD.
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 enhances the sensitivity of the PD, prevents optical noise, and enables the acquisition of better pixel signals with a wider dynamic range, even at low illumination levels.
Implementation Method 1
a semiconductor substrate having a photoelectric conversion element converting incident light into a charge
Data Source
AI summary
A solid-state image sensor includes a semiconductor substrate having a photoelectric conversion element converting incident light into a charge and a charge retaining section temporarily retaining the charge photoelectrically converted by the photoelectric conversion element and a light shielding section having an embedded section extending in at least a region between the photoelectric conversion element and the charge retaining section of the semiconductor substrate.