Tapered Light-Blocking Wall for Image Sensor Sensitivity
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Solution Overview
Problem
The existing image sensors face an issue with insufficient sensitivity due to the absorption of light by metal reflective layers, which attenuate incident light when it is reflected multiple times, preventing effective improvement in optical sensitivity.
Innovation Solution
An image sensor design featuring a light-blocking wall with a tapered-shape cross-section adjacent to the semiconductor substrate at pixel boundaries, which reflects incident light onto the photoelectric conversion units, reducing multiple reflections and absorption, and improving light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a metal reflective layer is used to reflect incident light focused at parts aside from the photoelectric conversion units, then the light can be guided to the photoelectric conversion units, but the light is absorbed by the metal reflective layer and greatly attenuated when reflected multiple times
Solution Approach 1:
The patent changes the shape parameter of the light-blocking wall from a conventional vertical or flat configuration to a tapered configuration with a specific angle. This parameter change optimizes the light reflection path, ensuring that light reflected by the light-blocking wall reaches the photoelectric conversion unit directly without requiring multiple reflections from the metal reflective layer, thereby reducing light absorption and attenuation.
2Device complexity
If the photoelectric conversion units are formed on the semiconductor substrate directly below the lenses in a mosaic shape, then the device structure is simplified, but the improvement in sensitivity is insufficient
Solution Approach 1:
The patent applies local quality by introducing light-blocking walls with different properties at specific locations (pixel boundaries) rather than uniformly across the entire device. The light-blocking walls are strategically positioned at boundaries between adjacent pixels to reflect oblique incident light into the photoelectric conversion units, while the central regions maintain the simple mosaic structure. This localized modification improves sensitivity without significantly increasing overall device complexity.
3Ease of operation
If incident light is reflected multiple times by the reflective layer, then light can be guided to photoelectric conversion units, but the light is greatly attenuated due to absorption
Solution Approach 1:
The patent extracts the light guidance function from the metal reflective layer by introducing dedicated light-blocking walls with tapered configurations. These light-blocking walls are specifically designed to reflect oblique incident light at pixel boundaries directly into the photoelectric conversion units, thereby extracting the light guidance function from the general-purpose metal reflective layer and eliminating the need for multiple reflections that cause attenuation.
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 tapered light-blocking wall configuration enhances the sensitivity of the image sensor by ensuring that incident light is reflected only once, minimizing absorption and flare, and effectively guiding light to the photoelectric conversion units, thereby improving image quality.
Implementation Method 1
an on-chip lens that focuses the incident light onto the photoelectric conversion unit
Implementation Method 2
a photoelectric conversion unit disposed on a semiconductor substrate and photoelectrically converting incident light that is irradiated
Implementation Method 3
a light-blocking wall disposed adjacent to the semiconductor substrate at a boundary between the plurality of pixels and configured such that a side of the light-blocking wall that is irradiated with the incident light has a tapered-shape cross-section, the light-blocking wall blocking the incident light
Data Source
AI summary
The sensitivity of an image sensor is improved.The image sensor includes a plurality of pixels and a light-blocking wall. The plurality of pixels included in the image sensor each includes a photoelectric conversion unit disposed on a semiconductor substrate and photoelectrically converting incident light that is irradiated, and an on-chip lens that focuses the incident light onto the photoelectric conversion unit. The light-blocking wall included in the image sensor is disposed adjacent to the semiconductor substrate at a boundary between the plurality of pixels and configured such that a side of the light-blocking wall that is irradiated with the incident light has a tapered-shape cross-section, the light-blocking wall blocking the incident light.