Image Sensor Recess Sidewall Angle Control
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Solution Overview
Problem
CMOS image sensors experience light loss and brightness differences due to the 'canyon etching' process, resulting in significant brightness variations between the center and corners of the image, caused by the angle between the sidewall and bottom of the recess region being greater than 90 degrees.
Innovation Solution
A method is introduced where a semiconductor substrate with an active array region and peripheral circuit region is fabricated using silicon oxide dielectric layers, with a recess region formed in the second dielectric layer, and the angle between the sidewall of the second dielectric layer and the top surface of the first dielectric layer is less than 90 degrees, reducing light loss and improving uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If canyon etching process is used to reduce light loss, then light loss is reduced, but brightness uniformity deteriorates due to angle greater than 90 degrees causing thicker dielectric layer at edges
Solution Approach 1:
The patent changes the critical parameter of the etching process - the angle between the sidewall and bottom of the recess region. By controlling this angle to be less than or equal to 90 degrees through modified etching conditions, the patent achieves both reduced light loss and improved brightness uniformity across the sensor array.
Solution Approach 2:
The patent addresses the non-uniform thickness of the third dielectric layer by modifying the local geometry of the recess region. The controlled angle ensures that the dielectric layer thickness varies more uniformly across different regions of the active array, compensating for the edge effects that cause brightness non-uniformity.
2Use of energy by moving object
If canyon etching is performed to expose first dielectric layer, then light transmission is improved, but structural complexity increases due to precise angle control requirements
Solution Approach 1:
The patent simplifies the etching process by establishing specific parameter ranges - particularly the angle between sidewall and bottom being less than or equal to 90 degrees. This parameter control provides a clear fabrication guideline that reduces process complexity while achieving the desired light transmission improvement.
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 approach enhances the sensitivity of the image sensor by minimizing light loss and uniformity issues, ensuring consistent brightness across the image sensor array.
Implementation Method 1
Incident light is divided into light of different wavelengths, such as red, blue, and green, and received by the photodiode in semiconductor substrate, which is then converted into electrical signals.
Data Source
AI summary
An image sensor device includes a substrate having an active array region and a peripheral circuit region, a plurality of light-sensing elements disposed within the active array region, a first dielectric layer on the substrate, and a second dielectric layer on the first dielectric layer. A recess region is provided in the second dielectric layer to reveal a top surface of the first dielectric layer within the active array region. An angle between a sidewall of the second dielectric layer that defines the perimeter of the recess region and the top surface of the first dielectric layer is less than 90 degrees.