Semiconductor Cavity Sidewall Perpendicularity via Dry-Wet Etching
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Solution Overview
Problem
Existing backside illuminated (BSI) image sensor devices face challenges in downsizing due to tapered cavity profiles and rough surfaces, which limit sensing ability and affect light photo response quality.
Innovation Solution
A method involving a dry etching process to create a cavity with sloped sidewalls followed by a wet etching process to make the sidewalls perpendicular, increasing the volume and improving the surface quality of the heterogeneous radiation-sensing region, filled with germanium for enhanced light sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dry etching process is used to create a cavity, then the cavity can be formed with controlled depth and shape, but the sidewalls become tapered and the surface becomes rough
Solution Approach 1:
The etching process is segmented into two distinct stages: first a dry etching process to create the initial cavity with controlled depth, then a wet etching process to correct the sidewall profile. This segmentation allows each process to optimize for its specific function without compromising the other.
Solution Approach 2:
The wet etching process acts as an intermediary step that mediates between the dry etching process and the final cavity structure. It corrects the tapered sidewalls created by dry etching without removing excessive material, using selective chemical etching to achieve vertical profiles.
2Reliability
If the cavity volume is increased to improve light sensing ability, then more light can be detected, but the device size and complexity increase
Solution Approach 1:
The methodology changes the etching parameters by switching from a purely dry etching process to a combined dry-wet etching sequence. This parameter change enables better control over cavity volume and shape, maximizing light sensing ability while maintaining manageable device dimensions.
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 method enhances the light sensing ability and photo response quality by increasing the volume of the radiation-sensing region and reducing surface roughness, addressing the limitations of tapered profiles and crystal defects in existing BSI devices.
Implementation Method 1
performing a dry etching process upon the front surface of the substrate to form a cavity with sloped sidewalls
Implementation Method 2
performing a wet etching process upon the front surface of the substrate to further etch the sidewalls of the cavity to be perpendicular to the front surface of the substrate
Data Source
AI summary
A semiconductor structure is disclosed. The semiconductor substrate includes: a front surface and a back surface; and a heterogeneous radiation-sensing region in the semiconductor substrate, the heterogeneous radiation-sensing region including a top surface, a bottom surface and sidewalls, the top surface being adjacent to the front surface of the semiconductor substrate, the sidewalls being perpendicular to the front surface of the semiconductor substrate, and the bottom surface being parallel to the front surface of the semiconductor substrate. An associated manufacturing method is also disclosed.