Varying Depth Trench Formation Using Etchant Barrier Layer
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Solution Overview
Problem
Existing methods for forming trenches of varying depths in semiconductor devices, such as image sensors, often result in photoresist residue contamination and increased costs due to multiple etching processes, which can alter trench shapes and increase tooling expenses.
Innovation Solution
A method involving an etchant barrier layer and a single photoetch process to form trenches of varying depths, where an oxide layer prevents unwanted etching and allows for precise control of trench depths without leaving photoresist residue, reducing contamination and tooling costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple etching processes are used to form trenches of varying depths, then trench depth precision is improved, but photoresist residue contamination increases and manufacturing cost increases
Solution Approach 1:
The patent segments the trench formation process into two distinct etching steps: a first etching process that forms trenches to a first depth, and a second etching process that forms trenches to a second depth. By using separate etching processes for different depth requirements, the patent achieves precise control over trench depths while avoiding the need for repeated photoresist application and removal cycles that would generate residue contamination.
Solution Approach 2:
The patent applies a depth control layer before the etching processes, which preliminarily defines the trench depth. The depth control layer is formed at a specific position and thickness to control the final trench depth. This preliminary action allows the etching process to stop automatically at the desired depth, eliminating the need for multiple photoresist cycles and reducing contamination.
2Manufacturing precision
If multiple etching processes are used to form trenches of varying depths, then trench depth precision is improved, but tooling cost increases
Solution Approach 1:
The depth control layer serves multiple functions: it acts as an etching stop layer to control trench depth, serves as a mask for the second etching process, and can be selectively removed afterward. This multi-functionality reduces the need for separate tooling and processes for each etching step, thereby reducing overall tooling costs while maintaining precise trench depth control.
Solution Approach 2:
The patent changes the physical and chemical parameters of the depth control layer (material composition, thickness, etching resistance) to optimize its performance. By carefully selecting the layer's properties, the patent enables precise depth control using standard etching equipment, avoiding the need for specialized or expensive tooling while achieving the required manufacturing precision.
3Reliability
If varying depth trenches are formed in semiconductor devices, then electrical isolation is improved, but process complexity increases
Solution Approach 1:
The patent applies local quality by forming depth control layers at specific locations where varying trench depths are required. Instead of uniformly processing the entire wafer, the depth control layers are selectively formed only in regions where depth variation is needed, allowing precise electrical isolation in critical areas while keeping other areas simpler and reducing overall process complexity.
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 method effectively forms trenches of varying depths without photoresist residue, enhancing electrical isolation and reducing contamination and tooling costs, while maintaining desired trench shapes and improving wafer yield.
Implementation Method 1
an etchant barrier layer and a single photoetch process to form trenches of varying depths, where an oxide layer prevents unwanted etching
Data Source
AI summary
A method of forming trenches in a semiconductor device includes forming an etchant barrier layer above a first portion of a semiconductor layer. A first trench is etched in a second portion of the semiconductor layer using a first etchant. The second portion of the semiconductor layer is not disposed underneath the etchant barrier layer. The etchant barrier layer is etched through using a second etchant that does not substantially etch the semiconductor layer. A second trench is etched in the first portion of the semiconductor layer using a third etchant. The third etchant also extends a depth of the first trench.