Backside Isolation Trench Wet Dry Etch Profile
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Solution Overview
Problem
Existing semiconductor wafer processing techniques face challenges in efficiently forming isolation trenches through the backside of substrates without compromising the structural integrity, particularly in reducing etching time and improving throughput.
Innovation Solution
A method involving a combination of wet and dry etching techniques is employed to form an isolation trench with a tapered portion created by wet etching and a non-tapered portion by dry etching, where the wet etch is performed first to increase etching speed and then followed by dry etching to achieve a specific profile, reducing overall etching time and enhancing semiconductor wafer processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dry etching is used to form the isolation trench, then the profile precision is improved, but the etching time increases
Solution Approach 1:
The etching process is divided into two distinct segments: a wet etching step to create the tapered portion and a dry etching step to create the non-tapered portion. This segmentation allows each method to be optimized for its specific function, with wet etching providing speed and dry etching providing precision, thereby resolving the contradiction between etching time and profile precision.
Solution Approach 2:
The wet etching is performed as a preliminary action before the dry etching. This preliminary wet etching creates the tapered portion and removes the majority of the substrate thickness quickly, so that the subsequent dry etching only needs to create a thin non-tapered portion, significantly reducing the total etching time while maintaining profile precision.
2Productivity
If wet etching is used to form the isolation trench, then the etching speed is improved, but the profile control deteriorates
Solution Approach 1:
The isolation trench formation is segmented into two parts: a tapered portion created by wet etching for high speed, and a non-tapered portion created by dry etching for high precision. This segmentation allows the wet etching to operate at full speed without compromising the final profile, as the precision-critical portion is handled by the subsequent dry etching step.
Solution Approach 2:
Wet etching is used as a preliminary high-speed removal step to create the tapered portion and remove the bulk of the substrate material. This preliminary action achieves high productivity while the subsequent dry etching step provides the precise profile control needed for the final non-tapered portion, thus resolving the contradiction between speed and precision.
3Productivity
If the isolation trench is formed without a non-tapered portion, then the processing throughput is improved, but the access to materials for subsequent processing deteriorates
Solution Approach 1:
The isolation trench is designed with different local qualities: a tapered portion for efficient material removal and a non-tapered portion for functional access. The non-tapered portion acts as a localized feature that provides vertical access to underlying materials, enabling subsequent processing steps while the majority of the trench maintains the tapered geometry for optimal throughput.
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 significantly reduces etching time, improves the profile of the isolation trench for subsequent processing, and increases the number of semiconductor wafers that can be processed within a given time period, enhancing metrics like wafers per hour (WPH) and enabling better access to materials for further processing.
Implementation Method 1
A wet etch is performed to form a tapered portion of the isolation trench
Implementation Method 2
a dry etch is performed to form a non-tapered portion of the isolation trench
Data Source
AI summary
Among other things, one or more semiconductor arrangements comprising isolation trenches, and techniques for forming such isolation trenches are provided. A substrate comprises a front side surface and a backside surface. One or more devices are formed over the front side surface. A wet etch is performed to form a tapered portion of an isolation trench. A dry etch is performed to form a non-tapered portion of the isolation trench. Because both the wet etch and the dry etch are performed, etching time is reduced compared to merely using the dry etch due to the wet etch having a relatively faster etch rate than the dry etch. In an embodiment, the isolation trench provides isolation for a current leakage path associated with a device or other material formed over the front side surface. In an embodiment, metal is formed within the isolation trench for backside metallization.