Multi-Orientation Trenching for Superjunction Wafer Flatness
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Solution Overview
Problem
Conventional trenching methods in semiconductor manufacturing cause wafer bowing and warping, especially when processing large diameter wafers, which leads to processing inefficiencies and increased risk of chipping or breakage, preventing cost reduction through larger wafer diameters.
Innovation Solution
A method of manufacturing superjunction devices by forming trenches with multiple orientations on a semiconductor wafer, such as vertical and horizontal orientations, to distribute mechanical stress evenly and reduce bowing and warping, allowing for the use of larger wafer diameters while minimizing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional single-orientation trenching is used, then manufacturing process is simple, but wafer bowing and warping increase significantly
Solution Approach 1:
The trenching process is segmented into multiple passes with different orientations (e.g., first pass at 0°, second pass at 90°). Each pass removes material in a specific direction, distributing the mechanical stress removal across multiple controlled steps rather than one aggressive single-orientation etch, thereby reducing overall wafer distortion.
Solution Approach 2:
The patent employs periodic alternation between different trenching orientations in successive processing passes. This periodic action allows the wafer to experience alternating stress patterns that prevent cumulative bowing in a single direction, maintaining better wafer flatness throughout the deep trenching process.
2Reliability
If deep trenching is performed to manufacture superjunction devices, then device performance is improved, but wafer bowing and warping are exacerbated
Solution Approach 1:
Deep trenching required for superjunction devices is divided into multiple sequential passes with different orientations. This segmentation allows the total trench depth to be achieved while distributing the mechanical stress across multiple lighter etching operations, preventing excessive wafer bowing that would occur with a single deep etch pass.
Solution Approach 2:
The patent performs preliminary shallow trenching passes at different orientations before completing the full deep trench depth. These preliminary actions create a stress-distributed foundation that prevents severe bowing during subsequent deeper etching steps, enabling successful completion of deep superjunction trenches while maintaining wafer flatness.
3Ease of manufacture
If larger wafer diameters are used to reduce manufacturing cost, then cost efficiency is improved, but bowing and warping become more prevalent
Solution Approach 1:
The multi-orientation trenching process segments the material removal into controlled passes that distribute stress evenly across large wafer areas. This approach enables cost-effective processing of large-diameter wafers (e.g., 6-inch or larger) by preventing the severe bowing and warping that would otherwise make such large wafers unprocessable.
Solution Approach 2:
The patent changes the processing parameters by introducing multiple trenching orientations and passes, which fundamentally alters the stress distribution pattern during etching. This parameter change enables the use of larger wafer diameters for cost reduction while maintaining sufficient wafer flatness through controlled stress management.
Data Source
AI summary
A method of manufacturing a superjunction device includes providing a semiconductor wafer having at least one die. At least one first trench having a first orientation is formed in the at least one die. At least one second trench having a second orientation that is different from the first orientation is formed in the at least one die.