Single Deep Termination Trench for Stable Transistor Breakdown
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Solution Overview
Problem
Traditional transistor fabrication techniques often result in a decrease in breakdown voltage due to process variations and require multiple processing masks and steps, leading to unreliable termination breakdown voltages.
Innovation Solution
The method involves depositing a first and second epitaxial layer, forming a single termination trench greater than 10 microns in depth, and filling it with a dielectric, which reduces processing complexity and enhances breakdown voltage reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple termination trenches about 5 microns in depth are used, then the horizontal electric field at die perimeter can be managed, but the breakdown voltage becomes unreliable and decreases due to process variations
Solution Approach 1:
The patent combines multiple shallow termination trenches (about 5 microns deep) into a single deep termination trench (more than 10 microns deep). This merging approach consolidates the termination function into one structure that extends deeper into the drift region, providing more robust breakdown voltage control that is less sensitive to process variations in trench depth and spacing.
Solution Approach 2:
The patent transitions from a shallow termination structure to a deep termination structure by increasing the vertical dimension of the termination trench. The single termination trench extends more than 10 microns into the drift region, utilizing the vertical dimension more effectively to manage the horizontal electric field and provide stable breakdown voltage characteristics.
2Reliability
If multiple termination trenches are used, then termination breakdown voltage can be achieved, but the number of processing masks and steps increases
Solution Approach 1:
The patent merges multiple termination trench formation operations into a single trench formation operation. By consolidating the termination function into one deep trench rather than multiple shallow trenches, the number of photolithography masks and etching steps is reduced, simplifying the fabrication process while maintaining reliable termination breakdown voltage.
3Ease of manufacture
If traditional termination trench depth is used (about 5 microns), then fabrication is simpler, but breakdown voltage decreases due to process variations
Solution Approach 1:
The patent increases the depth of the termination trench from about 5 microns to more than 10 microns, utilizing the vertical dimension more effectively. This deeper trench provides better electric field management and more robust breakdown voltage characteristics that are less sensitive to process variations, while still using standard fabrication techniques.
Data Source
AI summary
In one aspect, a method of fabricating a transistor includes depositing a first epitaxial layer; depositing a second epitaxial layer on the first epitaxial layer; forming a single termination trench in the second epitaxial layer; and filling the termination trench with a dielectric. A depth of the termination trench is greater than 10 microns. In another aspect, a transistor includes a first epitaxial layer; a second epitaxial layer on the first epitaxial layer; and a single termination trench in the second epitaxial layer. The termination trench is greater than 10 microns and is filled with a dielectric.