Trench Isolation Structure Using Nitrogenous Mask for Leakage Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Deep trench isolation technologies face challenges in high voltage power devices due to hot electrons/holes being trapped at the oxide/polysilicon interface, leading to cross-talk and isolation failure, which affects the performance and pressure resistance of these devices.
Innovation Solution
A trench isolation structure is manufactured by forming a first trench with a wide top and narrow bottom, filling it with silicon oxide, creating a nitrogen-containing compound sidewall residue, and using this residue as a mask to etch a second deeper trench, followed by polysilicon deposition and silicon oxide coverage, to enhance isolation and reduce leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trench isolation is used to reduce leakage and improve isolation performance, then isolation effectiveness is improved, but hot electrons/holes become trapped at the oxide/polysilicon interface causing cross-talk and isolation failure
Solution Approach 1:
The patent removes the problematic polysilicon fill material from the deep trench isolation structure, extracting the source of trap generation that causes hot electron/hole accumulation and cross-talk, while maintaining the trench isolation's leakage reduction benefits
Solution Approach 2:
The patent changes the material parameter of the trench fill from polysilicon to alternative materials that do not generate traps at the oxide interface, fundamentally altering the electrical characteristics to eliminate cross-talk while preserving isolation functionality
2Manufacturing precision
If conventional photolithography masking is used to define trench patterns, then manufacturing precision is achieved, but the number of masks and process complexity increase
Solution Approach 1:
The patent employs self-aligned masking techniques where the mask pattern is automatically positioned using the trench structure itself or previously formed features as alignment references, eliminating the need for separate alignment steps and reducing mask count while maintaining precision
Solution Approach 2:
The patent combines multiple functions into single process steps, such as integrating the masking function with the etch process or combining pattern definition with structural formation, thereby reducing the total number of discrete steps and masks required
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 improves the isolation performance and pressure resistance of high voltage power devices by reducing leakage and cross-talk, while minimizing the number of photolithography masks required, thus enhancing the reliability of deep trench isolation structures.
Implementation Method 1
filling silicon oxide into the first trench by depositing
Implementation Method 2
forming a silicon oxide corner structure at a corner of the top of the first trench by thermal oxidation
Implementation Method 3
depositing a nitrogen-containing compound on the surface of the wafer to cover the surface of the silicon oxide in the first trench
Implementation Method 4
dry-etching the nitrogen-containing compound, removing the nitrogen-containing compound on the surface of the silicon oxide in the first trench
Data Source
AI summary
A method for manufacturing a trench isolation structure comprising forming a shallow trench having a wider upper section and a narrower lower section in a wafer surface, removing part of the silicon oxide by etching, forming a silicon oxide corner structure at a corner at a top corner of the shallow trench by thermal oxidation, depositing silicon nitride on the wafer surface to cover surfaces of the shallow trench silicon oxide and the silicon oxide corner structure, dry etching the silicon nitride on the shallow trench silicon oxide surface thereby forming masking silicon nitride residues extending into the trench, etching downwards to form a deep trench, forming silicon oxide layers on a side wall and the bottom of the deep trench, depositing polycrystalline silicon in the shallow and deep trenches, removing the silicon nitride, and forming silicon oxide in the shallow trench to cover the polycrystalline silicon.