Isolation Trenches With Protective Cap For High Voltage
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Solution Overview
Problem
Existing methods for fabricating isolation trenches in semiconductor layers often result in structural and morphological defects such as openings, cracks, and polysilicon accumulation, which deteriorate insulation properties, especially in high-voltage devices.
Innovation Solution
A protective cap is introduced in the upper region of the trench to prevent damage during etching processes, using a cavity dug in the upper portion of the trench filled with a material grown by High Density Plasma Chemical Vapor Deposition (HDP-CVD) that inhibits interface formation, ensuring stable and reliable insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If TEOS oxide is used to fill the isolation trench cavity, then the trench can be filled with insulating material, but the mechanical hardness of the oxide is lower and structural defects such as openings and cracks occur
Solution Approach 1:
The patent uses a composite material structure where thermal oxide (grown by thermal oxidation) and TEOS oxide (deposited by CVD) are combined. The thermal oxide provides mechanical strength and structural integrity, while the TEOS oxide provides complete cavity filling. This composite approach resolves the contradiction between achieving full filling and maintaining mechanical hardness.
Solution Approach 2:
The patent performs thermal oxidation first to grow a liner oxide layer on the cavity walls before depositing TEOS oxide. This preliminary thermal oxidation creates a strong foundational layer that prevents subsequent cracking and openings, addressing the mechanical weakness issue before the TEOS filling process.
2Ease of manufacture
If etching processes are performed to remove nitride layer and residual sacrificial nitrides, then the device structure is cleaned, but openings and cracks are formed in the isolation trenches
Solution Approach 1:
The patent performs a protective deposition step after trench filling and before the etching processes. This protective layer acts as a cushion that prevents the formation of openings and cracks during subsequent etching operations, maintaining trench integrity while still allowing the necessary cleaning etches to proceed.
Solution Approach 2:
The patent applies a protective coating to the trench structure before the harmful etching processes. This preliminary protective action counteracts the potential damage from etching, preventing openings and cracks from forming during the manufacturing process.
3Reliability
If the silicon layer is divided into volumes by deep isolation trenches, then electrical insulation between devices is achieved, but defects such as impurities, holes, or cracks deteriorate insulation properties
Solution Approach 1:
The patent changes the physical and chemical parameters of the oxide filling process by combining thermal oxidation (low temperature, high quality) with TEOS CVD deposition (higher temperature, complete filling). This parameter combination produces an oxide fill that is both structurally sound and free of defects, ensuring high insulation reliability.
Solution Approach 2:
The thermal oxidation process automatically grows oxide conformally on the cavity walls, self-adjusting to the cavity geometry. This self-service mechanism ensures uniform coverage and eliminates the need for additional masking or alignment steps, reducing the risk of structural defects.
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 provides isolation trenches with enhanced structural and morphological integrity, preventing defects and improving insulation properties, making them suitable for high-voltage applications.
Implementation Method 1
using a cavity dug in the upper portion of the trench filled with a material grown by High Density Plasma Chemical Vapor Deposition (HDP-CVD)
Data Source
AI summary
A method is for the formation of at least one filled isolation trench having a protective cap in a semiconductor layer, and a semiconductor device with at least one filled isolation trench having a protective cap. The method allows obtaining, in an easy way, filled isolation trenches exhibiting excellent functional and morphological properties. The method therefore allows the obtainment of effective filled isolation trenches which help provide elevated, reliable and stable isolation properties.