Split-Gate Trench MOSFET Shield Oxide Fabrication
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Solution Overview
Problem
Existing fabrication techniques for split-gate trench MOSFETs are complex and expensive, requiring multiple masks, which increases processing costs and complexity.
Innovation Solution
A semiconductor device with a poly-protected shield oxide is developed, featuring a plurality of gate trenches with specific insulating layers and conductive materials, reducing the number of masks needed in the fabrication process by using a thick liner insulator and intermediate dielectric layers to simplify the trench structure and protect the insulator during contact formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fabrication techniques are used for split-gate trench MOSFETs, then the device performance is achieved, but the fabrication process becomes complex and expensive requiring 8 or more masks
Solution Approach 1:
The patent combines multiple functions into fewer processing steps. The thick liner insulator layer (first insulating layer) serves both as a protective barrier during fabrication and as the final gate dielectric. The intermediate dielectric layer (second insulating layer) is formed and then selectively removed to create contact holes, eliminating the need for separate masking steps that would otherwise be required to protect different regions at different stages.
Solution Approach 2:
The thick liner insulator layer is formed preliminarily before any conductive materials are deposited. This preliminary insulator layer protects the underlying semiconductor substrate throughout the entire fabrication process, including during the deposition of polysilicon gates and the formation of contact holes. By establishing this protective layer first, the patent eliminates the need for multiple subsequent protective masks.
2Manufacturing precision
If multiple masks are used during fabrication, then precise patterning is achieved, but processing costs and complexity increase
Solution Approach 1:
The thick liner insulator layer serves as a self-protective element throughout the fabrication process. Instead of requiring external masks to protect the substrate and underlying layers, the structure itself provides the necessary protection. The intermediate dielectric layer similarly serves dual purposes: as a protective barrier during deposition and as a sacrificial layer that defines contact hole locations when removed, eliminating the need for separate protective masks.
3Reliability
If a thick liner insulator is used to protect the substrate, then substrate protection is improved, but the number of masks needed increases
Solution Approach 1:
The thick liner insulator layer performs multiple functions: it protects the semiconductor substrate during fabrication, serves as the gate dielectric, and provides electrical isolation. The intermediate dielectric layer also performs multiple functions: it protects underlying structures during polysilicon deposition, and when selectively removed, it defines the contact hole pattern. By designing layers with multiple functions, the patent eliminates the need for separate protective masks for each function.
Data Source
AI summary
A plurality of gate trenches is formed into a semiconductor substrate in an active cell region. One or more other trenches are formed in a different region. Each gate trench has a first conductive material in lower portions and a second conductive material in upper portions. In the gate trenches, a first insulating layer separates the first conductive material from the substrate, a second insulating layer separates the second conductive material from the substrate and a third insulating material separates the first and second conductive materials. The other trenches contain part of the first conductive material in a half-U shape in lower portions and part of the second conductive material in upper portions. In the other trenches, the third insulating layer separates the first and second conductive materials. The first insulating layer is thicker than the third insulating layer, and the third insulating layer is thicker than the second.