Group III Nitride Contact Trenches With Dummy Trench Fill Control
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Solution Overview
Problem
Existing methods for filling trenches with n-doped Group III nitride material in semiconductor substrates face challenges such as non-conformal growth, unwanted growth structures, and incomplete filling, especially in trenches with high aspect ratios.
Innovation Solution
Incorporating wider dummy trenches with n-doped Group III nitride material, where the dummy trenches have a width at least 1.1 times that of the contact trenches, to guide the growth and ensure complete filling of the contact trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trenches with high aspect ratios are filled with n-doped Group III nitride material, then electrical connection to the two-dimensional charge gas is achieved, but non-conformal growth and incomplete filling occur
Solution Approach 1:
Dummy trenches are introduced as intermediary structures with wider width (B ≥ 1.1b) than contact trenches. These dummy trenches act as mediators that modify the growth environment and material distribution, enabling conformal filling of the narrower contact trenches while preventing non-conformal growth and incomplete filling
Solution Approach 2:
The dummy trenches are formed and configured before the actual contact trench filling process. By pre-establishing these wider trenches with specific geometric relationships (B ≥ 1.1b), the growth conditions are optimized in advance to ensure that subsequent material deposition fills the contact trenches completely and uniformly
2Reliability
If contact trenches are filled with n-doped Group III nitride material, then ohmic contact is formed, but unwanted vertical growth structures are created
Solution Approach 1:
The dummy trenches serve as intermediary structures that intercept and redirect excess material growth. By providing wider spaces (B ≥ 1.1b) adjacent to the contact trenches, they absorb the harmful vertical growth tendency and guide material deposition into desired conformal patterns, preventing unwanted vertical structures from forming in the contact regions
Solution Approach 2:
The dummy trenches are configured in advance to counteract the harmful vertical growth effect. Their wider geometry (B ≥ 1.1b) creates a preliminary anti-action by providing alternative growth paths and modifying stress distributions, thereby preventing the formation of unwanted vertical structures before they can develop in the contact trenches
3Manufacturing precision
If dummy trenches with width B ≥ 1.1b are introduced, then uniform filling of contact trenches is achieved, but device complexity increases
Solution Approach 1:
The trench system is segmented into two distinct types: contact trenches (width b) for electrical connection and dummy trenches (width B ≥ 1.1b) for growth control. This segmentation allows each type to serve its specific function optimally, with the dummy trenches providing geometric control that simplifies the filling process of contact trenches, thereby reducing overall manufacturing complexity despite the additional structure
Data Source
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AI summary
In an embodiment, a semiconductor substrate is provided that comprises a multilayer Group III nitride substrate comprising a first major surface and at least one heterojunction that is capable of supporting a two-dimensional charge gas, at least one contact comprising a contact trench extending into the multilayer Group III nitride substrate from the first major surface. The contact trench is filled with n-doped Group III nitride material for forming an electrical connection to the two-dimensional charge gas. The semiconductor substrate further comprises at least one dummy trench extending into the multilayer Group III nitride substrate from the first major surface. The dummy trench is partially filled with n-doped Group III nitride material. The dummy trench has a width B and the contact trench has a width b, wherein B ≥ 1.1b.