Trench Oxide Growth Layout for Stable Subthreshold Silicon Devices
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Solution Overview
Problem
Existing semiconductor devices face issues with thinning of the oxide film at the open end of a trench, leading to subchannel formation and humps in sub-threshold characteristics due to leakage currents.
Innovation Solution
The semiconductor device incorporates a trench with an open end inclined in a specific direction relative to the crystal orientation of the Si monocrystal, enhancing the growth rate of the oxide film at the open end through an oxidation treatment, thereby suppressing thinning and subchannel formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the oxide film is formed by thermal oxidation treatment, then the oxide film is formed on the main surface, but the oxide film thins at the open end of the trench due to crystal orientation effects
Solution Approach 1:
The patent applies asymmetry by forming a tapered portion at the open end of the trench with a specific inclination angle (α) of 45 degrees or less. This asymmetric structure compensates for the natural thinning of the oxide film at the open end caused by crystal orientation effects, ensuring uniform effective oxide film thickness across different trench regions and preventing subchannel formation that would degrade subthreshold characteristics.
Solution Approach 2:
The patent applies local quality by creating a tapered portion specifically at the open end of the trench where the oxide film naturally thins. This localized structural modification ensures that the oxide film maintains appropriate thickness at the critical open end region while preserving the overall trench structure, thereby preventing leakage currents and maintaining reliable transistor operation.
2Manufacturing precision
If the trench open end is formed with a specific inclination to enhance oxide film growth, then the oxide film thickness is improved, but the trench structure becomes more complex
Solution Approach 1:
The patent applies asymmetry by forming a tapered portion specifically at the open end of the trench with a controlled inclination angle. This asymmetric structure is designed to match the crystal orientation of the semiconductor substrate, creating a symmetric relationship between the tapered portion and the underlying crystal structure. This approach simplifies the manufacturing process by aligning with natural crystal growth patterns while achieving precise oxide film thickness control.
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
This approach effectively prevents subchannel formation and humps in sub-threshold characteristics by optimizing the oxide film growth, improving the semiconductor device's performance.
Implementation Method 1
forming an oxide film which is constituted of an oxide of the Si chip and formed as a film on the main surface and at the open end
Data Source
AI summary
The semiconductor device includes an Si chip which has a main surface facing a {100} plane, a trench which is formed by digging down the main surface and has an open end extending inclined in a <110> direction side with respect to a <100> direction in a plan view, and an oxide film which is constituted of an oxide of the Si chip and formed as a film on the main surface and at the open end.