Semiconductor Heterojunction Interface State Density Reduction
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Solution Overview
Problem
Conventional semiconductor device manufacturing methods using polycrystal silicon as a hetero semiconductor region result in deteriorated interface characteristics due to defective crystals at the grain boundary, leading to increased interface state density.
Innovation Solution
A method involving the formation of a heterojunction between an N−-type silicon carbide epitaxial layer and an N+-type polycrystal silicon region, with a thermal oxide film formed by oxidizing both layers in an oxidizing atmosphere to reduce interface state density, using a gate insulating film and depositing film to improve interface characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a gate insulating film is formed by depositing method on polycrystal silicon, then the manufacturing process is simple, but the interface characteristics are deteriorated due to defective crystals at grain boundary
Solution Approach 1:
The patent applies preliminary oxidation treatment to the polycrystal silicon surface before depositing the gate insulating film. This preliminary action of forming an oxidized layer eliminates defective crystals at grain boundaries in advance, ensuring high-quality interface characteristics before the main deposition process occurs.
Solution Approach 2:
The patent introduces an oxidized layer as an intermediary between the polycrystal silicon and the gate insulating film. This intermediary layer acts as a buffer that prevents direct contact between the depositing film and defective crystal regions, thereby improving interface characteristics while maintaining manufacturing simplicity.
2Reliability
If thermal treatment is performed in oxidizing atmosphere, then interface state density is reduced, but additional process steps are required
Solution Approach 1:
The patent merges the oxidation process with the gate insulating film formation process by performing thermal treatment in oxidizing atmosphere during the same thermal processing step. This combines two functions (oxidation and insulating film formation) into one process step, reducing overall process complexity while achieving low interface state density.
Solution Approach 2:
The patent utilizes parameter changes in the thermal treatment process, specifically controlling temperature and atmosphere composition, to simultaneously achieve oxidation of the polycrystal silicon surface and formation of the gate insulating film. By optimizing these parameters, the process achieves dual benefits without requiring separate dedicated steps.
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 enhances the interface characteristics and reliability of the semiconductor device by reducing interface state density and achieving low resistance conduction characteristics through controlled oxidation and impurity introduction.
Implementation Method 1
forming a thermal oxide film between the first insulating film and facing surfaces of the semiconductor substrate and the hetero semiconductor region by performing a thermal treatment in an oxidizing atmosphere
Data Source
AI summary
Methods of manufacturing a semiconductor device including a semiconductor substrate and a hetero semiconductor region including a semiconductor material having a band gap different from that of the semiconductor substrate and contacting a portion of a first surface of the semiconductor substrate are taught herein, as are the resulting devices. The method comprises depositing a first insulating film on exposed portions of the first surface of the semiconductor substrate and on exposed surfaces of the hetero semiconductor material and forming a second insulating film between the first insulating film and facing surfaces of the semiconductor substrate and the hetero semiconductor region by performing a thermal treatment in an oxidizing atmosphere.