Epitaxial Body Layer Switching Element for Electric Field Attenuation
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Solution Overview
Problem
Existing switching elements with diffusion-based body layers suffer from reduced electric field attenuation due to curved inclined surfaces, leading to decreased effectiveness in attenuating the electric field applied to the gate insulating film.
Innovation Solution
The use of an epitaxial body layer instead of a diffusion layer ensures a wider, less curved inclined surface at the interface between the body layer and the first n-type semiconductor layer, effectively attenuating the electric field applied to the gate insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a diffusion layer is used to form the body layer, then the body layer can be formed by conventional diffusion processes, but impurities diffuse toward the first n-type semiconductor layer side causing the inclined surface to curve and reducing the width of the inclined surface
Solution Approach 1:
The patent changes the formation method of the body layer from diffusion-based to epitaxial-based. This parameter change in the manufacturing process prevents impurity diffusion into the first n-type semiconductor layer, thereby maintaining a straight inclined surface with precise geometry while still being manufacturable through established epitaxial techniques.
Solution Approach 2:
The patent replaces the thermal diffusion process with an epitaxial growth process. Instead of relying on thermal diffusion of impurities through the semiconductor lattice, the body layer is formed by controlled epitaxial deposition, which allows precise control over layer composition and geometry without unwanted impurity spreading.
2Ease of manufacture
If the inclined surface is curved due to impurity diffusion, then the body layer can be formed by diffusion processes, but the inclined surface becomes relatively narrow and the electric field attenuation effect is decreased
Solution Approach 1:
The patent changes the body layer formation method from diffusion to epitaxial growth, which fundamentally alters the impurity distribution profile. This parameter change ensures that impurities do not diffuse into the first n-type semiconductor layer, maintaining a straight inclined surface that provides sufficient width for effective electric field attenuation.
3Reliability
If an epitaxial body layer is used instead of a diffusion layer, then a wider and less curved inclined surface is achieved for better electric field attenuation, but the manufacturing process becomes more complex
Solution Approach 1:
The patent replaces the diffusion process with epitaxial growth to form the body layer. While epitaxial growth may appear more complex, it provides precise control over layer formation and eliminates the need for subsequent diffusion steps, actually simplifying the overall process while achieving superior geometric control and electric field attenuation.
Solution Approach 2:
The patent changes the body layer formation mechanism from thermal diffusion to epitaxial deposition. This parameter change enables precise control of the body layer composition and interface geometry, achieving the desired straight inclined surface profile through the epitaxial growth conditions rather than through diffusion 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 configuration results in improved electric field attenuation and reduced on-resistance in MOSFETs, maintaining low on-resistance while effectively suppressing the electric field applied to the gate insulating film.
Implementation Method 1
the body layer is constituted by an epitaxial layer
Implementation Method 2
diffusion of impurities to the first n-type semiconductor layer side from the body layer side hardly occurs
Implementation Method 3
an electric field to be applied to the gate insulating film can be attenuated by providing the inclined surface on the interface between the body layer below the gate electrode and the first n-type semiconductor layer
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A switching element (10) includes a semiconductor substrate (12) that includes a first n-type semiconductor layer (44), a p-type body layer (42) constituted by an epitaxial layer, and a second n-type semiconductor layer (40) separated from the first n-type semiconductor layer (44) by the body layer (42), a gate insulating film (28) that covers a range across the surface of the first n-type semiconductor layer (44), the surface of the body layer (42), and the surface of the second n-type semiconductor layer (40), and a gate electrode (26) that faces the body layer (42) through the gate insulating film (28). An interface (50) between the first n-type semiconductor layer (44) and the body layer (42) includes an inclined surfaces (52,63) and in the bottom of the body layer (42) a surface parallel with the upper surface (12a). The inclined surfaces (52,63) is inclined such that the depth of the body layer (42) increases as a distance from two opposite ends end (42a) of the body layer (42) increases in a horizontal direction towards the middle of the body layer. An inclined surface (52,63) is disposed below the gate electrode (26).