Insulated Gate Switching Device Trench Segmentation
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Solution Overview
Problem
Existing insulated gate type switching devices, such as MOSFETs, face challenges in maintaining a stable gate threshold during mass production due to variations in p-type impurity implantation angles and densities, leading to inconsistent electric field distribution and device performance.
Innovation Solution
A manufacturing method involving the formation of a laminated structure with specific gate trench geometries and oblique implantation of impurities at controlled angles to create a connection region between the body and bottom regions, ensuring that impurities are suppressed from certain side surfaces, thereby stabilizing the gate threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If p-type impurities are implanted to the longitudinal side surfaces of the gate trenches by oblique irradiation, then the connection region is formed to reduce electric field around the bottom portion of the gate trench, but the irradiation direction varies causing p-type impurities to be implanted to the short directional side surfaces, resulting in gate threshold variation
Solution Approach 1:
The gate trench is divided into two distinct portions: a first portion with a first width and a second portion with a second width wider than the first width. This segmentation allows different impurity implantation strategies for each portion, enabling the connection region to be formed only where needed while preventing unwanted impurity implantation in other areas.
Solution Approach 2:
The patent applies local quality by creating a connection region with increased p-type impurity density specifically at the longitudinal side surfaces of the second portion of the gate trench, while maintaining lower impurity density at the longitudinal side surfaces of the first portion. This localized differentiation achieves electric field control precisely where required without affecting other regions.
2Manufacturing precision
If the semiconductor substrate is set so that the irradiation direction of the p-type impurities and the short directional side surfaces are parallel, then impurity implantation to short directional side surfaces is suppressed, but it is difficult to accurately set the substrate and the irradiation direction varies, leading to incomplete suppression
Solution Approach 1:
The gate trench is segmented into a first portion and a second portion with different widths. The oblique implantation geometry is designed such that the implantation profile selectively affects only the longitudinal side surfaces of the second portion, creating the connection region without requiring precise alignment to suppress implantation on short directional side surfaces.
Solution Approach 2:
The gate trench has an asymmetric cross-sectional profile with different widths at different portions. This asymmetry, combined with oblique implantation at a specific angle, creates a selective impurity distribution that forms the connection region in the second portion while naturally preventing impurity implantation in the first portion, regardless of minor substrate alignment variations.
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 suppresses variations in gate threshold and electric field concentration near the gate trench, enhancing the reliability and consistency of insulated gate type switching devices during mass production.
Implementation Method 1
oblique implantation of impurities at controlled angles to create a connection region between the body and bottom regions
Data Source
AI summary
A method of manufacturing an insulated gate type switching device includes forming a gate trench that has a first portion with a first width in a first direction and a second portion with a second width in the first direction, the second width being wider than the first width. In an oblique implantation, second conductivity type impurities are irradiated at an irradiation angle inclined around an axis orthogonal to the first direction. The first width, the second width, and the irradiation angle are set such that the second conductivity type impurities are suppressed, at a first side surface of the first portion, from being implanted into a part below a lower end of a second semiconductor region, and at a second side surface of the second portion, the impurities are implanted into the part below the lower end of the second semiconductor region.