Trench-Gate Semiconductor Voltage Structure for Stable Field Distribution
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Solution Overview
Problem
Semiconductor devices with trench-gate structures face challenges in maintaining stable electric field distribution, which is dependent on the depth of the gate trench, leading to potential electric field concentration and breakdown issues.
Innovation Solution
The semiconductor device incorporates a voltage-resistant structure in the outer peripheral portion with a semiconductor region of a second conductivity type, extending deeper than the gate trench, and a surface insulating film with varying thicknesses to improve flatness and reduce electric field concentration, along with a gate trench design that includes inner and outer trenches to distribute electric fields and prevent breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the gate trench depth is increased to improve voltage resistance, then the voltage blocking capability is improved, but electric field concentration at the trench bottom increases leading to dielectric breakdown
Solution Approach 1:
The patent introduces a voltage resistant structure with different conductivity type in the outer peripheral portion at a depth position equal to or deeper than the gate trench. This creates a localized region with different electrical properties that specifically addresses the electric field concentration problem at the trench bottom without requiring overall trench deepening, thus improving voltage resistance while preventing dielectric breakdown.
Solution Approach 2:
The solution moves from a one-dimensional approach (increasing trench depth) to a two-dimensional approach by adding a voltage resistant structure in the outer peripheral portion at the same depth level. This lateral extension provides additional voltage blocking capability without increasing the vertical trench depth, thereby avoiding electric field concentration at the trench bottom.
2Strength
If the gate trench is made deeper to enhance voltage blocking, then the voltage handling capability improves, but the electric field distribution becomes unstable and dependent on trench depth
Solution Approach 1:
By introducing a voltage resistant structure with different conductivity type in the outer peripheral portion, the patent creates a localized region that stabilizes the electric field distribution. This structure provides a reference potential that makes the electric field distribution less sensitive to variations in gate trench depth, thereby enhancing stability.
3Manufacturing precision
If the surface insulating film thickness is reduced to improve flatness for wire bonding, then the surface flatness and wire bonding reliability improve, but the insulating capability may be compromised
Solution Approach 1:
The patent applies different surface insulating film thicknesses in different regions: a thinner film in the cell portion for flatness and wire bonding, and a thicker film in the outer peripheral portion for insulating capability and voltage resistance. This spatial differentiation allows both requirements to be satisfied simultaneously.
Data Source
AI summary
A semiconductor device of the present invention includes a semiconductor layer of a first conductivity type having a cell portion and an outer peripheral portion disposed around the cell portion, formed with a gate trench at a surface side of the cell portion, and a gate electrode buried in the gate trench via a gate insulating film, forming a channel at a portion lateral to the gate trench at ON-time, the outer peripheral portion has a semiconductor surface disposed at a depth position equal to or deeper than a depth of the gate trench, and the semiconductor device further includes a voltage resistant structure having a semiconductor region of a second conductivity type formed in the semiconductor surface of the outer peripheral portion.