Trench Gate Semiconductor Fabrication With Rounded Trench Openings
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Solution Overview
Problem
In semiconductor devices with trench gate structures, electric field concentration at the opening end portion of the trench can lead to poor connection between electrodes and the semiconductor substrate, and increased on-resistance due to reduced distance between trenches.
Innovation Solution
A method for manufacturing semiconductor devices with trench gate structures that involves forming a rounded portion at the opening end portion of each trench, achieved by performing a second etching under conditions where the mask selectivity is higher than that of the semiconductor substrate, thereby minimizing surface removal and maintaining connectivity between trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a trench gate structure is formed with sharp opening end portions, then the manufacturing process is simpler, but electric field concentration occurs at the opening ends leading to poor connection and increased on-resistance
Solution Approach 1:
The patent applies curvature by forming rounded opening end portions in the trenches instead of sharp corners. This is achieved through a two-step etching process: first forming the trench with a mask, then performing a second etching that rounds the opening ends. The rounded shape eliminates electric field concentration at sharp corners, improving connection quality and reducing on-resistance while maintaining manufacturing feasibility
2Productivity
If the distance between trenches is reduced to increase device density, then productivity improves, but on-resistance increases due to electric field concentration and poor connection
Solution Approach 1:
By rounding the opening end portions of trenches, the patent eliminates electric field concentration that would otherwise occur at sharp corners. This allows trenches to be placed closer together without increasing on-resistance, enabling higher device density and productivity while maintaining electrical performance
3Reliability
If a second etching is performed to form rounded portions, then electric field concentration is suppressed, but surface removal increases potentially reducing connectivity between trenches
Solution Approach 1:
The patent changes etching parameters by performing a second etching with controlled conditions that selectively round the opening end portions. The etching parameters (such as etchant concentration, temperature, or exposure time) are optimized to remove only a minimal amount of surface material at the opening ends while maintaining the overall surface integrity and connectivity between trenches
Solution Approach 2:
The second etching process applies local quality by selectively rounding only the opening end portions of the trenches while leaving the rest of the trench structure and surface intact. This localized modification suppresses electric field concentration at critical points without affecting the overall surface connectivity between trenches
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 electric field concentration at the trench opening and reduces the risk of poor connections between electrodes and the semiconductor substrate, while also lowering on-resistance by maintaining the integrity of the surface between trenches.
Implementation Method 1
forming a plurality of trenches, which extend in a longitudinal direction along a planar direction of the semiconductor substrate, in the semiconductor substrate adjacent to the one surface by performing a first etching; forming a rounded portion at an opening end portion of each of the plurality of trenches by performing a second etching
Data Source
AI summary
A method for manufacturing a semiconductor device includes: preparing a semiconductor substrate; arranging a mask on one surface of the semiconductor substrate; forming opening portions in the mask by patterning so as to expose planned formation regions of the semiconductor substrate where trenches are to be formed; forming the trenches, which extend in a longitudinal direction along a planar direction of the semiconductor substrate, in the semiconductor substrate adjacent to the one surface, by performing a first etching using the mask; forming a rounded portion at an opening end portion of each of the trenches by performing a second etching in a state where the mask is arranged and under a condition that a selectivity of the mask is higher than that of the semiconductor substrate; and arranging a gate insulating film and a gate electrode in each of the trenches, thereby to form trench gate structures.