Semiconductor Edge Structure With Multi-Slope Trench Transition
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Solution Overview
Problem
Existing manufacturing methods for electronic devices, such as Schottky diodes, using silicon carbide substrates face challenges with premature avalanche-multiplication due to steep edge transitions, leading to increased reverse leakage current and reduced device efficiency.
Innovation Solution
A manufacturing method involving the formation of a drift layer with a top surface and a first conductivity type, followed by the creation of trenches and a depression region with distinct slopes, allowing for an inclined edge transition region between the active area and the edge termination region, reducing electrical field concentration and premature avalanche-multiplication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If anisotropic etching is used to form trenches with vertical side walls, then the device compactness is improved, but premature avalanche-multiplication occurs due to steep edge transitions
Solution Approach 1:
The edge transition region is segmented into multiple zones with different slopes (first slope region and second slope region), allowing the structure to achieve both compactness and reduced field concentration. The first slope region provides a gradual transition while the second slope region maintains verticality for compactness.
Solution Approach 2:
Different regions of the edge transition structure are given different local qualities (slopes) to serve different functions. The first slope region (45°-60°) reduces field concentration, while the second slope region (75°-85°) maintains compactness, with each region optimized for its specific purpose.
2Reliability
If isotropic etching is used to form inclined edge transition regions, then premature avalanche-multiplication is reduced, but the device area increases
Solution Approach 1:
The edge transition region is divided into segmented zones with different slopes. The first slope region uses isotropic etching characteristics to reduce field concentration, while the second slope region uses anisotropic etching to maintain vertical walls, achieving both reliability and area efficiency.
Solution Approach 2:
The solution moves from a single-slope two-dimensional profile to a multi-slope three-dimensional structure, allowing the edge transition region to achieve both gradual field transition and compact footprint by utilizing vertical dimension optimization.
3Manufacturing precision
If multiple etching masks are used to form different slopes, then manufacturing precision is improved, but device complexity and manufacturing time increase
Solution Approach 1:
Multiple etching operations that would normally require separate masks are merged into a single anisotropic etching process. The single mask with strategically placed openings allows simultaneous formation of both slope regions, reducing manufacturing complexity while maintaining precision.
Solution Approach 2:
The mask is designed in advance with pre-calculated opening positions and dimensions that directly determine the slopes of both regions. This preliminary design of the mask geometry eliminates the need for multiple masking steps while achieving the desired precise edge transition structure.
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 method effectively reduces the area occupied by the active region, minimizes undesirable field line concentrations, and enhances the reverse-biasing performance of the diode, thereby improving the overall efficiency and reliability of the electronic device.
Implementation Method 1
The step of formation of the trenches 9 envisages a chemical etching, for example a directional dry etching
Implementation Method 2
formed in manufacturing steps subsequent to that of FIG. 1 and not illustrated herein on the top surface 2a and within the recesses 9, in particular in direct contact with the drift layer 2 and with the junction-barrier elements 8, is a metal layer
Implementation Method 3
forming an edge-termination structure laterally to said trench by implanting dopant species which have a second conductivity different from the first conductivity
Data Source
AI summary
A manufacturing method of an electronic device includes: forming a drift layer of an N type; forming a trench in the drift layer; forming an edge-termination structure alongside the trench by implanting dopant species of a P type; and forming a depression region between the trench and the edge-termination structure by digging the drift layer. The steps of forming the depression region and the trench are carried out at the same time. The step of forming the depression region comprises patterning the drift layer to form a structural connection with the edge-termination structure having a first slope, and the step of forming the trench comprises etching the drift layer to define side walls of the trench, which have a second slope steeper than the first slope.