Selective Field Oxide in Edge Termination for Reduced Field Crowding
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Solution Overview
Problem
Dielectric layers in semiconductor devices cause issues at the interface between the dielectric layer and the edge termination region, leading to potential performance degradation and electric field crowding.
Innovation Solution
A field oxide layer is selectively grown in the edge termination region with varying thicknesses over guard rings and the drift region, using an oxidation process that repairs surface damage and enhances passivation, improving dynamic performance and Schottky barrier characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric layer is deposited over the edge termination region to passivate the surface, then surface passivation is improved, but interface issues arise between the dielectric layer and the edge termination region
Solution Approach 1:
The patent applies local quality by creating a non-uniform oxide layer with different thicknesses in different regions. The oxide layer is thicker over the guard rings and thinner over the drift region, providing enhanced passivation at the critical guard ring interfaces while maintaining appropriate characteristics over the drift region. This localized variation in oxide thickness addresses the interface issues specifically where they occur most critically.
Solution Approach 2:
The oxidation process is performed as a preliminary step before final dielectric layer deposition. This preliminary oxide layer serves as an intermediate layer that prepares the surface by providing a graded transition and repairing surface damage, thereby preventing interface issues when the final dielectric layer is deposited.
2Ease of manufacture
If a uniform dielectric layer is deposited over the edge termination region, then manufacturing simplicity is maintained, but electric field crowding occurs at the edges
Solution Approach 1:
The patent implements local quality through selective oxidation that creates different oxide thicknesses in different areas. The thicker oxide over the guard rings specifically targets the edge regions where electric field crowding occurs, providing enhanced field management at these critical locations while keeping the manufacturing process relatively simple through a single oxidation step.
3Reliability
If the field oxide layer is made thicker over the drift region, then passivation coverage is improved, but dynamic performance and voltage change rate deteriorate
Solution Approach 1:
The patent resolves this contradiction by applying local quality - the oxide layer is made thinner over the drift region to maintain fast dynamic response and high voltage change rates, while being made thicker over the guard rings to provide adequate passivation coverage. This spatially differentiated approach allows both requirements to be satisfied in their respective regions.
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
The selective growth of the field oxide layer improves the integrity of the passivation, repairs surface damage, and enhances the dynamic performance of semiconductor devices, particularly in Schottky diodes, by reducing electric field crowding and increasing breakdown voltage.
Implementation Method 1
The field oxide layer is formed using an oxidation process that results in selective oxide growth on and across the edge termination region
Data Source
AI summary
A semiconductor device includes a drift region, an active region in the drift region, and an edge termination region in the drift region adjacent to the active region. The edge termination region includes one or more guard rings in the drift region. The drift region has a first conductivity type and the one or more guard rings have a second conductivity type. The edge termination region may also include a passivation layer that is disposed on the one or more guard rings and on the drift region in the edge termination region. The passivation layer has a first thickness over each guard ring and a second thickness over the drift region, where the first thickness is greater than the second thickness. Alternatively, the edge termination region may also include a passivation layer that is only disposed on the one or more guard rings in the edge termination region.