Angled Dielectric Openings for SiC Encapsulation
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Solution Overview
Problem
Semiconductor devices, particularly those using wide bandgap materials like SiC and Group III nitrides, face challenges with environmental protection due to defects in Plasma Enhanced Chemical Vapor Deposition (PECVD) silicon nitride (SiN) layers, which allow moisture ingress and compromise the robustness of the encapsulation structure during fabrication processes.
Innovation Solution
A multi-layer encapsulation structure is implemented with a first conformal dielectric layer and a second dielectric layer of different material, such as polyimide, where the opening for exposing metal contact structures has sidewalls with a substantially continuous slope, minimizing lateral etching and ensuring a hermetic seal by configuring etching operations to maintain consistent angles and reduce inflection points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PECVD SiN layer is used as environmental barrier, then environmental protection is improved, but the layer is prone to defects such as pin holes and columnar structures that allow moisture penetration
Solution Approach 1:
The encapsulation structure is divided into multiple layers: a first PECVD SiN layer (50-150 nm thick) and a second PECVD SiN layer (100-500 nm thick), separated by an intermediate layer. This segmentation allows each layer to serve specific functions - the first layer provides initial environmental barrier, the intermediate layer fills defects, and the second layer provides enhanced protection, collectively resolving the issue of moisture penetration through defective single-layer encapsulation.
Solution Approach 2:
The first PECVD SiN layer is deposited beforehand to provide initial environmental protection and serve as a foundation for subsequent processing. This preliminary encapsulation layer is then selectively removed at metal contact openings using wet etching, allowing metal interconnects to be formed before the second SiN layer is deposited to complete the environmental barrier, ensuring continuous protection throughout fabrication.
2Ease of operation
If opening is formed through encapsulation layers to expose metal contact structure, then electrical connection is enabled, but sidewall slope variation causes chipping and compromises seal integrity
Solution Approach 1:
The etching parameters are optimized to achieve a controlled sidewall slope of 30-60 degrees through the encapsulation layers. This parameter control ensures that the opening has sufficient width for reliable metal contact formation while maintaining a consistent slope that prevents chipping and preserves the hermetic seal of the encapsulation structure.
Solution Approach 2:
The intermediate layer is selectively positioned at the metal contact opening region, where it serves to fill defects and provide a planarization surface. This localized quality enhancement ensures that the critical sealing areas maintain encapsulation integrity while allowing proper metal contact formation in the opening region.
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 multi-layer encapsulation structure effectively prevents moisture ingress and enhances the robustness of semiconductor devices by maintaining a continuous, angled sidewall profile through the encapsulation layers, reducing chipping and improving environmental protection.
Implementation Method 1
Plasma Enhanced Chemical Vapor Deposition (PECVD) may be used to form SiN as an environmental barrier for a semiconductor device
Implementation Method 2
The opening may be formed by wet etching or other suitable techniques
Data Source
AI summary
A semiconductor die includes a semiconductor body having a gate, a source contact, and a drain contact thereon, a metal contact structure on the semiconductor body and electrically connected to the gate, the source contact, or the drain contact, and an encapsulation structure. The encapsulation structure includes first and second encapsulation layers of respective non-conductive materials stacked on the metal contact structure, and an opening extending therethrough to expose the metal contact structure. The opening includes a sidewall having a substantially continuous slope that extends through the first and second encapsulation layers to the metal contact structure. Related devices and fabrication methods are also discussed.