Composite Field Plate Structure to Prevent Deformation in Semiconductors
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Solution Overview
Problem
The adhesion of foreign matter to the field plate in semiconductor devices can cause deformation, leading to reduced breakdown voltage and potential short circuits.
Innovation Solution
A semiconductor device design where the field plate consists of a first metal layer made of gold and a second metal layer with higher Mohs hardness, such as tantalum, tungsten, molybdenum, niobium, or titanium, which inhibits the adhesion of foreign matter and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the field plate is made of gold (Au), then the electrical conductivity and corrosion resistance are improved, but the field plate becomes softer and more susceptible to foreign matter adhesion and deformation
Solution Approach 1:
The field plate is constructed as a composite structure with a gold layer and a harder metal layer (tantalum, tungsten, molybdenum, niobium, or titanium). The gold layer provides corrosion resistance and electrical conductivity, while the harder metal layer provides mechanical strength and resistance to deformation. This composite structure resolves the contradiction between softness and hardness.
2Reliability
If the field plate is made of gold (Au), then the electrical conductivity is improved, but foreign matter adhesion increases causing deformation
Solution Approach 1:
The composite field plate structure with gold and harder metal layers reduces foreign matter adhesion. The harder metal layer provides a more resistant surface that is less prone to adhesion of foreign matter compared to pure gold, while the gold layer maintains electrical conductivity. This resolves the contradiction between electrical conductivity and foreign matter adhesion resistance.
3Strength
If a harder metal layer is added to the field plate, then the resistance to foreign matter adhesion and deformation is improved, but the device structure becomes more complex
Solution Approach 1:
The field plate is segmented into multiple functional layers: a gold layer for electrical conductivity and corrosion resistance, and a harder metal layer for mechanical strength. This segmentation allows each layer to perform its specific function optimally while resolving the contradiction between simplicity and performance.
Solution Approach 2:
The composite structure of gold and harder metal layers provides the necessary mechanical strength and resistance to foreign matter adhesion. While the structure is more complex than a single-layer plate, the complexity is justified by the significant improvement in reliability and resistance to deformation.
Data Source
AI summary
A method for producing a semiconductor device includes forming a gate electrode, a source electrode, and a drain electrode on an upper surface of a semiconductor layer, forming a first insulating film on the gate electrode, and forming a field plate on the first insulating film, the field plate having a first metal layer and a second metal layer having a higher Mohs hardness than the first metal layer. The forming the field plate includes forming a resist mask having an opening, the opening exposing a portion of the first insulating film overlapping the gate electrode, forming the first metal layer and the second metal layer in this order on an upper surface of the resist mask and inside the opening, and removing the resist mask and a portion of the first and second metal layers that are disposed on the resist mask by a lift-off process.