Flowable Dielectric Pit Filling for GaN HEMT Yield
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Solution Overview
Problem
The presence of pits on ceramic substrates used in semiconductor fabrication reduces the manufacturing yield of GaN-based semiconductor devices, as material layers formed on these substrates are also formed within the pits, leading to defects and reduced performance.
Innovation Solution
A method involving the formation of a flowable dielectric material on the substrate, which is then heat-treated to reflow and fully fill the pits, followed by a planarization process to expose a flat surface, allowing for the subsequent deposition of GaN-based semiconductor layers without pit-related defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flowable dielectric material is formed and heat-treated to reflow into pits, then manufacturing yield is improved by eliminating pit-related defects, but process complexity increases due to additional fabrication steps
Solution Approach 1:
A flowable dielectric material is formed over the substrate before subsequent semiconductor fabrication steps, and heat treatment is performed to reflow this material into pits beforehand. This preliminary action fills defects that would otherwise cause problems during later processing, thereby improving manufacturing yield without complicating the core semiconductor fabrication process
Solution Approach 2:
The flowable dielectric material serves as an intermediary substance that is introduced to mediate between the defective substrate surface and the subsequent semiconductor layers. This intermediary material fills the pits and provides a planarized surface, allowing subsequent fabrication steps to proceed without being affected by the underlying substrate defects
2Reliability
If a flowable dielectric material is deposited to fully fill pits, then manufacturing yield is improved, but material consumption increases
Solution Approach 1:
The dielectric material is formulated with specific flow characteristics and the heat treatment is optimized to achieve complete pit filling with minimal excess material. By controlling parameters such as material viscosity, deposition thickness, and reflow temperature, the process ensures that just enough material is consumed to fill the pits without significant waste
Solution Approach 2:
The flowable dielectric material undergoes a phase transition during heat treatment, changing from a solid or semi-solid deposited state to a liquid-like reflow state that enables it to flow into and completely fill the pits. This phase transition allows the material to self-adjust and fill defect volumes efficiently, ensuring complete pit filling while minimizing the initial material deposition required
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 enhances the manufacturing yield by eliminating pit-related defects and providing a planar surface for semiconductor processes, reducing manufacturing costs and improving the quality of GaN-based semiconductor devices like HEMTs.
Implementation Method 1
performing a heat treatment so that the flowable dielectric material reflows into and fully fills the pit
Implementation Method 2
performing a planarization process to remove a portion of the flowable dielectric material outside of the pit and expose the upper surface of the substrate
Data Source
AI summary
A semiconductor device includes a substrate, a flowable dielectric material and a GaN-based semiconductor layer. The substrate has a pit exposed from an upper surface of the substrate, the flowable dielectric material fully fills the pit, and the GaN-based semiconductor layer is disposed over the substrate and the flowable dielectric material.