GaN HEMT Diffusion Barrier on Silicon Substrate
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Solution Overview
Problem
GaN devices on silicon carbide substrates are costly due to the high expense of silicon carbide substrates, and they suffer from parasitic losses and performance degradation due to gallium and aluminum diffusion during epitaxial growth.
Innovation Solution
Formation of doped regions on a silicon substrate using ion implantation or doped semiconductor layers to prevent gallium and aluminum diffusion, creating a diffusion barrier that reduces parasitic losses and enhances RF performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GaN devices are fabricated on silicon carbide substrates, then device performance is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent substitutes expensive silicon carbide substrates with cheaper silicon substrates. The silicon substrate serves as a cost-effective alternative that, while having different material properties, can still support GaN device fabrication when combined with the diffusion barrier layer to prevent unwanted material diffusion.
Solution Approach 2:
The patent introduces a diffusion barrier layer as an intermediary between the silicon substrate and the GaN epitaxial layers. This intermediate layer prevents gallium and aluminum diffusion into the silicon substrate, enabling the use of cheap silicon substrates while maintaining device performance that would otherwise require expensive silicon carbide substrates.
2Device complexity
If epitaxial growth is performed without diffusion barriers, then manufacturing process is simplified, but parasitic losses increase due to gallium and aluminum diffusion
Solution Approach 1:
The patent applies preliminary action by forming the diffusion barrier layer on the silicon substrate before performing epitaxial growth of the GaN layers. This pre-formed barrier prevents gallium and aluminum diffusion during the subsequent high-temperature epitaxial process, reducing parasitic losses without complicating the overall manufacturing flow.
Solution Approach 2:
The diffusion barrier layer acts as an intermediary that blocks the diffusion of gallium and aluminum atoms from the epitaxial layers into the silicon substrate. This intermediary layer eliminates the harmful diffusion effect while adding minimal complexity to the manufacturing process.
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 solution reduces parasitic losses and improves RF performance by preventing gallium and aluminum diffusion into the substrate during epitaxial growth, making GaN devices more cost-effective and efficient.
Implementation Method 1
Formation of doped regions on a silicon substrate using ion implantation
Implementation Method 2
doped regions functioning as enhanced resistivity regions or diffusion barriers... prevent gallium and aluminum diffusion
Implementation Method 3
a transistor over the upper surface of the base semiconductor substrate and formed from a plurality of epitaxially-grown semiconductor layers
Data Source
AI summary
A semiconductor device includes a base substrate, a doped region at an upper surface of the base substrate, and a transistor over the upper surface of the base substrate and formed from a plurality of epitaxially-grown semiconductor layers. The doped region includes one or more ion species, and has a lower boundary above a lower surface of the base substrate. The base substrate may be a silicon substrate, and the transistor may be a GaN HEMT formed from a plurality of heteroepitaxial layers that include aluminum nitride and/or aluminum gallium nitride. The doped region may be a diffusion barrier region and/or an enhanced resistivity region. The ion species may be selected from phosphorus, arsenic, antimony, bismuth, argon, helium, nitrogen, and oxygen. When the ion species includes oxygen, the doped region may include a silicon dioxide layer formed from annealing the doped region after introduction of the oxygen.