GaN Semiconductor Si Doping via SiO2 Mask Removal
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Solution Overview
Problem
Conventional methods for producing n-type Group III nitride semiconductor products using silane as a dopant gas limit Si doping concentration to around 1×10^18 cm^-3, leading to impaired crystallinity at higher concentrations.
Innovation Solution
A method involving the selective growth of GaN using an SiO2 mask, where the SiO2 layer is removed with buffered hydrofluoric acid, allowing for high-concentration Si doping without compromising crystallinity, by growing a third layer of n-type Group III nitride semiconductor with an Si concentration of 1×10^19/cm^3 or more without supplying an n-type dopant gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silane dopant gas is used to increase Si doping concentration, then n-type doping level increases, but crystallinity deteriorates
Solution Approach 1:
The patent applies preliminary action by forming an SiO2 mask layer on the semiconductor substrate before the main doping process. This mask layer is then selectively removed to create Si-rich regions that serve as dopant sources during subsequent MOCVD growth, enabling high Si concentration without direct silane gas introduction that would harm crystallinity
Solution Approach 2:
The SiO2 mask layer acts as an intermediary substance that enables Si doping without direct contact between silane gas and the semiconductor substrate. The SiO2 is removed by buffered hydrofluoric acid to expose Si that diffuses into the semiconductor during MOCVD, serving as a mediator that achieves doping while preserving crystallinity
2Quantity of substance
If Si doping concentration is increased beyond 1×10^18 cm^-3, then n-type conductivity improves, but manufacturing precision deteriorates
Solution Approach 1:
The patent applies local quality by creating spatially non-uniform Si distribution through the SiO2 mask pattern. The mask is removed selectively in specific regions, causing Si to diffuse locally into the semiconductor substrate only where needed, enabling precise control of doping concentration and location rather than uniform doping throughout
Solution Approach 2:
The patent changes the doping mechanism from direct gas-phase doping to solid-state diffusion from SiO2 layers. By controlling the thickness and pattern of SiO2 masks and the duration of MOCVD growth, the Si diffusion parameters are controlled, achieving precise doping concentration control at high levels that would be impossible with conventional silane doping
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 method achieves high Si concentration doping in n-type Group III nitride semiconductors while maintaining favorable crystallinity, making the product suitable for applications like contact layers in semiconductor devices, such as HFETs, by regulating Si concentration through controlled layer thickness and etching processes.
Implementation Method 1
removing the second layer by wet etching
Implementation Method 2
removal of SiO2 by use of buffered hydrofluoric acid (BHF)
Implementation Method 3
growing a Group III nitride semiconductor on the first layer exposed by the removal of the second layer by MOCVD
Implementation Method 4
the regrown GaN is doped with Si at a high concentration
Data Source
AI summary
The present invention provides a method for producing an n-type Group III nitride semiconductor product having a high Si concentration and exhibiting favorable crystallinity. In the production method, specifically, an AlN buffer layer is formed on a sapphire substrate by MOCVD, and then a first layer (thickness: 2 μm) is formed from undoped GaN on the buffer layer by MOCVD at 1,140° C. Subsequently, a second layer (thickness: 200 nm) is formed from SiO2 on the first layer by plasma CVD, and then the second layer is removed by use of BHF (buffered hydrofluoric acid). Next, a GaN layer (thickness: 50 nm) is grown, by MOCVD at 1,140° C., on the first layer exposed by removal of the second layer without supply of an n-type dopant gas. Thus, on the first layer is provided a third layer formed of n-type GaN doped with Si at a high concentration and exhibiting favorable crystallinity.