MOCVD Susceptor Temperature Gradient for Nitride Semiconductor Uniformity
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Solution Overview
Problem
The formation of nitride semiconductor layers in semiconductor substrates often results in non-uniform thickness and composition, particularly in aluminum gallium nitride (AlGaN) layers, leading to inhomogeneous performance of field effect transistors (FETs) due to variations in thickness and aluminum composition.
Innovation Solution
A process using metal organic chemical vapor deposition (MOCVD) with a susceptor having a temperature gradient, where the center is set higher than the periphery, to control the flow of source gases and grow nitride semiconductor layers, specifically aluminum gallium nitride (AlGaN) and indium aluminum gallium nitride (InAlGaN), to achieve uniform thickness and composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional MOCVD is used to grow nitride semiconductor layers, then the production process is simple, but the thickness and composition become non-uniform across the substrate
Solution Approach 1:
The patent applies local quality by creating different temperature zones across the susceptor surface. The susceptor is designed with a temperature gradient where the center region is heated to a higher temperature than the peripheral regions. This localized temperature differentiation compensates for the non-uniform gas flow distribution, ensuring uniform deposition of AlGaN layers across the entire substrate surface despite variations in source gas flow rates at different locations.
Solution Approach 2:
The patent changes the temperature parameter spatially across the susceptor surface. By adjusting the heating power distribution to create a temperature gradient (higher at center, lower at periphery), the process compensates for the inherent non-uniformity in source gas flow. This parameter modification transforms the deposition conditions to achieve uniform layer thickness and composition across the substrate.
2Manufacturing precision
If uniform source gas flow is used across the substrate, then the process is simple, but the thickness and aluminum composition vary due to temperature distribution
Solution Approach 1:
The patent applies local quality by creating different temperature zones across the susceptor surface. The susceptor is designed with a temperature gradient where the center region is heated to a higher temperature than the peripheral regions. This localized temperature differentiation compensates for the non-uniform gas flow distribution, ensuring uniform deposition of AlGaN layers across the entire substrate surface despite variations in source gas flow rates at different locations.
Solution Approach 2:
The patent changes the temperature parameter spatially across the susceptor surface. By adjusting the heating power distribution to create a temperature gradient (higher at center, lower at periphery), the process compensates for the inherent non-uniformity in source gas flow. This parameter modification transforms the deposition conditions to achieve uniform layer thickness and composition.
3Reliability
If the center and periphery are heated equally, then the heating control is simple, but the threshold voltage shows large dispersion
Solution Approach 1:
The patent applies local quality by creating different temperature zones across the susceptor surface. The susceptor is designed with a temperature gradient where the center region is heated to a higher temperature than the peripheral regions. This localized temperature differentiation compensates for the non-uniform gas flow distribution, ensuring uniform deposition of AlGaN layers across the entire substrate surface despite variations in source gas flow rates at different locations.
4Reliability
If conventional heating is used without temperature gradient, then the process is simple, but the leak current increases due to composition variation
Solution Approach 1:
The patent applies local quality by creating different temperature zones across the susceptor surface. The susceptor is designed with a temperature gradient where the center region is heated to a higher temperature than the peripheral regions. This localized temperature differentiation compensates for the non-uniform gas flow distribution, ensuring uniform deposition of AlGaN layers across the entire substrate surface despite variations in source gas flow rates at different locations.
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 effectively suppresses the dispersion in thickness and aluminum composition of the semiconductor layers, resulting in improved uniformity of the threshold voltage and reduced leak current, enhancing the performance and reliability of FETs.
Implementation Method 1
The nitride semiconductor materials are grown by metal organic chemical vapor deposition (MOCVD) supplied with source gases
Implementation Method 2
Heaters are accompanied with those center, middle, and periphery of the susceptor for adjusting temperature distribution thereof
Data Source
AI summary
A process of forming a semiconductor device by use of a MOCVD technique is disclosed. The semiconductor device, which is made of primarily nitride semiconductor materials, includes a GaN channel layer, an AlGaN barrier layer, and a GaN cap layer on a substrate. The barrier layer and the cap layer are grown under a gradient temperature condition where the upstream side of the substrate with respect to the flow of the MOCVD source gases is at a higher temperature as compared with the temperature at the downstream side of the substrate with respect to the flow of the source gases.