Nitride Semiconductor Epitaxial Substrate Nitrogen Dissociation Control
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Solution Overview
Problem
The dissociation of nitrogen from nitride semiconductor materials during the growth of epitaxial substrates leads to defects and increased drain leak current in semiconductor devices, particularly due to differences in growth temperatures and nitrogen supply conditions between the nucleus forming layer and the nitride semiconductor layer.
Innovation Solution
A process involving the sequential growth of aluminum nitride (AlN) layers using metal organic chemical vapor deposition (MOCVD), where the upper AlN layer is grown with a higher nitrogen flow rate than the lower layer, and the growth temperature for the nitride semiconductor layer is lower than that of the upper layer, to mitigate nitrogen dissociation and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the growth temperature is increased to improve the growth rate of the nucleus forming layer, then the growth efficiency is improved, but nitrogen dissociation from the surface is accelerated causing interface defects
Solution Approach 1:
The patent applies parameter changes by adjusting the nitrogen source gas flow rate to be higher during the growth of the upper AlN layer compared to the lower AlN layer. This compensates for nitrogen dissociation at elevated temperatures by increasing nitrogen supply, thereby maintaining stoichiometry and preventing interface defects while allowing higher growth temperatures for improved productivity.
2Manufacturing precision
If the nitrogen source gas flow rate is increased to prevent nitrogen dissociation, then the crystal quality is improved, but the process complexity increases
Solution Approach 1:
The patent applies local quality by differentiating the nitrogen source gas flow rate for different layers: a higher flow rate is used specifically during the growth of the upper AlN layer that is exposed to high temperature, while a lower flow rate suffices for the lower AlN layer. This targeted approach improves crystal quality where needed without unnecessarily complicating the overall 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
This approach effectively reduces defects and drain leak current by maintaining a higher nitrogen composition in the upper layer, enhancing the crystal quality and reducing nitrogen dissociation, thereby improving the performance of nitride semiconductor devices.
Implementation Method 1
The process includes steps of sequentially growing a lower layer, an upper layer, and a nitride semiconductor layer on a substrate by the metal organic chemical vapor deposition (MOCVD) technique
Implementation Method 2
the nucleus forming layer in a surface thereof is exposed within a condition of a high temperature, which accelerates the dissociation of nitrogen (N) from the surface of the nucleus forming layer and causes defects in an interface
Data Source
AI summary
A process of forming a nucleus fanning layer in a nitride semiconductor epitaxial substrate is disclosed. The process includes steps of growing: a lower layer of the nucleus forming layer on a substrate; an upper layer of the nucleus thrilling layer on the lower layer; and a nitride semiconductor layer each by the metal organic chemical vapor deposition (MOCVD) technique. The growth of the nitride semiconductor layer is done at a temperature lower than a growth temperature for the upper layer, and the growth of the upper layer is done by supplying ammonia (NH3) at a flow rate greater than the flow rate of ammonia (NH3) timing the growth of the lower layer.