GaN Crystal Growth on Silicon via AlN Interlayer
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Solution Overview
Problem
The challenge of growing high-quality gallium nitride (GaN) crystals on silicon substrates is hindered by melt back etching due to the high reactivity between silicon and GaN, and the formation of amorphous aluminum nitride interlayers at low temperatures leads to cracking and further etching issues.
Innovation Solution
A method involving the formation of an interlayer of aluminum nitride or aluminum oxide on a silicon substrate at 350 to 700 degrees C, followed by crystal nucleus distribution and subsequent growth of GaN crystals from these nuclei, using a heat treatment apparatus to control gas supply and temperature for preventing melt back etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an amorphous AlN film is formed at low temperature to prevent substrate melting, then substrate damage is avoided, but the AlN film cracks during GaN growth causing melt back etching
Solution Approach 1:
The patent changes the temperature parameter from low temperature (350-700°C) to high temperature (900-1100°C) during the interlayer formation step. This temperature increase enables the AlN film to form with sufficient crystallinity and mechanical strength to prevent cracking during subsequent GaN growth, while still protecting the silicon substrate from melting through controlled processing conditions
Solution Approach 2:
The patent creates a composite structure consisting of the silicon substrate and the AlN interlayer. The AlN layer acts as a protective barrier with specific thermal and chemical properties that prevent direct interaction between the silicon substrate and GaN, thereby preventing melt back etching while maintaining structural integrity
2Stability of the object's composition
If the AlN interlayer is heated to high temperature to crystallize it, then film strength increases, but the silicon substrate may melt
Solution Approach 1:
The patent optimizes the temperature parameter to a specific range (900-1100°C) that is high enough to crystallize the AlN interlayer and improve its mechanical properties, but controlled through processed time and atmosphere to prevent silicon substrate melting. The temperature is maintained within this narrow window to achieve the desired balance
Solution Approach 2:
The AlN interlayer is formed and crystallized in advance before the GaN crystal growth process. This preliminary high-temperature treatment ensures the interlayer has sufficient strength and structural stability to prevent cracking during the subsequent crystal growth, while the substrate is already protected by the formed interlayer
3Ease of manufacture
If GaN crystals are grown on silicon substrate directly, then device cost decreases, but melt back etching occurs due to high reactivity
Solution Approach 1:
The patent introduces an AlN interlayer as an intermediary substance between the silicon substrate and the GaN crystal. This interlayer serves as a buffer that prevents direct chemical interaction between the reactive silicon substrate and GaN, thereby eliminating melt back etching while still enabling cost-effective growth on silicon substrates
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 prevents melt back etching and allows for the growth of high-quality GaN crystals with controlled crystal nuclei distribution, suppressing substrate reaction and enabling large particle diameter growth.
Implementation Method 1
heating the silicon substrate and the interlayer in an atmosphere containing ammonia or oxygen such that crystal nuclei of the aluminum nitride or the aluminum oxide included in the interlayer are distributed on the silicon substrate
Implementation Method 2
a heat unit configured to heat workpieces received in the processing container
Data Source
AI summary
There is provided a method of growing a gallium nitride-based crystal, including: forming an interlayer including aluminum nitride or aluminum oxide on a silicon substrate at a film forming temperature of 350 to 700 degrees C.; heating the silicon substrate and the interlayer in an atmosphere containing ammonia or oxygen such that crystal nuclei of the aluminum nitride or the aluminum oxide included in the interlayer are distributed on the silicon substrate; and growing gallium nitride-based crystals on the silicon substrate from the crystal nuclei distributed on the silicon substrate.