AlN Buffer Layer Growth for Low-Leakage III-Nitride on Silicon
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Solution Overview
Problem
The diffusion of group III elements into silicon substrates during the growth of group III nitride semiconductor layers through an AlN buffer layer reduces the resistivity of the substrate surface, leading to potential current leaks and increased parasitic capacitance.
Innovation Solution
The method involves growing a first AlN buffer layer at a low temperature of 400° C. to 600° C., followed by a second AlN buffer layer at a higher temperature of 900° C. to 1200° C., and subsequently growing the group III nitride semiconductor layer at varying temperatures to suppress the diffusion of group III elements into the silicon substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If AlN buffer layer is grown at high temperature (900°C or more) to improve crystallinity, then the crystallinity of AlN buffer layer is improved, but group III elements diffuse into Si substrate reducing surface resistivity
Solution Approach 1:
The AlN buffer layer growth process is divided into two distinct stages: a first growth stage at low temperature (400-600°C) to prevent element diffusion, and a second growth stage at high temperature (900-1200°C) to improve crystallinity. This segmentation allows each stage to optimize for its specific purpose without compromising the other.
Solution Approach 2:
The first AlN buffer layer is grown preliminarily at low temperature to create a protective barrier on the Si substrate surface before the high-temperature second growth stage. This preliminary action prevents group III elements from diffusing into the substrate during the subsequent high-temperature crystallization process.
2Object-affected harmful factors
If AlN buffer layer is grown at low temperature (400-600°C) to suppress diffusion of group III elements, then diffusion into Si substrate is suppressed, but crystallinity of AlN buffer layer deteriorates
Solution Approach 1:
The growth process is segmented into two temperature stages, allowing the system to achieve both low-temperature benefits (suppressing diffusion) and high-temperature benefits (improving crystallinity) through sequential processing rather than requiring a single compromise temperature.
Solution Approach 2:
The growth process employs periodic temperature variation, alternating between low-temperature growth phases and high-temperature crystallization phases. This periodic action enables the system to dynamically switch between preventing diffusion and improving crystal quality.
3Productivity
If group III nitride semiconductor layer is grown on Si substrate through AlN buffer layer, then large-diameter high-quality bulk single crystal Si substrate can be used for mass production, but dislocation density increases due to lattice mismatch
Solution Approach 1:
The AlN buffer layer serves as an intermediary between the Si substrate and the group III nitride semiconductor layer. This intermediate layer gradually transitions the lattice structure, reducing the abrupt mismatch between Si and GaN/AlN and thereby minimizing dislocation formation while enabling mass production on Si 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 maintains the crystallinity of the AlN buffer and group III nitride semiconductor layers while preventing a reduction in the resistivity of the silicon substrate, thereby improving the quality and reliability of the semiconductor substrate.
Implementation Method 1
growing a first AlN buffer layer on an Si substrate at a first growth temperature of 400° C. to 600° C.
Implementation Method 2
growing a second AlN buffer layer on the first AlN buffer layer at a second growth temperature of 900° C. to 1200° C.
Implementation Method 3
applying heat treatment to the Si substrate
Implementation Method 4
growing a group III nitride semiconductor layer on the second AlN buffer layer
Data Source
AI summary
A method for manufacturing a group III nitride semiconductor substrate, that includes: growing a first AlN buffer layer on an Si substrate at a first growth temperature; growing a second AlN buffer layer on the first AlN buffer layer at a second growth temperature higher than the first growth temperature; and growing a group III nitride semiconductor layer on the second AlN buffer layer, wherein an Al raw material and an N raw material are alternately repeatedly fed in the growing the first AlN buffer layer.