GaN Laminate Step-Terrace Structure for HVPE Surface Flatness
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Solution Overview
Problem
The challenge is to develop a GaN laminate with a thick GaN layer grown on a GaN substrate using hydride vapor phase epitaxy (HVPE) that maintains high quality and surface flatness, essential for improving semiconductor device performance, particularly in achieving a thickness of 10 μm or more while avoiding the formation of complex ridge-like structures that may degrade performance.
Innovation Solution
A GaN laminate is created with a GaN substrate having a low index crystal plane and a GaN layer grown via HVPE, where the growth temperature is set between 1050°C and 1200°C, forming a step-terrace structure on the surface with steps of multiple molecular layers and alternating terraces, which enhances surface flatness and prevents the formation of macro step-macro terraces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the GaN layer thickness is increased to 10 μm or more to improve withstand voltage, then the semiconductor device performance is improved, but the surface flatness deteriorates due to formation of macro step-macro terraces
Solution Approach 1:
The invention changes the growth temperature parameter to 1050°C or higher during HVPE growth, which fundamentally alters the growth mechanism to form a step-terrace structure instead of macro step-macro terraces. This parameter change enables simultaneous achievement of thick layer growth (10 μm or more) and maintained surface flatness, resolving the contradiction between withstand voltage improvement and surface flatness deterioration
Solution Approach 2:
The invention creates a specific local surface structure (step-terrace structure with steps of multiple molecular layers) that differs from the conventional macro step-macro terrace structure. This local structural quality enables the surface to maintain flatness while accommodating thick layer growth, thus resolving the contradiction between thickness and surface quality
2Productivity
If HVPE is used to achieve high growth rate for thick GaN layer, then productivity is improved, but the surface structure becomes complex with macro step-macro terraces
Solution Approach 1:
By changing the growth temperature to 1050°C or higher, the invention transforms the surface structure formed during high-rate HVPE growth from complex macro step-macro terraces to a simpler step-terrace structure. This parameter change maintains the high productivity advantage of HVPE while eliminating the harmful surface complexity
Solution Approach 2:
The invention converts the potentially harmful macro step-macro terrace structure into a beneficial step-terrace structure by adjusting the growth temperature. The high growth rate of HVPE, which originally caused surface complexity, is transformed into an advantage that produces a controlled step-terrace structure with improved surface flatness when grown at 1050°C or higher
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 results in a GaN laminate with improved surface flatness, as evidenced by a reduced root mean square (rms) value of surface roughness, facilitating easier integration of additional layers and potentially enhancing semiconductor device performance by avoiding the detrimental effects of macro step-macro terraces.
Implementation Method 1
a GaN layer epitaxially grown on the main surface of the GaN substrate
Implementation Method 2
hydride vapor phase epitaxy (HVPE) capable of obtaining a high growth rate
Implementation Method 3
epitaxially growing the GaN layer, the GaN layer is grown, with a growth temperature set to 1050° C. or more and 1200° C. or less
Data Source
AI summary
To provide a new GaN laminate obtained by growing a GaN layer on a GaN substrate by HVPE, including: a GaN substrate containing GaN single crystal and having a low index crystal plane as c-plane closest to a main surface; and a GaN layer epitaxially grown on the main surface of the GaN substrate, and having a thickness of 10 nm or more, wherein a surface of the GaN layer has a step-terrace structure in which a step having a height of equal to or more than a plurality of molecular layers of GaN and extending in a predetermined direction and a terrace are alternately arranged.