Nitride Crystal Substrate Mosaic Growth via Vapor and Liquid Phase

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Solution Overview

Problem

There is a need for a method to manufacture high-quality nitride crystal substrates with larger diameters, as existing techniques struggle to produce substrates exceeding 2 inches in diameter while maintaining low defect density and impurity concentration.

Innovation Solution

A method involving the arrangement of seed crystal substrates in a planar appearance with parallel main surfaces and contacting lateral surfaces, followed by vapor-phase growth to combine them, liquid-phase growth to smooth the surface, and subsequent vapor-phase growth to enhance the substrate quality, allowing for increased diameter and improved substrate quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If a single large-diameter substrate is used for crystal growth, then the diameter of the nitride crystal substrate can be increased, but the quality (low defect density and impurity concentration) deteriorates

Engineering Contradiction:

Improvediameter of substrateVSAvoidquality of nitride crystal substrate

Core Design Contradiction:

Length of stationary objectVSManufacturing precision

Solution Approach 1:

The invention divides a large-diameter substrate into multiple smaller seed crystal substrates arranged in a mosaic pattern. Each seed substrate is grown separately to ensure high quality, then combined through vapor-phase growth to form a large-diameter substrate that maintains low defect density and impurity concentration throughout.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention performs preliminary crystal growth on multiple small seed substrates before combining them. This allows each seed substrate to be optimized for high quality independently, and the vapor-phase growth step combines them while maintaining overall substrate quality.

Inventive Principle:

Principle #10Preliminary action

2Length of stationary object

If multiple seed crystal substrates are combined, then the diameter of the substrate can be increased, but surface irregularities (grooves at combined parts) increase

Engineering Contradiction:

Improvediameter of substrateVSAvoidsurface smoothness

Core Design Contradiction:

Length of stationary objectVSShape

Solution Approach 1:

The invention changes the growth parameters between vapor-phase and liquid-phase growth. Vapor-phase growth combines the seed substrates, creating grooves at combined parts. Liquid-phase growth then fills these grooves and smooths the surface, achieving a uniformly smooth finish across the entire large-diameter substrate.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention utilizes phase transitions by switching from vapor-phase growth (for combining substrates) to liquid-phase growth (for smoothing surfaces). The liquid phase effectively fills and smooths the grooves created during vapor-phase combining, resulting in a uniformly smooth surface.

Inventive Principle:

Principle #36Phase transitions

3Strength

If vapor-phase growth is used to combine seed substrates, then the substrates can be joined, but grooves form at the combined parts

Engineering Contradiction:

Improvebonding of seed crystal substratesVSAvoidsurface profile

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The invention uses liquid-phase growth as an intermediary process between vapor-phase growth (which bonds the substrates) and final substrate completion. The liquid-phase growth acts as a mediator that fills the grooves created during vapor-phase bonding, smoothing the surface while preserving the strong bonds formed earlier.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 method enables the production of high-quality nitride crystal substrates with larger diameters, reducing the variation of the off-angle in the substrate's main surface, minimizing screw dislocations, and improving productivity by effectively smoothing the surface and reducing the need for additional processing steps.

Implementation Method 1

growing a first crystal film using a vapor-phase growth method on a surface of the plurality of seed crystal substrates arranged in the planar appearance

Methodology Applied

Scientific EffectVapor-phase growth: Chemical Vapour Deposition

Implementation Method 2

growing a second crystal film using a liquid-phase growth method on a main surface of the combined substrate so as to be embedded in a groove that exists at a combined part of the seed crystal substrates

Methodology Applied

Scientific EffectLiquid-phase growth:

Data Source

PatentUS10260165B2Method for manufacturing nitride crystal substrate and substrate for crystal growth

Publication Date: 2019.04.16 SUMITOMO CHEM CO LTD

AI summary

There is provided a method for manufacturing a nitride crystal substrate, including: arranging a plurality of seed crystal substrates made of a nitride crystal in a planar appearance, so that their main surfaces are parallel to each other and their lateral surfaces are in contact with each other; growing a first crystal film using a vapor-phase growth method on a surface of the plurality of seed crystal substrates arranged in the planar appearance, and preparing a combined substrate formed by combining the adjacent seed crystal substrates each other by the first crystal film; growing a second crystal film using a liquid-phase growth method on a main surface of the combined substrate so as to be embedded in a groove that exists at a combined part of the seed crystal substrates, and preparing a substrate for crystal growth having a smoothened main surface; and growing a third crystal film using the vapor-phase growth method, on the smoothed main surface of the substrate for crystal growth.