SiC Crystal Growth Radial Temperature Gradient Control
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Solution Overview
Problem
Existing methods for manufacturing silicon carbide single crystals, such as HTCVD, fail to effectively suppress the conversion of threading edge dislocations into prismatic plane dislocations and subsequent conversions into basal plane dislocations, which affects the quality of semiconductor devices.
Innovation Solution
A method involving HTCVD with a controlled temperature gradient in the radial direction, specifically 15° C./mm or lower, and strategic management of shear stress regions on the silicon carbide single crystal layer to minimize the areas where high shear stresses overlap, thereby reducing dislocation conversions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HTCVD method is used to grow silicon carbide single crystal, then crystal growth is achieved, but threading edge dislocations are converted into prismatic plane dislocations which further convert into basal plane dislocations
Solution Approach 1:
The patent applies parameter changes by controlling the temperature gradient in the radial direction during HTCVD crystal growth. Specifically, maintaining the temperature gradient at 15°C/mm or lower prevents the conversion of threading edge dislocations into prismatic plane dislocations, and subsequently prevents conversion into basal plane dislocations. This parameter control directly addresses the dislocation conversion problem while enabling successful crystal growth.
2Productivity
If temperature gradient in radial direction is not controlled, then crystal growth proceeds, but dislocation conversions occur affecting device quality
Solution Approach 1:
The patent implements parameter changes by establishing a specific temperature gradient condition (15°C/mm or lower) in the radial direction during crystal growth. This parameter control enables simultaneous achievement of productive crystal growth and low dislocation density, resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The patent applies equipotentiality by creating a uniform temperature distribution in the radial direction through controlled gradient. This uniform thermal field prevents localized stress variations that would otherwise cause dislocation conversions, enabling both efficient growth and high crystal quality.
3Stability of the object's composition
If threading edge dislocations are converted into prismatic plane dislocations, then crystal structure changes, but device performance deteriorates
Solution Approach 1:
The patent uses parameter changes by controlling the temperature gradient to prevent the crystal structure transitions that lead to device performance deterioration. By maintaining the gradient at 15°C/mm or lower, the crystal structure remains stable in the desired configuration, avoiding harmful dislocation conversions.
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 suppresses the conversion of threading edge dislocations into prismatic plane dislocations and prismatic plane dislocations into basal plane dislocations, resulting in improved quality silicon carbide single crystal ingots and wafers suitable for high-performance semiconductor devices.
Implementation Method 1
high temperature chemical vapor deposition (hereinafter called HTCVD or the HTCVD method) is known (see, for example, Patent Document 1). With the HTCVD method, many of basal plane dislocations (may hereinafter be referred to as BPDs) contained in a seed substrate are converted into threading edge dislocations (may hereinafter be referred to as TEDs) by epitaxial growth.
Implementation Method 2
growing the silicon carbide single crystal so that a temperature gradient in a radial direction is a predetermined value or lower
Data Source
AI summary
Provided are a method for manufacturing a silicon carbide single crystal, which can suppress conversion of threading edge dislocations into prismatic plane dislocations and conversion of the prismatic plane dislocations into basal plane dislocations; and a silicon carbide single crystal ingot and a silicon carbide wafer, in which conversion from threading edge dislocations into prismatic plane dislocations and conversion from the prismatic plane dislocations into basal plane dislocations have been suppressed. A silicon carbide single crystal is grown on the surface of a seed substrate by a gas method so that a temperature gradient in the radial direction of the seed substrate takes a predetermined value or lower during the growth. The area of regions T1 to T4, where regions R1 to R3 of a basal plane whose shear stresses exceed critical resolved shear stress, and regions S1 to S4 of a prismatic plane whose shear stresses exceed critical resolved shear stress overlap, is less than a half of the area of a crystal growth surface. Furthermore, the area of the regions T1 to T4 is smaller than the area of regions V1 to V4 where a region R4 of the basal plane whose shear stress does not exceed the critical resolved shear stress overlaps the regions S1 to S4.