Silicon Carbide Single Crystal L Dislocation Control
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Solution Overview
Problem
High-quality silicon carbide (SiC) single crystal wafers with low dislocation density are not effectively produced, leading to unsuppressed leakage current issues in device production, as existing methods fail to differentiate between spiral dislocations based on distortion magnitude.
Innovation Solution
The method involves producing SiC single crystals with a spiral dislocation density of L dislocations ≤300/cm², where the burgers vector b satisfies b>+1/3, and growing SiC crystals on substrates with specific off-angles to the {0001} plane, distinguishing between L and nL dislocations to control leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the density of spiral dislocation is set to the specified value or lower (2500 cm−2), then the manufacturing precision is improved, but the leakage current is not suppressed
Solution Approach 1:
The patent segments the classification of spiral dislocations by introducing the concept of L dislocations with specific burgers vector magnitudes (b>+1/3). This segmentation allows differentiation between dislocation types that have different impacts on leakage current, enabling selective control of dislocation density to suppress leakage current while maintaining acceptable manufacturing precision.
Solution Approach 2:
The patent changes the parameter criteria for acceptable dislocation density from a general threshold (2500 cm−2) to a more specific parameter based on burgers vector magnitude (b>+1/3) and a lower density threshold (≤300 cm−2). This parameter change enables more precise control over the relationship between dislocation density and leakage current suppression.
2Ease of manufacture
If existing methods are used to produce SiC single crystal, then the production process is simple, but the leakage current cannot be suppressed
Solution Approach 1:
The patent modifies the production process by implementing specific parameter controls: (1) selecting substrates with off-angles within 10 degrees in the <1120> direction with respect to the {0001} plane, and (2) controlling L dislocation density to ≤300 cm−2. These parameter changes enable leakage current suppression while maintaining relative simplicity in the production process.
Solution Approach 2:
The patent applies preliminary action by pre-selecting substrates with specific off-angle orientations before crystal growth. This preliminary selection of substrate orientation prepares the system in advance to suppress leakage current during the subsequent crystal growth process, eliminating the need for complex post-processing adjustments.
3Object-generated harmful factors
If the density of L dislocation is reduced to ≤300 cm−2, then the leakage current is suppressed, but the manufacturing complexity increases
Solution Approach 1:
The patent simplifies the control approach by establishing a clear parameter threshold (L dislocation density ≤300 cm−2) and a specific substrate orientation criterion (off-angle within 10 degrees in <1120> direction). These well-defined parameter changes provide straightforward control criteria that reduce manufacturing complexity despite the stricter requirements.
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 high-quality SiC single crystals suitable for device production by suppressing leakage current, with the density of L dislocations ≤300/cm², ensuring effective device performance.
Implementation Method 1
growing the silicon carbide single crystal on the surface of the substrate as a seed crystal
Data Source
AI summary
A silicon carbide single crystal includes a spiral dislocation. The spiral dislocation includes a L dislocation having a burgers vector defined as b, which satisfies an equation of b><0001>+1/3<11-20>. The L dislocation has a density equal to or lower than 300 dislocations/cm2, preferably, 100 dislocations/cm2, since the L dislocation has large distortion and causes generation of leakage current. Thus, the silicon carbide single crystal with high quality is suitable for a device production which can suppress the leakage current.