Silicon Nitride Substrate Grain Boundary Control
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Solution Overview
Problem
Silicon nitride substrates often exhibit insufficient insulating properties despite meeting current leakage value criteria, due to variations in the abundance ratio of silicon nitride crystal grains to the grain boundary phase in the substrate's thickness direction.
Innovation Solution
A silicon nitride substrate with a controlled ratio of grain boundary phase to substrate thickness, incorporating rare earth elements, magnesium, and titanium as sintering aids, ensuring a dielectric strength mean value of 15 kV/mm or more and a volume resistivity of 60 × 10^12 Ωm or more, while maintaining thermal conductivity of 50 W/m·K or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the current leakage value is controlled to meet insulating criteria, then insulating properties are improved, but variations in insulating properties due to grain boundary phase distribution remain insufficient
Solution Approach 1:
The patent applies local quality by controlling the grain boundary phase distribution specifically in the thickness direction of the substrate. By making the grain boundary phase occupy 10-30% of the total thickness, the invention creates a localized structural characteristic that ensures uniform insulating properties throughout the substrate, addressing the variation problem while maintaining overall insulating performance.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the ratio of grain boundary phase thickness to substrate thickness within the range of 0.10-0.30. This quantitative parameter control transforms the insulating properties from variable to stable, ensuring that the abundance ratio of crystal grains to grain boundary phase remains consistent throughout the substrate thickness.
2Temperature
If the substrate is thinned to improve heat dissipation, then thermal resistance is reduced, but insulating properties may be compromised
Solution Approach 1:
The patent resolves this contradiction by changing the critical parameter of grain boundary phase ratio to 10-30% of substrate thickness. This parameter optimization allows thin substrates to maintain both excellent heat dissipation (due to reduced thermal resistance) and superior insulating properties (due to controlled grain boundary phase distribution that prevents current leakage).
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 configuration results in a highly reliable silicon nitride substrate with reduced variations in insulating properties, enabling effective heat dissipation and supporting high-voltage semiconductor elements with improved reliability and thermal stability.
Implementation Method 1
substrates having a thermal conductivity of 50 W/m·K or more are being developed as silicon nitride substrates... it is possible to lower the thermal resistance by thinning the substrate, heat dissipation (heat radiating property) is improved
Data Source
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AI summary
The invention is characterized in that, in a silicon nitride substrate comprising a grain boundary phase with silicon nitride crystal particles and having a heat conductivity of 50W/m·K or greater, the sectional structure of the silicon nitride substrate has a ratio (T2/T1) of 0.01 to 0.30 between the thickness T1 of the silicon nitride substrate and the total length T2 of the grain boundary phase in the thickness direction, and a variation in the dielectric strength of 15% or less from the mean value, as measured by the four terminal method, in which electrodes are brought into contact with the front and the back of the substrate. In addition, a dielectric strength mean value of 15 kv/mm or greater is desirable. According to this constitution, the silicon nitride substrate having a small dielectric strength variation, and the silicon nitride circuit substrate using the same, are obtained.