Composite Substrate With Silicon Coating for Heat Dissipation
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Solution Overview
Problem
Current semiconductor devices face challenges with heat dissipation due to silicon substrates' low thermal conductivity and dielectric properties, leading to power loss in high-frequency regions, and contamination issues from metallic impurities in ceramic sintered substrates used for improved heat conductivity.
Innovation Solution
A composite substrate is created with an inorganic insulating sintered-body substrate having high thermal conductivity and volume resistivity, a silicon coating between the substrate and single-crystal semiconductor thin film, and an intermediate insulating layer to suppress metallic impurity contamination and enhance device characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a ceramic sintered body (silicon nitride or aluminum nitride) is used as a substrate to improve heat conductivity, then thermal conductivity is improved, but metallic impurities (iron and aluminum) contaminate the device fabrication process
Solution Approach 1:
A silicon oxide layer is introduced as an intermediate barrier between the ceramic sintered body substrate and the device fabrication area. This oxide layer prevents metallic impurities (iron and aluminum) from the substrate from contaminating the device fabrication process while allowing the high thermal conductivity of the substrate to be utilized for heat dissipation
2Ease of manufacture
If silicon substrate is used for device fabrication, then device fabrication is straightforward, but heat dissipation is poor due to low thermal conductivity
Solution Approach 1:
The invention uses a composite structure combining a ceramic sintered body substrate (providing high thermal conductivity for heat dissipation) with a silicon oxide layer and single-crystal silicon thin film (providing suitable fabrication properties). This composite approach allows both heat dissipation and ease of fabrication to be achieved simultaneously
3Reliability
If silicon oxide layer is used below device active layer for heat management, then thermal insulation is provided, but thermal conductivity deteriorates due to low thermal conductivity of SiO2
Solution Approach 1:
The invention applies different material properties at different locations: a silicon oxide layer is used immediately below the device active layer where thermal insulation is needed for device reliability, while a ceramic sintered body substrate with high thermal conductivity is used in the bulk for heat dissipation. This local differentiation of material properties resolves the contradiction between thermal insulation and thermal conductivity
4Temperature
If sapphire substrate is used for SOS structure, then heat conductivity is improved and high-frequency power loss is reduced, but cost increases and warpage occurs during heat treatment
Solution Approach 1:
The invention replaces expensive sapphire substrates with ceramic sintered bodies (silicon nitride or aluminum nitride) that provide comparable high thermal conductivity but are more cost-effective and have better mechanical compatibility with silicon devices, reducing both manufacturing cost and warpage issues during heat treatment
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
The solution provides a cost-effective composite substrate with improved heat dissipation and reduced power loss in high-frequency regions, effectively preventing metallic impurity contamination and enhancing device performance.
Implementation Method 1
covering the sintered substrate with a thin layer of oxide, nitride or oxynitride material, between the sintered substrate and the semiconductor film, to restrict leaching of Fe and Al impurities
Implementation Method 2
an inorganic insulating sintered-body substrate having a thermal conductivity of at least 5 W/m·K
Data Source
Figure 1
AI summary
This composite substrate has a single-crystal semiconductor thin film (13) provided to at least the front surface of an inorganic insulating sintered-body substrate (11) having a thermal conductivity of at least 5 W/m·K and a volume resistivity of at least 1×108 Ω·cm. The composite substrate also has, provided between the inorganic insulating sintered-body substrate (11) and the single-crystal semiconductor thin film (13), a silicon coating layer (12) comprising polycrystalline silicon or amorphous silicon. As a result of the present invention, metal impurity contamination from the sintered body can be inhibited, even in a composite substrate in which a single-crystal silicon thin film is provided upon an inexpensive ceramic sintered body which is opaque with respect to visible light, which exhibits an excellent thermal conductivity, and which further exhibits little loss at a high frequency range, and characteristics can be improved.