SiC Composite Substrate Warpage Control via Oxide Film Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The commercialization of silicon carbide (SiC) composite substrates is hindered by high costs due to poor crystallinity and complex production processes, as well as issues with warpage, which makes them unsuitable for precision semiconductor fabrication.
Innovation Solution
A method involving a monocrystalline SiC layer on a polycrystalline SiC substrate is produced by using a silicon support substrate with a silicon oxide film, where the oxide film is partially removed to impart warpage, allowing for the deposition of polycrystalline SiC and subsequent removal of the support substrate, thereby canceling out thermal and internal stresses and reducing warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional bonding methods using ceramic or metal intervening materials are used, then bonding between monocrystalline SiC layer and polycrystalline SiC substrate is achieved, but device fabrication becomes difficult due to insulation or metallic impurity contamination
Solution Approach 1:
The patent removes the problematic intervening materials (ceramics and metals) entirely from the bonding interface. Instead, it uses a silicon oxide film formed directly on the silicon support substrate as the bonding interface, eliminating the insulating or contaminating layers while maintaining strong bonding capability through direct oxidation bonding.
Solution Approach 2:
The silicon oxide film acts as an intermediary layer formed in situ on the silicon support substrate surface. This oxide film provides a bonding interface that avoids the drawbacks of ceramic or metal interveners while enabling strong adhesion between the monocrystalline SiC layer and the support substrate through controlled oxidation and bonding processes.
2Strength
If silicon oxide faces are used for bonding, then bonding between monocrystalline SiC layer and polycrystalline SiC substrate is achieved, but separation takes excessive time due to strong bonding
Solution Approach 1:
The patent extracts the problematic thick silicon oxide bonding layer used in conventional methods and replaces it with a thin silicon oxide film formed in situ on the silicon support substrate. This thin film provides sufficient bonding strength during fabrication but allows rapid separation afterward, eliminating the excessive separation time issue.
Solution Approach 2:
The patent changes the thickness parameter of the silicon oxide film from the thick layers used in conventional bonding to a thin film configuration. This parameter change maintains adequate bonding strength for device fabrication while enabling fast separation through HF etching, resolving the time loss problem.
3Manufacturing precision
If polycrystalline SiC is deposited on monocrystalline SiC layer, then composite substrate structure is formed, but warpage occurs due to thermal expansion difference
Solution Approach 1:
The patent uses the silicon support substrate with its specific thermal expansion properties as a counterweight to compensate for the warpage induced by thermal expansion differences during polycrystalline SiC deposition. The support substrate's mechanical properties and thermal characteristics balance the stress, maintaining substrate flatness.
Solution Approach 2:
The patent creates a composite structure consisting of the silicon support substrate, thin silicon oxide film, monocrystalline SiC layer, and deposited polycrystalline SiC. This composite material system is designed to balance thermal expansion differences and mechanical stresses, preventing warpage while enabling the desired substrate structure formation.
4Reliability
If monocrystalline SiC substrates are produced using sublimation process, then high purity monocrystalline SiC is obtained, but production cost becomes very high due to exacting conditions
Solution Approach 1:
The patent introduces a silicon support substrate with a silicon oxide film as an intermediary platform for growing the monocrystalline SiC layer. This intermediary approach allows growth under more manageable conditions compared to direct sublimation, reducing process complexity while maintaining substrate quality through the controlled oxide interface.
Solution Approach 2:
The patent uses a silicon support substrate as a template or copy platform upon which the monocrystalline SiC layer is grown. This copying approach on a familiar silicon substrate platform simplifies the production process compared to direct monocrystalline SiC substrate fabrication, while the resulting SiC layer retains the required high quality characteristics.
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 SiC composite substrates with excellent shape and reduced warpage, facilitating the fabrication of high-quality semiconductor devices at lower costs and improving handling and precision.
Implementation Method 1
some or all of the thickness of the silicon oxide film over some region or all of the back side of the support substrate in the monocrystalline SiC layer carrier is removed by chemical etching so as to impart warpage to the monocrystalline SiC layer carrier
Implementation Method 2
depositing polycrystalline SiC onto the monocrystalline SiC layer by chemical vapor deposition so as to form a polycrystalline SiC substrate
Implementation Method 3
the support substrate is physically removed by grinding or the like, thereby obtaining a SiC composite substrate
Data Source
Figure 1(a)~1(i)
Figure 2A~4
AI summary
Provided is a method for producing a SiC composite substrate 10 having a single crystal SiC layer 12 on a polycrystalline SiC substrate 11, wherein after the single crystal SiC layer 12 is provided on the front surface of a holding substrate 21 comprising Si and having a silicon oxide film 21a on the front and back surfaces thereof to produce a single crystal SiC layer supporting body 14, a part or all of the thickness of the silicon oxide film 21a on one area or all of the back surface of the holding substrate 21 in the single crystal SiC layer supporting body 14 is removed to impart warpage to the single crystal SiC layer supporting body 14', then polycrystalline SiC is deposited on the single crystal SiC layer 12 by chemical vapor deposition to form the polycrystalline SiC substrate 11, and thereafter the holding substrate is physically and/or chemically removed. By means of the present invention, it is possible to obtain a SiC composite substrate having a single crystal SiC layer with good crystallinity and little warpage with a simple production process.