Biaxially Oriented SiC Substrate for Low-Warp Wafer Flatness
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Solution Overview
Problem
Warping in SiC substrates during the manufacturing process of SiC power devices is a significant issue, leading to breakages and poor chucking during polishing and manufacturing of semiconductor apparatuses, which existing methods have not adequately addressed.
Innovation Solution
A SiC substrate with a biaxially oriented SiC layer, where the difference between maximum and minimum Raman shift values for the transverse acoustic branch is controlled to 0.50 cm^-1 or less, achieved by measuring at 1 mm intervals on orthogonal lines, and incorporating specific nitrogen and rare earth element concentrations to reduce in-plane nitrogen and elastic strain distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SiC substrates are used, then manufacturing process is simple, but warp occurs leading to breakages and poor chucking
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Raman shift value (a physical parameter characterizing crystal structure) to within 0.50 cm⁻¹ of the transverse acoustic branch peak. This parameter control ensures uniform crystal orientation and reduces internal stress, thereby minimizing substrate warp without requiring complex structural modifications. The biaxial orientation specification further refines this parameter control to achieve the desired stability.
2Manufacturing precision
If substrate warp is reduced by conventional methods, then some improvement is achieved, but breakages still occur during polishing and poor chucking during manufacturing
Solution Approach 1:
The patent applies preliminary action by controlling the Raman shift value and biaxial orientation during substrate fabrication, before the polishing and manufacturing processes. This pre-control of crystal structure parameters prevents warp development that would otherwise occur during subsequent manufacturing steps, thereby eliminating breakages during polishing and ensuring proper chucking without requiring additional corrective measures.
3Reliability
If Raman shift control is implemented, then warp is reduced, but measurement and control complexity increases
Solution Approach 1:
The patent replaces complex mechanical warp measurement and control systems with Raman spectroscopy, an optical characterization method. By measuring the Raman shift value of the transverse acoustic branch peak, the patent provides a non-contact, precise method to control substrate uniformity. This substitution simplifies the overall control process while achieving superior warp reduction compared to traditional mechanical measurement approaches.
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 reduces warp in SiC substrates, enhancing their stability and suitability for semiconductor manufacturing processes.
Implementation Method 1
a difference between a maximum value kmax and a minimum value kmin of a Raman shift value is 0.50 cm−1 or less
Implementation Method 2
incorporating specific nitrogen and rare earth element concentrations to reduce in-plane nitrogen and elastic strain distributions
Data Source
Figure 1~2(c)
Figure 3~4
Figure 5~6
AI summary
There is provided a SiC substrate in which warp is small. The SiC substrate includes a biaxially oriented SiC layer, and, in a Si surface and a C surface of the SiC substrate, a difference between a maximum value kmax and a minimum value kmin of a Raman shift value is 0.50 cm-1 or less. The Raman shift value is obtained by, in the Si surface of the SiC substrate, measuring the Raman shift value indicating a peak corresponding to a transverse acoustic branch of a Raman spectrum at 1 mm intervals on two straight lines passing through a central point of the Si surface and being orthogonal to each other, and, in the C surface of the SiC substrate, measuring the Raman shift value indicating a peak corresponding to a transverse acoustic branch of a Raman spectrum at 1 mm intervals on two straight lines passing through a central point of the C surface and being orthogonal to each other.