Wide-Gap Semiconductor Substrate Thinning Without Edge Warpage
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Solution Overview
Problem
Existing methods for thinning wide-gap semiconductor substrates, such as silicon carbide, face challenges including cracking, warping, high abrasive wear, and impractical polishing rates, which hinder the production of devices with low power loss and high mechanical strength.
Innovation Solution
A semiconductor substrate design with a thin-plate part and a thick-plate part, combined with a manufacturing apparatus that uses a cover member to protect the peripheral edge during etching, allowing precise thinning of the inner region without warping or cracking, and a depth monitor for real-time etching control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the silicon carbide substrate is thinned by grinding the back surface to reduce thickness, then the substrate thickness is reduced enabling lower power loss, but the substrate becomes cracked or chipped due to warpage
Solution Approach 1:
The substrate thinning process is segmented into two distinct regions: an inner area that is thinned to a first thickness and an outer peripheral area that is thinned to a second thickness greater than the first. This segmentation allows the device formation area to be sufficiently thin for low power loss while the peripheral area maintains greater thickness to prevent warpage and cracking during processing and conveyance.
Solution Approach 2:
Different thickness qualities are applied to different locations on the substrate back surface. The inner area receives aggressive thinning to achieve the target thickness for device formation, while the outer peripheral area receives less thinning to maintain structural integrity. This local quality differentiation resolves the contradiction between needing thin areas for performance and thick areas for reliability.
2Length of stationary object
If the silicon carbide substrate is thinned by CMP polishing to reduce thickness, then the substrate thickness is reduced, but the polishing rate is too low making the process impractical
Solution Approach 1:
The invention replaces the mechanical CMP polishing system with a chemical etching system. Instead of using mechanical abrasion to remove material, the process uses chemical etching to selectively remove material from the substrate back surface. This substitution dramatically increases the material removal rate while maintaining the ability to achieve uniform thinning across the inner area of the substrate.
3Length of stationary object
If the silicon carbide substrate is ground with a grinding device to thin the back surface, then the substrate thickness is reduced, but high abrasive wear occurs reducing manufacturing efficiency
Solution Approach 1:
The invention replaces the mechanical grinding system with a chemical etching system. Instead of using abrasive grains to mechanically remove material from the silicon carbide substrate, the process uses chemical reactions to dissolve and remove material. This eliminates the high abrasive wear associated with mechanical grinding of hard materials like silicon carbide, significantly reducing consumable wear and improving manufacturing efficiency.
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 method enables the production of devices with low on-state resistance and power loss while maintaining high mechanical strength, reducing manufacturing costs and time by avoiding grinding and improving surface accuracy.
Implementation Method 1
an outer-periphery covering mechanism (40) covering a peripheral edge portion of a wide-gap semiconductor substrate (70) placed on a platen (15) with a cover member (41) during etching of the wide-gap semiconductor substrate (70)
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3(a)~3(c)
AI summary
Provided is a method for manufacturing a wide-gap semiconductor substrate enabling formation of a device having low power loss while maintaining high mechanical strength. This method is an etching method for etching a wide-gap semiconductor substrate (W) placed on a platen (15) disposed in a processing chamber (11) by means of plasma generated from an etching gas so that only a device formation region of the wide-gap semiconductor substrate (W) is thinned, the method including a step of supplying the etching gas into the processing chamber (11) and generating the plasma from the etching gas, and a step of applying a bias potential to the platen (15) to etch only the device formation region of the wide-gap semiconductor substrate (W) so as to thin only the device formation region.