Silicon Carbide Substrate Processing via Laser Pyrolysis
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Solution Overview
Problem
Current silicon carbide (SiC) processing techniques, such as mechanical grinding/dicing and plasma dicing, face challenges due to the high mechanical hardness of SiC, leading to material damage and low throughput, and require expensive thick metal hard masks for etching.
Innovation Solution
A method involving laser-assisted plasma thinning and dicing, where SiC is decomposed into Si and C through pyrolysis, allowing for etching without the need for thick metal masks, using a two-part process of pyrolyzing and removing debris layers with high etch selectivity, repeated as necessary to achieve desired thickness or dicing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mechanical grinding/dicing is used to process SiC, then material removal is achieved, but significant mechanical damage occurs in the SiC material
Solution Approach 1:
The patent replaces mechanical grinding/dicing with a chemical etching process using ClF3 gas. The etching process chemically removes SiC material without mechanical contact, thereby eliminating mechanical damage while maintaining material removal capability. The chemical reaction between ClF3 and SiC enables precise material removal through selective etching.
Solution Approach 2:
The patent changes the processing parameters by using plasma activation to enhance the etching rate of ClF3. By controlling plasma power, gas flow, and temperature, the process achieves high etching rates (greater than 1 μm/min) while maintaining clean cuts without mechanical damage to the SiC material.
2Reliability
If plasma dicing with ClF3 etching gases is used, then etching is achieved, but the etching rate is low (less than 1 μm/min) leading to very long etching times
Solution Approach 1:
The patent employs periodic pulsed plasma etching cycles, alternating between plasma on-time (for etching) and plasma off-time (for debris removal and surface refresh). This periodic action prevents debris accumulation that would otherwise passivate the surface and reduce etching rate, thereby achieving sustained high etching rates greater than 1 μm/min while maintaining etching quality.
Solution Approach 2:
The patent implements continuous plasma flow during the etching process to constantly supply fresh reactive species to the etching surface. This continuous action prevents depletion of reactive chlorine atoms and maintains high etching rates throughout the process, eliminating the need for long etching times while preserving etching quality.
3Reliability
If thick metal hard masks (10 μm to 15 μm) are used for etching, then etching process is enabled, but the process becomes very expensive
Solution Approach 1:
The patent extracts and removes the thick metal hard mask layer from the process by using selective chemical etching with ClF3 gas. The etching process selectively removes the metal mask material through chemical reaction, eliminating the need for thick masks and subsequent mask removal steps, thereby significantly reducing process cost while maintaining etching capability.
Solution Approach 2:
The patent replaces expensive thick metal hard masks with thin sacrificial mask layers (such as photoresist or thin metal layers) that are selectively removed by the ClF3 etching process. These disposable thin masks are much cheaper to apply and remove, and the etching process itself serves to clear them away, reducing overall manufacturing cost while enabling the etching process.
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 reduces mechanical damage, increases etching rate, and eliminates the need for expensive masks, resulting in higher throughput and improved mechanical breaking strength of SiC chips.
Implementation Method 1
pyrolyzing a surface of the substrate to produce a silicon and carbon containing debris layer over the silicon carbide containing crystalline substrate
Implementation Method 2
State-of-the-art plasma dicing of SiC wafers, utilizing e.g. ClF3 etching gases
Data Source
AI summary
A method of processing silicon carbide containing crystalline substrate is provided. The method includes pyrolyzing a surface of the silicon carbide containing crystalline substrate to produce a silicon and carbon containing debris layer over the silicon carbide containing crystalline substrate, and removing the silicon and carbon containing debris layer, wherein the pyrolyzing and the removing is repeated at least once.