Silicon Carbide Cavity Formation by Laser Ablation and Backside Thinning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional machining processes for silicon carbide (SiC) substrates often result in cracking due to their brittleness, and existing etching methods are impractical and expensive for creating cavities in thicker substrates.
Innovation Solution
A method using a laser to partially ablate the substrate from the top side, creating a trench that covers most of the thickness without penetrating fully, followed by mechanical grinding or polishing on the backside to form cavities without cracking, employing maskless technology and avoiding chemical or dry etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional machining processes (slicing, lapping, polishing) are used on SiC substrates, then cavities can be created, but surface and subsurface cracking occurs due to the brittleness of SiC
Solution Approach 1:
The patent replaces conventional mechanical machining processes (slicing, lapping, polishing) with laser-based processing. The laser selectively removes material to create cavities without the mechanical contact and stress that cause cracking in brittle SiC substrates. This substitution of mechanical systems with optical/thermal systems resolves the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The patent changes the processing parameters from mechanical force-based to laser energy-based. By controlling laser power, pulse duration, and scanning speed, the process achieves clean cavity formation without the subsurface damage and cracking inherent in mechanical machining. This parameter change enables both ease of manufacture and crack-free substrates.
2Manufacturing precision
If chemical or dry etching techniques are used to remove SiC, then selective removal can be achieved, but the process becomes prohibitively expensive and impractical for thick substrates due to long etch times
Solution Approach 1:
The patent replaces chemical and dry etching processes with laser-based material removal. The laser directly ablates SiC material at controlled rates (e.g., 1500-10000 angstroms/minute) without requiring chemical etchants or complex masking, achieving both selective removal and high productivity for thick substrates.
Solution Approach 2:
The patent extracts the material removal function from chemical etching processes and implements it through direct laser ablation. This eliminates the need for slow chemical reactions and masking steps, enabling rapid and selective cavity formation in thick SiC substrates while maintaining manufacturing precision.
3Productivity
If direct milling methods are used to create cavities, then material can be removed efficiently, but cracking propagates on the machined surface due to SiC brittleness
Solution Approach 1:
The patent replaces direct mechanical milling with laser ablation for cavity creation. The laser removes material through controlled heating and vaporization rather than mechanical cutting, achieving high material removal rates without inducing the subsurface cracking and surface damage that propagate from mechanical milling in brittle SiC.
Solution Approach 2:
The patent changes from mechanical removal parameters (cutting speed, feed rate, tool geometry) to laser processing parameters (power, pulse duration, scan speed). This parameter transformation enables efficient material removal while maintaining surface integrity by avoiding the mechanical stresses that cause crack propagation in SiC.
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
Enables reliable creation of cavities through full thickness semiconductor wafers without cracking, maintaining the crystal structure and reducing stress concentrations, thus overcoming the limitations of conventional methods.
Implementation Method 1
The method uses a laser to target the bulk of the substrate thickness without penetrating the entire substrate
Data Source
AI summary
A method for creating at least one cavity in a semiconductor substrate including the steps of:(a) partially ablating the semiconductor substrate from the top side with a laser to form a trench in the semiconductor substrate surrounding a cross section of the semiconductor material having the desired shape,(b) machining the backside of the semiconductor substrate partially ablated in step (a) to reduce the semiconductor substrate to a final thickness that is equal to or less than the laser ablation depth to form a plug of semiconductor material unattached to a remainder of the semiconductor substrate; and(c) removing the plug of semiconductor material from the semiconductor substrate to form the at least one cavity with cross section of desired shape extending through the semiconductor substrate.