Subsurface Laser Parting of Crystalline Material With Crack Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for removing thin layers of crystalline materials from substrates, such as wire sawing, face challenges including significant material loss, high processing times, stress-induced wafer bow and warp, and high production costs, particularly for silicon carbide which requires extensive time and resources.
Innovation Solution
A method involving imaging and analysis of uncracked regions after subsurface laser damage to determine necessary adjustments in laser damage formation parameters, such as power and depth, to promote crack formation and subsequent fracture, allowing for more efficient and uniform production of thin layers with reduced material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If wire sawing is used to cut thin layers from crystalline substrates, then material can be removed and wafers can be produced, but significant material loss occurs due to kerf width
Solution Approach 1:
The patent replaces the mechanical wire saw cutting system with a laser-based system that uses optical energy to induce subsurface damage and thermal stress for fracture. The laser beam focuses energy at a specific depth below the surface, creating a damage layer that promotes controlled cracking without the need for mechanical contact, thereby eliminating kerf loss associated with wire sawing.
Solution Approach 2:
The patent changes the physical state and parameters of the laser processing by controlling laser power, scanning speed, and focal depth to optimize the subsurface damage formation. By adjusting these parameters, the process achieves minimal material loss while maintaining high productivity through controlled fracture propagation.
2Productivity
If wire sawing is used to cut thin layers, then wafers can be produced, but processing times are very long
Solution Approach 1:
The laser-based system replaces slow mechanical wire sawing with optical processing that induces rapid subsurface damage and fracture. The laser can quickly scan across the substrate surface, creating damage patterns that lead to instantaneous fracture along the desired cutting line, dramatically reducing processing time while increasing productivity.
Solution Approach 2:
The laser processing uses periodic pulsed operation to create subsurface damage at controlled intervals. The laser scans repeatedly over the same path multiple times, with each pass adding to the cumulative damage until fracture occurs. This periodic action allows for precise control of the damage depth and extent, optimizing both speed and quality.
3Ease of manufacture
If wire sawing is used to cut thin layers, then material can be removed, but stress-induced wafer bow and warp occur
Solution Approach 1:
The laser-based system replaces mechanical cutting that applies direct physical stress with optical energy deposition. The laser induces thermal stress and subsurface damage without mechanical contact, allowing the wafer to fracture along the damage line with minimal external force. This reduces stress-induced bow and warp while maintaining ease of manufacture through controlled fracture.
Solution Approach 2:
The subsurface laser damage layer acts as an intermediary that mediates the separation process. Instead of applying direct mechanical stress to cut the wafer, the laser creates a damaged zone that serves as a preferential path for fracture propagation. This intermediary damage layer reduces the stress required for separation and minimizes warping.
4Manufacturing precision
If conventional laser damage formation is used, then subsurface damage can be created, but uncracked regions remain requiring additional processing
Solution Approach 1:
The patent implements feedback control by imaging the substrate surface after laser processing to detect uncracked regions. The imaging system provides real-time information about the effectiveness of the laser damage formation, allowing the system to adjust processing parameters or re-scan specific areas to ensure complete crack propagation. This feedback loop improves manufacturing precision while managing device complexity through automated detection and adjustment.
Solution Approach 2:
The imaging and analysis of uncracked regions is performed as a preliminary step before final fracture. By identifying areas that require additional laser damage formation, the system can apply preliminary corrective action to ensure uniform crack propagation across the entire substrate, improving manufacturing precision without requiring complex post-processing.
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 enhances the efficiency of laser-assisted processing by optimizing laser damage formation, reducing material loss, and improving the uniformity and quality of the produced wafers, thereby addressing the limitations of traditional methods.
Implementation Method 1
supplying emissions of a laser focused along a first average depth position within an interior of a crystalline material
Implementation Method 2
supplying emissions of a laser focused along a first average depth position within an interior of a crystalline material of a substrate
Data Source
AI summary
A crystalline material processing method includes forming subsurface laser damage at a first average depth position to form cracks in the substrate interior propagating outward from at least one subsurface laser damage pattern, followed by imaging the substrate top surface, analyzing the image to identify a condition indicative of presence of uncracked regions within the substrate, and taking one or more actions responsive to the analyzing. One potential action includes changing an instruction set for producing subsequent laser damage formation (at second or subsequent average depth positions), without necessarily forming additional damage at the first depth position. Another potential action includes forming additional subsurface laser damage at the first depth position. The substrate surface is illuminated with a diffuse light source arranged perpendicular to a primary substrate flat and positioned to a first side of the substrate, and imaged with an imaging device positioned to an opposing second side of the substrate.