Rapid SiC Wafering by Controlled Vickers Cleavage
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Solution Overview
Problem
The current semiconductor wafer manufacturing process is inefficient and costly due to high material waste (up to 50% loss during slicing), time-consuming (taking weeks to produce wafers), and expensive equipment and consumables, particularly for hard-to-machine wide bandgap materials like SiC, GaN, and diamond.
Innovation Solution
A non-abrasive technique for rapid wafering using a table-top hardness tester with Vickers diamond tips to initiate and propagate cracks in crystalline materials, reducing material loss and time by cleaving wafers without sawing, and employing a wedge to control crack propagation for precise cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If wire sawing is used to slice semiconductor ingots, then wafers can be produced, but up to 50% of the usable ingot material is lost as kerf
Solution Approach 1:
The patent replaces the mechanical wire sawing system with a fracture-based separation system. Instead of using diamond-coated wires to abrasively cut through the ingot, the invention uses pre-formed fractures or cleavage planes within the crystal structure to naturally separate wafers. This substitution eliminates the need for abrasive removal, reducing kerf loss from 50% to minimal amounts while maintaining wafer integrity and quality.
Solution Approach 2:
The invention changes the fundamental parameter of material separation from abrasive removal (wire sawing) to fracture-based separation. By controlling the fracture propagation through precise positioning and force application, the system achieves clean separations with minimal material loss. The parameter change involves transitioning from a removal-based process to a separation-based process that exploits the material's inherent fracture properties.
2Productivity
If wire sawing is used to cut wafers from ingots, then wafers can be produced, but the process takes up to a week due to material hardness
Solution Approach 1:
The patent replaces the slow abrasive wire sawing mechanism with a rapid fracture propagation system. Instead of gradually removing material through abrasion over several days, the invention initiates controlled fractures that propagate quickly through the ingot along predetermined paths. This substitution leverages the material's fracture mechanics rather than fighting against its hardness, reducing processing time from weeks to minutes or hours while maintaining separation quality.
Solution Approach 2:
The invention implements preliminary action by pre-forming fracture initiation points or guiding structures within the ingot before the actual separation process. These pre-prepared features guide the fracture propagation path, ensuring that when the fracture is initiated, it follows the desired trajectory cleanly and rapidly. This preliminary preparation eliminates the need for slow, controlled abrasive cutting through the entire ingot thickness.
3Ease of manufacture
If diamond wire and slurry are used for wire sawing, then cutting can be performed, but expensive consumables must be replaced often
Solution Approach 1:
The patent replaces the consumable-intensive wire sawing system (requiring diamond wires and slurry) with a fracture-based system that uses minimal to no consumables. The separation is achieved through controlled fracture propagation along crystallographic planes or pre-formed interfaces, eliminating the need for abrasive materials. This substitution dramatically reduces consumable costs while maintaining effective separation capability.
Solution Approach 2:
The invention extracts and eliminates the consumable components (diamond wire, slurry) from the cutting process. By relying on the inherent fracture properties of the semiconductor material and controlled force application, the system achieves separation without requiring external abrasive materials. This extraction of consumables simplifies the manufacturing process and eliminates ongoing material costs.
4Manufacturing precision
If wire sawing equipment is used, then wafers can be sliced, but heavy and bulky machines weighing over a ton are required
Solution Approach 1:
The patent replaces the heavy wire sawing machinery with a lightweight fracture propagation system. Instead of requiring tons of equipment to drive abrasive wires through hard materials, the invention uses controlled force application to initiate and guide fractures. This substitution dramatically reduces equipment weight while maintaining precise separation capability, enabling the use of smaller, more flexible manufacturing equipment.
Solution Approach 2:
The invention introduces an intermediary mechanism (such as positioned frustoconical indenters or controlled force application points) that mediates between the applied force and the material separation. These intermediaries concentrate and direct the force to initiate fractures at precise locations, enabling accurate wafer separation without requiring the heavy machinery needed for conventional wire sawing.
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
Dramatically reduces material waste and production time, achieving smooth, defect-free wafers with minimal post-cleavage polishing, and significantly lowers costs by using a compact, cost-effective setup.
Implementation Method 1
A crack is driven parallel to the surface at a depth, typically 500 μm, to separate a wafer from a boule
Implementation Method 2
A non-abrasive technique for rapid wafering using a table-top hardness tester with Vickers diamond tips to initiate and propagate cracks
Data Source
AI summary
This invention concerns cleaving of silicon carbide (SiC) wafers from boule to reduce the cost of manufacturing SiC substrates. We use Vickers diamond tips to initiate a crack, similar to a hardness tester, and a chisel type wedge to drive the crack at a depth of 500 micron. We use the same machine to initiate and propagate the crack. We do not use either a wire saw or a laser or ion implantation to transfer a layer. We prevent the crack from deviating from its plane and we reduce the consumption of diamond and extend the lifetime of Vickers indenters while machining SiC under high load. The rate of diamond consumption is on par or even less than the multi-wire saw. We use parallel indentation in conjunction with fast motors and actuators to speed up the cleavage process and increase the throughput which makes it competitive with the multi-wire saw.