Off-Axis Laser Wafer Processing for Surface Roughness Control
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Solution Overview
Problem
Existing methods for fabricating semiconductor wafers from crystalline boules, such as silicon carbide, result in significant material loss and high costs due to the use of consumable tools and non-uniform surface processing, particularly with non-planar laser ablation methods that do not effectively reduce surface roughness.
Innovation Solution
Employing a laser-based system with lasers at a non-perpendicular incidence angle for surface processing of semiconductor wafers, utilizing relative motion to smooth the surface and reduce roughness, thereby minimizing material loss and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional consumable tools are used for surface processing, then material removal is achieved, but material loss increases and costs rise
Solution Approach 1:
The patent replaces conventional mechanical consumable tools (grinding wheels, lapping plates) with a laser-based system that uses optical energy for material removal. The laser beam interacts with the semiconductor wafer surface through ablation, eliminating the need for physical contact and consumable mechanical tools, thereby reducing material loss and operational costs.
Solution Approach 2:
The patent employs controlled laser parameters (wavelength, pulse duration, power, scanning speed) to optimize material removal efficiency while minimizing damage to the workpiece. By adjusting these parameters, the system achieves precise surface processing with reduced material loss compared to conventional mechanical methods.
2Manufacturing precision
If non-planar laser ablation is used, then material removal is achieved, but surface roughness is not effectively reduced
Solution Approach 1:
The patent implements a multi-pass laser processing strategy where different regions of the surface receive tailored laser treatment. The first pass removes gross irregularities, while subsequent passes with adjusted parameters refine the surface quality. This localized, staged approach ensures both material removal and effective surface smoothing.
Solution Approach 2:
The patent uses periodic pulsed laser operation with controlled duty cycles and repetition rates. The pulsed nature allows thermal diffusion between pulses, preventing excessive heat accumulation that would cause surface damage. This periodic action enables progressive surface smoothing while maintaining material integrity.
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 achieves reduced surface roughness and increased fracture strength of semiconductor wafers by selectively removing higher surface features, reducing material loss and operational costs through non-consumable tool usage.
Implementation Method 1
providing emission of one or more lasers to the surface of a semiconductor workpiece... a laser-based system with lasers at a non-perpendicular incidence angle for surface processing of semiconductor wafers, utilizing relative motion to smooth the surface and reduce roughness
Data Source
AI summary
Systems and methods for laser-based surface processing operations on a semiconductor wafer, such as a silicon carbide semiconductor wafer, are provided. In one example, a method includes providing a semiconductor workpiece having a surface. The method includes providing emission of one or more lasers to the surface of a semiconductor workpiece at a non-perpendicular incidence angle relative to the surface. The method includes imparting relative motion between the one or more lasers and the semiconductor workpiece while providing emission of the one or more lasers to the surface of the semiconductor workpiece at the non-perpendicular incidence angle.