Off-Axis Laser Wafer Smoothing for Low-Loss SiC Surface Processing
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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 at perpendicular angles, which fail to effectively reduce surface roughness.
Innovation Solution
Employing a laser-based surface processing method with lasers incident at non-perpendicular angles to impart relative motion, reducing surface roughness and thickness of semiconductor wafers by selectively ablating higher surface features, utilizing non-consumable tools to minimize material loss and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If perpendicular laser ablation is used for surface processing, then material removal is achieved, but surface roughness is not effectively reduced and significant material loss occurs
Solution Approach 1:
The patent changes the laser incidence angle parameter from perpendicular (0 degrees) to non-perpendicular angles (specifically 45-75 degrees from the surface normal). This parameter change transforms the ablation mechanism to preferentially remove protruding surface features while preserving valleys, thereby reducing surface roughness and minimizing overall material loss through selective ablation of only the highest surface points
Solution Approach 2:
The patent applies local quality by making the ablation effect location-dependent on surface topography. The non-perpendicular laser angle creates localized preferential removal at protruding regions while leaving recessed areas intact. This selective local removal continues iteratively to progressively smooth the entire surface, achieving uniform roughness reduction without uniform material loss across the substrate
2Productivity
If consumable tools are used for surface processing, then material removal is achieved, but manufacturing costs increase due to tool consumption and replacement
Solution Approach 1:
The patent replaces mechanical consumable tools (such as abrasive papers, polishing pads, or grinding wheels that wear down and require replacement) with a non-mechanical laser-based ablation system. The laser beam is a non-consumable energy source that can process surfaces continuously without degradation, eliminating tool replacement costs while maintaining high processing productivity through direct energy-to-material conversion
Solution Approach 2:
The patent changes the processing mechanism from mechanical contact (with consumable tool wear) to optical energy interaction (with non-consumable laser). By adjusting laser parameters such as pulse duration, energy density, and incidence angle, the system achieves efficient material removal without the diminishing returns and replacement costs associated with mechanical tool wear
3Manufacturing precision
If non-uniform surface processing is used, then material removal varies across the surface, but surface smoothness and structural integrity are compromised
Solution Approach 1:
The patent changes the laser incidence angle parameter to create controlled non-uniform ablation that preferentially targets protruding surface features. This selective parameter application removes material from high points while preserving low points, progressively converging toward a uniform surface topology. The process maintains structural integrity by avoiding aggressive uniform removal that would compromise underlying material strength
Solution Approach 2:
The patent employs periodic action through iterative multiple-pass laser processing. Each pass selectively removes protruding features, and subsequent passes continue the smoothing process on the newly formed surface. This periodic application of the same non-perpendicular ablation principle progressively achieves uniform surface smoothness while preserving the underlying structural integrity through gradual, controlled material removal
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 surface smoothness, increases fracture strength, and reduces manufacturing costs by minimizing tool consumption and material waste, achieving a smoother surface with reduced roughness and improved structural integrity.
Implementation Method 1
providing emission of one or more lasers to the surface of a semiconductor workpiece... selectively ablating higher surface features
Implementation Method 2
ablating higher surface features, utilizing non-consumable tools to minimize material loss
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.