SiC Wafer Grind Disc for Uniform Thickness Removal
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Solution Overview
Problem
Grinding silicon carbide semiconductor wafers poses challenges due to its hardness and brittleness, leading to excessive tool wear, heat generation, cracks, and non-uniform material removal, including center dimples and edge rolls, which affect the quality and precision of the finished product.
Innovation Solution
A polishing system with a grind disc having an abrasive surface that contacts the entire surface of the silicon carbide wafer, utilizing additives to enhance grinding operations, reducing non-uniformities such as center dimple and edge roll, and enabling both grinding and polishing operations in a single system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional grinding methods are used on silicon carbide wafers, then material removal is achieved, but non-uniform material removal occurs including center dimples and edge rolls
Solution Approach 1:
The grinding process is divided into multiple sequential steps: coarse grinding to remove bulk material, followed by fine grinding to achieve uniform surface. This segmentation allows each step to be optimized independently, with coarse grinding handling high material removal and fine grinding focusing on uniformity, thereby eliminating center dimples and edge rolls while maintaining process simplicity
Solution Approach 2:
The invention changes key grinding parameters including using different abrasive grit sizes for coarse and fine grinding, adjusting wheel speed and feed rate, and modifying wheel composition (resin-bonded vs. metal-bonded). These parameter changes enable uniform material removal across the wafer surface by optimizing the interaction between abrasive and workpiece for each grinding stage
2Productivity
If grinding operations are performed on silicon carbide, then thickness reduction is achieved, but excessive tool wear occurs due to hardness and brittleness
Solution Approach 1:
The invention uses different wheel compositions for different grinding stages: resin-bonded wheels for coarse grinding that remove material quickly but wear faster, and metal-bonded wheels for fine grinding that provide slower but more consistent material removal with extended wheel life. This parameter change in wheel composition balances productivity and tool durability
Solution Approach 2:
The process discards the worn coarse grinding wheel and recovers by using a fresh fine grinding wheel for the next stage. This allows optimal performance at each stage without compromising overall tool life, as each wheel is used only for its intended purpose until wear necessitates replacement
3Manufacturing precision
If grinding is performed on silicon carbide wafers, then thickness is reduced, but heat generation and cracks occur due to material brittleness
Solution Approach 1:
The grinding process is segmented into coarse and fine stages with intermediate steps for stress relief and surface inspection. This segmentation allows heat and stress to be managed in controlled increments rather than accumulated continuously, preventing thermal damage and cracking while achieving the required dimensional accuracy
Solution Approach 2:
The grinding process uses periodic action with intermittent cooling periods and alternating between coarse and fine grinding passes. This periodic action allows heat dissipation between passes and prevents thermal buildup that would cause cracking, while maintaining continuous progress toward the target thickness
4Manufacturing precision
If the grind disc contacts only partial surface of the wafer, then grinding operation is simpler, but non-uniformities such as center dimple and edge roll are produced
Solution Approach 1:
The invention transitions from partial surface contact (2D area contact) to complete surface contact by using a wafer-sized grind disc that matches the wafer diameter. This dimensional change ensures every point on the wafer surface receives uniform grinding action, eliminating center dimples and edge rolls while the disc can be replaced or reconfigured as needed, managing the complexity
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 system achieves uniform material removal, reduces tool wear, and maintains precision dimensions and surface finish, addressing the challenges of silicon carbide's hardness and brittleness, while allowing for efficient batch processing.
Implementation Method 1
a grind disc having an abrasive surface configured to grind silicon carbide
Implementation Method 2
imparting relative motion between the grind disc and the silicon carbide semiconductor workpiece
Data Source
AI summary
Grind discs for semiconductor polishing systems are provided. In one example, a semiconductor workpiece polishing system includes a platen configured to rotate about an axis. The semiconductor workpiece polishing system further includes a grind disc on the platen, the grind disc has an abrasive surface configured to grind silicon carbide. The semiconductor workpiece polishing system includes a workpiece carrier operable to bring a silicon carbide semiconductor workpiece into contact with the grind disc to implement a grinding operation on the silicon carbide semiconductor workpiece. The grinding operation reduces a thickness of the silicon carbide semiconductor workpiece by at least about 0.5 microns.