Wafer Surface Laser Fluence Mapping for Faster SiC Lapping
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Solution Overview
Problem
Conventional laser processing methods for SiC wafers result in inefficient lapping processes due to uniform laser modification across uneven surfaces, leading to increased time consumption and abrasive usage, and higher overall loss rates of wafers.
Innovation Solution
A method involving a laser processing system that scans the wafer surface to determine profile distribution, allowing for a fluence integration distribution that varies based on the surface profile, enhancing modification in high-profile areas and reducing it in low-profile areas, thereby optimizing the lapping process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If uniform laser modification is applied across the entire wafer surface, then the modified layer thickness is consistent, but the lapping process becomes time-consuming and consumes high amounts of abrasives
Solution Approach 1:
The patent applies local quality by varying the laser fluence distribution across different regions of the wafer surface based on the measured profile distribution. Regions with higher profile distribution receive higher fluence to create thicker modified layers, while regions with lower profile distribution receive lower fluence. This localized adjustment optimizes the modified layer thickness distribution to match the surface topology, thereby reducing lapping time and abrasive consumption while maintaining adequate modification uniformity where needed.
Solution Approach 2:
The patent implements preliminary action by performing profile scanning of the wafer surface before laser modification to obtain the profile distribution information. This preliminary measurement enables the laser processing system to pre-calculate and apply the appropriate fluence integration distribution, ensuring that the subsequent laser modification is optimized for each specific region before the lapping process begins, thus avoiding unnecessary removal of material during lapping.
2Reliability
If comprehensive laser modification is performed before lapping, then the modified layer covers the entire surface, but excessive material is removed during lapping increasing wafer loss
Solution Approach 1:
The patent applies local quality by varying the laser fluence distribution across different regions of the wafer surface based on the measured profile distribution. Regions with higher profile distribution receive higher fluence to create thicker modified layers, while regions with lower profile distribution receive lower fluence. This localized adjustment optimizes the modified layer thickness distribution to match the surface topology, thereby reducing lapping time and abrasive consumption while maintaining adequate modification uniformity where needed.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the laser fluence parameter across different spatial regions of the wafer surface. Instead of using a uniform fluence value, the system varies the fluence integration distribution according to the profile distribution data, thereby optimizing the modified layer thickness in each region to minimize excessive material removal during lapping while ensuring adequate coverage.
3Shape
If conventional lapping process is used on hard SiC wafer surface, then the surface is planarized, but the process is very time-consuming and consumes high amounts of abrasives
Solution Approach 1:
The patent implements preliminary action by performing profile scanning of the wafer surface before laser modification to obtain the profile distribution information. This preliminary measurement enables the laser processing system to pre-calculate and apply the appropriate fluence integration distribution, ensuring that the subsequent laser modification is optimized for each specific region before the lapping process begins, thus avoiding unnecessary removal of material during lapping.
Solution Approach 2:
The patent applies mechanics substitution by replacing part of the mechanical lapping process with laser-induced modification. The laser modifies the physical and chemical properties of the SiC surface layer, making it softer and more susceptible to subsequent lapping or polishing. This substitution of mechanical action with thermal/chemical modification reduces the time and abrasive consumption required for achieving the desired surface flatness.
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 reduces the time and abrasive consumption in the lapping process while minimizing wafer loss by tailoring laser modification to the surface profile, potentially eliminating the need for initial lapping and directly proceeding to polishing.
Implementation Method 1
performing laser processing on the wafer from the top surface of the wafer by a laser apparatus with a fluence integration distribution
Implementation Method 2
performing laser processing on the wafer from the top surface of the wafer by a laser apparatus with a fluence integration distribution to form a laser-processed wafer
Data Source
AI summary
A method for laser processing wafer surface comprises following steps of: providing a wafer; performing profile scanning a top surface of the wafer by a scanning device to obtain a profile distribution of the top surface of the wafer; and performing laser processing on the wafer from the top surface of the wafer by a laser apparatus with a fluence integration distribution to form a laser-processed wafer, wherein the fluence integration distribution is related to the profile distribution of the top surface of the wafer.