Laser Workpiece Division via Refractive Index Matching Coating
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Solution Overview
Problem
The existing laser processing method for dividing semiconductor wafers is hindered by surface unevenness, which causes refraction issues with the pulsed laser beam, leading to reduced processing quality and the need for preliminary grinding, limiting its applicability.
Innovation Solution
Applying a coating member with a refractive index close to that of the workpiece to the incident surface to planarize it, allowing for improved focusing of the pulsed laser beam and forming a modified layer inside the workpiece, followed by external force application for division.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pulsed laser beam is applied to a workpiece with an uneven incident surface, then laser processing can be performed, but the laser beam refracts at the interface causing reduced focusing accuracy and processing quality
Solution Approach 1:
A coating member is applied to the incident surface of the workpiece to serve as an intermediary layer. This coating member has a refractive index that is an intermediate value between air and the workpiece material, reducing the refraction of the pulsed laser beam at the interface. The coating member planarizes the incident surface and improves focusing accuracy without requiring preliminary grinding of the workpiece.
2Manufacturing precision
If the incident surface is planarized by preliminary grinding, then laser processing quality is improved, but the workpiece thickness is reduced and the process becomes more complex
Solution Approach 1:
The coating member acts as a mediator that provides the necessary surface planarity for accurate laser focusing without requiring direct removal of workpiece material through grinding. This eliminates the preliminary grinding step and reduces overall process complexity while maintaining incident surface planarity.
Solution Approach 2:
Instead of changing the physical shape of the workpiece surface through grinding, the invention changes the optical parameters by applying a coating member with specific refractive index properties. This alters the optical interface characteristics without mechanically modifying the workpiece geometry.
3Manufacturing precision
If the incident surface is planarized by grinding, then laser processing quality is improved, but material is removed from the workpiece
Solution Approach 1:
The coating member serves as an intermediary that provides the necessary optical interface quality without requiring removal of workpiece material. The coating is applied to the existing surface, eliminating the need for abrasive grinding that would remove material while still achieving the required surface planarity for high-quality laser processing.
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
Enables precise and effective laser processing for dividing semiconductor wafers with uneven surfaces without the need for grinding, enhancing processing quality and applicability to various workpiece types.
Implementation Method 1
the pulsed laser beam incident on the incident surface of the workpiece refracts at the interface between air and the workpiece
Implementation Method 2
applying a pulsed laser beam to a workpiece to form modified layers inside the workpiece
Data Source
AI summary
A workpiece dividing method for dividing a workpiece having an uneven incident surface upon which a pulsed laser beam falls. The workpiece dividing method includes a coating step of applying a coating member to the incident surface of the workpiece, thereby planarizing the incident surface of the workpiece, the coating member transmitting the pulsed laser beam and having a refractive index close to that of the workpiece for the pulsed laser beam, a modified layer forming step of applying the pulsed laser beam to the workpiece from the side of the incident surface in the condition where a focal point of the pulsed laser beam is set inside the workpiece after performing the coating step, thereby forming a modified layer inside the workpiece, and a dividing step of applying an external force to the workpiece after performing the modified layer forming step, thereby dividing the workpiece as starting from the modified layer formed inside said workpiece as a break start point.