Laser-Altered Holding Jig for Uniform Wafer Grinding
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Solution Overview
Problem
Existing holding jigs for grinding circular plate-shaped wafers often result in minute protruding parts on the supported surface of the workpiece due to the design of grooves, which can affect the uniformity of the ground surface and the transmission of suction force.
Innovation Solution
A holding jig with a plate shape and an altered layer that reaches the central region of the second surface from the central region of the first surface, formed using laser processing, which functions as a suction path with a slight gap to minimize the generation of minute protruding parts during grinding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grooves are formed in the holding jig to transmit suction force, then the suction force transmission is improved, but minute protruding parts are generated on the workpiece surface
Solution Approach 1:
The invention changes the physical state of the groove from a macroscopic open structure to a microscopic altered layer with different material properties. The laser processing creates an altered layer with changed density, hardness, and surface energy, which prevents workpiece material from adhering and forming protrusions while still allowing suction force transmission through the groove structure.
Solution Approach 2:
The altered layer formed by laser processing creates a micro-porous or micro-structured surface layer that allows fluid (suction force) to pass through while preventing solid material (workpiece) from adhering and forming protrusions. The porous structure enables selective permeability to different phases of matter.
2Force
If the holding jig is made with grooves, then the suction force is transmitted to the workpiece, but the workpiece becomes pushed into the grooves during grinding
Solution Approach 1:
The laser processing fundamentally changes the physical parameters of the groove material, creating an altered layer with different mechanical properties including increased hardness, changed thermal conductivity, and modified surface energy. These parameter changes prevent the workpiece material from being pushed into and adhering to the groove structures during grinding.
3Ease of manufacture
If linear grooves are formed by making sum of depths equal to or larger than substrate thickness, then through-holes are created simply, but the grooves remain exposed in the upper surface causing protruding parts
Solution Approach 1:
The invention applies laser processing to change the physical state and properties of the groove material, transforming it from a simple geometric feature that causes protrusions into an altered layer with modified material properties. This parameter change maintains the ease of through-hole formation while eliminating the surface quality issues.
Solution Approach 2:
The invention replaces the traditional mechanical groove formation method with laser processing, which uses optical energy to create the altered layer. This substitution eliminates the mechanical exposure of groove edges that cause protrusions while maintaining the suction force transmission function.
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 holding jig effectively prevents the formation of minute protruding parts on the workpiece surface while maintaining the suction force, ensuring a uniform thickness and surface quality during grinding.
Implementation Method 1
a laser processing step of manufacturing the holding jig by focusing a laser beam having a wavelength component transmitted through the substrate on the substrate and forming the altered layer in the substrate
Data Source
AI summary
A holding jig has a plate shape and is interposed between a workpiece with a circular plate shape and a chuck table when the workpiece is held by the chuck table in a grinding apparatus including the chuck table and a grinding unit including a grinding wheel. The holding jig has a first surface, a second surface on the opposite side of the first surface, and an outer circumferential surface that connects the first surface and the second surface. An altered layer that reaches a central region of the second surface from a central region of the first surface is formed. The material of the main component of the holding jig is the same as the material of the main component of the workpiece.