Wafer Edge Trimming With Laser-Fractured Off-Cut Segmentation
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Solution Overview
Problem
Existing edge trimming techniques for wafers result in large annular off-cuts during grinding, which require periodic cleaning and are prone to chipping, leading to inefficiencies and maintenance challenges.
Innovation Solution
A processing method involving a trimming step to form an annular stepped portion, followed by laser processing to create concentrically arranged fracture starting points, and subsequent grinding with a protective member to reduce off-cuts by subdividing fragments, thereby minimizing waste and promoting smooth fracture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If edge trimming is performed to prevent chipping during grinding, then chipping is suppressed, but large annular off-cuts are generated that require periodic cleaning
Solution Approach 1:
The patent divides the annular stepped portion into multiple small fragments by forming fracture starting points (modified layers) within it. Instead of removing the entire annular portion as one large off-cut, the modified layers cause the material to break into numerous small pieces during grinding, thereby reducing the size of off-cuts while maintaining the chipping prevention function
Solution Approach 2:
The patent performs laser processing to create modified layers (fracture starting points) within the annular stepped portion before the grinding operation. This preliminary action prepares the material structure in advance so that during subsequent grinding, the material will naturally fracture into small pieces rather than forming large off-cuts
2Length of moving object
If the wafer is ground to extremely small thickness of 50μm or smaller, then thinning is achieved, but the outer peripheral edge becomes a sharp knife edge prone to chipping
Solution Approach 1:
The patent removes the continuous annular stepped portion from the wafer periphery, segmenting it away from the main wafer body. This eliminates the stress concentration point that would otherwise cause chipping in ultra-thin wafers, while the trimming step creates a clean edge that is less prone to damage
Solution Approach 2:
The patent extracts and removes the annular stepped portion from the wafer structure through the combined trimming and grinding process. By taking out this potentially problematic feature that could cause chipping, the wafer edge becomes more stable and reliable for ultra-thin applications
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 method effectively reduces the size of off-cuts during wafer grinding, enhances the separation process, and minimizes wear on grinding stones, improving operational efficiency and reducing maintenance needs.
Implementation Method 1
applying, to the annular stepped portion, a laser beam of a wavelength that has transmissivity for the wafer
Implementation Method 2
fracture starting points from which the wafer is to be fractured under an external force applied by the grinding are formed in the stepped portion
Data Source
AI summary
A processing method of a wafer includes trimming the wafer along its outer peripheral edge while causing a cutting blade to cut from a front surface into a chamfered portion to a depth greater than a finish thickness, so that an annular stepped portion is formed in an outer peripheral surplus region. A protective member is bonded to a side of the front surface of the wafer, and the wafer is ground from its back surface to thin the wafer to a finish thickness. Between trimming and grinding, a laser beam is applied to the stepped portion, so that annular modified layers which are to be fractured under a pressing force to be applied by the grinding are formed in the stepped portion, whereby the fractured fragments of the stepped portion are subdivided.