Semiconductor Wafer Dicing with Modified Layer Removal
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Solution Overview
Problem
The stealth dicing method for semiconductor wafers results in reduced flexural strength of device chips due to the presence of modified layers, making it difficult to divide the workpiece into individual chips without compromising the process.
Innovation Solution
A method involving a laser beam application to create cracks in the workpiece, followed by a cutting step using a cutting blade with a specifically designed cross-sectional shape to remove the modified layers, ensuring the cutting fluid does not enter the cracks, thereby increasing the flexural strength and ease of division into device chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If modified layers are left in device chips to facilitate division, then it is easier to divide the workpiece into device chips, but the flexural strength of the device chips is lowered
Solution Approach 1:
The cutting step extracts and removes the modified layers from the device chips after laser processing has created the necessary cracks for division. This extraction resolves the contradiction by eliminating the harmful modified layers that would otherwise remain in the chips, thereby restoring flexural strength while preserving the crack-induced ease of division.
2Strength
If cutting is performed to remove modified layers, then flexural strength of device chips is increased, but it may cause contamination of cracks with cutting fluid and cut chips
Solution Approach 1:
The cutting blade is designed with non-uniform thickness, creating a localized quality difference where the thinner portion preferentially cuts along the crack interfaces. This local geometric feature guides the cutting action to occur primarily at the crack locations, minimizing the intrusion of cutting fluid and chips into the cracks while still effectively removing modified layers.
Solution Approach 2:
The cracks created by laser processing, which could potentially trap cutting fluid and cause contamination, are instead utilized as preferred cutting paths. The cutting blade follows these pre-formed cracks, converting what could be a source of contamination into a beneficial guide for clean, precise removal of modified layers with minimal fluid intrusion.
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 increases the flexural strength of device chips by removing modified layers, preventing contamination and ensuring clean separation, which enhances the reliability of subsequent processing steps.
Implementation Method 1
applying a laser beam having a wavelength that is transmittable through the workpiece to a reverse side of the workpiece along the streets while focusing the laser beam at a point within the workpiece, thereby forming modified layers in the workpiece along the streets and cracks extending from the modified layers to the face side
Data Source
AI summary
Disclosed herein is a method of processing a workpiece having a plurality of streets provided on a face side thereof, the method including: a laser beam applying step of applying a laser beam having a wavelength that is transmittable through the workpiece along the streets while focusing the laser beam at a point within the workpiece, thereby forming modified layers in the workpiece along the streets and cracks extending from the modified layers to the face side; and a cutting step of, thereafter, cutting the workpiece from a reverse side thereof along the streets while supplying the workpiece with a cutting fluid, thereby removing the modified layers from the workpiece.