Wafer Dicing with Laser-Formed Cracks and Side-Face Trimming
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Solution Overview
Problem
The use of laser processing to divide wafers results in modified layers on the side faces of semiconductor device chips, which obstruct light emission and reduce chip strength, while conventional cutting methods with thick blades increase kerf loss.
Innovation Solution
A method involving laser beam application to form modified layers, followed by tape affixing and expansion to create gaps, and subsequent cutting with a cutting blade to remove modified layers, minimizing material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cutting blade with large edge thickness is used to cut the wafer, then the cutting blade can withstand the load and avoid damage, but the kerf width increases and material loss increases
Solution Approach 1:
The method applies preliminary action by first forming modified layers through laser irradiation before the cutting blade contacts the wafer. The modified layers are created by irradiating the wafer with a laser beam having a wavelength transmittable through the wafer while positioning the focused spot within the wafer, which prepares the material structure in advance to facilitate easier cutting with reduced blade thickness.
Solution Approach 2:
The invention replaces part of the mechanical cutting system with a laser processing system. Instead of relying solely on a thick mechanical cutting blade to handle hard materials like sapphire, the method uses laser irradiation to pre-modify the material structure, substituting optical energy for mechanical force and enabling the use of thinner, more precise cutting blades.
2Loss of substance
If a laser beam is used to divide the wafer, then kerf loss is reduced, but modified layers are left on the chip side faces which obstruct light emission and reduce chip strength
Solution Approach 1:
The method extracts the harmful modified layers from the chip side faces by causing the cutting blade to cut into the modified layers formed by laser irradiation. This removes the obstructing modified layers from the LED chip side faces while maintaining the benefits of reduced kerf loss from the laser processing.
3Object-generated harmful factors
If the cutting blade cuts into cracks with extremely small widths, then the modified layers can be removed, but the cutting blade undergoes the same load as cutting the wafer itself and tends to be damaged
Solution Approach 1:
The laser irradiation performs preliminary action by creating modified layers that extend through the wafer thickness, which then serve as pre-formed crack paths. When the cutting blade contacts these pre-formed cracks, it follows the existing paths rather than having to fracture intact material, significantly reducing the mechanical load on the blade.
4Strength
If a thick cutting blade is used to cut highly hard materials like sapphire, then the blade can avoid damage, but the kerf width increases and material volume for device chips is reduced
Solution Approach 1:
The invention replaces the purely mechanical cutting system with a hybrid laser-mechanical system. The laser beam pre-modifies the sapphire wafer structure by creating modified layers, which reduces the mechanical resistance encountered by the cutting blade, enabling the use of thinner blades that produce narrower kerfs and preserve more material for device chips.
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
Reduces kerf loss and removes modified layers from chip side faces, enhancing chip brightness and strength while maintaining material efficiency.
Implementation Method 1
applying a laser beam having a wavelength transmittable through the wafer to the wafer while positioning its focused spot within the wafer, thereby forming modified layers in the wafer along the projected dicing lines
Data Source
AI summary
A wafer processing method including applying a laser beam to the wafer along projected dicing lines of the wafer while focusing the laser beam within the wafer, thereby forming modified layers in the wafer along the projected dicing lines, after the modified layers have been formed in the wafer, affixing a first tape to a reverse side of the wafer, after the first tape has been affixed to the reverse side of the wafer, developing cracks initiated from the modified layers in the wafer to divide the wafer into a plurality of device chips, and expanding the first tape to form gaps between the device chips, and after the gaps have been formed between the device chips, inserting a cutting blade into the gaps and causing the cutting blade to cut into side faces of the device chips, thereby cutting off the side faces of the device chips.