Transmissive Sheet Laser Wafer Processing to Prevent Bending
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Solution Overview
Problem
Existing laser processing methods face issues with wafer bending due to volume expansion during modified layer formation, leading to unstable chuck table holding and improper division into device chips.
Innovation Solution
A method involving a chuck table with a holding surface and a transmissible sheet to stabilize the workpiece, using atmospheric pressure to maintain close contact and form a modified layer inside the workpiece without bending, followed by dividing the workpiece into individual device chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the focal point of a laser beam is positioned inside the workpiece to form a modified layer, then internal processing can be executed to enable wafer division, but volume expansion occurs causing the wafer to bend and the holding force becomes unstable
Solution Approach 1:
A transparent sheet is introduced as an intermediary between the chuck table and the workpiece. This sheet transmits the laser beam while allowing atmospheric pressure to act uniformly on the workpiece surface, preventing bending caused by volume expansion during modified layer formation.
Solution Approach 2:
Atmospheric pressure is utilized to press the transparent sheet against the workpiece surface, maintaining stable contact and preventing wafer bending. The suction force generated by the chuck table creates a vacuum that holds the sheet in place, ensuring the workpiece remains flat during laser processing.
2Ease of manufacture
If the focal point of a laser beam is positioned inside the workpiece to form a modified layer, then division into device chips can be enabled, but the wafer bends making it impossible to properly form the modified layer
Solution Approach 1:
The transparent sheet serves as a mediator that transmits laser energy while maintaining atmospheric pressure contact with the workpiece. This prevents wafer bending and ensures the focal point remains accurately positioned inside the workpiece for proper modified layer formation.
Solution Approach 2:
The introduction of the transparent sheet changes the pressure distribution parameters on the workpiece surface, maintaining uniform atmospheric pressure that prevents bending while allowing laser beam transmission for precise modified layer formation.
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 suppresses workpiece bending and ensures stable formation of modified layers, enabling proper division into device chips.
Implementation Method 1
laser beam with such a wavelength as to be transmitted through a workpiece
Implementation Method 2
the focal point of a laser beam is positioned inside the workpiece
Implementation Method 3
the workpiece is irradiated with the laser beam to form a modified layer inside the workpiece
Implementation Method 4
a sheet having transmissibility... positioning the focal point of the laser beam inside the workpiece through the sheet
Implementation Method 5
generating a suction force for the holding surface of the chuck table and reducing the pressure on a region covered by the sheet
Implementation Method 6
to bring the workpiece into close contact with the upper surface of the chuck table by an atmospheric pressure applied to the sheet
Data Source
AI summary
A processing method includes a holding step of holding a workpiece by a chuck table including a holding surface that holds the workpiece in an upper surface and a sheet covering step of covering the upper surface of the chuck table in addition to the workpiece by a sheet having transmissibility. The processing method also includes a close contact step of generating a suction force for the holding surface of the chuck table and reducing the pressure on a region covered by the sheet to bring the workpiece into close contact with the upper surface of the chuck table by an atmospheric pressure applied to the sheet and a modified layer forming step of positioning the focal point of a laser beam inside the workpiece through the sheet and irradiating the workpiece with the laser beam to form a modified layer.