Wafer Division Using Laser Modified Layers and Plasma Etching
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Solution Overview
Problem
During the division of wafers into individual device chips, dust from modified layers contaminates the front surface of devices and the atmosphere, and the remaining modified layers at the sidewalls reduce the flexural strength of the chips.
Innovation Solution
A processing method that includes forming modified layers inside planned dividing lines using a laser beam, coating the wafer's front surface with a water-soluble resin, supporting the wafer with a dicing tape and ring frame, expanding the tape to divide the wafer, and using plasma etching to remove the modified layers while protecting the chip surfaces with the resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If modified layers are formed inside planned dividing lines by laser irradiation to enable wafer division, then the wafer can be divided into individual device chips, but dust is scattered from the modified layers and adheres to the front surface of devices, contaminating the devices
Solution Approach 1:
A protective film is applied to the front surface of the wafer before laser irradiation. This protective film acts as an intermediary barrier that prevents dust generated from the modified layers during division from adhering to the device front surfaces, while allowing the laser beam to pass through and form the modified layers effectively.
Solution Approach 2:
The protective film is applied in advance before the laser irradiation and division process. This preliminary action ensures that the front surface is protected before dust generation occurs during the modified layer formation and subsequent division, preventing contamination from the outset.
2Ease of manufacture
If modified layers are formed inside planned dividing lines by laser irradiation, then the wafer can be divided into individual device chips, but part of the modified layers remains at the outer circumferences (sidewalls) of the device chips, causing dust to scatter and contaminate subsequent steps
Solution Approach 1:
The patent replaces mechanical removal methods with plasma processing to remove modified layers from the sidewalls. Plasma processing provides more precise and complete removal of the modified layers at the outer circumferences, preventing dust generation that would contaminate the atmosphere in subsequent steps.
Solution Approach 2:
The modified layers that remain at the sidewalls after division, which initially cause contamination problems, are selectively removed using plasma processing. This converts the harmful residual modified layers into a controlled removal process that eliminates dust generation while preserving the integrity of the device chips.
3Ease of manufacture
If modified layers remain at the sidewalls of device chips after division, then the division process is simplified, but the flexural strength of the device chips is lowered
Solution Approach 1:
Plasma processing is used to selectively remove the modified layers from the sidewalls of the device chips after division. This non-mechanical process precisely removes the problematic modified layers without damaging the chip structure, thereby restoring the flexural strength while maintaining the simplicity of the division process.
Solution Approach 2:
The patent changes the physical and chemical state of the modified layers through plasma processing, transforming them from a state that compromises structural integrity to a state where they are completely removed. This parameter change restores the mechanical properties of the device chips, specifically the flexural strength.
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
Prevents contamination of device chips and the atmosphere by shielding dust with the water-soluble resin and removes modified layers without damaging the chips, thereby maintaining the flexural strength of the device chips.
Implementation Method 1
a laser beam irradiation unit that irradiates the workpiece held by the chuck table with a laser beam
Implementation Method 2
positions the focal point of the laser beam to the inside of a planned dividing line of the wafer and executes irradiation to form modified layers that serve as the points of origin of dividing inside the planned dividing lines
Implementation Method 3
executing plasma etching and removing the modified layers that remain at side surfaces of the device chips
Data Source
AI summary
A processing method of a wafer includes a modified layer forming step of positioning the focal point of a laser beam with a wavelength having transmissibility with respect to the wafer to the inside of a planned dividing line and executing irradiation along the planned dividing line to form modified layers inside and a water-soluble resin coating step of coating the front surface of the wafer with a water-soluble resin before or after the modified layer forming step. The processing method also includes a dividing step of expanding a dicing tape to divide the wafer into individual device chips together with the water-soluble resin with which the front surface of the wafer is coated and a modified layer removal step of executing plasma etching and removing the modified layers that remain at the side surfaces of the device chips in a state in which the dicing tape is expanded and the front surfaces of the individual device chips are coated with the water-soluble resin.