Wafer Laser Division via Reflected Light Feedback
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Solution Overview
Problem
The existing wafer processing methods face challenges in forming a uniform modified layer when the surface irradiated with a laser beam is nonuniform, leading to uneven crack formation and difficulties in wafer division.
Innovation Solution
A method involving a laser processing apparatus that detects the reflected light distribution along the planned dividing lines, sets regions based on this distribution, and applies laser processing under different conditions to ensure a uniform modified layer formation, stabilizing the laser beam and maintaining consistent processing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser beam is applied along planned dividing lines under constant irradiation conditions, then processing efficiency is maintained, but nonuniform modified layer is formed due to surface irregularities
Solution Approach 1:
The patent applies dynamics by making the laser processing conditions variable rather than constant. The control unit dynamically adjusts laser processing parameters (such as irradiation intensity or scanning speed) based on real-time reflected light intensity measurements. This allows the system to adapt to surface irregularities like projections and depressions, ensuring uniform modified layer formation while maintaining processing efficiency.
Solution Approach 2:
The patent implements feedback control by measuring the reflected light intensity from the wafer surface and using this information to adjust laser processing conditions. The control unit receives reflected light intensity signals and modifies laser parameters accordingly, creating a closed-loop system that compensates for surface nonuniformities and ensures consistent modified layer quality throughout the processing area.
2Ease of manufacture
If laser processing is performed on nonuniform surface, then processing can be completed, but cracks are not formed uniformly leading to division problems
Solution Approach 1:
The system uses reflected light intensity measurements as feedback to monitor surface conditions during laser processing. Based on this feedback, the control unit adjusts laser parameters in real-time to compensate for surface irregularities, ensuring that cracks form uniformly throughout the wafer despite variations in surface topology, thereby improving division reliability.
Solution Approach 2:
The patent applies parameter changes by modifying laser processing parameters (such as power, speed, or focal position) in response to detected surface variations. This dynamic parameter adjustment ensures that the laser energy delivery is optimized for each local area, producing uniform crack formation and reliable wafer division even across nonuniform surfaces.
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
This approach enables the formation of a uniform modified layer within the wafer, ensuring consistent and stable crack formation across the wafer, thereby facilitating uniform division even when the irradiated surface is nonuniform.
Implementation Method 1
The modified layer is formed by causing multiphoton absorption by applying a laser beam having a transmission wavelength to the wafer and condensing the laser beam onto the inside of the wafer
Implementation Method 2
irradiating the wafer with light for state detection along the plurality of planned dividing lines, and detecting reflected light of the light from an upper surface of the wafer
Data Source
AI summary
A processing method for performing laser processing on a wafer includes: a reflected light detecting step of irradiating the wafer with light for state detection along a plurality of planned dividing lines, and detecting reflected light of the light from an upper surface of the wafer; a region setting step of setting a first region and a second region to the planned dividing lines based on the reflected light; a first laser processing step of performing laser processing on the first region under a first laser processing condition; and a second laser processing step of performing laser processing on the second region under a second laser processing condition.