Laser Focus Position Correction for Thermal Drift in Wafer Processing
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Solution Overview
Problem
High-speed processing of semiconductor wafers using laser processing apparatuses leads to thermal expansion of components, causing shifts in the position of the laser beam's converged spot, resulting in reduced processing quality due to the need for time-consuming detection and correction methods that may not effectively address significant thermal expansions.
Innovation Solution
A laser processing apparatus equipped with a temperature detector and a controller that uses a correlation map to adjust the position of the converged laser beam based on temperature changes, ensuring accurate positional correction of the laser beam in both the thicknesswise and indexing feed directions, utilizing a linear motor with electromagnetic coils as the moving mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the holding table is processing-fed at high speed (600-1000 mm/s or higher), then productivity is improved, but thermal expansion of components causes shift in converged spot position, worsening manufacturing precision
Solution Approach 1:
The system performs preliminary temperature detection and positional correction before the thermal expansion significantly affects the converged spot position. By detecting temperature changes early and calculating correction values in advance, the system prevents position deviations rather than correcting them after they occur, maintaining precision at high feed speeds
Solution Approach 2:
The system implements a feedback mechanism where temperature detectors continuously monitor the holding table and actuators, and the controller uses this temperature information to calculate and apply real-time correction values to the converged spot position, compensating for thermal expansion effects during high-speed processing
2Manufacturing precision
If conventional correction methods using laser-processed marks are used, then converged spot position can be corrected, but the time-consuming detection process increases processing time
Solution Approach 1:
The system replaces the mechanical/optical detection method (using laser-processed marks and optical detectors) with a temperature-based detection and calculation method. By detecting temperature changes and calculating position corrections through computational logic rather than physical mark detection, the system achieves faster correction without sacrificing precision
Solution Approach 2:
The system performs temperature-based position correction in advance and during processing, rather than waiting to detect marks after processing. This preliminary correction approach eliminates the time-consuming mark detection step while maintaining accuracy
3Productivity
If components are thermally expanded too much by high-speed processing, then productivity is maintained, but conventional correcting procedures become ineffective, worsening manufacturing precision
Solution Approach 1:
The system continuously monitors temperature changes in the holding table and actuators during high-speed processing and dynamically adjusts the converged spot position based on real-time temperature data. This feedback mechanism enables effective correction even under significant thermal expansion conditions that would render conventional methods ineffective
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 solution allows for precise correction of the laser beam's position, preventing shifts caused by thermal expansion, thereby enhancing processing quality and reducing processing time by enabling early and accurate detection of temperature changes.
Implementation Method 1
an electric motor included as an actuator in the moving mechanism generates heat
Implementation Method 2
an electric motor included as an actuator in the moving mechanism generates heat, thermally expanding components that are affected by the heat
Implementation Method 3
a laser beam emitted from a laser oscillator is applied to a semiconductor wafer
Data Source
AI summary
A laser processing apparatus includes a laser beam applying mechanism for applying a laser beam to a workpiece held by a holding mechanism while keeping a converged spot of the laser beam in the workpiece, and a temperature detector for detecting a temperature of the holding mechanism or a temperature of an actuator of a moving mechanism that moves the holding mechanism in a processing feed direction. The laser beam applying mechanism has a converged spot position adjusting unit. The controller, depending on a temperature change detected by the temperature detector, controls the converged spot position adjusting unit to establish a position of the converged spot of the laser beam in a thicknesswise direction of the workpiece.