Excimer Laser Spot Overlap Machining for Precise Deep Focal Control
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Solution Overview
Problem
In semiconductor exposure apparatuses, the wide spectrum line width of KrF and ArF excimer laser beams leads to chromatic aberration, reducing resolving power due to the use of materials that transmit ultraviolet light, necessitating a method to narrow the spectrum line width of laser beams to minimize aberration.
Innovation Solution
A laser machining method and system that utilize a pulse laser beam from an excimer laser apparatus, guiding the beam through irradiation spots and moving the machining object in the height direction, with an irradiation optical system and fθ lens to condense the beam and ensure overlap of adjacent spots, reducing energy density loss and allowing precise machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a projection lens is made of a material that transmits ultraviolet light (such as KrF and ArF laser beams), then the laser beam can be transmitted through the lens, but chromatic aberration occurs due to the wide spectrum line width, reducing resolving power
Solution Approach 1:
The patent applies parameter changes by narrowing the spectrum line width of the laser beam through a line narrowing module (LNM) with a line narrowing element (etalon or grating). This modifies the spectral parameter of the laser beam to minimize chromatic aberration while maintaining transmission through ultraviolet-transmitting lens materials, thereby resolving the contradiction between lens transmission and chromatic aberration.
2Reliability
If the spectrum line width of the laser beam is narrowed using a line narrowing module, then chromatic aberration is minimized, but the device complexity increases
Solution Approach 1:
The patent integrates the line narrowing module as a standard component within the laser resonator, modifying the spectral parameter of the laser beam. This approach accepts increased device complexity as a necessary trade-off to achieve the critical improvement in resolving power by minimizing chromatic aberration.
3Manufacturing precision
If the pulse laser beam is guided through irradiation spots and the machining object is moved in the height direction, then precise machining is achieved, but the machining process time increases
Solution Approach 1:
The patent employs periodic action by moving the machining object in discrete height steps and performing irradiation at multiple height positions. This stepwise periodic movement allows precise focal point control for accurate machining while managing the overall process time through systematic repetition at different depths.
Solution Approach 2:
The patent segments the machining process into multiple height positions, with the irradiation process performed at discrete vertical levels. This segmentation enables precise control at each height while organizing the overall machining operation into manageable stages, balancing precision requirements with process efficiency.
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 forms machined portions with reduced energy density loss, enabling precise machining even on hard materials by reducing divergence and blurring, and allowing for deeper focal points, thus improving machining efficiency and accuracy.
Implementation Method 1
an fθ lens through which the pulse laser beam from the irradiation optical system is condensed to the machining area
Implementation Method 2
a pulse laser beam output from an excimer laser apparatus
Data Source
AI summary
A laser machining method forms a machined portion in a machining area of a machining object by irradiating the machining area with a pulse laser beam. The laser machining method includes an irradiation process of irradiating the machining area with the pulse laser beam output from an excimer laser apparatus by guiding the pulse laser beam to part of the machining area and moving the guided pulse laser beam through irradiation spots, and a movement process of moving the machining object in a height direction of the machining object. The irradiation process is performed at a plurality of height positions on the machining object moved in the height direction in the movement process. In the irradiation process, at least part of each of the irradiation spots of the pulse laser beam overlaps another irradiation spot adjacent to the irradiation spot.