Laser Ablation Power Compensation for Off-Axis Distortion
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Solution Overview
Problem
Existing laser ablation systems for fine line structures on substrates suffer from off-axis focal spot distortion due to lens aberrations, leading to variations in line width and energy density, which can result in incomplete ablation or inaccurate patterning, especially at the extremes of the scan field.
Innovation Solution
A method and apparatus that dynamically adjust the laser output power or pulse energy based on the position of the focal spot relative to the on-axis position, using a controller unit and power changing means to maintain consistent line width across the scan field by compensating for off-axis focal spot distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a scanner and lens are used to form fine line structures by laser ablation, then high resolution patterning is achieved, but off-axis focal spot distortion occurs leading to variations in line width and energy density
Solution Approach 1:
The patent dynamically changes the laser beam power or pulse energy as a function of the focal spot position across the scan field. By adjusting this parameter in real-time, the system compensates for off-axis focal spot distortion and maintains consistent line width and energy density throughout the scanning area, preventing incomplete ablation at field edges
Solution Approach 2:
The system uses a pre-determined compensation profile that maps focal spot position to required power adjustment. This feedback mechanism ensures that as the beam moves to off-axis positions where distortion occurs, the power is automatically adjusted to maintain optimal ablation conditions, thereby ensuring reliable and complete ablation across the entire scan field
2Device complexity
If lens aberrations are present in the scanning optical system, then the system structure is simple, but focal spot shape distortion increases at field extremes reducing peak energy density
Solution Approach 1:
Rather than modifying the optical system structure to eliminate aberrations, the patent changes the laser beam power parameter dynamically based on focal spot position. This approach maintains the simple optical structure while compensating for aberration-induced focal spot distortion through real-time power adjustment, preserving both simplicity and precision
Solution Approach 2:
The patent accepts the presence of lens aberrations as an inherent characteristic of simple optical systems and converts this 'harmful' effect into a manageable parameter. By pre-characterizing the distortion pattern and using it to drive dynamic power compensation, the system transforms the aberration from a defect into a known variable that can be compensated for, maintaining manufacturing precision without increasing device complexity
3Manufacturing precision
If laser power is increased to compensate for energy spreading at off-axis points, then peak energy density is restored, but overall energy consumption increases
Solution Approach 1:
The patent applies local quality by adjusting laser power only at specific off-axis positions where focal spot distortion occurs, rather than uniformly increasing power across the entire scan field. The dynamic power adjustment is localized to regions needing compensation, maintaining peak energy density consistency where required while minimizing unnecessary energy consumption in areas where distortion is negligible
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 ensures consistent peak power or energy density and line width across the scan field, preventing incomplete ablation and maintaining the accuracy of fine line structures, even at the edges of the scan field, thereby enhancing the reliability of high-resolution patterning in thin films and micro-electronic devices.
Implementation Method 1
Laser beam scanner units are commonly based on dual axis oscillating mirrors driven by galvanometer or other motors where the requirement is to mark or pattern over a two dimensional area. For the case where scanning in one axis only is required rotating polygonal mirrors are often used.
Implementation Method 2
A variety of different lenses are used to focus the beam onto the substrate surface. These can range from simple singlet lenses to complex multi-element lenses.
Implementation Method 3
The techniques for marking or patterning flat substrates by laser ablation using beam scanners and focussing lenses is extremely well known
Data Source
AI summary
A method and apparatus is described that allows accurate control of the width of fine line structures ablated by lasers in thin films on substrates when using scanner and focussing lens systems. The method provides dynamic compensation for optical distortions introduced by the scan lens at off axis points by increasing the laser power or energy in the beam in order to overcome the reduction in power or energy density.