Ultrafast Laser Scribing and Chemical Etching for Transparent Materials
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Solution Overview
Problem
Current methods for singulating and cleaving wafers and glass panels, such as diamond cutting and laser ablation, face issues like poor edge quality, microcracks, contamination, and low processing speed, especially in transparent materials, which limit the precision and efficiency of the manufacturing process.
Innovation Solution
The formation of continuous laser filaments in transparent materials using ultrafast laser pulses focused externally to create a beam waist outside the material, avoiding optical breakdown and enabling precise cutting with minimal collateral damage, allowing for the creation of long, taper-free filaments that can be used for singulation and marking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If diamond cutting is used for scribing, then cutting speed can be maintained, but edge quality deteriorates with microcracks and wide kerf width
Solution Approach 1:
The patent replaces the mechanical diamond cutting system with a laser-based system. Specifically, it uses a combination of ultrashort pulse laser ablation to create precise modification lines followed by chemical etching to achieve clean separation. This substitution eliminates mechanical contact, preventing the generation of microcracks and wide kerf widths associated with diamond cutting, while maintaining high processing speeds through the rapid ablation and etching process.
Solution Approach 2:
The patent changes the physical parameters of the cutting process by using ultrashort pulse durations (femtosecond to picosecond range) and specific wavelength selection to achieve nonlinear absorption in transparent materials. This parameter change enables precise energy deposition with minimal thermal diffusion, creating narrow modification zones that result in high-quality edges with minimal microcracking, while the rapid pulse delivery maintains high productivity.
2Manufacturing precision
If laser ablation is used for scribing transparent materials, then mechanical contact is eliminated, but processing speed deteriorates
Solution Approach 1:
The patent merges two processes into a coordinated sequence: ultrashort pulse laser ablation creates precise modification lines, and chemical etching immediately follows to complete the separation. This combination leverages the precision of laser ablation while the chemical etching process rapidly removes material to achieve high processing speeds. The synergistic effect of combining these two methods resolves the speed limitation of pure laser ablation.
Solution Approach 2:
The patent implements continuous processing by maintaining a high repetition rate of ultrashort laser pulses to continuously create modification lines across the material, followed by continuous chemical etching. This continuous action eliminates idle time between steps and maintains high productivity throughout the process, addressing the speed limitation while preserving the precision benefits of laser ablation.
3Device complexity
If conventional laser pulses are used, then processing is simpler, but collateral thermal damage increases
Solution Approach 1:
The patent uses periodic ultrashort laser pulses with carefully controlled duration (femtosecond to picosecond range) and repetition rates. This periodic action allows each pulse to deposit energy before significant thermal diffusion can occur, minimizing the heat affected zone. The pulsed nature maintains relative system simplicity while dramatically reducing collateral thermal damage compared to continuous wave lasers.
Solution Approach 2:
The patent changes the temporal parameter of laser pulses to ultrashort durations and selects specific wavelengths that match the absorption characteristics of the target material. This parameter change enables nonlinear absorption processes that confine energy deposition to the focal volume, preventing thermal diffusion to surrounding areas. The result is minimal heat affected zone while maintaining practical laser system operation.
4Manufacturing precision
If multiple passes are used for femtosecond cutting, then precision is improved, but throughput deteriorates
Solution Approach 1:
The patent performs preliminary laser ablation to create modification lines that precisely define the cut path and depth. This preliminary action prepares the material so that subsequent chemical etching can rapidly complete the separation in a single pass. The preliminary structuring by laser enables high precision while the single-pass chemical etching restores high throughput, eliminating the need for multiple precision passes.
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 method achieves high precision and efficiency in cutting transparent materials with reduced microcracks and debris, enabling the production of fine structures and maintaining the integrity of the material, with post-cleave break strength exceeding 50 MPa, and allows for the processing of smaller device sizes and complex material stacks.
Implementation Method 1
the high laser intensity induces nonlinear absorption effects to provide a dynamic opacity that can be controlled to accurately deposit appropriate laser energy into a small volume of the material as defined by the focal volume
Implementation Method 2
Femtosecond and picosecond laser ablation, therefore, offer significant benefits in machining of both opaque and transparent materials
Implementation Method 3
eliminating plasma creation and therefor plasma reflections thereby reducing collateral damage through the small component of thermal diffusion and other heat transport effects during the much shorter time scale of such laser pulses
Implementation Method 4
The formation of continuous laser filaments in transparent materials using ultrafast laser pulses focused externally to create a beam waist outside the material
Data Source
AI summary
Very fine closed form structures can be scribed via filamentation in the transparent substrate very quickly, the modified zone can be etched via dry or wet chemical etching to release the closed form. A metal layer engages the transparent substrate and is covered with photoresist. A portion of the photoresist and a portion of the metal are removed simultaneously with the creation of a filament through the transparent substrate. The photoresist protects the portion of the metal layer that is not removed. The desired closed form can be released by weakening the cut region using dry or wet chemical etching to remove the desired part.