Pulsed Laser Direct Writing for Repeatable Sub-100 nm Nanolithography
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Solution Overview
Problem
Existing nano-scale patterning methods using ultrashort laser pulses suffer from stochastic effects and poor repeatability due to reliance on near-threshold processes, limiting the fabrication of sub-100 nm structures.
Innovation Solution
A laser patterning method involving the use of tailored pulse bursts to selectively excite precursor sites on a sample, with controlled intensities, temporal inter-pulse spacings, and spatial overlap, allowing for the formation of patterned features smaller than the illumination beam size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tightly-focused laser beams with adjusted energy near the damage threshold are used to achieve small feature sizes, then feature size is reduced, but repeatability deteriorates due to stochastic near-threshold processes
Solution Approach 1:
The patent applies preliminary action by pre-forming precursor sites (such as color centers or defect sites) in the material before the final patterning step. These precursor sites serve as predetermined locations that will deterministically respond to subsequent laser irradiation, eliminating the stochastic nature of direct threshold-based patterning. The precursor sites are created in advance and then selectively activated by the laser to form the final patterned features with high repeatability.
Solution Approach 2:
The patent introduces an intermediary mechanism by using precursor sites as intermediate structures between the laser beam and the final patterned features. These precursor sites act as mediators that convert the laser energy into deterministic material modifications. The precursor sites have specific optical properties that allow them to absorb laser energy and trigger localized material changes only at their precise locations, providing a deterministic pathway from laser irradiation to feature formation.
2Manufacturing precision
If multi-photon absorption in large-bandgap materials is used to fabricate nano-scale features, then sub-100 nm structures can be formed, but repeatability deteriorates due to laser energy fluctuations
Solution Approach 1:
The patent applies preliminary action by pre-forming precursor sites (such as color centers or defect sites) in the material before the final patterning step. These precursor sites serve as predetermined locations that will deterministically respond to subsequent laser irradiation, eliminating the stochastic nature of direct threshold-based patterning. The precursor sites are created in advance and then selectively activated by the laser to form the final patterned features with high repeatability.
Solution Approach 2:
The patent applies parameter changes by modifying the optical properties of the material through precursor site formation. The precursor sites have different absorption characteristics compared to the bulk material, creating localized regions with altered parameters. This allows the material to respond differently at precursor site locations versus surrounding areas, enabling deterministic patterning that is insensitive to overall laser energy fluctuations.
3Manufacturing precision
If conventional laser patterning is used to achieve nanometer-scale structures, then high resolution is obtained through cold ablation, but feature repeatability deteriorates due to stochastic effects
Solution Approach 1:
The patent applies preliminary action by pre-forming precursor sites (such as color centers or defect sites) in the material before the final patterning step. These precursor sites serve as predetermined locations that will deterministically respond to subsequent laser irradiation, eliminating the stochastic nature of direct threshold-based patterning. The precursor sites are created in advance and then selectively activated by the laser to form the final patterned features with high repeatability.
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
Enables repeatable and reliable fabrication of nanoscale features with precise dimensions, overcoming the limitations of stochastic processes and achieving feature sizes down to 50 nm or less.
Implementation Method 1
nano-scale features may be fabricated in some applications through multi-photon absorption in large-bandgap materials
Implementation Method 2
Ultrashort laser pulses (e.g., laser pulses with durations on the order of picoseconds, femtoseconds, or lower) can produce nanometer-scale structures with high resolution due to so-called 'cold ablation' that reduces or completely avoids detrimental thermal effects
Data Source
AI summary
A laser patterning method may include fabricating one or more precursor sites on a sample, generating an illumination beam including one or more pulse bursts, each pulse burst including two or more laser pulses, and scanning the illumination beam across the sample along a scan pattern including locations of the one or more precursor sites. At least one of intensities, temporal inter-pulse spacings, or spatial overlap between the two or more laser pulses in the illumination beam may be selected to selectively excite the one or more precursor sites to selectively modify the sample at the one or more precursor sites to form one or more patterned features, where a dimension of at least one feature in the one or more patterned features along at least one dimension is smaller than a size of the illumination beam on the sample.