Laser-Induced Substrate Structuring for Nano-Rod Formation
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Solution Overview
Problem
Current methods for generating small-sized features on substrate surfaces, such as semiconductor surfaces, are complex and costly, and existing techniques like pulsed laser-assisted etching produce structures larger than the laser wavelength.
Innovation Solution
A method involving irradiation of a substrate surface with a first set of polarized short laser pulses while in contact with a fluid, followed by a second set of pulses with different polarization, to break up initial surface features into smaller-sized nanostructures, such as nano-sized rods, achieving surface densities of 1×10^8 to 1×10^11 cm^-2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pulsed laser-assisted etching is used to fabricate small structures, then structures can be formed directly onto the substrate, but the structure sizes are larger than the laser wavelength
Solution Approach 1:
The patent applies segmentation by using a two-step laser irradiation process: first forming larger micrometer-sized structures, then breaking them up into smaller nanometer-sized features through a second irradiation step with different polarization. This divides the structure formation process into sequential stages to achieve final dimensions smaller than the laser wavelength.
Solution Approach 2:
The patent uses preliminary action by first creating micrometer-sized structures as intermediate features before breaking them down into nanometer-sized final structures. The fluid is also applied in advance to the substrate surface before laser irradiation to facilitate the structure formation and breakdown process.
2Manufacturing precision
If conventional lithography and chemical etching are used, then control over shape and size is achieved, but the processes are complex and costly
Solution Approach 1:
The patent replaces complex mechanical and chemical systems (lithography masks, chemical etchants, multiple processing steps) with a simplified optical system using polarized laser pulses. The control over shape and size is achieved through optical parameters (polarization direction, pulse energy, wavelength) rather than mechanical or chemical processes.
Solution Approach 2:
The patent uses parameter changes by varying laser pulse parameters (polarization direction, energy density, wavelength) to control the formation and breakdown of surface structures. By changing the polarization direction between two irradiation steps, the process achieves precise control over final structure dimensions without complex equipment.
3Manufacturing precision
If a single set of polarized laser pulses is used, then initial surface structures are formed, but they are not broken up into smaller nanosized features
Solution Approach 1:
The patent applies periodic action by using repeated laser irradiation cycles with different polarization directions. The first irradiation creates initial structures, and subsequent irradiations with perpendicular polarization break them down into smaller features. This periodic application of laser energy with varying parameters enables progressive refinement of structure size.
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 effectively generates micron-sized and submicron-sized features, specifically nano-sized rods with diameters of 50 nm to 200 nm and heights of 50 nm to 500 nm, overcoming the limitations of existing techniques by producing finer features with controlled surface density and size.
Implementation Method 1
a plurality of micron-sized and/or submicron-sized features are formed in a top surface layer of the substrate by irradiating a substrate surface with a plurality of polarized short radiation pulses
Implementation Method 2
the structured surface can be irradiated with a second set of linearly polarized short laser pulses with a different polarization axis so as to break up the surface features formed by the first set into smaller-sized features
Data Source
AI summary
In one aspect, the present invention provides a method of processing a substrate, e.g., a semiconductor substrate, by irradiating a surface of the substrate (or at least a portion of the surface) with a first set of polarized short laser pulses while exposing the surface to a fluid to generate a plurality of structures on the surface, e.g., within a top layer of the surface. Subsequently, the structured surface can be irradiated with another set of polarized short laser pulses having a different polarization than that of the initial set while exposing the structured surface to a fluid, e.g., the same fluid initially utilized to form the structured surface or a different fluid. In many embodiments, the second set of polarized laser pulses cause the surface structures formed by the first set to break up into smaller-sized structures, e.g., nano-sized features such as nano-sized rods.