Laser Interference Lithography Flat-Top Beam Shaping
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Solution Overview
Problem
Conventional laser interference lithography systems fail to produce uniform periodic structures over large sample areas due to non-uniform energy distribution and Gaussian intensity profiles, leading to insufficient uniformity of grating structures.
Innovation Solution
A laser interference lithography system with a flat-top intensity profile is achieved by using a refractive beam shaper and beam expanders to convert Gaussian laser beams into flat-top intensity profiles, ensuring uniform exposure over a larger area through a combination of beam expansion and refraction, with a spatial filter to reduce noise and maintain intensity uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional Lloyd's mirror interferometer with Gaussian laser beam is used, then the system setup is simple and not susceptible to environmental disturbance, but the energy distribution is non-uniform resulting in insufficient uniformity of grating structure over large sample area
Solution Approach 1:
The patent transforms the laser beam intensity profile from Gaussian distribution to flat-top distribution by introducing a beam shaper and spatial filter. This parameter change in the beam intensity distribution enables uniform energy distribution across the sample area, resolving the uniformity issue while preserving the simplicity of the Lloyd's mirror configuration
Solution Approach 2:
The patent introduces a beam shaper and spatial filter as intermediary components between the laser source and the Lloyd's mirror interferometer. These intermediaries modify the beam profile without altering the fundamental interferometer design, achieving uniform grating structures while maintaining system simplicity
2Area of stationary object
If two additional reflecting mirrors are added to create a tunable two-mirror LIL system, then grating structure over 4-inch area can be obtained, but the uniformity of grating structure is still insufficient due to Gaussian intensity profile
Solution Approach 1:
The patent changes the intensity profile parameter from Gaussian to flat-top distribution using a beam shaper. This transformation addresses the uniformity problem that persists even in expanded two-mirror systems, enabling uniform grating structures over large 4-inch sample areas
Solution Approach 2:
The patent applies beam shaping and spatial filtering preliminarily before the beams enter the interferometer. This preliminary action ensures that the beams already have the desired flat-top profile and uniform spatial distribution, which then maintains uniformity throughout the interference process over large areas
3Manufacturing precision
If beam expanders and refractive beam shaper are used to convert Gaussian intensity profile to flat-top intensity profile, then uniform light field distribution and uniform grating structure over large area can be achieved, but the device complexity increases
Solution Approach 1:
The patent introduces beam expanders and a refractive beam shaper as intermediary components that perform the critical function of profile transformation. While these add components, they are strategically placed in the optical path to achieve uniformity without fundamentally redesigning the interferometer, thus managing complexity effectively
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 system achieves uniform light field distribution and reduced grating periodicity variation, enabling the fabrication of uniform periodic structures over a 2-inch area with improved uniformity and consistency, suitable for various nano-patterning applications.
Implementation Method 1
a refractive beam shaper for converting a Gaussian intensity profile inherent to the coherent laser beam into a flat-top intensity profile
Implementation Method 2
at least one reflector for receiving and reflecting the second collimated laser beam to form a third collimated laser beam
Implementation Method 3
a laser source for emitting a coherent laser beam
Implementation Method 4
the second and third collimated laser beams are transmitted to the substrate at a predetermined angle to produce an interference pattern on the substrate
Data Source
AI summary
A laser interference lithography system with flat-top intensity profile comprises a laser source for emitting a coherent laser beam, a first beam expander for adjusting the coherent laser beam size, a refractive beam shaper for converting a Gaussian intensity profile inherent to the coherent laser beam into a flat-top one and outputting a first collimated laser beam, a second beam expander for receiving the first collimated laser beam and outputting a second collimated laser beam, a sample holder for holding a substrate, and at least one reflector for reflecting the second collimated laser beam to generate a third collimated laser beam. The second and third collimated laser beams are transmitted to the substrate at a predetermined angle to create an interference pattern exposed onto the substrate.