Abstract
The application of laser light sources for illumination tasks like in mask aligner lithography relies on non-imaging optical systems with multi-aperture elements for beam shaping. When simulating such systems, the traditional approach is to separate the beam-shaping part (incoherent simulation) from dealing with coherence properties of the illuminating laser light source (diffraction theory with statistical treatment). We present an approach using Gaussian beam decomposition to include coherence simulation into ray tracing, combining these two parts, to get a complete picture in one simulation. We discuss source definition for such simulations, and verify our assumptions on a well-known system. We then apply our approach to an imaging beam shaping setup with microoptical multi-aperture elements. We compare the simulation to measurements of a similar beam-shaping setup with a 193 nm continuous-wave laser in a mask-aligner configuration.
Highlights
To improve the resolution in proximity mask aligner lithography, decreasing the exposure wavelength λ is the only way if a certain exposure gap g is to be maintained as resolution is given by [1]:
Mask aligner lithography relies on uniform illumination of the photomask, containing the structural information which is to be transmitted to a photoresistcoated substrate
For σsim the autocorrelation peak is measured at full width half maximum (FWHM), containing approximately 68% of the total energy, compared to the expected diffraction limited spot size, containing roughly 84% of the energy
Summary
To improve the resolution in proximity mask aligner lithography, decreasing the exposure wavelength λ is the only way if a certain exposure gap g is to be maintained as resolution is given by [1]:. While illumination systems relying on rotating diffusers can be modelled by incoherent ray tracing with good results, the investigation of coherence effects in the illumination path requires coherent simulation of the system [5]. Coherent simulation of such systems is demanding: one has to deal with some thousands of microoptical channels in combination with macroscopic length-scales for the overall illumination system and a diffuse yet coherent source. We present an approach using Gaussian beam decomposition (GBD) for modelling coherence in ray tracing simulation as an approach to combine these opposing requirements
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
