Proximity exposure techniques in lithography are getting more and more popular because of the cost of ownership
advantage of mask aligners compared to projection systems. In this paper a gap between simulation and the final result,
the prints will be closed. We compare high resolution measurements of intensity field behind amplitude masks with
proximity correction structures with simulations gain insight in limitation of proximity lithography. The final goal is to
develop techniques that allow enhancing the resolution by using advanced optical correction structures. The correction
structures are designed with Layout Lab (GenISys GmbH), prints are done and characterized and the results are compared
with measured light intensity distributions. The light intensity distributions behind the mask are recorded using a High
Resolution Interference Microscopy (HRIM). We concentrate on an example study of edge slope improvement and we
explore possibilities of improved parameters like edge slope at different proximity distances. Simulations and
measurements are compared and discussed.
We introduce a complete methodology for process window optimization in proximity mask aligner lithography. The
commercially available lithography simulation software LAB from GenISys GmbH was used for simulation of light
propagation and 3D resist development. The methodology was tested for the practical example of lines and spaces, 5 micron
half-pitch, printed in a 1 micron thick layer of AZ® 1512HS1 positive photoresist on a silicon wafer. A SUSS MicroTec
MA8 mask aligner, equipped with MO Exposure Optics® was used in simulation and experiment. MO Exposure Optics®
is the latest generation of illumination systems for mask aligners. MO Exposure Optics® provides telecentric illumination
and excellent light uniformity over the full mask field. MO Exposure Optics® allows the lithography engineer to freely
shape the angular spectrum of the illumination light (customized illumination), which is a mandatory requirement for
process window optimization. Three different illumination settings have been tested for 0 to 100 micron proximity gap.
The results obtained prove, that the introduced process window methodology is a major step forward to obtain more robust
processes in mask aligner lithography. The most remarkable outcome of the presented study is that a smaller exposure gap
does not automatically lead to better print results in proximity lithography - what the “good instinct” of a lithographer
would expect. With more than 5'000 mask aligners installed in research and industry worldwide, the proposed process
window methodology might have significant impact on yield improvement and cost saving in industry.
This paper [J. Micro/Nanolith. MEMS MOEMS. 12, (2 ), 023015 (Apr–Jun 2013)] was mistakenly published as a regularly contributed paper in the April–June 2013 issue of JM3. It was intended to be published with the special section on “Advanced Fabrication of MEMS and Photonic Devices” guest edited by Freymann, Maher, and Suleski in the October-December 2013 issue of JM3. The paper can be found online at CrossRef[[XSLOpenURL/10.1117/1.JMM.12.2.023015]]. It also appears in the October–December 2013 print issue with the special section.
We report on the light confinement effect observed in nonideally shaped (i.e., nonspherical) nanoscale solid immersion lenses (SIL). To investigate this effect, nanostructures of various shapes are fabricated by electron-beam lithography. When completely melted in reflow, these noncircular pillars become spherical, while incomplete melting results in nonspherically shaped SILs. Optical characterization shows that nonideal SILs exhibit a spot size reduction comparable with that of spherical SILs. When the size of the SIL is of wavelength scale or smaller, aberrations are negligible due to the short optical path length. This insensitivity to minor variations in the shape implies a large tolerance in nano-SIL fabrication.
We report on the light confinement effect observed in non-ideally shaped (i.e., non-spherical) nanoscale solid immersion lenses (SILs). To investigate this effect, nanostructures of various shapes are fabricated by electron-beam lithography. When completely melted in reflow, these non-circular pillars become spherical, while incomplete melting results in nonspherically shaped SILs. Optical characterization shows that non-ideal SILs exhibit a spot size reduction comparable to that of spherical SILs. When the SIL size is wavelength scale or smaller, aberrations are negligible due to the short optical path length. This insensitivity to minor variations in shape implies a large tolerance in nano-SIL fabrication.