| The linear systems limit of optics is given by a maximal spatial frequency of 2/γ. Conventional imaging schemes are limited by ∼NA/γ. In optical lithography, resolution enhancement techniques (RET's) extend this limit. Imaging interferometric lithography (IIL) is a new RET with the potential to extend the resolution to the linear systems limit of 2/γ.; This potential is explored in two experimental setups for lithography. The first uses a lens of 0.358 NA at a wavelength of 364nm. It has a demagnification of 1/10. Arbitrary structures are printed with smallest feature sizes of 250nm using the scheme of IIL. This corresponds to a γ/CD of 1.49. The value for the conventional scheme is −0.72. The theoretical maximal value for the linear systems limit is 4. The second system was designed to achieve values of 2.7. It utilizes a lens of 0.9 NA, at a wavelength of 244nm. The demagnification is 1/20. It is expected to print CD's of 90nm. Preliminary experiments have produced Manhattan structures with a CD of 200nm.; The principle of IIL was transferred for the first time to optical microscopy and implemented experimentally. A He-Ne laser served as a light source at 633nm. A 0.4 NA, 20x microscope objective at the front end of the experiment limited the spatial frequency transfer. The system's magnification was 200x. Using the new imaging interferometric microscopy (IIM) principle, Manhattan structures with CD's of 500nm on chrome on glass masks could be resolved. Theses results were compared to a conventional microscope image using a 0.9 NA objective and standard illumination and to numerical Fourier optics simulations. IIM achieves the same resolution with three exposures as the standard microscopy image with a better contrast in the high spatial frequencies. It retains the larger field-of view, depth-of-field, and working distance of the low NA objective.; Two-photon lithography was explored as a RET by writing two parallel lines as close as possible to each other with a fs laser system. A linear resolution enhancement of √2 could be realized as predicted. Changes in the photoresist response were observed for different excitation schemes and the two photon absorption coefficient of the Shipley 510 photoresist was measured to be β ∼ 6 × 10−9cm/W. |
