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Investigation of the process latitude for sub-half-micron pattern replication in x-ray lithography

: Oertel, H.K.; Huber, H.-L.; Weiß, M.


Microelectronic engineering 13 (1991), No.1-4, pp.339-342
ISSN: 0167-9317
International Conference on Microlithography: Microcircuit Engineering (ME) <16, 1990, Leuven>
Conference Paper
Fraunhofer ISIT ()

It has been shown, that using soft x-ray radiation and the proximity printing scheme, mask features down to 150 nm in size can be printed in single layer resists of 1 micron thickness and above. A figure of merrit for the application of x-ray lithography (XRL) in volume production has to consider parameters as wavelength range, proximity gap, mask contrast, different types of features (lines, spaces, lines and spaces, contact holes, and islands), linewidth control, and regarding the development process resist sensitivity, resist contrast and development behaviour. B.J.Lin proposed to analyse the aerial image profile and to relate the results to resist profiles by assuming a resist of infinite contrast. He extended the description of optical printing schemes by means of curves of constant linewidth in the exposure-defocus-space (E-D-trees) to soft x-ray proximity printing by similar curves in the exposure-proximity gap-space (E-G-trees). His study for three different long features with quarter micron pattern size, 10 per cent linewidth control, a rectangular type of spectral wavelength distribution, and constant mask contrast of 10 showed that the process window opens below a proximity gap value of about 25 micron. Including as two-dimensional features contact holes and islands he concluded that with quarter micron design rules there is no process window at all for any gap larger than 20 micron. In this contribution the influence of spectral distribution and source point spot-size as well as the influence of the mask contrast on the process window will be studied. Furthermore the influence of the resist development on process window will be investigated. The consideration of resist contrast and dark erosion rate effects tends to increase the process window considerably.