It is well admitted that NanoImprint is a powerfull next generation lithography. Nevertheless many defects may appear during a NanoImprint process. Some of them are clearly related to the stamp or polymer surface properties, or the stamp pattern symmetry breakdown. This paper will address the defectivity issue in imprint process and specially in non printed areas where resist features may appear. They are related to capillary forces between the stamp surface and the polymer. The understanding of their growth with respect to mold-polymer distance and printing process is presented. A specific stamp, with cavity depths ranging from 12-224 nm, has been designed to control the capillary bridge growth. The resulting capillary bridges were characterized as a function of the cavity depth, printing temperature, resist thickness and printing time. Results show that capillary bridge number is strongly influenced by cavity depth and in a less extent by temperature and printing time.
In-line process control in microelectronics manufacturing requires real-time and non-invasive monitoring techniques.
Among the different metrology techniques, scatterometry, based on the analysis of ellipsometric signatures (i.e stokes coefficients vs. wavelength) of the light scattered by a patterned structures, seems to be well adapted.
Traditionally, the problem of defining the shape and computing the signature is dealt with modal methods and is called direct problem. On the opposite, the inverse problem allows to find the grating shape thanks to an experimental signature acquisition, and can not be solved as easily. Different classes of algorithms have been introduced (evolutionary, simplex, etc.) to address this problem, but the method of library searching seems to be the most attractive technique for industry. This technique has many advantages that will be presented in this article, however the main limitation in real-time context comes from the short data acquisition time for
different wavelengths. Indeed, the lack of data leads to the method failure and several database patterns can match the experimental data. In this article, a technique for real time reconstruction of grating shape variation using dynamic scatterometry is presented. The different tools to realize this reconstruction, such as Modal
Method by Fourier Expansion, regularization technique and specific software and hardware architectures are then introduced. Results issued from dynamic experiments will finally illustrate this paper.
Hot embossing throughput is a key issue, which has been addressed in this paper. We show how it is possible to remove
the mold from the imprinted resist at the imprint temperature. We study reflow behavior of imprinted patterns, and
make a cooling and quenching simulation. This work can lead to design of cooling tools adapted to a given application,
and suits as well for the full wafer imprint, as well for the roll imprint.
Sub 100 nm resolution on 200 mm silicon stamp have been hot embossed into commercial Sumitomo NEB 22 resist. A single dot pattern, exposed with electron beam lithography, has been considered to define the stamp and make thus possible to point out the impact of stamp design onto the printing. Moreover, more complex shapes (triangular, elliptic, random...) with sub 200 nm resolution with and without uniform surrounding frame have been also designed. A large scale of initial resist thickness, from 56 nm to 506 nm, has been printed to assess the effect of polymer flow properties onto the stamp cavities filling and the printed defects. The impact of the pattern symmetry breakdown onto defect generation is clearly shown in this paper in the printed areas as well as in the unprinted areas.