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Thermal evaporation is commonly used for the production of optical coatings. The well-known thermal evaporation is the most frequently used process for the production of optical coatings. The low packing density of thermally evaporated films implies optical constants and mechanical properties which are inferior to those of the bulk materials. In this paper a range of ion based coating technologies, such as ion-assisted deposition (IAD), ion plating (IP), arc discharge evaporation, and plasma IAD are described. For the investigations of the plasma-IAD process, we used a newly developed advanced plasma source (APS) with special features. The properties of dielectric layers deposited with plasma IAD will be presented in comparison to conventional thermally evaporated films. In particular, the results of scratch resistant layers in combination with antireflection coatings on organic substrates will be shown.

This paper presents a detailed study on computer simulations of resist profiles obtained in x-ray lithography for exposures made either with synchrotron radiation or with an Al–Kα source. It is assumed, for purposes of the calculations, that the vacuum windows consist of kapton and that silicon is used as the mask material. The influence of edge shape and mask absorber thickness upon the resist structure is of special interest. The other parameters affecting resist profiles, such as Fresnel diffraction (especially in the case of semitransparent absorbers) and photoelectron range, are taken into consideration. In the case of the x-ray tube, the penumbral blur caused by the finite dimensions of the source spot leads to an additional deterioration of the edge sharpness. For the calculations, the intensity distribution over the spot area was assumed to be uniform (with Gaussian-shaped edges). The influence of the photoelectron range upon the resist profiles is calculated, using the simple depth-dose relationship of Gruen. The calculated resist profiles are compared with typical experimental results.

Very intense technological efforts for increasing the density of integration ofsemiconductor devices have been made in the development of new and economical lithography methods for structures below2/am. The lithography methods used up to now in production are working with UV radiation in the region near 400 rim.The resolution limit due to Fresh'el diffraction allows the replication of structure dimensions down to 3--4 urn. A further improvement of the optical lithography (introduction ofdemagnifying projection printing instead of 1: 1 proximity exposure) probably will lead to powerful production machines enabling the reproduction of structures with dimensions down to 1 ,am.On the other hand, the expenditure increases rapidly when decreasing the resolution limits. For dropping the structure size below 1 tzm, the alternative lithography methods are electron-beam writing and X-ray lithography. Additionally, an application of these methods for larger structures could be furthered by an improvement ofthe yield. X-ray lithography is a direct further development of 1: 1 proximity printing, with the help of a mask, by drastically lowering the wavelen~h. This means the maintenance of a relatively simple process, also in the case ofvery small structures. But an important condition, if X-ray lithography is to be a practical method, is the availability ofan economical X-ray source in the wavelength region of1 nm with nearly parallel radiation. Because at this wavelength there are no problems with Fresn'el diffraction, and the distortions caused by the secondary electrons generated in the resist are much lower compared with electron-beam writing, structures down to 0.1/am are achievable with high aspect ratios. Although the very good replication features have been conf'gmed in many experiments, there are many problems to be solved, especially concerning the radition source, the resist-and the masktechnology.The application of X-ray lithography could mainly provide advantages in the mass production of VLSI devices with constant design.The domain of e-beam writing, besides mask production, could be the production of circuits with frequent changes in design (e.g., in the phase of circuit development).

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