Application of synchrotron radiation to x-ray lithography

Abstract

Synchrotron radiation from the German electron synchrotron DESY in Hamburg has been used for x-ray lithography. Replications of different master patterns (for magnetic bubble devices, Fresnel zone plates, etc.) were made using various wavelengths and exposures. High-quality lines down to 500 Å wide have been reproduced using very soft x rays. The sensitivities of x-ray resists have been evaluated over a wide range of exposures. Various critical factors (heating, radiation damage, etc.) involved with x-ray lithography using synchrotron radiation have been studied. General considerations of storage ring sources designed as radiation sources for x-ray lithography are discussed, together with a comparison with x-ray tube sources. The general conclusion is that x-ray lithography using synchrotron radiation offers considerable promise as a process for forming high-quality-submicron images with exposure times as short as a few seconds.

Composition and Resistivity of Sputtered Tungsten Silicides

“…Chemical vapor deposition (CVD) has been used for deposition of pure WSix (1,2). High purity silicide layers with low sheet resistance, low particles, and excellent step covverage can be obtained by this method.…”

Fabrication of 0.2 μm large scale integrated circuits using synchrotron radiation x-ray lithography

“…[1][2][3][4][5][6][7][8][9][10] The 512 kilobit static random access memory ͑SRAM͒ fabrication with 100% bit yield by IBM's group in 1993, for example, demonstrated that SR lithography was a viable candidate for sub-0.25 m device fabrication. 9 As the result of the development of SR rings, [11][12][13] x-ray steppers, 14 -18 high-quality x-ray masks, 19,20 and mask inspection 21 and repair 22 systems over the last decade, an infrastructure for SR lithography is now complete.…”

Present status and problems of X-ray lithography

“…Since the basic work ofSchwinger [51] and Sokolov/Temov [52], the interest in this light source, which f'tlls a gap from soft X-ray to vacuum-UV, has grown rapidly in the last few years [53][54][55][56][57][58]. The first attempts to use synchrotron radiation for lithography were made by Spiller et al at DESY in Hamburg, 1978 [59]. These experiments already showits outstanding characteristics in regard to replicating structures in the sub-/am region.…”

“…Although the absorption in the resistis higher too, the loss in the window cannot be compensated; and therefore more powerful sources are required, which could lead to serious problems of temperature rise in the mask and the wafer. Somewhat more complicated is the choice ofthe proper wavelength region, or the range ofthe electron energy ()'max is connected with the energy according to equation (4.4)), assuming the use ofa synchrotron or a storage ring.The first estimations regarding the appropriate wavelength orenergy region have already been carried out by Spiller et al [59].A more detailed optimization calculation regarding exposure time and contrast, in which all technologicalparameters mentioned above are contained, has been carried out in [40]. In this calculation, the quantitative influence of backscattered photoelectronshas also been taken into account.…”

“…Orientational and phenomenological investigations concerning the relation between mask contrast, edge acuity and dose are described in [59]. The reasons for the strong connection have to do with the relatively low mask contrast (exposure beneath the absorber too), the low absorption in the resist(relatively homogeneous dose distribution in the resist), and the very low diffraction and scattering effects (possibility of varying the dose in a wide range).…”