E. B. Kluenkov

Multilayer Zr/Si filters for EUV lithography and for radiation source metrology

The technique for fabrication of thin film filters with high mechanical strength, capable of withstanding the prolonged heat load of 1 W/cm2, has been developed. Freestanding multilayer Zr/Si filters of size 20×150 mm2 with high transparency of 76% at wavelength λ = 13 nm were manufactured for EUV lithography tool. We have also developed and fabricated various designs of filters (freestanding or mesh supported) with lower transparency of 40-50% for experiments with intensive EUV sources. The tests of differential pressure withstandability and heat-resistance of filter samples were fulfilled. In order to model the influence on the filter of intensive radiation of the lithography source we have tested Zr/Si film samples by the Joule heating in vacuum at residual pressure of 10-8 Torr. The testing consisted in continuous heating of Zr/Si films at the electrical power per area unit from 0.5 W/cm2 to 6 W/cm2 during long period of time (up to 2 months). The influence of the long-term heat load on the transparency of samples at λ = 13 nm and within wavelength region 0.3 - 2 μm was investigated.

Free-standing spectral purity filters for extreme ultraviolet lithography

Free-standing multilayer films consisting of Si, Zr, Mo and silicides of both metals have been fabricated and studied as spectral purity filters (SPF) for extreme ultraviolet (EUV) (13.5 nm) lithography tools. Comparative tests of multilayer SPF structures of various compositions have been performed at high power loads. It was found that a Mo/ZrSi2 structure with MoSi2 capping layers is featured with capability to withstand prolonged heating in vacuum (10−7  mbar) at 900-950°C. A technique of fabrication of large aperture free-standing multilayers was developed, and a pilot sample of the above film structure of 160 mm in diameter, 50 nm thick, with transparency at 13.5 nm above 70% was fabricated as a conceptual prototype of SPFs with large dimensions.

The microstructure and X-ray reflectivity of Mo/Si multilayers

Abstract We have studied microstructure Mo/Si multilayers grown by RF and DC sputtering at different deposition parameters by cross-sectional transmission electron microscopy and X-ray reflectivity for the wavelength 13.4 nm and 0.154 nm. It is shown experimentally that reflection properties of mirrors are determined by the crystalline state of molybdenum layers. The results are compared for the different samples and discussed in view of the choice an optimal deposition parameters to produce multilayers with a high X-ray reflectivity for the λ=13.4 nm.

A stand for a projection EUV nanolithographer-multiplicator with a design resolution of 30 nm

An original stand for a nanolithographer-multiplicator with an operating wavelength of 13.5 nm and a design spatial resolution of 30 nm has been developed in Russia at the Institute for Physics of Microstructures, Russian Academy of Sciences. A detailed description of basic principles and approaches used when constructing the stand and its key elements is given. The experiments planned to be performed using the stand are discussed.

Microstructure and electrical properties of YBCO films

YBCO thin films were fabricated in situ on R-plane sapphire with YSZ buffer layers by inverted cylindrical magnetron sputtering. The films with , transition width , surface microwave resistance at 10 GHz and critical current density at 77 K were routinely fabricated at optimum deposition temperature and gas mixture pressure. The relations between the growth conditions, microstructure and electrical properties of YBCO thin films were investigated for a wide range of deposition temperatures. The variation of the film properties with deposition temperature is substantiated by a thorough analysis of changes in the microstructure and state of Cu-rich particles on the surface YBCO thin films. The particle formation observed in our experiment can be described using the classical thin film nucleation and growth model based on the concept of capture zones.

Influence of annealing on the structural and optical properties of thin multilayer EUV filters containing Zr, Mo, and silicides of these metals

New freestanding multilayers consisting of Zr, Mo and silicides have been fabricated and studied as spectral purity filters for the future generation of projection EUV lithography tools with a wavelength of operation 13 nm. The optical properties of multilayers were measured in EUV, visible and IR spectral ranges. Developed filters combine transparency of 70% at λ = 13 nm with high efficiency of suppression of out-of-band radiation (2-3 orders of magnitude from UV to IR regions). The reflectivity of filters at λ = 10.6 μm, where the spectral intensity of background radiation of laser plasma EUV source is at a maximum, achieves 88%. We have tested the withstandability of new multilayer structures to long-term (3 - 7 hours) vacuum heating by CO2-laser radiation at the power, absorbed per area unit of the specimen, of 8 W/cm2. The annealed samples were studied by secondary ion mass-spectroscopy and optical measurements were also performed. The most promising structure Zr/ZrSi2 coated with MoSi2 layers showed smaller decrease in transparency at λ = 13 nm (from 73% to 68%) than other tested compositions. Freestanding filters of 160 mm in diameter with transparency of 65% at wavelength λ = 13 nm were manufactured for EUV lithography tool.

Manufacturing and investigation of objective lens for ultrahigh resolution lithography facilities

Status of activities in field of manufacturing and investigation of objective lens for ultrahigh resolution lithography facilities carrying out in IPM RAS is reported. Some physical aspects of operation of interferometers with diffraction reference wave are considered. A scheme of a point diffraction interferometer developed in IPM is presented. Last experimental data on making high precision spherical substrates with NA=0.25 are presented. A problem of surface shape measurements of aspherical substrates with a help of a point diffraction interferometer is discussed. A scheme of measurements and experimental data of wave deformation of 6-lens objective are given.

Study of correlation between the microstructure and phase inhomogeneities of Y-Ba-Cu-O epitaxial films and their DC and microwave properties

The influence of various kinds of structure and phase inhomogeneity on electrical properties of YBCO thin films prepared by inverted cylindrical magnetron sputtering has been investigated. A simultaneous analysis of the changes in the microstructure and electrical parameters has allowed us to define the contribution of each kind of inhomogeneity in the restriction of the films electrical parameters. It has been found that the transition temperature depends mainly on deviations of the c-axis lattice parameter from its optimum value, the critical current density depends mainly on the out of plane misorientation of the film domains and the microwave surface resistance depends mainly on the volume of the high-angle misoriented domains. By using atomic force and scanning tunnelling microscopy regions of YBCO films with modified properties around Cu-rich second phase particles were observed. It is suggested that superconducting properties of these regions are worse than the matrix due to Cu depletion. Usually the relative area of these inhomogeneities in our films is about 30% and can occupy up to 50% and, therefore, mostly determines the electrical properties of films. It is suggested that the processes of cation disorder deforming the film lattice play an important role in formation of structure and phase inhomogeneities in YBCO thin films.

Thin film multilayer filters for solar EUV telescopes

Al, with a passband in the wavelength range of 17-60 nm, and Zr, with a passband in the wavelength range of 6.5-17 nm, thin films on a support grid or support membrane are frequently used as UV, visible, and near-IR blocking filters in solar observatories. Although they possess acceptable optical performance, these filters also have some shortcomings such as low mechanical strength and low resistance to oxidation. These shortcomings hinder meeting the requirements for filters of future telescopes. We propose multilayer thin film filters on the basis of Al, Zr, and other materials with improved characteristics. It was demonstrated that stretched multilayer films on a support grid with a mesh size up to 5 mm can withstand vibration loads occurring during spacecraft launch. A large mesh size is preferable for filters of high-resolution solar telescopes, since it allows image distortion caused by light diffraction on the support grid to be avoided. We have investigated the thermal stability of Al/Si and Zr/Si multilayers assuming their possible application as filters in the Intergelioprobe project, in which the observation of coronal plasma will take place close to the Sun. Zr/Si films show high thermal stability and may be used as blocking filters in the wavelength range of 12.5-17 nm. Al/Si films show lower thermal stability: a significant decrease in the films transmission in the EUV spectral range and an increase in the visible spectrum have been observed. We suppose that the low thermal stability of Al/Si films restricts their application in the Intergelioprobe project. Thus, there is a lack of filters for the wavelength range of λ>17  nm. Be/Si and Cr/Si filters have been proposed for the wavelength range near 30.4 nm. Although these filters have lower transparency than Al/Si, they are superior in thermal stability. Multilayer Sc/Al filters with relatively high transmission at a wavelength of 58.4 nm (HeI line) and simultaneously sufficient rejection in the wavelength range near 30.4 nm (HeII line) have been fabricated. They are planned to be used in the project KORTES, whose telescopes will have an EUV channel at 58.4 nm.

Current status and development prospects for multilayer X-ray optics at the Institute for Physics of Microstructures, Russian Academy of Sciences

A real opportunity for applying traditional optical methods to soft X-ray and extreme UV (ultraviolet) radiation bands has appeared thanks to recent successes in the area of multilayer-mirror deposition and procedures for fabricating supersmooth and highly precise substrates of mirrors. The implementation of this opportunity opens up fundamentally new prospectss in the nanodiagnostics of substances, micro- and nanoelectronics, microbiology, solar astronomy and other applications. The main directions in multilayer X-ray optics developed at the Institute for the Physics of Microstructures, Russian Academy of Sciences, are presented and the aspects of the use thereof in science and technology are considered. The main problems arising during the fabrication of multilayer interference structures for the soft X-ray and extreme UV bands are discussed. The main results obtained recently in the scope of each direction of investigation are presented. Plans for the future development of these directions are discussed.