The principle of the Orbitron pump is described. Its miniaturization is simulated. The application of such an ultra high vacuum pump is based on the availability of electron sources with good resistance against mbar vacuum levels. Especially field emitter cathodes are well suited to supply the active ionizing current. This electron current orbits around an anode. Ions generated along the electron path are extracted to the cathode. This is made from getter material e.g. titanium, which is sputtered by the impinging ions and in turn coats the internal surface of the pump. This generates an active getter film for chemical pumping. Employing a cathode - extractor separation smaller than 1 μm allows to start the pump at a pressure as low as 1 mbar in the cavity. Using electron beam induced deposition, it was shown that a field emitter - extractor configuration can be built with dimensions of < 2 μm in length, width and height. This miniaturized electron gun supplies the required current for the pump of e.g.100 μA. Employing micromechanical technologies, the Orbitron pump can be built and integrated into a MEMS device to supply UHV in a volume of < 1 Mio μm3 on a chip. Connecting the pump with a load vacuum volume, miniature electronic, optical, or mechanical devices, which require a continuous vacuum or even UHV, can be pumped down on chip and operated by only electrical controls.
Klaus Edinger, Hans Becht, Rainer Becker, Volker Bert, Volker Boegli, Michael Budach, Susanne Göhde, Jochen Guyot, Thorsten Hofmann, Ottmar Hoinkis, Alexander Kaya, Hans Koops, Petra Spies, Bernd Weyrauch, Johannes Bihr
High-resolution electron-beam assisted deposition and etching is an enabling technology for current and future generation photo mask repair. NaWoTec in collaboration with LEO Electron Microscopy has developed a mask repair beta tool capable of processing a wide variety of mask types, such as quartz binary masks, phase shift masks, EUV masks, and e-beam projection stencil masks. Specifications currently meet the 65 nm device node requirements, and tool performance is extendible to 45 nm and below. The tool combines LEO's ultra-high resolution Supra SEM platform with NaWoTec's e-beam deposition and etching technology, gas supply and pattern generation hardware, and repair software. It is expected to ship to the first customer in October this year. In this paper, we present the tool platform, its work flow oriented repair software, and associated deposition and etch processes. Unique features are automatic drift compensation, critical edge detection, and arbitrary pattern copy with automatic placement. Repair of clear and opaque programmed defects on Cr, TaN, and MoSi quartz masks, as well as on SiC and Si stencil masks is demonstrated. We show our development roadmap towards a production tool, which will be available by the end of this year.
KEYWORDS: Photomasks, Etching, Electron beams, Ion beams, Lithography, Silicon carbide, Gemini Observatory, Magnetism, Signal attenuation, Electron beam lithography
An electron beam technology for repair of Next Generation Lithography masks is described. Deposition of missing material in clear defects is shown with different material characteristics. Etching of opaque defects is demonstrated. The superiority of the electron beam technology to the well established and widely used focused ion beam techniques is discussed. Electron beam repair avoids the unacceptable transmission loss which is generated by focus ion beam techniques especially for 193 nm and 157 nm lithography by Ga-ion implantation. Shrinking dimensions of printable
defects require higher resolution than ion beams allow, which is, however, obtained routinely with electron beam systems. Specially designed lenses having low aberrations provide outstanding better signal to noise ratio than ion beam systems. Results on deposition and etching of NGL mask relevant materials like TaN, SiC, Mo/Si, and
silicon dioxide is demonstrated. In general 1 keV electrons and a low electron current were used for the etching processes.
KEYWORDS: Photomasks, Electron beams, Etching, Platinum, Interferometers, Charged-particle lithography, Quartz, Silicon carbide, Scanning electron microscopy, Control systems
Electron-beam induced chemical reactions and their applicability to mask repair are investigated. For deposition and chemical etching with a focused electron-beam system, it is required to disperse chemicals in a molecular beam to the area of interest with a well-defined amount of molecules and monolayers per second. For repair of opaque defects the precursor gas reacts with the absorber material of the mask and forms a volatile reaction product, which leaves the surface. In this way the surface atoms are removed layer by layer. For clear defect repair, additional material, which is light absorbing in the UV, is deposited onto the defect area. This material is rendered as a nanocrystalline deposit from metal containing precursors. An experimental electron-beam mask repair system is developed and used to perform exploratory work applicable to photo mask, EUV mask, EPL and LEEPL stencil mask repair. The tool is described and specific repair actions are demonstrated. Platinum deposited features with lateral dimensions down to 20 nm demonstrate the high resolution obtainable with electron beam induced processes, while AFM and AIMS measurements indicate, that specifications for mask repair at the 70 nm device node can be met. In addition, examples of etching quartz, TaN, and silicon carbide stencil masks are given.
Micromechanical devices and systems sometimes require a nanostructured addition or subtraction of material to obtain a more specific functionality. Silicon micro-technology is able to generate smart devices, but is facing a very complex processing to generate nano-structured areas to specialize the device, which are required only in small numbers. Here the very high resolution technique of three-dimensional electron beam nanolithography with chemically induced reactions can help. This technique is performed as a bottom up direct write or etch technique using a dedicated electron beam system with beam control and the possibility to add on chemicals using molecular beams, which can be switched on and off, and with a concentration matching the chemicals required to the lithography action. Etching oxides and carbides allows to structure very hard materials. Depositing oxides, metal or metal carbon compounds allows to add on specific three-dimensional nano-structures. Surfaces can potentially be modified to become specially chemically active or protected, and electronic circuitry can potentially be added in situ, which are built using vacuum micro-electronic devices to amplify or switch signals. This leads to novel nano-analytical devices and many applications. The technology is described. Applications are presented, e.g. in nano-optics with the rapid prototyping of photonic crystals, in nano-electronics with a micro-triode, and in nano biotechnology with surface structures. A comparison of electron-, ion- and laser-beam induced reactions is given.
Volker Boegli, Hans Koops, Michael Budach, Klaus Edinger, Ottmar Hoinkis, Bernd Weyrauch, Rainer Becker, Rudolf Schmidt, Alexander Kaya, Andreas Reinhardt, Stephan Braeuer, Heinz Honold, Johannes Bihr, Jens Greiser, Michael Eisenmann
The applicability of electron-beam induced chemical reactions to mask repair is investigated. To achieve deposition and chemical etching with a focused electron-beam system, it is required to disperse chemicals in a molecular beam to the area of interest with a well-defined amount of molecules and monolayers per second. For repair of opaque defects the precursor gas reacts with the absorber material of the mask and forms a volatile reaction product, which leaves the surface. In this way the surface atoms are removed layer by layer. For clear defect repair, additional material, which is light absorbing in the UV, is deposited onto the defect area. This material is rendered as a nanocrystalline deposit from metal containing precursors. An experimental electron-beam mask repair system is developed and used to perform exploratory work applicable to photo mask, EUV mask, EPL and LEEPL stencil mask repair. The tool is described and specific repair actions are demonstrated. Platinum deposited features with lateral dimensions down to 20 nm demonstrate the high resolution obtainable with electron beam induced processes, while AFM and AIMS measurements indicate, that specifications for mask repair at the 70 nm device node can be met. In addition, examples of etching quartz and TaN are given.
A comparison of the achievements of charged particle beam induced processes as published is evaluated to judge on the applicability of this technology for Next Generation Lithography mask repair. Methods for repair of defects of different types on different masks are reviewed. This compares the achievements of ion beam technologies as well as of electron beam technologies. With these techniques the properties of the deposited materials for open defect repair can be selected using different precursors, currents, temperatures and voltages for the deposition process. Very high resolution is achievable. For opaque defects the etching and trimming of a surplus of absorber or scattering material with electrons or ions is compared.
A method to produce polymer-based passive and active photonic bandgap devices for integrated optics is described. The aim of the method is to implement low-cost active and passive opto-electronic devices of high quality with a high degree of integration and high packing density. A structurable resist or polymer layer of high quality is placed onto an opto-electronic substrate. An etching mask and a high-grade anisotropical in-depth etching process are used to generate a structure which can be used as a photonic bandgap material. The permittivity of the structure is changed by filling the polymer structure with monomers by means of a vapor-phase or liquid-phase diffusion. Depending on the monomer type used for diffusion as well as on temperature and on interaction time, the optical properties of an optical element can be changed selectively. The method described will make possible an increase in the packing density of future integrated optics and low-cost production of large quantities alike.
KEYWORDS: Microlens, Single mode fibers, Quartz, Lithography, Photoresist processing, Scanning electron microscopy, Silicon, Electron microscopes, Image processing, 3D image processing
The fabrication of microlenses on flat and three-dimensional substrates is described. A totally dry resist process is used. The characteristics of this novel process are investigated. A technique for lens positioning and exposure was developed for a scanning electron microscope using an image processor as a beam control system. The hyperbolic profile of the microlenses is computer generated. Microlenses of cylindrical, round, and elliptical geometry were fabricated on a Si wafer and on the end of a monomode quartz fiber. Focusing of infrared light by fabricated microlenses is demonstrated.
Photonic crystals were investigated experimentally in a scaled setup with microwaves in the form of 2D arrays of dielectric rods of high permittivity surrounded by air and are reported in the literature. These crystals render perfect mirrors for a band of wavelengths. Having an impurity built into the structure, transmission filters with a specific narrow bandwidth can be generated. The predominant feature of these structures is, that devices of high finesses are obtained with as few as 6 planes of dielectric rods. The grid constant of the rods is < (lambda) /3, with (lambda) the wavelength used in the device. The rod diameter is < (lambda) /6 and the length of the rods should exceed 2 (lambda) . Therefore photonic crystal elements extend only a few micrometers in the x-, y-, and z- dimension. In combination with monomode-waveguides and applying some areas filled with non-linear optical materials, tunable filters and switches for the routing of light can be built in a very compact way. It is the first time, that 3D additive lithography with electron-beam induced deposition is employed to generate photonic crystals. This technique allows to generate insulating or conductive structures from wires with > 80 nm diameter and micrometers dimensions with a surface roughness below 3 nm. It offers the freedom to taylor the refractive index of the material by selecting precursor materials, deposition conditions, and exposure mode. A scanning electron microscope with VIDAS-beam control system is used for this lithography. A custom designed lithography function allows to control position, dwelltime, and sequence of the pixels. Using a program generated database, which contains all pixel and time information required, 3D structures are generated with the deposition process. The devices are placed with nm precision in waveguide patterns. Macro-controlled construction of arrays of dielectric rods of high aspect ratios is presented, which resemble perfect or imperfect photonic crystals. Using specialized crystals, filters and tunable filters dense devices for routing of light or optical metrology can be fabricated.
Structurization of three-dimensional surfaces has become more and more important for micro- mechanics, micro-electronics, and micro-optics. It is widely accepted that resist processes present fewer hazards to personnel and environment than conventional wet resist processes. Octavinylsilsesquioxan is investigated as a dry negative tone resist. It is employed to structure 250 micrometer deep steep surface steps, to modify fabricated three-dimensional structures with dot gratings for metrology applications, and to generate optical micro-lenses of 6 micrometer to 150 micrometer diameter on wafers and on the end of monomode fibers. The negative tone dry resist, also known as V-T8, enables coating of arbitrary substrates by evaporation in high vacuum. After exposure it is developed in high vacuum by a dry thermal treatment at 200 degrees Celsius. The resist is characterized using layers with a thickness in the range from 50 nm to 1 micrometer. Electrons with an energy ranging from 5 keV to 50 keV are used. The sensitivity of V-T8 films is 40 (mu) C/cm2 at 20 keV, which is orders of magnitude higher than that of other dry resist systems. The resist exhibits high dry etch resistivity. Its contrast is increased from 0.7 to 2.1 using plasma etching in CF4 as a post-development step.
We have realized a new class of high-Q resonant cavity using two-dimensional photonic bandgap (PBG) structures and showed that its Q-value can be as high as approximately 23,000 in the mm-wave regime. We further show that its modal properties, such as the resonant frequency, modal linewidth and number of modes, can be tuned by varying the cavity size. In addition, we present a new nano-fabrication technique for constructing PBG resonant cavities in the near infrared and visible spectral regime.
The procedure for three-dimensional lithography with electron-beam induced deposition is described. The technique can be applied in scanning electron microscopes and does not contaminate the instrument. Various precursor materials with vapor pressures of mtorr at room temperature are investigated with regard to their suitability for different applications. Deposited materials are characterized with respect to topography, morphology, electrical and optical properties by scanning electron microscopy, high resolution transmission electron microscopy, conductivity measurements, and energy dispersive x-ray analysis. The results show, that the properties of deposited nanocrystalline materials can be selected to be insulating or conducting using different currents and voltages for the deposition process. High resolution and high aspect ratio structures are grown with this technique and are applied in many fields. In optics 2-dimensional phonon crystals can be custom designed and produced as filters with a narrow bandgap. For atomic force and scanning tunneling microscopy very fine tips having a high aspect ratio are produced on top of conventional commercial probe tips, or on thermally heated etched tungsten tips, or on fresh cut wire tips. Nanostructurization of materials renders deposited nanocrystalline gold dots of 20 nm diameter and 10 nm distance. K(Omega) to G(Omega) -resistors of a few micrometer in length are components for micro- and nanoelectronics. Electrodes and field electron sources for electron optical microsystems are built under computer control. A micro-tube of 0.25 micrometer in length can be built for vacuum microelectronics.
A numerical study of tips and supertips prone for fieldemission sources is performed using a 3D numerical electron optics package. Special supertips are fabricated with additive lithography under computer control. Different materials are used to generate amorphous or nanocrystalline tips. Its performance is simulated. Additive lithography using electron beam induced deposition allows to design base radii from 50 to 1000 nm. Tip radii and tip length of similar dimensions can be generated. Supertips on top of a deposited tip can have a radius as small as 5 nm. This is achieved using a high resolution scanning electron microscope with a cold field emission source. Gold-tips are constructed on top of Pt/Ir-wire tips. The positioning accuracy is 20 nm. Tips are routinely produced with aspect ratios of 5 to 10 and give an additional field enhancement factor. The influence of the nanocrystallinity of the deposited material to the field enhancement is investigated. Nanocrystals at the tip enhance the field up to a factor of 4. This effect explains the high emission current obtained in experiments from nanocrystalline tips.
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