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Fresnel zone plates for x-ray focusing optics are typically made using lithographic techniques. To achieve optimum efficiency for hard x rays, a depth of several microns is required, which limits the minimum zone width and hence minimum focal spot size achievable using lithography. We are exploring the fabrication of zone plates by an alternative technique that surmounts these limitations: the growth of a multilayer film to be used in transmission (Laue) diffraction geometry, in which the thickness of consecutive layers gradually increases according to the Fresnel zone formula; the film is sectioned after growth to the required depth. For a planar multilayer, this produces a linear zone plate that can focus x rays in one dimension. Here we report the growth and characterization of a depth-graded multilayer suitable for use as a zone plate for hard x-ray focusing. The multilayer has a total of 470 alternating layers of WSi2 and Si with thicknesses increasing monotonically from 15 to 60 nm, for a total thickness of 11.33 μm. One of the major challenges is to understand and select the right material system for this kind of thick multilayer. We have found that WSi2/Si is a promising system. A comparison between WSi2/Si and W/Si multilayers is presented. [ABSTRACT FROM AUTHOR]

Direct-write soft x-ray lithography with an ∼50 nm diameter beam is used to pattern features in hydrogen silsesquioxane (HSQ) thin films. Scanning transmission x-ray microscopy of the undeveloped patterns (latent patterns) at the oxygen K-edge reveals a two-stage cross-linking mechanism. Oxygen and silicon near edge x-ray absorption fine structure spectra of latent patterns show an increase in oxygen content and no change in silicon content within exposed regions. A dose and thickness dependent spatial spread of the cross-linking reaction beyond the exposure boundaries is observed and quantified in detail. Strong area-dependent exposure sensitivity (attributed to cross-linking beyond the exposed region) is observed in latent patterns. A lateral spread in the cross-linking of >70 nm (full width at half maximum) is observed on both sides of the lines created with 580 eV x-rays (λ=2.14 nm) in 330±50 nm thick HSQ films at low dose (0.6±0.3 MGy, 27±12 mJ/cm2) (1 MGy=106 J/kg absorbed energy). At a higher dose (111±29 MGy, 5143±1027 mJ/cm2), this spread increased to 150 nm. Preliminary results indicate that latent line widths increased with increasing delay between film spin-coating and exposure. Sharper lines are observed after room temperature development of the latent HSQ patterns in NaOH/NaCl solution (onset dose of 3.9±1.0 MGy, 181±36 mJ/cm2) due to the removal of material below a critical degree of cross-linking. Given the short range of low energy secondary electrons in condensed media (<10 nm at ≤580 eV), the observed spread is likely due to the propagation of reactive ions or radicals beyond the exposed regions. [ABSTRACT FROM AUTHOR]

LIGA process has been developed in the 2.5-dimensional world. We introduced new technologies of a 3D X-ray lithography and a worm injection molding with an unscrewing de-molding mechanism, and succeeded in the deployment of a 3D LIGA process. Furthermore, we fabricated a spiral microcoil using the 3D-LIGA process and a metallization technique combining flat and smooth electroplating and isotropic chemical etching. The microcoil diameter was 0.5 mm and the length was 1 mm. The width of coil lines was 10µm and the pitch was 20µm. Characteristics of this microcoil as an inductor combine the inductance of 91 nH and the quality factor of 5.8 at the frequency of 1 GHz. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(1): 43–51, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20679 [ABSTRACT FROM AUTHOR]

Abstract We have investigated and report in this paper the factors influencing the deformation caused by the dependence between the absorbed X-ray energy on the resist and the shape of the absorber on the X-ray mask. Based on the measurement of errors that occurred during the transferring process between the 2-D shape of mask pattern and the resulting wall of the fabricated 3-D structure, we have developed newly useful graphical data on the absorbed X-ray energy, dosage, and shape of a microstructure. As a result, it is being reported as a method for compensation for the deformed shape after the fabrication of a quadruplets-microneedle. We have considered a number of factors affecting the deformation and finally realized that the effect of a dose?depth nonlinear curve is the most possible cause. Without the compensation of the mask design, we could observe the deformed shapes of the sloped sidewall on the exposed structures. Polymethylmethacrylate microneedle structures fabricated by X-ray lithography with an additional plane-pattern to cross-section transfers technique are directly influenced by the absorber on the X-ray mask pattern. The sidewall of the microneedle was improved by changing the mask pattern from a double right-triangular pattern to a double semi-circular pattern, modeled by comparing the results from a mask-pattern and the actual structure. [ABSTRACT FROM AUTHOR]

This paper presents a systematic study on a novel 3D (three-dimensional) UV (ultraviolet) lithography apparatus for thick photoresist and a UV lithography process simulation for 3D microstructuring. In order to realize a wide variety of 3D microstructures, the developed proximity 3D UV lithography apparatus adopts the 'moving mask lithography' concept which was originally proposed by the authors for deep x-ray lithography. Furthermore, the authors propose a new practical photoresist profile simulation approach adopting the 'fast marching method' to consider the photoresist dissolution vector in the development process. A series of moving mask UV lithography experiments using a positive-tone photoresist (50 µm thickness) successfully confirmed (1) the capability of the moving mask UV exposure technique for 3D microstructuring and (2) the validity of the proposed photoresist profile simulation. [ABSTRACT FROM AUTHOR]

This paper presents a newly developed 3-Dimensional (3-D) simulation system for Moving Mask Deep X-ray Lithography (M²DXL) technique, and its validation. The simulation system named X-ray Lithography Simulation System for 3-Dimensional Fabrication (X3D) is tailored to simulate a fabrication process of 3-D microstructures by M²DXL. X3D consists of three modules: mask generation, exposure and resist development (hereafter development). The exposure module calculates a dose distribution in resist using an X-ray mask pattern and its movement trajectory. The dose is then converted to a resist dissolution rate. The development module adopted the "Fast Marching Method" technique to calculate the 3-D dissolution process and resultant 3-D microstructures. This technique takes into account resist dissolution direction that is required by 3-D X-ray lithography simulation. The comparison between simulation results and measurements of "stairs-like" dose deposition pattern by M²DXL showed that X3D correctly predicts the 3-D dissolution process of exposed PMMA. [ABSTRACT FROM AUTHOR]

This study proposes a general methodology for estimating the depth profile of the heat source of the thermal transport system during deep X-ray lithography. The exposure process in a lithography system is considered as an inverse heat conduction problem with an unknown heat source. The conjugate gradient method is used to solve the inverse problem. Numerical results confirm that the method proposed herein can accurately estimate the heat source even involving the inevitable measurement errors. Furthermore, this methodology can also be applied to estimate the local distribution of temperatures when using scanning thermal microscopy (SThM) to microthermally machine materials and will contribute to increase the quality of microthermally machined products. In addition, a thermomechanical data-storage system, which utilizes a resistively heated atomic-force-microscopy (AFM) cantilever tip to read and write data bits, can also adopt this inverse methodology to control the temperature of a polymer substrate. [ABSTRACT FROM AUTHOR]

We discuss the fabrication of anodized aluminum nanopore arrays by electrochemical means using inexpensive and readily available equipment. The arrays of pores exhibit short-range hexagonal order, with diameters ranging from ∼7 nm to hundreds of nanometers. The pore diameter and spacing are varied by changing the anodization conditions. We have used nanopore arrays to fabricate arrays of bismuth nanowires and as masks for x-ray lithography. [ABSTRACT FROM AUTHOR]

Conditions are determined for the formation of X-ray refractive lenses with kinoform fern-like profile in resist layers of PMMA and SU-8 by deep X-ray lithography. Based on the simulation results of the main steps of mask fabrication and pattern formation the technological process parameters have been defined. The features of microstructure formation in polymer layers more than 100 μm thick are described. The properties of the obtained microstructures have been analyzed. First tests have been performed with SU-8 lenses. The preliminary measured spot size is less a 8.2 μm. [Copyright &y& Elsevier]

An anodized aluminum oxide nanopore has been used as an x-ray lithography mask to achieve a feature size of ∼35 nm on the polymethylmethacrylate photoresist. The mask was exposed using synchrotron radiation and demonstrates the feasibility of forming large arrays of regular nanostructures. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]