With the intent of finding a sensitive photocathode material in the 130 Å (100eV) X-ray range for use in a high resolution soft X-ray Conversion Microscope, photoelectron yields of several materials (mostly alkali halides), were measured at the National Institute of Standards and Technology's (NIST) Synchrotron Ultraviolet Radiation Facility II (SURF II). These measurements were made as a function of wavelength in the spectral range 115 Å-400 Å. The measured values are comparable to previous measurements of the photoelectron yields of these and similar materials, and to an existing model of photoemission [1–3]. We also determined the effects of prolonged exposure to X-ray light on performance. Moreover, because of the hygroscopic nature of Alkali Iodides, measurements of the photoelectron yield versus wavelength were repeated for samples of CsI that were kept in storage for periods of time to determine the effects of storage time and water absorption on the photoelectron yield.

Boron, a low Z element, is useful for x-ray optics since it has a low atomic absorption coefficient. Boron films prepared by chemical vapor deposition were characterized optically, electronically and mechanically. Auger, infrared and hydrogen effusion analyses showed that the films are amorphous hydrogenated boron. The hydrogen content ranges from 8–71%. The measurements of the complex refractive index and the resistance vs. temperature determined that they are a typical amorphous semiconductor with the energy gap ranging from 1.09 to 1.36 eV, decreasing with increasing hydrogen content and with the Fermi energy level pinned about midgap. The real refractive index at 490 nm increases from 3.25–3.59 with increasing hydrogen content. The Young's modulus and hardness were found to be 3.05 × 1013 dyne/cm2 and around 2500 Vickers, respectively. The chemical tests suggested that boron films are stable in nonoxidizing bases and concentrated acids. Some oxidizing bases such as basic ferricyanide and permanganate solutions are good etchants for CVD boron films. Boron coated beryllium x-ray windows which have enhanced resistance to degradation are now commercially available, and self-supporting boron windows are potential future products for x-ray imaging.

Many properties of LPCVD SiC film as X-ray mask membrane have been investigated in detail. The film has an atomic ratio of 1.0 and negligible impurities, and was found to be damage-free to SR X-rays up to 500 KJ/cm2. An integrated transparency of 1.05 μm thick SiC membrane for SR X-rays was measured to be 76%. The interference peak at 633 nm of optical spectrum has given the membrane of around 1.0 μm in thickness the transmittance peak of 70% and increased to more than 80% after an AR coating or planarizations by polishing and etching-back. The attainable transmittance was found to be limited to about 84%, theoretically and experimentally, due to the absorption of the membrane. The peak transmittance of 87% is obtainable by the AR coating on the polished SiC membrane. The internal stress was found to be independent of thicknesses above 0.6 μm and the measured Young's modulus is 4.5×1011 Pa irrespective of the thickness and stress. Some extremely polished (0.1 nm Ra) and all the etched-back membranes studied withstood breakage at the pressure as high as the as-deposited ones. The stress uniformity in 30 mm square of the membrane was found to be ± 10 % by measuring five local stresses with a bulge method.

Laser Ablation Deposition (LAD) technique was used to produce hydrogen-free SiC films on (100) Si substrate. Deposition temperatures of 300°C and 450°C were investigated. The Si2p and C1s. core levels and the Si-C absorption band of the a-SiC LAD films were characterized by using X-ray Photoelectron Spectroscopy (XPS) and Fourier-Transform Infra Red (FTIR) absorption spectroscopy, respectively. The high compressive stress of the as-deposited SiC films was released and controlled by means of rapid thermal annealing. A correlation between the stress evolution and the Si-C bond density of the annealed films is pointed out. Optical transmission and mechanical properties (stress, Young's modulus) measurements were carried out on the free-standing membranes fabricated from SiC LAD films. The effect of the deposition temperature on the SiC membrane properties is discussed.

In this paper, the kinetics and properties of amorphous LPCVD silicon carbide films synthesized from the single organosilane precursors diethylsilane (DES) or di-tbutylsilane (DTBS) are discussed. For DES, the growth rate is observed to vary linearly with flow rate and pressure, while for DTBS, a square root dependency is seen as a function of these parameters. An Arrhenius type behavior was observed for both chemistries yielding activation energy values of 40 and 25 kcal/mol for DES and DTBS respectively. The elemental composition of the films became progressively richer in carbon as the deposition temperature increased with stoichiometry occurring near 750°C. The film stress was dependent on carbon content and became compressive at compositions near Si0.35C0.65. The hardness and Young's modulus of the films increased with increasing carbon content reaching maxima near stoichiometry. Free-standing membranes produced under optimal processing conditions had a relatively low optical transmission due to excess carbon. Although, transmission characteristics were improved by adding NH3 in the reaction chamber, the resulting silicon carbonitride films exhibited undesirably high values of tensile stress.

Multilayer x-ray lithography membranes were designed and fabricated. Consisting of alternating layers of SiC and SiNx, the membranes were designed to have low reflectance for improved optical alignment of x-ray masks, high fracture strength, superior chemicaletch resistance, and high manufacturing yield. The membranes were prepared from multilayer coatings deposited on silicon wafers in an electron cyclotron resonance chemical vapor deposition system. Membranes with less than 5% reflectance over 150 nm bandwidths were made. External SiNx layers increased the chemical etch resistance of the membranes. The fracture strength was 2–3 times that of SiC, and the membrane yield was 50% higher than that of single-layer SiC. Field-emission SEM of the multilayer coating cross-section showed the presence of 20–150 nm defects near the layer interfaces. The layering confines or stabilizes the defects, thereby increasing the membrane yield and fracture strength.

In x-ray mask repair high Z absorber features, such as gold or tungsten, must be removed or added. The main challenges are the small lateral dimensions (0.25 μm and below) and the thickness of the absorbers (˜ 0.5 μm) The focused ion beam appears to be the best tool developed to meet this challenge. Unwanted features are removed by ion milling while missing absorber is reconstructed using ion induced deposition from a locally piped-in precursor gas. The high aspect ratio of the features complicates both of these processes. Milling away 0.5 μm thick absorber can lead to redeposition of the sputtered material on neighboring features. The crystal grains of the absorber mill at different rates depending on orientation which results in nonuniform features. A possible alternative which only works with W absorber is to use ion assisted etching. In ion induced deposition a precursor gas such as dimethylgold hexafluoro acetylacetonate is provided by a capillary tube aimed at the region scanned by the ion beam. The incident Ga+ ions, usually at energies in the 25–100 keV range, dissociate the adsorbed precursor molecules leaving a deposit of gold mixed with carbon. The carbon content can approach 50 atomic % resulting in an x-ray attenuation which is about one half of that of pure gold. A number of unexplored materials science issues are associated with mask repair including: the reduction of the carbon content, redeposition both from milling and from induced deposition, milling as a function of crystal orientation and energy, and deposition of high aspect features. The technology is well enough developed so that mask repair of 0.25 μm features can be considered. However, a better understanding of the materials science aspects of x-ray mask repair will help to advance the state-of-the-art.

Intra-granular microstructure and stress of tungsten rf magnetron sputtered thin films have been correlated for deposits with stresses ranging from 1000 MPa to −1000 MPa and belonging to the zone T of the Thornton's microstructural diagram. For pure α-W films, the stress values determined from the substrate deflection method were shown to be comparable with those determined by the x-ray diffraction sin2ψ method using the α-W (321) reflection. The lattice parameter a0 of the unstressed material as deduced and was found to depend on the deposition conditions. In addition, a significant broadening of the (321) diffraction peak was observed foi compressive films, which suggests that the intra-granular microstructure has been changed. These original results are interpreted in terms of structural defects: in particular, compressive stress can be related to an interstitial feature.

In this work the stress and grain structure of electrodeposited gold films was determined as a function of time from deposition, with measurements being conducted in time intervals of minutes to days after deposition.

A test structure that allows accurate and unambiguous measurement of out of plane distortion (OPD) was developed. Using this structure the time evolution of the stress of the films was followed using an interferometric microscope. Scanning ion microscopy was used to determine the time evolution of the grain structure of the samples. This technique, based on focused ion beam imaging, allows determination of grain structure of thin films without special sample preparation or restrictions in film thickness.

The sign, magnitude, and stability of the stress at room temperature was found to be a function of the rate of deposition and the concentration of additive in the electrodeposition solution.

For some of the films studied, grain growth from the hundreds of Angstroms to tens of microns was found to occur in a matter of minutes at room temperature.

Sputter-deposited tungsten thin films exhibit high intrinsic stress. This stress can result in both in-plane and out-of-plane distortion when the films are deposited on thin membrane structures such as x-ray masks. To minimize these distortions, intrinsic stresses in these absorber films have to be low and reproducible. Several groups have recently reported that by precisely controlling the sputter deposition conditions, W films with low stresses can be produced. However, the reproducibility is limited. We have built a novel acoustic resonance system, in which one electrode, mounted behind the mask membrane, monitors its position and simultaneously provides an electrostatic drive to keep it vibrating at its resonant frequency. For typical membranes and deposition conditions, vibrational modes in the 1–10 kHz range are observed. During tungsten deposition, sputtering pressure is varied in response to changes in the membrane resonant frequency, so that the film stress is minimized. We have made a systematic study of the microstructure and stress of W thin films using a variety of characterization techniques. We have shown the feasibility of depositing low-stress (<10 MPa) W films by in-situ stress monitoring and control of sputtering pressure. By using a proper combination of substrate heating and sputter power density (thermal engineering), the reproducibility of in-situ stress control is greatly improved. The present experimental results of in-situ stress control during W sputter deposition are very promising for the successful utilization of low stress (<10 MPa) W films as absorbers for x-ray masks.