Synchrotron radiation exposure

Figure 6. Inorganic resist pattern replicated by synchrotron radiation exposure, width is 0.5...

To test the feasibility of obtaining submicron size patterns in the resist films, an exposure source was used which consisted of the X-ray continuous spectrum produced by synchrotron radiation from the 5 0 MeV storage ring of the University of Orsay (ACO) since synchrotron radiation had been shown previously (2.,8.) to be a suitable source for providing very high resolution due to the small divergence of the beam. The maximum output flux of ACO... 

Figure 4. Scanning electron micrographs of patterns in a 0.8-fim PFEMA film exposed to synchrotron radiation from the French electron synchrotron ACO in Orsay (exposure time 2.5 times shorter than that required for PMMA) and developed in a MIBK/IPA 4 1 mixture at20°C for ISO s...

The authors would like to thank Dr. B. Fay for resist exposures by ACO synchrotron radiation, Dr. P. Parrens from LETI (Grenoble) for measurement of plasma etching rates and the "Direction des Recherches, Etudes et Techniques" (DRET) which partly sponsored this work. 

A 0.4 m thick SPP layer was exposed to X-rays followed by a flood exposure using near UV radiation. The resist was then dip-developed in a 0.8 wt% TMAH solution for 60 s at 25 °C. We used two x-ray exposure systems to evaluate the characteristics of the SPP resist. One is SR-114 which has a source composed of a molybdenum rotating anode with a 0.54 nm Mo-La characteristic line. The exposure was carried out in air. The other has a synchrotron radiation source with a central wavelength of 0.7 nm (KEK Photon Factory Beam Line, BL-1B). The exposure was carried out in vacuum (<10-4 Pa). A positive resist, FBM-G,15) was used as a standard, because its sensitivity only weakly depends on the ambient. 

A variety of alternating copolymers based on H-allyl- and N-(3-ethynylphenyl)maleimides, with substituted styrenes and vinyl ethers, have been prepared and their response to x-ray irradiation studied. Broadband and monochromatic x-ray exposures were conducted at the Stanford Synchrotron Radiation Laboratory. Sensitivities were observed to correlate with mass absorption coefficients of the copolymers and were found to be as high as 5-10 mJ/cm2. Preliminary fine line lithographic studies indicate 0.5 ion resolution capabilities. 

In the laboratory, high spatial resolution, double-crystal topographs can often take several days to expose. The intensity available at synchrotron radiation sources makes the use of this radiation very attractive and exposures at second-... 

It took the short time of one year or so to solve the structure of rhinovirus which causes the common cold. This relied on two major advances in methods. The first was the use of synchrotron radiation in data collection. Nearly a million reflections were collected on the protein crystallography facility at the Cornell Synchrotron source in a matter of days. This conveyed a speed advantage over data collection on a conventional source and also ameliorated an otherwise impossible problem of radiation damage when long exposure times were used. The far greater rate of radiation damage in the X-ray beam in relation to plant viruses is symptomatic of an inherently less stable protein capsid and the absence of quasi-symmetry. The capsid consists of 60 copies each of four proteins and the virus with about 30 % RNA has a total molecular weight of about 8.5 million. 

The excellent characteristics of the IP system as an integrating area detector are well suited to X-ray diffraction and scattering experiments using synchrotron radiation. The system is particularly well suited for biological specimens which require the shortest exposure time or the smallest amount of X-ray dose possible as demonstrated through the applications in this article. 

An ozone treatment (10 minutes at room temperature) of the HF-etched SiC surface before the metallization step was introduced as a very convenient processing step to produce Schottky diode gas sensors with an increased stability and reproducibility. The use of spectroscopic ellipsometry analysis and also photoelectron spectroscopy using synchrotron radiation showed that an oxide, 1-nm in thickness, was formed by the ozone exposure [74, 75]. The oxide was also found to be close to stochiometric SiO in composition. This thin oxide increased the stability of the SiC Schottky diodes considerably, without the need for any further interfacial layer such as Ta or TaSi which have been frequently used. Schottky diodes employing a porous Pt gate electrode and the ozone-produced interfacial layer have been successfully operated in both diesel exhausts and flue gases [76, 77]. 

Another example of the interaction of water with a relatively simple metal oxide surface is provided by the water vapor/a-Al203(0001) system (Figure 7.9(a)). Oxygen Is synchrotron radiation photoemission results indicate that significant dissociative chemisorption of water molecules does not occur below 1 torr p(H20) [149]. However, following exposure of the alumina (0001) surface to water vapor above this threshold p(H20) , a low kinetic energy feature in the Is spectrum grows quickly,... 

Accordingly, by courtesy of the Stanford Synchrotron Radiation Laboratory, some time was made available for exposure of film samples to synchrotron radiation. The window size on the beam line was 2 mm x 12 mm. During exposure the machine was running at 10-13 ma and at an energy of... 

X-ray scattering from molecules in dilute solution is a classic technique dating back to the use of static X-ray tube sources in the 1960s and earlier. However, the relatively low X-ray flux from such sources makes the acquisition of an X-ray scattering profile a matter of hours of exposure. More recently, the use of synchrotron radiation X-rays has made the acquisition of SAXS data much faster, down to a fraction of second exposure time on third generation electron storage ring sources. 

Ultraviolet photoemission spectroscopy( UPS) measurements of a Pd/ SiCVa-Si H structure indicate (Fortunato et al., 1984) that the mechanism responsible for the transport property variations is a change in the contact potential. In these experiments a few angstroms of a-Si have been deposited by an in situ evaporation onto a Pd/SiO substrate. Figure 5 shows the photoemission spectra obtained by synchrotron radiation at a photon energy of 30 eV and for three different conditions (1) after the a-Si deposition, (2) after the H2 exposure at 10-2 Torr for 2 min, and (3) after 02 exposure at 5 X 10-5 Torr and 110°C for 7 min. 

XAFS spectroscopy has been used frequently to determine the oxidation state of an element as a catalyst is subjected to treatments such as reduction, oxidation, or exposure to some reactant. It is the near edge of the X-ray absorption spectrum, the XANES region that is usually used for these measurements. As mentioned in the introduction, the first to recognize the value of XANES for this type of investigation was van Nord-strand (1960), and his report appeared well before the advent of synchrotron radiation sources. 

X-ray white-beam synchrotron radiation topograph was carried on with the energy 2.2013GeV, beam intensity 82.4mA, lifetime 23.8h in the Beijing Synchrotron Radiation Faculty (BSRF). The exposure time was fixed to be 3-6 seconds according to the distance between wafers and slit, area and beam intensity. Photos with different sizes were obtained by adjusting the size of the film and slit. 

Van Buuren et al. [105] performed photoemission and X-ray absorption experiments on Si nanocrystals to determine the TVB and BCB shifts, respectively, as a function of size. The Si nanocrystals were grown in situ at 1700 °C in an Ar gas buffer of 112 mTorr followed by hydrogen exposure to passivate the surface. The resolution of the photoemission and absorption measurements carried out on a synchrotron radiation source were 0.25 eV and 0.05 eV, respectively. They observed a valence band to conduction band shift ratio of 2 1 for all sizes of Si nanocrystals. This is in agreement with various calculations reported for Si nanocrystals [106]. 

White beam synchrotron radiation was used in a topographical study [64] of the phase transition in [Ni(en)2 (NCS)2J single crystals. The short exposure times possible using this intense radiation enabled the strained centre of the crystal to be identified as the most imperfect zone, within which the nucleation and growth process was initiated. The phase transition commenced at defect sites. The role of generation and relaxation of mechanical stresses in influencing kinetics of solid state transformations was later reviewed [65]. 

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