Ellipsometric Scatterometry for the Metrology of Sub-0.1- num-Linewidth Structures.

We describe a modification to our existing scatterometry technique for extracting the relative phase and amplitude of the electric field diffracted from a grating. This modification represents a novel combination of aspects of ellipsometry and scatterometry to provide improved sensitivity to small variations in the linewidth of subwavelength gratings compared with conventional scatterometer measurements. We present preliminary theoretical and experimental results that illustrate the possibility of the ellipsometric scatterometry technique providing a metrology tool for characterizing sub-0.1-mum-linewidth.

Comparison of pentobarbital alone and pentobarbital in combination with lidocaine for euthanasia of dogs.

Pentobarbital alone, pentobarbital plus 1% lidocaine solution, pentobarbital plus 2% lidocaine solution, and pentobarbital plus 3% lidocaine solution were each used to euthanatize 6 dogs. For each dog, time between the beginning of injection of the euthanasia solution and each of the following events was recorded: collapse, onset of apnea, flat-line electrocardiogram, flat-line electroencephalogram, loss of palpable heartbeat, and loss of palpable pulse. Any signs of pain or discomfort were also recorded. There were no significant differences among groups except for time to flat-line electrocardiogram. Dogs euthanatized with pentobarbital alone had significantly longer times than did dogs euthanatized with pentobarbital in combination with any of the lidocaine concentrations. We concluded that pentobarbital in combination with lidocaine was a reasonable alternative to pentobarbital alone when euthanatizing dogs.

Correlation between substrate preparation technique and scatter observed from optical coatings.

We present experimental evidence of the dependence of coating scatter on a substrate preparation technique for fused silica substrates. Samples included conventionally polished, superpolished, andfloat-polished substrates. We used scatterometry and total internal reflection microscopy to investigate the effects of substrate preparation on the performance of zirconium oxide thin films. Results indicate that scatter from coatings dominates the scatter signature of the coated optic. They also demonstrate that substrate preparation can affect the level of scatter produced in optical coatings. In addition it is observed that the substrates with the lowest scatter do not necessarily result in the coatings with the lowest scatter.

Cloning and restriction endonuclease mapping of the genome of an equine herpesvirus 4 (equine rhinopneumonitis virus), strain 405/76.

Purified virion DNA of an Australian isolate of equine herpesvirus 4(EHV 4.405/76) was digested with restriction enzymes and the DNA fragments were cloned into pUC19. The resulting recombinant plasmid library, representing 92% of the virus genome, was used in hybridization analyses to construct restriction maps for BamHI, EcoRI, and SalI for the EHV4 genome. The results show that the genome of EHV 4.405/76 was approximately 145 kb and comprised a unique long (UL) region of 112 kb and a unique short (US) region of 12.4 kb. US is flanked by an internal and terminal repetitive sequence (IRS and TRS) of about 10.3 kb. The BamHI and EcoRI restriction maps are similar to those previously published for an English isolate EHV 4.1942 strain although some differences such as location of an additional fragment and changes in positions of two other small fragments were found.

Linewidth measurement of gratings on photomasks: a simple technique.

A novel laser scatterometer linewidth measurement tool has been developed for critical dimension metrology of photomasks. Calculation of the linewidth is based on a rigorous theoretical model, thus eliminating the need for calibrations. In addition the effect of the glass substrate on which the photomask grating is placed is explicitly taken into account. The experimental arrangement consists of a chrome photomask diffraction grating that is illuminated with a laser. A rigorous theoretical model is used to provide a lookup table that gives the power in the transmitted zero-order beam as a function of the linewidth for a fixed pitch of the grating. The predicted linewidth values are compared with those that are obtained by using commercial optical linewidth measurement systems, and excellent agreement is obtained.

Microstructure characterization by angle-resolved scatter and comparison to measurements made by other techniques.

The theory and measurement of angle-resolved scatter are described. Values of rms roughness that were obtained by using this technique to characterize four different materials are compared with values that were obtained by using a total integrated scatter measuring instrument, an optical profiler, and a mechanical profiler. The spatial frequency bandwidths and modulation transfer functions of the four instruments are different, and results are described in light of these differences.

Etching of high-reflecting thin-film assemblies using ion-beam-figuring techniques.

Ion-beam-figuring techniques have been applied to fabricate high-power transmission gratings for use in photoacoustic spectroscopy. A thin-film assembly of SiO(2) and TiO(2) layers on an SiO(2) substrate provides a high-reflecting characteristic at a desired wavelength. With standard photolithographic techniques a grating pattern is developed on the surface of the assembly then ion etched with ion-beam-figuring techniques. These gratings exhibit an increased factor of 25 in acoustic signal levels when compared with previously used chemical-etched silicon gratings. This increase was obtained owing to higher transmission, less thermal distortion, and the ability to withstand higher incident power levels.

High-sensitivity surface-photoacoustic spectroscopy.

The sensitivity of surface-acoustic-wave detection is extended by several orders of magnitude to a surface-specific absorbance of alphal ~ 10(-9) for a power density of 1 GW/cm(2) using a narrow-bandwidth interdigitated surface-acousticwave detector and an optical irradiation pattern to provide a matched acoustic signal. Major advantages include narrow-bandwidth detection and a large irradiated area that permits more optical energy on the sample. A rapid, nondestructive, reproducible liquid-bonding technique, which permits the extension of these measurements to a wide variety of samples, is demonstrated. Results for AlN and ZrO(2) films (alphal ~ 10(-4)) and fused-silica substrates (alphal ~ 10(-6)-10(-7)) are reported.