Binary and phase-shifting chromium on quartz optical photomasks have been successfully investigated with high-pressure/environmental scanning electron microscopy. The successful application of this methodology to semiconductor photomask metrology is new because of the recent availability of a high-pressure SEM instrumentation equipped with high-resolution, highsignal, field emission technology in conjunction with large chamber and sample transfer capabilities. The high-pressure SEM methodology employs a gaseous environment to help diminish the charge build-up that occurs under irradiation with the electron beam. Although very desirable for the charge reduction, this methodology has not been employed much in photomask or wafer metrology until now. This is a new application of this technology to this area, and it shows great promise in the inspection, imaging and metrology of photomasks in a charge-free operational mode. This methodology also holds the potential of similar implications for wafer metrology. For accurate metrology, high-pressure SEM methodology also affords a path that minimizes, if not eliminates, the need for charge modeling. This paper presents some new results in high-pressure SEM metrology of photomasks.
Summary:The scanning electron microscope (SEM) has been frequently used in the pharmaceutical industry for studying pharmaceutical products. However, the technique does not allow for the continuous characterization of a product in both dry and hydrated states without processing the product. Through the recent advent of the environmental scanning electron microscope (ESEM), it is now possible to observe a sample in both the dry and hydrated states without extensive product preparation. The ESEM also allows for continual observation during the hydration process from the dry state until the sample is dissolved. In this study, the ESEM was used to characterize the morphologic differences and hydration patterns of granules formulated with a water-soluble hydrophilic swelling polymer, Polyox ® . Two molecular weights (1,000,000 and 7,000,000) of the polymer were used in concentrations ranging from 10 to 25% w/w. Visual differences in granule surface morphology and differences in hydration patterns were seen in granules prepared from different polymer concentrations. The morphologic data were corroborated by surface area measurements taken on a surface area analyzer. The rate at which the granule dissolved in the ESEM also correlated with the drug dissolution times determined by the standard USP dissolution method.
Historically, SEM developed as a high vacuum technique requiring sample chamber vacuum of 10-5 Torr or better. Energetic electrons scatter from any molecules they encounter, so their creation and transport from source to sample, through the focusing lenses of the electron column, requires high vacuum. This imposes a number of limitations on the kinds of samples that can be examined. Samples must tolerate the vacuum environment and the vacuum system must tolerate the sample. Generally, samples have to be solid, clean, dry, and not contain volatile components. Furthermore, since the vacuum insulates the sample from everything except the stub that supports it, non-conductive samples require a conductive pathway between the scanned region and ground to prevent the accumulation of charge deposited by the beam electrons.
Renewed interest in textile blends of wool and cotton has led to developments in union dyeing (same shade on both wool and cotton fibers) that has potential for increased markets for both fibers as trans-seasonal apparel. The difficulty of efficiently dyeing wool and cotton to the same shade has limited the availability of yarns and fabrics containing blends of both fibers. In fabrics containing blends of cellulosic cotton and proteinaceous wool, it is generally necessary to employ more than one class of dyes and the process involves several steps with adjustments of pH and temperature. The ARS process provides maximum effectiveness and efficiency for one-step union dyeing. It requires pretreatment before dyeing to impart cationic character to cellulosic cotton so that it can compete with protonated wool for a common anionic dye. Three pre-treatments have been applied.
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