Vacuum-electron-beam exposure

THE DIAZOKETONE/RESIN SYSTEM VACUUM ELECTRON BEAM EXPOSURE... 

For the case of the vacuum electron beam exposures we have two observations that apparently lead to a paradox. The first is electron beam exposure produces a ketene but with a much lower yield at low temperatures this is shown in Fig. 5 by the characteristic C C=0 stretching frequency at 2130 cm which appears upon irradiation. The. second is that the carboxylic acid ester does not appear to be formed when the vacuum electron beam exposures arc performed at room temperature. A comparison of Figs. 6 7 supports this claim for example. Fig. 6 summarizes the results for a UV exposure of the system to demonstrate the major IR absorption for the ester Fig. 7 contains the results for the electron beam exposure under identical conditions and. shows that the C=0 band for the e.stcr at =s 17.50 is not evident. 

If the ketene was produced via a Wolff rearrangement at low temperature then the carboxylic acid c.ster. should certainly form as a result of the room temperature exposure. In view of this we conclude that the mechanism for the vacuum electron beam exposure docs not involve a Wolff rearrangement. Instead we propose that-a carbene formed by loss of Aj from the diazoketone plays a central role in the chemistry that ensues after electron beam exposure. The propo.sed mechanism for the electron beam induced chemistry discu.ssed thus far is summarized in the scheme below. 

Even though the vacuum-oriented surface techniques yield much useful information about the chemistry of a surface, their use is not totally without problems. Hydrated surfaces, for example, are susceptible to dehydration due to the vacuum and localized sample heating induced by x-ray and electron beams. Still, successful studies have been conducted on aquated inorganic salts (3), water on metals (3), and hydrated iron oxide minerals (4). Even aqueous solutions themselves have been studied by x-ray photoelectron spectroscopy (j>). The reader should also remember that even dry samples can sometimes undergo deterioration under the proper circumstances. In most cases, however, alterations in the sample surface can be detected by monitoring the spectra as a function of time of x-ray or electron beam exposure and by a careful, visual inspection of the sample. 

Figure 19. The fraction of film remaining after electron beam exposure and development as a function of vacuum curing time for three negative...

Aldehyde Copolymer Self Developing Electron-beam Resists. The ceiling temperature for the copolymerization of aliphatic aldehydes is usually below 0°C and the copolymers are easily depolymerized into monomeric aldehydes above 150°C under vacuum. This depolymerization into monomers also occurs on electron-beam or X-ray exposure as evidenced by combined gas-liquid partition chromatography-mass spectrometry. As a result, the copolymers of aldehydes behaved as self-developing positive resists and almost complete development was accomplished without any solvent treatment. Electron-beam exposure characteristics of the aliphatic aldehyde copolymers studied here are... 

Lithography. Electron beam exposures were carried out with an IBM vector scan e-beam exposure tool at 20 keV. X-ray exposures were carried out under vacuum by Al-Ka radiation, and UV exposures with a Cannon PLA 500, Oriel illuminator, Hybrid Technology Group Model 345-10, or Optical Associates Inc. Model 780 in contact... 

Both characteristic X-ray line and continuous spectra were used to evaluate the performances of the resists. To determine exposure parameters (i.e. sensitivity and contrast) irradiations were carried gut in this study using the aluminum Kot- 2 emission line at 8.3t A generated by means of a modified Vacuum Generators Limited model EG-2 electron beam evaporation gun. The resist samples were exposed through a mask (A) consisting of a range of aluminum foils of different thicknesses supported on an absorbing nickel frame in order to vary the X-ray flux. 

Cross sections of the 2-layer and 4-layer devices are shown in Fig. 16.9 (a) and (b), respectively. Our samples were prepared by an Electron Beam Lithography system. The exposure was carried out for 2 psec by a pixel map of 60000x60000 dots to give a total exposure area of 1.2x 1.2 mm. Next, SO nm of organic Alq3 and subsequent 20 nm of gold were deposited on the grating by a thermal evaporator with vacuum level and evaporation rate of approximately 2 10" Torr and 0.2 A/s, respectively. 

Uhrathin sectioning is the penultimate step in a sequential protocol involving fixation, dehydration, and embedding of a specimen. The protocol itself is devised to preserve the specimen in as lifelike a state as possible, to prepare it for the process of uhrathin sectioning, exposure to the vacuum and electron beam of the microscope, and to impart enough contrast to permit imaging all this is done with a minimum of introduced artifacts. 

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