UV exposure system

Dual-Cure (UV + Thermal) Epoxy Resin. The main purpose for using a dualcure epoxy resin is the stability of the B-cured material and the ease with which it can be removed by grinding during planarization. A homogeneous, semicured state can be reached because the liquid environment within the UV exposure system helps to control the temperature and stabilize the intensity of U V Ught. Furthermore, because the temperature of the liquid environment is kept low, the expansion of air bubbles that may have been trapped in the fill material at room temperature is prevented. 

Photochromic silver—copper haUde films were produced by vacuum evaporation and deposition of a mixture of the components onto a sUicate glass substrate (13). The molar ratio of the components was approximately 9 1 (Ag Cu) and film thicknesses were in the range of 0.45—2.05 p.m. Coloration rate upon uv exposure was high but thermal fade rates were very slow when compared with standard silver haUde glass photochromic systems. 

Figure 7. IR spectra of the trimethylolpropane tris(2-mercaptoacetate)/ trimethylolpropane diallyl ether system for three different UV exposure times (0 s, 713 s, 8995 s) showing S-H stretching (2570 cm 1), C=C stretching (1646 cm 1), and aromatic out-of-phase C-H deformation (830 cm 1) peaks. The thiol peak is monitored to calculate the extent of reaction while the C-H deformation peak is used as an internal standard.

Recently, nonionic acid precursors based on nitrobenzyl ester photochemistry have been developed for chemically amplified resist processes (78-80). These ester based materials (Figure 8) exhibit a number of advantages over the onium salt systems. Specifically, the esters are easily synthesized, are soluble in a variety organic solvents, are nonionic in character, and contain no potential device contaminants such as arsenic or antimony. In addition, their absorption characteristics are well suited for deep-UV exposure. 

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. 

Application to the two-layer resist system. Photobleachable resist systems that have a strong absorption before exposure and that bleach completely upon UV exposure alleviate the light reflection from the substrate. A photobleachable resist system formed by means of the doping process liras reported in our previous paper (9). This resist system consists of two layers in which a diazonium salt is distributed in both the top and bottom layers. When exposed to i-line, the diazonium salt in... 

While PMMA is an attractive material because of its resolution characteristics, its sensitivity to radiation induced degradation is low, and its dry-etching characteristics are poor. The e-beam and deep-UV exposure doses for PMMA are —100 nC cm-2 (38) and >1 Jem-2 (40), respectively. The fact that nanometer resolution is readily achieved in this material has, however, prompted many researchers to examine substituted systems in attempts to effect improved performance. 

The schematic processing steps for the two-layer deep-UV PCM system are shown in Table III for near-UV and e-beam exposures, resulting in capped and uncapped profiles respectively. Step 5a is required only for near-UV exposures to average out optical interference effects discussed in Section 6.2.a. Step 6a is used to enhance the AZ to PMMA adhesion and cap retention. Figure 15 shows uncapped 1 - nm lines in a 2 - /im thick PMMA layer. Figure 16 shows the capped image with 0.3 fim AZ on 2 -iLim PMMA. The AZ layer was delineated by a 30 - /iC/cm 25 - keV e-beam in both cases. 

Such a pinhole density test was performed on the AZ/PMMA two-layer deep-UV PCM system (26). The result is shown in Table IX where a pinhole density of 8 and 6 per cm was obtained for the capped (A) and uncapped (B) systems. Because only three wafers were used for each test, the result should be taken only qualitatively and the numerical difference between 6 and 8 pinholes/cm should be taken as being indicative of measurement fluctuations only. It should not be attributed to the use of different developers or O2 plasma because in the subsequent tests of batches C and D in which the DUV exposure was omitted, the numbers were 0 and 1 pinhole/cm with the capped system giving the smaller pinhole density. The low pinhole density in batch E in which the AZ development step was omitted suggests that the pinholes arise during the development of the AZ layer. Presumably, a small portion of the AZ base resin molecules were not linked up with the photoactive compound and therefore still exhibited their intrinsic high solubility in the AZ developer. After development, these high solubility spots became pinholes. These pinholes are apparently larger than the diffraction - limited sizes so that they can be transferred into the PMMA film by deep-UV exposure. 

Experimental systems without irradiation of the reactor, but with (i) Raman spectroscopy with UV or VIS sources (ii) UV-VIS and ECD spectroscopy and (iii) fluorescence spectroscopy, represent special cases. It is possible, even perhaps probable, that the chemistry observed in the sample cell is dissimilar to the chemistry in the CSTR fluid elements. This is particularly worrisome in the cases were UV exposure occurs. Having said that, a test can be performed using exact replicate catalytic runs. For example, in the first mn, the sample cell can be irradiated for the full duration [to < t < tf]. In the second and third case, the sample cell can be irradiated for 50 % and 10 % of the duration. If the same set of observable species are found, and the time dependences of all the observable species are the same between runs, then, to a first approximation, the spectroscopy has not affected the system. In conclusion, cases (i) to (iii) should be treated with caution by the experimentalist. 

Suppression of local (at the site of UV exposure) and systemic (at a distant, unexposed site) immune responses to a variety of antigens has been demonstrated in both humans and animals exposed to UV-B. There is reasonably good evidence that such immunosuppression plays a role in human carcinogenesis however, the implications of such immunosuppression for human infectious diseases are still unknown. 

Drew, H. D., Brower, J. F., Juhl, W. E., and Thornton, L. K. (1998), Quinine photochemistry A proposed chemical actinometer system to monitor UV exposure in photostability studies of pharmaceutical drug substances and drug products, Pharmacopeial Forum, 24(3), 6334. 

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