Poly thick film

Figure 8.19 Two-diaenslonal separation of the components of a coal derived gasoline fraction using live switching. Column A was 121 n open tubular column coated with poly(ethelene glycol) and column B a 64 m poly(dimethylsiloxane) thick film column. Both columns were temperature programmed independently taking advantage of the two oven configuration. Peak identification 1 acetone, 2 2-butanone, 3 > benzene, 4 isopropylmethylketone, 5 isoprop-anol, 6 ethanol, 7 toluene, 8 => propionitrile, 9 acetonitrile, 10 isobutanol, 11 — 1-propanol, and 12 = 1-butanol. (Reproduced with permission from Siemens AG).

Figure 3.81 Typical cyclic voltammograms of a poly pyrrole film on Pt in Nrsatu rated 1 M NaClOj. The voltammograms were collected immediately after holding the film at -0.6 V vs, SCE for 5 min and after cycling for 5 min. The scan rate was 100 mV s "1 and the film thickness 84 nm. Reprinted from Electrochimica Acta, 36, P.A, Christensen and A. Hamnett, In situ Spectroscopic Investigations of the Growth, Electrochemical Cycling and Overoxidation of Polypyrrole in Aqueous Solution , pp. 1263-1286(1991), with kind permission from Pergamon Press Ltd., Headington Hill Hall, Oxford OX3 0BW, UK.

Electrosynthesis of polymers compares favorably with the thick film method providing addressable and controlled deposition. In terms of selectivity to hydrogen peroxide in the presence of interferents, the most promising results were obtained with poly-l,2-diaminobenzene (poly-1,2-DAB)-modified electrodes [125],... 

The copyrolysis of 1 wt% dibromotetrafluoro-p-xylylene with commercially available hexafluoro-p-xylene (Aldrich) with metals was examined and it was found that it was indeed possible to prepare films that were spectroscopically indistinguishable from those deposited from dimer. The PA-F films obtained are of excellent quality, having dielectric constants of2.2-2.3 at 1 MHz and dissociation temperatures up to 530°C in N2. A uniformity of better than 10% can be routinely achieved with a 0.5-gm-thick film on a 5-in. silicon wafer with no measurable impurities as determined by XPS. During a typical deposition, the precursor was maintained at 50°C, the reaction zone (a ceramic tube packed with Cu or Ni) was kept at 375-550°C, and the substrate was cooled to -10 to -20°C. The deposited film had an atomic composition, C F 0 = 66 33 1 3 as determined by XPS. Except for 0, no impurities were detected. Within instrumental error, the film is stoichiometric. Poly(tetrafluoro-p-xylylene) has a theoretical composition ofC F = 2 1. Figure 18.2 illustrates the XPS ofthe binding energy... 

Sensitivity data for 193 nm exposures were obtained by imaging 1 mm to 1 cm diameter spots in a 1.2 pm thick poly(styrene) film using a Questek ArF excimer laser. Sensitivity was found to be a function of the fluence. For example, one pulse was sufficient to result in a full thickness image after treatment with TiCU and O2 RIE when the fluence was 6 mJ/cm2/pulse (Figure 10). Considerably more dose (32 mJ/cm2) was required to obtain the same result when the fluence was 1... 

Figure 11. SEM of 0.4 pm line and space patterns in a 1.2 pm thick chlorinated poly(styrene) film exposed with 250 mJ/cm2 of 248 nm light, treated with TiCl4 and developed by O2 RIE.

Figure 13. Absorption spectrum of a 1 im thick poly(styrene) film on a quartz disc.

TiCU readily functionalizes hydrophilic polymers such as poly(vinyl alcohol), m-ciesol novolac and methacrylic acid copolymers as well as moderately hydrophobic polymers such as poly(methyl methacrylate), poly(vinyl acetate), poly(benzyl methacrylate) and fully acetylated m-cresol novolac. HCI4 did not react with poly(styrene) to form etch resistant films indicating that very hydrophobic films follow a different reaction pathway. RBS analysis revealed that Ti is present only on the surface of hydrophilic and moderately hydrophobic polymer films, whereas it was found diffused through the entire thickness of the poly(styrene) films. The reaction pathways of hydrophilic and hydrophobic polymers with HCI4 are different because TiCl is hydrolysed by the surface water at the hydrophilic polymer surfaces to form an etch resistant T1O2 layer. Lack of such surface water in hydrophobic polymers explains the absence of a surface TiC>2 layer and the poor etching selectivities. 

A photooxidative scheme has been developed to pattern sub half-micron images in single layer resist schemes by photochemical generation of hydrophilic sites in hydrophobic polymers such as poly(styrene) and chlorinated poly(styrene) and by selective functionalization of these hydrophilic sites with TiCU followed by O2 RIE development. Sub half-micron features were resolved in 1-2 pm thick chlorinated poly(styrene) films with exposures at 248 nm on a KrF excimer laser stepper. The polymers are much more sensitive to 193 nm (sensitivity 3-32 mJ/cm2) than to 248 nm radiation (sensitivity -200 mJ/cm2) because of then-intense absorption at 193 nm. 

As expected, the degree of leveling was superior to that achieved by 2 nm thick films, and the poly(a-methylstyrene) film achieved better planarization over the wider holes. The improvement in the planarity of the film profiles was extended to holes as wide as 500 /zm by doubling the film thickness. 

UV spectra of both polymers IV and V taken from ca. ljim thick films showed that the each of the polymers had absorbencies of less than 0.30 per micron of film thickness at 254 nm as shown in Figure 6 for polymer V. This allows their use with triarylsulfonium salts, which generally absorb in the deep UV. In addition, it is known that poly(4-hydroxystyrene) does not absorb strongly in the deep UV, while poly(3,5-dimethyl-4-hydroxystyrene) also shows no strong absorption band near 254 nm (Figure 6). 

The stir bar is coated with a thick film of poly(dimethylsiloxane) (PDMS), in which the aqueous sample extraction takes place during stirring for a predetermined time. Alter that time it is removed and placed into a glass tube, which is transferred into a thermal desorption system where the analytes are thermally recovered and evaluated online with a capillary MDGC-MS system (Fig. 17.8). 

J. Wang, M. Pumera, M.P. Chatrathi, A. Rodriguez, S. Spillman, R.S. Martin and S.M. Lunte, Thick-film electrochemical detectors for poly(dimethylsiloxane)-based microchip capillary electrophoresis, Electroanalysis, 14 (2002) 1251-1255. 

---