Composite resist

Interest in solution inhibition resist systems is not limited to photoresist technology. Systems that are sensitive to electron-beam irradiation have also been of active interest. While conventional positive photoresists may be used for e-beam applications (31,32), they exhibit poor sensitivity and alternatives are desirable. Bowden, et al, at AT T Bell Laboratories, developed a novel, novolac-poly(2-methyl-l-pentene sulfone) (PMPS) composite resist, NPR (Figure 9) (33,34). PMPS, which acts as a dissolution inhibitor for the novolac resin, undergoes spontaneous depolymerization upon irradiation (35). Subsequent vaporization facilitates aqueous base removal of the exposed regions. Resist systems based on this chemistry have also been reported by other workers (36,37). 

Materials Resist composition Resist thickness Resist Tg /im C... 

Formulation of Resist Solutions. Forty grams of a Novolak resin was mixed with 10 g of the photoactive compound, and dissolved in 100 g of bis-2-methoxy-ethylether. After wafers were spin-coated, the samples were immediately placed on a hot plate at 82 C for 14 min. The formulation procedure of a composite resist of poly (2-methyl-1-pentene sulfone) in the Novolak resin is as follows the polysulfone was mixed with the resin (13 wt% solid), and then dissolved in 2-methoxyethyl acetate the films were spin-coated onto silicon wafers, and then baked at 100°C for 20 min prior to electron beam exposure. 

Figure 1. Dissolution rates of a composite resist made of a diazonaphthoquinone sensitizer and o-chloro-m-cresol-formaldehyde Novolak resin after 5 /cm2 electron beam exposures. Note this kind of an induction period appeared only in the high-molecular-weight fraction resin.

The nonpolarizable interface has been defined above (Section 6.3.3) as one which, at constant solution composition, resists any change in potential due to a change in cell potential. This implies that (3s Ma< )/3V)jl = 0. However, the inner potential difference at such an interface can change with solution composition hence, Eq. (6.89) can be rewritten in the form of dM7ds< > = (RT/ZjF) d In a, which is the Nemst equation [see Eq. (7.51)] in differential form for a single interface. 

Metal Solvent system Electrolyte Surface film composition Resistivity Q cm Ref. 

Composition Resistivity, p (fl cm) Dielectric Constant, e Dielectric Dispersion, tan 6 Applications... 

We wish to report first dry developable photoresists with poly(olefin sulfones) with photosensitizers like pyridine N-oxide, and then we present our study on composite resists made of poly(olefin sulfones) with novolac resins or with poly(p-hydroxystyrenes). 

Figure 7 shows photo-images obtained with the composite resist made of poly(2-methyl-l-pentene sulfone) and Varcum positive tone patterns are shown on the left, and negative tone patterns on the right. The resists films were spin-coated onto silicon wafers from an AZ-thinner solution of poly(2-methyl-l-pentene sulfone) (16.5 wt% in solid) and Varcum, and prebaked at 100°C for 20 min. The UV exposures were carried out with a medium pressure mercury lamp with a dose of 200 mJ/cm2 of 254 nm light it can be reduced to 100 mJ/cm2 for full development. 

In all these studies, UV light in a region from 250 to 300 nm has been used to degrade poly(olefin sulfones) via energy transfer from the host resin in the case of composite resists with Varcum, and from sensitizers in the case of... 

FIGURE 5.12 Composite resistivity as a function of filler volume loading and filler type. 

A = fraction of superconductor by volume fio = permeability of free space p = composite resistivity Pa = dynamic resistivity Px = resistivity transverse to the filaments Pll = resistivity parallel to the filaments Te = eddy current (coupling current) relaxation time Th = hysteresis driven transport current relaxation time constant... 

R. Riedel, H. J. Kleebe, H. Schonfelder, and F. Aldinger, A Covalent Micro/Nano-Composite Resistant to High-Temperature Oxidation, Nature, 1995, 374, 526-528. 

In Eq. (29), Rjn is the measurement resistor (across which the current or photocurrent is measured) and Rg is the electrolyte resistance. The term C is the capacitance, which, in the metal case, is the Helmholtz layer capacitance, Ch- (Once again, the Gouy region is ignored here.) For semiconductor-electrolyte interfaces, we have seen that two layers are involved in a series circuit configuration with corresponding capacitances of Csc and Ch (Fig. 6). Because Ch Csc, C Csc- This assumption is usually justified because Ch — 10 F cm and Csc = 1Q- — 10 F cm . If the composite resistance (/ m + R i) is 100 ohm, then tceii for metal electrodes is 10 s and that for the semiconductor case is... 

Figure 3.1. Percolation curve of a conducting composite based on nonconducting polymeric binder with conductive filler. Theoretical dependence of composite resistivity on conductive filler content. In the zone 1, the electrical resistance of the composite is similar to that of the polymer. In zone 2, the percolation fraction / represents a critical conductive filler content that permits the formation of the first conducting filament consisting of particle-to-particle contacts. In zone 3, electrical resistance of the composite is similar to that of pure conductive filler.

Resistance to creep is dependent on the alignment of fibres to match the external loading and minimise stresses in the matrix. When subjected to tensile stresses carbon composites resist long term creep very well. In off axis situations creep rates will be higher and in compression the contribution by the matrix to local fibre stability is critical and lower allowable stresses are required. 

Synergism between the conductive networks was examined, and the effects of fiber orientation and fiber length on composite resistance were evaluated. The resistance of the composites containing both carbon fiber and carbon black fillers was also compared with that of composites containing only carbon black or carbon fibers. 

Conductometric PPy-PVA composite Resistance increases with NH3 concentration but becomes irreversible beyond 10% NH,... 

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