Dissolution inhibition effect

A cresol novolac resin has been synthesized which exhibits a much greater dissolution-inhibiting effect than in various commercially available novolac or phenolic resins. Using this resin, a positive electron beam resist was prepared and its exposure characteristics were examined. A tetramethylammonium hydroxide aqueous solution was used as the developer. The sensitivity reaches 3xl0 6 C/cm2 without post-exposure baking. It was found that the sensitivity to double exposure was much higher than that to single exposure with the same total dose. A similar phenomenon was also... 

Similar dissolution inhibition effect by photoacid generators has also been observed in poly(norbomene-methyle-nehexafluoroisopropanol) (poly(NBHFA)) system [38]. Table 57.13 lists dissolution rates of poly(NBHFA) in 0.26N TMAH at room temperature with various photoacid... 

Key performance parameters of photoacid generators are absorbance, quantum efficiency, dissolution inhibition effect, etc. Table 57.14 shows quantum yields for the photolysis of some aryl iodonium and sulfonium salts. 

Formation of the resist pattern is due to the solubility change of the exposed part of the resist which results from the photochemical reaction of NQD. Figure 3 shows a change of the dissolution rate of the resist. The dissolutjon rate of a novolak film itself in an alkaline developer is approximately lOOA/sec. Once NQD is added to the novolak resin, the rate decreases drastically by the order of one thousand, which means the unexposed part scarcely dissolves in the alkaline developer. This is called the "dissolution inhibition effect" of NQD (1). And then upon exposure NQD decomposes to produce indenecarboxylic acid which makes the exposed region even more soluble than the novolak itself. 

Base catalyzed reaction As for the base catalyzed reaction, two out of the four major products were isolated as shown in Table 2. Figure 11 shows the probable reaction scheme. Unlike photochemical or thermal reactions, base catalyzed reaction seems to lake place upon the nucleophilic attack of hydroxy or phenoxy anions to the diazo group. It should be reminded that BC-F3 also implies a crosslinking structure. On the real resist surface NQD would crosslink with novolak resin as shown in Figure 12. This reaction is regarded as one of the mechanisms of the dissolution inhibition effect. 

Latitude Enhancement NOvel Single layer lithography (LENOS) is another approach for profile improvement (see Figure 15) (11). In this process the insoluble layer is formed by the alkaline treatment. The mechanism is thought to be similar to that of the dissolution inhibition effect that is, base catalyzed crosslinking and extraction of novolak resin to form the protective layer. 

The dissolution of copper and of brasses in acid solutions has been studied by several authors". Various substances have inhibiting effects on the rate of attack of copper or brasses in nitric acid" and in hydrochloric acid". ... 

While "conventional positive photoresists" are sensitive, high-resolution materials, they are essentially opaque to radiation below 300 nm. This has led researchers to examine alternate chemistry for deep-UV applications. Examples of deep-UV sensitive dissolution inhibitors include aliphatic diazoketones (61-64) and nitrobenzyl esters (65). Certain onium salts have also recently been shown to be effective inhibitors for phenolic resins (66). A novel e-beam sensitive dissolution inhibition resist was designed by Bowden, et al a (67) based on the use of a novolac resin with a poly(olefin sulfone) dissolution inhibitor. The aqueous, base-soluble novolac is rendered less soluble via addition of -10 wt % poly(2-methyl pentene-1 sulfone)(PMPS). Irradiation causes main chain scission of PMPS followed by depolymerization to volatile monomers (68). The dissolution inhibitor is thus effectively "vaporized", restoring solubility in aqueous base to the irradiated portions of the resist. Alternate resist systems based on this chemistry have also been reported (69,70). 

Mg2+ influences calcite dissolution rates the same way, but not to the same extent as Ca2+. The inhibition effects of Mg2+ can be described in terms of a Langmuir adsorption isotherm. Sjoberg (1978) found he could model results for the combined influences of Ca2+ and Mg2+ in terms of site competition consistent with ion exchange equilibrium. The inhibition effects of Mg2+ in calcite powder runs increase with increasing Mg2+ concentration and as equilibrium is approached. 

Studies of phosphate inhibition of calcite dissolution both in the presence and absence of Ca2+ and Mg2+ have shown that the inhibiting effect of phosphate increases with increasing Ca2+ concentration. Results in solutions with Mg2+ were less reproducible, indicating the same trend, but not as strong an inhibition relation (Sjoberg, 1978), and a decrease in apparent equilibrium with increasing phosphate,... 

Nestaas, I., and Terjesen, S.G. The inhibiting effect of scandium ions upon the dissolution of calcium carbonate. 

Knowledge that silyl substituents may be incorporated into standard resist chemistry to effect etching resistance has prompted several workers to evaluate silylated novolacs as matrix resins for conventional positive-photoresist formulations. Typically, these resists operate via a dissolution inhibition mechanism whereby the matrix material is rendered insoluble in aqueous base through addition of a diazonaphthoquinone. Irradiation of the composite induces a Wolff rearrangement to yield an indenecarboxylic acid (Figure 4), which allows dissolution of the exposed areas in an aqueous-base developer (35). 

Figure 1. CO2 partial pressure control on carbonate dissolution A) effect of temperature on biogenic soil pCOz and total soil pCOz, soil pC-Oi is lower than biogenic pCOi due to inhibition effects of high CO2 or low oxygen levels (Drake, 1983) and, B) equilibrium concentrations of Ca with respect to calcite for open, closed, and restricted air volume systems Equilibrium pCOi values below atmospheric equilibrium is...

To exemplify inhibition effects, we choose a few case studies with Fe(III)(hydr)oxides because these oxides are readily dissolved with protons, ligands, and reductants and are of great importance in the iron cycles in natural waters. The reductive dissolution of Fe(III) minerals by a reductant such as H2S is much faster than ligand- or proton-promoted dissolution. The dissolution reaction, as shown by Dos Santos-Afonso and Stumm (1992), is initiated by the formation of =FeS and =FeSH surface complexes the subsequent electron transfer within the complex leads to the formation of Fe(II) centers in the... 

The fact that oxoanions can effectively inhibit reductive and nonreductive dissolution with regard to a reference system supports and the concept of competition between dissolution-promoting and dissolution-inhibiting ligands. As Figure 13.20 shows with the help of MICROQL calculations (Westall, 1979 based on complex formation constants fitted to actual data by Sigg and Stumm, 1981, on one hand and by Dos Santos-Afonso and Stumm, 1992, on the other hand), the dissolution system is very sensitive to phosphate. 

An alternative, or complementary mechanism could have been that low levels of fluoride from the more-rapidly dissolving dentine caused the effect, inhibiting enamel dissolution more effectively than that of dentine itself, as reported by ten Cate et al. [11]. Although fluoride concentrations measured in... 

Among the experimental findings were the inhibiting effect of the polymer, the yield restriction in the course of the reaction, and the decelerating effect of salts dissociating during dissolution. These results can be explained by the displacement of equilibrium toward the formation of mixed ion pairs. 

Several investigators have studied inhibition of calcite dissolution near equilibrium pH by surface adsorption of insoluble salts. Berner and Morse ( 7) showed inhibition by phosphate at 10 6 M. Terjesen et al (1A) modeled the inhibiting effects of metal ions as an apparent reduction in the equilibrium pH. Koss and Moller (15) studied the apparent equilibrium pH in the presence of Ni, Fe, Mg, and other metal ions. Sjoberg (13) measured inhibition by phosphate and by Mg++. 

PHEMA into an SBF solution. At the higher released citric acid concentrations, the formation of calcium citrate crystals can bring about a depletion of the calcium ion concentration in the SBF solution, so less calcium phosphate will precipitate onto the polymer. At lower citric acid concentrations, the inhibition effect of citrate anions on formation of calcium phosphates has been attributed to the complex equilibria between calcium, citrate and phosphate ions (27-29). Precipitated calcium phosphates may undergo dissolution via surface exchange between phosphate and citrate ions (calcium citrate is much more soluble than calcium phosphate). 

Fluang [246] investigated the SCC of AISI 321 stainless steel in acidic chloride solutions by the SSRT technique and fracture mechanics. It was found that the cleavage fracture characterizes the fracture surface. The active dissolution mechanism controls the SCC of AISI 321 stainless steel in acidic chloride solutions and can be inhibited by using KI. The inhibition effect of KI on the SCC is due to inhibition of the anodic reaction of the corrosion process. 

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