Dissolution rate resist

Have alloying elements that, once the oxide film was broken down or penetrated, would have a slow dissolution rate, resist noncongruent dissolution that is detrimental, and collect beneficial alloying elements at easy low coordination dissolution sites. The alloying element might also be engineered to alter surface diffusion rates. 

Positive-Tone Photoresists based on Dissolution Inhibition by Diazonaphthoquinones. The intrinsic limitations of bis-azide—cycHzed mbber resist systems led the semiconductor industry to shift to a class of imaging materials based on diazonaphthoquinone (DNQ) photosensitizers. Both the chemistry and the imaging mechanism of these resists (Fig. 10) differ in fundamental ways from those described thus far (23). The DNQ acts as a dissolution inhibitor for the matrix resin, a low molecular weight condensation product of formaldehyde and cresol isomers known as novolac (24). The phenoHc stmcture renders the novolac polymer weakly acidic, and readily soluble in aqueous alkaline solutions. In admixture with an appropriate DNQ the polymer s dissolution rate is sharply decreased. Photolysis causes the DNQ to undergo a multistep reaction sequence, ultimately forming a base-soluble carboxyHc acid which does not inhibit film dissolution. Immersion of a pattemwise-exposed film of the resist in an aqueous solution of hydroxide ion leads to rapid dissolution of the exposed areas and only very slow dissolution of unexposed regions. In contrast with crosslinking resists, the film solubiHty is controUed by chemical and polarity differences rather than molecular size. 

Numerous studies have probed how novolac microstmcture influences resist hthographic properties. In one example, a series of resists were formulated from novolacs prepared with varying feed ratios ofpara-jmeta-cmso. These researchers found that the dissolution rate decreased, and the resist contrast increased, as thepara-jmeta-cmso feed ratio increased (33). Condensation can only occur at the ortho position ofpara-cmso but can occur at both the ortho- and i ra-positions of meta-cmso. It is beheved that increased steric factors and chain rigidity that accompany increasedpara-cmso content modify the polymer solubihty. 

The local dissolution rate, passivation rate, film thickness and mechanical properties of the oxide are obviously important factors when crack initiation is generated by localised plastic deformation. Film-induced cleavage may or may not be an important contributor to the growth of the crack but the nature of the passive film is certain to be of some importance. The increased corrosion resistance of the passive films formed on ferritic stainless steels caused by increasing the chromium content in the alloy arises because there is an increased enhancement of chromium in the film and the... 

Sintered and sprayed ceramic anodes have been developed for cathodic protection applications. The ceramic anodes are composed of a group of materials classified as ferrites with iron oxide as the principal component. The electrochemical properties of divalent metal oxide ferrites in the composition range 0- lA/O-0-9Fe2O3 where M represents a divalent metal, e.g. Mg, Zn, Mn, Co or Ni, have been examined by Wakabayashi and Akoi" . They found that nickel ferrite exhibited the lowest consumption rate in 3% NaCl (of 1 56 g A y at 500 Am and that an increase in the NiO content to 40mol 7o, i.e. O NiO-O-bFejO, reduced the dissolution rate to 0-4gA y at the expense of an increase in the material resistivity from 0-02 to 0-3 ohm cm. 

In plain tinplate cans for acid foods, tin provides cathodic protection to steel (3,4). The slow dissolution of tin prevents steel corrosion. Many investigators (5-1I) have defined this mechanism in detail and have shown that the tin dissolution rate is a function of the cathodic activity of the base steel, the steel area exposed through the tin and the tin-iron alloy layers, and the stannous ion concentration. Kamm et al. showed that control of the growth of the tin—iron alloy layer provides a nearly continuous tin-iron alloy layer and improves the corrosion resistance of heavily coated (over 45 X 10"6 in. tin) ETP for mildly acid food products in which tin provides cathodic protection to steel (12). The controlled tin-iron alloy layer reduces the area of steel exposed to the product. ETP with the controlled alloy is designated type K, and since 1964, 75 type K ETP has been used to provide the same protection as 100 ETP provided previously (13). 

The best known way of lowering the corrosion of iron is by its alloying with chrominm, nickel, and other metals. The corrosion resistance of the corresponding stainless steels is dne to the fact that chrominm is readily passivated. This is a quality that is fonnd even in alloys with relatively low chromium contents. Hence, stainless steels are practically always strongly passivated, and their spontaneous dissolution rates are very low. 

Acid Concentration Required for Crosslinking Resist Films. The strong acid catalyzed reaction of methylated melamine 1 with novolak in a film was studied first in order to estimate the amount of acid generated in experimental AHR resists upon exposure. Incremental amounts of a 1% solution of p-toluenesulfonic acid (pTSA) were added to a resist solution which contained no RSAG. The solutions were coated onto wafers and subjected to a typical bake cycle. The dissolution rate... 

Figure 8 shows the effect of the alkaline concentration in TMAH solutions on the contrast and sensitivity of the new resist. Sensitivity of the resist increases as the alkaline concentration increases, however, the contrast is maxima (4.72) at 0.83% TMAH solution. This means that the higher concentration over 0.83% cannot distinguish the difference of the dissolution rate between the unexposed and exposed resist film. For instance, the higher concentrated developer also attacks the exposed areas and the loss of resist thickness occurs. The alkaline concentration in TMAH solution, therefore, is optimized at 0.83%. This developer concentration was subjected to the following lithographic evaluation. 

Cation Size. In their early studies, Hlnsberg (1) and Arcus (3) found that dissolution rates of resists decreased as the size of the cation of the base Increased. Our results support their conclusion. In Figure 5, the dissolution rates of a PMPS(10X)/p-N02-PHMP film 1n different alkali solutions clearly show a decreasing trend with increasing cation size. In fact, the rate 1s Inversely proportional to the cross-sectional area of the unhydrated cation (Figure 6). It is known 1n the diffusion of small molecules 1n polymers, the diffusion constant is Inversely related to the size of the molecule (IS). The observed dependence of dissolution rate on cation size 1s therefore suggestive of cation diffusion as a crucial step. It is... 

In some Sub-Saharan African countries, a WHO study (WHO, 2003) shows a high failure rate in quality control testing on chloroquine tablets. Only 58% of the medicines tested had an acceptable levels of chloroquine content and only 25% had the correct dissolution rate (which is an indicator of the fact that the active substance is dissolved in the intestine and therefore can be absorbed by the body) (Figure 3). Treating patients with poor quality medicines may result in providing insufficient dosages, so promoting the development of resistance. 

The BA is relatively well crystallized, which tends to lower hydrolysis when considering a long-term perspective. Dissolution rates are generally lowered if the crystalline fraction is higher and the growth of less resistant phases like meli-lites can be reduced. This is mainly the case for bulk compositions with a higher Si/Ca ratio. 

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.

Y-intercept and the slope, respectively, and are listed in Table I. The results of the dissolution rate determination method (method 2) are presented in Figure 3. As can be seen, the maximum removable mineral (P0) by dilute acid is independent of the size of the shale particles. However, the carbonate fraction in the shale mineral matrix is very close to this figure. This could mean that the accessibility of the leaching agent to the leachable materials in shale is complete in the size ranges studied in this experiment—but at different rates. This could also indicate that the carbonate deposit sites are not isolated but can, perhaps, be thought of as interconnected by minerals built of the dilute acid-resistant minerals. 

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