Cross-linking resists

The main producers of organic accelerators for mbber vulcanization are shown in Table 3. This table is not meant to be completely comprehensive, but rather to indicate the principal historical suppHers to the mbber industry. Most producers offer chemical equivalents in the largest-volume products. Within the range of smaHer-volume specialty accelerators, chemical equivalents become less common. Each producer may offer different products to achieve the same purpose of rapid cross-linking, resistance to thermal degradation, or other performance characteristics. Many offer proprietary blends of accelerators. 

Cross-linking reactions, acid-catalyzed polymer, 15 168-169 Cross-linking resists, 15 172 Cross-linking systems, covalent dye fixation using, 9 489-491 Cross-finking treatments, in volumetric sweep efficiency, 18 620 Cross-finks... 

Plasma films are usually highly cross-linked, resistant to higher temperatures, resistant to abrasion and chemical attack, and are highly adherent to the surface. Adhesion to the surface is generally high both because the growing polymer complex can fit the surface contour and thus lock-itself in (physical adhesion), and because in many instances, the species are active enough to chemically react with the surface molecules to chemically bond to the surface. The surface can be prepared so that the chemical reaction is enhanced. 

Protein-protein-AGE (cross-linked resists proteolysis inhibits proteasomes induces ROS)... 

It is apparent from Table I that the sensitivity of lightly cross-linked resist films is more dependent upon film thickness than is that of fully-cured films (i.e. films cured at 150-175°C). It seems that the solvent may have some influence upon sensitivity. The values in Table I were obtained on films spun from solution in ethoxyethyl acetate and even fully cross-linked films show some variation of sensitivity with film thickness. 

The resist has been used as a mask in wet etching and in lift-off processes, and more recently in etching chromium films in a chlorine-oxygen-helium plasma. In the latter, the etch rates have ranged from 4 to 5.5nm/min at lOOW power in a barrel type reactor. Chromium etches at about 6.5nm/min under these conditions. The etch rate of the resist appears to be independent of the degree to which it has been cured before exposure, so the sensitive form described here is just as effective a mask as the highly cross-linked resists described earlier, at least in the chromium etching process. 

The copper foil is subsequently covered with a photoresist layer that is patterned by lithography techniques to produce the desired circuitry. Areas of exposed, cross-linked resist protect the copper that is to remain on the board as circuitry. The unprotected copper that is not needed for the circuitry is etched away, usually with ferric chloride solution. At this point, the printed board must have the following characteristics the substrate has to be structurally sound (no delamination), and the copper conductor patterns have to adhere well to the substrate in addition, the assembly should have good dimensional stability, and it has to show good solderability (ability to withstand short exposures to liquid solder at temperatures around 250 C or higher) to allow for the connection of components and devices to the circuitry. 

Equation (6.4) is the fundamental equation of cross-linking resists, for it relates the imaging characteristic, namely, the gel dose Eq, to molecular properties of the polymer. It expresses the fact that the resist sensitivity is proportional to the quantum yield of the cross-linking reaction, to the weight-average molecular weight Mw of the polymer, and to the radiation-gathering power em of the chromophore. ... 

The effect of the cross-linking of resist polymer films is to make the film stable to heat such that it cannot be made to flow or melt. A fully cross-linked resist polymer film is practically insoluble in most solvents, although it can be stripped with oxygen plasma etching. Its plasma etch resistance is superior to a similar film that is not cross-linked. 

Negative-tone imaging using ultraviolet or X-ray exposure of cross-linking resists such asSU-8... 

Negative-Tone Thick-Film Lithography Using UV and X-Ray Exposure of Cross-Linking Resists... 

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