Polymeric dissolution inhibitor

When two polymeric systems are mixed together in a solvent and are spin-coated onto a substrate, phase separation sometimes occurs, as described for the application of poly (2-methyl-1-pentene sulfone) as a dissolution inhibitor for a Novolak resin (4). There are two ways to improve the compatibility of polymer mixtures in addition to using a proper solvent modification of one or both components. The miscibility of poly(olefin sulfones) with Novolak resins is reported to be marginal. To improve miscibility, Fahrenholtz and Kwei prepared several alkyl-substituted phenol-formaldehyde Novolak resins (including 2-n-propylphenol, 2-r-butylphenol, 2-sec-butylphenol, and 2-phenylphenol). They discussed the compatibility in terms of increased specific interactions such as formation of hydrogen bonds between unlike polymers and decreased specific interactions by a bulky substituent, and also in terms of "polarity matches" (18). In these studies, 2-ethoxyethyl acetate was used as a solvent (4,18). Formation of charge transfer complexes between the Novolak resins and the poly (olefin sulfones) is also reported (6). 

These results indicate that vacuum curing occurs through a radical reaction mechanism and is terminated by reaction of the ring-opened epoxy group with the azide group (not nitrene) under exposure. There is a possibility that polymerization initiated by an exposure-induced radical cation may occur. Furthermore, it is thought that reaction products from both the azide and epoxide serve as dissolution inhibitors, because the sensitivity of EAP is almost the same as that of EP, as shown in Figures 1 and 2. 

Figure 23 lists representative acid-labile protecting groups that have been incorporated in positive-tone CA resist systems. These groups can be pendent to the matrix polymer chain, can be attached to a monomeric or polymeric additive that acts as a dissolution inhibitor (64—66), or can even be appended to the PAG structure (67). The kinetics of acid-catalyzed deprotection vary significantly with structure. In particular, the activation energy,... 

However, the photochemistry itself does not make a relief image. Rather it is used to modify the solubility of the polymeric binder. The diazoquinone compounds used in resists are referred to as dissolution inhibitors or photoactive components (PAC s). The addition of a diazoquinone molecule dramatically inhibits the dissolution rate of a thin film of a novolac resin. Upon exposure, the dissolution rate of the novolac based resist is considerably faster than the rate for the novolac alone. The accelerated dissolution rate may be caused by formation of acid eind its subsequent ionization during development or by enhauiced diffusion of the developer into the coating because of changes caused by the formation and fate of the nitrogen (2). 

Novolac Based Positive Electron Beam Resist Containing a Polymeric Dissolution Inhibitor... 

Bowden and his coworkers(j).) proposed a new type of positive electron beam resist which consists of an alkali-soluble novolac and polymeric dissolution inhibitor. The positive working mechanism of this new type positive resist( NPR ) is similar to that for the conventional positive photoresist 10). It was also found that poly(2-methylpentene-l sulfone)( PMPS ) is good as a polymeric dissolution inhibitor for NPR(lil). In addition, it was clarified that one of the difficulties with NPR is phase separation in the resist films(10)(n). 

Although it is generally difficult to find polymer pairs that mix homogeneously, PHOST partially protected with THP or tert-butoxycarbonylmethyl group has been reported to be miscible with a novolac resin or PHOST and to function as a dissolution inhibitor [124,132]. Another acid-labile polymeric dissolution inhibitor is a terpolymer of tert-butyl methacrylate (TBMA), methyl methacrylate (MMA), and methacrylic acid (MAA), which is miscible with a novolac resin [179] while PTBMA is not [159]. This methacrylic terpolymer is only marginally miscible with PHOST but more compatible with C- and... 

In addition to the oligomeric and polymeric dissolution inhibitors discussed earlier, small molecules bearing acid labile groups have been employed in 157 nm resist formulations [295, 312]. Representative examples are shown in Fig. 98. Some are better than others in dissolution inhibition of a copolymer of NBHFA and NBTBE (92 8). What is interesting is that a diazonaphthoquinone PAC developed for mid UV application (Fig. 99) [313] is surprisingly transparent and can inhibit the dissolution of PNBHFA even better than the small acid-labile dissolution inhibitors in Fig. 98 [312]. In contrast, the dissolution of PSTHFA cannot be efficiently inhibited either with diazonaphthoquinone, the small acid-labile lipophilic compounds in Fig. 98, or the carbon monoxide copolymer (Fig. 94) [312]. 

H. Ito and E. Flores, Evaluation of onium salt cationic photoinitiators as novel dissolution inhibitor for novolac resin, J. Electrochem. Soc. 135,2322 (1988) H. Ito, Aqueous base developable deep UV resist systems based on novel monomeric and polymeric dissolution inhibitors, Proc. SPIE 920, 33 (1988). T. Aral, T. Sakamizu, K. Katoh, M. Hashimoto, and H. Shiraishi, A sensitive positive resist for 0.1 p,m electron beam direct writing hthography, J. Photopolym. Sci. Technol. 10, 625 (1997). 

Tamboli et al. (2009) have used OCP and galvanic current measurements to study PCMPC chemistries for Cu as well as a range of barrier metals including Ta, TaN, Ti, TiN, and Ru. A primary contaminant generated during Cu CMP is the residual species of the dissolution inhibitor BTA regularly used for metal CMP (Yamada et al., 2008 Tran et al., 2012). When present in the CMP slurry, Cu +/Cu+ can form insoluble Cu-BTA complexes, which in turn can lead to unavoidable surface defects in the form of strongly adsorbed (sometimes polymeric) islands and/or scratches on the processed Cu. Electrochemical methods have been proven to be usefiil to study the presence of these Cu-BTA defects as well as their removal chemistries under in situ conditions (Miao et al., 2014). 

The solubility of the PAG in the solid polymeric matrix can influence CA resist performance (63). This is a particular issue for the ionic oniiun salts if the polarities of polymer and PAG are sufficiently different, phase segregation will occur, and the poor mixing of photoacid and polymer effectively reduces the efficiency of catalyzed deprotection. Additionally, resist contrast can be affected when the solubility of the photoproducts differs from that of the original onium salt. In fact onium salts can serve as dissolution inhibitors in novolac polymers, analogous to diazonaphthoquinones, even in the absence of any acid-sensitive chemical function on the poljuner (27). 

COMA polymers (Fig. 17), synthesized by conventional radical polymerization, have a 1 1 alternating structure, a consequence of the preference for each radical to react exclusively with the other monomer. As a rnle, the products are high Tg materials for example poly(norbornene-co-maleic anhydride) has a Tg > 300°C. The polymerization allows the incorporation of small amoimts of other vinyl monomers (e.g. acrylic acid) without disruption of the alternating structure (117). Substituted norbornenes can be included in the pol5mierization mixture to incorporate acid-labile functionality, to modify polymer polarity, and to improve film adhesion (118). Cholate dissolution inhibitors can be added in the formulated resist to further modify functional properties (119). 

Another chemical strategy for microstructure generation is related to the dissolution inhibitor principle, whereby a polymeric matrix is rendered insoluble in a certain solvent by admixing with a particular compound. 

Radiation-induced decomposition or chemical alteration of the dissolution inhibitor restores the solubility of the polymeric matrix. For example, certain polysulfones and polyaldehydes (for general structures, see Chart 5.10) will act as dissolution inhibitors when blended with phenol formaldehyde or cresol formaldehyde resins. 

Poly(olefin sulfone) chart 5.10 Chemical structures of polymeric dissolution inhibitors for novolak resins. 

This paper presents new data on dissolution kinetics. The effects of alkali concentration, size of the cation, and salt addition were studied. The influence of segmental mobility on dissolution was elucidated by measuring the temperature coefficients of the dissolution rates. Experiments were also carried out to study the relation between the chemical structure of a polymeric Inhibitor and Its effectiveness 1n retarding dissolution. Based on these results,... 

Fronts of concentrations of 0.03, 0.06, and 0.15% (AIBN to MMA) were run at the temperatures ranges of 42 to 47,47 to 52 and 66 to 68 C. The ranges were a result of temperature fluctuations due to the type of thermostat used. Three samples at each set of conditions were run to determine an average and standard deviation. To ensure that the fronts were initiated by the polymeric seed, controls were run that did not contain seeds. To ensure that the gradient movement detected was not solely seed dissolution, controls using seeds and solutions of 4.0% TEMPO, a free-radical scavenger used as an inhibitor, in... 

The experimental controls where no seeds were included polymerized homogeneously indicating that it is necessary to include a seed for IFF to occur. Controls that included seeds and a polymeric inhibitor to illustrate seed dissolution showed an initial sharp dip that did not move up the reaction vessel but instead diffused with time indicating no reaction taking place. 

Inhibition in acidic environments is not always due to the partial blocking of the surface by an adsorbed inhibitor. Sometimes, the inhibitor forms weakly soluble complexes with the metal ions produced by dissolution. The complexes precipitate at the surface forming a porous layer. In certain cases, the unsaturated carbon-carbon bonds of the complexes undergo polymerization reactions that render the layers more compact. The dissolution of the metal is thus slowed. 

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