Alicyclic methacrylate

Several polymethacrylates, primarily alkyl esters, were compared with a novolac resist in terms of etch rates in CF4 and Ar plasmas. The alkyl groups examined included methyl, terf-butyl, cyclohexyl, norbonyl, adamantyl, and benzyl [226]. The polymerization of alicyclic methacrylates was pioneered by Otsu, who has demonstrated facile polymerization of bulky methacrylates and reported high Tg of this class of polymethacrylates [230]. It has been found that alicyclic polymers exhibit better dry etch resistance than acyclic esters and that the dry etch durability is increased by an increase in the number of rings. Thus, poly(adamantyl methacrylate) is as stable as a novolac resist under dry etch conditions. A 30/70 copolymer of adamantyl methacrylate with ter/-butyl... 

A significant number of works are concerned with the development of new membranes for the separation of mixtures of aromatic/alicyclic hydrocarbons [10,11,77-109]. For example, the following works can be mentioned. A mixture of cellulose ester and polyphosphonate ester (50 wt%) was used for benzene/cyclohexane separation [113]. High values of the separation factor and flux were achieved (up to 2 kg/m h). In order to achieve better fluxes and separation factors the attention was shifted to the modification of polymers by grafting technique. Grafted membranes were made of polyvinylidene fluoride with 4-vinyl pyridine or acrylic acid by irradiation [83]. 2-Hydroxy-3-(diethyl-amino) propyl methacrylate-styrene copolymer membranes with cyanuric chloride were prepared, which exhibited a superior separation factor /3p= 190 for a feed aromatic component concentration of 20 wt%. Graft copolymer membranes based on 2-hydroxyethyl methylacrylate-methylacrylate with thickness 10 pm were prepared [85]. The membranes yielded a flux of 0.7 kg/m h (for feed with 50 wt% of benzene) and excellent selectivity. Benzene concentration in permeate was about 100 wt%. A membrane based on polyvinyl alcohol and polyallyl amine was prepared [87]. For a feed containing 10 wt% of benzene the blend membrane yielded a flux of 1-3 kg/m h and a separation factor of 62. 

Simultaneous photopolymerization of an alicyclic epoxy compound and methyl methacrylate by a sensitized sulfonium salt was described by Mitsubishi Rayon [143] in 1989. The composition finds use for dental protheses. A similar composition, patented by the same company [144], containing an inorganic filler, gives dental plates with high gloss and abrasion resistance. 

Polymers for use in 193 nm lithography are co-, ter-, and tetra-polymers of 1) methacrylates, 2) norbornenes, 3) norbornene-maleic anhydride, 4) nor-bornene-sulfur dioxide, and 5) vinyl ether-maleic anhydride (Fig. 39). While 1), 3), 4), and 5) are prepared by radical polymerization, all-norbornene polymers 2) are synthesized by transition-metal-mediated addition polymerization [166-168].Norbornenes (Fig.40) are sluggish to undergo radical [168,169] and cationic [170] polymerizations. Their ring-opening metathesis polymerization (ROMP, Fig. 40) [ 171 ] has never produced worthy resist polymers. The C=C double bonds introduced in the ROMP polymer backbone must be hydrogenated to reduce the 193 nm absorption and the ROMP polymers tend to have low Tg. However, the major problem for the ROMP polymers was their unacceptable swelling in aqueous base development. While polymethacrylate systems contain etch-resistant alicyclic structures in the ester side chain, norbornene-based systems carry the alicyclic unit in the backbone. Essentially all the 193 nm re-... 

Figure 11.49 Effect of electron-beam curing of resists based on poly(methacrylate) platform and hybrid methacrylate/alicyclic polymer platform on polygate etch. Electron-beam curing improves etch resistance by up to 50% relative to the control (uncured) sample. Processing was done in a nitrogen environment of the ElectronCure Electron Beam Process Chamber utilizing these electron-beam parameters 3.75 keV, 6 mA, 2000 pC/cm. The wafer temperature of the standard (Std.) process was not controlled, that for the electron-beam standard cure (ESC) process was kept at a medium temperature, that for the low-temperature (LT) process was maintained at a iow temperature, whiie that for the control was at room temperature. [After R. Dammel, Practical resist processing, SPIE Short Course No. SC616 (2005).]...

Random co- and terpolymers containing acrylate or methacrylate moieties with pendant alicyclic groups... 

The etch resistance of common acrylic polymers is poor but can be improved without reducing 193-nm optical transparency by the attachment of alicyclic pendant groups to the backbone. For example, a 1 1 copolymer of tert-butyl methacrylate and adamantyl methacrylate (108) exhibits a nearly twofold reduction in plasma etch rate compared to the ert-butyl methacrylate homopolymer. Figure 15b provides examples of alicyclic ester groups that have been assessed (109-111). 

An ester is a compound whose structure may be derived by the replacement of the replaceable hydrogen of an acid by an alkyl, aryl, alicyclic or heterocyclic group. The most important esters are these derived from carboxylic acids the structural formula of these esters is R-CO—O—R For the purposes of this chapter, polyesters are defined as polymers containing recurring —CO—0— groups in the main chain. It may be noted that this definition excludes polymers of esters such as vinyl acetate and methyl methacrylate since in these polymers the ester groups occur in side-chains and not in the main chain. 

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