Lithographic evaluation and processing of chlorinated polymethylstyrene

Hartney, Mark A.; Tarascon, R. G.; Novembre, Anthony E.

doi:10.1116/1.583264

Cited by 23 publications

(13 citation statements)

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“…G= -0.414G~ = 0.399/D~ ~ 9 Mw [4] G= -0.250Gs = 0.241/Dn ~ " Mw [5] The data points are plotted in accordance with these equations in Fig. 6 and 7, respectively.…”

Section: Discussionmentioning

confidence: 92%

Radiation‐Induced Cross‐linking and Chain Scission Reactions in Chlorinated Polymethylstyrene Electron‐Beam Resists

Jones

Matsubayashi

Tate

et al. 1990

J. Electrochem. Soc.

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Structurally characterized polymers of o-, m-, and p-methylstyrene, 2,4-and 2,5-dimethylstyrene, and 2, 4, 6-trimethylstyrene prepared by anionic mechanisms and chlorinated selectively at substituent methyl positions, have been assessed as negative-working electron-beam resists. Copo]ymers of vinyl benzyl chloride and o-, m-, and p-methylstyrene prepared by a radical mechanism are similarly assessed. The lithographic data have been correlated in accordance with Inokuti's theory for the radiation-induced simultaneous cross-linking and scission of polymers with generalized Poisson distributions. All the polymers substantially substituted with methyl groups in the ortho position are shown not to undergo radiation-induced chain scission and accordingly display the highest lithographic contrasts. Lithographic reactivities and the radiation chemical yields are further correlated in accordance with the Charlesby-Pinner relationship and are shown to be independent of both molecular weight and polydispersity and therefore characteristic of chain microstructure. Lithographic contrast is shown to arise from variations in gel dose.The application of chlorinated polymethylstyrene derivatives as negative-working electron beam resists has been investigated extensively in recent years. As a class, they offer submicron resolution and display a moderate to high sensitivity to radiation and good dry-etch durability.In order to optimize lithographic performance, a wide range of structures has been accessed through a variety of synthetic approaches:1. Imamura et al.(1, 2) employed Lewis acid catalyzed chloromethylation of polystyrene (CMS) synthesized by anionic methods. This has the advantage of being able to start with a polymer of narrow molecular weight distribution, but the product polymers are structurally ill-defined, and although a range of chlorine contents can be attained, the phenyl rings bear no unchlorinated methyl groups.2. Tarascon and Hartney et al. (3, 4) carried out homogeneous solution-phase free radical-induced partial chlorinations of poly(p-metl~ylstyrene). This allows the ready preparation of narrow distribution polymers through the anionic polymerization of the parent monomer but results in main chain chlorination and di-and tri-as well as monochlorination of the methyl groups. More recently, Jones and Matsubayashi (5) have achieved essentially selective monochlorination of the ring substituent methyl groups of the polymer using sodium hypochlorite and a phase transfer catalyst (PTC). Some broadening of the molecular weight distribution was found to be inevitable and this feature limited the extent of chlorination that could realistically be achieved.3. Ledwith et al. (6) developed copolymers of vinyl benzyl chloride (VBC; a 60:40 mixture of the m-and p-isomers) and p-methylstyrene, which, though offering a degree of substituent positional specificity and completely avoiding the possibility of main chain chlorination over a wide range of chlorine contents, confines the molecular weights of the polymers and the...

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“…G= -0.414G~ = 0.399/D~ ~ 9 Mw [4] G= -0.250Gs = 0.241/Dn ~ " Mw [5] The data points are plotted in accordance with these equations in Fig. 6 and 7, respectively.…”

Section: Discussionmentioning

confidence: 92%

Radiation‐Induced Cross‐linking and Chain Scission Reactions in Chlorinated Polymethylstyrene Electron‐Beam Resists

Jones

Matsubayashi

Tate

et al. 1990

J. Electrochem. Soc.

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“…There have been several reports of halogenation of poly(4-MeSt) to introduce chloromethyl-or bromomethyl groups on to the rings. [19][20][21] Bromination reactions are, compared to chlorination reactions, highly selective toward formation of the monobromination of the methyl groups. Chung, et al reported the radical bromination of α-olefin/4-MeSt copolymers.…”

Section: Resultsmentioning

confidence: 99%

Preparation of branched polystyrene using atom transfer radical polymerization techniques and protection-deprotection chemistry

Kwark

2008

Macromol. Res.

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A new strategy using protection-deprotection chemistry was used to prepare branched polymers using the ATRP method only. Among the several monomers with different protecting groups, vinyl benzyl t-butyloxy carbonate (VBt-BOC) and 4-methyl styrene (4-MeSt) could be polymerized successfully to form backbones using the ATRP method in a controlled fashion. The protected groups in the backbones were converted to alkyl bromides and used as initiating sites for branch formation. The benzyl t-butyloxy carbonate groups in the backbones containing VBt-BOC units were first deprotected to benzyl alcohol by trifluoroacetic acid, then converted to benzyl bromide by reacting them with triphenylphosphine/carbon tetrabromide. The benzyl bromide groups in the backbones containing 4-MeSt units could be generated by bromination of the methyl groups using N-bromosuccinimide/benzoyl peroxide. The structures of the prepared polymers were well-controlled, as evidenced by the controlled molecular weight as well as the narrow and unimodal molecular weight distribution.

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“…this correction is that the apparent gel dose of the copolymer dg/d log 10 r=2.303 K ar e−ar (7) resists is marginally suppressed, an effect that can be attributed to the irregular distribution of crosslinking points along the By substituting r=R0.5, it follows that contrast is given by eqn. (8). polymer chain that results from a statistical copolymerisation process.…”

Section: Discussionmentioning

confidence: 99%

Radiation chemistry and the lithographic performance of chemical amplification resists formulated from poly(4-epoxystyrene-stat-styrene) and a photoacid generator

Jones¹,

Cordina²,

Murphy³

1997

J. Mater. Chem.

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Copolymers of styrene and 4-epoxystyrene in formulations with triphenylsulfonium hexafluoroantimonate as a photoacid generator undergo a crosslinking reaction by a chain mechanism when irradiated with 20 keV electrons and hence act as negativeworking electron-beam resists. The copolymers have been prepared by a free radical mechanism over the entire composition range and the lithographic performance of the materials has been evaluated. The sensitivities of the resist formulations are shown to correlate with the epoxystyrene content of the copolymers in accordance with a simple model of the radiation chemistry of the system. Contrast variations are explained in terms of the statistical structure of the copolymer and it is demonstrated that at low epoxystyrene contents the systems behave in accordance with an unsensitised single-stage crosslinking mechanism. The copolymers with epoxystyrene contents greater than ca. 8% have such high lithographic sensitivities and show such a good tolerance of processing variations as to commend the optimisation of their performance with a view to their subsequent application as electron-beam resists.

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Lithographic evaluation and processing of chlorinated polymethylstyrene

Cited by 23 publications

References 0 publications

Radiation‐Induced Cross‐linking and Chain Scission Reactions in Chlorinated Polymethylstyrene Electron‐Beam Resists

Radiation‐Induced Cross‐linking and Chain Scission Reactions in Chlorinated Polymethylstyrene Electron‐Beam Resists

Preparation of branched polystyrene using atom transfer radical polymerization techniques and protection-deprotection chemistry

Radiation chemistry and the lithographic performance of chemical amplification resists formulated from poly(4-epoxystyrene-stat-styrene) and a photoacid generator

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