Novel Fluoropolymers for Use in 157nm Lithography.

Abstract

Unexpectedly good UV transmittance at 157 nm of poly(norbornene sulfone) bearing a pendant hexafluoroisopropanol functionality has prompted us to employ this fluoroalcohol as an acid group for the design of chemical amplification resists for use in 157 nm lithography. The backbone structures to which the hexafluoroalcohol group is attached are polynorbornene and polystyrene. Furthermore, our discovery that poly(methyl a-trifluoromethylacrylate) is adequately transparent at 157 nm has led us to incorporate the a-trifluoromethylacrylic unit in the polymer backbone by radical copolymerization with styrenes and norbomenes. Thus, four platforms are currently available to us in preparation of 157 nm resist polymers; 1) all-acrylic, 2) all-norbornene, 3) acrylic-norbomene, and 4) acrylic-styrenic systems.

DFT Calculations of Photoabsorption Spectra in the VUV Region for Design of Photoresist Materials for 157 nm Lithography.

“…Although the a-trifluorination of PMMA significantly decreases the absorption at 157 nm as reported by Brodsky et al [7] and Ito et al [18,19], the calculated absorptions of (c) and (d) are only 20-30 % smaller than those of (a) and (b). For estimating absorbance in the solid state, calculated oscillator strengths should be divided by molecular volume.…”

“…Figs. 2, 4, and 11 demonstrate the effectiveness of the judicious introduction of -CF3 group and support the good transparency of poly(MTFMA) at 157 nm [18,19]. Fig.12 shows the calculated spectra of the esters of propionic acid (a-d) and 3,3,3-trifluoropropionic acid (e-h).…”

Dissolution Characteristics of Acidic Groups for 157-nm Resist.

“…The HFA group can be attached to styrene (St) and norbornene (Nb). 4- (1,1,1,3 [1]. We found that vinyl sulfonyl groups exhibited extremely high transparency at 157 nm and reported that copolymers with HFASt worked as resists [9,10].…”

“…Thus, fluoropolymers have been intensively studied because of their high transparency at 157 nm [1][2][3][4][5][6]. In addition to good transparency, the most important property for high-resolution capability is good dissolution characteristics [7].…”

Synthesis and Properties of Fluorine-containing Poly(ether)s with Pendant Hydroxyl Groups by the Polyaddition of Bis(oxetane)s and Bisphenol AF

“…Recently, most research groups investigated fluoropolymers as photoresist materials for F 2 lithography because they are fairly transparent in the vacuum ultraviolet (VUV). [1][2][3][4][5][6] In our recent paper, we demonstrated the synthesis and characterization of fluorine-containing polymers by the polyaddition of fluorine-containing bis(epoxide)s with fluorine-containing dicarboxylic acids, diols, 7 and active diesters. 8 The refractive indices of the obtained polymers decreased when the fluorine contents increased.…”