Bis(fluoroalcohol) Monomers and Polymers:  Improved Transparency Fluoropolymer Photoresists for Semiconductor Photolithography at 157 nm

Abstract

Novel norbornene and [4.2.1.02,5]tricyclononene monomers bearing two hexafluoro-2-propanol substituents are polymerized with tetrafluoroethylene in solution, giving amorphous, largely alternating copolymers. The norbornene copolymer shows excellent transparency at 157 nm and a dissolution rate in aqueous tetramethylammonium hydroxide that is 100 000 times faster than the corresponding polymer with a single hexafluoro-2-propanol substituent on the norbornene ring. Intermediate dissolution rates are readily obtained using mixtures of the mono- and disubstituted norbornenes. The tricyclononene copolymer is obtained in higher conversion and molecular weight but has a higher absorbance at 157 nm and a slower dissolution rate. Partial protection of the fluoroalcohol groups as their methoxymethyl derivatives gives photoresist polymers with absorbance of 1.0 μm-1 or less which can be imaged at 157 nm using a photoacid generator.

New Amorphous Fluoropolymers of Tetrafluoroethylene with Fluorinated and Non-Fluorinated Tricyclononenes. Semiconductor Photoresists for Imaging at 157 and 193 nm

“…As described elsewhere, the use of HFPO-dp leads to a 0.2-0.3 µm -1 improvement in 157 nm transparency because the latter initiator does not leave carbonyl-containing end groups on the polymer chains. 11 Polymer compositions were generally determined by 19 F NMR. For polymers 21 and 23, which lack fluorine signals from the TCN component, 13 C NMR spectra were obtained for complete compositional analysis using the carbonyl signal to quantify the TCN ester.…”

“…9,10 We have recently described copolymers of TFE and a norbornene substituted by two hexafluoro-2-propanol substituents which show exceptional transparency. 11 Photolithography at 157 nm has now largely disappeared from the semiconductor road map due to the development of 193 immersion lithography as a less expensive alternative for generating features at the 65 nm and smaller nodes. We, therefore, retooled our effort toward development of fluorinated photoresists for 193 imaging.…”

Immersion Lithography: Photomask and Wafer-Level Materials

“…Ideally, the topcoat would dissolve in the same aqueous base developer (TMAH) used in the resist development step, but some topcoat versions were designed for nonaqueous solvent development, which adds an extra processing step. Many topcoats incorporate fluorinecontaining functional groups for their increased hydrophobicity, as well as the same compound 112 French · Tran types used effectively for absorbance reduction in 157-nm technology (88,(96)(97)(98)(99)(100)(101). These fluoropolymers have also been used in water immersion resist materials-either as additives to current 193-nm materials or as block copolymers (102)(103)(104).…”

The “Precursor Approach” to Patterned Fluorescence Images in Polymer Films

“…In the past few years, the 157 nm fluorine excimer laser has been applied to the generation of relief images with extremely narrow line widths and spacing. [64][65][66][67] Thus, systems for efficient generation of catalytic amounts of acids from PAG upon irradiation of a 157 nm excimer laser are required. Recently, Scaiano and coworkers have developed a protocol for the verification of acid generation in 157 nm lithographic processes based on patterned fluorescence images associated with the coumarin derivative 26 (coumarin 6) (Scheme 12).…”