Hidekazu Okamoto

19F nuclear magnetic resonance studies of halogenated propanes

Abstract The relationship between 19 F chemical shifts in halogenated propanes and their structures are elucidated using MNDO calculations to determine the population of rotamers. The pairs of atoms gauche to a fluorine atom and van der Waals interaction between the two terminal substituents are responsible for the 19 F chemical shifts. The differences among chemical shifts in diastereomers are also discussed in terms of the conformation of the molecule.

A New Route to Perfluoro(Propyl Vinyl Ether) Monomer: Synthesis of Perfluoro(2-propoxypropionyl) Fluoride from Non-Fluorinated Compounds

Perfluoro(2-propoxypropionyl) fluoride (1a), which is the precursor of the perfluorinated propyl vinyl ether (PPVE) monomer of an industrially important perfluoroalkoxy copolymer (PFA), was synthesized by utilizing direct fluorination of the non-fluorinated counterpart for the first time. The partially-fluorinated ester 7 synthesized from the desired perfluorinated acid fluoride 1a itself and the non-fluorinated alcohol 5, which has a carbon skeleton corresponding to the desired compound 1a, was perfluorinated by liquid-phase direct fluorination with elemental fluorine. Degradation of the resulting perfluorinated ester 8 gave 2 mols of the desired acid fluoride 1a. In a sense, this process can be called self-multiplication of a perfluorinated acid fluoride from a non-fluorinated alcohol.

Low-k SiOCH Film Etching Process and Its Diagnostics Employing Ar/C5F10O/N2 Plasma

We proposed an environmental harmonic etching gas of C5F10O (CF3CF2CF2OCFCF2), and demonstrated the etching of low-k SiOCH films employing a dual-frequency capacitively coupled etching system. Dissociative ionization cross sections for the electron impact ionizations of C5F10O and c-C4F8 gases have been measured by quadrupole mass spectroscopy (QMS). The dissociative ionization cross section of CF3+ from C5F10O gas was much higher than those of other ionic species, and 10 times higher than that of CF3+ from C4F8 gas. CF3+ is effective for increasing the etching rate of SiO2. As a result, the etching rate of SiOCH films using Ar/C5F10O/N2 plasma was about 1000 nm/min, which is much higher than that using Ar/C4F8/N2 plasma. The behaviours of fluorocarbon radicals in Ar/C5F10O/N2 plasma, which were measured by infrared diode laser absorption spectroscopy, were similar to those in Ar/C4F8/N2 plasma. The densities of CF and CF3 radicals were markedly decreased with increasing N2 flow rate. Etching rate was controlled by N2 flow rate. A vertical profile of SiOCH with a high etching rate and less microloading was realized using Ar/C5F10O/N2 plasma chemistry.

Comparative studies in the 19F and 1H NMR chemical shifts in 2,2-difluorohalogenated propanes

Abstract Fluorine-19 chemical shifts were compared with 1H chemical shifts in CF3-CF2-R versus CH3-CF2-R, CF2Cl-CF2-R versus CH2Cl-CF2-R and CFCl2-CF2-R versus CHCl2-CF2-R, where R is a substituted methyl group containing all combinations of H, Cl and F. A good linear relationship was found between the 19F and 1H NMR chemical shifts. Conformational analysis using MNDO calculations was applied to the CF3-CF2-R and CH3-CF2-R series to clarify the interaction between the terminal substituents. In halogenated propanes, 19F and 1H chemical shifts are mainly affected by the through-space interaction between the terminal substituents rather than the electronegativity.

Chapter 2: Evaluation and Selection of CFC Alternatives

Abstract This chapter reports on the effect of fluorine compounds in the atmosphere. These compounds have been evaluated for their role in ozone layer depletion and global warming. The state of their application, the use of alternatives and the alternatives themselves were analyzed. There are also explanations of the science behind ozone depletion potential and global-warming potential, of associated evaluation methods, and new methods that can compensate for previous deficiencies. The results suggest that fluorine compounds with short atmospheric lifetimes are suitable as chlorofluorocarbon alternatives.

13C NMR STUDIES OF HYDROCHLOROFLUOROPROPANES AND CHLOROFLUOROPROPANES

Abstract 13C NMR chemical shifts of 3,3-dichloro-1,1,1-trifluoropropanes (CF3-CXY-CHCl2), 3-chloro-2,2,3,3-tetrafluoropropanes (CClF2-CF2-R), and diastereomers of 1,3-dichloro-1,1,2,3-tetrafluoropropane were studied by analysis using MNDO calculations. In CF3-CXY-CHCl2, 13C NMR chemical shifts of the methylene group are dependent on the electronegativity of the atoms attached to the methylene carbon, and those of the trifluoromethyl group depend on the magnetic anisotropy of neighboring halogen atoms X and Y. In CClF2-CF2-R, the magnetic anisotropy of the atoms gauche to the terminal group and the steric effect of the terminal group are responsible for the 13C NMR chemical shift of a terminal halogenated methyl group, and the inductive effect of the substituent R mainly determines the 13C NMR chemical shift of the difluoromethylene group.

Etching Enhancement Followed by Nitridation on Low-k SiOCH Film in Ar/C5F10O Plasma

The etching rates of low-dielectric-constant (low-k), porous SiOCH (p-SiOCH) films were increased by nitrogen-added Ar/C5F10O plasma etching in dual-frequency (60 MHz/2 MHz)-excited parallel plate capacitively coupled plasma. Previously, perfluoropropyl vinyl ether [C5F10O] provided a very high density of CF3+ ions [Nagai et al.: Jpn. J. Appl. Phys. 45 (2006) 7100]. Surface nitridation on the p-SiOCH surface exposed to Ar/N2 plasma led to the etching of larger amounts of p-SiOCH in Ar/C5F10O plasma, which depended on the formation of bonds such as =C(sp2)=N(sp2)– and –C(sp)≡N(sp).

Recyclable Fluorine-Based Cleaning Solvents for Resist Removal

The development of new functional cleaning agents is strongly required for leading-edge LSI fabrication, such as resist removal process without any damage to low-k materials. For example, as excessive acid cleaning agents would damage such materials. Consequently, a low damage cleaning technique with no collapsing fine structures is also desirable. On the other hand, the concept of recycle of cleaning agents is an urgent issue for the reduction of cleaning cost. Therefore, both cleaning ability and easy recyclable function are essential for next generation cleaning agents. Fluorine-based cleaning agents have been widely used for cleaning, rinsing and drying process in the electronics industry. Asahi Glass Corporation (AGC) has commercialized various fluorine-based cleaning agents as AC-series (Hydrofluorocarbon: HFC) and AE-series (Hydorofluoroether: HFE). Typical properties of these compounds are summarized in Table I. Here we report the application of fluorine-based cleaning agents to ArF resist removal and the evaluation of the recycles.

Environmental-Friendship Etching Process of Low-k SiOCH Films Employing an Alternative Fluorocarbon Gas

We have proposed a novel etching gas C₅F₁₀O of which global warming potential would be less than 50, for the plasma etching of SiOCH. The etching was performed using a dual frequency capacitively coupled plasma (CCP). The high performances of a high etching rate and a high selectivity over resist films were obtained. The C₅F₁₀O gas produced many CF₃ ⁺ ions which have a large etching yield due to its special molecular structure and the deposition of polymers was decreased by addition of the N₂ gas. Consequentially, the Ar/C₅F₁₀O/N₂ plasmas have a great potential for realizing a higher etch rate of 980 nm/min and a high etching selectivity over resist of about 7 than the Ar/C₄F₈/N₂ plasmas.

19FNMR study of HCFC propanes

Abstract Asahi Glass has developed HCFC225ca and HCFC225cb as the promising alternatives to CFC113. CF 3 CF 2 CHCl 2 CClF 2 CF 2 CHClF HCFC225ca HCFC225cb During the preliminary survey for the alternatives to CFC113, we have prepared a number of halogenated propanes and found an interesting relationship between 19 FNMR and the structure of those halogenated propanes. For example, the 19 FNMR chemical shift of CF 3 group in the series of CF 3 CF 2 R is affected by the size of R group as shown in Table 1. Those steric effect will be discussed on the basis of MNDO calculation. 1 . CF 3 chemical shift of CF 3 CF 2 R R Chemical shift CF 3 CH 3 −87.2 ppm CH 2 F −85 ppm CH 2 Cl −84.1 ppm CHF 2 −82.8 ppm CF 3 −83.0 ppm CHClF −81.9 ppm CClF 2 −80.9 ppm CHCl 2 −80.1 ppm CCl 2 F −78.1 ppm CCl 3 −75.6 ppm