Six unsaturated fluorocarbon (UFC) gases as well as a fluorinated ether were examined for dielectric etch and global warming emissions performance and compared to three perfluorocompound (PFC) gases. All of the gases were capable of etch performance comparable to that of a typical C3F8 process, while exhibiting superior global warming emissions performance compared to the PFCs. A low-flow hexafluoro-2-butyne process was found to have a significant emissions benefit, showing a normalized emissions reduction of 88.2% compared to the C3F8 process. Two other C4F6 isomers (hexafluoro-1,3-butadiene and hexafluorocyclobutene) also exhibited reductions greater than 80%, while hexafluoropropene and octafluorocyclopentene exhibited emissions reductions greater than 70% compared to the typical C3F8 process. For the C4F6 isomers, a large portion of the emissions were a result of CHF3 formation with photoresist as the sole source of the hydrogen. An extended 4 min etch with hexafluoro-1,3-butadiene resulted in a deep via with an aspect ratio of 5:1, very high selectivity to photoresist, and no evidence of etch stopping. © 2002 The Electrochemical Society. All rights reserved.

Gas-phase Fourier transform infrared spectroscopy (FTIR) has been used to analyze the effluents from C2H2F4, hexafluoropropylene oxide (CF3CFOCF2, HFPO), and CH2F2 pulsed plasmas. A series of reference spectra for possible effluent species was used to identify the major species in each. The major species in pulsed C2H2F4 plasmas were found to be: C2H2F4, HF, C2F4, C2HF5, CHF3, and SiF4 (formed from free fluorine). For HFPO pulsed plasmas, the major effluents are: HFPO, CF3COF3, COF2, C2F4, C2F6, CO, CF4, and C3F8, whereas for CH2F2 pulsed plasmas, the major effluents are: CH2F2, HF, SiF4, and CHF3. Reaction sets were postulated for each precursor to account for the observed effluents, and these sets were used to explain the trends of species concentrations with pulse on and pulse off time. In each case, most of the effluent concentration trends could be traced back to competition between dissociation pathways of a particular molecule. For both C2H2F4 and CH2F2, the main reactions were the competition between CF2 production and HF elimination from the original precursor. For C2H2F4 pulsed plasmas, the competition between these pathways was found to be ∼1:1, whereas for CH2F2 pulsed plasmas, the HF elimination pathway is dominant. For HFPO, the key reactions are the three dissociation pathways of CF3COF, a main product of the initial dissociation of HFPO into CF2+CF3COF. The global warming impact of each of the pulsed plasma enhanced chemical vapor deposition processes was gauged by the million metric tons of carbon equivalent (MMTCE) metric. CH2F2 pulsed plasmas were found to have the lowest MMTCE (min=2.1×106), whereas HFPO pulsed plasmas had the highest MMTCE (max=7.7×107). For all three precursors, the MMTCE impact is reduced by decreasing the exposure to plasma excitation through increasing the off time at a fixed on time.

Figure 9. The FTIR absorbance spectrum for C 4 F 8 O.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199 Downloaded on 2015-05-29 to IP

The goal of the work presented in this article was to provide a preliminary screening for a novel fluorinated compound, oxalyl fluoride, C 2 O 2 F 2 (F-͑CϭO)-(CϭO͒-F), as a potential replacement for perfluorocompounds in dielectric etch applications. Both process and emissions data were collected and the results were compared to those provided by a process utilizing a standard perfluorinated etch chemistry (C 2 F 6 ). In this evaluation, oxalyl fluoride produced very low quantities of global warming compounds under the conditions in which it was tested, as compared to the C 2 F 6 process. A preliminary evaluation of the compound's process performance was also carried out. Patterned tetraethoxysilane-deposited silicon oxide masked with deep UV photoresist having 0.6, 0.45, and 0.35 m via hole features was used as the test vehicle. Although C 2 O 2 F 2 was capable of etching silicon dioxide, low oxide etch rate and poor selectivity to the mask layer were observed. Finally, in addition to the experimental work performed, a set of ab initio quantum chemical calculations was undertaken to obtain enthalpies of dissociation for each of the bonds in the oxalyl fluoride molecule in order to better understand its dissociation pathways in plasma environments.

This paper presents the results of an effort to test several novel chemistries for use as replacements for perfluorocompounds in dielectric etch processes. Chemistries belonging to the hydrofluorocarbon and iodofluorocarbon families, namely, 2H-heptafluoropropane (CF3-CFH-CF3), iodotrifluoromethane (CF3I), l-iodoheptafluoropropane (CF2I-CF2-CFj, and 2-iodoheptafluoropropane (CFrCFI-CF3), were tested in an Applied Materials Centura 5300 HDP etch tool, using a high aspect ratio silicon dioxide via etch application as the test vehicle. Designed experiment methodology was used in the evaluation. Effluent was analyzed using Fourier transform infrared spectroscopy and quadrupole mass spectrometry. The performance of the alternative etchants in a high aspect ratio via etch process was compared to that of a standard chemistry on the Centura 5300 etch tool. Significant reductions in global warming emissions, relative to a perfluorinated baseline process, were found to be attainable with the alternative chemistries.

Hexafluorobenzene was evaluated as an alternative chemistry for dielectric etch applications in a high density plasma etch chamber with reduced global warming emissions. Processes based on hexafluorobenzene exhibited global warming emissions reductions as high as 97% compared to a C 3 F 8 -based process, which is the greatest reductions level of any alternative chemistry examined to date on this tool. Using hexafluorobenzene, it is possible to operate in a regime of high etch rate and high polymerization. There are several issues, however, that need to be addressed if this chemistry is to be used for high performance dielectric etching. This material is a liquid at room temperature, which makes it difficult to deliver process gas to the chamber. In addition, this chemistry is highly polymerizing, resulting in excess polymer deposition on chamber walls leading to significant process variability for standard chamber clean times. Significantly longer chamber clean times were required between each etch to remove the excess polymer.

One environmental issue currently facing the semiconductor industry is the emission of perfluorinated compounds (PFCs) from a variety of processes including chamber cleaning following plasma enhanced chemical vapor deposition (PECVD) of dielectrics. The emission of PFCs has been targeted for reduction due to the contribution of these species to global warming. An option under investigation is the use of alternative compounds that emit lower amounts of global warming species. The current study presents chamber cleaning times and emissions from the use of one such species, trifluoroacetic anhydride (TFAA), in a widely used commercial PECVD tool, the Novellus Concept One 200. A central composite design-of-experiments was employed to calculate response surfaces for the chamber clean time and PFC emission concentrations as the chamber pressure, TFAA flow rate, and oxygen flow rate were varied. The chamber clean times were measured using optical emission spectroscopy, quadrupole mass spectrometry, as well as Fourier transform infrared (FTIR) spectroscopy, and the PFC emissions were quantified using FTIR spectroscopy. The performance of TFAA is compared to standard Novellus Concept One 200 C2F6 and C3F8 chamber cleaning processes and to processes in which the effect of augmentation of C2F6 with NF3 is studied.

Use of 2H-heptafluoropropane, 1-iodoheptafluoropropane, and 2-iodoheptafluoropropane for a high aspect ratio via etch in a high density plasma etch toolThe work presented in this article represents the third and final part of a series of articles which present a systematic evaluation of iodoheptafluoropropane (C 3 F 7 I) as a potential replacement for perfluorocompound chemistries in dielectric etch applications. In the experiments discussed in this series, 1-and 2-iodoheptafluoropropane based etch processes had been employed in a via etch application in an inductively coupled high density plasma etch tool. Part I of this article discusses etch process behavior of 1-and 2-iodoheptafluoropropane, while Part II examines films deposited by the 1-iodo isomer. This article will focus on the composition of the process effluent stream, as characterized by Fourier transform infrared ͑FTIR͒ spectroscopy. Data generated by both isomers of the compound will be presented and compared to those generated by conventional (C 3 F 8 -and C 2 F 6 -based͒ etch processes. Significant reductions in global warming emission ͑on the order of 80%-85%͒ were obtained relative to the conventional processes. Additionally, FTIR data were correlated with process and film analysis data presented in Parts I and II to generate better understanding of key plasma mechanisms in iodofluorocarbon etch environments.