Simon Karecki

The Use of Unsaturated Fluorocarbons for Dielectric Etch Applications

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 C 3 F 8 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 C 3 F 8 process. Two other C 4 F 6 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 C 3 F 8 process. For the C 4 F 6 isomers, a large portion of the emissions were a result of CHF 3 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.

Use of 2H-heptafluoropropane, 1-iodoheptafluoropropane, and 2-iodoheptafluoropropane for a high aspect ratio via etch in a high density plasma etch tool

An issue currently facing the semiconductor industry is the use and emission of perfluorocompounds (PFCs), gases which are believed to contribute to global warming, in a number of plasma processes used in integrated circuit manufacture, including wafer patterning. Several approaches to reducing emissions of these compounds are being considered, namely abatement, recapture/recovery, process optimization, as well as the development of alternative chemistries as PFC substitutes. The authors present here the results of an effort to test several alternatives in a silicon dioxide etch application (high aspect ratio via etch). 2H-heptafluoropropane, 1-iodoheptafluoropropane, and 2-iodoheptafluoropropane, were tested in an Applied Materials Centura 5300 high density plasma etch tool. Fourier transform infrared spectroscopy was used to analyze the process effluent. The process performance and emissions of the alternative etchants were compared to those of a standard chemistry on the Centura 5300 etch tool.

Use of Novel Hydrofluorocarbon and Iodofluorocarbon Chemistries for a High Aspect Ratio Via Etch in a High Density Plasma Etch Tool

This paper presents the results of an effort to test several novel chemistries for use as replacements for perfluoro-compounds in dielectric etch processes. Chemistries belonging to the hydrofluorocarbon and iodofluorocarbon families, namely, 2H-heptafluoropropane (CF 3 -CFH-CF 3 ), iodotrifluoromethane (CF 3 I),1-iodoheptafluoropropane (CF 2 I-CF 2 -CF 3 ), and 2-iodoheptafluoropropane (CF 3 -CFI-CF 3 ), 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.

High density plasma oxide etching using nitrogen trifluoride and acetylene

The use of nitrogen trifluoride (NF3) and acetylene (C2H2) in the presence of helium has been examined for oxide etching in an inductively coupled, high density plasma etch tool. Oxide etch rates have been measured for blanket films and for patterned wafers with features of 0.6, 0.45, and 0.35 μm nominal critical dimension, while process performance has been assessed with cross-sectional scanning electron microscopy. Optical emission spectroscopy has been employed in situ to characterize the species present in the plasma, and quadrupole mass spectrometry has been used to analyze process effluent sampled between the chamber outlet and the turbo pump inlet. Polymer film deposited on the surface of the oxide layer has been studied with time-of-flight secondary ion mass spectrometry. Global warming emissions for a range of process conditions have been quantified using Fourier transform infrared spectroscopy, and are compared to emissions from more typical oxide etch processes on the same tool type. Results in...

Plasma etching of dielectric films with novel iodofluorocarbon chemistries: Iodotrifluoroethylene and 1-iodoheptafluoropropane

The use of two novel etch chemistries belonging to the iodofluorocarbon family, iodotrifluoroethylene and 1-iodoheptafluoropropane, has been investigated in a dielectric etch application. These substances are being explored as potential alternatives to perfluorocompounds, a fully fluorinated class of etchants that is presently in widespread use in dielectric etch processes. Whereas perfluorocompounds have global warming properties once emitted into the atmosphere, iodofluorocarbons such as those discussed in this work are presently believed not to possess long-term environmental impacts. Under the conditions tested, the two iodofluorocarbons discussed in this work have both been found to etch silicon dioxide films readily. Note that 1-iodoheptafluoropropane has also been found to be capable of etching silicon nitride films under these conditions. An Applied Materials Precision 5000 etch tool was used in this work.

Characterization of iodoheptafluoropropane as a dielectric etchant. III. Effluent analysis

The work presented in this article represents the third and final part of a series of articles which present a systematic evaluation of iodoheptafluoropropane (C3F7I) 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 (FTIR) spectroscopy. Data generated by both isomers of the compound will be presented and compared to those generated by conventional (C3F8- and C2F6-based) etch processes. Significant reductions in global warming emission (on the order of 80%–85%) were obtained relative to the convent...

Characterization of iodoheptafluoropropane as a dielectric etchant. I. Process performance evaluation

1- and 2-iodoheptafluoropropane were characterized extensively as potential replacement etchants for perfluorocompounds used in an oxide etch application. In the present study, via holes of critical dimension down to 0.35 μm were etched in an inductively coupled high density plasma tool. Oxide etch rate, mask and stop layer selectivities, and feature profile were among the principal metrics used to evaluate the performance of these compounds. A conventional (C3F8-based) etch process was used as a reference. Process behavior as a function of a number of variables—namely source power, bias power, etch gas flow, additive gas CH3F) flow, roof, wall, and chiller temperatures, and pressure was studied. While good etch rates and feature profiles were obtained, mask and stop layer selectivity was found to be limited. As a supplement to the experimental work, a set of ab initio quantum chemical calculations was undertaken to obtain enthalpies of dissociation for each of the bonds in the iodoheptafluoropropane mole...

Characterization of iodoheptafluoropropane as a dielectric etchant. II. Wafer surface analysis

This article forms the second part of a three-part series which presents a systematic characterization of iodoheptafluoropropane (C3F7I) based oxide etch processes in an inductively coupled high density plasma etch tool. Parts I and III of the article discuss etch process behavior and effluent composition, respectively. The focus of this article is on the characterization of films deposited by 1-iodoheptafluoropropane (CF2I–CF2–CF3) processes using two techniques: X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. A significant result obtained in this study is that, while iodoheptafluoropropane has a greater tendency to polymerize than its perfluorinated counterpart, C3F8, because of its lower F:C ratio, the C3F7I etch process is driven, in large part, by physical mechanisms stemming from bombardment of the wafer surface by massive iodine ions. The mechanisms discussed in this article provide a consistent explanation that reconciles the highly polymerizing behavior of iodoheptafluoropropane with its relatively low mask and stop layer selectivity, as compared to a C3F8 based process in the same inductively coupled etch tool.This article forms the second part of a three-part series which presents a systematic characterization of iodoheptafluoropropane (C3F7I) based oxide etch processes in an inductively coupled high density plasma etch tool. Parts I and III of the article discuss etch process behavior and effluent composition, respectively. The focus of this article is on the characterization of films deposited by 1-iodoheptafluoropropane (CF2I–CF2–CF3) processes using two techniques: X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. A significant result obtained in this study is that, while iodoheptafluoropropane has a greater tendency to polymerize than its perfluorinated counterpart, C3F8, because of its lower F:C ratio, the C3F7I etch process is driven, in large part, by physical mechanisms stemming from bombardment of the wafer surface by massive iodine ions. The mechanisms discussed in this article provide a consistent explanation that reconciles the highly polymerizing behavior of iod...