Optical emission spectroscopy of reactive plasmas: A method for correlating emission intensities to reactive particle density
01 Jun 1980-Journal of Applied Physics (American Institute of Physics)-Vol. 51, Iss: 6, pp 3134-3136
TL;DR: In this article, a small concentration of suitably chosen noble gas to a reactive plasma is shown to permit the determination of the functional dependence of reactive particle density on plasma parameters, and examples illustrating the simplicity of this method are presented using F atomic emission from plasma-etching discharges and a comparison is made to available data in the literature.
Abstract: The addition of a small concentration of suitably chosen noble gas to a reactive plasma is shown to permit the determination of the functional dependence of reactive particle density on plasma parameters. Examples illustrating the simplicity of this method are presented using F atomic emission from plasma‐etching discharges and a comparison is made to available data in the literature.
Citations
More filters
TL;DR: The field of plasma etching is reviewed in this paper, where basic principles related to plasma etch such as evaporation rates and Langmuir-Hinshelwood adsorption are introduced.
Abstract: The field of plasma etching is reviewed. Plasma etching, a revolutionary extension of the technique of physical sputtering, was introduced to integrated circuit manufacturing as early as the mid 1960s and more widely in the early 1970s, in an effort to reduce liquid waste disposal in manufacturing and achieve selectivities that were difficult to obtain with wet chemistry. Quickly, the ability to anisotropically etch silicon, aluminum, and silicon dioxide in plasmas became the breakthrough that allowed the features in integrated circuits to continue to shrink over the next 40 years. Some of this early history is reviewed, and a discussion of the evolution in plasma reactor design is included. Some basic principles related to plasma etching such as evaporation rates and Langmuir–Hinshelwood adsorption are introduced. Etching mechanisms of selected materials, silicon, silicon dioxide, and low dielectric-constant materials are discussed in detail. A detailed treatment is presented of applications in current silicon integrated circuit fabrication. Finally, some predictions are offered for future needs and advances in plasma etching for silicon and nonsilicon-based devices.
539 citations
TL;DR: A review of the United States patent literature on plasma surface modification technologies and a brief review of scientific literature on investigations of the effects of plasma treatment, the nature of the plasma environment, and the mechanisms that drive the plasma interaction are provided in this article.
Abstract: Plasma treatment of polymers encompasses a variety of plasma technologies and polymeric materials for a wide range of applications and dates back to at least the 1960s. In this article we provide a brief review of the United States patent literature on plasma surface modification technologies and a brief review of the scientific literature on investigations of the effects of plasma treatment, the nature of the plasma environment, and the mechanisms that drive the plasma–surface interaction. We then discuss low‐radio‐frequency capacitively coupled nitrogen plasmas and their characteristics, suggesting that they provide significant plasma densities and populations of reactive species for effective plasma treatments on a variety of materials, particularly when placing the sample surface in the cathode sheath region. We further discuss surface chemical characterization of treated polymers, including some results on polyesters treated in capacitively coupled nitrogen plasmas driven at 40 kHz. Finally,...
317 citations
Cites result from "Optical emission spectroscopy of re..."
...Emissions from N atoms can be normalized to those observed from N2 as done by Fancey, who used N atom emissions at 493.5 nm and 746.8 nm and molecular emissions at 380.4 nm and 337.1 nm.[116] This approach is similar to the actinometry approach of Coburn and Chen,[117] except that the background molecular nitrogen serves as the actinometer, and thus its validity for determining the relative concentration of N atoms is limited to the case of weak dissociation....
[...]
...This approach is similar to the actinometry approach of Coburn and Chen,([117]) except that the background molecular nitrogen serves as the actinometer, and thus its validity for determining the relative concentration of N atoms is limited to the case of weak dissociation....
[...]
...As discussed by Coburn and Chen, the underlying assumption in using emission intensity ratios to determine relative concentrations of species is that any changes in the electron energy distribution function in the discharge are compensated by taking the ratio of the emission intensity of interest to that of a specie of known concentration whose excitation threshold for emission is as close as possible to that of the specie of interest....
[...]
TL;DR: In this article, an intensive study has been performed to understand and tune deep reactive ion etch (DRIE) processes for optimum results with respect to the silicon etch rate, etch profile and mask etch selectivity.
Abstract: An intensive study has been performed to understand and tune deep reactive ion etch (DRIE) processes for optimum results with respect to the silicon etch rate, etch profile and mask etch selectivity (in order of priority) using state-of-the-art dual power source DRIE equipment. The
research compares pulsed-mode DRIE processes (e.g. Bosch technique) and mixed-mode DRIE processes (e.g. cryostat technique). In both techniques, an inhibitor is added to
fluorine-based plasma to achieve directional etching, which is formed out of an oxide-forming (O2) or a fluorocarbon (FC) gas (C4F8 or CHF3). The inhibitor can be introduced together with the etch gas, which is named a mixed-mode DRIE process, or the inhibitor can be added in a
time-multiplexed manner, which will be termed a pulsed-mode DRIE process. Next, the most convenient mode of operation found in this study is highlighted including some remarks to
ensure proper etching (i.e. step synchronization in pulsed-mode operation and heat control of the wafer). First of all, for the fabrication ......
Enjoy reading . Henri Jansen 18 June 2008
275 citations
TL;DR: In this paper, the authors used two-photon laser-induced fluorescence to obtain quantitative measurements of the concentration of ground state O atoms in O2+CF4-rf discharges.
Abstract: We have used two‐photon laser‐induced fluorescence to obtain quantitative measurements of the concentration of ground state O atoms in O2+CF4 rf discharges. Absolute calibration was achieved by generating a known concentration of atomic oxygen by UV laser photolysis of O2. Trace amounts of Ar were added to serve as an inert reference gas for concurrent optical emission measurements, in which the plasma‐induced optical emission intensities from O* and Ar* lines were recorded. Emission line shapes were measured using a Fabry–Perot interfermoter to gain information on the mechanisms for formation of excited oxygen atoms in the plasma. Two excitation mechanisms were found to be important: (1) electron impact excitation of ground state atoms, e+O → O*+e, and (2) dissociative excitation of O2, e+O2 → O*+O+e. Evidence for both excitation mechanisms was obtained for O* (8446 A) emission, with atomic excitation being dominant, whereas dissociative excitation appeared to be the dominant mechanism for O* (7774 A) em...
237 citations
TL;DR: In this paper, the authors used plasma emission actinometry to study the mechanism by which small additions of oxygen (∼0.5%) enhance the rate of diamond deposition in a dilute (4%) CH4/H2 discharge at high temperature (900-1300 K).
Abstract: Plasma emission actinometry has been used to study the mechanism by which small additions of oxygen (∼0.5%) enhance the rate of diamond deposition in a dilute (4%) CH4/H2 discharge at high temperature (900–1300 K). Increasing amounts of CH4 in the feed depress [H], while increasing the O2 concentration, up to ∼5%, produces a fivefold increase in atomic hydrogen in the discharge zone. Invoking a mechanism where diamond growth competes with the formation of an amorphous/graphitic inhibiting layer, these results and earlier studies suggest that oxygen (1) increases [H] which selectively etches amorphous/graphitic carbon, (2) accelerates reaction of this layer with molecular hydrogen, and (3) may itself act as a selective etchant of nondiamond carbon. As a result, the number of active diamond growth sites is increased and enhanced growth rates are observed. We also have grown diamond by alternating a CH4/He discharge with a H2/O2/He discharge and results are consistent with this mechanism. Instantaneous growt...
236 citations
References
More filters
IBM1
TL;DR: In this paper, the etching process is discussed in terms of three basic steps: adsorption, product formation, and product desorption with the goal of clarifying the relative importance of these three steps.
Abstract: The purpose of the present paper is to review the salient features of our understanding of phenomena which occur in plasma etching situations. The etching process is discussed in terms of three basic steps: adsorption, product formation, and product desorption. Experiments performed in well‐defined (nonplasma) environments are discussed with the goal of clarifying the relative importance of these three steps in the etching process. An attempt is made to relate the resulting concepts to several phenomena generally observed in plasma situations (e.g. etching anisotropy, selective etching, the loading effect, and the role of additive gases). Moreover, the glow discharge, in addition to generating active species which initiate the chemical reactions, also causes the etched surface to be subjected to energetic particle (ions, electrons) bombardment. The role of this radiation in the etching process is emphasized. Speculative comments relating to plasma etching parameters and apparatus are also given.
484 citations
TL;DR: In this article, the plasma etching of silicon and silicon dioxide in CF4-O2 mixtures has been studied as a function of feed-gas composition in a 13.56MHz plasmagenerated in a radial flow reactor at 200 W and 0.35 Torr.
Abstract: The plasma etching of silicon and silicon dioxide in CF4‐O2 mixtures has been studied as a function of feed‐gas composition in a 13.56‐MHz plasmagenerated in a radial‐flow reactor at 200 W and 0.35 Torr. Conversion of CF4 to stable products (CO, CO2, COF2, and SiF4) and the concentration of free F atoms ([F]) in the plasma were measured using a number of different diagnostics. The rate of etching, the concentration of F atoms, and the intensity of emission from electronically excited F atoms (3s 2 P–3p 2 P° transition at 703.7 nm) each exhibit a maximum value as a function of feed‐gas composition ([O2]); these respective maxima occur at distinct oxygen concentrations. For SiO2, the variation in etching rate with [O2] is accounted for by a proportional variation in [F], the active etchant. The etching of silicon also occurs by a reaction with F atoms, but oxygen competes with F for active surface sites. A quantitative model which takes oxygen adsorption into account is used to relate the etch rate to [F]. The initial increase of [F] with [O2] is accounted for by a sequence of reactions initiating with the production of CF3 radicals by electron impact and followed by a reaction of CF3 with oxygen. When [O2] exceeds ∼23% (under the present discharge conditions), [F] decreases due, probably, to a decrease in electron energy with an increase of oxygen in the feed gas.
482 citations
TL;DR: The dependence of etch rate on the quantity of material being etched, often referred to as the loading effect, for plasma etching is analyzed quantitatively with the aid of some simplifying assumptions as mentioned in this paper.
Abstract: The dependence of etch rate on the quantity of material being etched, often referred to as the loading effect, for plasma etching is analyzed quantitatively with the aid of some simplifying assumptions. The etch rate is related to the quantity of material being etched through three phenomenological parametersβ, τ, and , which are related to the affinity of the etching material for the active species created in the plasma, the lifetime of the active species, and the volume generation rate of the active species, respectively. It is shown analytically that the reciprocal of the etch rate, when identical wafers are etching simultaneously, is directly proportional to . Data are presented for the plasma etching of Si in a plasma which confirm the analytical prediction. The significance of loading with respect to the measurement of etch rate, end‐point detection, and the interpretation of the temperature dependence of etch rate is discussed. A brief discussion of the physical meaning of the phenomenological parameters and their relation to process parameters subject to control such as power, pressure, and temperature is also included.
202 citations
TL;DR: In this paper, the authors used spectroscopic analysis of optical emission during rf plasma etching of semiconductor materials to gain a better understanding of the plasma chemistry involved in these systems.
Abstract: Spectroscopic analysis of optical emission during rf plasma etching of semiconductor materials has been used to gain a better understanding of the plasma chemistry involved in these systems. The emission was studied principally in CF4−O 2 gas mixtures, but other gases were observed as well. It is known that the addition of a relatively small percentage of O2 to CF4 yields a much faster etching rate for silicon and silicon nitride. With the addition of O2 to CF4 discharges we have studied emission from atomic O and molecular CO with a large increase in the emission of atomic F. When the plasma is actively etching silicon or silicon nitride, the emission intensities of both F and O atoms are significantly lower. The etching process can be monitored by observing the intensities of these lines. Analysis of the emission features has also been used to determine abnormal conditions which can adversely affect the etching process.
142 citations
TL;DR: Plasma etching, the selective etching of material by reaction with chemically active radicals in a glow discharge, is dry and clean, and offers process simplification and improved dimensional tolerances compared to existing wet chemical-etching processes in semiconductor integrated circuit (IC) device fabrication as mentioned in this paper.
Abstract: Plasma etching, the selective etching of material by reaction with chemically active radicals in a glow discharge, is dry and clean, and offers process simplification and improved dimensional tolerances compared to existing wet‐chemical‐etching processes in semiconductor integrated circuit (IC) device fabrication. In this paper previously published work on plasma etching and apparatus is reviewed, new processes and techniques for Al and Al–Si plasma etching and for the precise control of etchrates and detection of etchcycle endpoints are reported, and plasma etching and stripping are shown to be fully compatible with silicon gate, metal–oxide–semiconductor (MOS) device processing in a new ’’fully plasma‐etched ion‐implanted’’ 2‐μm channel‐length CMOS process. It is concluded that plasma etching and stripping technologies can have a significant impact on MOS manufacturing, in improving the tolerances and yield of conventional geometry devices with 4‐μm minimum linewidth, and in improving the resolution to ...
112 citations