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May 2013

Volume 31, Issue 3, Articles (03xxxx)

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J. Vac. Sci. Technol. A 31, 030801 (2013); http://dx.doi.org/10.1116/1.4794357 (24 pages)

Yalin Dong, Qunyang Li, and Ashlie Martini
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Characteristics of silicon etching by silicon chloride ions

Tomoko Ito, Kazuhiro Karahashi, Song-Yun Kang, and Satoshi Hamaguchi

J. Vac. Sci. Technol. A 31, 031301 (2013); http://dx.doi.org/10.1116/1.4793426 (5 pages)

Online Publication Date: 1 March 2013

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Plasmas generated from halogen-containing gases, such as Cl2 or HBr, have been widely used in gate etching processes for semiconductor chip manufacturing. Such plasmas may contain silicon halide ions formed by the ionization of etching products that enter the plasma. In this study, to illustrate Si etching by such silicon halide ions, the sputtering yield of Si by SiClx+ (with x = 1 or 3) ions has been obtained as a function of the incident ion energy by using a mass-selected ion beam injection system. It has been found that, at sufficiently low energy, the incidence of SiCl+ ions leads to the deposition of Si which may affect profile control in microelectronic device fabrication processes.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning

Real-time control of electron density in a capacitively coupled plasma

Bernard Keville, Yang Zhang, Cezar Gaman, Anthony M. Holohan, Stephen Daniels, and Miles M. Turner

J. Vac. Sci. Technol. A 31, 031302 (2013); http://dx.doi.org/10.1116/1.4795207 (12 pages)

Online Publication Date: 22 March 2013

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Reactive ion etching (RIE) is sensitive to changes in chamber conditions, such as wall seasoning, which have a deleterious effect on process reproducibility. The application of real time, closed loop control to RIE may reduce this sensitivity and facilitate production with tighter tolerances. The real-time, closed loop control of plasma density with RF power in a capacitively coupled argon plasma using a hairpin resonance probe as a sensor is described. Elementary control analysis shows that an integral controller provides stable and effective set point tracking and disturbance attenuation. The trade off between performance and robustness may be quantified in terms of one parameter, namely the position of the closed loop pole. Experimental results are presented, which are consistent with the theoretical analysis.
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52.77.Bn Etching and cleaning
52.25.-b Plasma properties
52.70.Ds Electric and magnetic measurements

Nitrogen actinometry for measurement of nitrogen radical spatial distribution in large-area plasma-enhanced chemical vapor deposition

Changhoon Oh, Minwook Kang, Seungsuk Nam, and Jae W. Hahn

J. Vac. Sci. Technol. A 31, 031303 (2013); http://dx.doi.org/10.1116/1.4798772 (5 pages)

Online Publication Date: 2 April 2013

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Density distributions of radicals in the large-area silicon nitride (Si3N4) plasma-enhanced chemical vapor deposition (PECVD) process were measured using a spatially resolvable optical emission spectrometer (SROES). To determine the qualitative distribution of a target radical, the authors used optical actinometry with nitrogen (N2) gas as an actinometer. To compare the SROES data and process results, the thickness of the deposited Si3N4 thin films using an ellipsometer was measured. By introducing nitrogen-based optical actinometry, the authors obtained very good agreement between the experimental results of the distributions of atomic nitrogen radical and the deposited thicknesses of Si3N4 thin films. Based on these experimental results, the uniformity of the process plasma in the PECVD process at different applied radio frequency powers was analyzed.
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07.60.Dq Photometers, radiometers, and colorimeters
52.77.Dq Plasma-based ion implantation and deposition
07.60.Fs Polarimeters and ellipsometers
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Computational modeling study of the radial line slot antenna microwave plasma source with comparisons to experiments

Laxminarayan L. Raja, Shankar Mahadevan, Peter L. G. Ventzek, and Jun Yoshikawa

J. Vac. Sci. Technol. A 31, 031304 (2013); http://dx.doi.org/10.1116/1.4798362 (11 pages) | Cited 1 time

Online Publication Date: 8 April 2013

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The radial line slot antenna plasma source is a high-density microwave plasma source comprising a high electron temperature source region within the plasma skin depth from a coupling window and low electron temperature diffusion region far from the window. The plasma is typically comprised of inert gases like argon and mixtures of halogen or fluorocarbon gases for etching. Following the experimental study of Tian et al. [J. Vac. Sci. Technol. A 24, 1421 (2006)], a two-dimensional computational model is used to describe the essential features of the source. A high density argon plasma is described using the quasi-neutral approximation and coupled to a frequency-domain electromagnetic wave solver to describe the plasma-microwave interactions in the source. The plasma is described using a multispecies plasma chemistry mechanism developed specifically for microwave excitation conditions. The plasma is nonlocal by nature with locations of peak power deposition and peak plasma density being very different. The spatial distribution of microwave power coupling depends on whether the plasma is under- or over-dense and is described well by the model. The model predicts the experimentally observed low-order diffusion mode radial plasma profiles. The trends of spatial profiles of electron density and electron temperature over a wide range of power and pressure conditions compare well with experimental results.
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52.50.Dg Plasma sources
52.65.-y Plasma simulation
52.75.-d Plasma devices
52.25.-b Plasma properties

Selective etching of TiN over TaN and vice versa in chlorine-containing plasmas

Hyungjoo Shin, Weiye Zhu, Lei Liu, Shyam Sridhar, Vincent M. Donnelly, Demetre J. Economou, Chet Lenox, and Tom Lii

J. Vac. Sci. Technol. A 31, 031305 (2013); http://dx.doi.org/10.1116/1.4801883 (6 pages)

Online Publication Date: 18 April 2013

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Selectivity of etching between physical vapor-deposited TiN and TaN was studied in chlorine-containing plasmas, under isotropic etching conditions. Etching rates for blanket films were measured in-situ using optical emission of the N2 (C3Πu →B3Πg) bandhead at 337 nm to determine the etching time, and transmission electron microscopy to determine the starting film thickness. The etching selectivity in Cl2/He or HCl/He plasmas was poor (<2:1). There was a window of very high selectivity of etching TiN over TaN by adding small amounts (<1%) of O2 in the Cl2/He plasma. Reverse selectivity (10:1 of TaN etching over TiN) was observed when adding small amounts of O2 to the HCl/He plasma. Results are explained on the basis of the volatility of plausible reaction products.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning

Impact of static magnetic fields on the radial line slot antenna plasma source

Jun Yoshikawa and Peter L. G. Ventzek

J. Vac. Sci. Technol. A 31, 031306 (2013); http://dx.doi.org/10.1116/1.4802737 (10 pages)

Online Publication Date: 26 April 2013

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The radial line slot antenna plasma source is used in semiconductor device fabrication. As is the case for all plasma sources, ever more strict uniformity control requirements are driven by the precision demands of new device technologies. Large volume diffusion plasmas, of which the radial line slot antenna source is one type, must overcome transport effects or diffusion modes that tend to “center peak” the plasma density near the wafer being processed. One way to resolve problematic transport effects is the insertion of magnetic fields into the plasma region. In this paper, the impact of the magnetic field on plasma properties is parameterized as a function of slot configuration. The magnetic field orientation and the magnitude of magnetic field are varied in a computational study in which the source is modeled as a two-dimensional axisymmetric quasineutral plasma. This work employs a finite element model simulation. The magnitude of magnetic fields considered is 50 Gauss maximum with a microwave power of 3000 W at a pressure of 20 mTorr. 20 mTorr is chosen as this is a condition where diffusion effects are challenging to counteract. The study showed that there are specific conditions for slot configuration and magnetic field that improve the plasma controllability and some that do not. Plasma property modulation is most effective when the plasma source region is placed at large radius with axial magnetic fields. There are synergistic effects between the slot location and magnetic field that are important and placing large magnetic fields at the chamber edge alone does not result in improved uniformity. Electron cyclotron resonance (ECR) heating and the impact of pulsing the magnetic fields are presented. ECR heating is not important for the conditions relevant to this paper and pulsing is shown to have benefit.
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52.50.Dg Plasma sources
52.65.Pp Monte Carlo methods
51.20.+d Viscosity, diffusion, and thermal conductivity
52.25.Fi Transport properties
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
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