Bulletin of the American Physical Society
62nd Annual Gaseous Electronics Conference
Volume 54, Number 12
Tuesday–Friday, October 20–23, 2009; Saratoga Springs, New York
Session TR1: Materials Processing |
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Chair: Jean-Paul Booth, CNRS - Ecole Polytechnique Room: Saratoga Hilton Ballroom 1 |
Thursday, October 22, 2009 1:30PM - 2:00PM |
TR1.00001: Reaction mechanisms in patterning complex oxide materials by plasmas Invited Speaker: The continuous down-scaling of the microelectronic and optoelectronic integrated circuits dictates the development of atomic layer deposition and high fidelity pattern transfer processes to synthesize and integrate novel materials, such as multifunctional oxides, into nanometer scaled devices. As the introduction of new gate dielectric materials in sub-32-nm metal oxide semiconductor field effect transistors (MOSFET) increases the complexity of the gate stack etch process, it is critical to formulate a comprehensive kinetics model to predict the physical and chemical effects of plasma chemistries on these complex gate dielectric materials. In this talk, I will highlight recent work on delineating the reaction mechanism in patterning complex metal oxides in halogen based plasmas. In general, the etch-rate scaled with the square-root of ion energy, and was dictated by the chemical nature of the dominant reaction ions in the plasma. The dominant metal-containing etch products were mainly MCl$_x$ species, and their intensity and complexity increased with ion energy. A model was formulated to accurately describe the etching of composite oxide films in complex plasma chemistries involving competing deposition and etching mechanisms. This site balance-based model explains the etch-rate dependence on key plasma parameters including plasma chemistry/condition, neutral-to-ion flux ratio, and ion energy, as well as the film composition. The model fits well to a wide range of experimental data demonstrating its validity and potential application to various plasma etching processes. [Preview Abstract] |
Thursday, October 22, 2009 2:00PM - 2:15PM |
TR1.00002: Surface Modification of Polymer Photoresists in Fluorocarbon Plasma Etching Mingmei Wang, Mark Kushner In plasma etching of high aspect ratio (AR), nm sized features, erosion of polymer photoresist (PR) can perturb the feature profile (e.g., bowing). Although cross-linking of PR due to ion and VUV fluxes could make it more resistive to etching, typically the PR etch rate is too high to maintain the pattern when the AR is large ($>$ 20). In dielectric plasma etching using fluorocarbon gases, one strategy to prevent PR erosion is to deposit a (C$_{x}$F$_{y})_{n}$ polymer on its surface. This process may be enhanced in dc-augmented capacitively coupled plasmas (CCPs) by sputtering of Si and C$_{x}$F$_{y}$ from the dc biased electrode. Dangling bonds generated on the PR surface by ion, photon or electron bombardment trap Si and C$_{x}$F$_{y}$ radicals forming Si-C and C-C bonds. Sputtered Si atoms can also react with C$_{x}$F$_{y}$ radicals to produce more reactive C$_{x}$F$_{y-1}$ radicals which are more easily incorporated into the PR. In this talk we discuss scaling laws for radical production derived from a computational investigation of a dc-augmented dual frequency CCP reactor sustained in Ar/C$_{4}$F$_{8}$/O$_{2}$. Fluxes of Si radicals are produced by sputtering of the dc electrode. Rates of polymer deposition on and sputtering of PR, and consequences of PR erosion (and deposition) on feature profiles will be discussed. [Preview Abstract] |
Thursday, October 22, 2009 2:15PM - 2:30PM |
TR1.00003: Factors Affecting the Sealing Efficiency of Low-$k$ Dielectric Surface Pores Using Successive He and Ar/NH$_{3}$ Plasma Treatment Juline Shoeb, Mark Kushner Sequential treatment of porous SiCOH by He and NH$_{3}$ plasmas is effective at sealing pores while maintaining the low-$k$ of the dielectric. He plasmas activate surface sites to accelerate the reactions responsible for pore sealing. Additional NH$_{3}$ plasma treatment completes the sealing through formation of Si-N, C-N and N-N bonds resulting from the adsorption of NH$_{x}$. To seal pores, sufficient He plasma exposure time is required to break Si-O bonds at SiO$_{2}$ sites and to activate pore lining CH$_{n}$ groups by removal of H atoms. Sealing efficiency degrades if the pore radius is too large to link the sites of opposite pore walls by Si-N-N-C, Si-N-N-Si or C-N-N-C chains. In this talk, we discuss results from a computational investigation of the sealing efficiency of a porous carbon doped silica films (SiOCH). The Hybrid Plasma Equipment Model provided the fluxes of ions, neutrals and photons onto the surface from He and NH$_{3}$/Ar ICPs. The sealing mechanism was implemented in the Monte Carlo Feature Profile Model with which profiles of the low-$k $pores are predicted. Factors affecting the sealing efficiency, such as treatment time, bias, average pore radius and pore radius standard deviation will be discussed. [Preview Abstract] |
Thursday, October 22, 2009 2:30PM - 2:45PM |
TR1.00004: The influence of He plasma pretreatment on O and H atom interaction with low-k nanoporous materials O.V. Braginsky, A.S. Kovalev, D.V. Lopaev, E.M. Malykhin, Yu. A. Mankelevich, T.V. Rakhimova, A.T. Rakhimov, A.N. Vasilieva, S.M. Zyryanov, M.R. Baklanov The low-k film damage during resist plasma processing is mainly caused by O and H atoms. Low-k surface modification via plasma pretreatment is capable to reduce the atom influence and therefore to minimize the damage. The effect of He plasma pretreatment both on low-k surface modification and interaction with O and H atoms was studied for 3 types of low-k SiOCH films: BDIIx, ELK 2.5, ELK 2.3 (porosity: 24, 24, 33{\%}, pore radius: 0.8, 0.8, 1 nm). The influence of ions, VUV radiation and metastables in He low-pressure (20 mTorr) SWD 81 MHz discharge was separately investigated. The O and H surface loss probabilities were measured in the far afterglow of the high-pressure (10 Torr) 13.56 MHz discharge. All changes occurring with low-k surface after treatment in both discharges were analyzed by FTIR spectroscopy. The phenomenological model, including recombination and reactions of O and H atoms on low-k surface, was used to analyze the obtained results. [Preview Abstract] |
Thursday, October 22, 2009 2:45PM - 3:00PM |
TR1.00005: Investigation of the etching mechanisms of Ar/Cl$_{2}$/O$_{2}$ inductively coupled plasmas on silicon by means of modelling and experiments Stefan Tinck In this topic, the etching behaviour of Cl$_{2}$/O$_{2}$/Ar inductively coupled plasmas on a silicon substrate, as used in shallow trench isolation for the production of electronic devices, is investigated by means of modelling and experiments. A hybrid plasma model is applied to calculate the plasma characteristics in the reactor chamber and two additional Monte Carlo simulations are performed to predict the fluxes, angles and energy of the plasma species bombarding the silicon substrate, as well as the resulting surface processes such as etching and deposition. Experimentally, it is found that when the fraction of oxygen in the gas mixture of the plasma is too high, the deposition of oxygen species becomes superior to the etching of silicon by chlorine species, resulting in an etch rate close to zero. In the surface simulations, special attention is paid to the potential distribution and the composition of the surface layers during etching or deposition to provide a better insight in these silicon surface processes. [Preview Abstract] |
Thursday, October 22, 2009 3:00PM - 3:30PM |
TR1.00006: Development and validation of a C5F8/Ar/O2 mixture chemistry model using quantum chemistry methods Invited Speaker: Understanding the electron impact processes in c-C5F8 plasmas is of importance to low dielectric constant thin film deposition and etch process development. As much of radicals and excited states in c-C5F8 plasma chemistry are inaccessible by experiment, we used quantum chemistry methods, coupled with a zero-dimensional plasma kinetics model to develop an electron impact cross-section set and its associated plasma chemistry mechanism. The calculations were augmented with quadrupole mass spectrometry and actinometry measurements on a 200mm capacitively coupled plasma source. Predicted etch rates are in good agreement with experimental data examining large substrate RF bias and low pressure. The primary loss process for c-C5F8 is electron impact dissociation into isomers of C5F7 via excitation to the triplet state of c-C5F8. Electron impact dissociation of C5F7 isomers leads finally to the production of C5F5 (an isomer with two conjugate pi bonds) and C5F6 (an isomer with two pi bonds and a folded ring structure). These and other isomers characterized by a plurality of pi bonds and certain ring structures are very stable under electron impact. These ``terminal" species are important from the perspective of polymer deposition. The etch precursor, atomic fluorine, is primarily produced from electron impact dissociation of the feed-gas and its degradation products. CF is produced from dissociation of CF2. CF3 is produced primarily from the walls. [Preview Abstract] |
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