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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ion energy distributions (IEDs) striking surfaces in rf glow discharges are important in the context of plasma etching during the fabrication of microelectronics devices. In discharges sustained in molecular gases or multicomponent gas mixtures, the shape of the IED and the relative magnitudes of the ion fluxes are sensitive to ion–molecule collisions which occur in the presheath and sheath. Ions which collisionlessly traverse the sheaths or suffer only elastic collisions arrive at the substrate with a measurably different IED than do ions which undergo inelastic collisions. In this article we present measurements and results from parametric calculations of IEDs incident on the grounded electrode of a rf glow discharge sustained in a He/N2 gas mixture while using a Gaseous Electronics Conference Reference Cell (33.3 Pa, 13.56 MHz). We found that the shape of the IEDs for N+3 and N+4 provide evidence for inelastic ion–molecule reactions which have threshold energies of 〈10 eV. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7419-7424 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fluorocarbon impurities are known to have deleterious effects on the operation of excimer lasers; however, the sensitivity limits are poorly known. Absorption at 248.9 nm in an e-beam-pumped KrF laser has been attributed to CF2, produced by plasma fragmentation of precursor molecules such as CF4. In this paper, the effects of CF4 impurities on the gain of an electron-beam-excited KrF laser are investigated theoretically. It is found that the density of KrF(B) significantly decreases and absorption increases when the CF4 concentration exceeds 0.03%. The decrease in the density of KrF(B) is dominantly the result of the interception of precursors to forming the upper laser level, as opposed to direct quenching.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 2106-2114 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dust particle transport in low-temperature plasmas has recently received considerable attention due to the desire to minimize contamination of wafers during plasma processing of microelectronics devices. Laser light scattering observations of dust particles near wafers in reactive-ion-etching (RIE) radio frequency (rf) discharges have revealed clouds which display collective behavior. These observations have motivated experimental studies of the Coulomb liquid and solid properties of these systems. In this paper, we present results from a two-dimensional model for dust particle transport in RIE rf discharges in which we include particle-particle Coulomb interactions. We predict the formation of Coulomb liquids and solids. These predictions are based both on values of Γ〉2 (liquid) and Γ〉170 (solid), where Γ is the ratio of electrostatic potential energy to thermal energy, and on crystal-like structure in the pair correlation function. We find that Coulomb liquids and solids composed of trapped dust particles in RIE discharges are preferentially formed with increasing gas pressure, decreasing particle size, and decreasing rf power. We also observe the ejection of particles from dust crystals which completely fill trapping sites, as well as lattice disordering followed by annealing and refreezing. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3716-3718 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Contamination of wafers by particles in plasma processing reactors is a continuing problem affecting yields of microelectronic devices. In this letter, we report on a computational study of particle contamination of wafers in a high plasma density inductively coupled plasma (ICP) reactor. When operating with an unbiased substrate, particles readily contaminate the wafer due to high ion fluxes which produce large ion-drag forces. Biasing the substrate with a radio frequency (rf) voltage counteracts the ion-drag forces by increasing the opposing electrostatic forces in the sheath, thereby shielding the wafer from incoming particles. We have found three regimes of particle contamination for different ICP powers and rf biases. At high rf biases and low ICP powers, particles trap at the edge of the sheath. At low rf bias and high ICP power, ion drag forces dominate, particles do not trap, and wafer contamination is problematic. At intermediate powers and biases, particles quasitrap, leading to moderate particle contamination. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 1996-06-24
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 6
    Publication Date: 1991-06-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 7
    Publication Date: 1997-09-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 8
    Publication Date: 1996-01-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 9
    Publication Date: 2019-07-18
    Description: Semiconductor device profiles are determined by the characteristics of both etching and deposition processes. In particular, a highly anisotropic etch is required to achieve vertical sidewalls. However, etching is comprised of both anisotropic and isotropic components, due to ion and neutral fluxes, respectively. In Ar/Cl2 plasmas, for example, neutral chlorine reacts with the Si surfaces to form silicon chlorides. These compounds are then removed by the impinging ion fluxes. Hence the directionality of the ions (and thus the ion angular distribution function, or IAD), as well as the relative fluxes of neutrals and ions determines the amount of undercutting. One method of modeling device profile evolution is to simulate the moving solid-gas interface between the semiconductor and the plasma as a string of nodes. The velocity of each node is calculated and then the nodes are advanced accordingly. Although this technique appears to be relatively straightforward, extensive looping schemes are required at the profile corners. An alternate method is to use level set theory, which involves embedding the location of the interface in a field variable. The normal speed is calculated at each mesh point, and the field variable is updated. The profile comers are more accurately modeled as the need for looping algorithms is eliminated. The model we have developed is a 2-D Level Set Profile Evolution Simulation (LSPES). The LSPES calculates etch rates of a substrate in low pressure plasmas due to the incident ion and neutral fluxes. For a Si substrate in an Ar/C12 gas mixture, for example, the predictions of the LSPES are identical to those from a string evolution model for high neutral fluxes and two different ion angular distributions.(2) In the figure shown, the relative neutral to ion flux in the bulk plasma is 100 to 1. For a moderately isotropic ion angular distribution function as shown in the cases in the left hand column, both the LSPES (top row) and rude's string method (bottom row) predict tapered profiles. The LSPES uses an AD with a FWHM = 13.5 degrees, and rude's model uses a ratio of sheath voltage to ion temperature of 50. The more anisotropic IADs produce profiles with more vertical sidewalls and a wider bottom surface, as shown in the right hand column. Here, the LSPES has an AD with a FWHM = 2 degrees, and rude's model uses a ratio of 500 of sheath voltage to ion temperature. The agreement between the LSPES and rude's model is excellent in both cases. We will present etching profiles generated by the LSPES, including calculations of the re-emitted fluxes of both neutrals and ions off of the profile walls. In addition, we will show the effect of geometric structures (overhangs, etc.) on the etching profiles. Other physical aspects, such as surface diffusion, will also be included in the model.
    Keywords: Plasma Physics
    Type: 4th International Workshop on Advanced Plasma Tool and Process Engineering; May 26, 1998 - May 27, 1998; Millbrae, CA; United States
    Format: text
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  • 10
    Publication Date: 2019-07-19
    Description: In 2012, the entry vehicle for the Mars Science Laboratory (MSL) mission was the largest and heaviest vehicle flown to another planet, designed to be able to withstand the largest heat fluxes in the Martian atmosphere ever attempted. The heatshield material that had been successfully used for all previous Mars missions had been baselined in the design, but during the development and qualification testing demonstrated catastrophic and unexplained failures. With only 10 months remaining before the original launch date, the TPS team led by NASA Ames designed and implemented a first-ever tiled, ablative heatshield. Highlights from MSL of the testing difficulties and innovations required to execute a new heatshield design will be presented, along with a sneak peak of the Mars 2020 mission.
    Keywords: Lunar and Planetary Science and Exploration
    Type: ARC-E-DAA-TN52600 , Semi-Therm 34; Mar 19, 2018 - Mar 23, 2018; San Jose, CA; United States
    Format: application/pdf
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