Quantitative study of oxygen enhancement of sputtered ion yields. I. Argon ion bombardment of a silicon surface with O2 flood

Franzreb, Klaus; Lörinčı́k, Jan; Williams, Peter W.

doi:10.1016/j.susc.2004.10.001

Cited by 55 publications

(51 citation statements)

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“…The case of silicon has been extensively studied in order to measure experimentally the variations of the ion yields with oxygen surface concentration, [2,3] and to propose a theoretical model for the mechanisms of atomic secondary ions formation. [4] Experimentally, two main problems are to be solved: the accurate measurement of the oxygen atomic concentration at the surface whatever the oxygen level used, and the reliable measurements of the (useful) ion yields enhanced by the oxygen induced matrix effects.In some remarkable previous studies under Ar + beam, oxygen atoms are introduced either by flooding oxygen near the receding surface (external source of oxygen) [2,5] or by implantation of one isotope of oxygen atoms [6] (internal source of oxygen). Williams' ' 18 O method' [2] consists in implanting an 18 O marker (for quantitative oxygen measurements of the following flooded oxygen) and then in introducing 16 O (matrix effects 'enhancer') during the analysis with a constant superficial concentration, determined by the oxygen pressure.…”

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Isotopic comparative method (ICM) for the determination of variations of the ion yields in boron‐doped silicon as a function of oxygen concentration in the 0–10 at.% range

Dupuy

Dubois

Prudon

et al. 2011

Surface & Interface Analysis

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Keywords: SIMS; matrix effects; ion yield; quantification; silicon; oxygen Since the beginning of the development of SIMS techniques, oxygen is well known to enhance the ion yield of electropositive species.[1] This 'oxygen matrix effect' is widely used, either as primary beam ions or using an oxygen leak ('oxygen flooding') near the surface of the sample, or even by combining both; oxygen modifies the near surface concentration by means of a partial or complete oxidation leading to the increase of the ionization probability, useful yield and ion yield of matrix and trace elements. The case of silicon has been extensively studied in order to measure experimentally the variations of the ion yields with oxygen surface concentration, [2,3] and to propose a theoretical model for the mechanisms of atomic secondary ions formation. [4] Experimentally, two main problems are to be solved: the accurate measurement of the oxygen atomic concentration at the surface whatever the oxygen level used, and the reliable measurements of the (useful) ion yields enhanced by the oxygen induced matrix effects.In some remarkable previous studies under Ar + beam, oxygen atoms are introduced either by flooding oxygen near the receding surface (external source of oxygen) [2,5] or by implantation of one isotope of oxygen atoms [6] (internal source of oxygen). Williams' ' 18 O method' [2] consists in implanting an 18 O marker (for quantitative oxygen measurements of the following flooded oxygen) and then in introducing 16 O (matrix effects 'enhancer') during the analysis with a constant superficial concentration, determined by the oxygen pressure. This method has been discussed and commented in e.g. [7,8,9] Wittmack's ' 16 O method' does not use any preliminary isotopic marker but in situ implantation of 16 O by the primary column of the SIMS instrument itself. The implantation profile, or at least the concentration of the maximum of the implantation peak, must be known for quantitative oxygen concentration measurements. According to how the implantation has been performed, this method is limited to oxygen concentrations lower than 35 at.%. [6] In this work, we propose a new 18 O Isotopic Comparative Method ' 18 O-ICM' to investigate the oxygen concentration dependence of secondary ion yield enhancement in the 0-10 at.% range under Ar + primary beam. This method has been previously developed to measure the variations of the ion yields of highly concentrated boron in silicon.[10] For this, a silicon sample is multiimplanted with 18 O (ICM isotopic reference) to obtain a near-flat profile with a sufficiently low concentration of oxygen to remain in dilute regime. A high dose of 16 O implantation is subsequently (or previously) performed, so that the whole profile of 16 O is contained in the near-flat 18 O region. Moreover, silicon is uniformly boron doped for investigating the dopant ion yield. The ICM allows to deduce from the knowledge of the 18 O concentration the real profile of 16 O and total oxygen concentration at the surface,

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Isotopic comparative method (ICM) for the determination of variations of the ion yields in boron‐doped silicon as a function of oxygen concentration in the 0–10 at.% range

Dupuy

Dubois

Prudon

et al. 2011

Surface & Interface Analysis

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“…This surface oxide enhanced ionization efficiency of all trace elements, and did not indicate higher concentrations near the surface. 43 The disappearance of the oxide could be taken as where the oxygen peak plateaued, which also matched with where the Cu signal stabilized (not shown). The SIMS profile in figure 9 shows that the Ag as well as other impurities were uniformly distributed throughout the thickness of the film, probably implying no interface segregation.…”

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Pulse-Plating of Copper-Silver Alloys for Interconnect Applications

Volov

Swanson

O'Brien

et al. 2012

J. Electrochem. Soc.

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The electrodeposition of Cu-Ag alloys was studied as a possible application for interconnect technology, where Cu-Ag alloys may be less susceptible to electromigration than Cu alone. The presence of chloride in state-of-the-art copper plating electrolytes limited the solubility of Ag. However, pulse-plating approach enabled a wide range of Cu-Ag alloy compositions at substantial chloride concentration levels. The deposition of Ag was driven by the displacement reactions between the metallic copper and ionic silver during the off-time. Measured alloy compositions were consistent with theoretical estimates at various electrolyte concentrations, electrode rotation speeds, pulse frequencies and duty cycles. However, organic additives decreased incorporation of Ag into the alloy. It was also discovered that CuSO 4 · 5H 2 O from a number of major chemical suppliers contained Ag as an impurity. The roughness of the films was significant when produced by pulsed plating, but was shown to be substantially reduced in the presence of a leveling agent. Additionally, the concentration of chloride in the electrolyte was shown to significantly affect surface quality of the deposited Cu-Ag thin films. With the continuing miniaturization of microelectronics, electromigration effects in copper interconnect systems are becoming a major factor in determining device lifetime and reliability.1-3 Accordingly, there is a need for interconnect materials with improved electromigration resistance, while maintaining adequate electrical resistivity. It has been shown that co-deposits of Cu with small amount of other metals (such as Ag, Sn, Co, and Mg) can potentially mitigate both electro-and stress-migration.4-8 However, the resistivity of the interconnect increases with the addition of foreign metals. The International Technology Roadmap of Semiconductors (ITRS) has set the resistivity criterion at ρ < 2.2 μ · cm, 9 only slightly above the bulk resistivity of pure copper at 1.68 μ · cm. Alloying copper with silver (ρ Ag = 1.59 μ · cm) was shown to increase the resistivity of electrochemically deposited Cu-Ag films the least when compared to other copper alloys.10 For Ag content between 0.17 and 3.2 wt% the resistivity ranges 1.8 to 3.1 μ · cm.10 For this reason Cu-Ag alloys, especially at the lower Ag weight percentages, are potential candidates for the fabrication of interconnects in microelectronic devices.Acidic copper-sulfate electrolytes containing chloride have been successfully applied for many years to the electrochemical fabrication of copper interconnects. [11][12][13] Chloride in these electrolytes is known to be one of the critical constituents enabling defect-free filling of surface features.14-20 The main challenge for depositing silver from copper-plating electrolytes, which contain about 50 ppm of chloride, is the low solubility of silver in the presence of chloride ions (the solubility product of AgCl in water at 25• C is 1.8×10 We demonstrate that the application of a pulsating current instead of a direct current permits ...

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“…It has long been known that the presence of oxygen tends to increase the secondary ion yield from metals and semiconductors [Benninghoven, 1975]. When targets containing Si are bombarded by ∼ keV Ar + in the presence of a controlled oxygen atmosphere, α Si ∼ 0.2 for SiO 4 stoichiometry, and α Si ∼ 0.01 for 40% O in the presence of a controlled oxygen atmosphere [Franzreb et al, 2004]. Since sputtering depletes oxygen from the uppermost surface and at large fluences the total yield is stoichiometric with the bulk composition, the concentration C O in the uppermost nm of the target can be significantly depleted, thereby complicating estimates of the ionization efficiencies.…”

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“…The average solar wind ion flux is Φ SW ∼ 10 7 cm −2 s −1 at 3 A.U., and the total yields obtained from the SDTrimSP simulations are Y tot ∼ 0.03 atom/ion. Based on the available data [Franzreb et al, 2004], we here take α Si = 0.005 as a conservative estimate of the ionization fraction for Si. The relative yields given in Table 4.7 are used to determine the ejected fluxes of the remaining refractory species.…”

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Radiation Effects on Airless Bodies in Space: Radiolysis, Sputtering, and Sintering in Regoliths

Schaible¹

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Quantitative study of oxygen enhancement of sputtered ion yields. I. Argon ion bombardment of a silicon surface with O2 flood

Cited by 55 publications

References 54 publications

Isotopic comparative method (ICM) for the determination of variations of the ion yields in boron‐doped silicon as a function of oxygen concentration in the 0–10 at.% range

Isotopic comparative method (ICM) for the determination of variations of the ion yields in boron‐doped silicon as a function of oxygen concentration in the 0–10 at.% range

Pulse-Plating of Copper-Silver Alloys for Interconnect Applications

Radiation Effects on Airless Bodies in Space: Radiolysis, Sputtering, and Sintering in Regoliths

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