Molybdenum Contamination in Silicon: Detection and Impact on Device Performances

Codegoni, Davide; Polignano, M. L.; Caputo, D.; Riva, Andrea Macedo; Blot, Emmanuel; Coulon, David; Maillot, Pauline; Pic, Nicolas

doi:10.4028/www.scientific.net/ssp.145-146.123

Cited by 15 publications

(10 citation statements)

References 2 publications

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“…Molybdenum (Mo) contamination in silicon epitaxial layers is reported to be due to contaminated valves in the gas supply system, 1 stainless steel gas delivery lines, 2,3 HCl susceptor etching, 4,5 formation of shallow junctions using BF 2 ion implantation 6 and contaminated cleaning benches. 7 In p-type silicon, the donor level (Mo-d) is reported by several groups to be E v +0.28 ± 0.01 eV. [8][9][10] This energy level is consistent with the theoretically calculated Mo-d level in silicon.…”

supporting

confidence: 80%

“…When E a is plotted versus the square root of the electric field (F 1/2 ), the slope from our measurements were calculated to be 4.5 × 10 −5 eV/(V/cm) 1/2 , while that of the predicted slope for a donor level is 2.2 × 10 −4 eV/(V/cm) 1/2 as shown in (7). Our calculated slope is almost one order of magnitude lower than that for a trap that would show the Poole-Frenkel effect.…”

Section: Resultsmentioning

confidence: 99%

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Detection of a Molybdenum Acceptor Level in N-Type Silicon

Cox

2014

ECS J. Solid State Sci. Technol.

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The detection of Mo in n-type Si has been reported in only a few references. An unidentified peak was detected in an n-type epitaxial layer by DLTS with an activation energy and capture cross-section of 0.255 eV and 3.5 × 10 −16 cm 2 , respectively. These results were consistent with measurements of n-type silicon implanted with Mo. A p-type epitaxial wafer was exposed to the same epitaxial growth environment resulting in the detection of the Mo-d level, thus confirming the Mo contamination. The change in the enthalpy of the capture of electrons into the unidentified level was 14 meV resulting in the majority carrier capture cross-section being determined to be 1.2 × 10 −16 cm 2 assuming a multi-phonon process. Using the activation energy and enthalpy change of capture cross-section data, the change in Gibbs free energy as a function of temperature was calculated to be E c -0.269 eV. Poole-Frenkel effect measurements determined the deep level to be an acceptor-like state. The total change in entropy was determined to be 1k, the first reported total entropy change for an acceptor level of a 4d transition metal. The measured enthalpy energy was in reasonable agreement with the reported theoretical calculation of a substitution Mo-a deep level.

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supporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Detection of a Molybdenum Acceptor Level in N-Type Silicon

Cox

2014

ECS J. Solid State Sci. Technol.

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“…In addition to the most common and most studied contaminants (e.g., iron and copper ) new elements were introduced a few years ago into the fabrication process, for instance tellurium for phase change memory devices . The detrimental impact of some slow diffuser contaminants (molybdenum and tungsten) was also pointed out . Finally, organic contamination is known to degrade the gate oxide integrity (GOI) .…”

Section: Introductionmentioning

confidence: 99%

A comparative analysis of different measurement techniques to monitor metal and organic contamination in silicon device processing

Polignano

Codegoni

Grasso

et al. 2015

Phys. Status Solidi A

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A few key techniques for the analysis of contamination in silicon are compared for their ability to detect different impurities. Both metal and organic contamination is included in this study. In addition, common contaminants and elements recently introduced in the fabrication process are considered. For what concerns metal contamination, it is shown that different approaches are required depending on the in‐depth distribution of the contaminant and hence on its diffusivity. Copper, iron, molybdenum, and tellurium are chosen as examples of contaminants with different diffusivity and solubility properties. Total reflection X‐ray fluorescence (TXRF), recombination and generation lifetime measurement techniques, deep level transient spectroscopy (DLTS) and capacitance versus voltage measurements are compared. The detection of slow diffusers is found to be very critical, because a very low dose may result in a non‐negligible concentration in the device region. As a consequence, the sensitivity per unit area required for these elements is difficult to reach with surface techniques such as TXRF. On the other hand, very fast diffusers such as copper can hardly be revealed in the solid solution in silicon. Copper in silicon can be revealed at the oxide–silicon interface by TOF‐SIMS measurements, or by surface generation velocity measurements with the Zerbst method. For what concerns organic contamination, surface recombination velocity and gate oxide integrity tests were compared. The most relevant effects of organic contamination were observed by electrical stress of the oxide. Indeed, the fraction of capacitors with degraded breakdown voltage increased dramatically in wafers with intentional organic contamination.

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“…It is well-known that molybdenum and tungsten contamination have detrimental impact on device performances. [1][2][3] As these contaminants are slow diffusers in silicon, [4][5][6] even a small amount per unit area results in a significant concentration in the near-surface silicon volume. Therefore, this sort of contamination can be difficult to catch by surface techniques and still be harmful for devices.…”

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Analysis of Near-Surface Metal Contamination by Photoluminescence Measurements

Polignano

Galbiati

Mica

et al. 2018

ECS J. Solid State Sci. Technol.

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In this work, molybdenum and tungsten-implanted wafers are analyzed by an innovative technique based upon photoluminescence measurements, with the aim to assess the ability of this technique to detect metal contamination in the near-surface region. Surface Photovoltage (SPV) measurements of carrier diffusion length are compared to the results of photoluminescence measurements. It is shown that molybdenum and tungsten contamination are easily detected by photoluminescence intensity measurements down to about 10 10 cm −2 contaminant dose. Vice versa, SPV has limited sensitivity to these elements (≥5 • 10 10 cm −2 ), because of their low diffusivity. Therefore, photoluminescence intensity measurement can be a valid alternative to conventional carrier diffusion length measurements for monitoring slow diffuser contamination.

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Molybdenum Contamination in Silicon: Detection and Impact on Device Performances

Abstract: In this paper, a case of molybdenum contamination from wet cleaning is discussed, and various techniques are compared for their ability to detect molybdenum. In addition, the impact of this sort of contamination on the electrical results of a bipolar device is studied.

Cited by 15 publications

References 2 publications

Detection of a Molybdenum Acceptor Level in N-Type Silicon

Detection of a Molybdenum Acceptor Level in N-Type Silicon

A comparative analysis of different measurement techniques to monitor metal and organic contamination in silicon device processing

Analysis of Near-Surface Metal Contamination by Photoluminescence Measurements

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