Copper in silicon n+-p junctions

Böhm, Roger; Klose, H.

doi:10.1002/pssa.2210090259

Cited by 7 publications

(5 citation statements)

References 11 publications

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“…p-n Junctions.-To the best of our knowledge, the first studies of the impact of Cu contamination on electrical properties of Schottky diodes were performed in the 1960s and 1970s by Goetzberger et al, 124 Busta et al, 125 Bohm et al, 126 and Hamaker et al, 127 among others. They observed a substantial increase in the leakage current of p-n junctions fabricated on intentionally contaminated Si wafers.…”

Section: Impact Of Copper On Devicesmentioning

confidence: 99%

Physics of Copper in Silicon

Istratov

Weber

2002

J. Electrochem. Soc.

366

221

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This article reviews the progress made in the studies of copper in silicon over the last several years and puts forward a comprehensive model of the behavior of copper in silicon. Technical aspects of this model are discussed in detail. It is shown that many important aspects of the behavior of copper in silicon are not shared with the other 3d transition metals. The positive charge state of interstitial copper makes its defect reactions Fermi-level-dependent, and results in a noticeable difference in the out-diffusion and precipitation behavior of copper in n-Si and p-Si. The extremely high diffusivity of copper in silicon, which is a consequence of the small ionic radius of copper and its relatively weak interaction with the silicon lattice, makes it highly mobile at room temperature and impacts the stability of copper complexes. Large lattice strains and electrostatic effects in p-Si make the formation of copper-silicide precipitates in the bulk energetically unfavorable, unless the chemical driving force for precipitation is high enough to overcome the nucleation and precipitation barrier. Literature data on the effect of copper on minority carrier lifetime and device yield are analyzed using our improved understanding of the physics of copper in silicon. Finally, the impact of the physics of copper in silicon on the development and characterization of copper diffusion barriers is discussed. © 2001 The Electrochemical Society. All rights reserved.

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Section: Impact Of Copper On Devicesmentioning

confidence: 99%

Physics of Copper in Silicon

Istratov

Weber

2002

J. Electrochem. Soc.

366

221

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show abstract

“…Copper contamination in Si devices with a p‐n junction has been shown to lead to an increase in leakage current . Istratov et al suggested that the leakage current at p‐n junctions increases through the formation of Cu precipitates in the junction area, most likely starting from the n‐type side of the junction, where Cu complex formation is favoured .…”

Section: Challenges For Copper‐plated Silicon Solar Cellsmentioning

confidence: 99%

Challenges facing copper‐plated metallisation for silicon photovoltaics: Insights from integrated circuit technology development

Lennon

Colwell

Rodbell

2018

Progress in Photovoltaics

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Copper‐plated interconnects were widely adopted for volume manufacture of integrated circuits after more than a decade of intensive research to demonstrate that use of Cu would not impact device reliability. However, although Cu‐plated metallisation promises significantly reduced costs for Si photovoltaics, its adoption in manufacturing has not gained the same traction. This review identifies some key challenges facing the introduction of Cu‐plated metallisation for Si photovoltaics. These include the following: (1) increased carrier recombination due to the use of Cu for metal contact formation; (2) reduced module reliability due to adhesion or contact integrity failures; and (3) limited availability of cost‐effective processes and equipment for metal plating. For integrated circuits, Cu's low electrical resistance and high resistance to electromigration provided an impetus for the large investment in process development that was required to realise Cu‐plated interconnects. However, the technical advantages of using Cu for Si solar cell contacts are not as compelling, as solar cells can tolerate larger feature sizes thus reducing the criticality of the contact metal's conductivity and electromigration properties. Additionally, for Si photovoltaics, low cost is paramount, and new challenges arise from the need for modules to absorb light and operate in the field for 25+ years in diverse outdoor climates. However, with the scale of Si photovoltaic manufacturing expected to increase dramatically in the next decade, the use of large quantities of silver for cell metallisation will provide an incentive to address reliability concerns regarding the use of Cu for Si photovoltaic metallisation.

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“…Finally, our results indicate that Cu Si and related complexes induce gap states, and that if these defects are present in sufficient concentrations they can cause leakage current, increasing the tunneling probability of electrons from filled impurity induced states to empty states in the conduction band in Si devices. Note that the Cu-related defects are not the only or the main source of leakage current observed in Si devices, since their concentration are relatively low in most devices that do not use copper as contacts [2][3][4][5]. The different behavior of Cu in p-and n-Si as suggested previously [12,15], can be attributed to the fact that Cu i is stable in +1 charge state and tends to form complexes, such as Cu Si -Cu i and Cu Si -H i , that are more stable in n-Si than in p-Si and Cu Si -3Cu i which is more stable in p-Si than in n-Si .…”

Section: Si and H +mentioning

confidence: 99%

“…Copper is a common impurity in silicon, often present in the processing environment of Si wafers [1]. It has long been known that the presence of Cu in Si-based p-n junction leads to increase in leakage current [2][3][4][5]. It has also been reported that Cu may cause breakdown of the gate silicon oxide [6,7], resulting in leakage current in MOS capacitors.…”

Section: Introductionmentioning

confidence: 99%

Hybrid-Functional Calculations of the Copper Impurity in Silicon

2017

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We calculate formation energies and transition levels for copper-related defects in silicon using the screened hybrid functional of Heyd, Scuseria, and Enzernhof HSE06. We considered Cu siting on interstitial sites (Cu i), substitutional site (Cu Si), Cu Si-Cu i pair, a complex formed of substitutional Cu and intersititial hydrogen (Cu Si-H i) and a complex formed of a substitutional Cu and three interstitial Cu (Cu Si-3Cu i). We find that Cu i is a fast diffuser, with migration barrier of only 0.19 eV, in good agreement with experimental values. Cu i is a shallow donor and its formation energy is lower than that of Cu Si for all Fermi level positions in the band gap. Cu Si , on the other hand, induce levels in the gap, which are related to the occupation of antibonding states originated from the coupling between the Cu 3d states (t (d) 2), resonant in the valence band, and the vacancy-induced gap states (t (p) 2). The stable charge states of Cu Si in the gap are +1, 0,-1, and-2. The transition levels of Cu Si-Cu i and Cu Si-H i are closely related to the levels of isolated Cu Si : a donor level (+/0) near the valence band, an acceptor level near mid gap, and a double acceptor level in the upper part of the gap. The calculated transition levels are in good agreement with experimental results, and the formation energies explain the observed solubility.

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Copper in silicon n+-p junctions

Cited by 7 publications

References 11 publications

Physics of Copper in Silicon

Physics of Copper in Silicon

Challenges facing copper‐plated metallisation for silicon photovoltaics: Insights from integrated circuit technology development

Hybrid-Functional Calculations of the Copper Impurity in Silicon

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