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Title: Thermal Stability of Copper–Nickel and Copper–Nickel Silicide Contacts for Crystalline Silicon

Abstract

Copper is a low-cost, low-damage alternative to Ag paste for front-side metallization of crystalline Si (c-Si) solar cells, but requires conductive diffusion barriers like Ni or NiSi. Thermal stability of these barriers during postmetallization anneal is critical for performance. In this study, we address the structural and chemical stability of Cu contacts with both Ni and NiSi barrier layers, identifying interfacial reactions responsible for their degradation. Superior thermal and chemical stability of single-phase NiSi barrier as compared to Ni is made evident by XRD, Auger, and Raman spectroscopies. Moreover, the commonly used Cu-Ni-Si contact stack does not convert to more stable Cu-NiSi-Si stack upon thermal treatment. Instead, Cu readily alloys with the Ni layer and reacts with the underlying c-Si to form Cu3Si, with no evidence for the formation of NixSi phases. Also, even the superior NiSi barrier slowly dissolves into Cu at elevated temperatures.

Authors:
 [1];  [1];  [1];  [1];  [2];  [2];  [2];  [3];  [3]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Rochester Inst. of Technology, NY (United States)
  3. Colorado School of Mines, Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
OSTI Identifier:
1479870
Report Number(s):
NREL/JA-5900-71509
Journal ID: ISSN 2574-0962
Grant/Contract Number:  
AC36-08GO28308
Resource Type:
Accepted Manuscript
Journal Name:
ACS Applied Energy Materials
Additional Journal Information:
Journal Volume: 1; Journal Issue: 6; Journal ID: ISSN 2574-0962
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; copper; metallization; nickel; nickel silicide; solar cell

Citation Formats

Nemeth, William M., Perkins, Craig, Young, David L., Stradins, Paul, Marshall, Alexander, Florent, Karine, Kurinec, Santosh K., Agarwal, Sumit, and Kale, Abhijit. Thermal Stability of Copper–Nickel and Copper–Nickel Silicide Contacts for Crystalline Silicon. United States: N. p., 2018. Web. https://doi.org/10.1021/acsaem.8b00488.
Nemeth, William M., Perkins, Craig, Young, David L., Stradins, Paul, Marshall, Alexander, Florent, Karine, Kurinec, Santosh K., Agarwal, Sumit, & Kale, Abhijit. Thermal Stability of Copper–Nickel and Copper–Nickel Silicide Contacts for Crystalline Silicon. United States. https://doi.org/10.1021/acsaem.8b00488
Nemeth, William M., Perkins, Craig, Young, David L., Stradins, Paul, Marshall, Alexander, Florent, Karine, Kurinec, Santosh K., Agarwal, Sumit, and Kale, Abhijit. Thu . "Thermal Stability of Copper–Nickel and Copper–Nickel Silicide Contacts for Crystalline Silicon". United States. https://doi.org/10.1021/acsaem.8b00488. https://www.osti.gov/servlets/purl/1479870.
@article{osti_1479870,
title = {Thermal Stability of Copper–Nickel and Copper–Nickel Silicide Contacts for Crystalline Silicon},
author = {Nemeth, William M. and Perkins, Craig and Young, David L. and Stradins, Paul and Marshall, Alexander and Florent, Karine and Kurinec, Santosh K. and Agarwal, Sumit and Kale, Abhijit},
abstractNote = {Copper is a low-cost, low-damage alternative to Ag paste for front-side metallization of crystalline Si (c-Si) solar cells, but requires conductive diffusion barriers like Ni or NiSi. Thermal stability of these barriers during postmetallization anneal is critical for performance. In this study, we address the structural and chemical stability of Cu contacts with both Ni and NiSi barrier layers, identifying interfacial reactions responsible for their degradation. Superior thermal and chemical stability of single-phase NiSi barrier as compared to Ni is made evident by XRD, Auger, and Raman spectroscopies. Moreover, the commonly used Cu-Ni-Si contact stack does not convert to more stable Cu-NiSi-Si stack upon thermal treatment. Instead, Cu readily alloys with the Ni layer and reacts with the underlying c-Si to form Cu3Si, with no evidence for the formation of NixSi phases. Also, even the superior NiSi barrier slowly dissolves into Cu at elevated temperatures.},
doi = {10.1021/acsaem.8b00488},
journal = {ACS Applied Energy Materials},
number = 6,
volume = 1,
place = {United States},
year = {2018},
month = {5}
}

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Figures / Tables:

Figure 1 Figure 1: a) Process sequence for the formation of NiSi on $c$-Si via a two-step or one-step annealing process. b) X-ray diffractograms recorded at different stages of annealing of Ni films on $c$-Si: (ⅰ) after annealing for 300 s at 250 °C, followed by etching of excess Ni in amore » piranha solution; (ⅱ) after annealing the structure in “ⅰ” for another 300 s at 450 °C; and (ⅲ) after direct annealing for 300 s at 450 °C in a one-step process. c) Raman spectra recorded at different stages of annealing of Ni films on $c$-Si: (ⅰ) after annealing for 300 s at 250 °C, followed by etching of excess Ni in a piranha solution; (ⅱ) after annealing the structure in “ⅰ” for another 300 s at 450 °C; and (ⅲ) after direct annealing for 300 s at 450 °C in a one-step process. The inset shows the temporal evolution of the Raman spectra during one-step annealing of Ni films on $c$-Si at 450 °C.« less

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