Role of microstructure and doping on the mechanical strength and toughness of polysilicon thin films

Yagnamurthy, Sivakumar; Boyce, Brad L.; Chasiotis, Ioannis

doi:10.1109/JMEMS.2015.2410215

Title: Role of microstructure and doping on the mechanical strength and toughness of polysilicon thin films

Abstract

We investigated the role of microstructure and doping on the mechanical strength of microscale tension specimens of columnar grain and laminated polysilicon doped with different concentrations of phosphorus. The average tensile strengths of undoped columnar and laminated polysilicon specimens were 1.3 ± 0.1 and 2.45 ± 0.3 GPa, respectively. Heavy doping reduced the strength of columnar polysilicon specimens to 0.9 ± 0.1 GPa. On grounds of Weibull statistics, the experimental results from specimens with gauge sections of 1000 μm × 100 μm × 1 μm predicted quite well the tensile strength of specimens with gauge sections of 150 μm × 3.75 μm × 1 μm, and vice versa. The large difference in the mechanical strength between columnar and laminated polysilicon specimens was due to sidewall flaws in columnar polysilicon, which were introduced during reactive ion etching (RIE) and were further exacerbated by phosphorus doping. Moreover, the removal of the large defect regions at the sidewalls of columnar polysilicon specimens via ion milling increased their tensile strength by 70%-100%, approaching the strength of laminated polysilicon, which implies that the two types of polysilicon films have comparable tensile strength. Measurements of the effective mode I critical stress intensity factor, KIC,eff, also showedmore »« less

Authors:

Yagnamurthy, Sivakumar ^[1]; Boyce, Brad L. ^[2]; Chasiotis, Ioannis ^[1]

Univ. of Illinois at Urbana-Champaign, Champaign, IL (United States)
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Publication Date:: Tue Mar 24 00:00:00 EDT 2015

Research Org.:: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:: USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:: 1109313

Report Number(s):: SAND-2013-6879J
Journal ID: ISSN 1057-7157; 472177

Grant/Contract Number:: AC04-94AL85000

Resource Type:: Accepted Manuscript

Journal Name:: Journal of Microelectromechanical Systems

Additional Journal Information:: Journal Volume: 24; Journal Issue: 5; Journal ID: ISSN 1057-7157

Publisher:: IEEE

Country of Publication:: United States

Language:: English

Subject:: 42 ENGINEERING; critical stress intensity factor; Weibull; grain size; MEMS; size effects; doping; microstructure

Citation Formats


                    Yagnamurthy, Sivakumar, Boyce, Brad L., and Chasiotis, Ioannis. Role of microstructure and doping on the mechanical strength and toughness of polysilicon thin films.  United States: N. p., 2015. 
Web.  doi:10.1109/JMEMS.2015.2410215.

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                    Yagnamurthy, Sivakumar, Boyce, Brad L., & Chasiotis, Ioannis. Role of microstructure and doping on the mechanical strength and toughness of polysilicon thin films.  United States.  https://doi.org/10.1109/JMEMS.2015.2410215

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                    Yagnamurthy, Sivakumar, Boyce, Brad L., and Chasiotis, Ioannis. Tue .  
"Role of microstructure and doping on the mechanical strength and toughness of polysilicon thin films".  United States.  https://doi.org/10.1109/JMEMS.2015.2410215.  https://www.osti.gov/servlets/purl/1109313.

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@article{osti_1109313,

  title        = {Role of microstructure and doping on the mechanical strength and toughness of polysilicon thin films},

  author       = {Yagnamurthy, Sivakumar and Boyce, Brad L. and Chasiotis, Ioannis},

  abstractNote = {We investigated the role of microstructure and doping on the mechanical strength of microscale tension specimens of columnar grain and laminated polysilicon doped with different concentrations of phosphorus. The average tensile strengths of undoped columnar and laminated polysilicon specimens were 1.3 ± 0.1 and 2.45 ± 0.3 GPa, respectively. Heavy doping reduced the strength of columnar polysilicon specimens to 0.9 ± 0.1 GPa. On grounds of Weibull statistics, the experimental results from specimens with gauge sections of 1000 μm × 100 μm × 1 μm predicted quite well the tensile strength of specimens with gauge sections of 150 μm × 3.75 μm × 1 μm, and vice versa. The large difference in the mechanical strength between columnar and laminated polysilicon specimens was due to sidewall flaws in columnar polysilicon, which were introduced during reactive ion etching (RIE) and were further exacerbated by phosphorus doping. Moreover, the removal of the large defect regions at the sidewalls of columnar polysilicon specimens via ion milling increased their tensile strength by 70%-100%, approaching the strength of laminated polysilicon, which implies that the two types of polysilicon films have comparable tensile strength. Measurements of the effective mode I critical stress intensity factor, KIC,eff, also showed that all types of polysilicon films had comparable resistance to fracture. Therefore, additional processing steps to eliminate the edge flaws in RIE patterned devices could result in significantly stronger microelectromechanical system components fabricated by conventional columnar polysilicon films.},

  doi          = {10.1109/JMEMS.2015.2410215},

  journal      = {Journal of Microelectromechanical Systems},

  number       = 5,

  volume       = 24,

  place        = {United States},

  year         = {Tue Mar 24 00:00:00 EDT 2015},

  month        = {Tue Mar 24 00:00:00 EDT 2015}

}

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Works referencing / citing this record:

Effects of nano‐grain structures and surface defects on fracture of micro‐scaled polysilicon components
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Xu, Ran; Hu, Xiaozhi
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Advanced microelectromechanical systems-based nanomechanical testing: Beyond stress and strain measurements
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Bhowmick, Sanjit; Espinosa, Horacio; Jungjohann, Katherine
MRS Bulletin, Vol. 44, Issue 06
DOI: 10.1557/mrs.2019.123

Statistical Investigation of the Mechanical and Geometrical Properties of Polysilicon Films through On-Chip Tests
journal, January 2018

Mirzazadeh, Ramin; Ghisi, Aldo; Mariani, Stefano
Micromachines, Vol. 9, Issue 2
DOI: 10.3390/mi9020053

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Title: Role of microstructure and doping on the mechanical strength and toughness of polysilicon thin films

Abstract

Citation Formats

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