Accession Number : ADA575829


Title :   Influence of Grain Structure and Doping on the Deformation and Fracture of Polycrystalline Silicon for MEMS and NEMS


Descriptive Note : Final rept. 1 Jul 2009-31 May 2012


Corporate Author : ILLINOIS UNIV AT URBANA DEPT OF ATMOSPHERIC SCIENCES


Personal Author(s) : Chasiotis, Ioannis


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a575829.pdf


Report Date : 03 Sep 2012


Pagination or Media Count : 25


Abstract : This research program investigated the effect of microstructure and doping on the effective mode I critical stress intensity factor, K(sub IC,eff), and the tensile strength of 1- m thick films comprised of columnar or laminated polysilicon doped with different concentrations of Phosphorus. The K(sub IC,eff) was 0.8-1.2 MPa m and differed by as much as 25% for specimens with specific grain size and doping concentration. This data scatter was attributed to differences in the local material details at the location of the crack tip. The K(sub IC,eff) of columnar polysilicon was generally higher than laminated polysilicon, but the latter demonstrated smaller variability in K(sub IC,eff), due to the averaging effect of the laminate structure. The tensile strengths of undoped columnar and laminated polysilicon were 1.28 0.06 GPa and 2.28 0.15 GPa, respectively. While high doping impacted the strength of the former, it had negligible effect on the strength of the latter. It was concluded that microstructural control of failure initiation is compromised by large defects that are due to post processing, and that laminated polysilicon films do improve on the consistency and magnitude of film strength. It was also shown that the Weibull parameters derived from the larger specimens could predict the characteristic strengths of 200 times smaller specimens for different film structures and doping conditions, and vice versa.


Descriptors :   *DOPING , *FRACTURE(MECHANICS) , *GRAIN STRUCTURES(METALLURGY) , DEFORMATION , GRAIN BOUNDARIES , GRAIN SIZE , MICROELECTROMECHANICAL SYSTEMS , MICROSTRUCTURE , SILICON , TENSILE STRENGTH


Subject Categories : Crystallography
      Mechanics
      Solid State Physics


Distribution Statement : APPROVED FOR PUBLIC RELEASE