Effect of crystallographic orientation on phase transformations during indentation of silicon
- PDF / 1,223,242 Bytes
- 12 Pages / 584.957 x 782.986 pts Page_size
- 10 Downloads / 265 Views
S.J. Stranick Surface and Microanalysis Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899
D.J. Morris, M.D. Vaudin, and R.F. Cook Ceramics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (Received 6 August 2008; accepted 25 November 2008)
In a statistical nanoindentation study using a spherical probe, the effect of crystallographic orientation on the phase transformation of silicon (Si) was investigated. The occurrence and the contact pressures at which events associated with phase transformation occur, for an indentation force range from 20 to 200 mN, were analyzed and compared for the orientations Si(001), Si(110), and Si(111). It was found that plastic deformation combined with phase transformation during loading was initiated at lower forces (contact pressures) for Si(110) and Si(111) than for Si(001). Also, the contact pressure at which the phase transformation occurred during unloading was strongly influenced by the crystallographic orientation, with up to 38% greater values for Si(110) and Si(111) compared to Si(001). Mapping the residual stress field around indentations by confocal Raman microscopy revealed significant differences in the stress pattern for the three orientations.
I. INTRODUCTION
Single crystal silicon (Si) is one of the principal materials used for solid-state electronics, microelectromechanical systems (MEMS), infrared optical, and photovoltaic technologies. In recent decades, various solid phases of Si have been observed as a result of mechanical loading of the material.1,2 Knowledge of the nature and occurrence of these Si phases is essential, as the performance of Si-based devices depends on the Si properties, which are strongly influenced by phase transformations. For example, Si changes its electrical characteristics from semiconductor-like to metallic under mechanical loading.3 The entire concept of ductileregime (DR) machining, an ultraprecision machining process applied by the semiconductor industry, is based on the transformation from the brittle (Si-I) to the ductile (Si-II) phase.4 Phase transformations have a significant impact on the tribological performance of Si.5 The lower etching rates of high-pressure polycrystalline phases created through phase transformation are exploited in a recent new maskless patterning process.6 Although earlier works (reviewed in Ref. 7) indicate a dependence of the transformation pressures on the a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0122
1172
http://journals.cambridge.org
crystallographic orientation (in other words, a dependence on the loading direction), the Si(001) orientation (and hence loading along Si[001]) has been studied almost exclusively, as it is the most common orientation used in the semiconductor microelectronics industry. In strain engineering, however, tensile or compressive stresses are induced perpendicular to the [001] direction to enhance transistor performance through enhan
Data Loading...
