Fracture strength of micro- and nano-scale silicon components

Abstract

Silicon devices are ubiquitous in many micro- and nano-scale technological applications, most notably microelectronics and microelectromechanical systems (MEMS). Despite their widespread usage, however, issues related to uncertain mechanical reliability remain a major factor inhibiting the further advancement of device commercialization. In particular, reliability issues related to the fracture of MEMS components have become increasingly important given continued reductions in critical feature sizes coupled with recent escalations in both MEMS device actuation forces and harsh usage conditions. In this review, the fracture strength of micro- and nano-scale silicon components in the context of MEMS is considered. An overview of the crystal structure and elastic and fracture properties of both single-crystal silicon (SCS) and polycrystalline silicon (polysilicon) is presented. Experimental methods for the deposition of SCS and polysilicon films, fabrication of fracture-strength test components, and analysis of strength data are also summarized. SCS and polysilicon fracture strength results as a function of processing conditions, component size and geometry, and test temperature, environment, and loading rate are then surveyed and analyzed to form overarching processing-structure-property-performance relationships. Future studies are suggested to advance our current view of these relationships and their impacts on the manufacturing yield, device performance, and operational reliability of micro- and nano-scale silicon devices.

A new push‐pull sample design for microscale mode 1 fracture toughness measurements under uniaxial tension

“…Therefore, the microscale fracture toughness measurements described here achieved a high level of consistency even though not all requirements of ASTM standard E399 could be met. This is reflected also in the good correspondence of the fracture toughness reported here (1.02 MPa√m) with the range of values regarded as reliable in the literature (0.65‐1.0 MPa√m) …”

“…Micromechanical fracture measurements using several different methods resulted in room temperature fracture toughness values between 0.8 and 1.0 MPa√m . Our results are located at the upper end of the spectrum of reliable toughness measurements for Si and feature a relatively small experimental scatter; therefore, they may be regarded as in line with the existing research. Fracture surfaces imaged posttest revealed highly consistent and repeatable fracture patterns and facetted crack paths aligned with the (100) plane for both notch lengths.…”

“…Reliable fracture toughness values for cleavage of single crystal Si along (110) and (111) planes at room temperature in the literature vary from 0.65 to 1.0 MPa√m. 9,[40][41][42][43][44][45][46][47][48] Micromechanical fracture measurements using several different methods resulted in room temperature fracture toughness values between 0.8 and 1.0 MPa√m. 25,49 Our results are located at the upper end of the spectrum of reliable toughness measurements for Si 9 and feature a relatively small experimental scatter; therefore, they may be regarded as in line with the existing research.…”

“…The development of silicon (Si) microfabrication techniques in large‐scale clean room facilities has allowed fabricating and commercializing microelectromechanical (MEMS) devices . These structures require a high reliability, which motivates the mechanical characterization of their base materials.…”

“…1,[5][6][7][8] The development of silicon (Si) microfabrication techniques in large-scale clean room facilities has allowed fabricating and commercializing microelectromechanical (MEMS) devices. 9 These structures require a high reliability, which motivates the mechanical characterization of their base materials. Silicon fails in a brittle manner at room temperature; its strength is defined as the stress needed to propagate a crack through the entire sample.…”