A New Class of Mechanical Fatigue in Silicon

Sanjit Bhowmick1 and Brian lawn2

 

Ceramics Division, Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 - 8520

 

It has long been known that bulk silicon is immune from fatigue.  We present evidence demonstrating severe fatigue in macroscale cracks produced in cyclic loading of (100) single-crystal silicon with a sphere indenter. The periodic indentation field generates ring cracks around the contact, which proliferate with continued cycling.  Copious debris in the form of slabs and particulates is ejected from within the crack walls onto the specimen surface.  The key ingredient is a component of shear stress acting on the cracks during contraction and expansion of the contact circle.   Continued ejection leads ultimately to large-scale surface removal.  The fatigue damage progressively degrades the material strength, the more rapidly at higher contact load.  Implications concerning the function of silicon devices, including MEMS, will be briefly presented.

 

Category: Materials

 

1. Author: Sanjit Bhowmick

Room No: A349, Building: 223

Phone: x4539, Fax: x5334

Email: sanjit.bhowmick@nist.gov

Division: Ceramics, MSEL (8520)

Not Sigma Xi member

 

2. Mentor: Brian Lawn

Room No: A347, Building: 223

Phone: x5775, Fax: x5334

Email: brian.lawn@nist.gov

Division: Ceramics, MSEL (8520)

Not Sigma Xi member