On the Feasibility of a New Technique for Applying and Sensing a Pre-Strain State for Strain Engineering

This paper reports a successful design, fabrication, and characterization of a new microstructure, that utilizes piezoresistivity, for locally applying a pre-strain state onto silicon substrates and measuring it. This technique allows for applying tensile and compressive transverse local strain for the first time, using the same stressing layer rather than using nitride capping for tensile or silicon germanium for compressive strain. It is well-known that the only strain that enhances both electron and hole mobility simultaneously is the transverse uniaxial strain. Moreover, the utilized sensing structure evaluates directly the actual stress transmitted to the substrate. Therefore, it is a valuable tool for strain engineering applications, where modulating and determining the pre-strain state onto the silicon at infinitesimal areas are required. The proposed structure composed of highly compressive plasma enhanced chemical deposition nitride layer that was patterned in a way allowing for inducing both local tensile and compressive uniaxial pre-strain onto the silicon. Using this method, the stress transferred to silicon is around 40 to 150 MPa, however the developed sensing structure was capable of detecting it for both tensile and compressive stresses.