Characterization of in-plane strain relaxation in strained layers using a newly developed plane nano-beam electron diffraction (plane-NBD) method

Abstract

A uniaxial strained channel is attractive for enhancing MOSFET performance. In order to develop the performance of uniaxially strained channel devices, strain evaluation within the channel is important, because the control of in-plane strain variation along gate length and gate width directions is needed to improve MOSFET performance. In order to directly evaluate an in-plane strain variation within a strained channel with a very small lateral resolution, we have newly developed the plane-NBD method, which is a combination of the TEM technique and NBD measurement. A characteristic of plane-NBD is that it enables separation of the in-plane strain variation with two axes with a lateral resolution of 10 nm. This method was successively applied to the strain characterization of biaxially compressive-strained SGOI layers. As a result, the plane-NBD has revealed that strain relaxation within the SGOI layers after isolation processing was dependent on the mesa size. These results have demonstrated that the plane-NBD method is a unique and effective technique for evaluating in-plane strain distribution within small and thin strained layers of a sub-100 nm size.