Using STEM with quasi-parallel illumination and an automated peak-finding routine for strain analysis at the nanometre scale

Strain engineering has become an important tool to allow the semiconductor industry to meet roadmap requirements for device performance in the face of limits to device scaling. In addition, strain and/or lattice distortion through chemistry or mechanical stress, can have significant effect on mechanical, electrical and magnetic properties in a wide range of materials. Therefore, determination of strain in a processed, failed or natural sample will have ramifications in almost all fields of material science and solid state physics. Currently, only transmission electron microscopy (TEM) has proven capable of measuring such buried strains at the required spatial resolutions. This contribution presents an automated methodology to measure strain with high accuracy, high reproducibility, and high spatial resolution yet without the need for elaborate experimental setup or highly trained operator. The methodology is first put in perspective and compared to other available methodologies. Important aspects of the experimental setup are then detailed as well as the specificity of the methodology and used algorithm. Three different cases are described: SiGe multilayer, strained transistor, and indented sapphire and the strain measured discussed.