Survey of characterization and metrology for nanoelectronics

Abstract

Advances in process technology enable high volume manufacture of integrated circuits with nano-scale transistor and interconnect technology. This fabrication capability results in the availability of a great range of nano-scale materials and structures such as nano-tubes, thin films, nano-dots, and nanowires. Many of these materials are under consideration as the material for Beyond CMOS switches. There are two themes emphasized in this paper. First, materials exhibit new phenomena such as quantum confinement at nano-scale dimensions. Measurements not only observe these phenomena, determination of the dimensions of nanoscale materials requires understanding of these phenomena. Second, simulation and modeling at nano-scale dimensions is critical to both device operation and metrology. This extended abstract reviews the materials characterization and metrology methods necessary for measuring materials properties. This abstract covers several of the many measurement methods necessary for nanoscale characterization and metrology. I. The Impact of Quantum Phenomena on Optical Metrology and X-Ray Photoelectron SpectroscopyMaterials characterization of nano-scale materials has proven the existence of quantum confinement or quantum size effects (QSE). The observation of QSE in thin metal films using X-ray Photoelectron Spectroscopy is well known to the surface science community.(1) When the thickness of metal film is small enough, electron motion is confined in one dimension.The phase accumulation model correctly describes quantization of new energy level of the free electron gas by the film thickness.(2) When a metal film is thin enough and the interface between the metal and substrate are smooth enough, the extra energy levels can be observed by XPS at room temperature.Recently, we have shown that optical methods can also observe quantum confinement in ultra-thin silicon semiconductor films. The first step in identifying changes in optical properties, especially the dielectric function, is demonstrating that the data is not due to other phenomena such as stress. We observed a blue shift in the E1 critical point of ultra-thin silicon and show that it can be attributed to quantum confinement.(3) It is important to note that energy shifts in E1 smaller than KT can be observed optically. II.. Aberration Corrected Transmission Electron MicroscopyRoutinely producing high quality images is critical to nanoscale materials characterization. It is well known that image quality in electron and optical microscopy suffers from lens aberration. Electron lens aberration in high resolution transmission electron microscopy (HRTEM) results in delocalization of critical information. For example, lattice fringes can be observed to extend beyond the actual grain boundary in poly-crystalline samples. Delocalization also obscures interfacial features. The location of the last plane of atoms at an interface is typically difficult to observe.In scanning TEM (STEM), the spatial resolution of images and the ability to determine the location of t...