Experimental stress determination increases accuracy in microelectronics
Throughout the nanotechnology era, industrial research on submicron semiconductors, such as Complementary Metal Oxide Semiconductors (CMOS), has to confront a key challenge. This involves the minimisation of the mechanical stresses built up in the layers and substrate during processing that play a very important role in the nanoworld. The deformations caused by these stresses on the device fabrication, performance and reliability constitute a much more complicated problem than the respective one existing in the macroworld. Urged by this, the project employed a technique of X-ray microdiffraction for non-destructive analysis of the local strain in test structures with submicron spatial resolution. More specifically, this novel experimental method is used to measure local crystalline structure and deformation with X-rays with the aid of suitable hardware and software. Employing a X-ray waveguide, the provided X-ray beam is highly coherent with spatial dimensions to the order of a few tens of nanometers and with a divergence of about 1mrad. Aided by suitable equipment such as a diffractometer for running micro-diffraction experiments and specialised software, the experimental procedures provided interesting results. Thereby, from the diffraction profile the strain depth profile with lateral spatial resolution in the 100-300nm range was derived. The method may find useful applications in any kind of crystalline structure, from analysing microelectronic materials, to studying bio- and engineering materials, and in particular interface problems.
