In advanced nanoelectronics transistor structures, strain can be used as a concept to enhance the mobility of electrons (or holes) in the channel region and thereby increasing the channel conductivity and overall device performance. At the same time, novel transistor channel materials such as compound III-V semiconductors are introduced in 3D integration schemes. Strain and composition measurements for process optimization on these structures generally require TEM-based techniques such as nano-beam diffraction (NBD) and convergent beam electron diffraction (CBED), or X-ray techniques like high-resolution X-ray diffraction (HRXRD). The main drawback of these approaches is that the measurement is destructive in nature and/or requires lengthy or large-scale integration using complex metrology tools. In this topic, the use and optimization of advanced micro-Raman spectroscopy is investigated for measuring the local stress and composition in next-generation (nm-scale) semiconductor architectures. As a dramatic enhancement of the Raman response occurs when sampling such nm-sized features, a concept termed nano-focused Raman has been developed which can be employed for compositional and strain measurements in group IV and III-V finFETs, nanowires and multistacks. Combined with oil immersion techniques for the light coupling, multi tensor strain values can be obtained.
The focus of the topic will to optimize and quantify this approach and to build on a fundamental understanding of the active Raman modes in the materials of interest, their dependency on strain and composition in nanoscale semiconductors and the role of the light coupling process on the spectral response. Through cross-validation with other characterization tools from the imec metrology portfolio such as Nanobeam diffraction (TEM) and HRXRD, a non-destructive and quantitative metrology concept will be developed that is of paramount importance for future CMOS technology. With the emergence of wafer scale Raman systems, this PhD research is of high industrial relevance as it paves the way for their application for stress and composition measurements at the nanoscale in nanoscale systems.
Required background: physics, engineering
Type of work: 60% experimental, 40% interpretation and modelling
Supervisors: Wilfried Vandervorst, Ingrid De Wolf
Daily advisor: Thomas Nuytten
The reference code for this PhD position is STS1712-53. Mention this reference code on your application form.