Material characterization of semiconducting oxides

Dynamic Random-Access Memory (DRAM) is a semiconductor memory in which each bit of data in each cell is can be randomly accessed by semiconducting transistors. A new generation of DRAM with alternative types of transistors are under development. Instead of silicon, semiconducting oxide (SCO) is explored to enable an extremely low refresh frequency, data integrity and low power consumption. Conformal and low temperature deposition of SCO’s enables the further miniaturization of DRAM technology and extends the application of this material to other type of new devices.

The electrical properties of SCO originate from their wide band gap, their exclusively n-type behavior and their relative high electron mobility that remains largely preserved in the amorphous phase. n-Type doping occurs from intrinsic ‘defects’ and by incorporation of hydrogen which are both poorly understood. Moreover, there is a lack of understanding on the relation between atomic arrangements in the film to the doping concentrations and defect states that control electronic transport. By careful optimization of deposition processes the ideal SCO films are obtained enabling a detailed characterization of the atomic structure and defects with state-of-the-art techniques.

This PhD project starts with on the experimental exploration of InGaZnO₄ (IGZO) films with a spinel crystal structure. This crystal phase is considered as a prototype for the amorphous phase, currently the SCO material of reference. The general approach is to optimize the poly-crystalline structure to a mono-crystalline film with low defectivity. The atomic arrangement of those optimized structures will be investigated in detail and compared to the references. This requires elaborated sample preparation, experimental and dedicated characterization methods based on Rutherford Back Scattering (RBS), X-ray diffraction (XRD), Tunnel electron microscopy (TEM) and other techniques available at imec. Also, submissions to sophisticated beam-line characterizations abroad are considered in this project.

This PhD project is part of an industrially relevant research program for which new materials are pre-screened for future technology nodes, extending leading-edge technologies. You will obtain new fundamental insight and expertise on the behavior of SCO’s in order to predict and test possible improvements on material and device level.  You will work together with a team of deposition, material science and characterization experts within an international environment.