Single Electron Transistor on FD SOI for Spin Qubits Sensing

This Master Thesis describes the design and the fabrication of a Single Electron Transistor (SET) on a FD SOI (Fully Depleted Silicon-on-Insulator) substrate. The SET is an ultra-sensitive sensor capable of measuring single charge transitions in the environment, which makes it the best candidate for the readout of a spin qubit state. Moreover, the SET illustrated in this Thesis is based on the silicon quantum dots technology and this aspect makes easier its integration with spin qubits. Such platforms already exist and will be introduced during the dissertation, but most of them are fabricated on bulk silicon and not on SOI. Under this light, the aim of this work is to validate a robust process flow to fabricate a quantum dot on FD SOI wafers with the function of SET, the leading device for the integration of more complicated devices such as spin qubits in silicon quantum dots. This is the final goal of the Electron Spin Qubits project inside the NCCR spin network (1), a project where this Master Thesis constitutes only the very first part. A lot of emphasis is put on the characterization of the gate oxide used to create the SiMOS structure of the quantum dot to find the best fabrication recipe for a very high-quality oxide, which is the main effective mean for the reduction of the charge noise, one of the most detrimental parameters in single electron electronics. The results of this study allow to obtain the best fabrication recipe. Furthermore, another focal aspect of the dissertation is constituted by the realization of ohmic contacts on the UTB (Ultra-Thin Body) FD SOI wafers, from the TCAD simulations for the dopants implantation to the fabrication of the contacts and their characterization. The Thesis is entirely carried out at Nanolab of Prof. Adrian Mihai Ionescu (2), whereas the nanofabrication process inside the CMi cleanrooms (3). Both are located at the École Polytechnique Fédérale de Lausanne. (1) https://www.nccr-spin.ch/ (2) https://www.epfl.ch/labs/nanolab/ (3) https://www.epfl.ch/research/facilities/cmi/