Student Projects

Co‐supervisor: Fabio Bersano

Overview

This project aims to optimize key nanofabrication steps in the production of spin qubit devices in silicon. The student will receive training in our academic cleanroom and will be tasked with fine-tuning the engineering parameters of the fabrication process to enhance device quality. Prerequisites include a thorough understanding of semiconductor physics and a general knowledge of basic microfabrication techniques.

Co-supervisor: Niccolò Martinolli

Master Semester Project – Cryogenic electrical characterization of ferroelectric Si-doped HfO2

Overview

This short project aims at investigating some fundamental properties of ferroelectric Si-doped HfO2, when used as a gate oxide, from room to cryogenic temperatures. By using thin film capacitors fabricated in cleanroom as model structures, the student will perform electrical characterizations on a room temperature and a cryogenic probestation cooled with liquid helium. By employing a combination of polarization-voltage, current-voltage, and capacitance-voltage measurements at high and low frequency, the student will observe and report how the remnant polarization, coercive field, leakage current, and density of charged traps change with the temperature.

Objectives

• Understanding how ferroelectric materials work and their application in field effect transistors.
• Understanding the rationale behind the cryogenic characterization and the relevance of defects.
• Familiarizing with the techniques and equipment used.
• Finding optimal characterization conditions and conducting experiments in an accurate and thorough way.
• Analyzing and reporting results clearly and effectively.

Prerequisites

• Basic understanding of semiconductor physics and devices.
• Data analysis with Origin Pro, Matlab or Python.

Starting date

As soon as possible

Master Thesis Project – Gate integration of ferroelectric Si-doped HfO2 in cryo-electronic devices

Overview

This semester-long project aims at integrating ferroelectric Si-doped HfO2 in the gate stack of field effect transistors and understanding its impact on the device characteristics, from room to cryogenic temperature. The final goal is to explore the potentials of ferroelectric gates in the field of cryo-electronics and spin qubits architectures. The student will be given both cleanroom fabrication and characterization tasks of thin film capacitors, Hall-bars, and field effect transistors. By using well-tested fabrication processes and employing several characterization techniques, the student will observe and report how the gate stack properties change with the temperature and how the gate stack influences the underlying silicon channel, in terms of threshold, mobility and noise.

Objectives

• Understanding how ferroelectric materials work and their application in field effect transistors, cryo-electronics and quantum devices.
• Understanding the impact of the gate stack on the device, according to the desired functionality.
• Familiarizing with the techniques and equipment used.
• Fine-tuning of some fabrication processing parameters.
• Finding optimal characterization conditions and conducting experiments in an accurate and thorough way.
• Analyzing and reporting results clearly and effectively.
• Interpreting the results critically and proposing solutions to problems.

Optional opportunities (based on the student preference and the progress of other projects)

• TCAD simulations of the fabricated structures.
• Boot-up of a helium cryostat.
• Extension of the work to ferroelectric single electron transistors.
• Comparison of the results obtained on the capacitors with other techniques to investigate charged traps.

Prerequisites

• Good understanding of semiconductor physics and devices.
• Knowledge of basic microfabrication techniques.
• Data analysis with Origin Pro, Matlab or Python.
• Some experience in a research lab.

Starting date

As soon as possible

Co‐supervisor: Ali Gilani

Co‐supervisor: Igor Stolichnov

Co‐supervisor: Ali Gilani

Project requirements: basic theoretical knowledge of cleanroom fabrication and biochemistry knowledge

Main tasks: Biosensor characterization

Starting date:  As soon as possible

Recommended type of project:  Master project or internship.

Work breakdown: 10% theory, 20% fabrication, 70% characterization.

Contact person:  Ali Gilani

Co‐supervisor: Hung-wei Li

Overview

This semester-long project aims to investigate the properties and applications of ferroelectric materials through the lens of supercapacitor technology. Students will have the opportunity to delve into the fabrication and testing of various electrode designs, focusing on their effects when different polarizations are applied to ferroelectric materials. The project will utilize NiCuOx and Fe₂O₃ as active materials and tailored architectures for optimized performance.

Objectives

1. To fabricate various designs of electrodes using NiCuOx and Fe₂O₃ as active materials.
2. To test the effects of different polarizations on the ferroelectric material.
3. To understand the underlying principles of how ferroelectric materials work.

Methodology

Fabrication Phase

• Material Preparation: Students will deposit NiCuOx and Fe2O3 as active materials for the electrode in the cleanroom.
• Electrode Design: Multiple designs of electrodes will be fabricated, with these materials deposited on the Pt layer of the supercapacitor.

Testing Phase

• Polarization Experiments: A series of experiments will be conducted to apply different polarizations to the ferroelectric material.
• Electrochemical Experiments:  Conduct cyclic voltammetry, galvanostatic charge-discharge, and impedance spectroscopy tests, to estimate the performance of devices.

Expected Outcomes

• A deeper understanding of ferroelectric materials.
• A set of optimized electrode designs for ferroelectric supercapacitors.
• Insights into the effects of different polarizations on ferroelectric materials.

Starting date: As soon as possible 

Recommended type of project:  Semester project.

Work breakdown: 20% theory, 50% fabrication, 30% characterization.

Contact person: Hung-wei Li

Co‐supervisor: Hung-wei Li

Overview

This project aims to explore the mechanisms of interface interactions and charge trapping in multilayer capacitors composed of dielectric (DE), ferroelectric (FE), and antiferroelectric (AFE) materials. The focus will be on understanding how these interactions impact energy storage. By fabricating and characterizing various multilayer structures with precise control over silicon doping concentrations in Si: HfO2, we aim to optimize the performance of these devices.
The student will be responsible for fabricating the multilayer capacitors using Atomic Layer Deposition (ALD) and other relevant techniques in the cleanroom. The project involves a detailed study of interface phenomena, including the role of the Al2O3 dielectric layer in creating a built-in electric field that enhances energy storage efficiency.
The findings from this project will contribute to the development of advanced electronic components with improved energy efficiency capabilities.

Objectives:

• Fabrication of Multilayer Capacitors: Develop and execute a process flow for fabricating multilayer DE/FE/AFE capacitors using Atomic Layer Deposition (ALD) and other cleanroom techniques.
• Characterization of Interface Mechanisms: Investigate the role of interfaces in these multilayer structures, particularly how the introduction of an Al2O3 dielectric layer affects the built-in electric field and overall device performance.
• Analysis of Charge Trapping: Examine charge trapping phenomena within the multilayer capacitors to understand their influence on energy storage efficiency and memory stability.
• Optimization of Device Performance: Use the insights gained from interface and charge trapping analysis to refine the multilayer structure for improved energy storage density.

Expected workload for the student:

• Initial literature review
• Familiarize with the fabrication processes, including ALD, and the principles of interface phenomena in multilayer structures.
• Develop a detailed process flow for fabricating the multilayer capacitors, including the tools and methods to be used.
• Complete cleanroom safety and equipment training.
• Fabricate multilayer capacitors with varying silicon doping concentrations
• Perform measurements to assess interface properties and charge trapping effects, including electrical characterization (e.g., capacitance-voltage, polarization-electric field)

Expected learning outcome:

• Cleanroom Fabrication Techniques: Hands-on experience with Atomic Layer Deposition (ALD) and other cleanroom processes essential for fabricating advanced electronic materials (sputtering, MLA, wet etching, and ion beam etching).
• Material Characterization: How to use various electrical characterization techniques, such as capacitance-voltage (C-V) and current-voltage (I-V) measurements, and polarization-electric field (P-E) measurements to assess material properties.
• Structural Characterization: Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) to analyze layer morphology, crystallinity, and interface quality.
• Data Analysis and Interpretation: How to analyze experimental data and derive meaningful conclusions about material behavior and device performance.
• Research Documentation and Reporting: Skills in documenting experimental processes, analyzing results, and presenting findings in a clear and concise manner.

Requirements:

• Background in electrical engineering, material science, physics et similar
• General knowledge about semiconductor physics and devices, characterization methods
• Basic understanding of microfabrication processes
• Python/MATLAB/… for data analysis

Starting date: Spring 2024

Recommended type of project:  Semester project/Master Thesis Project

Co‐supervisor: Vanessa Conti

Overview

VO2 is a phase change material able to pass from an insulating-monocline phase to a conductive-rutile one when reaching a critical carrier concentration, while HfO2 is a commonly used high-k dielectric that exhibits ferroelectricity under particular process conditions (doping, controlled annealing), when crystallizing in an orthorhombic phase. A successful integration of these two materials would help into the development of an efficient way to gate a VO2 transistor, leading to the possibility to realize devices for neuromorphic computing and memory applications.

The aim of this project is to study the structural and electrical properties of Si:HfO2 and VO2 once the former is deposited on top of the latter. Particularly, the student will have the task to study the possibility to anneal the stack using a flash-lamp annealing (FLA) tool, which thanks to its highly localized heat supply should be able to cause a minor number of damages to the underneath VO2 layer with respect to a conventional rapid-thermal process (RTP).

In order to reach the goal, Si:HfO2 and its metallic capping layer will be deposited (ALD, sputtering) on top of an already made VO2 thin film PLD deposited. The stack will be subsequently annealed in different thermal and ambient conditions. Structural characterization of the annealed stack will be done by means of several techniques (SEM, XRD, scanning probe microscopies) and the output will be correlated with the different annealing processes. Subsequently, different set of measurements (ex. CV, PUND, C-AFM, PFM) will be done on the samples with the desired structural properties in order to characterize the ferroelectric properties of the Si:HfO2 and the integrity of the VO2. To fabricate the electrical test structures, the samples will be processed in CMi cleanroom (metal deposition, laser direct writing, etching).

Possibly, different capping layers options could be explored as an alternative to the standard TiN layer.

Expected workload for the student:

• Initial literature review
• Fabrication of the capping layer – ferroelectric – VO2 stack (ALD, sputtering)
• Annealing of the stack (RTP, FLA)
• Structural characterization (mostly SEM, XRD, possibly AFM)
• Fabrication of capacitor structures on the stack (sputtering, MLA, wet etching / IBE)
• Electrical measurements (mostly with a parameter analyzer, possibly C-AFM and PFM)

Expected learning outcome:

• Basic understanding on the design of an experiment procedure
  • How to interpret and communicate the data
• Microfabrication skills in a real cleanroom environment
• Structural and electrical characterization experience
• General knowledge on ferroelectric and phase change materials

Requirements:

• Background in electrical engineering, material science, physics et similar
• General knowledge about semiconductor physics and devices, characterization methods
• Basic understanding of microfabrication processes
• Python/MATLAB/… for data analysis

Starting date: Spring 2024

Recommended type of project:  Master Thesis Project

Contact person: Vanessa Conti