MOSFET transistor fabrication on AFM tip

Rudnicki, Kamil (2014) MOSFET transistor fabrication on AFM tip. PhD thesis, University of Glasgow.

Abstract

The project is concerned with the development of methods for the fabrication of magnetic sensor devices on Atomic Force Microscopy (AFM) probes and their characterization. The devices use the principle of the Hall effect (based on the Lorentz force) to sense the magnetic properties of a magnetized specimen.

In the past Hall bar sensors have been fabricated using semimetals such as Bismuth, or using 2-d electron gas material based on heterojunctions in III-V material. The former probes are limited by low sensitivity. The latter are limited by the difficulty encountered when trying to integrate the device with a force-sensing cantilever. The highest spatial resolution reported for a Hall bar operating at room temperature is 50 nm. Due to quantum effects (long mean free path), scaling down devices based on high mobility material results in a drop in sensitivity. For magnetic material studies of current interest higher resolutions are required. To achieve this goal in a material system which is compatible with micromachining the proposed approach utilises silicon as the sensing material. Silicon Hall bars have already been reported to work for large scale devices.

This thesis presents the development of p-type enhancement mode MOSFET transistor fabrication process on a tip of Atomic Force Microscope (AFM) probe. The active device fabrication process was developed in order to allow fabrication of a magnetic sensor for Scanning Hall Probe Microscope (SHPM). The Hall bar was constructed on the apex of the AFM tip of attractive mode probes.

The fabrication is performed in batches by using common semiconductor techniques leading to micromachining of the Si substrate, formation of the active device and cantilever release step. The transistor characteristics are presented, compared with expected performance of the modelled device and the reasons for differences are discussed.

In this work, a method for application of spin-on-dopant on highly topographic structures is developed. Other encountered process incompatibilities are dealt with to finally present a full process for p-type enhancement mode MOSFET transistor on AFM tip fabrication.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: MOSFET, transistor, fabrication, AFM, cantilever, tip
• Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Supervisor's Name: Weaver, Prof. Jonathan and Dobson, Dr. Phil
• Date of Award: 2014
• Depositing User: PhD Kamil Rudnicki
• Unique ID: glathesis:2014-5398
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 11 Aug 2014 09:50
• Last Modified: 11 Aug 2014 09:53
• URI: https://theses.gla.ac.uk/id/eprint/5398