Highenergy ionbeam -maskingbynano apertures

Michael Beljaars, BSc

Supervisors:David N. Jamieson

Peter JohnstonPeter Mutsaers

Advice and moral support:Andrew Alves

Michael L. Taylor

Outline

Introduction• Motivation• Background

Project• Focus of the project• Challenges• Experimental setup• Simulation• Results• Conclusions

Lack of high aspect ratio (>1:100) nano-structuring (~10nm) tool

Creating photonic crystals:manipulation of light by periodic arrays ofnanostructures

Motivation

Background• Ion Beam Lithography (IBL)• Focused Ion Beam (FIB)

BackgroundIon Beam Lithography (IBL)• Light ions (Hydrogen, Helium)• High energy (1 – 5 MeV)• Lithography -> resist layer

(PMMA), etching

• Beamspot size ~ 1 µm

BackgroundFocused Ion Beam (FIB)• Heavy ions (Galium)• Low energy (10 – 50 keV)• Direct writing, no resist layer, no etching step required

• Beamspot size ~ 10 nm (state-of-the-art)

IBL versus FIB

Background

• Masking IBL

Background

• High energy ion beam masking by nano-apertures in AFM cantilevers

• Continue recent work by– Michael Taylor: Monte Carlo simulation of high

energy ions through nano-apertures– Andrew Alves: Experimental work on masking a 1.5

MeV Helium ion beam by nano-aperture

Focus of theproject

• Creating high aspect ratio nano-aperture– FIB milling in combination with Platinum deposition

• Align ion beam with aperture– Coarse alignment by goniometer– Fine tuning by beam rocking

• Observing full energy ions through aperture– Trial and error– Reducing number of scattered high energy ions (pre-

collimator)

Challenges

Experimental setup• Melbourne Pelletron MicroProbe 2

– 1.5 MeV Helium• Cantilever with nano-aperture• Photodiodes

– Copper grids– PMMA coating

• Goniometer

Simulation

Beam rocking• Propagating Rays by Matrices (PRAM)• Scanning coils

– 200 Gauss– Separation distance 430 mm– Angular range 1 degree

• Manufacturing of the nano-apertures– Design: slots and holes– Milled cantilevers

• Calibration copper grid• Theta dependence of spectrum• Energy shift• Full energy ions through aperture

– 50% full energy background noise with 750 µm image aperture; less than 20% with 250 µm image aperture

Results

• Project too extensive for a 3 month traineeship• Milling of apertures is not rocket science• Beam line

– Ion source– Power supply steering coils– Object apertures– Micro V slit– Image apertures

• Beam rocking• Masking

Conclusions

Outlook• Creating high aspect ratio nano-apertures by FIB milling

and Platinum deposition• Revision of the MP2 beam line• Implementation of beam rocking• Determination of degradation rate of photodiode• Application in step and repeat lithography