8/19/2019 Dose Assignment in Electron Beam Lithography

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DOSE ASSIGNMENT IN ELECTRON BEAM LITHOGRAPHY.

roject student: Adeleye Adetunji Oluwaseye

upervisor: Dr. Stephen Thoms

IntroductionOne of the challenges that hamper the resolution of the ElectronBeam Lithography is the Proximity Effect occurrence, which isexperienced during the exposure of sample materials.

Proximity EffectThe two main types of interaction in the Proximity Effect are:Forward scattering (small angle) and Back scattering (largeangle) [1].

Fig. 1a. Effect of Forward & Backward Scattering [2].There are two types of Proximity Effect namely the Intra-Proximity Effect and the Inter-Proximity Effect.

Fig. 1b. An Illustration of both the Inter-Proximity Effect andIntra-Proximity Effect [2]

The following are methods of compensating for Proximity Effectviz.: Dose modification, Shape modification, Equalization ofbackground dose correction (GHOST) and Multilayer resisttechnique, [1],[3] [4].

Experimental MethodsThis experiment was carried out on the three categories on thesubstrate: NO Proximity Effect Correction (NO PEC), OLDProximity Effect Correction (OLD PEC) and New Proximity EffectCorrection (NEW PEC).

The NO PEC has no Point Spread Function (PSF), the OLDPEC contains the PSF generated through the Monte CarloSimulation, while the NEW PEC contains the PSF generatedthrough the Modern Version of the Monte Carlo Simulation.For the Vector Beam 6 (VB6) Electron Beam Tool to write on asubstrate, it passes through the processes in Fig. 2., as eachprocess plays a vital role in the effectiveness of the desiredpattern.

Fig.2. Process Flow of an Electron Beam Lithography Pattern.

Result & Discussion

Fig. 3. Image analysis of the NO PEC, OLD PEC and NEW PECwith the error bar analysis.

The NO PEC reviews the variations of line widths, line edgeroughness, Intra-Proximity Effect and the dosage assigned isunevenly distributed. The OLD and NEW PEC, bothcompensated for the Proximity Effect as there is uniformity in theallocation of dose for pattern fracturing and improvement in theline edge roughness.

References[1] Van de Kraats A and Murali R , ‘Proximity Effect in E-beamLithography’ Atlanta Georgia: Nanotechnology Research Centre,Georgia Institute of Technology (2005).

[2] Chen. B and Ren, ‘Proximity Effect in Electron BeamLithography’ , IEEE, 0-7803-8511-X/04/$20.00:578, (2004).[3] Harafuji.K, Misaka.A.,Kawakita.K, Nomura, N., Hamaguchi,Hand Kawamoto, M, ‘ Proximity Effect Correction Data Processing

System For Electron Beam Lithography’, , Journal of Vacuum

Science and Technology B, Vol.10(1):133-142, (1992).[4] Owen,R and Rissman,P ‘ Proximity Effect Correction for

Electron Beam Lithography by Equalization of Background Dose’

, Journal of Applied Physics, Vol.54(6):3573-3581 (1983).

University of Glasgow, charity number SC004401

Intraproximity effect

Conceptual

Design

Layout Editor

Software

Layout Beamer

Software

SamplePreparation

Belle Software Exposure (VB 6)

Development Sputter Coating Desired Pattern

310

320

330

340

350

360

370

380

centre join end

width (nm)

region

DOSE 475µC cm-2 of 0.5µm lines

NO PEC

OLD PEC

NEW PEC