DOC PREVIEW
UW-Madison G 777 - CASINO V2.42 - A Fast and Easy-to-use Modeling Tool for Scanning Electron Microscopy

This preview shows page 1-2-3 out of 10 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 10 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 10 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 10 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 10 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

SCANNING VOL. 29, 92–101 (2007) Wiley Periodicals, Inc.CASINO V2.42—A Fast and Easy-to-use Modeling Tool for ScanningElectron Microscopy and Microanalysis UsersDOMINIQUE DROUIN1,ALEXANDRE R´EALCOUTURE1,DANY JOLY1,XAV I E R TASTET1,VINCENT AIMEZ1,RAYNALD GAUVIN21Electrical Engineering Department, Universite de Sherbrooke, Sherbrooke, Qu´ebec, J1K 2R1, Canada2Department Mining, Metals and Materials Engineering, McGill University, Montreal, H3A 2B2 , CanadaSummary: Monte Carlo simulations have been widelyused by microscopists for the last few decades. In thebeginning it was a tedious and slow process, requiringa high level of computer skills from users and longcomputational times. Recent progress in the microelec-tronics industry now provides researchers with afford-able desktop computers with clock rates greater than3 GHz. With this type of computing power routinelyavailable, Monte Carlo simulation is no longer anexclusive or long (overnight) process. The aim of thispaper is to present a new user-friendly simulation pro-gram based on the earlier CASINO Monte Carlo pro-gram. The intent of this software is to assist scanningelectron microscope users in interpretation of imag-ing and microanalysis and also with more advancedprocedures including electron-beam lithography. Thisversion uses a new architecture that provides resultstwice as quickly. This program is freely available to thescientific community and can be downloaded from thewebsite: www.gel.usherb.ca/casino. SCANNING 29:92–101, 2007. 2007 Wiley Periodicals, Inc.Key words: Monte Carlo simulation software, scanningelectron microscopy, BE line scan, X-ray line scan, E-beam lithographyPACS: 02.70.Uu; 05.10.Lm; 07.05.Tp; 68.37.Hk;85.40.HpIntroductionThe motivation of this work was to provide an easy-to-use and accurate simulation program of electronAddress for reprints: Dominique Drouin, D´epartement deg´enie´electrique et g´enie informatique, Universit´e de Sherbrooke,Sherbrooke (Qu´ebec), J1K 2R1, Canada,E-mail: [email protected] 8 December 2006; Accepted with revision25 January 2007beam–sample interactions in a scanning electron micro-scope (SEM). It can be used to assist scanning electronmicroscopy users in planning and interpreting their rou-tine SEM-based imaging and analysis and also in moreadvanced topics such as electron-beam lithography. Onthe basis of a single-scattering algorithm, this softwareis specially designed for modeling low-energy beaminteractions in bulk and thin foil samples. The initialversion of CASINO (Hovington et al . 1997) was devel-oped for expert users and presented some limitationsin data handling capabilities. These aspects have beenaddressed in the present version by the developmentof a new user interface. This paper presents the simu-lation models used, the main features of the program,and some example applications.CASINO v2.42 Structure and PrinciplesThis software has been developed using C++ objectoriented programming language. It therefore takes fulladvantage of the native PC operating environment. Thegraphical interface used was the MFC library. The fol-lowing section describes the details of program opera-tion: sample modeling, electron trajectory calculations,output and other special features.Sample ModelingTwo basic geometries for sample representation arehandled by CASINO v2.42: vertical planes and hor-izontal planes. These simple models can be used toreproduce a large number of real samples such as mul-tilayers, heterostructures and grains boundaries. Usingthe Simulation/Modify Sample dialog box, the appropri-ate type of geometries for the desired sample modeling,the total number of regions with different chemicalcomposition, and the thickness or width of each regionare set. The substrate option extends the thickness ofthe bottom region in the case of horizontal planes, orD. Drouin et al.: CASINO 2.42 93the width of both first and last regions in the case ofvertical planes, to a value much larger than the electronpenetration depth in the sample.Each of the added layers then needs to be matched toa chemical composition. This operation is easily doneby “double-clicking” on the layer and then enteringdirectly the chemical formula (SiO2 for SiO2)ortheatomic or weight fraction of each element present. Thesoftware will calculate an average density based on theweight fraction of each element, but it is recommendedto use known density values in g/cm3, if available.A library function allows the user to store specialcompositions, for uncommon alloys and compounds.Electron Trajectory CalculationThe main part of a Monte Carlo program is the sim-ulation of a complete electron trajectory. This sectiondescribes the different steps and physical models usedby CASINO to calculate electron trajectories.Different physical models are preprogrammed, soexpert users can set them using the Simulation/ChangePhysical Models according to their different prefer-ences. The present work uses the default values.The tool is intended to represent, as accurately aspossible, the actual interaction conditions in SEMs.Modern electron optics and advanced electron sourcessuch as field emission can achieve subnanometerimage resolution on the sample. CASINO assumes aGaussian-shaped electron beam, where the user canspecify the electron-beam diameter of their instrument,d, representing 99.9% of the total distribution of elec-trons. The actual landing position of the electron on thesample is thus calculated using eq(1):X0=dlog(R1)2 × 1.65× cos(2πR2)Y0=dlog(R1)2 × 1.65× cos(2πR3)(1)where Rxare random numbers uniformly distributedbetween 0 and 1.The initial penetration angle is fixed by the user, andno scattering angle is initially calculated. The distancebetween two successive collisions is evaluated usingthe equations:L =−λellog(R4)[nm] (2)1λel= ρN0ni =1CiσielAi(3)where Ci, Aiare the weight fraction and atomic weightof element i , respectively, ρ is the density of theregion (g/cm3)andN0the Avogadro’s constant. Thevalue of the total cross-section (Mott and Massey1949, Czyzewski et al. 1990), σi(nm2), for eachchemical element of the region is determined using theprecalculated and tabulated value (Drouin et al ., 1997).This program neglects the effect of inelastic scatter-ing on electron deviation and groups all the electronenergy loss events in a continuous energy loss function(Joy and Luo, 1989). With this assumption, the energy,in keV, between collisions can


View Full Document

UW-Madison G 777 - CASINO V2.42 - A Fast and Easy-to-use Modeling Tool for Scanning Electron Microscopy

Documents in this Course
Load more
Download CASINO V2.42 - A Fast and Easy-to-use Modeling Tool for Scanning Electron Microscopy
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view CASINO V2.42 - A Fast and Easy-to-use Modeling Tool for Scanning Electron Microscopy and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view CASINO V2.42 - A Fast and Easy-to-use Modeling Tool for Scanning Electron Microscopy 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?