Multiscale Approach for the Analysis of Channeling Profile

Measurements of Ion Implantation Damage

G. Hobler, G. Otto, D. KovacL. Palmetshofer1,

K. Mayerhofer², K. Piplits²1 Inst. Semiconductor and Solid State Physics, Univ. Linz

² Inst. Chem. Technol. and Analytics, TU Vienna

Institute of Solid-State Electronics

Damage Models in BC Simulations

• Traditional model:– defect positions: generated statistically

– atom positions: random interstitial model

– dynamic annealing: „recombination factor“

• Proposed model:– defect positions: trace each defect during the whole

simulation

– atom positions: take from ab-initio simulations

– dynamic annealing: kinetic lattice Monte Carlo simulation (kLMC) after each collision cascade

Overview

• Introduction

• BC-kLMC approach

• Application to channeling profile measurement (CPM) experiments

Damage Measurements

RBS

Channelingprofile

Channeling Implantations

• Fit dose dependence of channeling implantation profiles recombination factor

frec=0.125 Nsat=41021cm-2

(G.Hobler et al., J. Vac. Sci. Technol B14 (1) 272, 1996)

Channeling Profile Measurements

• Measure pre-existing crystal damage with a low-dose channeling implant

(M. Giles et al., MRS Symp. Proc. 469, 253, 1997)

The Role of Dynamic Annealing in Si

• Temperature dependence of implant damage:

(J.E. Westmoreland et al., Appl. Phys. Lett. 15, 308, 1969)

The Role of Dynamic Annealing in Si

• Dose-rate dependence of implant damage:

T=300K

(O.W. Holland et al., Rad. Eff. 90, 127, 1985)

70µA/cm²

0.14µA/cm²

Overview

• Introduction

• BC-kLMC approach

• Application to channeling profile measurement (CPM) experiments

Coupled BC-kLMC Approach

• Traditional approach:

• BUT: type and amount of defects influence BC trajectories (dechanneling)

kLMC

BCloopover

cascades

1 cascade

pointdefects

point defects + clusters

Coupled BC-kLMC Approach

• Proposed new approach:

kLMC

BCloopover

cascades old defects + new point defects

point defects + clusters

atom positionsfor each defect

defects

Details of kLMC

• Each defect is associated with one or more lattice sites

• Defects: Vn, In (n=1,2,3,...)

• Events:– Diffusion hops (I, V)

– Reactions of defects located within capture radius

Vn+V Vn+1 Vn+I Vn-1 In+I In+1 In+V In-1

• Parameters:

– DV=310-13 cm²/s DI=6.3510-17 cm²/s

– (Capture radii)

Details of kLMC

• „Old“ defects: restricted to column(periodic boundaryconditions)

• „New“ defects: anywhere

• Interaction between „new“

and „old“ defects: Using periodicity of „old“ defects

Details of BC

• Read defects from kLMC (columnar domain)

• Use periodicity to generate defects around projectile

• Atom positions from ab-initio calculations (VASP)– defect structure

– strain around defect

• All defects composed of individual I and V (currently)

Overview

• Introduction

• BC-kLMC approach

• Application to channeling profile measurement (CPM) experiments

CPM Experiments

• Damage implant: N, 30 keV, 31014 cm-², 10° tilt

• CPM implant: B, 30 keV, 1013 cm-2, 0° tilt

shield(110)-Si

CPM Experiments

• Results:

CPM Simulation Results

• Simulation results without strain:

CPM Simulation Results

• Strain from vacancies:

CPM Simulation Results

• Strain from interstitials:

What is wrong?

• Defects: Vn, In (n=1,2,3,...)

• Events:– Diffusion hops (I, V)

– Reactions of defects located within capture radius

Vn+V Vn+1 Vn+I Vn-1 In+I In+1 In+V In-1

• Parameters:

– DV=310-13 cm²/s DI=6.3510-17 cm²/s

– (Capture radii)

• Lack of amorphous pockets?

What is wrong?

• Defects: Vn, In (n=1,2,3,...)

• Events:– Diffusion hops (I, V)

– Reactions of defects located within capture radius

Vn+V Vn+1 Vn+I Vn-1 In+I In+1 In+V In-1

• Parameters:

– DV=310-13 cm²/s DI=6.3510-17 cm²/s

– (Capture radii)

• Lack of amorphous pockets? NO

• Approximate treatment of I-Clusters?

What is wrong?

• I-Clusters:

• Similar study on RBS-C: Efficiency of I2, I3, I4 within 40% of split-110 interstitial

I I2 I3

I4a I4b

(G. Lulli et al., Phys. Rev. B69, 165216, 2004)

What is wrong?

• Defects: Vn, In (n=1,2,3,...)

• Events:– Diffusion hops (I, V)

– Reactions of defects located within capture radius

Vn+V Vn+1 Vn+I Vn-1 In+I In+1 In+V In-1

• Parameters:

– DV=310-13 cm²/s DI=6.3510-17 cm²/s

– (Capture radii)

• Lack of amorphous pockets? NO

• Approximate treatment of I-Clusters? Probably not

• Attraction of I+Vn, V+In and/or Repulsion of I+In, V+Vn

Conclusions

• New approach for implant damage simulations– coupled BC and kLMC

– atom positions from ab-initio

• Consistent simulation of both defect generation and analysis

• Simulations yield too much damage need to use– interaction radii to favor recombination and/or

– reaction barriers to impede clustering