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
