Post on 22-Jul-2020
Sacit M. ÇetinerKenan Ünlü
Penn State UniversityRadiation Science & Engineering Center
University Park, PA 16802-2304
Gregory R. DowningNIST
Development of Time-Of-Flight Neutron Depth Profiling at Penn State University -
Preliminary Results
TRTR-IGORR 2005Gaithersburg, MD
September 12-16, 2005
September 12-16, 2005 TRTR-IGORR 2005
• Neutron depth profiling (NDP)• Conventional NDP
– limitations• Penn State NDP Setup• Time-of-Flight NDP (TOF-NDP)
– need– possibilities
• Penn State TOF-NDP Setup• Preliminary Results
INTRODUCTION
September 12-16, 2005 TRTR-IGORR 2005
• Neutron depth profiling– powerful surface characterization technique for certain light
elements– monoenergetic, isotropic charged particle emission– rapid energy loss– nondestructive
• Conventional neutron depth profiling (NDP)– direct measurement of residual energy– SBD, PIPS or Photodiode PIN detectors
• Time-of-Flight NDP– particle flight time is measured– microchannel plates (MCP) can be used
NEUTRON DEPTH PROFILING
September 12-16, 2005 TRTR-IGORR 2005
APPLICATIONS OF NDP• B depth profile in insulation layers such as
borophoshosilicate glass (BPSG), and implanted B distributions of semiconductor wafers
• He dynamics in technologically important materials
• Li depth profile in lithium niobate (LiNbO3) optical waveguide
• He damage and effusion in fully stabilized zirconia
• Li and N profiles in lithium phosphorus oxynitride (LiPON), and Li profile in lithium cobaltoxide (LiCoO2), two important lithium-ion battery materials
September 12-16, 2005 TRTR-IGORR 2005
NEUTRON DEPTH PROFILING
€
10B+n → 7Li*+4He(1472.6keV); 7Li* → 7Li(840keV)+γ(478keV)
€
10B+n → 7Li(1013keV)+4He(1776.73keV)
September 12-16, 2005 TRTR-IGORR 2005
PENN STATE NDP SETUP
September 12-16, 2005 TRTR-IGORR 2005
BPSG STANDARD SAMPLE
September 12-16, 2005 TRTR-IGORR 2005
BPSG STANDARD SAMPLE
September 12-16, 2005 TRTR-IGORR 2005
TIME-OF-FLIGHT NDP
• Particle flight time is measured, which is inversely proportional to particle residual energy
• Instead of semiconductor detectors, microchannel plates (MCP) can be used for precise time signals
• Secondary electrons ejected from the surface of the sample as the charged particle emerges are used to trigger the start signal; alpha or recoil give the stop signal
September 12-16, 2005 TRTR-IGORR 2005
PENN STATE TOF-NDP SETUP
September 12-16, 2005 TRTR-IGORR 2005
• Time-of-NDP is particularly important for depth profile measurements of shallow and ultra shallow source/drain junctions– device thickness <200 nm
TIME-OF-FLIGHT NDP
September 12-16, 2005 TRTR-IGORR 2005
TIME-OF-FLIGHT NDP:Preliminary Measurements - Offline
0 10 20 30 40 50 60 70 800
50
100
150
200
250
Time (ns)
Counts
September 12-16, 2005 TRTR-IGORR 2005
TIME-OF-FLIGHT NDP:Preliminary Measurements - Offline
3 3.05 3.1 3.15 3.2 3.25 3.3 3.35 3.4 3.45 3.50
50
100
150
200
250
Time (ns)
Counts
September 12-16, 2005 TRTR-IGORR 2005
TIME-OF-FLIGHT NDP:Preliminary Measurements - Offline
4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.60
50
100
150
200
250
Energy (MeV)
Counts
September 12-16, 2005 TRTR-IGORR 2005
CONVENTIONAL NDP:Same Sample
4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.60
20
40
60
80
100
120
140
160
180
200
Particle Energy (MeV)
Counts
September 12-16, 2005 TRTR-IGORR 2005
HOW TO IMPROVE
• Noise elimination
• Impedance matching along the entire signal transmission line
• Microchannel plate (MCP) assembly: special conical anode
September 12-16, 2005 TRTR-IGORR 2005
MCP SIGNAL
-10 -6 -2 2 6 10 14 18 22 26 30 34 38 42 46 50-0.015
-0.01
-0.005
0
0.005
0.01
MCP O
utp
ut (V
)
-10 -6 -2 2 6 10 14 18 22 26 30 34 38 42 46 50-1.5
-1
-0.5
0
0.5
1
Time (nsec)
Preamp O
utp
ut (V
)
September 12-16, 2005 TRTR-IGORR 2005
Signal Improvement:Special Conical Anode
September 12-16, 2005 TRTR-IGORR 2005
SUMMARY
• Preliminary measurement results have been presented
• Further optimization is needed for higher signal resolution
• Improved depth resolution will make it possible to measure B depth profiles in ultra shallow junctions
September 12-16, 2005 TRTR-IGORR 2005
THANK YOU!
Penn StateBreazeale Nuclear Reactor during a pulse
September 12-16, 2005 TRTR-IGORR 2005
CONVENTIONAL NDP:Same Sample
190 200 210 220 230 240 250 260 2700
20
40
60
80
100
120
140
160
180
200
Channel Number
Counts
September 12-16, 2005 TRTR-IGORR 2005
TIME-OF-FLIGHT NDP
0 100 200 300 400 500 600 700 800 900 10000
2
4
6
8
10
12
14
16
18
20
Projectile Depth (nm)
Energy Reso
lution (ke
V)
Straggling
Multiple-angle Scattering
System
Geometrical
Total
September 12-16, 2005 TRTR-IGORR 2005
TIME-OF-FLIGHT NDP
0 20 40 60 80 100 120 140 160 180 2000
2
4
6
8
10
12
Projectile Depth (nm)
Energy Reso
lution (ke
V)
Straggling
Multiple-angle Scattering
System
Geometrical
Total