Development of Time-Of-Flight Neutron Depth Profiling at Penn · September 12-16, 2005 TRTR-IGORR 2005 • Neutron depth profiling – powerful surface characterization technique

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


• 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


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


NEUTRON DEPTH PROFILING

€

10B+n → 7Li*+4He(1472.6keV); 7Li* → 7Li(840keV)+γ(478keV)

€

10B+n → 7Li(1013keV)+4He(1776.73keV)


PENN STATE NDP SETUP


BPSG STANDARD SAMPLE


BPSG STANDARD SAMPLE


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


PENN STATE TOF-NDP SETUP


• 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


TIME-OF-FLIGHT NDP:Preliminary Measurements - Offline

0 10 20 30 40 50 60 70 800

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3 3.05 3.1 3.15 3.2 3.25 3.3 3.35 3.4 3.45 3.50

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4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.60

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CONVENTIONAL NDP:Same Sample

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HOW TO IMPROVE

• Noise elimination

• Impedance matching along the entire signal transmission line

• Microchannel plate (MCP) assembly: special conical anode


MCP SIGNAL

-10 -6 -2 2 6 10 14 18 22 26 30 34 38 42 46 50-0.015

-0.01

-0.005

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MCP O

utp

ut (V

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Signal Improvement:Special Conical Anode


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


THANK YOU!

Penn StateBreazeale Nuclear Reactor during a pulse


CONVENTIONAL NDP:Same Sample

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Documents

Development of Time-Of-Flight Neutron Depth Profiling at Penn · September 12-16, 2005 TRTR-IGORR 2005 • Neutron depth profiling – powerful surface characterization technique