Suppression of Phosphorus
Diffusion in Silicon by
Fluorine Co- implantation
By
Dr Huda Abdel Wahab A. El Mubarek
[email protected]
Royal Academy of Engineering and EPSRC
Research Fellow
Acknowledgments
• University of Southampton
• Royal Academy of Engineering and
EPSRC: Fellowship
• EPSRC: EPSRC Grant
Contents
• Motivation
• Experimental Procedure
• Results
– Effect of F+ Implantation on Phosphorus Diffusion
in Si
– Fluorine Diffusion in Silicon
– Fluorine and Phosphorus Implantation Damage in
Silicon
• Discussion
• Conclusions
Motivation
• Phosphorus diffuses Significantly in Si due
to Transient Enhanced Diffusion (TED)
• F+ implantation into Si1:
• Eliminates B TED
• Significantly reduces B thermal diffusion
1.H. A. W. El Mubarek, P. Ashburn, “Reduction of boron thermal diffusion and elimination of boron transient
enhanced diffusion in silicon by high energy fluorine implantation”, Applied Physics Letters, vol. 83
(20), pp. 4134-4136, (2003).
• No work to date on the effect of F +
Implantation on Phosphorus diffusion in Si
Experimental Procedure
(100) P type Si
Experimental Procedure
F+ 185KeV, 9x1014
or 2.3x1015
ions/cm2
F Rp = 0.4µm
(100) P type Si
Experimental Procedure
P+ 100KeV, 6x1013
ions/cm2
P Rp = 0.15µm
F Rp = 0.4µm
(100) P type Si
Experimental Procedure
• Samples diced 1cm×1cm Pieces
• Rapid Thermal Annealing in Nitrogen at
800°C , 900°C or 1000°C for 30 seconds
• P an F profiles obtained by SIMS
• Transmission Electron Microscopy
Results
Effect of F+ implantation
on P diffusion in Si at
800°C,30s in Nitrogen
Phosphorus Profiles (800°C, 30s)
1.E+19
P (no F)
Concentration (cm -3 )
P (9e14F)
P (2.3e15F)
P as imp
1.E+18
1.E+17
0.0
0.1
0.2
0.3
0.4
0.5
Depth (Microns)
F+ implantation eliminates Phosphorus diffusion at 800°C
Effect of F+ implantation on P
diffusion in Si at 900°C,30s in
Nitrogen
Phosphorus Profiles (900°C, 30s)
1.E+19
Concentration (cm-3)
P as imp
P(no F)
P (9e14F)
1.E+18
1.E+17
0.0
0.1
0.2
0.3
0.4
0.5
Depth (microns)
F+ implantation eliminates Phosphorus diffusion at 900°C
Effect of F+ implantation on P
diffusion in Si at 1000°C,30s in
Nitrogen
Phosphorus Profiles (1000°C, 30s)
1.E+19
Concentration (cm-3)
P as imp
P(no F)
P(2.3e15 F)
P (9e14 F)
1.E+18
1.E+17
0.0
0.1
0.2
0.3
0.4
0.5
Depth (Microns)
F+ implantation eliminates Phosphorus diffusion at 1000°C
Fluorine Diffusion in Silicon
185KeV 9×1014cm-2 F+ diffusion in Si
1.E+20
Concentration (cm -3 )
P
F (As implanted)
F (800°C, 30s)
1.E+19
1.E+18
1.E+17
1.E+16
0.0
0.2
0.4
0.6
Depth (Microns)
0.8
1.0
185KeV 9×1014cm-2 F+ diffusion in Si
1.E+20
Concentration (cm-3)
P
F (As implanted)
F (800°C, 30s)
F (900°C.30s)
1.E+19
1.E+18
1.E+17
1.E+16
0.0
0.2
0.4
0.6
Depth (Microns)
0.8
1.0
185KeV 9×1014cm-2 F+ diffusion in Si
1.E+20
Concentration (cm -3 )
P
F (As implanted)
F (800°C, 30s)
F (900°C.30s)
F (1000°C,30s)
1.E+19
1.E+18
1.E+17
1.E+16
0.0
0.2
0.4
0.6
Depth (Microns)
0.8
1.0
185KeV 2.3×1015cm-2 F+ diffusion in Si
1.E+20
P
Concentration (cm-3 )
F (As implanted)
F (800°C,30s)
1.E+19
1.E+18
1.E+17
1.E+16
0.0
0.2
0.4
0.6
Depth (Microns)
0.8
1.0
185KeV 2.3×1015cm-2 F+ diffusion in Si
1.E+20
Concentration (cm-3 )
P
F (As implanted)
F (800°C,30s)
F (900°C,30s)
1.E+19
1.E+18
1.E+17
1.E+16
0.0
0.2
0.4
0.6
Depth (Microns)
0.8
1.0
185KeV 2.3×1015cm-2 F+ diffusion in Si
1.E+20
Concentration (cm -3 )
P
F (As implanted)
F (800°C,30s)
F (900°C,30s)
F (1000°C,30s)
1.E+19
1.E+18
1.E+17
1.E+16
0.0
0.2
0.4
0.6
Depth (Microns)
0.8
1.0
Phosphorus and Fluorine
Implantation Damage in
Silicon
Imaged by Transmission
Electron Microscopy
Taken by Dr Amy Gandy
A Bright field image taken down the
(100) zone axis
F+ 185KeV 2.3x1015cm-2, P+ 100KeV 1x1015cm-2, 900°C, 30min in Nitrogen
Region 1
Region 2
Dislocation
Loops and
Vacancy
Clusters
Region 1: extends from about 145nm below the
surface and is 75nm wide
Region 2: extends from about 315nm below the
surface and is 520nm wide
A Bright field , Off Bragg image of
the Vacancy-Type defects
F+ 185KeV 2.3x1015cm-2, P+ 100KeV 1x1015cm-2, 900°C, 30min in Nitrogen
200nm
VacancyClusters
Discussion
1.E+20
P
Concentration (cm-3)
F (As implanted)
F (1000C,30s)
1.E+19
Vacancy-Fluorine
Clusters
1.E+18
1.E+17
1.E+16
0.0
0.2
0.4
0.6
0.8
Depth (Microns)
• Vacancy-Fluorine Clusters extend through out the F profile
• The Phosphorus profile is entirely within the Vacancy-fluorine Clusters
Region
• VF clusters resulted in an under saturation of interstitials and hence
eliminated Phosphorus Diffusion
1.0
Conclusions
• F+ implantation eliminated Phosphorus
Diffusion !
• F+ implantation is a simple and efficient
technique to obtain shallow Phosphorus
junctions in Silicon !