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Comparison of elemental boron and boron halide implants into silicon
Nuclear Instruments and Methods in Physics Research B 237 (2005) 93–97 www.elsevier.com/locate/nimb
Comparison of elemental boron and boron halide implants into silicon J.A. Sharp *, R.M. Gwilliam, B.J. Sealy, C. Jeynes, J.J. Hamilton, K.J. Kirkby Surrey Ion Beam Centre, Advanced Technology Institute School of Electronics and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK Available online 24 June 2005
Abstract This paper investigates the electrical activation of boron halide molecular implants into silicon and compares them þ þ to boron implants at the same effective energy. The implanted species: B+, BFþ 2 , BCl2 and BBr2 were implanted to doses of 2 · 1014 and 1 · 1015 B cm2 the energy of the molecular implants was calculated to give an effective boron implant energy of 5 keV. Samples cut from the wafers were annealed for 30 s at temperatures ranging from 800 C to 1100 C. Hall effect measurements were used to compare and contrast the electrical activation of the boron between þ the different halide species and doses. It was found that molecular implants of BBrþ 2 and BCl2 do not enhance the elecþ trical activation of boron to the same extent that BFþ implants do. The BBr implants are only comparable with boron 2 2 after annealing at high temperatures (above 1000 C). The BFþ implants show enhanced electrical activation with 2 respect to boron for all the annealing temperatures and doses studied. 15 Rutherford backscattering spectroscopy (RBS) of silicon implanted with BBrþ boron 2 to a dose of 1 · 10 atoms cm2, shows that an amorphous region is created during the implantation. This region fully re-grows after annealing at 1100 C; lower temperature anneals remove only part of the amorphous layer. RBS channelling shows that a fraction of the bromine takes up substitutional lattice sites upon implantation, and that this fraction increases as the samples are annealed at temperatures above 600 C with 40% of the B being in substitutional sites after annealing at 1050 C. 2005 Elsevier B.V. All rights reserved. PACS: 61.72.Tt; 81.15.Np Keywords: Semiconductors; Boron; Shallow-junctions; Activation; RBS
*
Corresponding author. Tel.: +44 1483 686 093; fax: +44 1483 689 404. E-mail address: [email protected] (J.A. Sharp).
0168-583X/$ - see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.04.084
94
J.A. Sharp et al. / Nucl. Instr. and Meth. in Phys. Res. B 237 (2005) 93–97
1. Introduction Complementary Metal oxide semiconductor (CMOS) transistors are the building blocks of silicon chips. Shrinking device dimensions has the most beneficial effect on performance in terms of speed and efficiency. For ultra shallow-junctions the International Technology Roadmap for Semiconductors (ITRS) [1] requires that the depth of the individual transistors should shrink as well as the area they occupy, so that junction depths of <20.4 nm will be required for technology nodes of 90 nm and beyond [1]. In order to achieve shallower implants using ion implantation, new low energy implanters can be used, but these require significant investment. An alternative is to implant molecular ions containing the required dopant (in this case boron) with other heavier atoms. Currently, molecular boron difluoride (BFþ 2 ) is often used for boron doping, especially since the coimplantation of fluorine appears to have a beneficial effect on the electrical activation of boron [2], although there are some reports that it can also damage the gate oxide [3]. In the same group in the periodic table as fluorine are chlorine and bromine. These halide elements are heavier than fluorine; therefore shallower implants can be achieved at similar implant energies. The work carried out here is to evaluate the suitability of these heavier halide elements as molecular implants with boron þ (BClþ 2 , BBr2 ) into crystalline silicon. Comparisons of the electrical characteristics of these implants with standard B and BFþ 2 implants have been carried out after rapid thermal annealing using Hall effect measurements. Rutherford backscattering spectroscopy (RBS) has been used to investigate the both the damage and bromine depth distributions in the BBrþ 2 samples.
2. Experimental Czochralski grown 100 mm (1 0 0) n-type silicon wafers have been implanted with boron, BFþ 2, þ BClþ or BBr using a 200 kV Danfysik DF1090 2 2 ion implanter. The sources were BF3 (gas), BCl3 (liquid-gas) and BBr3 (liquid), respectively. Two doses of 2 · 1014 and 1 · 1015 boron atoms cm2
were investigated. The energies used for the boron halide molecular implants give an effective energy for the boron implant of 5 keV. The energies for the halide implants are as follows: B ¼ 5 keV; BFþ 2 ¼ 22.6 keV; BClþ 2 ¼ 37.8 keV; BBrþ 2 ¼ 78.9 keV. Rapid thermal annealing (RTA) was carried out on these samples using the Process Products Corporation 18 lamp RTA machine. A 30 s isochronal study was carried out from 800 C to 1100 C. A 350 C, 1 min stabilisation step was used prior to ramping up to the designated temperatures. Hall effect measurements were made to determine the carrier concentration and hence the percentage electrical activation of the boron, using an Accent HL5500 Hall effect measurement apparatus. Rutherford backscattering spectroscopy (RBS) was carried out using 1.5 MeV He+ ions using the high voltage engineering tandetron tandem accelerator. The samples used for RBS had been annealed in the temperature range 600– 1100 C, for times of 10 and 100 s. Data was collected with the sample in a random orientation, ion channelling was also used in both normal and glancing exit (45) modes. Subsequent to RBS analysis the DataFurnace [4] was used to analyse the data.
3. Results and discussion 3.1. Electrical activation Figs. 1 and 2 show, respectively, the percentage of electrically active boron atoms for the samples implanted with 1 · 1015 B cm2 and 2 · 1014 B cm2 boron doses for samples annealed in the range 800–1100 C for a time of 30 s. Fig. 1 (for dose of 1 · 1015 B cm2) shows that as the anneal temperature increases, the electrical activation of the boron increases. The range of the activation is from 5% for the lowest (B), up to 100% for the highest (BF2). The BF2 implant, as expected from the literature [5,2], shows the
J.A. Sharp et al. / Nucl. Instr. and Meth. in Phys. Res. B 237 (2005) 93–97 Percentage electrical activation of B for 1e15 dose
% activation
100 80
B BF2 BCl2 BBr2
60 40 20 0 800
900
1000
1050
1100
Anneal temperature (degrees C)
Fig. 1. Percentage electrical 1 · 1015 atoms cm2 dose.
activation
of
boron,
for
Percentage electrical activation of B for 2e14 dose 120
% activation
100
95
800 C. This trend is also apparent in the BBr2 implant. The BBr2 implant follows BCl2 much more closely at this lower dose. The range of activation is between 5% and 100%, similar to those for the high doses, although when comparing the two sets of data the higher dose normally shows the higher activation. This does not hold for the BBr2 implants, where the lower dose always shows the greater activation of the boron. This may be due to the extra damage introduced by the 1 · 1015 dose, which will take longer to anneal out. It could also be caused by solid solubility issues relating to the bromine and the increased strain that occurs for the higher dose in accommodating the bromine into the silicon lattice. 3.2. RBS results
80
B BF2 BCl2 BBr2
60 40 20 0 800
900
1000
1050
1100
Anneal temperature (degrees C)
Fig. 2. Percentage electrical 2 · 1014 atoms cm2 dose.
activation
of
boron,
for
highest activation, the BCl2 implant also achieves higher activation than the boron only implant. A peak in electrical activation for the BF2 and BCl2 implants is observed at 1050 C. The BF2 curve shows activation above 100%. This may be within the error bars for the measurements, but may also be caused by a slight error in the implant fluence i.e. slightly above 1 · 1015 ions cm2. The hall scattering factor my also be a reason for the slightly high carrier concentration. The activation of the BBrþ 2 implant is generally below that of the boron implant. The only temperatures where it is greater than the boron implant is at the very lowest and highest temperatures, a trend which can also be seen with the lower dose results below (Fig. 2). The results for the lower dose implants show almost exactly the same trends as those for the higher doses. BF2 again shows the highest activation with a peak at 1050 C. For this lower dose, the BCl2 implant only achieves activation greater than the boron implant above 1050 C, and at
Fig. 3 shows the glancing exit RBS ion channelling results in the region corresponding to the silicon surface for samples implanted with BBrþ 2 of 1 · 1015 B cm2 and annealed in the temperature range 600–1100 C for a time of 10 s, the as implanted spectrum is also shown for comparison. After implantation the channelled spectra shows that the silicon surface region has been amorphised to a depth of 60 nm. When the sample is annealed for 10 s, at 600 C anneal a small amount of regrowth occurs. More re-growth is seen after the 700 C, 10 s anneal. Even after annealing at 800 C, 900 C and 1000 C, this layer has not totally re-grown as evidenced by the height of the surface peak, in Fig. 3, after the 1000 C, 10 s anneal.
Fig. 3. Glancing exit RBS channelling results for 10 s anneal.
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J.A. Sharp et al. / Nucl. Instr. and Meth. in Phys. Res. B 237 (2005) 93–97
It is only after annealing at 1100 C for 10 s that the amorphous layer appears to have re-grown completely. The literature [6,7] suggests that boron enhances the re-growth of amorphous layers, even at low temperatures. Here, the re-growth seems to be slow; it may be that the bromine is retarding the amorphous re-growth. Fluorine has been shown to retard the re-growth of amorphous layers implanted with boron [6]; it is possible that bromine retards the re-growth too since bromine shares the same group in the periodic table. The RBS data agrees with the Hall data, shown in Fig. 1. Here it was shown that the electrical activation values for the BBr2 implants were only comparable with those for the fluoride and chloride at temperatures above 1000 C. The RBS data reveals that the damage introduced by implanting BBrþ 2 is only removed above 1000 C, and this coincides with the observed increase in electrical activation. Fig. 4, takes data from the region of the RBS random and channelled spectra where the bromine distribution is observed. The backscattered yield in the channelled spectrum is only due to bromine atoms in interstitial sites, whereas the random spectrum shows all the bromine atoms, thus the number of substitutional bromine atoms can be calculated. Fig. 4 shows the percentage of bromine atoms in interstitial and substitutional sites as a function of annealing temperature. The results show that after implantation there are a small number of bromine atoms on substitutional lattice sites. For annealing temperatures of P700 C the percentage of bromine atoms in substitutional sites increases, with 40% being substitutional after annealing at Interstitial and substitutional percentage bromine after 10 second anneal, from glancing incidence Percentage
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%
Substitutional Interstitial
1050 C. There is very little change in the interstitial fraction of bromine after annealing at 600 C. This coincides with the relatively small amount of re-growth seen at this temperature. 4. Conclusion Hall effect measurement results show that the molecular implants of BBr2 and BCl2 do not enhance the electrical activation of boron to the same extent as BF2 implants. The BBr2 implants are only comparable with boron at 1100 C for the 1 · 1015 dose, and above 1000 C for the 2 · 1014 dose. The BF2 implants consistently show the highest activation. The BCl2 implants show slightly improved electrical activation with respect to boron only implants. The BBr2 implants show the lowest activation over most of the annealing temperature range, however at the highest annealing temperature they show higher activation than B. Rutherford backscattering results show that BBr2 implants amorphise the silicon surface. This amorphous region re-grows during subsequent annealing. However, the implant damage is not removed completely until 1100 C where the highest electrical activation is also observed. RBS channelling results show that a small fraction of bromine atoms take up substitutional sites in the silicon lattice during implantation. This fraction increases after annealing at 700 C and above. Acknowledgements The authors would to thank the UK Engineering and Physical Sciences Research Council (EPSRC) for supporting the project. J.A.S. and J.J.H. are supported by EPSRC Doctoral Training Awards. They would also like to thank V.F. Power and A. Smith for their assistance in the experimental procedures. References
as- 600 700 800 900 1000 1050 1100 imp Anneal temperature
Fig. 4. Substitutional fraction of bromine after annealing for 10 s, from glancing exit incidence.
[1] International Technology Roadmap for Semiconductors, 2003. [2] T.H. Huang, H. Kinoshita, D.L. Kwong, Influence of fluorine pre-amorphization on the diffusion and activation
J.A. Sharp et al. / Nucl. Instr. and Meth. in Phys. Res. B 237 (2005) 93–97 of low-energy implanted boron during rapid thermal annealing, Appl. Phys. Lett. 65 (14) (1994) 1829. [3] S. Ganguly, Comparison of low energy BF2+, BCl2+ and BBr2+ implants for the fabrication of ultrashallow P ± N junctions, J. Appl. Phys. 91 (4) (2001) 2023. [4] N. Barradas, R.P. Webb, C. Jeynes, Simulated annealing analysis of Rutherford backscattering data, Appl. Phys. Lett. 71 (1997) 291. [5] S.H. Winston, R.M. Gwilliam, B.J. Sealy, G. Boudreault, C. Jeynes, R.P. Webb, K.J. Kirkby, Evaluation of the boron
97
activation and depth distribution using BBrþ 2 implants, in: 2002 14th International Conference on Ion Implantation Technology Proceedings, IEEE Cat. No. 02EX505, 2003, p. 115. [6] G. Olson, Kinetics and mechanisms of solid phase epitaxy and competitive process in silicon, Mat. Res. Soc. Symp. Proc. 35 (1985) 25. [7] E.J.H. Collart, Advanced front-end processes for the 45 nm CMOS technology node, Mater. Sci. Eng. B (2004).
Comparison of elemental boron and boron halide implants into silicon J.A. Sharp *, R.M. Gwilliam, B.J. Sealy, C. Jeynes, J.J. Hamilton, K.J. Kirkby Surrey Ion Beam Centre, Advanced Technology Institute School of Electronics and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK Available online 24 June 2005
Abstract This paper investigates the electrical activation of boron halide molecular implants into silicon and compares them þ þ to boron implants at the same effective energy. The implanted species: B+, BFþ 2 , BCl2 and BBr2 were implanted to doses of 2 · 1014 and 1 · 1015 B cm2 the energy of the molecular implants was calculated to give an effective boron implant energy of 5 keV. Samples cut from the wafers were annealed for 30 s at temperatures ranging from 800 C to 1100 C. Hall effect measurements were used to compare and contrast the electrical activation of the boron between þ the different halide species and doses. It was found that molecular implants of BBrþ 2 and BCl2 do not enhance the elecþ trical activation of boron to the same extent that BFþ implants do. The BBr implants are only comparable with boron 2 2 after annealing at high temperatures (above 1000 C). The BFþ implants show enhanced electrical activation with 2 respect to boron for all the annealing temperatures and doses studied. 15 Rutherford backscattering spectroscopy (RBS) of silicon implanted with BBrþ boron 2 to a dose of 1 · 10 atoms cm2, shows that an amorphous region is created during the implantation. This region fully re-grows after annealing at 1100 C; lower temperature anneals remove only part of the amorphous layer. RBS channelling shows that a fraction of the bromine takes up substitutional lattice sites upon implantation, and that this fraction increases as the samples are annealed at temperatures above 600 C with 40% of the B being in substitutional sites after annealing at 1050 C. 2005 Elsevier B.V. All rights reserved. PACS: 61.72.Tt; 81.15.Np Keywords: Semiconductors; Boron; Shallow-junctions; Activation; RBS
*
Corresponding author. Tel.: +44 1483 686 093; fax: +44 1483 689 404. E-mail address: [email protected] (J.A. Sharp).
0168-583X/$ - see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.04.084
94
J.A. Sharp et al. / Nucl. Instr. and Meth. in Phys. Res. B 237 (2005) 93–97
1. Introduction Complementary Metal oxide semiconductor (CMOS) transistors are the building blocks of silicon chips. Shrinking device dimensions has the most beneficial effect on performance in terms of speed and efficiency. For ultra shallow-junctions the International Technology Roadmap for Semiconductors (ITRS) [1] requires that the depth of the individual transistors should shrink as well as the area they occupy, so that junction depths of <20.4 nm will be required for technology nodes of 90 nm and beyond [1]. In order to achieve shallower implants using ion implantation, new low energy implanters can be used, but these require significant investment. An alternative is to implant molecular ions containing the required dopant (in this case boron) with other heavier atoms. Currently, molecular boron difluoride (BFþ 2 ) is often used for boron doping, especially since the coimplantation of fluorine appears to have a beneficial effect on the electrical activation of boron [2], although there are some reports that it can also damage the gate oxide [3]. In the same group in the periodic table as fluorine are chlorine and bromine. These halide elements are heavier than fluorine; therefore shallower implants can be achieved at similar implant energies. The work carried out here is to evaluate the suitability of these heavier halide elements as molecular implants with boron þ (BClþ 2 , BBr2 ) into crystalline silicon. Comparisons of the electrical characteristics of these implants with standard B and BFþ 2 implants have been carried out after rapid thermal annealing using Hall effect measurements. Rutherford backscattering spectroscopy (RBS) has been used to investigate the both the damage and bromine depth distributions in the BBrþ 2 samples.
2. Experimental Czochralski grown 100 mm (1 0 0) n-type silicon wafers have been implanted with boron, BFþ 2, þ BClþ or BBr using a 200 kV Danfysik DF1090 2 2 ion implanter. The sources were BF3 (gas), BCl3 (liquid-gas) and BBr3 (liquid), respectively. Two doses of 2 · 1014 and 1 · 1015 boron atoms cm2
were investigated. The energies used for the boron halide molecular implants give an effective energy for the boron implant of 5 keV. The energies for the halide implants are as follows: B ¼ 5 keV; BFþ 2 ¼ 22.6 keV; BClþ 2 ¼ 37.8 keV; BBrþ 2 ¼ 78.9 keV. Rapid thermal annealing (RTA) was carried out on these samples using the Process Products Corporation 18 lamp RTA machine. A 30 s isochronal study was carried out from 800 C to 1100 C. A 350 C, 1 min stabilisation step was used prior to ramping up to the designated temperatures. Hall effect measurements were made to determine the carrier concentration and hence the percentage electrical activation of the boron, using an Accent HL5500 Hall effect measurement apparatus. Rutherford backscattering spectroscopy (RBS) was carried out using 1.5 MeV He+ ions using the high voltage engineering tandetron tandem accelerator. The samples used for RBS had been annealed in the temperature range 600– 1100 C, for times of 10 and 100 s. Data was collected with the sample in a random orientation, ion channelling was also used in both normal and glancing exit (45) modes. Subsequent to RBS analysis the DataFurnace [4] was used to analyse the data.
3. Results and discussion 3.1. Electrical activation Figs. 1 and 2 show, respectively, the percentage of electrically active boron atoms for the samples implanted with 1 · 1015 B cm2 and 2 · 1014 B cm2 boron doses for samples annealed in the range 800–1100 C for a time of 30 s. Fig. 1 (for dose of 1 · 1015 B cm2) shows that as the anneal temperature increases, the electrical activation of the boron increases. The range of the activation is from 5% for the lowest (B), up to 100% for the highest (BF2). The BF2 implant, as expected from the literature [5,2], shows the
J.A. Sharp et al. / Nucl. Instr. and Meth. in Phys. Res. B 237 (2005) 93–97 Percentage electrical activation of B for 1e15 dose
% activation
100 80
B BF2 BCl2 BBr2
60 40 20 0 800
900
1000
1050
1100
Anneal temperature (degrees C)
Fig. 1. Percentage electrical 1 · 1015 atoms cm2 dose.
activation
of
boron,
for
Percentage electrical activation of B for 2e14 dose 120
% activation
100
95
800 C. This trend is also apparent in the BBr2 implant. The BBr2 implant follows BCl2 much more closely at this lower dose. The range of activation is between 5% and 100%, similar to those for the high doses, although when comparing the two sets of data the higher dose normally shows the higher activation. This does not hold for the BBr2 implants, where the lower dose always shows the greater activation of the boron. This may be due to the extra damage introduced by the 1 · 1015 dose, which will take longer to anneal out. It could also be caused by solid solubility issues relating to the bromine and the increased strain that occurs for the higher dose in accommodating the bromine into the silicon lattice. 3.2. RBS results
80
B BF2 BCl2 BBr2
60 40 20 0 800
900
1000
1050
1100
Anneal temperature (degrees C)
Fig. 2. Percentage electrical 2 · 1014 atoms cm2 dose.
activation
of
boron,
for
highest activation, the BCl2 implant also achieves higher activation than the boron only implant. A peak in electrical activation for the BF2 and BCl2 implants is observed at 1050 C. The BF2 curve shows activation above 100%. This may be within the error bars for the measurements, but may also be caused by a slight error in the implant fluence i.e. slightly above 1 · 1015 ions cm2. The hall scattering factor my also be a reason for the slightly high carrier concentration. The activation of the BBrþ 2 implant is generally below that of the boron implant. The only temperatures where it is greater than the boron implant is at the very lowest and highest temperatures, a trend which can also be seen with the lower dose results below (Fig. 2). The results for the lower dose implants show almost exactly the same trends as those for the higher doses. BF2 again shows the highest activation with a peak at 1050 C. For this lower dose, the BCl2 implant only achieves activation greater than the boron implant above 1050 C, and at
Fig. 3 shows the glancing exit RBS ion channelling results in the region corresponding to the silicon surface for samples implanted with BBrþ 2 of 1 · 1015 B cm2 and annealed in the temperature range 600–1100 C for a time of 10 s, the as implanted spectrum is also shown for comparison. After implantation the channelled spectra shows that the silicon surface region has been amorphised to a depth of 60 nm. When the sample is annealed for 10 s, at 600 C anneal a small amount of regrowth occurs. More re-growth is seen after the 700 C, 10 s anneal. Even after annealing at 800 C, 900 C and 1000 C, this layer has not totally re-grown as evidenced by the height of the surface peak, in Fig. 3, after the 1000 C, 10 s anneal.
Fig. 3. Glancing exit RBS channelling results for 10 s anneal.
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J.A. Sharp et al. / Nucl. Instr. and Meth. in Phys. Res. B 237 (2005) 93–97
It is only after annealing at 1100 C for 10 s that the amorphous layer appears to have re-grown completely. The literature [6,7] suggests that boron enhances the re-growth of amorphous layers, even at low temperatures. Here, the re-growth seems to be slow; it may be that the bromine is retarding the amorphous re-growth. Fluorine has been shown to retard the re-growth of amorphous layers implanted with boron [6]; it is possible that bromine retards the re-growth too since bromine shares the same group in the periodic table. The RBS data agrees with the Hall data, shown in Fig. 1. Here it was shown that the electrical activation values for the BBr2 implants were only comparable with those for the fluoride and chloride at temperatures above 1000 C. The RBS data reveals that the damage introduced by implanting BBrþ 2 is only removed above 1000 C, and this coincides with the observed increase in electrical activation. Fig. 4, takes data from the region of the RBS random and channelled spectra where the bromine distribution is observed. The backscattered yield in the channelled spectrum is only due to bromine atoms in interstitial sites, whereas the random spectrum shows all the bromine atoms, thus the number of substitutional bromine atoms can be calculated. Fig. 4 shows the percentage of bromine atoms in interstitial and substitutional sites as a function of annealing temperature. The results show that after implantation there are a small number of bromine atoms on substitutional lattice sites. For annealing temperatures of P700 C the percentage of bromine atoms in substitutional sites increases, with 40% being substitutional after annealing at Interstitial and substitutional percentage bromine after 10 second anneal, from glancing incidence Percentage
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%
Substitutional Interstitial
1050 C. There is very little change in the interstitial fraction of bromine after annealing at 600 C. This coincides with the relatively small amount of re-growth seen at this temperature. 4. Conclusion Hall effect measurement results show that the molecular implants of BBr2 and BCl2 do not enhance the electrical activation of boron to the same extent as BF2 implants. The BBr2 implants are only comparable with boron at 1100 C for the 1 · 1015 dose, and above 1000 C for the 2 · 1014 dose. The BF2 implants consistently show the highest activation. The BCl2 implants show slightly improved electrical activation with respect to boron only implants. The BBr2 implants show the lowest activation over most of the annealing temperature range, however at the highest annealing temperature they show higher activation than B. Rutherford backscattering results show that BBr2 implants amorphise the silicon surface. This amorphous region re-grows during subsequent annealing. However, the implant damage is not removed completely until 1100 C where the highest electrical activation is also observed. RBS channelling results show that a small fraction of bromine atoms take up substitutional sites in the silicon lattice during implantation. This fraction increases after annealing at 700 C and above. Acknowledgements The authors would to thank the UK Engineering and Physical Sciences Research Council (EPSRC) for supporting the project. J.A.S. and J.J.H. are supported by EPSRC Doctoral Training Awards. They would also like to thank V.F. Power and A. Smith for their assistance in the experimental procedures. References
as- 600 700 800 900 1000 1050 1100 imp Anneal temperature
Fig. 4. Substitutional fraction of bromine after annealing for 10 s, from glancing exit incidence.
[1] International Technology Roadmap for Semiconductors, 2003. [2] T.H. Huang, H. Kinoshita, D.L. Kwong, Influence of fluorine pre-amorphization on the diffusion and activation
J.A. Sharp et al. / Nucl. Instr. and Meth. in Phys. Res. B 237 (2005) 93–97 of low-energy implanted boron during rapid thermal annealing, Appl. Phys. Lett. 65 (14) (1994) 1829. [3] S. Ganguly, Comparison of low energy BF2+, BCl2+ and BBr2+ implants for the fabrication of ultrashallow P ± N junctions, J. Appl. Phys. 91 (4) (2001) 2023. [4] N. Barradas, R.P. Webb, C. Jeynes, Simulated annealing analysis of Rutherford backscattering data, Appl. Phys. Lett. 71 (1997) 291. [5] S.H. Winston, R.M. Gwilliam, B.J. Sealy, G. Boudreault, C. Jeynes, R.P. Webb, K.J. Kirkby, Evaluation of the boron
97
activation and depth distribution using BBrþ 2 implants, in: 2002 14th International Conference on Ion Implantation Technology Proceedings, IEEE Cat. No. 02EX505, 2003, p. 115. [6] G. Olson, Kinetics and mechanisms of solid phase epitaxy and competitive process in silicon, Mat. Res. Soc. Symp. Proc. 35 (1985) 25. [7] E.J.H. Collart, Advanced front-end processes for the 45 nm CMOS technology node, Mater. Sci. Eng. B (2004).