Damage formation and annealing studies of low energy ion implants ...

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the bulk Si becomes wavy in the early stages. This wavy-ness is retained for the full regrowth and this may explain the XTEM and MEIS results. This initial formation of the wavy layer is the probable reason for the SOI samples lagging behind the bulk Si in terms of the amount of regrowth that occurs for the same anneal duration. The proposed mechanism is illustrated schematically in Figure 6.32 for one such region. Figure 6.32 Illustration of proposed regrowth mechanism on SOI wafers. Once the leading edge of the interface reaches a depth where there is a high As concentration, regrowth slows down effectively allowing the back edge to catch up. This causes the straightening up of the interface as is observed by MEIS. Arsenic atoms that cannot be accommodated as areas of the a/c interface pass by are pushed into neighbouring amorphous areas, explaining why there is less modification of the As peak at depths where there has been some recrystallisation. A previous RBS study of samples where an amorphous Si was deposited on a layer containing at least one atomic layer of native oxide showed that upon annealing the height of the RBS peak from the amorphous Si was reduced but not the width (27). Columnar regrowth of the Si above regions where at isolated points crystal growth centres occur, most likely at gaps of the oxide layer, was suggested (27). This is consistent with the proposed mechanism in the sense that regrowth could occur selectively above small areas of seed and not above other areas without seed. If an implant produced an amorphous layer to the BOX, then random nucleation and growth would be expected (28, 29). 169
6.5 Conclusion In summary, in this chapter a range of studies of the effects of annealing on As implanted Si are presented. In the first section results are presented for annealing conditions similar to those currently used for device manufacturing, e.g. > 1000 °C spike annealing. MEIS results shows the effect of annealing causing recrystallisation of the implanted layers. The effect of As segregation is visible in the MEIS spectra. MEIS was used as the starting point for the interpretation of specular reflectivity results, the results of which suggested that the segregated As is narrower than that measured in MEIS. MEIS results showed that the segregated As is located underneath the oxide layer. SIMS measurements showed that As which becomes invisible in the MEIS spectra following annealing is retained and hence must represent As atoms in substitutional lattice positions. SIMS also shows that diffusion of As deeper into the bulk is a feature of this type of annealing. It was shown that diffusion played a more significant role in determining the final junction depth than the implant energy. Studies of the effect of using lower annealing temperatures have been carried out. Layer-by-layer SPER regrowth has been observed. During SPER, As takes up substitutional lattice sites and any that can’t be accommodated segregates in front of the advancing amorphous / crystalline interface. Importantly, diffusion deeper into the bulk was not observed with this annealing temperature range. Comparisons between MEIS and XRD have shown how MEIS can be used to interpret XRD results. The results of the two techniques in terms of the measured regrown layer thickness are in excellent agreement. Finally unusual regrowth of SOI wafers was observed. For conditions where a recoiled interstitials reached, or were close to, the buried oxide interface, a broad amorphous / crystalline interface was observed. This is attributed to the damage causing regions of imperfect crystalline seed for the regrowth to proceed from. References 1 http://public.itrs.net/ (accessed 12/1.06). 2 R. Lindsay, B.J. Pawlak, P. Stolk, K. Maex. Proceedings of MRS vol 717, p 65 3 T. Feudel, M. Horstmann, M. Gerhardt, M. Herden, L. Herrmann, D. Gehre, Ch. Krueger, D. Greenlaw, M. Raab. Mat. Sci. in Semiconductor Processing 7 (2004) 369–374. 170
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Damage formation and annealing stud
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3.2.2.6 Other models 40 3.2.3 Other
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Chapter 7 Interaction between Xe, F
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List of Figures Figure 1.1 a) Schem
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Figure 4.13 Variation in the kinema
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Figure 6.10 MEIS energy spectra for
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Figure 7.8 Combined MEIS Xe depth p
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Abbreviations and Symbols a/c amorp
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Abstract The work described in this
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Chapter 7 5 M. Werner, J.A. van den
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terminal (Vg), current cannot flow
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This is an approximate average leve
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the active channel, adjacent to the
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To continue to improve devices ther
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produces a device quality regrown l
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technique of channelling Rutherford
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22 J.S Williams. Solid Phase Recrys
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and the probability of scattering t
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importance for many atomic collisio
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M1, V0, E0 Figure 2.2 Elastic scatt
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2.3.1 Models for inelastic energy l
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dE/dx (ev/Ang) 10 1 Inelastic Energ
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dE/dx (eV/Ang) 125 100 75 50 25 0 2
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Figure 2.5 Results of TRIM simulati
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Chapter 3 Damage and Annealing proc
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the Si/SiO2 interface, consuming th
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On the basis that by creating an in
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Figure 3.4 Structure of crystalline
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a Si atom will suffer little angula
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3.2.2.5 Homogeneous model (Critical
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Sputtering and atomic mixing play a
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and is approximately 25 times faste
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elevant dopants later. For equal co
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nearest neighbour distance (52). By
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Category I defects are produced whe
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thermal annealing (600 - 700 °C an
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Figure 3.11 Relationship between im
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defect pairs due to Coulomb attract
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⎛ 〈 C ⎞ ⎛ ⎞ I 〉 〈 C V
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27 R.D. Goldberg, J. S. Williams, a
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67 H. Bracht. Diffusion Mechanism a
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Hall effect measurements were carri
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energy than one scattered from an a
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epresents a small improvement over
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(dE/dx)out multiplied by the path l
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they are small compared to the diff
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ackscattering (27). This fact forms
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Figure 4.7 a) Plot of a Gaussian di
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similar to the width of the error f
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UP Ion Beam SPIN Rotation Sample Sc
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Kinematic factor (K) 1.0 0.8 0.6 0.
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Figure 4.14 Illustration of the dou
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4.2.2.4 Interpretation of spectra A
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with are comparatively small, ~ 0.5
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Inelastic energy loss (eV/Ang) 32 2
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iterative procedure is carried out
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Yield (couts per 5µC) 300 250 200
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SIMS experiments were also carried
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MEIS, using the scattering conditio
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4.5 Sample production Samples have
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an N2/O2 environment to maintain an
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38 M. Anderle, M. Barozzi, M. Bersa
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damage evolution behaviour observed
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Yield (counts per 5 µC) 250 200 15
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essentially a “zero dose” profi
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no longer “visible” in MEIS has
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yield (cts / 5µC) 500 400 300 200
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5.4 Conclusion MEIS analysis with a
Page 137 and 138: Chapter 6 Annealing studies 6.1 Int
Page 139 and 140: 6.2.2.2 Results and Discussion Figu
Page 141 and 142: theory predictions and X-ray fluore
Page 143 and 144: implantation conditions are those u
Page 145 and 146: a) b) c) Yield (counts per 5 µC) Y
Page 147 and 148: greater than MEIS. SIMS is not sens
Page 149 and 150: attributed to the interference betw
Page 151 and 152: The as-implanted sample, with a bro
Page 153 and 154: a) b) Yield (counts per 5 µC) Yiel
Page 155 and 156: interface, as evidenced by the high
Page 157 and 158: duration, is observed. MEIS results
Page 159 and 160: Yield (counts per 5µC) 500 400 300
Page 161 and 162: ack edges of the Si peaks are very
Page 163 and 164: underneath the SiO2 layer, iii) it
Page 165 and 166: R s (Ω/sq) 950 900 850 800 750 60
Page 167 and 168: As concentration (at/cm 3 ) 1E22 1E
Page 169 and 170: R s (Ω/sq) 950 900 850 800 750 70
Page 171 and 172: Following annealing it was observed
Page 173 and 174: ∆a/a (x 10 -3 ) 4,0 epi550 3,5 3,
Page 175 and 176: Yield (counts per 5 uC) 350 300 250
Page 177 and 178: (FWHM). Concomitantly, As in the re
Page 179 and 180: Yield (counts per 5 µC) 450 400 35
Page 181 and 182: The higher temperature anneals carr
Page 183 and 184: ecomes steeper for the sample annea
Page 185 and 186: Figure 6.28 Schematic illustrations
Page 187: and the 2D picture in Figure 6.31b)
Page 191 and 192: 20 L. Capello, T. H. Metzger, M. We
Page 193 and 194: egarding B profiles relevant to the
Page 195 and 196: Yield (counts per 5 µC) 400 300 20
Page 197 and 198: TRIM AU 0.04 0.03 0.02 0.01 TRIM si
Page 199 and 200: a) F profile PAI 3 keV BF2 b) F pro
Page 201 and 202: Yield (counts per 5 µC) 20 15 10 5
Page 203 and 204: the corresponding PAI sample, yield
Page 205 and 206: amorphous matrix, (16) i.e. local c
Page 207 and 208: 21 M. Anderle, M. Bersani, D. Giube
Page 209 and 210: stopped at depths beyond the observ
Page 211: the role of each individual element
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