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

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durations with higher thermal budgets. The extra amount of diffused As seen in the SIMS profiles accounts for the variation in the amount of segregated As seen in MEIS. Concentration (at/cm 3 ) 1E22 1E21 1E20 1E19 1E18 1E17 1keV As, 2E15, PAI and NoPAI 0 10 20 30 40 50 60 PAI NoPAI Depth (nm) With respect to device production this experiment shows that a reduction in beam energy is less important in determining the junction depth than the diffusion. The depths of the 3 and 1 keV implants only vary by a few nm. This becomes much less significant when compared to the amount of diffusion, which in some cases was approximately 40nm. Note that the final junction depths of the 1 and 3 keV spike samples are not directly comparable in this study as they are at different temperatures. Using a 1 keV beam could be detrimental from the point of view of lower throughput, since lower beam currents are usually obtained with a 1 keV beam compared with 3keV due to space charge beam blow up effects. Solely changing anneal temperatures for spike annealing may result in less diffusion at the lower temperatures, but this doesn’t necessarily lead to an increased device performance due to overall processing effects (3). Returning to the results discussed in this section, a small growth in the oxide layer thickness to 2 nm occurs following implantation. As with previous experiments, the growth in thickness of the oxide layer, with increasing anneal temperature and/or 137 as-implanted 600C 20m 1000C 5s 1025C 10s 1050C spike 10 20 30 40 50 60 Figure 6.9 SIMS profiles for 1 keV As implanted samples, as-implanted and following various anneals.
duration, is observed. MEIS results have shown that the segregated As is located underneath the oxide layer. Figure 6.8 c) shows the O depth profiles for the NoPAI samples. The 0.6 nm increase in the oxide layer width is exactly replicated in the shift in depths of the As peaks of Figure 6.8a). It is likely from a simple consideration of the shape of the O peaks that the oxide layer contains some suboxides (15). The back edge of the peak is substantially less steep than the front edge and also less steep than the back edge of the corresponding Si peak plotted on the same depth scale in Figure 6.8d). This result again shows that the segregated As clearly sits underneath the SiO2 layer, although probably in a region of some suboxides. The Si is probably distorted around the segregated As and this is reflected in increased backscattering. 6.2.5 BF2 implanted samples Similar sets of experiments have been carried out using BF2 implanted samples. The regrowth is seen to proceed in the same way. Neither B nor F is visible in MEIS at the concentrations used; therefore the results are not presented here. However a novel effect involving the interaction between Xe, F and the defect structure was identified. This is the subject of chapter 7 of this thesis. 6.3 SPER studies 6.3.1 Introduction There is interest in studies of low temperature SPER, i.e. ~ 550 °C – 800 °C as this temperature range has been suggested as a possible solution for the formation of USJs in the 65 nm and 45 nm nodes (1-3). These temperatures are currently not used due to problems of lower electrical activation / solubility and a high level of defects left after annealing. However the real strength of this type of annealing is less diffusion, as the results in this section will corroborate. The first part of this section shows results of annealing a 3 keV As implanted wafer. An isothermal annealing series at 600 °C and an isochronal series for 10 s were carried out. MEIS results show the same effects as discussed before, i.e. segregation of As, with a fraction of As taking up substitutional positions and the movement of the a/c crystalline interface towards the surface in a layer by layer fashion. The As substitutionality is observed to follow the depth of the a/c interface. SIMS measurements show the same movement of As, seen in MEIS, and also show that the As invisible to MEIS is retained and importantly does not diffuse deeper into the bulk. 138
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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
Page 105 and 106: 4.2.2.4 Interpretation of spectra A
Page 107 and 108: with are comparatively small, ~ 0.5
Page 109 and 110: Inelastic energy loss (eV/Ang) 32 2
Page 111 and 112: iterative procedure is carried out
Page 113 and 114: Yield (couts per 5µC) 300 250 200
Page 115 and 116: SIMS experiments were also carried
Page 117 and 118: MEIS, using the scattering conditio
Page 119 and 120: 4.5 Sample production Samples have
Page 121 and 122: an N2/O2 environment to maintain an
Page 123 and 124: 38 M. Anderle, M. Barozzi, M. Bersa
Page 125 and 126: damage evolution behaviour observed
Page 127 and 128: Yield (counts per 5 µC) 250 200 15
Page 129 and 130: essentially a “zero dose” profi
Page 131 and 132: no longer “visible” in MEIS has
Page 133 and 134: yield (cts / 5µC) 500 400 300 200
Page 135 and 136: 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: interface, as evidenced by the high
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 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 188: and the 2D picture in Figure 6.31b)
Page 189 and 190: 6.5 Conclusion In summary, in this
Page 191 and 192: 20 L. Capello, T. H. Metzger, M. We
Page 193 and 194: egarding B profiles relevant to the
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
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21 M. Anderle, M. Bersani, D. Giube
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stopped at depths beyond the observ
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the role of each individual element
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