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

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a/c interface depth. Amount of visible As % of implant visible. as-impl 10.9 2.0E15 100 5s 7.4 1.74E15 87 10s 6.8 1.38E15 69 20s 6.2 1.35E15 68 30s 5.5 1.14E15 57 40s 5.2 1.07E15 54 60s 4.8 1.01E15 50 120 3.7 8.0E14 40 Table 6.3 Depths of the a/c interfaces and the amount of As visible in MEIS for the isothermal anneal series. In the centre section of Figure 6.11 is a graph showing the approximate regrowth rate inferred from these results. A simple consideration of the results reveals that the regrowth rate falls dramatically from its initial value as the concentration of the As peak increases and as the a/c interface reaches the surface. The regrowth rates are taken as an average value based on the distance between successive Si peaks and the time differences between them. The accuracy of this method is limited due to the changing time intervals, the instantaneous rate may vary quite quickly but this method assumes a constant regrowth rate over a period of 5s or longer. There may also be some acceleration of rate in a region of low As concentration (4, 23) which inevitably is averaged out. Additionally the ramping up and down introduces a small error in the timing which is obviously more pronounced with shorter durations. Nonetheless the trend seen provides a good illustration of the slowing down of the regrowth around the high As concentration and surface. From an initial estimated value in the region of 0.7 nms -1 (which will be < 1nm -1 for intrinsic Si (6), due to the overlapping over some depth in which the As concentration increases), it drops to ~ 0.065 nm s -1 where the local As concentration has its maximum concentration of ~ 3E21cm -3 . It slows down further in the region of the surface to ~ 0.02 nms -1 . The relation between regrowth, segregation effects and substitutional behaviour can be illustrated by plotting the As, Si and O peaks on the same depth scale as shown in Figure 6.12 for the as-implanted, 10s, 60s and 120s samples. The O peaks have had the Si dechannelling level subtracted. It clearly shows the following observations already made, i) that the Si peak contains scattering from the Si atoms in the oxide layer and scattering of Si atoms around the As peak, ii) the segregated As peak is located 143
underneath the SiO2 layer, iii) it appears that some suboxides exists around the segregated As peak. yield (counts per 5 µC) 400 350 300 250 200 150 100 50 4000 350 300 250 200 150 100 50 a) as-implanted b) 600C 10s c) 600C 60s d) 600C 120s 0 0 2 4 6 8 10 12 14 Depth (nm) SIMS analysis was carried out at with 0.5 keV and 0.25 keV Cs + primary beams and no appreciable difference was observed between the two energies. The SIMS profiles for some of the annealed samples are shown in Figure 6.13a) using a logarithmic concentration scale and in Figure 6.13b) using a linear concentration scale. Note that the depth range is different in the two figures. A profile from an equivalent asimplanted sample is included in Figure 6.13a). Only minor differences are observed between the profiles of the annealed samples and this as-implanted case beyond the near surface, i.e. deeper diffusion does not occur. The lack of diffusion to greater depths is crucially important in determining the usefulness of this type of annealing for the production of shallow junctions. Figure 6.13 shows clearly that the As profiles are changed little upon annealing for concentrations below ~2E21 cm -3 . This concentration is of the order of the maximum solid solubility (21, 22). However clear changes for concentrations higher than 2E21 cm -3 do occur, which are most clearly seen in Figure 6.13b) which has a reduced depth range. SIMS profiles agree with the trend of the MEIS results in terms of the segregation of As that cannot be accommodated in the 144 As Si O 2 4 6 8 10 12 14 Figure 6.12 As, Si and O depth profiles for the 3 keV As implanted samples, as-implanted and following 600 °C annealing for different durations.
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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
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 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: ack edges of the Si peaks are very
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
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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