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

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The above observation by MEIS of the correlation between the planar growth of the amorphous layer and the movement of the As peak to greater depth with increasing dose, implies that most of the dopant that initially came to rest beyond Rp, migrates towards, on average, shallower depths, back into the growing, highly disordered/ amorphous layer in which it is more readily accommodated than in the still crystalline material. This movement is possibly initiated or occurs during the quenching stage of the cascade and is likely to be point defect mediated. The combined damage evolution and dopant movement behaviour observed for shallow As implants is, in most respects, replicated for the even heavier Sb ion, implanted at 2 keV into Si at room temperature. Sb with a mass of 121 amu compared to As 75 amu, is expected to show reduced straggle and should in principle give better defined implant profiles. Whereas As is believed to diffuse either through an interstitial or vacancy assisted mechanism, Sb diffuses exclusively through the latter (28). Figure 5.4 shows the dependence of the MEIS spectra on the Sb dose, over the range from 1×10 14 cm -2 to 5×10 15 cm -2 . All implants were again carried out at room temperature. As before the spectrum for the virgin Si surface and the random spectrum are shown for reference and the peaks due to scattering off implanted Sb, surface Si and O are marked. The expected reduced straggling shows itself in the steeper down slope of the deep edge of the Sb implant profile compared to the equivalent region of the As profile shown in Figure 5.1. The development of the Sb scattering peak as a function of dose indicates a peak shift to greater depths, similar to that seen for As. The lowest implanted Sb dose of 1×10 14 cm -2 has already produced a fully amorphised near surface layer as demonstrated by attainment of the Si random level in the MEIS peaks. For increasing Sb dose this layer shows a planar growth to greater depth, again akin to that found above for As. The growth in width of the near-surface amorphous layer also causes the increased dechanneling level seen in the spectra for high Sb doses. For the highest dose of 5 × 10 15 cm -2 a dilution of the Si peak is observed that manifests itself in a dip in the displaced Si signal. This is caused by the unusual growth of the oxide thickness, in combination with the high Sb concentration. The oxide layer grows from a width of 2 nm at a dose of 3×10 15 cm -2 to 4 nm at 5 × 10 15 cm -2 . This observation and other MEIS results (not shown) appear to indicate that a high Sb implant concentration at shallow depths promotes the growth of the oxide layer to depths well beyond that of the native oxide. 113
yield (cts / 5µC) 500 400 300 200 100 virgin Random 7E13 5E14 1E15 3E15 5E15 O Si edge 0 145 150 155 160 165 170 175 180 185 190 195 Energy (keV) Figure 5.4 MEIS energy spectra showing the growth of the Si damage and Sb dopant yield as a function of fluence for 2 keV Sb + ion implantation into virgin Si at room temperature. The combined behaviour of the displaced Si and the implanted Sb dopant depth profiles is shown in Figure 5.5, as before using a common depth scale and logarithmic concentration scales. Here too the displaced Si profiles are those obtained after subtraction of the virgin Si spectrum and hence represent the additional disorder generated by the Sb implant at each dose indicated. The TRIM calculated vacancy distribution has been added to the top part of the figure as a representation of the energy deposition function. Equally the calculated Sb implant profile is added to the bottom of the figure, adjusted to the height of the profile for the dose of 5 × 10 14 cm -2 . The amorphous layer produced for the lowest implant dose investigated of 1 × 10 14 cm -2 , extends to a depth of ~5 nm (half height) and the shape of the disordered layer produced at this stage, not surprisingly, coincides with the energy deposition profile for depths beyond Rp. The half height of the down slope of the Sb distribution for this implanted dose also occurs approximately at this depth. Yet the actual implanted Sb distribution should extend to a greater depth as shown by the TRIM calculated Sb profile. Just as was seen for the As, Sb ions implanted with a Rp of 5 nm having a maximum range of at least twice that figure, migrate out of the as yet not amorphised deeper layer in which 114 Sb
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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
Page 81 and 82: 67 H. Bracht. Diffusion Mechanism a
Page 83 and 84: Hall effect measurements were carri
Page 85 and 86: energy than one scattered from an a
Page 87 and 88: epresents a small improvement over
Page 89 and 90: (dE/dx)out multiplied by the path l
Page 91 and 92: they are small compared to the diff
Page 93 and 94: ackscattering (27). This fact forms
Page 95 and 96: Figure 4.7 a) Plot of a Gaussian di
Page 97 and 98: similar to the width of the error f
Page 99 and 100: UP Ion Beam SPIN Rotation Sample Sc
Page 101 and 102: Kinematic factor (K) 1.0 0.8 0.6 0.
Page 103 and 104: 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: no longer “visible” in MEIS has
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 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
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ecomes steeper for the sample annea
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Figure 6.28 Schematic illustrations
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and the 2D picture in Figure 6.31b)
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6.5 Conclusion In summary, in this
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20 L. Capello, T. H. Metzger, M. We
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egarding B profiles relevant to the
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Yield (counts per 5 µC) 400 300 20
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TRIM AU 0.04 0.03 0.02 0.01 TRIM si
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a) F profile PAI 3 keV BF2 b) F pro
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Yield (counts per 5 µC) 20 15 10 5
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the corresponding PAI sample, yield
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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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