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

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MEIS MEIS yield yield (cts (cts / / 5µ 5µ C) C) MEIS MEIS yield yield (cts (cts / / 5µ 5µ C) C) 100 10 1 10 1 Displaced Si 0 5 10 As Si recoils Si vac's 0 5 10 Starting with the As range distributions (bottom), TRIM (26) calculations show that the maximum of the As profile in a pure Si matrix is expected to occur at a depth of approximately 5 nm (Rp = 5.5 nm) and hence its maximum range (~3 × Rp,) and associated damage might extend to ∼16 nm. The TRIM calculated profile is shown adjacent to that measured by MEIS after an As dose of 4 × 10 14 cm -2 . At or above this dose the agreement is very good for depths greater than Rp. Since TRIM provides 109 3e13-virg 9e13-virg 4e14-virg 1.5e15-virg 1.8e15-virg virgin Si 3e13 9e13 4e14 1.5e15 1.8e15 As TRIM 10 23 10 23 10 22 10 22 10 21 10 21 10 21 10 21 10 20 10 20 Depth (nm) Si conc (cm-3 Si conc (cm ) -3 ) As conc (cm-3 As conc (cm ) -3 ) Figure 5.2 Depth profiles of displaced Si and As implant atoms obtained from the MEIS energy spectra in Figure 5.1. TRIM calculated Si vacancy and recoil distributions and the As implant profile are shown for comparison. The dose dependent peak position of the As implant is indicated by arrows.
essentially a “zero dose” profile in a randomised solid, agreement with a low dose implant profile may be expected, provided that the Si matrix is amorphised. Figure 5.1 shows that this is the case for doses above 9 × 10 13 cm -2 , as evidenced by the Si damage peak reaching random level close to the surface, however this is not the case for the lowest dose investigated of 3 × 10 13 cm -2 . The development of depth profiles of displaced Si in Figure 5.2 suggests that the Si damage build up involves two distinct phases that partly overlap, i.e. an initial growth of disorder near to the oxide /Si interface until a ∼4 nm wide amorphous layer centred at a depth of ∼3.5 nm is completed, followed by the planar growth of the amorphous layer from the surface inwards, until for doses above 1.5 × 10 15 cm -2 the amorphous layer approaches a saturation depth of ∼10 nm. The increase in the thickness of the amorphous layer also causes the dechannelling level to rise, as is seen in Figure 5.1. The observed damage evolution behaviour cannot be explained in terms of the heterogeneous nucleation model of amorphous phase formation at room temperature (7- 10). In this model the energy deposition in the collision cascade is sufficiently dense to produce small amorphous zones (either in a single collision cascade or via cascade overlap) and these zones once they spatially overlap at a certain dose, effect a lattice phase change. Accordingly, the build up of displaced atoms would be expected to follow the shape of the energy deposition function as is given by vacancy and interstitial profiles produced by the implant ion. These profiles, again calculated by TRIM, are added to the top of Figure 5.2 showing the Si damage distributions, using arbitrary units but the same logarithmic scale. The two profiles are spatially close together and have their maxima at shallower depths than the TRIM calculated As profile in the bottom of Figure 5.2, as expected. It is clear that the growth of the disordered / amorphous Si layer does not coincide with the maximum in the energy deposition rate; in fact the damage profile for the lowest As implant dose is appreciably shallower than the calculated profiles. It appears that for a shallow As implant, initially at low doses, a highly damaged/amorphous 4 nm wide (FWHM) near-surface layer builds up, nucleated at the oxide/Si interface. No deeper damage is observed at this stage and this suggests that a fraction of the point defects produced at greater depths annihilate in dynamic annealing processes during the cascade. This behaviour is similar to that observed in previous MEIS studies for ULE B + implants into Si (19, 20) which showed the development of a 3–4 nm wide near-surface, highly damaged/amorphised layer, independent of implant energy up to 2 keV at room temperature. The formation of this layer was ascribed to the action of the oxide / Si interface as a sink for interstitials that are generated along the 110
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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
Page 77 and 78: ⎛ 〈 C ⎞ ⎛ ⎞ I 〉 〈 C V
Page 79 and 80: 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: Yield (counts per 5 µC) 250 200 15
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 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
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Yield (counts per 5 µC) 450 400 35
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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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