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

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The slower, or initially delayed, regrowth on SOI is also apparent with these samples. It is most noticeable with the samples annealed for 50s. For the SOI sample, regrowth to a depth around 20 nm has occurred but the bulk sample has regrown to a depth of approximately 6 nm. The samples annealed for 200s also show a large difference in the amount of damage regrowth between SOI and bulk Si. The samples annealed for 70s appear to show a similar level of regrowth between bulk Si and SOI. However for both samples the a/c interface is at a depth where there is a high As concentration and hence the regrowth rate is very slow. The bulk sample has regrown by an extra 2nm compared to the SOI sample. With the regrowth rate so low in this area this is a significant difference in depth. Indeed the depth of the a/c interface of the bulk Si sample annealed for 70s is close to the depth of the SOI sample annealed for 200s. 6.4.4 Discussion Before the regrowth mechanisms can be considered it is important to discuss the detail of the a/c interfaces. In Figure 6.28a) and b) are 2D schematic illustrations showing entirely different possible damage scenarios. In these illustrations black represents fully amorphous Si and white represents fully crystalline Si. Different levels of shading of grey represent different levels of damage between amorphous and crystalline. The right hand side of each illustration represents the surface. The approximate shape of the idealised MEIS profile (ignoring energy straggling and system resolution convolution) is given underneath each image. Figure 6.28a) illustrates a situation where there is a gradual transition from the crystalline region with increasing damage until an amorphous layer is reached. In Figure 6.28b) a sharp wavy interface between fully crystalline and fully amorphous Si is presented. Both scenarios would produce a similar shape in a MEIS profile, hence MEIS alone cannot distinguish between them. To determine the profile XTEM was carried out on the 60 nm SOI sample, preamorphised, implanted with 3keV As to 1E15 cm -2 , and annealed at 550 °C for 600s (MEIS result Figure 6.25a)). The result is shown in Figure 6.29. It shows that the a/c interface is indeed wavy in an irregular fashion, over a depth range of ~ 14 nm. This in excellent agreement with the depth range of the a/c interface from MEIS results. 165
Figure 6.28 Schematic illustrations of possible damage scenarios with the associated idealised MEIS profile. Figure 6.29 TEM image from a sample on 60 nm SOI, PAI, 3 keV As and annealed at 550 °C for 600s. Analysing the differences observed between the annealing of bulk Si and SOI, the most likely explanation is based on the accumulation of localised damage areas at the buried oxide interface, removing the crystal seed for the regrowth to proceed from in patches. In this section the disorder produced at the BOX is considered for the different studies presented. TRIM results for a 3 keV As implant are shown in Figure 6.30. The calculated As depth profile along with the vacancy and interstitial depth profiles are shown in Figure 6.30a) whilst a 2D pictorial representation of the calculation is shown in Figure 166
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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
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
Page 179 and 180: Yield (counts per 5 µC) 450 400 35
Page 181 and 182: The higher temperature anneals carr
Page 183: ecomes steeper for the sample annea
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 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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