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

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yield (counts per 5µC) 100 80 60 40 20 0 3 keV As as-implanted. 100 keV He 111 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Depth (nm) 4.2.3.4 Changes to the data acquisition It is worth noting that during the course of the project changes were made to the data acquisition system. The detection efficiency has been altered at different stages of the project. For this reason some of the random levels differ over time and are not directly comparable. An appropriate random level for the operating set up is used with all data in this thesis. 4.3 SIMS introduction and basic principles SIMS is a surface analytical technique used in a wide range of experiments. This section contains a brief explanation of depth profiling using dynamic SIMS with particular attention to unusual aspects that cause deviations from the ideal profiles, referred to as SIMS artefacts. The technique operates by bombardment of the sample surface with a primary ion beam causing sputtering of particles, followed by mass spectrometry of the emitted secondary ions. Much of the SIMS used in this thesis was carried out at ITC – IRST, Trento, using a Cameca Wf SC Ultra instrument (36, 37). 95 Computer program surface approximation Figure 4.21 Example of the difference between depth spectra calibrated using the surface approximation method and the computer program for a 3 keV As as-implanted sample.
SIMS experiments were also carried out at IMEC, Belgium, using an Atomika 4500 instrument in each case conditions for these experiments are described. Unless otherwise stated, the SIMS measurements presented in this thesis were carried out at ITC – IRST. In a SIMS instrument an ion source is used to produce primary ions that are formed into a beam by an ion optical column. Often instruments have several different sources to allow a range of ions to be used. The most common primary beams to use are O2 + , O - , Ar + , and Cs + . Oxygen ion bombardment enhances the secondary ion yields of electropositive elements and produces more uniform erosion of the sample than inert gas bombardment. O2 + is the general purpose primary beam for semiconductor samples where sample charging is not a problem. For insulating samples when sample charging is a problem an electron flood gun can be used to neutralise the sample and sample charging can also be reduced using an O - beam. A beam of Cs + ions is generally used for optimum sensitivity with electronegative elements (6). In the present studies Cs + has been used to profile As and F, while O2 + was used for profiling B (38, 39). Ion optics allows the ions to be accelerated and focused into a small beam that can be rastered over an area of the sample. In these experiments a beam energy of around 4 – 6 keV was used, but the sample was biased to create an impact energy of 0.25 – 1 keV. The beam was rastered over an area of typically around 200 µm 2 and data recorded over an area of around 70 µm 2 depending on the particular experiment. Incidence angles of 44 – 76° were obtained in the Cameca, which depended on the impact energy. Normal incidence was used in the Atomika. Erosion rates of 0.2 – 0.9 Å/s were obtained (38, 39). Sputtered secondary ions are energy filtered. This is useful for removing interference of molecular species from an atomic species with the same mass. Secondary ions can then be mass analysed in a mass spectrometer before being detected. Either magnetic sector spectrometers or quadrupole analysers are used. Either positive or negative secondary ions can be monitored (6). Negative As and F ions and positive B ions were collected (38, 39). The number of ions sputtered from the surface of the sample provides a means for measuring the composition of the sample. The sputtering yield is not linearly related to the concentration of an element present in a sample since the secondary ion yield varies with element (e.g. As or B), with changes to the matrix, (such as going from SiO2 to Si) and varies with the primary bombarding species (6). The erosion rate is also not constant during the first couple of nm. Depth scales are often calibrated on the basis of the final crater depth measurement and assuming a constant erosion rate. The use of a 96
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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
Page 63 and 64: and is approximately 25 times faste
Page 65 and 66: elevant dopants later. For equal co
Page 67 and 68: nearest neighbour distance (52). By
Page 69 and 70: Category I defects are produced whe
Page 71 and 72: thermal annealing (600 - 700 °C an
Page 73 and 74: Figure 3.11 Relationship between im
Page 75 and 76: 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: Yield (couts per 5µC) 300 250 200
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 and 162: ack edges of the Si peaks are very
Page 163 and 164: underneath the SiO2 layer, iii) it
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R s (Ω/sq) 950 900 850 800 750 60
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As concentration (at/cm 3 ) 1E22 1E
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R s (Ω/sq) 950 900 850 800 750 70
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Following annealing it was observed
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∆a/a (x 10 -3 ) 4,0 epi550 3,5 3,
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Yield (counts per 5 uC) 350 300 250
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(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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