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

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10 Tromp, R.M. Medium Energy Ion Scattering. In: Briggs D. and Seah P. editors. Practical surface analysis. Volume 2 – Ion and Neutral Spectroscopy. 2nd ed. John Wiley Ltd. 1992. 11 J. P. Biersack, J. F. Ziegler, Nucl. Instrum. Meth. 194, 1982, 93. 12 D. J. O’Connor, J. P. Biersack, Nucl. Instrum. Meth. B 15, 1986, 14. 13 J. P. Biersack, J. F. Ziegler. “The Stopping and Range of Ions in Solids”. From Ion implantation techniques, Springer, Berlin, 1982, Eds. H. Ryssel & H. Glaswisching. 14 Ion Implantation of Semiconductors, G. Carter, W.A. Grant, Arnold, 1976. 15 Ion implantation, G. Dearnaley, J. H. Freeman, R. S. Nelson, J. Stephen, North – Holland Publishing Company, Amsterdam, 1973. 16 Fundamentals of surface and thin film analysis, L.C. Feldman, J. Mayer, North- Holland, 1986. 17 Backscattering Spectrometry, W. K. Chu, J. W. Mayer, M. Nicolet, Academic Press, New York, 1978. 18 H. A. Bethe, Ann. Physik, 5, 325 (1930) 19 F. Bloch, Ann. Physik, 16, 285 (1933) 20 O. B. Firsov, Sov. Phys. JETP 9, (1959), 1076. 21 J. Lindhard and M. Scharff, Kgl. Danske Vid. Selsk., Matt. – Fys. Medd. 27, No 15. (1953) 22 J. Lindhard and M. Scharff, Phys. Rev. 124, 128 (1961) 23 J. Lindhard, M. Scharff, H. E. Schiøtt. Matt. Fys. Medd. Kgl. Danske Vid. Selsk., 33, (1963) No 14. 24 E. Fermi and E Teller, Phys. Rev., 72, 399 (1947) 25 Eisen, F. H. G.J. Clark, J. Bøttiger, J.M.Poate, Radiat. Eff. 13, 1972, pp 93 26 Lindhard 1954, Kgl. Danske Vid. Selsk., Matt.-Fys. Medd. 28, No. 8. 29
Chapter 3 Damage and Annealing processes 3.1 Introduction Ion implantation into Si results in the displacement of Si atoms, i.e. damage to the Si lattice. While simple atomic displacement can be described in terms of the atomic theory summarised in Chapter 2, the role of energy deposition density in determining the nature of the damage is more complex. This chapter describes the damage effects produced during implantation and different types of model for damage build up and amorphisation. To produce the electrically active doped regions, post implantation annealing is required to restore the crystal lattice and enable the dopants to take up substitutional lattice sites. The process by which the crystal lattice structure is restored during annealing in most device production, i.e. solid phase epitaxial regrowth (SPER), is described. Defect evolution also occurs during annealing and a brief summary of these aspects is given. Defects still present after annealing can be detrimental to transistor device performance in that they can introduce unwanted leakage currents and decreasing carrier mobility, i.e. the proportionality constant between the electric field and the electron drift velocity (1). Diffusion of the implanted ions to greater depths during annealing needs to be minimised for shallow junction depths (Xj). The evolution of the defects at the end of the range (EOR) of the implant can cause an anomalous enhancement of dopant diffusion called transient enhanced diffusion (TED). The effects discussed in this chapter shows that optimised annealing conditions must be a compromise between conditions that result in high levels of electrical activation with minimal defects and conditions that minimise the dopant diffusion. 3.1.1 Si crystal structure and its properties The Si crystal lattice has a diamond – type structure. This can be considered to be composed of two interpenetrating fcc lattices offset by a ¼ lattice cell along each of the [100], [010] and [001] axes (2, 3). Each Si atom is covalently bound to four others in a tetrahedral arrangement sharing two valence electrons of the sp 3 shell per bond (3) with a typical bond angle of 109.47° (4). The conventional unit cell contains 8 atoms and has a lattice constant, a, of 5.4 Å (2, 3). The distance of nearest neighbour spacing is √3/4a = 2.4 Å and the next nearest neighbour is 3.8 Å (3). The Si unit cell is shown in Figure 3.1. The atomic density of Si is 5.032 x 10 22 atoms/cm 3 at room temperature (3). The (100), (110) and (111) planes are shown in Figure 3.2 respectively. Si has three isotopes, 28 Si, 29 Si and 30 Si, with 28 Si the most abundant isotope with a natural 30
Page 1 and 2: Damage formation and annealing stud
Page 3 and 4: 3.2.2.6 Other models 40 3.2.3 Other
Page 5 and 6: Chapter 7 Interaction between Xe, F
Page 7 and 8: List of Figures Figure 1.1 a) Schem
Page 9 and 10: Figure 4.13 Variation in the kinema
Page 11 and 12: Figure 6.10 MEIS energy spectra for
Page 13 and 14: Figure 7.8 Combined MEIS Xe depth p
Page 15 and 16: Abbreviations and Symbols a/c amorp
Page 17 and 18: Abstract The work described in this
Page 19 and 20: Chapter 7 5 M. Werner, J.A. van den
Page 21 and 22: terminal (Vg), current cannot flow
Page 23 and 24: This is an approximate average leve
Page 25 and 26: the active channel, adjacent to the
Page 27 and 28: To continue to improve devices ther
Page 29 and 30: produces a device quality regrown l
Page 31 and 32: technique of channelling Rutherford
Page 33 and 34: 22 J.S Williams. Solid Phase Recrys
Page 35 and 36: and the probability of scattering t
Page 37 and 38: importance for many atomic collisio
Page 39 and 40: M1, V0, E0 Figure 2.2 Elastic scatt
Page 41 and 42: 2.3.1 Models for inelastic energy l
Page 43 and 44: dE/dx (ev/Ang) 10 1 Inelastic Energ
Page 45 and 46: dE/dx (eV/Ang) 125 100 75 50 25 0 2
Page 47: Figure 2.5 Results of TRIM simulati
Page 51 and 52: the Si/SiO2 interface, consuming th
Page 53 and 54: On the basis that by creating an in
Page 55 and 56: Figure 3.4 Structure of crystalline
Page 57 and 58: a Si atom will suffer little angula
Page 59 and 60: 3.2.2.5 Homogeneous model (Critical
Page 61 and 62: 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
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Kinematic factor (K) 1.0 0.8 0.6 0.
Page 103 and 104:
Figure 4.14 Illustration of the dou
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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
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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
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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
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yield (cts / 5µC) 500 400 300 200
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5.4 Conclusion MEIS analysis with a
Page 137 and 138:
Chapter 6 Annealing studies 6.1 Int
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6.2.2.2 Results and Discussion Figu
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theory predictions and X-ray fluore
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implantation conditions are those u
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a) b) c) Yield (counts per 5 µC) Y
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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
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a) b) Yield (counts per 5 µC) Yiel
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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
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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
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(FWHM). Concomitantly, As in the re
Page 179 and 180:
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
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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:
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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