posic/talks/seminar_2010.tex

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  33 \usepackage{semcolor}
  34 \usepackage{semlayer}           % Seminar overlays
  35 \usepackage{slidesec}           % Seminar sections and list of slides
  36
  37 \input{seminar.bug}             % Official bugs corrections
  38 \input{seminar.bg2}             % Unofficial bugs corrections
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  49 \usepackage{upgreek}
  50
  51 \begin{document}
  52
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  80
  81 % topic
  82
  83 \begin{slide}
  84 \begin{center}
  85
  86  \vspace{16pt}
  87
  88  {\LARGE\bf
  89   Atomistic simulation study of the silicon carbide precipitation
  90   in silicon
  91  }
  92
  93  \vspace{48pt}
  94
  95  \textsc{F. Zirkelbach}
  96
  97  \vspace{48pt}
  98
  99  Lehrstuhlseminar
 100
 101  \vspace{08pt}
 102
 103  17. Juni 2010
 104
 105 \end{center}
 106 \end{slide}
 107
 108 % motivation / properties / applications of silicon carbide
 109 \begin{slide}
 110
 111 \small
 112
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 114
 115
 116
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 121
 122  \rput[lt](0.2,4.6){\color{gray}PROPERTIES}
 123
 124  \rput[lt](0.5,4){wide band gap}
 125  \rput[lt](0.5,3.5){high electric breakdown field}
 126  \rput[lt](0.5,3){good electron mobility}
 127  \rput[lt](0.5,2.5){high electron saturation drift velocity}
 128  \rput[lt](0.5,2){high thermal conductivity}
 129
 130  \rput[lt](0.5,1.5){hard and mechanically stable}
 131  \rput[lt](0.5,1){chemically inert}
 132
 133  \rput[lt](0.5,0.5){radiation hardness}
 134
 135  \rput[rt](13.3,4.6){\color{gray}APPLICATIONS}
 136
 137  \rput[rt](13,3.85){high-temperature, high power}
 138  \rput[rt](13,3.5){and high-frequency}
 139  \rput[rt](13,3.15){electronic and optoelectronic devices}
 140
 141  \rput[rt](13,2.35){material suitable for extreme conditions}
 142  \rput[rt](13,2){microelectromechanical systems}
 143  \rput[rt](13,1.65){abrasives, cutting tools, heating elements}
 144
 145  \rput[rt](13,0.85){first wall reactor material, detectors}
 146  \rput[rt](13,0.5){and electronic devices for space}
 147
 148 \end{pspicture}
 149
 150 \begin{picture}(0,0)(-10,68)
 151 \includegraphics[width=2.6cm]{wide_band_gap.eps}
 152 \end{picture}
 153 \begin{picture}(0,0)(-295,-165)
 154 \includegraphics[width=3cm]{sic_led.eps}
 155 \end{picture}
 156 \begin{picture}(0,0)(-215,-165)
 157 \includegraphics[width=2.5cm]{6h-sic_3c-sic.eps}
 158 \end{picture}
 159 \begin{picture}(0,0)(-313,65)
 160 \includegraphics[width=2.2cm]{infineon_schottky.eps}
 161 \end{picture}
 162 \begin{picture}(0,0)(-220,65)
 163 \includegraphics[width=2.9cm]{sic_wechselrichter_ise.eps}
 164 \end{picture}
 165
 166 \end{slide}
 167
 168 % contents
 169
 170 \begin{slide}
 171
 172 {\large\bf
 173  Outline
 174 }
 175
 176  \begin{itemize}
 177   \item Polyteps and fabrication of silicon carbide
 178   \item Supposed precipitation mechanism of SiC in Si
 179   \item Utilized simulation techniques
 180         \begin{itemize}
 181          \item Molecular dynamics (MD) simulations
 182          \item Density functional theory (DFT) calculations
 183         \end{itemize}
 184   \item C and Si self-interstitial point defects in silicon
 185   \item Precipitation simulations
 186   \item Summary / Conclusion / Outlook
 187  \end{itemize}
 188
 189 \end{slide}
 190
 191 % start of contents
 192
 193 \begin{slide}
 194
 195  {\large\bf
 196   Polytypes of SiC
 197  }
 198
 199  \vspace{4cm}
 200
 201  \small
 202
 203 \begin{tabular}{l c c c c c c}
 204 \hline
 205  & 3C-SiC & 4H-SiC & 6H-SiC & Si & GaN & Diamond\\
 206 \hline
 207 Hardness [Mohs] & \multicolumn{3}{c}{------ 9.6 ------}& 6.5 & - & 10 \\
 208 Band gap [eV] & 2.36 & 3.23 & 3.03 & 1.12 & 3.39 & 5.5 \\
 209 Break down field [$10^6$ V/cm] & 4 & 3 & 3.2 & 0.6 & 5 & 10 \\
 210 Saturation drift velocity [$10^7$ cm/s] & 2.5 & 2.0 & 2.0 & 1 & 2.7 & 2.7 \\
 211 Electron mobility [cm$^2$/Vs] & 800 & 900 & 400 & 1100 & 900 & 2200 \\
 212 Hole mobility [cm$^2$/Vs] & 320 & 120 & 90 & 420 & 150 & 1600 \\
 213 Thermal conductivity [W/cmK] & 5.0 & 4.9 & 4.9 & 1.5 & 1.3 & 22 \\
 214 \hline
 215 \end{tabular}
 216
 217 {\tiny
 218  Values for $T=300$ K
 219 }
 220
 221 \begin{picture}(0,0)(-160,-155)
 222  \includegraphics[width=7cm]{polytypes.eps}
 223 \end{picture}
 224 \begin{picture}(0,0)(-10,-185)
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 242
 243 \end{slide}
 244
 245 \begin{slide}
 246
 247  {\large\bf
 248   Fabrication of silicon carbide
 249  }
 250
 251  \small
 252
 253  \vspace{4pt}
 254
 255  SiC - \emph{Born from the stars, perfected on earth.}
 256
 257  \vspace{4pt}
 258
 259  Conventional thin film SiC growth:
 260  \begin{itemize}
 261   \item \underline{Sublimation growth using the modified Lely method}
 262         \begin{itemize}
 263          \item SiC single-crystalline seed at $T=1800 \, ^{\circ} \text{C}$
 264          \item Surrounded by polycrystalline SiC in a graphite crucible\\
 265                at $T=2100-2400 \, ^{\circ} \text{C}$
 266          \item Deposition of supersaturated vapor on cooler seed crystal
 267         \end{itemize}
 268   \item \underline{Homoepitaxial growth using CVD}
 269         \begin{itemize}
 270          \item Step-controlled epitaxy on off-oriented 6H-SiC substrates
 271          \item C$_3$H$_8$/SiH$_4$/H$_2$ at $1100-1500 \, ^{\circ} \text{C}$
 272          \item Angle, temperature $\rightarrow$ 3C/6H/4H-SiC
 273          \item High quality but limited in size of substrates
 274         \end{itemize}
 275   \item \underline{Heteroepitaxial growth of 3C-SiC on Si using CVD/MBE}
 276         \begin{itemize}
 277          \item Two steps: carbonization and growth
 278          \item $T=650-1050 \, ^{\circ} \text{C}$
 279          \item Quality and size not yet sufficient
 280         \end{itemize}
 281  \end{itemize}
 282
 283  \begin{picture}(0,0)(-280,-65)
 284   \includegraphics[width=3.8cm]{6h-sic_3c-sic.eps}
 285  \end{picture}
 286  \begin{picture}(0,0)(-280,-55)
 287   \begin{minipage}{5cm}
 288   {\tiny
 289    NASA: 6H-SiC and 3C-SiC LED\\[-7pt]
 290    on 6H-SiC substrate
 291   }
 292   \end{minipage}
 293  \end{picture}
 294  \begin{picture}(0,0)(-265,-150)
 295   \includegraphics[width=2.4cm]{m_lely.eps}
 296  \end{picture}
 297  \begin{picture}(0,0)(-333,-175)
 298   \begin{minipage}{5cm}
 299   {\tiny
 300    1. Lid\\[-7pt]
 301    2. Heating\\[-7pt]
 302    3. Source\\[-7pt]
 303    4. Crucible\\[-7pt]
 304    5. Insulation\\[-7pt]
 305    6. Seed crystal
 306   }
 307   \end{minipage}
 308  \end{picture}
 309
 310 \end{slide}
 311
 312 \begin{slide}
 313
 314  {\large\bf
 315   Fabrication of silicon carbide
 316  }
 317
 318  \small
 319
 320  Alternative approach:
 321  Ion beam synthesis (IBS) of burried 3C-SiC layers in Si\hkl(1 0 0)
 322  \begin{itemize}
 323   \item \underline{Implantation step 1}\\
 324         180 keV C$^+$, $D=7.9\times 10^{17}$ cm$^{-2}$, $T_{\text{i}}=500\,^{\circ}\mathrm{C}$\\
 325         $\Rightarrow$ box-like distribution of equally sized
 326                        and epitactically oriented SiC precipitates
 327
 328   \item \underline{Implantation step 2}\\
 329         180 keV C$^+$, $D=0.6\times 10^{17}$ cm$^{-2}$, $T_{\text{i}}=250\,^{\circ}\mathrm{C}$\\
 330         $\Rightarrow$ destruction of SiC nanocrystals
 331                       in growing amorphous interface layers
 332   \item \underline{Annealing}\\
 333         $T=1250\,^{\circ}\mathrm{C}$, $t=10\,\text{h}$\\
 334         $\Rightarrow$ homogeneous, stoichiometric SiC layer
 335                       with sharp interfaces
 336  \end{itemize}
 337
 338  \begin{minipage}{6.3cm}
 339  \includegraphics[width=6cm]{ibs_3c-sic.eps}\\[-0.2cm]
 340  {\tiny
 341   XTEM micrograph of single crystalline 3C-SiC in Si\hkl(1 0 0)
 342  }
 343  \end{minipage}
 344  \begin{minipage}{6.3cm}
 345  \begin{center}
 346  {\color{blue}\bf\normalsize
 347   Precipitation mechanism not yet fully understood!
 348  }
 349  \renewcommand\labelitemi{$\Rightarrow$}
 350  \small
 351  \underline{Understanding the SiC precipitation}
 352  \begin{itemize}
 353   \item significant technological progress in SiC thin film formation
 354   \item perspectives for processes relying upon prevention of SiC precipitation
 355  \end{itemize}
 356  \end{center}
 357  \end{minipage}
 358
 359 \end{slide}
 360
 361 \begin{slide}
 362
 363  {\large\bf
 364   Supposed precipitation mechanism of SiC in Si
 365  }
 366
 367  \scriptsize
 368
 369  \vspace{0.1cm}
 370
 371  \begin{minipage}{3.8cm}
 372  Si \& SiC lattice structure\\[0.2cm]
 373  \includegraphics[width=3.5cm]{sic_unit_cell.eps}\\[-0.3cm]
 374  \hrule
 375  \end{minipage}
 376  \hspace{0.6cm}
 377  \begin{minipage}{3.8cm}
 378  \begin{center}
 379  \includegraphics[width=3.3cm]{tem_c-si-db.eps}
 380  \end{center}
 381  \end{minipage}
 382  \hspace{0.6cm}
 383  \begin{minipage}{3.8cm}
 384  \begin{center}
 385  \includegraphics[width=3.3cm]{tem_3c-sic.eps}
 386  \end{center}
 387  \end{minipage}
 388
 389  \begin{minipage}{4cm}
 390  \begin{center}
 391  C-Si dimers (dumbbells)\\[-0.1cm]
 392  on Si interstitial sites
 393  \end{center}
 394  \end{minipage}
 395  \hspace{0.2cm}
 396  \begin{minipage}{4.2cm}
 397  \begin{center}
 398  Agglomeration of C-Si dumbbells\\[-0.1cm]
 399  $\Rightarrow$ dark contrasts
 400  \end{center}
 401  \end{minipage}
 402  \hspace{0.2cm}
 403  \begin{minipage}{4cm}
 404  \begin{center}
 405  Precipitation of 3C-SiC in Si\\[-0.1cm]
 406  $\Rightarrow$ Moir\'e fringes\\[-0.1cm]
 407  \& release of Si self-interstitials
 408  \end{center}
 409  \end{minipage}
 410
 411  \begin{minipage}{3.8cm}
 412  \begin{center}
 413  \includegraphics[width=3.3cm]{sic_prec_seq_01.eps}
 414  \end{center}
 415  \end{minipage}
 416  \hspace{0.6cm}
 417  \begin{minipage}{3.8cm}
 418  \begin{center}
 419  \includegraphics[width=3.3cm]{sic_prec_seq_02.eps}
 420  \end{center}
 421  \end{minipage}
 422  \hspace{0.6cm}
 423  \begin{minipage}{3.8cm}
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