Atomic Orbitals

2. Atomic Orbitals s-orbitals p-orbitals d-orbitals

3. HB HA HA - HB = H2 Chemical Bonding Overlap of half-filled orbitals - bond formation Formation of Molecular Hydrogen from Atoms Overlap of filled orbitals - no bonding

4. Periodic Chart

5. Crystal Bonding sp3 antibonding orbitals sp3 bonding orbitals Silicon Crystal Bonding

6. Semiconductor Band Structures Silicon Germanium Gallium Arsenide

7. Intrinsic Semiconductor Aggregate Band Structure Fermi-Dirac Distribution

8. n-type Semiconductor Aggregate Band Structure Donor Ionization Fermi-Dirac Distribution

9. p-type Semiconductor Aggregate Band Structure Acceptor Ionization Fermi-Dirac Distribution

10. Temperature Dependence Fermi level shift in extrinsic silicon Mobile electron concentration (ND= 1.15(1016) cm3)

11. No Field Field Present Pictorial representation of carrier trajectory Carrier Mobility Carrier drift velocity vs applied field in intrinsic silicon

12. Effect of Dopant Impurities Effect of total dopant concentration on carrier mobility Resistivity of bulk silicon as a function of net dopant concentration

13. The Seven Crystal Systems

14. Bravais Lattices

15. Diamond Cubic Lattice a = lattice parameter; length of cubic unit cell edge Silicon atoms have tetrahedral coordination in a FCC (face centered cubic) Bravais lattice

16. z z z y y y x x x Miller Indices 100 110 111

17. Diamond Cubic Model 100 110 111

18. Cleavage Planes Crystals naturally have cleavage planes along which they are easily broken. These correspond to crystal planes of low bond density. In the diamond cubic structure, cleavage occurs along 110 planes.

19. [100] Orientation

20. [110] Orientation

21. [111] Orientation

22. [100] Cleavage

23. [111] Cleavage

24. Czochralski Process

25. Czochralski Process Equipment Image courtesy Microchemicals

26. Czochralski Factory and Boules

27. CZ Growth under Rapid Stirring Distribution Coefficients CZ Dopant Profiles under Conditions of Rapid Stirring

28. Enrichment at the Melt Interface

29. Zone Refining Si Ingot Heater Ingot slowly passes through the needle’s eye heater so that the molten zone is “swept” through the ingot from one end to the other

30. Single Pass FZ Process

31. Multiple Pass FZ Process Almost arbitrarily pure silicon can be obtained by multiple pass zone refining.

32. “Dangling Bonds” Vacancy (Schottky Defect)

33. Self-Interstital

34. Dislocations Edge Dislocation Screw Dislocation

35. Burgers Vector Edge Dislocation Screw Dislocation Dislocations in Silicon [100] [111]

36. Stacking Faults Intrinsic Stacking Fault Extrinsic Stacking Fault

37. Vacancy-Interstitial Equilibrium Formation of a Frenkel defect - vacancy-interstitial pair “Chemical” Equilibrium

38. Thermodynamic Potentials E = Internal Energy H = Enthalpy (heat content) A = Helmholtz Free Energy G = Gibbs Free Energy For condensed phases: E and H are equivalent = internal energy (total system energy) A and G are equivalent = free energy (energy available for work) T = Absolute Temperature S = Entropy (disorder) Boltzmann’s relation

39. Internal Gettering Gettering removes harmful impurities from the front side of the wafer rendering them electrically innocuous. High temperature anneal - denuded zone formation Low temperature anneal - nucleation Intermediate temperature anneal - precipitate growth

40. Oxygen Solubility in Silicon

41. Oxygen Outdiffusion

42. Precipitate Free Energy a) - Free energy of formation of a spherical precipitate as a function of radius b) - Saturated solid solution of B (e.g., interstitial oxygen) in A (e.g., silicon crystal) c) - Nucleus formation

43. Substrate Characterization by XRD Bragg pattern - [hk0], [h0l], or [0kl]

44. Wafer Finishing Ingot slicing into raw wafers Schematic of chemical mechanical polishing

45. Vapor-Liquid-Solid (VLS) Growth Si nanowires grown by VLS (at IBM)

46. liquid A B solid Gold-Silicon Eutectic A – eutectic melt mixed with solid gold B – eutectic melt mixed with solid silicon

47. Non-bridging oxygen SiO4 tetrahedron Silanol Silicon Dioxide Network

48. Thermal Oxidation One dimensional model of oxide growth Deal-Grove growth kinetics

49. Oxidation Kinetics Rate constants for wet and dry oxidation on [100] and [111] surfaces

50. Linear Rate Constant Orientation dependence for [100] and [111] surfaces affects only the “pre-exponential” factor and not the activation energy