Hartmut S. Leipner, Reinhard Krause-Rehberg. Defects in crystals Part III: Role in technology

Transcription

1 Hartmut S. Leipner, Reinhard Krause-Rehberg Defects in crystals Part III: Role in technology

2 Course Structure of imperfect crystals I. Crystal defects Basics II. Methods of defect investigations III. Defects and technology hsl 2k Structure of imperfect crystals - Introduction defect technology 2

3 Literature K.-T. Wilke: Kristallzüchtung. Berlin: Deutscher Verlag der Wissenschaften Silicon devices. Ed. K. A. Jackson. Weinheim: Wiley-VCH H. Arnold:Physikalische Chemie der Halbleiter. Berlin: Akademieverlag P. Haasen:Physikalische Metallkunde. Berlin: Akademieverlag G. Gottstein: Physikalische Grundlagen der Materialkunde. Berlin: Springer hsl 2k Structure of imperfect crystals - Introduction defect technology 3

4 Summary After having introduced the basics of lattice defects and experimental techniques for the investigation of lattice defects, we discuss in this course technological questions which are related to crystal defects. The three complexes which are dealt with from the viewpoint of defect physics are crystal growth, semiconductor technology, and metal physics. Various techniques of crystal growth are introduced in the first complex. Mechanisms of the growth-in of defects and the correlation between thermal strain and dislocation generation are treated in addition to transport phenomena and segregation. An introduction into electrical and optical properties of semiconductor defects and problems of defect engineering are discussed. The third complex deals with topics of metal physics such as sintering, recrystallization, phase transitions, and corrosion. hsl 2k Structure of imperfect crystals - Introduction defect technology 4

5 Syllabus 1 4. Defects and crystal growth 5 6. * Defect engineering in semiconductors 7 8. Defects and semiconductor technology * Defects in metallurgy; ceramics (* given by Reinhard Krause-Rehberg) hsl 2k Structure of imperfect crystals - Introduction defect technology 5

6 Methods of crystal growth Historical digression Mass crystallization in ancient technologies: bronze, iron Development of ceramic industry; salt crystallization Term crystal originates from Greek κριος (coldness) or κριµος (ice) Development of philosophy related to crystallographic ideas: conjugation of four elements and the definition of regular solids (Aristotle, Plato) Snow flakes from the work Kristallseelen of Haeckel (1917) (Scheel 1993) hsl 2k Structure of imperfect crystals - Introduction defect technology Snow flakes 6

7 Philosopher s stone Alchemical recipe for preparation of a universal medicine (quinta essenca), discovered in 1403 and published in (Scheel 1993) minera mercurii blood-red extract spiritus vini spiritus nitri spiritus salis vinegar spiritus salis ammoniaci spiritus tartari caput mortuum oil of materia philosophorum melt furnace moderate fire melting liquid as a water hsl 2k Structure of imperfect crystals - Introduction defect technology Philosopher s stone recipe 7

8 Verneuil technology First commercial process for growing large crystals Synthesis of sapphire and ruby for jewelry and watch stones; laser rods General application to substances with a high melting point Flame fusion growth apparatus of Verneuil (Scheel 1993/Verneuil 1902) hsl 2k Structure of imperfect crystals - Introduction defect technology Verneuil 8

9 Principle of the Verneuil method Powder Gas burner Growing single crystal Seed Movement of the crystal Crystal growth from the melt according to Verneuil (Weißmantel, Hamann 1989) hsl 2k Structure of imperfect crystals - Introduction defect technology Flame fusion 9

10 Growth from the solution Application for substances which do not melt or suffer phase transitions Supersaturation by cooling or evaporation of the solvent Salts; organic crystals High-pressure synthesis of quartz and diamond Special procedure of hydrothermal synthesis of quartz (transition between growth from the solution and from the vapor phase) H 2 O above the critical point can solve high amounts of otherwise insolvable substances High-pressure synthesis of diamond from carbon solved in a Ni melt (10 10 Pa, 2500 C) b. C hsl 2k Structure of imperfect crystals - Introduction defect technology 10

11 Crystal growth from the melt (a) (b) Crystallization at a cooled finger according to Kyropoulos (a) and the selection of the seed (b) (Scheel 1993/Kyropoulos 1926) hsl 2k Structure of imperfect crystals - Introduction defect technology Kyropoulos 11

12 Bridgman method Scheme of the Bridgman technique. 1 crucible, 2 growing crystal, 3 seed, 4 furnace. (Kleber 1990) hsl 2k Structure of imperfect crystals - Introduction defect technology Bridgman 12

13 Stress cracking Stress cracking in a single crystal of InP grown in a silica crucible with B 2 O 3 encapsulant (Monberg 1994) hsl 2k Structure of imperfect crystals - Introduction defect technology Cracks InP 13

14 Horizontal Bridgman growth Modified horizontal Bridgman furnace configuration for the growth of GaAs (Monberg 1994) hsl 2k Structure of imperfect crystals - Introduction defect technology Horizontal Bridgman 14

15 Vertical gradient freeze technique Melt Seed Melt Crystal T m Vertical gradient freeze temperature profile (T m melting temperature) and configuration for the liquid encapsulated VGF growth of GaP (Monberg 1994) VGF profile hsl 2k Structure of imperfect crystals - Introduction defect technology VGF 15

16 Pulling technique according to Czochralski Crystal Pull rod Seed Envelope r.f. coil Melt Crucible/ susceptor Czochralski method of crystal growth from the melt (Hurle, Cockayne 1994) hsl 2k Structure of imperfect crystals - Introduction defect technology Czochralski 16

17 Czochralski growth Si crystal 3-phase boundary Melt Crystal Gas Melt Meniscus Silicon crystal being pulled. The arrow shows the meniscus bright ring. (Hurle, Cockayne 1994) hsl 2k Structure of imperfect crystals - Introduction defect technology Meniscus colored 17

18 Liquid encapsulation Boric oxide Graphite Crystal Quartz or PBN crucible Melt Scheme of the liquid encapsulation principle used for the growth of compound semiconductors (PBN pyrolytic boron nitride) (Hurle, Cockayne 1994) hsl 2k Structure of imperfect crystals - Introduction defect technology Encapsulation 18

19 Floating zone melting Scheme of crucible-free zone melting. 1 rod holder, 2 melting polycrystal, 3 molten zone, 4 induction coil, 5 growing single crystal. (Wilke 1988) Maximum zone length h = 28 max. σ g ρ σ surface tension g gravitational acceleration ρ density of the liquid hsl 2k Structure of imperfect crystals - Introduction defect technology FZ 19

20 Convection and phase boundaries Convection scheme and phase boundaries (a) for low and (b) for higher pull rates. 1 feed rod, 2 molten zone, 3 inductor, 4 limiting diffusion layer, 5 crystal rod with isotherms. (Wilke 1988) hsl 2k Structure of imperfect crystals - Introduction defect technology Convection in FZ growth 20