Lucia Romano

UNIVERSIT DEGLI STUDI DI CATANIA DOTTORATO DI RICERCA IN FISICA XVIII CICLO

Heavily doped Si with B and Ga: electrical properties and clustering

Tesi per il conseguimento del titolo

Tutor: Prof.ssa Maria Grazia Grimaldi

Coordinatore: Prof. Francesco Riggi

This thesis is named after the best teacher I have ever met: My dad.

Cover: Experimental spectrum of Time Resolved Reflectivity measured on a sample of Si 550 nm amorphous thick on a crystalline substrate. More details can be found in Fig. 2.10 within this thesis, on page 45. * Poem of the Italian poetess Maria Luisa Spaziani (Rita Levi Montalcini, Abbi il Coraggio di Conoscere, Rizzoli, Milano, 2004), the English text is a free translation by Lucia Romano.

Heavily doped Si with B and Ga: electrical properties and clustering Lucia Romano Ph.D. Thesis University of Catania Printed in Catania, 10th December 2005

Non ha colonne dErcole il pensiero. La tua anima piccola, diabolica pigrizia, se le crea. N Ulisse n Colombo sospettavano le mille e mille isole in attesa. Te aspettano interi continenti. Dormono dentro il tuo cervello: osa! Il mondo da creare.

Maria Luisa Spaziani

No pillars of Hercules has thought. Your tiny soul, diabolic indolence, creates them. Ulysses or Columbus did not suspect the thousands and thousands of isles awaiting them. Whole continents are waiting for you. They are sleeping in your mind: risk it! The world has to be created. *

Contents

Introduction................................................................................................................................ I

CHAPTER 1 ............................................................................................................................... 1 Review of Si doping: incorporation, activation and deactivation of dopants ...................... 1

1.1 Defects in crystalline Si.............................................................................................. 1 1.1.1 Point defects.......................................................................................................... 2 1.1.2 Damage generation: displacement cascades ........................................................ 2 1.1.3 Annealing and Dopant diffusion............................................................................. 4

1.2 Impurity Clustering..................................................................................................... 7 1.2.1 Clustering evidences ............................................................................................. 8 1.2.2 Cluster structures .................................................................................................. 9 1.2.3 Impurity lattice location ........................................................................................ 10

1.3 Solid Phase Epitaxial Regrowth............................................................................... 13 1.3.1 Effect of impurities and regrowth models............................................................. 14 1.3.2 Supersaturated Solid Solutions ........................................................................... 19 1.3.3 Interface segregation........................................................................................... 21

1.4 Impurity ionization in heavily doped Si ..................................................................... 22 1.4.1 Low impurity concentration.................................................................................. 23 1.4.2 High impurity concentration ................................................................................. 23

1.5 References .............................................................................................................. 26

CHAPTER 2 ............................................................................................................................. 31 B and Ga in Si: impurity solubility and distribution............................................................. 31

2.1 Experimental............................................................................................................ 31 2.1.1 Sample preparation ............................................................................................. 31 2.1.2 Characterization .................................................................................................. 32

2.2 Impurity solubility in single doped (B or Ga) Si......................................................... 35 2.2.1 B doped Si........................................................................................................... 35 2.2.2 Ga doped Si ........................................................................................................ 39

2.3 Impurity solubility in B+Ga co-doped Si ................................................................... 41 2.4 SPE rate .................................................................................................................. 43

2.4.1 TRR measurements ............................................................................................ 44 2.4.2 SPE rate of B and Ga doped Si ........................................................................... 47 2.4.3 Ga segregation.................................................................................................... 51

2.5 Stability of the solid solution upon annealing ........................................................... 53 2.6 Concluding Remarks ............................................................................................... 56 2.7 References .............................................................................................................. 56

CHAPTER 3 ............................................................................................................................. 59 Effect of Strain on Carrier Mobility in heavily doped silicon............................................... 59

3.1 Brief review of carrier mobility in semiconductor ...................................................... 59 3.1.1 The BTE and the definition of carrier mobility ...................................................... 60 3.1.2 Strained silicon .................................................................................................... 63 3.1.3 Carrier Mobility in heavily doped Si ..................................................................... 65

3.2 Hall Mobility in Si doped with B and Ga ................................................................... 68 3.3 Strain in Si doped with B and Ga ............................................................................. 70

3.4 Strain effect on Hole Mobility ................................................................................... 73 3.5 Concluding Remarks ............................................................................................... 77 3.6 References .............................................................................................................. 77

CHAPTER 4 ............................................................................................................................. 79 Off-lattice displacement of dopants during ion irradiation ................................................. 79

4.1 Experiment .............................................................................................................. 79 4.1.1 Channeling Method ............................................................................................. 80 4.1.2 Evaluation of the ion energy loss......................................................................... 81

4.2 Off lattice displacement of B and Ga in Si................................................................ 83 4.2.1 Model of impurity- ISi interaction........................................................................... 86

4.3 Off lattice displacement of dopants in B+Ga co-doped Si ........................................ 88 4.3.1 Model of impurity- ISi interaction........................................................................... 88

4.4 Lattice location of impurities after ion irradiation ...................................................... 95 4.4.1 Ga doped Si ........................................................................................................ 96 4.4.2 B doped Si......................................................................................................... 101 4.4.3 B+Ga Co-doped Si ............................................................................................ 102

4.5 Concluding Remarks ............................................................................................. 104 4.6 References ............................................................................................................ 104

CHAPTER 5 ........................................................................................................................... 107 B implanted at RT in crystalline Si: B defect formation and dissolution.......................... 107

5.1 Electrical activation behaviour of B implanted in crystalline Si: literature review .... 107 5.2 Lattice location of B clusters and thermal evolution ............................................... 110

5.2.1 Experimental ..................................................................................................... 110 5.2.2 B lattice location at RT....................................................................................... 111 5.2.3 B clustering evolution during annealing ........................