Sn-Sb-Se based binary and ternary alloys for phase change memory applications [Elektronische Ressource] / vorgelegt von Kyung-Min Chung

Sujets

• Physik

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2008
• Nombre de lectures: 18
• Langue: English
• Poids de l'ouvrage: 21 Mo

Extrait

Sn-Sb-Se based binary and ternary alloys
for phase change memory applications
Von der Fakultat fur Mathematik, Informatik und
Naturwissenschaften der Rheinisch-Westfalischen Technischen
Hochschule Aachen zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften genehmigte Dissertation
vorgelegt von
Kyung-Min Chung
M.Sc.
aus Seoul, Korea
Berichter: Universitatsprofessor Dr. Matthias Wuttig
Universitatsprofessor Dr. Gero von Plessen
Tag der mundl ichen Prufung: 28 October 2008
Diese Dissertation ist auf den Internetseiten
der Hochschulbibliothek online verfugbarContents
List of Tables V
List of Figures VI
Abstract X
Zusammenfassung XIII
1 Introduction 1
1.1 Modern computer data storage . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Memory technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Emerging non-volatile memory technologies . . . . . . . . . . . . . . . . . 6
1.3.1 MRAM (Magnetic Random Access Memory) . . . . . . . . . . . . . 6
1.3.2 FeRAM (Ferroelectric Random Access Memory) . . . . . . . . . . . 7
1.3.3 PCRAM (Phase Change Random Access Memory) . . . . . . . . . 8
1.4 Challenges in PCRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.5 Development of phase change materials . . . . . . . . . . . . . . . . . . . . 14
1.6 Goals of this study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2 Theoretical background 17
2.1 Thermal Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.1.1 The Hertz-Knudsen equation . . . . . . . . . . . . . . . . . . . . . . 19
2.1.2 The Knudsen cell and the cosine law of emission . . . . . . . . . . . 21
2.1.3 Applications of the cosine law . . . . . . . . . . . . . . . . . . . . . 25
IContents
2.1.4 Evaporation of alloys . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.2 Crystallization kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.2.1 Phase transformation . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.2.2 Nucleation kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.2.3 Growth kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.2.4 Johnson-Mehl-Avrami (JMA model) . . . . . . . . . . . . . . . . . 43
2.3 X-ray analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.3.1 X-ray Di raction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
2.3.2 Laboratory X-ray methods . . . . . . . . . . . . . . . . . . . . . . . 52
2.3.3 X-ray Re ection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3 Experimental Methods 62
3.1 Thermal Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.1.1 Combinatorial material synthesis system . . . . . . . . . . . . . . . 62
3.1.2 The sample preparation chamber . . . . . . . . . . . . . . . . . . . 64
3.1.3 Secondary Neutral Mass Spectrometry . . . . . . . . . . . . . . . . 66
3.1.4 Control units and software . . . . . . . . . . . . . . . . . . . . . . . 69
3.2 Four-point probe method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
3.2.1 Activation energy for crystallization . . . . . . . . . . . . . . . . . . 74
3.3 X-ray analysis system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.3.1 X-ray di raction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
3.3.2 X-ray re ectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
3.4 Static tester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
3.5 Atomic Force Microscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
4 Results I : Sn-Se binary system 93
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
4.2 The SnSe alloy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
4.2.1 Temperature dependent electrical properties . . . . . . . . . . . . . 96
4.2.2 Investigation of structural properties . . . . . . . . . . . . . . . . . 98
IIContents
4.2.3 Kinetics of the structural transformations . . . . . . . . . . . . . . 103
4.2.4 Density and thickness change upon crystallization . . . . . . . . . . 105
4.2.5 Static tester experiments . . . . . . . . . . . . . . . . . . . . . . . . 107
4.3 The SnSe alloy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1122
4.3.1 Temperature dependent electrical properties . . . . . . . . . . . . . 112
4.3.2 Investigation of structural properties . . . . . . . . . . . . . . . . . 114
4.3.3 Kinetics of the structural transformations . . . . . . . . . . . . . . 115
4.3.4 Density and thickness change upon crystallization . . . . . . . . . . 117
4.3.5 Static tester experiments . . . . . . . . . . . . . . . . . . . . . . . . 119
4.3.6 Comparison with sputtered SnSe alloy . . . . . . . . . . . . . . . . 1222
4.4 The Sn Se alloy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1262 3
4.4.1 Temperature dependent electrical properties . . . . . . . . . . . . . 126
4.4.2 Investigation of structural properties . . . . . . . . . . . . . . . . . 129
4.4.3 Kinetics of the structural transformations . . . . . . . . . . . . . . 131
4.4.4 Density and thickness change upon crystallization . . . . . . . . . . 132
4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
5 Results II : Sn-Sb-Se ternary system 135
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
5.2 The MBE deposited and sputtered Sn Sb Se alloy . . . . . . . . . . . . . 1401 2 4
5.2.1 Temperature dependent electrical properties . . . . . . . . . . . . . 140
5.2.2 Investigation of structural properties . . . . . . . . . . . . . . . . . 142
5.2.3 Kinetics of the structural transformations . . . . . . . . . . . . . . 144
5.2.4 Density and thickness change upon crystallization . . . . . . . . . . 146
5.2.5 Static tester experiments . . . . . . . . . . . . . . . . . . . . . . . . 148
5.3 The SnSe -Sb Se pseudobinary alloys . . . . . . . . . . . . . . . . . . . . 1512 2 3
5.3.1 Temperature dependent electrical properties . . . . . . . . . . . . . 151
5.3.2 Investigation of structural properties . . . . . . . . . . . . . . . . . 153
5.3.3 Kinetics of the structural transformations . . . . . . . . . . . . . . 157
IIIContents
5.3.4 Density and thickness change upon crystallization . . . . . . . . . . 160
5.3.5 Static tester experiments . . . . . . . . . . . . . . . . . . . . . . . . 162
5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
Bibliography 170
Acknowledgements 183
Lebenslauf 185
IVList of Tables
2.1 The X-ray wavelengths for selected material. . . . . . . . . . . . . . . . . . 53
3.1 Bulk densities and Z-values for common used materials. . . . . . . . . . . . 67
4.1 The XRD peak positions of the as-deposited SnSe alloy. . . . . . . . . . . . 99
4.2 The XRD peak positions of the annealed SnSe alloy. . . . . . . . . . . . . . 100
4.3 The XRD peak positions of the SnSe alloy. . . . . . . . . . . . . . . . . . 1152
5.1 The XRD peak positions of Sn Sb Se alloy. . . . . . . . . . . . . . . . . . 1431 2 4
5.2 The XRD peak positions of Sn Sb Se alloy. . . . . . . . . . . . . . . . . . 1531 4 8
5.3 The XRD peak positions of Sn Sb Se alloy. . . . . . . . . . . . . . . . . . 1551 2 5
5.4 The XRD peak positions of Sn Sb Se alloy. . . . . . . . . . . . . . . . . . 1562 2 7
5.5 The data comparison for di eren t SnSe -Sb Se pseudobinary alloys. . . . . 1632 2 3
VList of Figures
1.1 Various types of data storage. . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Principle of MRAM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3 Principle of FeRAM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4 Principle of switching phase change materials. . . . . . . . . . . . . . . . . 9
1.5 Typical concepts of PCRAM cell design. . . . . . . . . . . . . . . . . . . . 12
2.1 The concept of physical vapor deposition. . . . . . . . . . . . . . . . . . . . 18
2.2 The Knudsen cell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3 The directional dependence of Knudsen cell. . . . . . . . . . . . . . . . . . 22
2.4 The directional dependence of condensation. . . . . . . . . . . . . . . . . . 25
2.5 Applications of the cosine law. . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.6 Comparison of thickness pro le obtained after evaporation in the static and
dynamic modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.7 The Gibbs free energy diagram for two phases, and of the same com-
pound as a function of the congurational coordinates. . . . . . . . . . . . 34
2.8 The Gibbs free energy of formation of nuclei as a function of lattice size. . 36
2.9 The viscosity in various stability regimes. . . . . . . . . . . . . . . . . . . 39
2.10 Schematic representation of the growth of phase 1 into the phase 2 matrix. 40
2.11 The temperature dependence of nucleation and growth rate for a fast nu-
cleation and growth dominated materials. . . . . . . . . . . . . . . . . . . . 42
2.12 Basic features of a typical XRD experiment. . . . . . . . . . . . . . . . . . 47
2.13 Several atomic planes and theier d-spacings. . . . . . . . . . . . . . . . . . 48
VI