Table Of ContentSpringer Series in Materials Science 270
Cor Claeys · Eddy Simoen
Metal Impurities
in Silicon- and
Germanium-Based
Technologies
Origin, Characterization, Control, and
Device Impact
Springer Series in Materials Science
Volume 270
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Cor Claeys Eddy Simoen
(cid:129)
Metal Impurities in Silicon-
and Germanium-Based
Technologies
Origin, Characterization, Control,
and Device Impact
123
CorClaeys EddySimoen
KULeuven imec
Leuven,Belgium Leuven,Belgium
ISSN 0933-033X ISSN 2196-2812 (electronic)
SpringerSeries inMaterials Science
ISBN978-3-319-93924-7 ISBN978-3-319-93925-4 (eBook)
https://doi.org/10.1007/978-3-319-93925-4
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Prof. Jan Vanhellemont, an outstanding
material scientist who stimulated many young
students and researchers and who tried to
find joy in every facet of his professional and
family life. He would surely have been
enthusiastic to contribute to this book.
Preface
Thecontrolofimpuritiesinsemiconductormaterialshasbeenacritical issuesince
the invention of the transistor due to their severe impact on the electrical device
performance.Impuritiescanbeintroducedduringeitherthecrystalgrowingprocess
and/orthedevicefabricationofthematerialitself.Sincethe1960’smuchattention
has been given to transition metals and over the years the number of publications
has increased exponentially. Whereas originally both germanium and silicon were
studied,thebreakthroughoftheplanartechnologyshiftedthefocusmoretosilicon.
However,duringthelasttwodecadesgermaniumhasknownarenewedinterestfor
deep submicron technologies, and good performance data is reported for e.g.
FinFETs, tunnelFETs and nanowires. Therefore, this book will discuss metallic
impurities in both Si- and Ge-based technologies.
An excellent work on metal impurities in silicon-device fabrication is the book
byK.Graff,withafirsteditionin1994andanupdatedversionin1999.Thepresent
bookisbasedonthatworkandwillrefertosomeofthegiveninformation,without
repeatingallthedifferentreferences.Animportantconsiderationisthatthenumber
of metals used in device manufacturing (e.g. high-k dielectrics, via filling, metal-
lization and interconnects, silicidation/germanidation, ferroelectric memories, 3D
integration, etc.) has strongly increased in recent years. This was one of the main
motivations for writing this book. In parallel, there is a continuous push to reduce
thermal budgetsinprocessing byeitherusing lower temperatures (<500°C for 3D
integration) or shorter times (ns and ms laser annealing). This allows less options
for gettering treatments. Finally, scaling the device dimensions to the nano-era
makes them sensitive to a smaller number of defects, so that specifications and
contamination control become tighter and tighter, challenging today’s metal con-
taminationmetrology.Ultimately,thedeviceitselfbecomesthemostsensitivetool
to detect single metal atoms. All these factors have led to new demands and
insights, so that there is definitively a need for a critical assessment on the recent
literature on metal behavior in group IV semiconductors.
Themainintentionis1)toextendtheinformationbyincludingsomeadditional
and new insights reported during the last twenty years and 2) to include recent
information on the origin, characterization and electrical impact of the metal
vii
viii Preface
impurities. Especially references that appears after 2000 are critically discussed.
Over the years the sensitivity of the detection techniques has been increased and
new non-destructive techniques that can be used in-line during wafer processing
havebeendeveloped.TheInternationalRoadmapforSemiconductorTechnologies
(ITRS) has for advanced technology nodes put forward more stringent specifica-
tions for the allowable metals. Special attention is also given to the behavior of
metalsinphotovoltaicdevices.Improvedand/ornewmodelsformetalgetteringare
addressed. In addition, a chapter on ab-initio calculations and density functional
theory (DFT) has been included.
The book is designed for a wide audience, including students, PhD students,
researchers, development engineers, process engineers and application engineers
workingatuniversities,researchcentersorinindustry.Informationisgivenonthe
underlying physics involved and the state of the art in the field is addressed. The
extensive reference list after each chapter is making it an indispensable reference
book for more in depth studies of the discussed topics. It is the first time that Si,
SiGe and Ge technologies are simultaneously addressed.
Leuven, Belgium Prof. Dr. Cor Claeys
August 2018 Prof. Dr. Eddy Simoen
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Basic Properties of Transition Metals in Semiconductors . . . . . . . . . 9
2.1 Solid Solubility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2 Diffusivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.1 Ion Pairing and Doping Effects. . . . . . . . . . . . . . . . . . . . 16
2.3 Segregation and Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.4 Electrical Properties of Transition Metals. . . . . . . . . . . . . . . . . . 26
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3 Source of Metals in Si and Ge Crystal Growth and Processing . . . . 37
3.1 Crystal Growth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2 Wet Wafer Cleaning Processes . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.2.1 Contamination in Si Cleaning Technology. . . . . . . . . . . . 41
3.2.2 Contamination in Ge Cleaning Technology . . . . . . . . . . . 46
3.3 Dry Vapor Phase Wafer Cleaning . . . . . . . . . . . . . . . . . . . . . . . 47
3.4 Photoresist Deposition and Stripping . . . . . . . . . . . . . . . . . . . . . 47
3.5 Wafer Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.6 Ion Implantation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.7 Thermal Processing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.8 Metal Layers in Device Fabrication . . . . . . . . . . . . . . . . . . . . . . 58
3.8.1 Silicidation and Germanidation. . . . . . . . . . . . . . . . . . . . 59
3.8.2 Metallization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.8.3 3D Integration—Through Silicon Vias (TSV) . . . . . . . . . 63
3.8.4 Ferroelectric Memories. . . . . . . . . . . . . . . . . . . . . . . . . . 65
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
ix
x Contents
4 Characterization and Detection of Metals in Silicon
and Germanium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.1 Chemical Analysis of Metals. . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.1.1 Elemental Analysis of Surface Metal Contamination . . . . 77
4.1.2 Elemental Analysis of Bulk Metal Contamination . . . . . . 79
4.1.3 Electron Paramagnetic Resonance. . . . . . . . . . . . . . . . . . 82
4.1.4 Mössbauer Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . 85
4.2 Structural Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.2.1 Structural Analysis of Metal Precipitates . . . . . . . . . . . . . 87
4.2.2 Structural Analysis of Metal-Related Point Defects . . . . . 89
4.3 Electrical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
4.3.1 Theoretical and Practical Considerations for Lifetime
Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
4.3.2 Surface Photo Voltage Lifetime Analysis . . . . . . . . . . . . 95
4.3.3 PhotoConductance Decay (PCD) and QSS-PC
Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
4.3.4 ELYMAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
4.3.5 PL Imaging. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
4.3.6 Carrier Lifetime by IR Imaging . . . . . . . . . . . . . . . . . . . 104
4.3.7 Lifetime Mapping of Extended Defects. . . . . . . . . . . . . . 105
4.3.8 MOS Generation Lifetime Techniques . . . . . . . . . . . . . . 108
4.3.9 Deep-Level Transient Spectroscopy . . . . . . . . . . . . . . . . 110
4.4 Strategy for Metal Contamination Monitoring. . . . . . . . . . . . . . . 114
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
5 Electrical Activity of Iron and Copper in Si, SiGe and Ge. . . . . . . . 125
5.1 Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
5.1.1 Configurations of Fe . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
5.1.2 Electrical Properties of Fe . . . . . . . . . . . . . . . . . . . . . . . 136
5.1.3 Detection and Identification of Fe in Silicon . . . . . . . . . . 147
5.2 Copper. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
5.2.1 Configurations of Copper . . . . . . . . . . . . . . . . . . . . . . . . 152
5.2.2 Electrical Activity of Cu . . . . . . . . . . . . . . . . . . . . . . . . 163
5.2.3 Detection of Copper. . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
6 Electrical Properties of Metals in Si and Ge. . . . . . . . . . . . . . . . . . . 197
6.1 Nickel in Si and Ge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
6.1.1 Ni-related Point Defects and Complexes . . . . . . . . . . . . . 198
6.1.2 Precipitation and Co-precipitation of Ni . . . . . . . . . . . . . 199
6.1.3 Electrical and Optical Activity of Ni. . . . . . . . . . . . . . . . 204
6.1.4 Impact of Ni on Recombination Lifetime . . . . . . . . . . . . 212
