Chemistry in Microelectronics

381 Pages·2013·7.88 MB·English

Chemistry in Microelectronics
Chemistry in
Microelectronics
Edited by
Yannick Le Tiec
Series Editor
Robert Baptist
Firstpublished2013inGreatBritainandtheUnitedStatesbyISTELtdandJohnWiley&Sons,Inc.
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Table of Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Chapter1.Chemistryin the“FrontEndoftheLine”(FEOL):
Deposits,GateStacks,EpitaxyandContacts . . . . . . . . . . . . . . . . . . . 1
FrançoisMARTIN,Jean-MichelHARTMANN,VéroniqueCARRONand
YannickLETIEC
1.1.Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2.Arrangementofthegate . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.1.Generalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.2.Siliconnitridingprocesses . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.3.TheintroductionoftheHighK/metalgatestacks. . . . . . . . . . . 6
1.2.4.Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.3.Chemistryofcrystallinematerials . . . . . . . . . . . . . . . . . . . . . . 19
1.3.1.Generalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.3.2.Afewbasicideasaboutepitaxy . . . . . . . . . . . . . . . . . . . . . 20
1.3.3.Surfacepreparationpriortoepitaxy. . . . . . . . . . . . . . . . . . . 24
1.3.4.Low-temperatureSiandSiGegrowth:thecomparison
ofthreeprecursors(silane,disilaneanddichlorosilane). . . . . . . . . . . 30
1.3.5.Integrationandconclusion . . . . . . . . . . . . . . . . . . . . . . . . 36
1.4.Contactareasbetweenthegateandthe“source”and“drain” . . . . . . 38
1.4.1.Generalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
1.4.2.IntroductiontotheconventionalNiSiprocessfor
sub-90nmnodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
1.4.3.ImplicationsfortheSALICIDEprocessoftherecent
technologyevolutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
1.4.4.Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
vi ChemistryinMicroelectronics
1.5.Generalconclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
1.6.ListofAbbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
1.7.Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Chapter2.ChemistryinInterconnects. . . . . . . . . . . . . . . . . . . . . . . 81
VincentJOUSSEAUME,Paul-HenriHAUMESSER,CarolePERNEL,Jeffery
BUTTERBAUGH,SylvainMAÎTREJEANandDidierLOUIS
2.1.Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
2.2.Interconnects:generalitiesandbackground. . . . . . . . . . . . . . . . . 83
2.2.1.Whatconditionsarerequiredforaninterconnect? . . . . . . . . . . 83
2.2.2.Themaintechnologicaladvancements . . . . . . . . . . . . . . . . . 90
2.2.3.Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
2.3.Dielectricdeposits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
2.3.1.Dielectricgeneralities . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
2.3.2Interlinedielectrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
2.3.3.Barrierdielectrics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
2.3.4.Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
2.4.Depositionandpropertiesofmetallayersfor
interconnectstructures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
2.4.1.Themanufactureofinterconnectstructures . . . . . . . . . . . . . . 123
2.4.2.Thechemistryofmaterialsandfunctionalproperties. . . . . . . . . 126
2.4.3.Thechemistryofinterfaces. . . . . . . . . . . . . . . . . . . . . . . . 129
2.4.4.Thechemistryofmetaldepositionprocesses . . . . . . . . . . . . . 130
2.4.5.Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
2.5.Cleaningprocessforcopperinterconnects . . . . . . . . . . . . . . . . . 144
2.5.1.Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
2.5.2.Impactofcorrosioninmicroelectronics . . . . . . . . . . . . . . . . 146
2.5.3.Electrochemicaldiagnostictools. . . . . . . . . . . . . . . . . . . . . 151
2.5.4.Equipmentforcleaningcopperinterconnections . . . . . . . . . . . 156
2.6.Generalconclusionsandperspectives . . . . . . . . . . . . . . . . . . . . 161
2.7.ListofAbbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
2.8.Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
Chapter3.TheChemistryofWetSurfacePreparation:
Cleaning,EtchingandDrying . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
YannickLETIECandMartinKNOTTER
3.1.Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
3.2.Cleaning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
3.2.1.Ammoniumhydrogenperoxidemixture(APM). . . . . . . . . . . . 188
3.2.2.Hydrochloricacidhydrogenperoxidemixture(HPM). . . . . . . . 194
3.2.3.Sulfuricacidhydrogenperoxidemixture(SPM) . . . . . . . . . . . 198
TableofContents vii
3.3.Wetetching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
3.3.1.Hydrofluoricacid(HF) . . . . . . . . . . . . . . . . . . . . . . . . . . 202
3.3.2.BufferedoxideetchantorBOE(HF/NH F) . . . . . . . . . . . . . . 209
4
3.4.Rinsinganddrying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
3.4.1.Ultrapurewater(UPW) . . . . . . . . . . . . . . . . . . . . . . . . . . 214
3.4.2.Drying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
3.5.Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
3.6.ListofAbbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
3.7.Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
Chapter4.TheUseandManagementofChemical
FluidsinMicroelectronics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
ChristianeGOTTSCHALK,KevinMCLAUGHLIN,JulieCREN,CatherinePEYNEand
PatrickVALENTI
4.1.Ultrapurewater. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
4.1.1.ParametersofUPW . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
4.1.2.UPWsystemunitoperations . . . . . . . . . . . . . . . . . . . . . . . 237
4.1.3.Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
4.1.4.Futuretrends. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
4.2.Gasesforsemiconductors . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
4.2.1.Maingasesusedinthesemiconductorfabricationprocess . . . . . 252
4.2.2.Gasqualityrequirementsforsemiconductorfabrication. . . . . . . 257
4.2.3.Implementationofgasesusedinthemanufacturingof
semiconductors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
4.2.4.Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
4.3.Dissolvedgases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
4.3.1.DI-O3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
4.3.2.DI-CO2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
4.3.3.DO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
4.4.High-puritychemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
4.4.1.Techniquesofpurificationforhigh-puritychemicals. . . . . . . . . 285
4.4.2.Handlingsystemsforhigh-puritychemicals. . . . . . . . . . . . . . 287
4.5.Wastemanagement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
4.5.1.Emissionguidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
4.5.2.Liquidwastetreatment–maintechnologies. . . . . . . . . . . . . . 293
4.5.3.Gasabatementsystems . . . . . . . . . . . . . . . . . . . . . . . . . . 298
4.5.4.Recyclingandreusing . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
4.6.ListofAbbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
4.7.Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
viii ChemistryinMicroelectronics
Chapter5.SurfaceFunctionalizationforMicro-and
Nanosystems:ApplicationtoBiosensors. . . . . . . . . . . . . . . . . . . . . . 309
AntoineHOANG,GillesMARCHAND,GuillaumeNONGLATON,
IsabelleTEXIER-NOGUESandFrancoiseVINET
5.1.Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
5.2.Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
5.2.1.Metaloxidesandsemiconductors . . . . . . . . . . . . . . . . . . . . 311
5.2.2.Carbonnanotubesandsiliconnanowires. . . . . . . . . . . . . . . . 313
5.2.3.Metals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314
5.2.4.Polymers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
5.2.5.PaperandTissues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
5.3.Functionalizationprocess . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
5.3.1.Activationandcleaningtreatments . . . . . . . . . . . . . . . . . . . 317
5.3.2.Silanizationprocesses . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
5.3.3.Sol-gelandpolymerdepositiontechniques. . . . . . . . . . . . . . . 324
5.3.4.Localizationprocesses. . . . . . . . . . . . . . . . . . . . . . . . . . . 325
5.4.Moleculeandmacromoleculeimmobilization . . . . . . . . . . . . . . . 332
5.4.1.Adsorptionandcovalentgrafting . . . . . . . . . . . . . . . . . . . . 332
5.4.2.Chemicalfunctionsforcovalentgrafting. . . . . . . . . . . . . . . . 334
5.4.3.Applicationsandexamples . . . . . . . . . . . . . . . . . . . . . . . . 337
5.4.4.Thechemicaltoolbox . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
5.4.5.Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
5.5.Analytescapture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
5.5.1.Exampleofinvitroapplication. . . . . . . . . . . . . . . . . . . . . . 340
5.5.2.Exampleofinvivoapplication. . . . . . . . . . . . . . . . . . . . . . 342
5.5.3.Detectionofanalytes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
5.6.Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348
5.7.ListofAbbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
5.8.Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
ListofAuthors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
Preface
Over the last few decades, the size of transistors has been drastically
shrunk although functionality of their circuits has increased. The physics
models have been widely investigated and corrected to take into account
physicalphenomenahappeningforverysmallfeatures.Thechemistriesused
for surface preparation have long been considered as black boxes. Materials
consumption has seriously been impacting on transistor performance
pushing the engineering teams to develop new alternative chemical mixtures
andsequences.Atthesametimeoverrecentyears,themetrologymadehuge
progress, allowing a better characterization and understanding of the
phenomena.
This book isdivided into five chapters to analyze therole ofchemistry in
the fabrication of advanced transistors: the chemicals and sequences used
in processing, from cleaning to etching, the role and impact of the purity of
the sources and materials used in “front end of the line (FEOL)” which
correspond to the “heart” and performance of individual transistors, moving
further to the “back end of the line” (BEOL) which is related to the
interconnection of all the transistors designed earlier during the FEOL
processing steps. Finally, the need of specific functionalization also requires
key knowledge in surface treatments and chemical management, allowing
applications like biosensors to develop new nanosystems. A new era is
widelyopeningwiththeconvergenceofelectronicsandbiology.
Chapter 1 allows the reader to enter the fascinating world of the FEOL,
which can be considered as the place where the heart of the transistor is
manufactured. Many domains are pretty important to properly optimize the
transistor performance: from doping level and profile to capacitance and
x ChemistryinMicroelectronics
junction consideration, optimized integration of new materials in terms of
nature, properties and thicknesses. In this chapter, the focus is on three key
modules: the gate stack definition, the crystalline materials involved in
source–drain areas and the contacts definition. These key elements will give
atransistoritsfinalperformanceeitherbeingonthe“highperformance”side
or being on the “low power” side. The gate stack optimization is mandatory
and material choice is very impacting in this area: a careful choice of the
best precursors for the deposited materials is necessary. Material science is
alsomuchinvolvednotonlyinthegateareabutalsointhetwomainpartsof
the transistor that are source and drain areas. Optimized undoped (or more
recently in situ doped) monocrystalline materials have to be deposited on
theseareasandafewstepslater,specificcontactshavethentoberealized.
Chapter2bringsthereadertothenextstep,whichistheunderstandingof
the interconnection between transistors themselves, which is called the
BEOL. This chapter covers the aspects of optimizing the material properties
so that a given transistor will be able to switch as quickly as requested, even
if the signal needs to move through many metal layers of interconnection.
Today,inmostadvancedtechnologies,thereareupto13metallevels,which
allow connection between a few billions of transistors on “first – ground –
floor or level 0”. The chip can be assimilated to a building (like a tower)
with an ever smaller surface as a base and ever higher height adding new
floors, up to 13 today. Engineering teams have then to design all the
interconnectionsinsidesucha towerbuilding whichcould be seen as putting
in place the right stairs, elevators, rooms, etc., so that carriers (electrons or
holes)canmoveasfastaspossiblefromonepointtootherofthatbuilding.
Chapter3coversthe main aspectsofthesurfacepreparationthatareused
in the current industry and research laboratories. Since 1970, wet cleaning is
a key driver when advanced technologies request new answers: alternate
materials have been introduced to address the following nodes. Over the last
10 years, the specification list given to the cleaning experts is getting new
criteriaand,today,therearekeyfocusesconcerningmaterialconsumptionor
loss, as well as selectivity between materials during chemical exposure.
Basic chemistries are revisited to address new competing materials because
the “standard” semiconductor silicon surface/substrate is now challenged by
germanium, silicon-germanium, and III–V compounds, among others. The
main chemical reaction is still about oxidation and reduction or acidic and
basic, then there comes the solution of multiple equation systems. This is
nothing new to chemical science; only the theoretical approach of the basic
Preface xi
knowledge used for years has to be carefully applied to address the future
challenges in transistor technology. In successive sections, the chapter
describes the cleaning, the etching and the final rinsing-drying sequence:
mechanisms, chemical reactions, impact of concentration and temperature
arereported.
Chapter 4 describes the use and management of chemical fluids in
microelectronics. The production of semiconductor devices is extremely
sensitivetowardany presenceoftraces oforganicormetalliccontamination.
Undesired impurities must be kept at very low levels. Hence, it is important
forallproductionsteps,startingalreadywiththeresourcingofchemicals,for
example ultrapure water, gases and liquid chemicals. As device line
widths continue to shrink, the requirement for ever higher water purities
in semiconductor applications is expected to increase. Techniques to
clean these chemicals, control them to the desired concentration and,
finally, the treatment of waste water and gas abatement are covered.
The chapter also presents unique problems for liquid and gas production as
well as quality analysis with the outlook of reducing the overall
consumption.
Chapter 5 provides information regarding the surface functionalization
for micro- and nanosystems, which are natural extensions of
microelectronics and are now found in many convergent applications.
Different materials are being investigated, from metal oxides,
semiconductors, carbon nanotubes; silicon nanowires, metals or polymers.
The functionalization processes are described: activation, cleaning, plasma
treatments, chemical vapor deposition, sol-gel and polymer deposition
techniques. Localization processes are also discussed: spotting,
photolithography, scanning beam lithography, microcontact printing, etc.
Mechanisms are explained, chemical reactions and related applications are
detailed. This final chapter is a fascinating one to complete the book with,
describingsomeinteractionsbetweenchemistryandmicroelectronics.
After this technical outline, let me finally express my thanks for the
commitment and considerable work of each coauthor who spent many hours
carefully describing their expertise and picking up the most relevant
references to his domain. The reader will find many relevant references at
the end of each chapter (around 700 references in total throughout the book)
including the most recent ones. I also would like to thank the editor for