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`SAMSUNG ET AL. EXHIBIT 1081
`Samsung et al. v. Elm 3DS Innovations, LLC
`IPR2016-00691
`
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`PLASMA DEPOSITION OF DIAMOND-LIKE
`
`CARBON AND FLUORINATED AMORPHOUS
`
`CARBON AND THE RESULTANT
`
`PROPERTIES AND STRUCTURE
`
`A DISSERTATION
`
`SUBMITTED TO THE DEPARTMENT
`
`OF MATERIALS SCIENCE AND ENGINEERING
`
`AND THE COMMITTEE ON GRADUATE STUDIES
`
`OF STANFORD UNIVERSITY
`
`IN PARTIAL FULFILLMENT FOR
`
`THE DEGREE OF DOCTOR OF PHILOSOPHY
`
`Alexander David Glew
`
`December 2002
`
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`UMI Number: 3085291
`
`Copyright 2003 by
`Glew, Alexander David
`
`All rights reserved.
`
`____
`
`__ (g)UMI
`
`UMI Microform 3085291
`Copyright 2003 by ProQuest Information and Learning Company.
`All rights reserved. This microform edition is protected against
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`© Copyright by Alexander David Glew 2003
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`All (rights Reserved
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`u
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`Signature Page
`
`I certify that I have read this dissertation and that in my opinion it is fully
`
`adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy
`
`Professor Mark Cappelli
`
`I certify that I have read this dissertation and that in my opinion it is fully
`
`adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy
`
`Professor William Nix
`
`Ah a
`
`I certify that I have read this dissertation and that in my opinion it is fully
`
`adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy
`
`Professor David Barnett
`
`Approved for the University Committee on Graduate Studies
`
`fQ u ^
`
`ui
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`Abstract
`
`Researchers first created diamondlike carbon (DLC) SO years ago, but it has only
`
`been the subject of intense research for the last decade. Most previous research of DLC
`
`is due to its hardness, which can approach 50 GPa. DLC is a highly stressed thin film
`
`that exists as a mixture of diamond like sp3 and graphite like sp2 bonded carbon, with 0-
`
`50% H. Many believe that high intrinsic stress states are necessary to stabilize the carbon
`
`sp3 content responsible for the hardness of DLC. Due to the inherent challenges in
`
`understanding DLC, its high intrinsic stress and limited thermal tolerance, it has received
`
`only limited application, including use as protective films for magnetic hard disks, razor
`
`blades and video recording heads.
`
`Researchers are beginning to explore other uses for amorphous carbon films,
`
`including as a low k dielectric in integrated circuits (ICs), which is the main area of
`
`interest in this study. Despite much effort, DLC failed as a low k dielectric, mainly
`
`because its dielectric constant was typically above 3. Researchers added F to impart a
`
`lower dielectric constant, creating fluorinated amorphous carbon (FLAC). However,
`
`many issues still hinder the use of FLAC as a dielectric.
`
`This author’s goals include fabricating high quality FLAC films by plasma
`
`enhanced chemical vapor deposition (PECVD), exploring the relationships between the
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`processing parameters and the dielectric value, as well as the related material properties
`
`which limit the useful application of FLAC. An improved understanding of the
`
`fundamentals behind FLAC processing may allow workers to improve upon the intrinsic
`
`stress and thermal instability that have limited its useful application.
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`iv
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`A PECVD reactor constructed for this study allowed the creation of high quality
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`DLC and FLAC films, in situ surface preparation, as well as plasma monitoring, and
`
`assured repeatable films of known composition. The PECVD reactor allowed deposition
`
`over a wide range of ion energies, pressures, and F content necessary to explore the many
`
`aspects of FLAC.
`
`A low k material must have a dielectric constant below 3. It is desirable to have a
`
`nondestructive method for measuring the dielectric value of thin films. Electrical
`
`capacitance voltage (CV) measurements made with metal insulator semiconductor (MIS)
`
`capacitors compared well with optical measurements by spectral and multi incident angle
`
`ellipsometry (MIA). The FLAC dielectric value approached 2.6, which is adequate for
`
`use in future IC processing. The optical measurements are nondestructive, but measure
`
`only electronic polarizations, and not ionic and orientational polarizations, which may
`
`also contribute to the dielectric constant.
`
`It is necessary to verify the ellipsometry
`
`measurements by CV measurements, which can measure all of the dielectric value.
`
`High thermal conductivity is important for dielectrics used in IC applications to
`
`carry away excessive thermal loads. Using a novel mask pattern that allowed two kinds
`
`of thermal conductivity measurements, thermoreflectance and 3to, as well as CV
`
`measurements on the same film, yielded FLAC conductivity values as high as 0.6 W m'1
`
`K"1. The thermal conductivity did not increase with the stress and F content, contrary to
`
`initial expectation. The author attributes this to increased contact resistance between the
`
`film and substrate, which is consistent with apparent surface roughening determined by
`
`optical measurements of films deposited with high energy and F content.
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`High intrinsic stress has limited the use of DLC, and may well limit FLAC.
`
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`Using knowledge of DLC as a starting point, studies indicate that the mechanical
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`properties of DLC and FLAC are mainly similar. DLC and FLAC film hardness ranged
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`from 14-16 GPa and 16-18 GPa respectively. Their film stress ranged from 800 MPa to
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`10 GPa. A study of thickness dependent properties showed that only films thinner than
`
`200 nm were able to achieve stresses greater than approximately 1.6 GPa, the room
`
`temperature transition pressure of graphite to diamond. This stress plateau for 200 nm
`
`and thicker films is significant, because it indicates the significant interfacial effects
`
`imparted to the thin films. Similarly, FLAC films less than 200 nm achieved stress levels
`
`up to 4 GPa. FLAC stress has the additional dependence on the F content, not observed
`
`in DLC. The stress level in FLAC films increased with the F content, which has not been
`
`observed previously.
`
`Annealing affects DLC and FLAC films. The mechanisms of annealing must be
`
`better understood in order to overcome some of the thermal limitations of FLAC which
`
`have impeded its application as an interlayer dielectric in integrated circuits. By heating
`
`the films while measuring the curvature by laser in order to determine the stress vs.
`
`temperature, the authors determined the activation energies for stress relief as 0.80 eV for
`
`DLC and 0.96 eV for FLAC. Using a standard exponential stress decay expression1 and
`
`solving the equations directly allows one to account for the annealing that takes place
`
`during heating. The coefficient of thermal expansion (CTE) mismatch between the film
`
`and substrate during cooling yields a CTE for the DLC film of approximately 10.5 ppm
`
`°C ‘. Rapid thermal annealing (RTA) of the films slightly improves the dielectric
`
`properties. The present author attributes the changes in properties observed in the present
`
`work to the reactions resulting in methane and hydrogen.
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`vi
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`The carbon sp3 content is responsible for many of the unique material properties.
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`The present work achieved high values of C sp3 content, 35-57%, for hydrogenated
`
`DLC, as determined by X-ray photoelectron spectroscopy (XPS) measurements. Films of
`
`varying thicknesses deposited under the same conditions yielded different C sp3 contents.
`
`This observation demonstrates a chemical basis for the thickness dependence that the
`
`intrinsic stress exhibited, as well as the dielectric value.
`
`It is important to understand the F content and bonding states in the FLAC films
`
`that we manufactured due to real and perceived concerns about highly fluorinated films.
`
`The F content of FLAC films, as determined by XPS, yielded the amount of carbon
`
`groups bonded as CF, CF2, and CF3. The films with less than 10% F formed only CF.
`
`FLAC films with 5-10% F were the most thermally stable, had the lowest dielectric
`
`constants, and had lower stress than more highly fluorinated films. The approach in this
`
`work of lightly fluorinating DLC to produce FLAC with less than 10% F is in contrast to
`
`most researchers attempt to create stable FLAC films with fully fluorinated carbon chains
`
`of 67% F. The understanding gained herein allows one to limit the F content in FLAC,
`
`preserving some of the best qualities of DLC, while still reducing the dielectric constant.
`
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`vii
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`Table of Contents
`
`1
`
`INTRODUCTION____________________________________________________________ 1
`
`1.1
`
`1.2
`
`Sc o pe..................................................................................................................................................... 9
`
`O rganization o f T h e s is.............................................................................................................. 14
`
`2
`
`BACKGROUND AND REVIEW .................................
`
`
`
`
`
`.................................. 16
`
`2.1
`
`2.2
`
`2.3
`
`2.4
`
`Structure o f hard carbon f ilm s............................................................................................16
`
`Properties o f am orphous hydrogenated carbon film s............................................... 21
`
`Fluorinated Am orphous Carbon...........................................................................................24
`
`PROCESSING OF AMORPHOUS CARBON FILMS........................................................................... 28
`
`2.4.1 Plasma Enhanced Chemical Vapor Deposition and subplantation o f FLAC and
`
`DLC................................................................................................................................30
`
`2.4.2 Average Ion Energy Models..........................................................................................42
`
`2.4.3 Fundamental plasma processing parameters in the synthesis o f FLAC and DLC.... 45
`
`3
`
`EXPERIMENTAL FACILITIES______________________________________________ 47
`
`3.1
`
`C hem ical V apor D eposition Rea c to r................................................................................. 47
`
`3.1.1 Chemistry and Vacuum Pressure Control......................................................................48
`
`3.2
`
`3.3
`
`Su b str a tes......................................................................................................................................51
`
`Plasm a C haracterization in the ch a m b er....................................................................... 52
`
`4
`
`FILM CHARACTERIZATION TECHNIQUES_________________________________ 54
`
`4.1
`
`4.2
`
`4.3
`
`4.4
`
`4.5
`
`X-Ray Photoelectron Spectroscopy...................................................................................54
`
`Mass deposition and density...................................................................................................57
`
`St r e s s ................................................................................................................................................57
`
`Ha r d n e s s......................................................................................................................................... 58
`
`Ellipso m etr y................................................................................................................................. 58
`
`4.5.1
`
`Spectral Ellipsometry.....................................................................................................61
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`45.2 Multi-Incident Angle Measurements............................................................................. 62
`
`4.6
`
`Capacitance Voltage Mea su r em en ts............................................................................... 63
`
`5
`
`RESULTS OF STRUCTURE, CHEMISTRY AND MECHANICAL PROPERTIES
`
`OF DLC AND FLAC FILMS_________________________________________________ 65
`
`5.1
`
`S t r u c t u r a l a n a ly s is a n d Q s p 3) c o n t e n t o f DLC film s b y X P S ..............................65
`
`5.1.1
`
`Estimate ofsp3 fraction in DLC samples by XPS.........................................................67
`
`5.2
`
`S t r u c t u r a l a n a ly s is a n d Cfsp3) c o n t e n t o f FLAC film s b y XPS a n d O p tic a l
`
`B a n d g a p ...........................................................................................................................................70
`
`5.2.1
`
`The Cfsp3) content o f FLAC...................................................................................................... 75
`
`5.2.2 H incorporation in FLAC and DLC films.............................................................................. 77
`
`5.3
`
`Densification, deposition rates and t h e formation of C(sp3)....................................79
`
`5.3.1 DLC Density and deposition rate............................................................................................79
`
`55.2
`
`FLAC Density and Deposition Rate..............................................................................83
`
`5.4
`
`Stress vs. thickness and energy in DLC and FLAC, and stress vs. F in FLAC
`
`FILMS...................................................................................................................................................85
`
`5.4.1
`
`Stress in DLC film s........................................................................................................86
`
`5.4.2
`
`Stress in FLAC film s......................................................................................................89
`
`5.5
`
`P h ase tr a n s f o r m a tio n s , s tr e s s a n d e n e rg y c o n s id e ra tio n s o f FLAC a n d DLC
`
`.............................................................................................................................................91
`
`5.6
`
`DLC AND FLAC HARDNESS.......................................................................................................... 93
`
`6
`
`RESULTS OF DLC AND FLAC THERMAL STABILITY, THERMAL EXPANSION
`
`AND THERMAL CONDUCTIVITY
`
`97
`
`6 .1
`
`Results and discussion o f the coefficient o f thermal expansion and th e
`
`STRESS RELAXATION MECHANISMS OF DLC AND FLA C........................................................98
`
`6.2
`
`6.3
`
`Rapid thermal annealing of DLC and F L A C .................................................................112
`
`Results and discussion o f the therm al conductivity of DLC and FLA C
`
`115
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`7
`
`RESULTS OF DLC AND FLAC DIELECTRIC AND OPTICAL PROPERTIES
`
`MEASUREMENTS------------------------------------------------------------------------------------- 117
`
`7.1
`
`Ellipsometric m easurem ents o f thickness com pared to profilom eters
`
`MEASUREMENTS FOR DLC AND FLAC........................................................................................................................ 118
`
`7.2
`
`ELLIPSOMETRIC MEASUREMENTS OF DIELECTRIC PROPERTIES COMPARED TO
`
`CAPACITANCE VOLTAGE MEASUREMENTS FOR DLC AND FLAC.........................................................................123
`
`8
`
`SUMMARY_______________________________________________________________ 132
`
`8.1
`
`8.2
`
`Sum m ary.......................................................................................................................................... 132
`
`Future w o r k ...................................................................................................................................135
`
`REFERENCES .........
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`List of Figures
`
`F ig u r e 2-1 2 s a n d 2 p o r b it a l s...............................................................................................................................................18
`
`Fig u r e 2-2 H y b r id iz e d s p3 b o n d in g o r b ita l s.................................................................................................................18
`
`F ig u r e 2-3 B a l l a n d s t ic k str u c tu r e o f d ia m o n d (a ) an d g r a p h it e (b)..........................................................19
`
`F ig u r e 2-4 V o l t a g e a t a t y p ic a l po w ered c a t h o d e in c a pa c it iv e l y c o u pl e d R F pla sm a...................33
`
`F ig u r e 2-5 T h e r m a l s p ik e f o r 150 eV io n in a m o r ph o u s c a r b o n a t a d ista n c e o f 2 a to m ic r a d ii
`
`(SOLID LINE), 3 ATOMIC RADII (LONG DASHED LINE), AND 4 ATOMIC RADII (HEAVY SHORT DASHED
`
`LINE).........................................................................................................................................................................................39
`
`F ig u r e 2-6 S u b p l a n t a t io n o f DLC by e n er g etic io n s.............................................................................................40
`
`F ig u re 2-7 C a r b o n P h a s e D ia g r a m .................................................................................................................................... 41
`
`F ig u re 2-8 T y p ic a l c a t h o d e v o lta g e............................................................................................................................... 42
`
`F ig u re 3-1 Sy s t e m Sc h e m a t ic O v er v iew .........................................................................................................................47
`
`F ig u r e 3-2 R F Po w e r Sc h e m a t ic ..........................................................................................................................................49
`
`Fig u r e 3-3 A v e r a g e io n e n e r g y ( • ) and bia s v o lta g e (■ ) v s. R F p o w e r in A r a t 100 mT orr
`
`pr essu re................................................................................................................................................................................53
`
`Fig u re 3-4 A v e r a g e io n e n e r g y ( • ) an d bia s v o lta g e (■ ) v s. p r e s s u r e in a r a t 100 W R F po w e r.
`
`..................................................................................................................................................................................................53
`
`F ig u r e 4 - 1 X PS sc h e m a t ic o f o per a tio n........................................................................................................................ 55
`
`F ig u r e 4-2 R e f l e c t io n fr o m a t h in film o n a su b str a te. ....................................................................................... 59
`
`F ig u r e 4-3 P a t t e r n u s e d f o r c a pa c it a n c e a n d t h e r m a l m ea s u r e m e n t s.................................................... 64
`
`F ig u re 5-1 X PS S p e c t r a o f D LC film s D epo sit e d a t 13.3 Pa f o r a r a n g e o f a v era ge ion en er g ie s.
`
`
`
`66
`
`F ig u re 5-2 C a r b o n I s s ig n a l deco n v o lu ted in t o sp2 a n d sp3 c o m p o n e n t s....................................................69
`
`F ig u re 5-3 Fl u o r in e in c o r po r a t io n in FLA C a s a fu n ctio n o f C F 4 fl o w .................................................... 71
`
`F ig u re 5-4 X PS Sp e c t r a o f C I s fea tu r e in FL A C film w ith 9% F ......................................................................72
`
`F ig u re 5-5 X PS Sp e c t r a o f F I s fea tu r e in FL A C film w ith 9% F ...................................................................... 72
`
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`Figure 5-6 XPS Survey scan o f FLAC (9% F) showing C , 0 and F peaks.................................................. 73
`
`Figure 5-7 XPS Spectra o f C I s feature in FLAC film........................................................................................74
`
`Figure 5-8 F luoro-carbo n g r o u p fraction vs. overall F content in film............................................... 75
`
`Figure 5-9 T a l c Pl o t show ing th e bandgap for a DLC film and tw o FLAC films w ith 3.8 and
`
`7.6% F CONTENT..........................................................................................................................................................77
`
`Figure 5-10 D ensity of DLC vs. ion energy deposited at 100 mTorr in pure CH»....................................80
`
`Figure 5-11 Deposition rate o f DLC deposited at 100 mTorr and 100 eV..................................................82
`
`Figure 5-12 DLC density vs. stress for films deposited at constant pressure o f 100 mTorr with
`
`INCREASING AVERAGE ION ENERGY.........................................................................................................................83
`
`Figure 5-13 B ias Voltage v s. gas ratio for FLAC films deposited at 100 mTorr and 1.27 W cm-2.
`
`.........................................................................................................................................................................................84
`
`Figure 5-14 Mass deposition rate vs. Fluorine in FLAC films at 100 W with a protective DLC
`
`LAYER ON THE SUBSTRATE.........................................................................................................................................85
`
`Figure 5-15 Stress vs. thickness for DLC films deposited at 100 mTo rr and at 100 + /-10 eV
`
`87
`
`Figure 5-16 Stress in DLC film s 200 nm or thicker..............................................................................................88
`
`Figure 5-17 Stress in FLAC film s vs. F content deposited at 100 mT orr and 100 W for films 205-
`
`360 nm thick............................................................................................................................................................... 90
`
`Figure 5-18 Stress in FLAC film s vs. F content deposited at 100 mT orr and 100 W for films 114-
`
`148 nm thick................................................................................................................................................................91
`
`Figure 5-19 DLC Hardness v s. average ion deposition energy..................................................................... 93
`
`Figure 20 FLAC hardness vs. average ion deposition energy....................................................................... 94
`
`Figure 5-21 FLAC Hardness v s. B ias Volta ge.......................................................................................................95
`
`Figure 5-22 FLAC Hardness v s. fluorine content............................................................................................. 95
`
`Figure 6-1 Stress change o f diam ond (m edium dash), DLC (short dash), graphite (solid), high-
`
`DENSITY POLYETHYLENE (LONG DASH) FILM ON Si DURING HEATING...........................................................100
`
`Figure 6-2 Stress annealing o f D L C (#) and FLAC(«) w ith 5% F upon heating to 400° C .................105
`
`Figure 6-3 D ielectric constant before( # ) and after(B) rapid thermal annealing vs. F
`
`CONCENTRATIONS OF a FLAC FILMS ON Si..............................................................................................112
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`F igure 6-4 T herm al conductivity vs. F concentrations for FLAC film s on S i.....................................116
`
`Figure 7-1 Profilom etry m easurem ent o f DLC and FLAC film thick ness.............................................. 119
`
`Figure 7-2 C om parison o f FLAC film thickness by spectral ellipsom etry, multi-incident angle
`
`ELLIPSOMETRY, AND STYLUS PROFILOMETRY AT 30 W RF POWER................................................................121
`
`F igure 7-3 Com parison o f FLAC film thickness as determined by spectral ellipsom etry, m ulti­
`
`incident ANGLE ELLIPSOMETRY, AND STYLUS PROFILOMETRY AT 7.7% F AND VARYING R F POWER.
`
`
`
`121
`
`F ig u re 7-4 D ie le c tr ic c o n s t a n t v e rs u s p o w er at c o n s ta n t F c o n t e n t o f 7.7% ....................................127
`
`F ig u re 7-5 D ie le c tric c o n s t a n t v e rs u s film F lu o rin e c o n t e n t a t a d is c h a r g e p o w er o f 30
`
`W a it s ........................................................................................................................................................................... 128
`
`F ig u re 7-6 D isp ersio n r e la tio n s h ip f o r FLAC film s (n s o lid a n d k d a s h e d )............................................ 131
`
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`List of Tables
`
`Table 1 Properties o f DLC, FLAC, diam ond and g ra ph ite.................................................................................4
`
`T a b le 5-1 T h e c o n d itio n s a n d r e s u l t s o f sp3 c o n t e n t in DLC sam ples by XPS....................................69
`
`T able 5-2 Hydrogen and Fluorine m easurem ent o f FLAC and DLC byRBS com pared w ith XPS.
`
`.........................................................................................................................................................................................78
`
`T able 5-3 Selected values of elastic properties o f low k fil m s..................................................................96
`
`T a b le 6-1 C o e ffic ie n ts o f th e r m a l ex p a n sio n a n d M o d u lu s .......................................................................... 99
`
`T able 6-2 Results fo r activation barrier to annealing for DLC and FLAC....................................105
`
`T a b le 6-3 B ond s t r e n g t h s of C— H a n d C— F sp ecies........................................................................................106
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`T able 6-4 Relaxation activation energy vs reaction and H diffusion energy................................... 111
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`T able 6-5 Polarizability of bonds............................................................................................................................113
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`T a b le 6-6 T h e rm a l conductivity o f lo w k film s .................................................................................................115
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`Table 7-1 FLAC film deposition conditions and fluorine content. ...........................................................130
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`1 Introduction
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`Diamond-like carbon (DLC) and fluorinated amorphous carbon (FLAC) interest
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`researchers in both academia and industry2 due to their useful material properties. There
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`has been some degree of research in amorphous carbon films for nearly 50 years3, ever
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`since Schmellenmier first discovered DLC in 19554. Most DLC research activity has
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`taken place in the last decade, and most FLAC research within the last five years.
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`There are many potential applications of DLC and FLAC films. Some of the
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`areas of interest include the following: protective coatings on video cassette recording
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`heads, magnetic tape, hard disks, razors, titanium and ultra high density polyethylene
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`prosthetic implants, artificial heart valves, sunglasses, coatings for infrared windows,
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`anti-reflective coatings, chemical mechanical etch stops, flat panel display emitters, and
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`many more. These are only a few of the possible uses of DLC and FLAC films.
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`Electronic applications of DLC and FLAC are particularly promising. Some have
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`proposed DLC as a coating for Si field electron emitters3. Others have proposed DLC for
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`use in a Metal-Semiconductor-Metal (MSM) layer structure as the switching elements in
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`active matrix displays6. The semiconductor community has considered FLAC as a low k
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`dielectric material to replace silicon dioxide for intermetal dielectric applications in the
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`International Technology Roadmap for Semiconductors7. Researchers at IBM Corp. have
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`also proposed DLC as a chemical mechanical polish etching stop for integrated circuit
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`(IC) processing in a European patent application8, which requires both the hardness of
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`DLC and its chemical inertness. Some have considered DLC as a hard mask and as a
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`photomask in semiconductor processing applications.
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`1
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`DLC and FLAC have also been considered for medical applications. Some of the
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`proposed uses are as coatings on titanium and ultra high-density polyethylene (UHDPE)
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`prosthetic devices9, such as artificial knees and hips. Others have considered it as a
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`coating on graphite artificial heart valves.
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`DLC and FLAC are ideal materials for some optical applications. Schebie10 et al
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`characterized the optical properties of DLC. Utilizing DLC as quarter-wave
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`antireflective coating on germanium, Sah and Koidl11 studied DLC for infrared (IR)
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`optical applications.
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`The initial interest in DLC was due to its potential use as an economical hard
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`protective coating, a “diamond-like” coating. The few successful commercial
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`applications of DLC thus far have been tribological: protective coatings on hard disks,
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`videocassette heads, magnetic tape, and razor blades. Excessive intrinsic stress and
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`thermal instability have precluded amorphous carbon films from most applications.
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`Diamond-like carbon is really a misnomer, in that DLC is an amorphous material.
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`It does not have the diamond cubic structure. However, DLC and FLAC both have a
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`high degree of C(sp3) coordination. DLC is partially sp3 coordinated, whereas di