Vol. 236 Nos. 1-2, December 15th, 1993
`
`ISSN 0040-6090
`
`
`LOPELIEETAITLL LILTAPTEHERENONMItomeaearawarempecpicsieane:
`we ee =
`(PNYSENSIROSSYhmtn romencttm,memeetearner
`oS
`ah
`oe
`r eri
`.
`ve
`await
`Be
`se
`3
`Pea:
`ee LTTATTA IIR
`#
`
`PERS
`
` International Journal
`on the Science and
`“ -- Condensed Matter vou
`Technologyof ae
`
`
`
`Proceedings of the 20th International Conference on Metallurgical Coatings ‘and Thin
`Films, San Diego, CA, USA, April 19-23, 1993
`
`Guest Editors: G. E. McGuire, A. Matthews and H. A. Jehn
`
`
`
`Editor-in-chief:
`J. E. Greene
`
`Page1 of 13
`
`TSMC Exhibit 1007
`
`

`

`Foes {sms)
`Hoene
`fenDijd] Cnfa
`
`
`f agaperemtienenSled
`
`
`PTOTSny
`otal OF CORT,
`Fokee
`>
`.
`
`7 Volume 236 (1993)
`
`Page 2 of 13
`
`Page 2 of 13
`
`

`

`gereae,
`
`4
`
`Chin...
`> SCDOT!
`ems
`
`Volume 236 (1993)
`
`Me OF CONCH~
`A?
`a
`/™
`(oe F095
`“Rxnighy98 aa
`
`
`
`Page 3 of 13
`
`Page 3 of 13
`
`

`

`Fiz Karlsruhe.
`
`Abstracting —Indexing Services
`This journalis cited by the following Abstracting and/or Indexing Services. Metal Abstracts, Chemical Abstracts,
`Physics Abstracts, Current Contents — Physical and Chemical Sciences, Current Contents — Engineering,
`Technology and Applied Sciences, Engineering Index, Cambridge Scientific Abstracts, Physikalische Berichte,
`Science Citation Index, Research Alert™, PASCAL (Centre National de la Recherche Scientifique),
`
`International Standard Serial Number 0040-6090
`ee
`© 1993-Elsevier Sequoia. All rights reserved
`0925-4005/93/$6.00
`No part of this publication may be teproduced, stored in a retrieval system or transmitted in any form or by any means,
`electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher, Elsevier
`Sequoia, S.A., P.O. Box 564, 1001 Lausanne, Switzerland.
`Submission of an article for publication implies the transfer of the copyright from the author(s) to the publisher and entails the
`author(s) irrevocable and exclusive authorization of the publisher to collect any sums or considerations for copying or
`reproduction payable by third parties.
`Upon acceptance of an article by the journal, the author(s) will be asked to transfer copyright of the article to the publisher.
`This transfer will ensure the widest possible dissemination of information.
`For Material Subject to US Copyright Law
`Special regulations for readers in the USA
`This journal has been registered with the Copyright Clearance Center, Inc., 21 Congress Street, Salem, MA 01970, U.S.A.
`Consentis given for copyingofarticles for personaiuse, or for the personal use of specific clients. This consent is given on the
`condition that the copier pays through the Center the per-copy fee stated in the code onthefirst page of each article for copying
`beyond that permitted by Sections 107 or 108 of the US Copyright Law. If no code appears in an article, the author has not
`given broad consent to copy and permission to copy must be obtained directly from the author. All articles published prior to
`1982 may be copied for a per-copy fee of US$2.50, also payable through the Center. This consent does not extend to other kins
`of copying, such as for general distribution, resale, advertising and promotion purposes or for creating new collective works.
`Special written permission must be obtained from the publisher for such copying.
` Noresponsibility is assumed by the Publisher for any injury and/or damage to persons or property as a matter of productsliability,
`
`
`negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein.
`
`
`
`
`
`Printed in The Netherlands
`
`Page 4 of 13
`
`Page 4 of 13
`
`

`

`LID FILMS
`
`THIN SO
`
`VOLUME236, NUMBERS J-2, DECEMBER15, 1993
`
`Contents
`eee
`
`Publication schedule .. 11... 0... cce cece eee e cee bbb cece cece cece,
`
`OPTICAL THIN FILMS
`
`Optically active films and ion processing of optical materials
`Properties of transparent conducting oxides deposited at room temperature . 2... cece cece cece eee e eens
`L. Davis (Fort Lauderdale, FL, USA)
`Optical switching technology for glazings ..... 00.00.00. c ecco ce cece cece eevee bebe bebe bb bebbbceeeec eee.
`C. M. Lampert (Berkeley, CA, USA)
`.
`Low temperature preparation oftransparent conducting ZnO:Althin films by chemical beam deposition.............
`H. Sato, T. Minami, S. Takata, T. Miyata and M.Ishii (Ishikawa, Japan)
`SnO, transparent conductor films produced by filtered vacuum are deposition..........0..0 ccc cceecececeeceeeees
`A. Ben-Shalom, L. Kaplan, R. L. Boxman, S. Goldsmith and M. Nathan (Tel-Aviv, Israel)
`Transparent conducting p-type NiO thin films prepared by magnetron sputtering ..........0..0.0ccc cece ceeueeues
`H. Sato, T. Minami, S. Takata and T. Yamada (Ishikawa, Japan)
`Characterization of n-CdS/p-CuGa, In, _, Se, thin film heterojunctions ...........0 0 cece eee cee cececeeeceeeeenees
`Y. Aparna, P. S. Reddy, B. Srinivasulu Naidu and P. Jayarama Reddy (Tirupati, India)
`
`Vv
`
`1
`
`6
`
`14
`
`20
`
`27
`
`32
`
`CVD, PECVD and non-vacuum deposition techniques for optical coating
`
`Low temperature preparation of SrTiO, thin filMs ...... 0... cece cece cece teen rennet e nee eee e nen e ens
`E. Dayalan and M. S. Tomar (Tulsa, OK, USA)
`Thermal stability of pyrolytic tin oxide films on aluminium ............ 0... e cece cece eee eee e nae
`A. Roos (Uppsala, Sweden), G. Chinyama (Lusaka, Zambia) and P. Hedenqvist (Uppsala, Sweden)
`Optical properties and equilibrium temperatures of titanium-nitride- and graphite-coated Langmuir probes for space
`FVby0)CerebC0)| 46
`M.Veszelei and E. Veszelei (Uppsala, Sweden)
`Deposition and characterization of multicomponentoxide films and multilayers from aqueous solution ..............
`G. J. Exarhos and N. J. Hess (Richland, WA, USA)
`:
`Silicon based, protective transparent multilayer coatings deposited at high rate on optical polymers by dual-mode MW/r-f.
`PECVD 20... o icc ccc cen nent een nen eens nena ret en ee neeSapte e neers eee e neers nee ee enes
`J. C. Rostaing, F. Cocuret (Jouy-en-Josas, France), B. Drevillon, R. Etemadi, C. Godet, J. Huc, J. Y. Parey and
`V. A. Yakovlev (Palaiseau, France)
`Inhomogeneousdielectrics grown by plasma-enhanced chemical vapor deposition ........-+-+ee seers sete teen nets
`S. Lim, J. H. Ryu, J. F. Wager (Corvallis, OR, USA) and L. M. Casas (Ft. Monmouth, NJ, USA)
`Characterization of magnetron-sputtered diamond-like thin films for optical coatings in IR.......-+++-+++++eeeeees67
`G. A. Clarke and R. R. Parsons (Vancouver, B.C., Canada)
`
`37
`
`40
`
`51
`
`58
`
`64
`
`DIAMOND AND RELATED MATERIALS
`Electronic and optical applications of diamond and related materials
`Thermalreaction of Ta thin films with polycrystalline diamond. .......-.- +06 essere rene cere rere sence Le eeaee
`J. S. Chen, E. Kolawa, M.-A. Nicolet and F. S. Pool (Pasadena, CA, USA)
`Effect of oxygen on hydrogenated amorphouscarbon films.......------ beet eeneeeeea gene tens sesesereseseceeec ss
`Y. Suefuji, Y. Nakamura, Y. Watanabe, §. Hirayama and K, Tamaki (Kanagawa, Japan)
`Fabrication of amorphous diamondfilms .......-.----et eeeeeteeene esse eeesseeseent eee er essence esse cess
`S. Falabella, D. B. Boercker and D. M. Sanders (Livermore, CA, USA)
`
`72
`
`77
`
`82
`
`Elsevier Sequoia
`
`Page 5 of 13
`
`

`

`Vili
`
`Synthesis of diamond and related materials
`Selective area deposition of diamond on4 in Si wafers ......... 000.0 e cece cece e eee ne cece eee enneneeteeyeescc..
`W. Hanni, C. Miiller, M. Binggeli, H. E. Hintermann, P. Krebs and A. Grisel (Neuchatel, Switzerland)
`Plasma diagnostics of a d.c. arcjet chemical vapor deposition diamond reactor .......6..6. 0000. eceeceeeececeee ee.
`S. W. Reeve and W. A. Weimer (China Lake, CA, USA)
`
`87
`
`9]
`
`96
`
`103
`
`106
`
`11]
`
`115
`
`120
`
`Diamond andrelated materials (Poster session)
`Properties of mixed-phase BN films deposited by rf. PACVD 0.2.0.0... 00.0 ccc cece cece ccc e ce eeveteneeceeeece.
`D. C. Cameron, M. Z. Karim and M.S. J. Hashmi (Dublin, Ireland)
`Thermal expansion of chemical vapor deposition grown diamondfilms ..............00..0cceceeeceeeeceececee..
`S. B. Qadri, C. Kim, E. F. Skelton, T. Hahn and J. E. Butler (Washington, DC, USA)
`Diamondthin films synthesized by a multinozzle oxy-acetylene chemical vapour deposition method .................
`W.Zhu, B. H. Tan and H. S. Tan (Singapore, Singapore)
`Application of nickel plating for the synthesis of chemical vapour deposition of diamond onsteels..................
`H. C. Shih, W. T. Hsu, C. T. Hwang, C. P. Sung, L. K. Lin and C. K. Lee (Hsinchu, Taiwan)
`Nucleation of diamondparticles by hot filament chemical vapour deposition ... 22.0.0... eee cece cece eee.
`K. Tamaki, Y. Watanabe, Y. Nakamura andS. Hirayama (Kanagawa, Japan)
`Microwave diamond synthesis with high oxygen hydrocarbons—(carbon dioxide, oxygen) ..........0..0-00cc cee.
`C.-F. Chen, S.-H. Chen, T.-M. Hong (Hsinchu, Taiwan), H.-W. Ko andS. E. Sheu (Lungtan, Taiwan)
`ADVANCES IN COATING AND THIN FILM CHARACTERIZATION
`Microstructural characterization and imaging techniques
`Calibration of an off-axis quartz crystal thickness monitor for a pulsed laser deposition system using a high resolution
`scanning electron microscope ... 2... 6.60.6. e eee eee eee ee tee ee ees tee te eeeentteteetbeetecnececee
`S. D. Walck, J. S. Zabinski, M. S. Donley (Wright Patterson, OH, USA) and J. E. Bultman (Dayton, OH, USA)
`XRD characterization of multilayered systems... 20.02... oe eee c ccc ese eeeceeueeeeueeeteececeebeceee cc.
`P. Scardi, L. Lutterotti (Mesiano, Italy) and A. Tomasi (Povo,Italy)
`Temperature dependence of atomic mixing at the copper~silicon interface... 0.06... eee cece cece cceecvcuccces
`A. M. Ektessabi (Kyoto, Japan)
`Low energy electron microscopy studies of Ge and Ag growth on Si(111).. 0.20... e cece cee eccucecceccee
`A. W. Denier van der Gon, R. M. Tromp and M.C. Reuter (Yorktown Heights, NY, USA)
`Surface and thin film analysis techniques
`Thermal modeling of a calorimetric technique for measuring the emittance of surfaces and coatings.............000.
`D. A. Jaworske (Cleveland, OH, USA)
`Further investigation of proton elastic scattering cross-section on carbon andsilicon ........... 0... cecceeceec eee.
`T. Xie (McMinnville, OR, USA), J. Liu (Chicago, IL, USA) and H.J. Fischbeck (Norman, OK, USA)
`Energy calibration accomplished by proton resonance scattering simulation .................. vec eee eee eeeeues
`T. Xie (McMinnville, OR, USA), J. Liu (Chicago, IL, USA) and H. J. Fischbeck (Norman, OK, USA)
`Application of X-ray photoelectron spectroscopy valence bands in studying ceramic surfaces and interfaces ..........
`D. Majumdar and D. Chatterjee (Rochester, NY, USA)
`Auger clectron spectroscopy studies ofinterfacial reactions in metal/semiconductor multilayers activated during differential
`scanning calorimetry measurements. 0.0.6.0 0 66.00. b eee e ec ee cece ec secaseteeceeeceeecece 169
`A. Zalar (Ljubljana, Slovenia), S. Hofmann, F, Pimentel (Stuttgart, Germany) and P. Panjan (Ljubljana, Slovenia)
`Newtrends in analytical tribology .............................
`J. M. Martin and M.Belin (Ecully, France)
`Optical properties and surface morphology studies of palladium contacts on mercuric iodide single crystals ..........
`M.A. George, M. Azoulay, A. Burger, Y. Biao, E. Silberman (Nashville, TN, USA) and D. Nason (Goleta, CA, USA)
`Non-destructive characterization techniques
`Decorative hard coatings: advances in optical characterization techniques
`U. Beck, G. Reiners and K. Witt (Berlin, Germany)
`Photothermal characterization of optical thin films... 0.0... 66000. ooecccececeeeeceeeececeecccc
`Z. L. Wu, P. K. Kuo, L. Wei, S. L. Gu and R. L. Thomas (Detroit, MI, USA)
`
`125
`
`130
`
`135
`
`140
`
`146
`153
`
`159
`
`164
`
`180
`
`191
`
`Page 6 of 13
`
`

`

`Elastic behaviour of TiN thin films.....00.0.0...eeeecccece cece eceu cee eseueseteu bee seeeeeceeces 209
`
`199
`204
`
`In-situ characterization techniques
`Kinetics of aluminium film oxidation measured by a modified quartz crystal microbalance .........
`M. Martin and E. Fromm (Stuttgart,Germany)
`Investigation of the adhesion mechanismsofsilicon alloy thin films on polymer substrates by IR ellipsometry........
`B. Drévillon (Palaiseau, France), J. C. Rostaing (Les Loges en Josas, France) and S. Vallon (Palaiseau, France)
`Mechanical properties and film adhesion
`
`M.Elena, M. Bonelli (Povo,Italy), C. E. Bottani, G. Ghislotti (Milano,Italy), A. Miotello (Povo, Italy), P. Mutti
`and P. M. Ossi (Milano, Italy)
`The nanoindentation response of systems with thin hard carbon COALINGS 6... eee eee e ces cece eeeceueeneees
`S. V. Hainsworth, T. Bartlett and T. F. Page (Newcastle upon Tyne, UK)
`The temperature-variant hardness response of duplex TBCs ...........0.0.c0ccceeccececcececeeeceeeceecceccee.
`P. C. Twigg and T. F. Page (Newcastle upon Tyne, UK)
`Finite element studies oftensile testing on thin film multilayers... 0... eee cece ccecceecuceuceucencs
`D. Krus, Jr, and R. W. Hoffman (Cleveland, OH, USA)
`An overview on metal/PET adhesion .... 0.0.2.0... ccc e cece cece ccceeeeceuuceeeeeceeebbeeecebbbeeec cece.
`J. F. Silvain (Talence, France) and J. J. Ehrhardt (Villers-lés-Nancy, France)
`Interface structure and adhesion of sputtered Ti layers on Si: the effect of heat treatment....................... ...
`I. Kondo, T. Yoneyama, K. Kondo, O. Takenaka (Kariya, Japan) and A. Kinbara (Tokyo, Japan)
`Cusp-like flaws along a rough surface 2.0.0.0... 0... e cece ce ee cee eeesecceeveeebeeeebeebebeecees
`J. Li, C.-H. Chiu, H. Gao (Stanford, CA, USA) and T.-W. Wu (San Jose, CA, USA)
`Measurement of Young’s moduli of TiC-coated film by the X-ray method ....... 0.00. ccc cccccccecceuccccccceuce
`H. Asada (Nagoya, Japan), Y. Kishi and Y. Hirose (Kanazawa, Japan)
`Measurementof the adhesion of TiN and Alcoatings by fracture mechanics tests ....... 00... 0c cccceccucccccceceee
`D. Miller, Y. R. Cho and E. Fromm (Stuttgart, Germany)
`
`214
`
`219
`
`225
`
`230
`
`236
`
`240
`
`247
`
`253
`
`TOPICAL CONFERENCE ON ADVANCED METALLIZATION
`
`Advanced metallization: materials and processes
`
`Advanced multilayer metallization schemes with copper as interconnection metal...........0.0.ccccceceacceeecuees
`S. P. Murarka, R. J. Gutmann (Troy, NY, USA), A. E. Kaloyeros and W. A. Lanford (Albany, NY, USA)
`Properties of titanium and aluminum thin films deposited by collimated sputtering................0..00.00ceeeueee
`D. Liu, S. K. Dew, M. J. Brett (Edmonton, Alb., Canada), T. Janacek, T. Smy (Ottawa, Ont., Canada) and
`W.Tsai (Palo Alto, CA, USA)
`Selective plasma deposition. ....... 0.00. c cc cee cece nee ee eee eee e eee eee e eee nent eee eeenees
`M.A. Ray, J. Duarte and G. E. McGuire (Research Triangle Park, NC, USA)
`
`Advanceddielectrics and planarization: materials and processes
`
`Stability and surface morphology offilms obtained by a chemical vapor deposition process ....... 0... 0c essences
`H. J. Viljoen (Lincoln, NE, USA)
`Characterization of phosphosilicate glass films obtained using plasma-enhanced chemical vapor deposition from tetra-
`ethylorthosilicate and trimethylphosphite........0.-. 066 ccc eee eee eee eee eee eee nee ene ene enn enn e nee ne eas
`C. L. Pillote, F. A. Shemansky (Mesa, AZ, USA), T. S. Cale and G. B. Raupp (Tempe, AZ, USA)
`
`Diffusion barriers
`Kinetics and conformality of TiN films from TDEAT and ammonia .........eee eee enter en eee eee cree es
`T. S. Cale, M. B. Chaara, G. B. Raupp (Tempe, AZ, USA) and I. J. Raaijmakers (San Jose, CA, USA)
`Amorphous W,)ReqoB2o
`diffusion barriers for <Si>/Al and ¢Si>/Cu metallizations cee eee eee e eee eee eee eens
`EKolawaX. Sun,J. S. Reid, J. S. Chen, M.-A. Nicolet and R. Ruiz (Pasadena, CA, USA)
`Study of sputtered molybdenum nitride as a diffusion barrier.........20 000 eee eee eee ee eee eee eee eens
`V. P. Anitha, A. Bhattacharya, N. G. Patil and S. Major (Bombay, India)
`
`257
`
`267
`
`274
`
`281
`
`287
`
`294
`
`301
`
`306
`
`Page 7 of 13
`
`

`

`311
`
`319
`
`325
`
`330
`
`334
`
`341
`
`347
`
`352
`
`x P
`
`roperties of chemical-vapor-deposited titanium nitride ...... 0.0... cece cece cece tence een eet e eet eennens
`J. B. Price, J. O. Borland and S. Selbrede (Sunnyvale, CA, USA)
`Evaluation of amorphous (Mo, Ta, W)—Si-N diffusion barriers for (Si>|Cu metallizations.................0000000.
`J. S. Reid, E. Kolawa, R. P. Ruiz and M.-A. Nicolet (Pasadena, CA, USA)
`Manufacturing aspects of low pressure chemical-vapor-deposited TiN barrier layers ............. 0.0 e cece cece es
`E. O. Travis and R. W. Fiordalice (Austin, TX, USA)
`Characterization of low pressure chemically vapor-deposited tungsten nitride films ............... 0.0 c ce eeeeueeuee
`S. D. Marcus and R. F. Foster (Phoenix, AZ, USA)
`Spatial composition variation in sputtered Ti-W films... 2.2.0.0... 00 eee cece e eee eees
`B. R. Rogers (Mesa, AZ, USA) and T. S. Cale (Tempe, AZ, USA)
`
`Topical conference on advanced metallization (Poster session)
`
`Mass and surface conductivity gain on polymer surfaces metallized using vacuum arc deposition....................
`R. L. Boxman and S. Goldsmith (Tel Aviv, Israel)
`Properties of reactively sputter-deposited Ta—N thin films....... 0.0.00. ccc ccc cece cece cee e cece et eeenvaeennas
`X. Sun, E. Kolawa, J.-S. Chen, J. S. Reid and M.-A. Nicolet (Pasadena, CA, USA)
`Three-dimensional simulation of an isolation trench refill process ........... 0.0.0 ccc cc eee eee ee eeeeceeeeeencuuas
`H. Liao and T. S. Cale (Tempe, AZ, USA)
`
`Author Index 20... 0... ccc cc ccc cece eee eee eee eee neces eee eeneteeeeeeneeueneneeeeteetannnnnbeeenees
`
`359
`
`Subject Index... 2.0.6... occ ccc cece tenet ene e eee n ee nen ete t eee cnteneeaeeueeneeuteuneurentennns
`
`361
`
`

`

`Thin Solid Films, 236 (1993) 347-351
`
`347
`
`Properties of reactively sputter-deposited Ta—N thin films
`
`Xin Sun, Elzbieta Kolawa, Jen-Sue Chen, Jason S. Reid and Marc-A. Nicolet
`California Institute of Technology, Pasadena, CA 91125 (USA)
`
`Abstract
`
`We deposited Ta-Nfilms by reactive r.f. sputtering from a Ta target with an N.—Ar gas mixture. Alloys over a
`composition range 0-60 at.% N have been synthesized. We report on their composition, structure and electrical
`resistivity before and after vacuum annealing in the temperature range 500-800 °C. We found that the film growth
`rate decreases with increasing ratio of the nitrogen flow rate to the total flow rate, while the nitrogen contentin the
`films first increases with the N, partial flow rate and then saturates at about 60 at.%. B.c.c.-Ta, Ta,N, TaN and
`TasNg appearin succession as the nitrogen contentrises, with Ta,N being the only single-phase film obtained. The
`atomic density of the films generally increases with the nitrogen content
`in the film. Transmission electron
`micrographs show that the grain size decreases from about 25 to 4 nm as the nitrogen concentration increases from
`20 to 50 at.%. The Ta,N phase can exist over a wide range of nitrogen concentration from about 25 to 45 at.%. For
`as-deposited films an amorphous phase exists along with polycrystalline Ta,N in the center portion of that range.
`This phase crystallizes after vacuum annealing at 600 °C for 65 min. A diagram ofstable and metastable phases for
`Ta_N films based on X-ray diffraction and transmission electron microscopy results is constructed. The resistivity
`is below 0.3 mQ cm forfilms with 0-50 at.% N and changeslittle upon vacuum annealing at 800 °C.
`a
`
`1. Introduction
`
`Thin films of Ta and its various compounds have
`long been of practical and scientific interest [1]. In the
`recent past tantalum nitride has attracted attention for
`applications as a thin film resistor with a low tempera-
`ture coefficient ofresistivity [2, 3], as a stable Schottky
`contact to silicon [4] and as a thin film diffusion barrier
`betweensilicon and metal overlayers of Ni [5], Al [6-9]
`and most recently Cu {10, 11]. As diffusion barriers in
`metal—semiconductor contacts,
`refractory metal ni-
`trides have long been recognized as an attractive class
`of material because of their high stability and good
`conductivity [12]. As an impurity in polycrystalline
`transition metalfilms, nitrogen has also been shown to
`restrict diffusion and increase the barrier effectiveness
`of those films, presumably by decorating the extended
`defects that act as fast diffusion paths in polycrystalline
`metallic films [13]. In substantial atomic concentrations,
`nitrogen can also promote the formation of amorphous
`metallic alloys with most early transition metals. The
`resulting films tend to combine the advantages of the
`high inertness of the respective metal nitrides with the
`absence offast diffusion paths as they exist in polycrys-
`talline films (for a review see ref. 14).
`To elucidate the influence of nitrogen on the diffusion
`barrier performance,
`it is essential to clarify how the
`deposition conditions and subsequent annealing treat-
`ment alter the structural and electrical properties of a
`film. The objective of the present study is to establish
`
`0040-6090/93/$6.00
`Page 9 of 13
`
`these facts for reactively sputter-deposited tantalum
`nitride films with a particular concern for the existence
`of amorphous Ta-N. The study generally follows the
`approachofa similar investigation of the W-—N system
`[15].
`
`2. Procedures
`
`Silicon wafers, either covered with thermally grown
`SiO, or patterned with photoresist, and segments of
`carbon tape were used as substrates on a stationary
`platform. .Ta—N films were deposited on these sub-
`strates by reactive r.f. magnetron sputtering from a
`7.5cm planar Ta cathode in an N,—Ar ambient. The
`substrate holder was placed about 7cm below the
`target and was neither cooled nor heated externally.
`The background pressure was 5x 10-7 Torr or less
`prior to the film deposition. The flow rates of N, and
`Ar and the total gas pressure were adjusted by mass
`flow controllers. The total pressure was monitored with
`a capacitive manometer in a feedback loop. We varied
`the N, partial flow rate, defined as the ratio of the
`nitrogen flow rate to the total flow rate of argon and
`nitrogen, from 0% to 25% to get 10 sets of films with
`different compositions. The total flow rate was in the
`range 55-80 cm? min~!. The highest flow rate was used
`to maintain good control of the nitrogen flow whenits
`fraction was small. The forward sputtering power and
`total gas pressure were kept at 300 W and 10 mTorr
`
`© 1993 — Elsevier Sequoia. All rights reserved
`
`

`

`348
`
`X. Sun et al. | Reactively sputter-deposited Ta—N thin films
`
`respectively for all depositions. Sputter deposition was
`performed in a static mode for Smin. The carbon
`substrates were used to determine the nitrogen concen-
`tration in the films by 2 MeV “He?* backscattering
`spectrometry. Photoresist-patterned films on Si sub-
`strates were obtained bylifting off in acetone and were
`subsequently used for measuring thefilm thickness with
`a Dektak profilometer. The atomic density of a film was
`calculated from its thickness and from the width of the
`Ta signal
`in the backscattering spectrum of the film.
`Films on oxidized Si substrates were annealed in a
`vacuum furnace at a pressure of about 5 x 1077 Torr
`and temperatures ranging from 500 to 800°C. All
`annealings lasted 65 min. All as-deposited and annealed
`films onoxidized Si were analyzed by backscattering
`spectrometry, four-point probe sheet resistance mea-
`surement, Co Ka X-ray diffraction using a stationary
`position-sensitive detector and by Cu Ka X-rays using
`a Read camera. We also madespecial depositions on
`copper grids covered with holey carbon. Plan-view mi-
`crostructures of these films were characterized by trans-
`mission electron microscopy (TEM)in a Philips EM430
`microscope operating at 300 keV.
`
`3. Results and discussion
`
`3.1. As-deposited films
`Figure | shows the growth rate of films for various
`N, partial flow rates in the chamber. The growth rate
`decreases rapidly as the amount of nitrogen increases.
`Forfilms reactively sputtered in a gas mixture with 5%
`N,, the growth rate is only 70%of that in pure Ar. At
`the same time the nitrogen concentration in the films
`increases steeply at first and then tends to saturate at
`about 60 at.%, as shown in Fig. 2. The symbols in this
`and subsequent figures indicate that the films are typi-
`
`10 mTorr / 300W
`as deposited
`
`55
`
`
`
`26 0
`
`&3&sFilmgrowthrate(nm/min) wo°
`
`5
`
`10
`
`15
`
`20
`
`25
`
`N,partial flow rate (%)
`
`1. Film growth rate of reactively sputtered Ta-—N films vs.
`Fig.
`nitrogen partial flow rate.
`
`Page 10 of 13
`
`Nconcentrationinfilm(atom%)-ooo °
`
`bee-Ta
`TaN
`amorph.
`TaN
`Tagg
`
`10 mTorr / 300 W
`as deposited
`
`g a
`
`°
`
`©°
`
`0
`
`5
`
`10
`
`15
`
`20
`
`25
`
`N, partial flow rate (%)
`
`Fig. 2. Nitrogen concentration in Ta—N films vs. N, partial flow rate
`in the chamber. The symbols indicate that the films are typically of
`multiphase composition.
`
`cally of multiphase composition, as determined by X-
`ray diffraction. Similar trends in deposition rate and
`nitrogen concentration have been reported previously
`for d.c.-sputtered Ta—N films [6], but the functional
`dependences on the N, flow rate of those results and
`ours cannotreadily be compared because the nitrogen
`flow rate was varied under different experimental con-
`straints. X-ray analyses reveal that the film deposited
`in pure Aris b.c.c.-Ta. For a nitrogen concentration
`between about 10 and 20 at.%, Ta,N is present
`in
`addition to the b.c.c.-Ta phase. The only crystalline
`phase present between about 20 and 50 at.% N is Ta,N,
`but an amorphous component also appears in the cen-
`ter portion of that range. At 50 at.% N, TaN is present,
`together with Ta;N, as the nitrogen concentration ex-
`ceeds the 50 at.% value. The structure of tantalum
`nitrides can be described as close-packed arrangements
`of Ta atoms with N atomsinserted in interstitial sites.
`The space group of Ta,N is P6;/mmce[16], with equal
`numbersofsites for Ta and N atoms, while the nitrogen
`atoms occupy half of the sites randomly [17]. However,
`deviations from this occupancy ratio can occur, which
`explains the finite range of existence of Ta,N. The
`range here exceeds that
`reported for
`thermal equi-
`librium conditions [18] and is presumably due to the
`non-equilibrium aspects of the sputter deposition tech-
`nique. The sequence of the phases observed here is
`consistent with the equilibrium phase diagram [18],
`where b.c.c.-Ta is known to have a low solubility for N,
`Ta,N exists over a range of about 10 at.% aroundits
`stoichiometric composition and TaN is a narrow phase.
`Various nitrogen-rich compounds
`(Ta;N,, Ta4Ns,
`Ta3N;) are also reported [16, 18], of which only TasN¢
`fits the observed X-ray lines well.
`The atomic density of the as-deposited films vs. the
`nitrogen concentration in the films is plotted in Fig. 3.
`The Ta film sputter deposited in pure Ar has a density
`
`Page 10 of 13
`
`

`

`X. Sun et al. | Reactively sputter-deposited Ta-N thin films
`
`349
`
`
`
`Fig. 4. Plan-view bright field transmission electron micrographs of
`five Ta-N films as deposited on copper grids covered with holey-
`carbon. The compositions and phases are indicated in Fig. 5.
`
`a crystalline Ta,N are imbedded. This finding confirms
`the X-ray results.
`In transition metal nitrides, deviations from ideal
`stoichiometry are quite common owing to their defect
`structure, which is similar to that of Ta,N [17, 19]. In
`W-_Nfilms the WN phase also exists in a finite range
`of film composition, but only at excess nitrogen concen-
`tration. A range with a mixture of W,N and an amor-
`phous phase does not exist
`there. Instead,
`there is a
`relatively broad region from about20 to 40 at.% N with
`a pure amorphousphase[15].
`
`3.2. Annealed films
`Isochronal heat treatments in vacuum (65 min at 500,
`600, 700 and 800 °C) for all sample compositions indi-
`cated by open circles in Fig. 5 were performed to
`
`(10@cm”) 0
`
`Atomicdensity
`
`10 mTorr /300W
`as deposited
`
`50
`40
`30
`20
`10
`N concentration in film (atom %)
`
`60
`
`70
`
`Fig. 3. Atomic density of reactively sputtered Ta-N films with
`various nitrogen concentrations. Note that the Y axis starts from
`about 4.5 instead of zero. For reference, bulk densities are indicated
`with arrows on the ¥ axis.
`
`that of bulk Ta
`as
`same
`the
`almost
`is
`that
`(5.52 x 102 cm~*). The atomic density of the films
`generally increases as the amountof nitrogen increases.
`This change in density of the films corresponds to the
`successive appearance of Ta,N, TaN and Ta;N,in the
`films as the nitrogen concentration increases.
`In the
`figure, the atomic densities of the films with high nitro-
`gen concentration are typically larger than those of
`their corresponding bulk compounds. Although this is
`unusual, these films contain some phases that are far
`from their exact stoichiometric composition, which
`might at least partly explain the results. The remaining
`discrepancy, if any, may be attributed to experimental
`uncertainties, which are due to the lateral non-unifor-
`mity of the film thickness and to the high background
`encountered in the backscattering signal of nitrogen.
`To classify the microstructure of the as-deposited
`films, special depositions (labelled A—E onthe bottom
`abscissa of Fig. 5) were made on copper grids covered
`with holey-carbon. Correspondingly labelled bright-
`field micrographs are shown in Fig. 4. The grainsofall
`crystalline phases are small and their size decreases with
`increasing nitrogen concentration from about 25 nm for
`sample A to about 4nm for sample E. They were
`measured from dark-field micrographs not shown here.
`The same trend has been reported by Gerstenburg and
`Calbick [2]. This reduction in grain size is also ex-
`pressed in the broadening of the corresponding X-ray
`diffraction lines. Because the sputtering time is kept
`constant for films of various compositions and growth
`rates, the thicknesses of the films differ. It is possible
`that the observed trend in the grain size reflects differ-
`ent stages of their evolution with film thickness rather
`than with nitrogen content. The micrographs of sam-
`ples C and D clearly reveal the additional presence of a
`featureless (amorphous) phase in which small grains of
`
`Page 11 of 13
`
`800}
`
`60
`
`50
`
`
`
`
`
`Annealingtemperature(°C)
`
`i
`
`°°
`beo-Ta+Ta,N
`
`N!'''1111111111,1
`
`m
`
`qecon--e--
`
`
`20
`10
`N concentrationin film (atom %)
`Fig. 5. Diagram of stable and metastable phases of Ta-N thin films
`prepared for this study. Open circles indicate all data points. Arrows
`on the bottom abscissa labelled A-E indicate compositions chosen
`for the TEM study (Fig. 4).
`
`

`

`350
`
`X. Sun et al. | Reactively sputter-deposited Ta-N thin films
`
`10 mTorr / 300W
`---- as deposited
`—— 800°C annealed
`
`'
`left scale rr right
`
`Ayagsisay
`
`establish the diagram of stable and unstable phases
`given in that figure, while open circles on the bottom
`abscissa indicate the compositions of all
`the as-de-
`posited samples discussed in Section 3.1. Dashed lines
`have been drawn to indicate approximate boundaries
`between regions with different predominant phases. Af-
`ter annealing at 600°C and above,
`the b.c.c.-Ta film
`sputtered deposited in pure argon partly transforms to
`the tetragonal B-Ta phase. For nitrogen concentrations
`between about 10 and 20 at.%, the Ta,N and b.c.c.-Ta
`phases that are observed at room temperature persist
`after all annealings. The linewidths of the X-ray spectra
`reflect only minor increases in the initial sizes of the
`grains of both phases. The as-deposited Ta,N phase
`initially formed at 25 at.%N is unstable and dissociates
`into b.c.c.-Ta and a Ta,N phase with presumably in-
`creased nitrogen content which places it nearer toits
`stoichiometric composition. In the composition range
`30-35 at.% N, the amorphous phase dominates in the
`as-deposited samples (C and D in Fig. 4), but disap-
`pears from the X-ray spectra above 500 °C, with the
`formation of grains that are the largest of the whole set
`investigated. When
`the
`composition
`approaches
`50 at.% N,
`the Ta,N phase again is metastable upon
`thermal annealing, but the decomposition now favors
`the increase in the nitrogen content in the phase by
`forming TaN. Above 50 at.%N, a very-fine-grained
`mixture of TaN and Ta,;N,persists at all temperatures,
`with an increase in the grain size by only about 60%
`after annealing at 800°C, as estimated from X-ray
`linewidths.
`As far as can be concluded from a comparison of
`the Ta signal heights of the as-deposited and 800 °C-
`annealed films in backscattering spectra, none of the
`films loses any nitrogen upon annealing. This is dissim-
`ilar to what occurs for reactively sputtered W-N films,
`where the loss of nitrogen upon thermal annealing is
`common. At 800 °C all tungsten nitride phases change
`to a-W [15].
`The dissimilarities between reactively sputter-de-
`posited Ta and W nitride films are related to the lesser
`stability resulting from the less negative heats of forma-
`tion of the nitrides of the Cr, Mo, W transition metal
`group compared with those of the Ti, Zr, Hf and V,
`Nb, Ta groups [19]. The bonding character in W-—N
`also changes to a partial covalency from the metallic
`Ta-—N bond.
`As shown in Fig. 6, the room temperature resistivity
`of both as-d