INTEL 1015
`
`

`
`Marc Heyns (editor)
`Marc Meuris & Paul Mertens (co—editors)
`
`Proceedings of
`the Second International Symposium on
`
`U1tra—-Clean Processing of
`Silicon Surfaces
`
`(UCPSS ’94)
`
`
`
`Acco Leuven / Amersfoort
`
`
`
`

`
`Conference organized by IMEC
`
`Firxt Edition : 1994
`
`TW. 250.000
`32 012 3262
`
`Published by Uitgeverij Aeeo, Tiensestraat 134136, 3000 Leuven (Belgie)
`Fort/1e Netherlands : Postbus 1285, 3800 BG Amersfoorl / Hamersveldseweg 10a, 3833 GP Leusden
`
`© 1994 by Acco (Academische Cooperalief c.v.), Leuven, (Belgié)
`
`No part of this book may be reproduced in any form, by mimeograph, film or any other means without
`permission in writing from the publisher.
`
`D/1994/0543/216
`
`NUGI 841
`
`ISBN 90-334-32625
`
`

`
`
`
`Table of Contents
`
`Preface
`
`Marc Heyns
`
`Trends in Wafer Cleaning Technology
`Takes/ti Haztori
`
`Keynote Presentation
`
`
`
`Recipes to Avoid Particle Contamination during Wet Cleaning Processes
`L. Mouclze, B. Beneyton, C. Paillet, JP. Joly, F. Tardij", D. Levy,
`K Bzzrla, P. Patruno, A. Tonti and W. Sievert
`
`Summary of HF—Last Wet Processing Using Direct—Displacernent
`Technology
`G.N. DiBell0, S.T. Bay, C.F. McConnell, J.W. Parker and EA. Cheney
`
`The Impact of Integrated Pre—cleans on Gate Oxide Integrity
`S. O’Brien, G. Brown and C. Tiplon
`
`Marangoni Drying : a New Concept for Drying Silicon Wafers
`R. Schild, K Locke, M Kozak and MM Heyns
`
`Particle Removal Efficiency from Native Oxides Using Dilute SC—1
`Megasonic Cleaning
`S.L. Cohen, W. Syverson, S. Basiliere, M]. Fleming, B. Furman, C. Gow,
`K Pope, R Tsai and M Liehr
`
`Metal Removal without Particle Addition : Optimization of the Dilute
`HCI Clean
`
`T.Q. Hard, P.W. Mertens, L.H. Hall and MM Heyns
`
`Diagnostics of Process—Hygiene in Large Scale Si-Manufacturing Using
`Trace-Analytical Tools
`L. Fabry, L. Késler, S. Pahlke, L. K012 and J. Hage (Invited)
`
`Ultra—Trace Metal Analysis of Si Wafer Surfaces Using Synchroton
`Radiation
`
`A. Fzlscher—Colbn'e, S. S. Laderman, S. Brennan, N. Takaura, P. Pianetta,
`A. Shimazaki, K Miyazaki, J. Kortright, D. C. Wherry
`
`Quantitative Depth Analysis of Ultratrace Elements in Silicon Wafers
`M Takenata, M. Hayashi, H. Mazsunaga, Y Honma, A. Kubota and
`Y Matsushita
`
`Characterisation of Oxides and Thin Films Using a Novel Scanning
`Kelvin Probe
`
`I.D. Baikie, G.H. Bmggink and S. Rival
`
`23
`
`27
`
`35
`
`47
`
`57
`
`65
`
`TW. 250.000
`32 012 3262
`
`a, 3833 GP Leusden
`
`any other means without
`
`ISBN 90—334~3262—5
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`
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`

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`
`
`69
`
`75
`
`79
`
`83
`
`87
`
`91
`
`95
`
`99
`
`6 R
`
`eoxidation Kinetics of I-lF—Etched Si(100), Si(110) and Si(111) Surfaces
`in Air
`J.T. Beeclzinor, P.V Kelly, G.M. O’Connor and G.M Crean
`
`A Comparative Study of Measurements of Roughness of Silicon and
`SiO2 Surfaces and Interfaces Using Scanning Probe Microscopy, Neutron
`and X—Ray Reflectivity
`A. Crossley, C.J. Sofield, J. Gofi‘, A. C.I. Lake, MT Hutc/tings, A. Menelle
`and MP. Mwrell
`
`In situ Monitoring of the Effect of Oxygen and Hydrogen Plasmas on the
`Passivation Level of Silicon Surfaces
`H. Li, EA. Ogozlo and JG. Cook
`
`Effect of Dynamical Plasma Cleaning on Si-SiO2 Structures
`V../VI. Maslovsky and GK Pavlov
`
`Adsorption and Desorption Studies of U-238 on Silicon Surfaces
`G. Mainka, S. Metz, A. Fester, H. Ochs and B. O. Kolbesen
`
`A UHV Compatible Plasma Chemical Cleaning Procedure for Low
`Temperature Epitaxial Growth on Patterned Silicon Substrates
`E. Beck, A. Dommann, I. Eisele, W. Hansch, N. Komer, D. Kniger
`and J. Ramm
`
`Soft Cleaning by in Vacuo Ultraviolet Radiation before MBE
`G. Lzppert and HJ. Osten
`
`The Effect of Various Processing and Hardware Parameters on the
`Decomposition of H202 in APM
`A. Philipossian and R. Wilkinson
`
`SCA Determination of Charges in Oxide after Metallic Contamination
`K Barla, F. Tardij", D. Walz and C. d’/lssenza
`
`103
`
`
`
` Calibration of TXRF Equipment
`107
`J. Knotlz, H. Schwenke and P. Eichinger
` Transfer Behavior of Metallic Contaminants from Solutions to Wafers
`U. Keller, W Aderhold and EP. Burte
`
`
`
`
` Low Temperature Oxides Deposited by Remote Plasma Enhanced CVD
`L. -Ac. Ragnarsson, S. Bengtsson, MO. Andersson and U. Sodervall
` H20 Microcontamination Generated by Reaction between Anhydrous
`
`HBr Gas and Transition Metal Oxides
`121
`
`A. Boireau, H. Chevrel, N. Uchida, K Miyazaki, E. Ozawa and [M Fried!
`U.V. Activated Cleaning Using NO, HCl and NO/HCl
`125
`C. Elsmore, R Gluck, P. Carr, M. Meuris, P.W. Menfens and MM Heyns
`
`
`
`
`
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`

`
`The Influence of Different Si(100) Surface Cleaning Procedures on
`Residual Contamination and Some Electrical Properties
`K Blum, G. Lzppert, R. Sarge, D. Krliger and K Héppner
`
`MOS Generation Lifetime for Measuring Metal Contamination in Silicon
`D. Walz, J.P. Joly and F. Tardzf
`'
`
`Effect of Different Chlorine Sources during Gate Oxidation
`B. Vermeire, P. W. Mertens, M.J. McGeary, K Kemls, M.M. Heyns,
`M. Schaekers and A. Lubbers
`
`Kinetics and Morphology of Copper Deposition on Hydrogen—Passivated
`Silicon Surfaces from Dilute HF Solutions
`
`J.A. Sees, L.H. Hall, 0.M.R Chyan, J.-J. Chen and H.)’. Chien
`
`A New Wet Cleaning Strategy
`M Jolley
`
`Characterization Methods of cSi/aSi Interface for Heterojunction Solar Cells
`F. Roca, D. Della Sala, G. Fameli, P. Grillo and F. Pascarella
`
`The Impact of Ca, Cu, Zn Silicon Surface Contamination on the Yield of a
`MOS DRAM Test Process
`
`W.R. Aderhold, N. Streckfufl, E.P. Bu.-1e and U. Keller
`
`UV/Ozone Pre-Treatment on Organic Contaminated Wafer for Complete
`Oxide Removal in HF Vapour Cleaning
`L. Li, J. Alay, P.W. Mertens, M. Meunls, W Vandervorst, M.M. Heyns,
`R. de Blank and E. Schuivens
`
`Improvement and Evaluation of Drying Techniques for HF-Last Wafer
`Cleaning
`L. Li, G. Zou, H. Bender, P.W. Mertens, M. Meuris, H.F. Schmidt and
`MM. Heyns
`
`Quantification Issues for VPD/TXRF
`R.S. Hockett, J.M. Metz and S. Tan
`
`Elimination of HF-Last Cleaning Related CoSi2 Defects Formation
`G. Zou, F. Jonckx, R. Donaton, W Kiiper, K Maer, P. W Menens, M. Meuris,
`M.M. Heyns, K Locke, M. Korac and R. Schild
`
`The Use of Deep Ultraviolet Photons to Remove Surface Contaminants
`A.C. Engelsberg
`
`UV-Enhanced Etching of Silicon Oxide by Chlorine Trifluoride
`C.F. Hiatt, J.W. Butterbaugh and D.C. Gray
`
`A New Method for In-Line, Real-Time Monitoring of Wafer Cleaning
`Operations
`E. Kamieniecki, P. Roman, D. Hwang and J. Ruzyllo
`
`131
`
`139
`
`143
`
`147
`
`151
`
`155
`
`159
`
`163
`
`167
`
`171
`
`177
`
`181
`
`185
`
`189
`
`

`
`
`
`
`193
`
`8 S
`
`i Surface Charge Imaging Using a High Resolution Scanning Kelvin Probe
`G.H. Braggink and I.D. Baikie
`
`
`
`Recombination Activity of Iron—Related Complexes in Silicon Studied
`with Microwave and Light-Induced Absorption Techniques
`A. Kaniava, A.L.P. Rotondaro, J. Vanhellemonz, E. Simoen, E. Gaubas,
`J. Vaitkus, T.Q. Hurd, PW Mertens, C. Claeys and D. Graf
`
`197
`
`
`
`
`
`
`
`
`
`
`Improved Rinsing Efficiency after SPM (H2804/H202) by Adding HP
`S. Verhaverbeke, R. Messoussi and T. Ohmi
`
`Fundamental Metallic Issues for Ultraclean Wafer Surfaces from Aqueous
`Solutions
`CR Helms, H.—S. Park, S. Dhanda, P. Gupta and M. Tran (Invited)
`
`Electrochemical Aspects of Noble Metals Related to Silicon Wafer
`Cleaning
`O.MR. Chyan, J.«J. Chen, HY Chien, L. Hall and J. Sees
`
`Metallic Particle Growth and Metal Induced Pitting (MIP) on Silicon
`Surfaces in Wet Processing and its Prevention
`H. Morinaga, M. Suyama, M. Nose, S. Verhaverbeke and T. Ohmi
`
`Metal Adsorption on Silicon Surfaces from Wet Wafer Cleaning Solutions
`G.J. Norga, KA. Black, H. M’Saad, J. Michel and LC. Kimerling
`
`A Novel Approach for Studying the Iron Absorption and Desorption
`Mechanisms on Silicon Surfaces during Wet Chemical Treatments
`H. Schdfer and K Budde
`
`201
`
`205
`
`217
`
`Recent Results of Ultraviolet—Initiated Processes for Cleaning and
`Etching of Silicon
`J. W Butterbaugh, DC. Gray, CF. Hiatz, H.H. Sawin and A.S. Lawing
`
`229
`
`
`
`Cleaning Performance of a Cryogenic Aerosol System
`P. Sferlazzo, A. Dart, B.K Libby, P.H. Rose, VV. Scheer and
`RG. van der Heide
`
` In-situ Rinse HF—Last for Pre-Epitaxy Cleaning
`P. Palruno, A. Fleur)», E. Andre and F. Tardif
`
`The Resurgence of Mechanical Brush Scrubbing
`WC. Kzusell and J. Pollick
`
`
`
`
`K Torek, J Ruzyllo and R. Grant
`
`
`In situ Remote Hydrogen Plasma Cleaned Si(100) for Gate Oxidation
`Formation : Correlation of Surface and Device Properties
`J.S. Montgomery, J.P. Bamak, H. Ying, J.R Hauser and R]. Nemanich
`
`255
`
`Etching of SiO2 with Anhydrous HF and Organic Solvent Vapors
`
`

`
`
`
`Physico Chemical Aspects of Hydrogen Peroxide Based Silioon Wafer
`Cleaning Solutions
`HF. Schmidt, M. Meuris, P. W. Mertens, A.L.P. Rotondaro, MM. Heyns,
`T.Q. Hard and Z. Hatcher (Invited)
`
`An HF-O3 Aqueous Solution for Silicon Wafer Cleaning
`Y Fukazawa, K Sanpei, T. Nakajima, K Takase and K Miyazaki
`
`Metal Addition of the RCA-1 Chemistry as a Function of Blend Ratio
`and Temperature
`K K Christenson, S. Smith and D. Werho
`
`TiN Etch Rate and H2O, Decomposition Studies in the H202/NH,,OH/H2O
`System
`A. Philipossian and J. Magana
`
`Reaction Limited Controlled Etch in Diluted HF Aqueous Solution
`with HNO3
`G. Seo, H. Kim, S. Kang, D. Kim, K Ryoo and P. Hong
`
`The Contrastive Behavior of COP/FP and SEP Defects in CZ Silicon
`Crystals
`T. Abe (Invited)
`
`Roughening during Wet Processing Studied by AFM of Stepped Surfaces
`S. Verhaverbeke, R. Messoussi and T. Ohmi
`
`Pitting on Wafers by Ag Trace in Diluted HP
`D. Lévy, P. Patruno, L. Mouche and F. Tardif
`
`AFM Characterization of Thermal Oxide Formed on Atomically Flat
`Si(l11) Surfaces
`M. Fukuda, C.H. Bjorkman, T. Yamazaki, S. Miyazaki and M. Hirose
`
`Interaction of the Sulphuric Acid Hydrogen Peroxide Mixture with
`Silicon Surfaces
`A.L.P. Rotondaro, H.F. Schmidt, M. Meuris, M.M. Heyns, C. Claeys
`and J. Mulready
`
`Different Reaction of O2 and Oxygen Radicals with Si under Critical
`Conditions for Growth of SiO2
`—
`K Hayama, T. Tougurt, M. Ishida and T. Nakamura
`
`Performances of Usual Wet Cleanings and Study of their Coupling with
`7 nm Gate Oxidation Parameters
`
`F. Tardifi T. Lardin, C. Paillet, D. Bremond, J.P. Joly, F. Martin, P. Mur,
`L. Mouche, P. Patruno, A. Tonti, D. Levy, K Barla and W Sievert
`
`The Impact of LOCOS Formation on the Gate Oxide Integrity
`M. Dohmen, R. VVtjbmg and R. Girisch
`
`259
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`267
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`271
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`275
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`279
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`283
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`289
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`293
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`297
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`301
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`305
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`309
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`315
`
`

`
`10
`
`Defect Density of Ultra-Thin Gate Oxides Grown by Conventional
`Oxidation Processes
`M. Depas, B. Vermeire, P.W Mertens, M. Schaekers, M Meuris and MM Heyns
`
`Adsorption Behavior of Nonionic Surfactants onto Silicon
`J.S. Jean and S. Raghavan
`
`Perfect Cleaning Technology and Analysis for Organic Contaminants on
`Si Wafer Surface
`N. Yonekawa, S. Yasui and T. Ohmi
`
`Ashing without Acid : an Assessment of Modern Photoresist Strippers
`L.M Loewenstein and G. Brown
`
`319
`
`323
`
`327
`
`331
`
`
`
`Characterization of the Removal of HMDS Monolayers
`N. Pozfiris, J. Newby, A.M Gundlach, R. Pethrick, S. Affivssman
`and A. Tannahill
`
`335
`
`
`
`
`
`
`
`
`
`Effect of Chlorine Contaminated Organic Solvent Photoresist Stripper
`on Post-Metal Etch Corrosion
`
`A. Philipossian, J. Fadden, L. Roe and E. Krosche
`
`
`
`
`Removal of Polymer Following Reactive Ion Etching
`D.K Hwang, B.P. Luther, J. Ruzyllo and D. Mount
`
`
`T. Hattori (Invited)
`
`Comparison of the Stability of the Surface Structure and H—Termination
`of H2 Annealed and HF—Last Cleaned (100) Silicon
`
` Initial Stage of Oxidation of Hydrogen—Terminated Silicon Surfaces ‘
`H. Bender, L. Li, P. Mertens, M. Caymax and MM. Heyns
`
`
`
`
`Thermal Desorption from and Chemical Stability of Hydrogen-Terminated
`Si Surfaces Studied by HREELS
`H. Nzlshimura, T. Yamazaki, S. Miyazaki and M. Hirose
`
`Electronic Properties of HF-Treated Si(111) Surfaces during Native Oxide
`Growth
`
`H. Angermann, Th. Dittrich and H. Flietner
`
`
`
`
`
`
`
`
`Degradation of Clean Si—Surfaces due to Storage in Clean (2) Wafer Boxes
`W. Storm, W. Vandervorsl, J. Alay, M. Meuris, A. Opdebeeck, M.M. Heyns,
`C. Polleunis and P. Benfrand
`
`367
`
`Chemically Treated Stepped Silicon {100} Surfaces
`V. Nayar, AJ. Pidduck, M. Idrees and BE]. Dew
`Selective Etching of Phosphorous Doped Oxides over Undoped Oxides in
`a Low Pressure HF Vapor Process
`
`R]. Wilhelm, WJ. C. Vermeulen and H. Watanabe
`
`

`
`UV-ENHANCED ETCHING OF SILICON OXIDE BY
`CHLORINE TRIFLUORIDE
`
`C. Fred Hiatt, Jeffery W. Butterbaugh and David C. Gray
`FSI International, 322 Lake Hazeltine Drive, Chaska, MN 55318
`
`185
`
`1.
`
`INTRODUCTION
`
`In semiconductor device processing, silicon oxides are used in many forms
`for many different applications. Dense thermally grown silicon oxide is used as
`the gate dielectric film in MOS transistors. Steam grown thermal silicon oxide is
`used as a field oxidation dielectric ‘layer. Doped silicon oxides such as
`phosphosilicate glass (PSG) and borophosphosilicate glass (BPSG) are used as
`intermetal dielectrics because they can be easily planarized through reflow.
`During the processing of silicon based semiconductor devices, other types of
`silicon oxide films may be formed as the result of exposure of silicon surfaces to
`chemical processing step, or to the ambient environment.
`In many cases, these
`residual oxides are considered surface contaminants since they must be removed
`to allow the formation of a high quality electrical interface. Often, it is necessary
`to remove a chemical or native oxide, along with associated residues and
`contamination from a pattern feature bottom in the presence of one or more of the
`silicon oxides mentioned above. Oxide etching selectivity is of paramount
`importance in these cases since different oxides may be etched at drastically
`different rates.
`
`A current trend in semiconductor wafer processing is towards using gas
`vapors or all dry gas processes in a cluster tool environment to remove residual
`oxides and contaminants.
`It has long been known that vapors of HF/water
`mixtures will etch various silicon oxide films, and this technology has been well
`studied [1,2] and commercialized. Etching of oxide films with anhydrous HP has
`also been well studied [3] and has been found to be affected by the quantity of
`residual water in the process environment and in the oxide film itself, such that
`the etching mechanisms appear to be similar to those for HF/water mixtures. A
`limitation encountered in the use of HF vapor phase etching of oxide films is the
`low etching rates for native and chemical silicon oxide films relative to doped
`silicon oxides
`.
`
`[1] have studied the selectivity of the HF vapor etching
`Wong et al.
`processes to many different types of oxide films. The results show that native,
`chemical, and thermal oxides are typically removed at rates up to 10 times slower
`than the removal rates of PSG and BPSG doped silicon oxides.
`This is
`problematic in several common processing circumstances.
`First of all,
`it
`is
`commonly necessary to clean native oxide and other contaminant fiom the bottom
`of contact holes through dielectric layers of BPSG. Using the current vapor phase
`processes, several hundred angstroms of the BPSG can be removed before the
`
`

`
`
`
`
`
`186
`
`silicon oxides and contamination in the contact hole are removed. Secondly, it is
`common to use sandwich structures of different types of silicon oxide films.
`For instance, a BPSG layer between two undoped oxide layers is sometimes used
`as the intermetal dielectric film in the above mentioned contact application.
`Cleaning of contact or other topographic features through this type of composite
`film with the current HP vapor technology causes enhanced lateral etching of the
`BPSG layer relative to the undoped oxide layers. This results in an undercut
`profile which is difficult to fill with subsequent films without forming voids
`Here, we describe the application of photochemical
`(UV-enhanced)
`processes for the rapid etching of doped and undoped oxide films, and the
`removal of thin chemical oxide surface layers. Previous work with CIF3 reported
`enhanced selectivity of native oxide over silicon under UV irradiation [4]. The
`processes reported here employ CIF3 gas in a dry nitrogen carrier stream and
`simultaneous UV irradiation. Doped and undoped oxides are observed to be
`removed at nearly identical rates in a large process window (pat. pending).
`
`
`
`EXPERIMENTAL
`
`
`
`The fu1l—wafer reactor used in these studies was an experimental single
`wafer vacuum cluster module capable of conducting photochemical processing of
`100, 150, or 200 mm wafers. The module was attached to a vacuum cluster
`robotic handler.
`The reactor module was constructed of hardcoated 6061
`aluminum. A dry rough pump was used to pump the vacuum reactor to a base
`pressure below 10 mtorr. High purity sapphire windows were used to allow UV
`light exposure of the wafer front side. Gases were introduced in a uniform radial
`laminar flow, to enhance the transport of etching products away from the wafer
`surface. High intensity (~200—300 mW/cm? at 200-400 nm), broad band UV
`irradiation was achieved with a commercially available 300 W/inch, medium
`pressure mercury arc discharge lamp. The wafer pre-process temperature was
`controlled using a proximity heater. During the period of UV exposure the wafer
`temperature was transient due to IR output from the UV lamps. However, the
`wafer temperature typically did not exceed 300°C during processing. Process
`pressure was monitored and controlled using a capacitance manometer in a
`feedback loop with a downstream throttle valve.
`Substrates used in this study were l50—mm p<l00> silicon wafers, 1-5
`ohm—cm. Oxide films were prepared by growing 400013. of silicon oxide in a
`steam oxidation process at 1000 °C. 5000}; BPSG (3% B, 3% P) films were
`deposited by CVD over 1000A of thermal oxide. The gases used C.P. grade
`(99.0%) CIF3 and VLSI grade (99.998%) C12. Dry N2 from a liquid N2 vapor
`delivery system was used as a diluent gas.
`Thermal oxide and BPSG removal rates were measured by comparing the
`film thickness, measured by spectroscopic reflectometry, before and after
`
`
`
`

`
`Silicon removal rates were measured by stylus profilometry on
`processing.
`wafers partially covered by a patterned oxide layer.
`
`187
`
`3.
`
`RESULTS AND DISCUSSION
`
`Rates for etching of thermal silicon oxide and BPSG in UV/CIF3 processes
`are shown in Figure 1 for an initial wafer temperatures of 150°C as a function of
`CIF3 concentration. Total flow was maintained at 1000 sccm using dry N2 as a
`diluent, and total pressure was maintained at 100 Torr. Thermal oxide and BPSG
`were found to etch at similar
`rates with a selectivity of better
`than 1.5
`
`(BPSG:thennal oxide).
`
`1.5
`
`76
`EX
`0
`
`1
`
`
`
`-BPSG
`Q)
`E E:'_"]therma| oxide
`05 g -I-BPSG/th. ox.
`-5
`:3
`3
`
`150
`
`§ 100
`g
`E
`Q)
`E 50
`=
`
`0.5
`
`0.75
`
`0.9
`
`CIF3 fraction in N2
`
`Figure 1. Removal rates of BPSG and thermal oxide during UV/CIF3 processes
`at 150°C as a function of CIF3 concentration.
`
`The removal of 10-20A chemical oxide layers using UV/CIF3 and
`UV/(ClF3+Cl2) processes was also investigated. Oxide patterned p<100> wafers,
`comprising 1-5 pm lines and vias, were subjected to an RCA-type wet chemical
`clean to produce the chemical oxide layer in the unpatterned regions. The wafers
`were then processed with UV/CIF3 or UV/(ClF3+Cl2). The CIF3 only process used
`2.5 sccm CIF3 with 997.5 sccm N2. The ClF3+C12 process used 2.5 sccm CIF3, 50
`sccm C12 and 947.5 sccm N2. Both processes were run at 100 torr with an initial
`wafer temperature of 100°C. Several wafers were exposed to UV for time periods
`ranging fiom 0.5 minutes to 3 minutes. The oxide pattern mask was subsequently
`stripped, and the depth of etching into the silicon substrate was measured using a
`
`

`
`188
`
`stylus profilometer. The results of these experiments are summarized in Figure 2.
`Regression of the time series back to a zero (undetectable silicon etch depth)
`indicates that the chemical oxide was removed after approximately 30 seconds of
`UV exposure under the experimental conditions. Comparison of the silicon
`surface roughening after chemical oxide removal for the two processes revealed
`that
`the UV/CIF3 process resulted in a visually rough surface, while the
`UV/(C1F3+Cl2) process left the silicon surface substantially smoother. This
`process is expected to be applicable as a dry contact clean.
`
`500
`
`
`
`A 400
`“S
`
`‘g 300
`g
`E 200
`ié
`
`-UVICIF3
`uuv/(c12+cn=3)
`
`"” 100
`
`
`
`
`
`
`
`
`
`
`
`O
`
`1
`
`2
`
`3
`
`4
`
`UV exposure time (minutes)
`
`Figure 2. Silicon removal as a function of UV exposure time for UV/CIF3 and
`UV/(C12 + ClF3) processes indicating the time to remove 10-20/X of
`chemical oxide.
`
`REFERENCES
`
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