`
`PCT
`
`(30) Priority Data:
`343,163
`
`22 November 1994 (22.11.94)
`
`US
`
`(71) Applicant: SILICON RESOURCES,INC. [US/US]; P.O. Box
`50386, Phoenix, AZ 85076-0386 (US).
`
`(72) Inventors: PETERSON, William, R.; 11808 South Tuzigoot
`Court, Phoenix, AZ 85044 (US). STAUFFER, Craig, M.:
`1202 Sargent Drive, Sunnyvale, CA 94087 (US).
`
`(74) Agents: CALDERONE, Lynda, L.et al.; Panitch Schwarze
`Jacobs & Nadel, P.C., 36th floor, 1601 Market Street,
`Philadelphia, PA 19103 (US).
`
`Published
`With international search report.
`
`(54) Title!) NON-AMINIC PHOTORESIST ADHESION PROMOTERS FOR MICROELECTRONIC APPLICATIONS
`(57) Abstract
`
`A method for providing a substrate having improved adherence for pol
`lymeric films is disclosed. The method entails reacting atleast
`one organosilane compound having at least one alkylsilyl moiety therein and at least one hydrolyzable group capable of reacting with the
`substrate to silylate the substrate. Hydrolyzable by-products from the reaction,if any, have a pH less than or equal to about 7.
`
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`(51) International Patent Classification 6 :
`(11) International Publication Number:
`WO 96/15861
`BOSD BUSIothhaeB 15/04, 176,
`(43) International Publication Date:
`PCT/US95/14860|(81) Designated States: AL, AM, AT, AU, BB, BG, BR, BY, CA,
`CH,CN,CZ, DE, DK,EE, ES, FI, GB, GE, HU, IS, JP, KE,
`(22) International Filing Date:
`14 November 1995 (14.11.95)
`KG,KP, KR, KZ, LK, LR, LT, LU, LV, MD, MG, MK,
`MN, MW,MX, NO,NZ, PL, PT, RO, RU, SD,SE, SG,SI,
`SK, TJ, TM, TT, UA, UG, UZ, VN, European patent (AT,
`BE, CH, DE, DK,ES, FR, GB, GR,IE, IT, LU, MC, NL,
`PT, SE), OAPI patent (BF, BJ, CF, CG, CI, CM, GA, GN,
`ML, MR,NE, SN, TD, TG), ARIPO patent (KE, LS, Mw,
`SD, SZ, UG).
`
`30 May 1996 (30.05.96) (21) International Application Number:
`
`

`

`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international
`applications under the PCT.
`
`Viet Nam
`
`United Kingdom
`Georgia
`Guinea
`Greece
`Hungary
`Ireland
`Italy
`Japan
`Kenya
`Kyrgystan
`Democratic People’s Republic
`of Korea
`Republic of Korea
`Kazakhstan
`Liechtenstein
`Sri Lanka
`Luxembourg
`Larvia
`Monaco
`Republic of Moldova
`Madagascar
`Mali
`Mongolia
`
`AT
`AU
`BB
`
`Austria
`Australia
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Cte d'Ivoire
`Cameroon
`China
`Czechoslovakia
`Czech Republic
`Germany
`Denmark
`Spain
`Finland
`France
`Gabon
`
`Tajikistan
`Trinidad and Tobago
`Ukraine
`United States of America
`Uzbekistan
`
`

`

`WO96/15861
`
`PCT/US95/14860
`
`NON-AMINIC PHOTORESIST ADHESION
`PROMOTERS FOR MICROELECTRONIC APPLICATIONSSSeeSEERUBLECTRONIC
`APPLICATIONS
`
`Field of Invention
`The invention is directed to treating
`semiconductor substrates prior to application of
`photoresists thereon during the manufacture of
`microelectronic devices.
`
`Background of the invention
`The microelectronics industry influences all
`aspects of modern day economies. At the center of this
`industry are microelectronic devices commonly referred to as
`chips.
`Improvements in design and materials in recent years
`have increased the performance of chips from containing a
`few thousand transistors to millions of transistors in
`approximately the same chip size. Microelectronic devices
`in the near future are expected to contain billions of
`transistors in this same chip size.
`Miniaturization to promote greater functionality
`per unit area of chip has placed tremendous demands on
`design, as well as the materials and chemistries utilized in
`manufacture of the chip. An important aspect of the
`manufacture of these devices entails application of
`photoactive films i.e., photoresists to the substrate.
`Photoresists are applied at all masking levels in
`manufacture of microelectronic devices. For example, 20-25
`masking levels may be employed during the manufacture of
`commercial devices.
`
`Photoresists have been employed in the fabrication
`of microelectronic devices throughout the history of the
`manufacture of these devices. Early device manufacture
`employed photolithographic techniques in which a photoresist
`film was placed or coated onto a substrate such as silicon,
`imaged with light, and developed into a desired pattern with
`chemical developers.
`The resulting pattern was used as a
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`selective mask in subsequent operations such as ion
`implanting, patterning of the underlying substrate, metal
`plating, as well as various other steps during manufacture
`of these devices.
`
`Early photoresist application methods presented
`problems including poor coating of the photoresist onto the
`substrate, pattern loss due to loss of portions of the
`photoresists by chemical developers, as well as
`"undercutting" of the photoresist by chemical developers.
`Undercutting occurs when an aqueous or organic developer
`migrates along the interface between a polar substrate and
`the photoresist to cause the photoresist to lift off the
`substrate.
`
`The above problems were largely eliminated when
`hexamethyl-disilazane ("HMDS") was employed to pretreat,
`i.e., "prime",
`the silicon substrates prior to application
`of the photoresist.
`Priming the substrates with HMDS was
`found to promote better photoresist coatings, provide more
`uniform photoresist films on the substrates,
`reduce pinholes
`in those films, as well as to reduce undercutting and lift-
`off of the photoresist film during development. These
`improvements were believed due to chemical reaction of HMDS
`with hydrogen-bonded water molecules on the substrate’s
`surface. As a result, yield of devices has been greatly
`improved by HMDS,
`thereby promoting adoption of HMDS as a
`standard pretreatment by manufacturers.
`During priming of silicon substrates with HMDS,
`initial chemical reaction of the HMDS with the hydrogen-
`bonded water molecules produces ammonia,
`trimethylsilanol
`and hexamethyldisiloxane.
`Subsequent reaction of HMDS with
`hydroxyl and oxide groups on the surface of the substrate
`produces a trimethylsiloxy substituted, i.e., silylated
`surface.
`The silylated surface is believed to reduce the
`number of surface polar groups,
`reduce the surface energy
`and provide an essentially monomolecular organic coating on
`the substrate which is compatible with organic photoresists.
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`H. Yanazawa, Colloids And Surfaces, vol. 9, pp. 133-145,
`(1984), describes that the interaction between the organic
`photoresist and the primed substrate surface is probably of
`hydrophobic nature. The hydrophobic trimethylsilyl groups on
`the substrate also repel polar groups such as are present in
`water and aqueous developers to prevent undercutting at the
`substrate-photoresist interface.
`As is known in the art, production of a silylated
`surface occurs when a reactive silicon compound in the
`Silylating agent reacts with a protic species on the surface
`of the substrate to produce a silicon compound bonded to the
`protic species, as well as a protonated, non-bonded by-
`product.
`The degree of surface silylation achieved during
`priming with materials such as HMDS can be gauged by
`measuring "surface contact angle". As is known,
`the higher
`the contact angle,
`the greater is the extent of silylation.
`As is also known, surface contact angle can be measured by
`focusing a commercially available contact angle goniometer
`on a drop of water placed on the silylated substrate.
`A
`high contact angle indicates that greater numbers of
`Silylating groups such as trimethylsilyl groups are bonded
`to the substrate surface. Prior observations by J. L.
`Nistler,
`"A Simple Technique to Analyse Conditions That
`Affect Submicron Photoresist Adhesion", KTI Microelectronics
`
`Seminar - Interface ‘88, pp. 233-247,
`(1988),
`("NISTLER")
`and by W. Moreau, Semiconductor Lithography: Principles,
`Practices, and Materials, Plenum Press, New York,
`(1988),
`("MOREAU") on substrates such as silicon, silicon dioxide
`and silicon nitride indicate that a contact angle of 65-85
`degrees is desirable since dewetting of the photoresist can
`occur above and below these contact angles.
`Improvements to using HMDS to "prime" a substrate
`involve applying liquid HMDS neat, HMDS diluted with one or
`more solvents, and vapor priming wherein vapors of HMDS are
`applied to the surface of a substrate. As known in the art,
`vapor priming can be performed by treating batches of wafers
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`
`in an oven, or by treating individual wafers on an in-line
`track system. Both methods entail heating the wafers under
`vacuum, whereafter HMDS vapor is introduced onto the wafers.
`Generally, priming enables acceptable photoresist
`films or other organic-based films to be applied to the
`primed substrate in subsequent steps.
`An acceptable
`photoresist film is a continuous, uniform film that does not
`exhibit pinholes, edge pullback, beading, blistering, lift
`off or "pop" during exposure, and does not exhibit
`significant lifting or undercutting during chemical
`development. Vapor priming is a preferred method for
`pretreating substrates in the manufacture of high density
`microelectronic devices.
`
`HMDS is the most popular agent for priming of
`wafers. Other agents which have been used to prime
`substrates include trimethylsilyldiethylamine (TMSDEA) and
`trimethylsilyldimethylamine (TMSDMA).
`Priming with HMDS,
`TMSDEA, and TMSDMA, however, can generate basic by-products
`of ammonia, diethylamine and dimethylamine which can
`negatively affect high resolution photoresists.
`High resolution photoresists are typically
`positive or negative aqueous developable compositions which
`have been chemically amplified. These photoresists, upon
`exposure to radiation such as photons, electrons or ions at
`wavelengths of from a few nanometers (X-ray)
`to about 450
`nm, generate minute amounts of acids from compounds such as
`diazonapthaquinones, onium salts, diazoacetoacetates and
`diazoketones which may be present in the photoresist
`composition. These acids are useful to perform reactive
`functions during subsequent steps in the manufacture of the
`chip. These reactive functions include, for example,
`hydrolysis of protecting groups, molecular weight
`modification, and/or cross-linking to increase molecular
`weight and density of the photoresist. These reactive
`functions typically occur after exposure of the photoresist
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`
`to radiation in a post-exposure baking step prior to
`developing the photoresist.
`Recently, it was discovered by S. MacDonald et
`al., Proc. SPIE, 1466;, 2-7 (1991), by W. Hinsberg et al in
`Pro
`SPIE, 1672, 24-32 (1992) and W. Hinsberg et al.
`in
`PMSE Preprints, ACS National Meeting, San Francisco, CA,
`(1992),
`that the acids generated in the photoresist can
`react with trace amounts of residual amines, ammonia or
`other nitrogen-containing by-products generated by priming
`and which remain on the substrate surface and in the
`These
`manufacturing atmosphere Surrounding the substrate.
`by-products, can undesirably neutralize the acids generated
`by the photoresist and thereby adversely affect the quality
`of the photoresist.
`High resolution photoresists typically employed in
`the manufacture of high density microelectronic devices are
`deep ultraviolet, chemically amplified resists ("DUV-CARS") .
`Ammonia and amine-containing by-products generated during
`priming can be especially deleterious to DUV-CARS.
`It has
`been reported by MacDonald et al., Proc. SPIE, 1466: 2-7
`
`(1991),
`that a fifteen minute exposure of DUV-CAR
`photoresists to 15 ppb amines causes scumming or capping.
`The presence of basic by-products and volatile clean room
`contaminants which are ammonia or amines or amine by-
`products have been reported by A. Muller et al.
`in Solid
`State Technology, pp. 61-72, September, 1994,
`to neutralize
`acid groups at the resist surface causing a skin on the
`resist surface ("scumming"), degraded line width control
`and,
`therefore, decreased critical dimension ("CD") control,
`decreased device yield and decreased process reliability.
`Various methods have been introduced to address
`the undesirable effects caused by amine and ammonia
`compounds and by-products. Topcoats which provide a barrier
`coating over the photoresist to prevent contact of the acids
`generated in the photoresist with residual ammonia and amine
`by-products produced during priming with compounds such as
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`HMDS are recommended by resist manufacturers such as IBM,
`ocG, Shin-Etsu and JSR in their applications literature.
`Volatile amines or ammonia have been shown by Berro et al.
`in J.I.E.S.,
`(Nov./Dec. 1993), and D. Kinkhead et al.
`in
`Microcontamination, p. 37 (June 1993),
`to form crystalline-
`like amine salts on wafer surfaces.
`Installation of acidic
`ion filters or scrubbing of air with acidic solutions in the
`manufacturing facilities’ air supply/exhaust recirculation
`system has also been employed to reduce ammonia
`contamination. Removal of airborne ammonia by activated
`carbon filtration has also been attempted. These methods,
`however, are expensive and have met with marginal success in
`control and removal of ammonia/amine contaminants.
`
`A need therefore continues for more reliable and
`
`efficient methods to reduce the amount of basic
`ammonia/amine-type contaminates generated during manufacture
`of microelectronic devices.
`
`Ss
`
`of The
`
`Invention
`
`According to the invention, it has been
`discovered that selected organosilane compounds can be
`employed to silylate a substrate to impart a molecular
`coating substantially equivalent to that obtained with HMDS,
`but without generating undesirable basic by-products such as
`ammonia, or amine-type compounds. Substrates which can be
`silylated include but are not limited to single crystal
`Silicon, polysilicon, silicon dioxide, silicon nitride,
`aluminum, aluminum oxide, copper, copper oxide,
`titanium,
`titanium nitride,
`titanium tungsten, boron phosphorus
`silicon glass, spin-on-glass, and silicides. Application of
`the selected organosilane compounds does not interfere with
`effective functioning of acids generated in photoresists,
`including chemically amplified resists. Application of
`these selected organosilane compounds also promotes uniform
`coating and bonding of photoresists to the substrate.
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`
`The invention employs selected organosilanes to
`silylate the surfaces of substrates such as silicon to
`promote effective application of a photoresist layer onto
`those surfaces.
`The invention solves long-standing problems
`in the art associated with generation of ammonia and amine-
`containing by-products generated during priming of
`substrates.
`The invention also substantially completely
`eliminates overpriming and underpriming to enable
`controllable, reproducible priming by presently available
`equipment with little or no modification and in shorter time
`periods with improved materials economics.
`
`In accordance with the invention, a method for
`substantially eliminating contamination of silylated
`substrates with basic by-products to yield improved bonding
`of polymeric films such as photoresists to a substrate
`surface is provided.
`The method comprises reacting at least
`one organosilane compound, especially trialkylsilane
`compounds and dialkylsilane compounds, with a substrate to
`silylate the substrate. The organosilane compound includes
`hydrolyzable leaving groups which are capable of generating
`by-products which have a pH less than seven.
`Various photoresists can be applied to the
`Silylated surfaces produced by the selected organosilanes
`employed in the invention. These photoresists include, for
`example,
`those compositions which contain compounds such as
`polyvinylphenol, polyhydroxystyrene, poly(t-butyl-carboxy)
`styrene, polyfumerates, poly(t-butoxystyrene) ,
`polyisoprenes,
`formaldehyde novolacs, and polyacrylic
`esters, as well as blends and copolymers thereof with cross-
`linking materials such as cyanurates, and a photoinitiator,
`such as onium salts, diazonaphenates, and azides.
`Especially useful organosilanes for use as
`silylating agents in the invention are trialkylsilanes of
`the formula:
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`- 8 -
`
`CH,
`H,C-Si-X-C-R
`
`Yu
`
`|C
`
`H,
`
`wherein
`
`X is O or NR’;
`Yis oO, CHz, CHR, CHOR, CRR or NR, ;
`R is any of hydrogen, C,-Cg saturated alkyl,
`especially C,-Cg saturated alkyl; C,-Cg saturated cyclic
`alkyl, especially Cg, saturated cyclic alkyl; C1 -Cg
`unsaturated alkyl, especially Cj-C, unsaturated alkyl;
`unsaturated C,-Cg cyclic alkyl, especially C.-C, unsaturated
`cyclic alkyl; C5-C,) fluorinated hydrocarbon alkyl,
`especially C,-C, fluorinated hydrocarbon alkyl; fluorinated
`alkyl, especially C,-Cy fluorinated alkyl; Cy-Cg fluorinated
`cyclic alkyl, especially C.-C, fluorinated cyclic alkyl; C1-
`C3 trialkylsiloxy, especially Me,Si0; trialkylsilyl,
`especially Me3Si; C,-C,5 alkoxy, especially C,-Cy alkoxy;
`phenyl, phenethyl, acetyl, 1-propanol, 2-propanol, alkyl
`ketones such as Co-Ce 1- and 2-alkyl- ketones, especially
`acetyl 2-propanonyl; C3-C,g alpha acetyl esters, especially
`methylacetyl;
`and R? is any of hydrogen, methyl,
`trifluoromethylethyl, or trimethylsilyl.
`Particularly useful trialkylsilanes include those
`of the formula:
`
`trifluoromethyl,
`
`CH,
`H,C-Si-OR*
`CH;
`where R* is any of saturated alkyl such as C,-C¢ alkyl,
`especially methyl, ethyl; unsaturated alkyl such as Co-Cg
`unsaturated alkyl, especially vinyl, allyl; cyclic alkyl
`such as C3,-Cg cyclic alkyl, especially cyclopentyl,
`cyclohexyl; unsaturated cyclic alkenes such as C4-Cg
`unsaturated cyclic alkenes, especially cyclopentenyl,
`cyclohexenyl; fluoroalkyl such as C,-Cg fluoroalkyl alkyl,
`especially trifluoroethyl;
`phenyl, fluorinated phenyl such
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`
`as fluorinated alkyl phenyl and fluorophenyl, especially
`pentafluorophenyl; alkyl ethers such as ethylene glycol
`alkyl and propylene glycol alkyl ethers, especially ethylene
`glycol methyl ether; alkyl ketones such as Cy-Cg alpha keto
`alkenes, especially methacroyl; saturated fluorinated alkyl
`ethers such as C3-Cg perfluoroalkyloxy alkyls, especially
`trifluoromethyloxyethylene; unsaturated fluorinated alkyl
`ethers such as 1-perfluoroalkyl-1-alkoxy ethylenes,
`especially 1-trifluoromethyl-1-ethoxyethylene. Other
`trialkylsilanes which are particularly useful in the
`invention include those of the formula:
`
`3
`
`O
`CH,
`| ll
`H3,C-Si-0O-S-R
`|
`It
`CH,
`O
`wherein R° is any of saturated alkyl such as straight or
`branched chain alkyl, especially methyl; and saturated
`fluoroalkyl such as trifluoroalkyl, especially
`trifluoromethyl.
`Particularly useful trialkylsilanes for use as
`silylating agents in the invention include
`O-trimethylsilyl-acetate (OTMSA), O-
`trimethylsilylproprionate (OTMSP), O-trimethylsilylbutyrate,
`trimethylsilyltrifluoroacetate (TMTFA), tri-
`methylmethoxysilane (TMMS), N-methyl-N-trimethyl-
`silyltrifluoroacetamide (MSTFA),
`0O-
`trimethylsilylacetylacetone (OTMAA) ,
`isopropenoxytrimethylsilane (IPTMS),
`bis(trimethylsilyl)trifluoroacetamide (BSA),
`methyltrimethylsilyldimethylketone acetate (MTDA)
`trimethylethoxysilane (TMES) .
`Dialkylsilanes wherein the silicon atom is
`attached to two reactive hydrolyzable groups, which on
`reaction with the substrate provide an organosilane compound
`on the substrate while generating substantially only acidic
`or neutral by-products, also may be employed as silylating
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`agents in the invention. Particularly useful dialkylsilanes
`include dimethyldimethoxysilane and dimethyldiacetoxysilane.
`The organosilanes employed in the invention may be
`
`applied to the substrate by any one of vapor,
`
`liquid, or
`
`solutions containing the organosilane at temperatures from
`
`about ambient to about 250°F and at pressures from about
`
`The
`atmospheric pressure to less than about 1 torr.
`organosilane can also be admixed with a photoresist and the
`
`mixture applied to the substrate to provide a uniform film
`
`10
`
`on the substrate.
`
`In another aspect of the invention, a silylated
`
`substrate which has adherence for polymeric coatings, such
`
`as photoresists,
`
`that is at least equal to the adherence
`
`achieved by HMDS silylating agents is provided.
`
`15
`
`Detailed Description of the Embodiment
`
`Generally,
`
`the selected organosilanes employed in
`
`the invention have in their molecular structure at least one
`
`reactive, hydrolyzable leaving group bonded to a silicon
`
`20
`
`atom. These organosilanes are alkylsilicon-substituted
`
`monomers which contain at least one hydrolyzable leaving
`group bound to a
`silicon atom.
`The leaving group is a
`
`chemical moiety such as acetate, carboxylate, enol,
`
`alkoxide, sulfate or amide. Upon reaction of the
`organosilane with the substrate during priming,
`the
`
`organosilane can produce acidic or neutral by-products of
`reaction depending on the specific hydrolyzable leaving
`group. These by-products may be described by the Bronsted-
`Lowry system as the conjugate acids of the organosilane
`molecule. Classical Arhenius definition applied to the by-
`products would be molecules with pH in aqueous solutions of
`less than or approximately equal to seven.
`The selected organosilanes employed in the
`invention can be applied neat as liquids, or as solutions in
`organic solvents such as xylene or PGMEA.
`The selected
`organosilanes also can be employed as mixtures with each
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`(I)
`
`other. These selected organosilanes also can be applied
`neat aS vapors, or as vapors in admixture with gaseous
`carriers such as nitrogen and inert gases such as argon.
`During application,
`the selected organosilanes are injected
`as liquid or vapor into a low pressure silylation area
`through an orifice, or by Spraying the organosilane into a
`heated area where the resulting vapor is transported by
`inert gas or vacuum to the substrate to be treated.
`Although not wishing to be bound by theory, it is
`believed that hydrogen ion transfer occurs during priming of
`a substrate as in reaction (I):
`i
`i
`R-Si-X + HO-Z ---> R-Si-O-Z + XH
`|
`!
`R
`R
`where R = methyl
`Kt
`N
`substrate composition
`leaving group
`As shown in (I), during priming of a substrate
`such as silicon,
`the organosilanes employed in the invention
`are believed to react with the substrate to form a surface
`layer of alkylsilyl groups, especially trimethylsilyl
`groups, of approximately one molecule thick on the substrate
`surface. Although not wishing to be bound by theory, it is
`believed that the leaving group of the organosilane, during
`reaction with hydrogen-bonded surface water, hydroxyl groups
`or similar reactive species on the substrate surface accept
`a proton to produce, for example, a trimethylsilyl group
`bound to the substrate.
`The reaction also is believed to
`produce by-products such as acids, alcohols, ketones and
`amides which have neutral or acidic properties depending on
`the hydrolyzable leaving group in the organosilane. These
`by-products can be represented by (II):
`Y
`
`Hl
`
`*
`
`H-x-4-R
`
`(II)
`
`where X is 0, NR’ or CH;
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`Y is O or NR’;
`Zis C or S=0, and
`
`Ris H, Cy-Cg saturated alkyl, Cj-Cg unsaturated
`alkyl, Cyg-Cg unsaturated cyclic alkyl, phenyl, C,-C,
`saturated fluoroalkyl, fluorine containing phenyl such as
`trifluoromethylphenyl, phenethyl, alkyl ketone such as
`acetylmethyl,
`trialkylsiloxy such as trimethylsiloxy,
`alkenylalkylether such as 1-trifluoromethyl-1-
`methoxyethylene, trialkylsilyl such as trimethylsilyl,
`trialkylsilyloxyenolic alkyl such as 2-trimethylsiloxyprop-
`l-enyl and C,-Cg alkoxy, and
`
`R* is H, CH3, CF3,
`
`(CH;)3Si, and CF;CH5-Z.
`
`i
`
`The silylated organosilanes employed in the
`invention can be applied neat as liquid or vapor, preferably
`vapor,
`to a substrate.
`The organosilanes can also be
`employed as solutions in solvents such as hydrocarbons and
`ether esters and the solutions can be applied as liquids or
`vapors to the substrate. Useful hydrocarbon solvents
`include alkanes such as hexane, octane, and the like as well
`
`toluene and the like.
`as aromatic solvents such as xylene,
`Useful ether esters include ethylene glycol methyl ether
`acetate, propylene glycol methyl ether acetate and the like.
`Organosilanes suitable for use in the invention
`include O-trimethylsilyl-acetate (OTMSA), O-
`
`trimethylsilylproprionate (OTMSP), O-trimethylsilylbutyrate,
`trimethylsilyltrifluoroacetate (TMTFA), tri-
`
`methylmethoxysilane (TMMS), N-methyl-N-trimethyl-
`Silyltrifluoroacetamide (MSTFA), methyl-3-
`(trimethylsiloxy) crotonate, bis(trimethylsilyl) acetamide,
`bis (trimethylsilyl) adipate, bis(tri-
`
`methylsilyl)trifluoroacetamide, 3-trimethylsilyl-2-
`oxazoladinone,
`trimethylsilylformate, O-
`
`trimethylsilylacetylacetone (OTMAA),
`isopropenoxytrimethylsilane (IPTMS),
`bis (trimethylsilyl) trifluoroacetamide (BSA),
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`methyltrimethylsilyldimethylketone acetate (MTDA)
`trimethylethoxysilane (TMES). Other organosilanes which may
`be employed include O-trimethylsilylmethacrylate, 2-
`trimethylsiloxypent-2-ene-4-one, 1-
`(trimethylsiloxy) cyclohexene. All of these compounds are
`commercially available.
`Additional compounds which can be employed as the
`selected silanes in the invention include commercially
`available isopropenoxytrimethylsilane and
`organosilylsulfonates of the formula:
`
`3
`
`O
`CH,
`i I
`H,C-Si-O-S-R
`|
`Il
`CH,
`0
`where R is Cy-Cyg alkyl or C,-C, fluoroalkyl. Especially
`suitable organosilylsulfonates include trimethyl -
`silylmethanesulfonate and trimethyl-
`silyltrifluoromethylsulfonate.
`As mentioned, solutions of the selected
`organosilanes in organic solvents can be employed as
`Silylating agents. Suitable organic solvents for use with
`these organosilanes include aliphatic hydrocarbons such as
`n-octane, hexane and the like; aromatic hydrocarbons such as
`toluene, xylene and the like;, aliphatic ethers such as
`methoxy ethylether, diglyme and the like; and ether esters
`such as propylene glycol methyletheracetate (PGMEA),
`ethylene glycol methyl ether acetate and the like.
`Solutions of the selected organosilanes employed
`in the invention may include one or more of the
`aforementioned selected organosilanes with one or more
`organic solvents in a mixture of from about 1:99 to 99:1.
`desirable solution includes OTMSA and PGMEA in a ratio of
`from about 1:99 to 99:1 OTMSA to PGMEA, preferably about
`20:80 OTMSA to PGMEA.
`
`A
`
`The selected organosilanes employed in the
`invention can be applied to silylate a substrate prior to
`applying a photoresist to the substrate in a wide range of
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`concentrations and mixture ratios dependent on the substrate
`composition, process temperatures, and equipment. Specific
`conditions for applying the photoresist can be determined by
`those skilled in the art.
`
`Substrates which can be treated in accordance with
`the invention include, but are not limited to, prime silicon
`wafers and silicon wafers having chemically or thermally
`generated oxide surfaces thereon. As used herein, prime
`silicon wafers are understood to mean unused silicon wafers
`which are taken directly from the manufacturer’s shipment.
`Other substrates which can be treated in accordance with the
`invention include chemical glasses such as borophosphorus
`Silicate glass (BPSG), metal layers such as aluminum,
`titanium,
`tungsten, copper, and chrome, silicon dioxide,
`silicon monoxide, chrome oxide, silicon nitride, aluminum
`oxide,
`titanium oxide, copper oxide, as well as various
`metal silicides such as aluminum silicide deposited on
`Silicon nitride and titanium nitride.
`Silylating of a substrate by direct vapor
`application of one or more of the selected organosilanes
`employed in the invention can be performed with commercially
`available vapor priming equipment.
`Examples of useful
`priming equipment
`include Genesis Microstar 200, Genesis
`2020 vapor prime unit, Genesis 2010 vapor prime unit,
`Genesis 2002 vapor prime oven, Yield Engineering Systems,
`Inc. priming equipment,
`in-line vapor track systems such as
`those manufactured by Silicon Valley Group, and liquid
`dispenser track systems.
`Silylating by direct vapor application, as is
`known in the art,
`is performed by transporting a mixture of
`vapors of one or more of the selected organosilanes in gases
`such as nitrogen or argon within vapor priming equipment, or
`by differential pressure flow of vapors of the organosilanes
`in vapor priming equipment to the substrate to be silylated.
`The specific amounts of the selected organosilane compound
`employed in the vapor mixture can vary from about 10 to
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`flow, exposure time and
`
`100,000 ppm depending on the system,
`vacuum employed.
`Silylation by direct application of vapor to the
`substrate can be performed at temperatures of about 10°C to
`about 200°C , preferably about 50°C to about 150°C.
`Silylation in accordance with the invention enables uniform
`organic films to be deposited onto the silylated surface of
`the substrate. Examples of films which can be deposited
`over the silylated surface include photoresists,
`silicon
`polyimides such as those products produced by Amoco Chemical
`Co. and Micro SI Inc., especially ALTISIL 115, 129, 1000 ana
`2000, polyacrylates such as any of those mentioned above and
`including polymethylmethacrylate polyimides such as those
`commercial products produced by Amoco Chemical Co., Dupont
`Electronics, National Starch and Chemical Co.,
`to name but a
`few, novolac-based films such as those products produced by
`Micro SI Inc., OCG Microelectronic Materials,
`Inc., Shipley
`Co., Inc., and planarizing layers such as those produced by
`Filmtronics, Futurrex, OCG Microelectronic Materials, Inc.,
`and Dow Chemical Co.
`Photoresists can be applied to the silylated
`surfaces produced by the selected organosilanes employed in
`the invention by methods known in the art. These
`photoresists are typically high resolution positive or
`negative tone, chemically amplified compositions which
`contain acyanurate and a photoinitiator. Useful
`photoresists include organic solutions of photoactivated
`polymers which contain photoinitiators. Useful
`photoinitiators include onium salts or mixtures such as
`diaryliodonium, arylalkyliodonium,
`triarylsulfoniun,
`arylakylsulfonium,
`trialkylsulfonium hexafluorophosphates,
`hexafluoroarsenates, hexafluoroantimonates and tosylates,
`especially 4-thiophenoxyphenyl diphenyl sulfonium
`hexafluoroantimonate, di(4-tert--~butylphenyl) iodonium
`hexafluorophosphate and dilauryl-4-t-“butylphenylsulfonium
`hexafluoroantimonate; diazonapthenates,such as
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`diazoquinonesulfonic acids or diazoquinonecarboxylic acids,
`especially 6-diazo-3,4-dihydro-4-oxo-1-napthene sulfonic
`acid; and azides,such as bisarylazides, especially
`2,bis(4,4+ diazidophenyl-2,27-ethylene) -4-methylcyclo-
`hexanone. These photoinitiators are reactive to light
`between the wavelengths of 436 nm to 190 nm. Examples of
`useful photoresist compositions include but are not limited
`
`to those available from Shipley Co., Inc., Hoechst Celanese
`
`(AZ Photoproducts Division), Tokyo Ohka Chemical Co.,
`Corp.
`Ltd., Shin-Etsu Chemical Co., Ltd., OCG Microelectronic
`Materials, Japan Synthetic Rubber Co., Ltd.,
`IBM, Hitachi
`Ltd., and BASF Ltd. Specific photoresists include Shipley’s
`SNR200, SAL601, SAL603, XP-3115, XP8844;
`IBM’s Apex and AST;
`OCG’s Camp 6, BASF ST2; and Hoechst’s AZPN114, Ray-PN and
`JSR‘'S PFR 1X750.
`
`the photoresist can
`In an alternative embodiment,
`be applied in admixture with the organosilanes employed in
`the invention.
`A mixture of photoresist material and at
`least one of the selected organosilanes employed in the
`the
`invention may be applied to the substrate. Typically,
`mixture may be applied by mixing a selected organosilane of
`this invention with the photoresist material in an amount of
`0.1 to 1.0% of the weight of the photoresist solution and
`applying the solution to spinning substrates as per the
`photoresist manufacturers’
`instructions.
`
`The photoresists can be applied to a substrate
`silylated with the organosilanes employed in the invention
`in a predefined pattern and thereafter developed by known
`methods. Typ