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`Case 6:20-cv-01216-ADA Document 41-15 Filed 10/06/21 Page 1 of 11
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`EXHIBIT 15
`EXHIBIT 15
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`case 6:20-ev-01216-ADA DocumentBI AMAT RAREETI
`Case 6:20-cv-01216-ADA Document 41-15 Filed 10/06/21 Page 2 of 11
`US006451512B1
`
`United States Patent
`US 6,451,512 B1
`(10) Patent No.:
`(12)
`Rangarajanet al.
`Sep. 17, 2002
`(45) Date of Patent:
`
`11/1997 Okamoto et al.
`........... 437/228
`5,688,723 A
`1/1998 Stauffer et al.
`...... « 430/313
`5,707,783 A
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`3/1999 Daietal. w.... . 438/597
`5,877,075 A
`2/2001 Jung etal. 0. 430/315
`6,190,837 B1
`FOREIGN PATENT DOCUMENTS
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`WO
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`9733199
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`Q/IL99T eee G03F/7/09
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`OTHER PUBLICATIONS
`
`Haring and Stewart, “X-ray photoelectron spectroscopy and
`infrared study of the processing of a silylated positive
`photoresist,” Journal of Vacuum Science & Technology, B9
`(1991) Nov./Dec., No. 6, New York, US, pp. 3406-3412.
`
`* cited by examiner
`
`Primary Examiner—Kathleen Duda
`(74) Attorney, Agent, or Firm—Amin & Turocy, LLP
`
`(57)
`
`ABSTRACT
`
`invention relates to a
`the present
`In one embodiment,
`method of processing an ultrathin resist, involving the steps
`of depositing the ultra-thin photoresist over a semiconductor
`substrate, the ultra-thin resist having a thickness less than
`about 3,000 A; irradiating the ultra-thin resist with electro-
`magnetic radiation having a wavelength of about 250 nm or
`less; developing the ultra-thin resist; and contacting the
`ultra-thin resist with a silicon containing compound in an
`environmentof at least one of ultraviolet light and ozone,
`wherein contact of the ultra-thin resist with the silicon
`containing compound is conducted betweenirradiating and
`developing the ultra-thin resist or after developing the
`ultra-thin resist.
`
`19 Claims, 2 Drawing Sheets
`
`(54)
`
`(75)
`
`UV-ENHANCED SILYLATION PROCESS TO
`INCREASE ETCH RESISTANCE OF ULTRA
`THIN RESISTS
`
`Inventors: Bharath Rangarajan, Santa Clara;
`Ramkumar Subramanian; Khoi A.
`Phan, both of San Jose; Bhanwar
`Singh, Morgan Hill; Michael K.
`Templeton, Atherton; Sanjay K.
`Yedur, Santa Clara; Bryan K. Choo,
`Mountain View, all of CA (US)
`
`(73)
`
`Assignee: Advanced Micro Devices, Inc.,
`Sunnyvale, CA (US)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`US.C. 154(b) by 0 days.
`
`(21)
`
`(22)
`
`(61)
`(52)
`(58)
`
`(56)
`
`Appl. No.: 09/565,691
`
`Filed:
`
`May1, 2000
`
`Tint, C17 occ cesescseseseecsesees G03F 7/00
`US. Che cece 430/313; 430/296; 430/328
`Field of Search ............0..cc cece 430/296, 311,
`430/313, 315, 323, 324, 325, 328
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`Mimura ......... se eeeeeeeeeee 430/296
`
`McGolgin et al.
`.......... 430/323
`Tto et al. vo eeeeeeeeeee 430/313
`Kim etal.
`156/661.11
`Nakato et al. ww... 428/451
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`y"
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`4,751,170 A *
`4,931,351 A
`5,407,786 A
`5,427,649 A
`5,486,424 A
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`6/1990
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`6/1995
`1/1996
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`Case 6:20-cv-01216-ADA Document 41-15 Filed 10/06/21 Page 3 of 11
`Case 6:20-cv-01216-ADA Document 41-15 Filed 10/06/21 Page 3 of 11
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`U.S. Patent
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`Sep. 17, 2002
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`Sheet 1 of2
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`US 6,451,512 B1
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`my
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`Fig. 1
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`Case 6:20-cv-01216-ADA Document 41-15 Filed 10/06/21 Page 4 of 11
`Case 6:20-cv-01216-ADA Document 41-15 Filed 10/06/21 Page 4 of 11
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`U.S. Patent
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`Sep. 17, 2002
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`Sheet 2 of2
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`US 6,451,512 B1
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`Case 6:20-cv-01216-ADA Document 41-15 Filed 10/06/21 Page 5 of 11
`Case 6:20-cv-01216-ADA Document 41-15 Filed 10/06/21 Page 5 of 11
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`US 6,451,512 B1
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`1
`UV-ENHANCED SILYLATION PROCESS TO
`INCREASE ETCH RESISTANCE OF ULTRA
`THIN RESISTS
`
`TECHNICAL FIELD
`
`The present invention generally relates to increasing the
`etch resistance of an ultra-thin resist.
`In particular,
`the
`present invention relates to silylating an ultra-thin resist
`which in turn increases its etch resistance.
`
`BACKGROUND ART
`
`In the semiconductor industry, there is a continuing trend
`toward higher device densities. To achieve these high
`densities, there has been and continues to be efforts toward
`scaling down the device dimensions on semiconductor
`wafers. In order to accomplish such high device packing
`density, smaller and smaller features sizes are required. This
`includes the width and spacing of interconnecting lines and
`the surface geometry such as corners and edges of various
`features. Since numerousinterconnecting lines are typically
`present on a semiconductor wafer, the trend toward higher
`device densities is a notable concern.
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`The requirement of small features, such as metal lines,
`with close spacing between adjacent features requires high
`resolution photolithographic processes. In general, lithogra-
`phyrefers to processes for pattern transfer between various
`containing compound is conducted betweenirradiating and
`media. It is a technique used for integrated circuit fabrication
`developing the ultra-thin resist or after developing the
`ultra-thin resist.
`in whichasiliconslice, the wafer, is coated uniformly with
`a radiation-sensitive film, the resist, and an exposing source
`In another embodiment, the present invention relates to a
`(such as optical light, X-rays, or an electron beam) illumi-
`method of increasing the etch resistance of an ultra-thin
`nates selected areas of the surface through an intervening
`resist, involving the steps of irradiating the ultra-thin resist
`master template, the photomask,for a particular pattern. The
`with electromagnetic radiation having a wavelength of about
`lithographic coating is generally a radiation-sensitized coat-
`250 nm orless, the ultra-thin resist having a thickness less
`than about 3,000 A; developing the ultra-thin resist; and
`ing suitable for receiving a projected image of the subject
`pattern. Once the image is projected,it is indelibly formed
`contacting the ultra-thin resist with a silicon containing
`in the coating. The projected image maybeeither a negative
`compound to incorporate silicon atoms into the ultra-thin
`or a positive of the subject pattern. Exposure of the coating
`resist in at least one of under ultraviolet light and in an
`through the photomask causes a chemical transformation in
`atmosphere comprising at least about 5% by weight ozone,
`wherein contact of the ultra-thin resist with the silicon
`the exposed areas of the coating thereby making the image
`area either more or less soluble (depending on the coating)
`containing compound is conducted betweenirradiating and
`in a particular solvent developer. The more soluble areas are
`developing the ultra-thin resist or after developing the
`ultra-thin resist.
`removed in the developing process to leave the pattern
`image in the coating as less soluble polymer.
`Projection lithography is a powerful and essential tool for
`microelectronics processing. However, lithography is not
`without limitations. Patterning features having dimensions
`of about 0.25 um, 0.18 um or less with acceptable resolution
`is difficult. This is because photoresist layers used in lithog-
`raphy typically have thicknesses on the order of 7,000 Aand
`higher. Such relatively thick photoresist layers are not con-
`ducive to making small patterned dimensions with good
`resolution.
`Using relatively thin photoresists (such as less than about
`5,000 A) enables the patterning of smaller and smaller
`dimensions. However,
`insufficient etch protection during
`semiconductor processing is associated with using thin
`photoresists. The relatively thin patterned photoresists sim-
`ply do notprotect underlying surfaces during etch steps. For
`example, corner rounding of layers underneath relatively
`thin photoresists is caused by insufficient etch protection and
`results in poor definition/resolution. In many instances the
`relatively thin patterned photoresists are removed during an
`etch procedure. As a result, it is often necessary to employ
`the use of hardmasks when using thin photoresists in sub-
`tractive semiconductor processing techniques.
`Improved
`lithography procedures providing improved resolution and
`improved etch resistance are therefore desired.
`
`2
`SUMMARYOF THE INVENTION
`
`The present invention generally provides methods that
`lead to improved etch resistance, improved critical dimen-
`sion control and/or improved resolution in patterned ultra-
`thin resists. Sinceit is possible to enhancethe etch resistance
`of ultra-thin photoresists,
`the present
`invention provides
`improved methods for etching layers underneath patterned
`ultra-thin photoresists including metal layers. The methods
`of the present invention makeit possible to etch trenches,
`holes and other openings on the order of about 0.18 wm or
`less in size. The methods of the present invention also make
`it possible to avoid the use of hardmasks when using
`ultra-thin photoresists. As a result,
`the present invention
`effectively addresses the concerns raised by the trend
`towards the miniaturization of semiconductor devices.
`
`the present invention relates to a
`In one embodiment,
`method of processing an ultra-thin resist, involving the steps
`of depositing the ultra-thin photoresist over a semiconductor
`substrate, the ultra-thin resist having a thickness less than
`about 3,000 A; irradiating the ultra-thin resist with electro-
`magnetic radiation having a wavelength of about 250 nm or
`less; developing the ultra-thin resist; and contacting the
`ultra-thin resist with a silicon containing compound in an
`environmentof at least one of ultraviolet light and ozone,
`wherein contact of the ultra-thin resist with the silicon
`
`In yet another embodiment, the present invention relates
`to a method of patterning a semiconductor layer on a
`semiconductor substrate, involving the steps of depositing
`an ultra-thin photoresist over the semiconductor layer, the
`ultra-thin resist having a thickness less than about 3,000 A;
`irradiating the ultra-thin resist with electromagnetic radia-
`tion having a wavelength of about 250 nm orless; devel-
`oping the ultra-thin resist thereby exposing a portion of the
`semiconductor layer through an opening in the ultra-thin
`resist; contacting the ultra-thin resist with a silicon contain-
`ing compound in an environment of at least one of ultra-
`violet light and ozone, wherein contactof the ultra-thin resist
`with the silicon containing compound is conducted between
`irradiating and developingthe ultra-thin resist or after devel-
`oping the ultra-thin resist; and etching the exposed portion
`of the semiconductor layer thereby patterning the semicon-
`ductor layer.
`BRIEF DESCRIPTION OF DRAWINGS
`FIG. 1 illustrates in a cross-sectional view of a method
`according to one aspect of the present invention.
`FIG. 2 illustrates in a cross-sectional view of a method
`according to one aspect of the present invention.
`FIG. 3 illustrates in a cross-sectional view of a method
`
`according to one aspect of the present invention.
`
`

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`US 6,451,512 B1
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`3
`FIG. 4 illustrates in a cross-sectional view of a method
`according to one aspect of the present invention.
`FIG. 5 illustrates in a cross-sectional view of a method
`
`according to one aspect of the present invention.
`FIG. 6 illustrates in a cross-sectional view of a method
`according to one aspect of the present invention.
`FIG. 7 illustrates in a cross-sectional view of a method
`
`according to one aspect of the present invention.
`FIG. 8 illustrates in a cross-sectional view of a method
`according to one aspect of the present invention.
`
`DISCLOSURE OF THE INVENTION
`
`The present invention involves etching extremely fine
`patterns using an ultra-thin resist having improved etch
`resistance. The present invention more specifically involves
`silylating an ultra-thin resist under an ultraviolet (UV) light
`atmosphere or an ozone atmosphere which enables high
`resolution patterning of underlying layers having features on
`the order of about 0.18 um or less, and even about 0.13 wm
`or less. The patterned and silylated an ultra-thin resist
`minimizes corner rounding problems and insufficient etch
`protection commonly associated with thinningresists.
`As a result of the present invention, etch resistance to at
`least one of wet, dry, gas, plasma, and liquid etchants is
`improved. Improved etch resistance permits the ultra-thin
`resists processed in accordance with the present invention to
`be used, without hadmasks, in patterning metal lines a and
`other structures that require aggressive etchants. Resolution
`and critical dimension control are also improved by the
`strengthened ultra-thin resists.
`An ultra-thin resist is initially provided over a semicon-
`ductor substrate. The semiconductor substrate may include
`any suitable semiconductor material (one or more layers of
`semiconductor materials), for example, a monocrystalline
`silicon substrate. Semiconductor substrates may include of
`one or more layers including substrate layers, diffusion
`regions, dielectric layers such as oxides and nitrides, metal
`layers, devices, polysilicon layers, and the like (all of which
`are collectively termed semiconductor layers). The top layer
`of the semiconductor substrate serves as the underlying layer
`once an ultra-thin photoresist layer is formed thereover.
`An ultra-thin photoresist layer is formed over the semi-
`conductor substrate. The ultra-thin photoresist is deposited
`over the semiconductor substrate using any suitable tech-
`nique. For example, the ultra-thin photoresist is deposited
`using conventional spin-coating or spin casting techniques.
`Ultra-thin photoresists in accordance with the present
`invention have a thickness of about 3,000 A orless. In one
`embodiment, the ultra-thin photoresist layer has a thickness
`from about 200 A to about 3,000 A. In another embodiment,
`the ultra-thin photoresist layer has a thickness from about
`500 A to about 2,500 A (about 2,500 A or less). In yet
`another embodiment, the ultra-thin photoresist layer has a
`thickness from about 700 A to about 2,000 A (about 2,000
`A orless).
`The ultra-thin photoresist layer has a thickness suitable
`for functioning as a mask for etching an underlying layer and
`for forming patterns or openings in the developed ultra-thin
`photoresist layer that are about 0.18 zm or less. Since the
`ultra-thin photoresist layer is relatively thin compared with
`I-line photoresists and other photoresists, improvedcritical
`dimension controlis realized.
`
`Ultra-thin resists are typically processed using small
`wavelength radiation. As used herein, small wavelength
`radiation means electromagnetic radiation having a wave-
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`length of about 250 nm orless, including e-beams and
`X-rays. In one embodiment, small wavelength radiation
`includes electromagnetic radiation having a wavelength of
`about 200 nm orless. In another embodiment, small wave-
`length radiation includes extreme UV electromagnetic radia-
`tion having a wavelength of about 25 nm or less. In yet
`another embodiment, small wavelength radiation includes
`extreme UVelectromagnetic radiation having a wavelength
`of about 15 nm orless, including e-beams and X-rays.
`Small wavelength radiation increases precision and thus
`the ability to improve critical dimension control and/or
`resolution. Specific examples of wavelengths to which the
`ultra-thin photoresists are sensitive (undergo chemicaltrans-
`formation enabling subsequent development) include about
`248 nm, about 193 nm, about 157 nm, about 13 nm, about
`11 nm, about 1 nm, and e-beams. Specific sources of
`radiation include KrF excimerlasers having a wavelength of
`about 248 nm, a XeHg vapor lamp having a wavelength
`from about 200 nm to about 250 nm, mercury-xenon arc
`lampshaving a wavelength of about 248 nm, an ArF excimer
`laser having a wavelength of about 193 nm, an F, excimer
`laser having a wavelength of about 157 nm, extreme UV
`light having wavelengths of about 13.5 nm and/or about 11.4
`nm, and X-rays having a wavelength of about 1 nm.
`In embodiments where the patterns or openings formed in
`the subsequently developed ultra-thin photoresist layer are
`from about 0.1 um to about 0.15 wm, a 157 nm sensitive
`photoresist or a 193 nm sensitive photoresist is preferably
`employed. In embodiments where the patterns or openings
`formed in the subsequently developed ultra-thin photoresist
`layer are about 0.1 um orless, a 13 nm sensitive photoresist
`or an 11 nm sensitive photoresist (extreme UV photoresist)
`is preferably employed.
`Positive or negative ultra-thin photoresists may be
`employed in the methods of the present invention. General
`examples of ultra-thin photoresists include those containing
`a partially t-butoxycarbonyloxy substituted poly-p-
`hydroxystyrene, melamine-formaldehyde polymers,
`polyvinylpyrrolidone, polymethylisoprenylketone,
`a
`novolak, a polyvinylphenol, polymers of hydroxystyrene
`and acrylate, methacrylate polymers or a mixture of acrylate
`polymers and methacrylate polymers. Further specific
`examples include poly (p-tertbutoxycarbonyloxy-a-
`methylstyrene), poly(p-tert-butoxycarbonyloxystyrene),
`poly(tert-butyl p-vinylbenzoate), poly(tert-butyl
`p-isopropenylphenyloxyacetate), and poly(tert-butyl
`methacrylate). Photoresists are commercially available from
`a numberof sources, including Shipley Company, Kodak,
`Hunt, Arch Chemical, Aquamer, JSR Microelectronics,
`Hoechst Celanese Corporation, and Brewer.
`After the ultra-thin resist is deposited over a semiconduc-
`tor substrate,
`the structure including the semiconductor
`substrate and ultra-thin resist is optionally heated. Heating
`serves to promote removal of excess solvent employed to
`deposit the ultra-thin resist.
`The ultra-thin resist layer is then selectively exposed to
`actinic radiation. In particular, the ultra-thin resist layer is
`exposed to a pattern of radiation having a relatively small
`wavelength (for example, less than 250 nm); thatis, selected
`portions of the ultra-thin resist layer are exposed to actinic
`radiation through a mask, leaving the ultra-thin resist layer
`with exposed and unexposed portions. Actinic radiation
`includesrelatively small wavelength less than 250 nm and
`e-beams. A numberof exemplary wavelengths are described
`above in connection with the ultra-thin resists.
`
`Following an image-wise exposure to actinic radiation,
`the ultra-thin resist layer is silylated under a UV or ozone
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`US 6,451,512 B1
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`5
`environment. In one embodiment, silylation is conducted
`after an image-wise exposure and before development. In
`another embodiment, silylation is conducted after develop-
`ment. Whensilylation is conducted after an image-wise
`exposure and before development, the portions of the ultra-
`thin resist layer that remain after developmentare silylated
`(the exposed portions in positive ultra-thin resists and the
`unexposed portions in negative ultra-thin resists); thus, the
`ultra-thin resist layer is silylated in patterned manner.In yet
`another embodiment, silylation is conducted after an image-
`wise exposure and before development and again after
`development. Such double silylation further increases the
`etch resistance of the ultra-thin resists.
`
`Silylation involves contacting the ultra-thin resist with a
`silicon containing compound in an UV or ozone environ-
`ment in any suitable manner. The silicon containing com-
`pound is any chemical compound containing a molecule of
`silicon that can be incorporated into an ultra-thin resist.
`Silicon containing compoundsinclude silane and organo-
`silicon compounds. Organosilicon compounds include
`monofunctional organosilicon compounds, difunctional
`organosilicon compounds,and polyfimctional organosilicon
`compounds. Thesilicon containing compound(s) employed
`are in the form of at least one of a vapor and liquid.
`Specific examples of silicon containing compounds
`include silane, hexamethyldisilazane (HMDS), trimethylsi-
`lyldiethylamine (TMSDEA),
`trimethylsilyldimethylamine
`(TMSDMA), dimethylsilyldiethylamine (DMADEA), dim-
`ethylsilyldimethylamine (DMSDMA),
`tetramethyldisila-
`zane (TMDS),trimethylmethoxysilane (TMMS), trimethyl-
`ethoxysilane (TMES),
`trimethylpropoxysilane (TMPS),
`trimethylacetoxysilane (TMAS), bis(dimethylamino)
`dimethylsilane (BDMADMS), bis(dimethylamino)
`methylsilane (BAMS), methyldimethylaminoethoxysilane
`(MDAES), methyldimethoxysilane (MDMS), methyldiethy-
`oxysilane (MDES), dimethyldimethoxysilane (DMDS),
`dimethyldiethoxysilane (DMES), and methyltrimethoxysi-
`lane (MTMS), and the like. In one embodiment, onesilicon
`containing compound is employed. In another embodiment,
`two or moresilicon containing compounds are employed. In
`yet another embodiment, three or more silicon containing
`compounds are employed.
`The monofunctional organosilicon compound has one or
`moresilicon atoms and a single hydrolyzable moiety bonded
`to a silicon atom. The compound may thus contain a single
`silicon atom bonded to a single hydrolyzable moiety. In
`cases involving a hydrolyzable moiety that has a valence of
`twoorgreater, the organosilicon compound maycontain two
`or more silicon atoms bonded to a common hydrolyzable
`moiety that is the only hydrolyzable moiety in the com-
`pound. The term “monofunctional”is used to denote that the
`reaction between the organosilane and the polymerresults in
`silicon atoms each bearing only a single linkage to the
`polymerat the location of a reactable group on the polymer,
`even if the organosilicon compound reactant contains more
`than one silicon atom. Thus, the monofunctional organosili-
`con compound doesnot crosslink the resist polymer chains.
`The di-or polyfunctional organosilicon compoundhas one
`or more silicon atoms and at least two hydrolyzable moi-
`eties. Upon reaction with the reactable groups on theresist
`polymer, the organosilicon compoundjoins two or more of
`the reactable groups, thereby crosslinking the polymer. The
`organosilicon compound may thus contain a single silicon
`atom bondedto two or more hydrolyzable moieties, or two
`silicon atoms joined by a nonhydrolyzable linkage but each
`bonded individually to a separate hydrolyzable moiety, or
`other variations. The term “di-or polyfunctional” is used to
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`denote that the reaction between the organosilicon com-
`pound and the resist polymer results in a silicon atom
`crosslinking the polymer chains by simultaneously bonding
`to the locations of two or more reactable groups on different
`chains.
`
`The term “hydrolyzable group” denotes any group that
`when bonded to a silicon atom can be cleaved from the
`silicon atom upon reaction of the organosilicon compound
`with the reactable group on the resist polymer. Examples of
`such hydrolyzable groups are amino (NH,), alkylamino
`(—NHR,whereR is alkyl), dialkylamino (—NR,R,, where
`R, and R, are independently alkyl), alkanoylamino (—NHC
`(O)R, where R is alkyl), alkoxy (—OR,where R is alkyl),
`and alkanoyloxy (—OC(O)R, where R is alkyl). Specific
`examples are dimethylamino, diethylamino, methoxy,
`ethoxy, propoxy, acetoxy, propionyloxy (—OC(O)C.Hs),
`and butyryloxy (—OC(O)C,H.).
`The time that the silicon containing compound is con-
`tacted with the ultra-thin resist layer is sufficient to promote
`incorporation of a suitable amountofsilicon atomsinto the
`ultra-thin resist to improvethe etch resistance thereof. In one
`embodiment, the silicon containing compound is contacted
`with the ultra-thin resist layer for a time from at least about
`10 seconds, or from about 10 seconds to about 1 hour. In
`another embodiment,
`the silicon containing compound is
`contacted with the ultra-thin resist layer for a time from at
`least about 30 seconds, or from about 30 secondsto about 10
`minutes. In yet another embodiment, the silicon containing
`compound is contacted with the ultra-thin resist layer for a
`time from at least about 50 seconds, or from about 50
`seconds to about 3 minutes.
`
`The temperature at which the silicon containing com-
`poundis contacted with the ultra-thin resist layer is sufficient
`to promote incorporation of a suitable amount of silicon
`atomsinto the ultra-thin resist to improvethe etch resistance
`thereof. In one embodiment,
`the silicon containing com-
`pound is contacted with the ultra-thin resist
`layer at a
`temperature from about 50° C. to about 250° C. In another
`embodiment, the silicon containing compound is contacted
`with the ultra-thin resist layer at a temperature from about
`60° C. to about 200° C. In yet another embodiment, the
`silicon containing compoundis contacted with the ultra-thin
`resist layer at a temperature from about 70° C. to about 180°
`C.
`
`In embodiments where the silicon containing compound
`is in the form of a gas/vapor,
`the pressure employed is
`sufficient to promote incorporation of a suitable amount of
`silicon atoms into the ultra-thin resist to improve the etch
`resistance thereof. In one embodiment, the silicon contain-
`ing compound is contacted with the ultra-thin resist layer
`under a pressure from about 10 torr to about 800 torr. In
`another embodiment,
`the silicon containing compound is
`contacted with the ultra-thin resist layer under a pressure
`from about 25 torr to about 500 torr. In embodiments where
`
`the silicon containing compoundis in the form of a liquid,
`the pressure employedis typically ambient, but in the range
`of 100 torr to 1,000 torr.
`In embodiments where the silicon containing compound
`is in the form of a gas/vapor, the gas may further contain an
`inert gas. Inert gases include the noble gases, such as helium,
`neon, argon, krypton and xenon, and nitrogen. In embodi-
`ments where the silicon containing compoundis in the form
`of a liquid, the liquid may further contain an inert liquid
`(inert to the incorporation ofsilicon atoms into an ultra-thin
`resist) such as an organic solvent.
`The silicon containing compound is contacted with the
`ultra-thin resist layer in an UV or ozone environment. In one
`
`

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`Case 6:20-cv-01216-ADA Document 41-15 Filed 10/06/21 Page 8 of 11
`Case 6:20-cv-01216-ADA Document 41-15 Filed 10/06/21 Page 8 of 11
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`US 6,451,512 B1
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`7
`embodiment, the silicon containing compoundis contacted
`with the ultra-thin resist layer under UV light. In another
`embodiment, the silicon containing compoundis contacted
`with the ultra-thin resist layer under an ozone containing
`atmosphere. In yet another embodiment, the silicon contain-
`ing compound is contacted with the ultra-thin resist layer
`under UV light and an ozone containing atmosphere.
`UV light as used herein means light or electromagnetic
`radiation having a wavelength from about 5 nm to about 390
`nm. As the silicon containing compound is contacted with
`the ultra-thin resist layer, UV light is directed at and/or
`above the structure containing the semiconductor substrate
`and the ultra-thin resist layer. Any suitable UV light source
`may be employed to irradiate the chamber in whichsilyla-
`tion is performed. The UV light may be continuous or
`intermittent.
`
`An ozone containing atmosphere contains at least about
`5% by weight ozone (O3). In another embodiment, the ozone
`containing atmosphere contains at
`least about 10% by
`weight ozone. In yet another embodiment, the ozone con-
`taining atmosphere contains at least about 20% by weight
`ozone. The ozone containing atmosphere may additionally
`contain inert gases and/or other gases that do not effect the
`incorporation of silicon atomsinto the ultra-thin resist. The
`ozone gas may be derived from any suitable ozone source.
`For example, ozone may be derived from oxygen using an
`ozone generator. Methods of making ozone are knownin the
`art.
`
`The ultra-thin photoresist layer is developed to provide a
`patterned ultra-thin photoresist. The selectively exposed
`ultra-thin photoresist layer is developed by contact with a
`suitable developer that removes either the exposed or unex-
`posed portions of the ultra-thin photoresist layer. The iden-
`tity of the developer depends upon the specific chemical
`constitution of the ultra-thin photoresist layer. Typically, for
`example, an aqueous alkaline solution may be employed to
`remove unexposed portions of the ultra-thin photoresist
`layer. Alternatively, one or more of dilute aqueous acid
`solutions, hydroxide solutions, water, organic solvent solu-
`tions may be employed to remove selected portions of the
`ultra-thin photoresist layer. Optionally, the developed ultra-
`thin photoresist layer is washed before proceeding.
`In embodiments where silylation is conducted after
`development, or after development in addition to immedi-
`ately after the image-wise exposure, the patterned ultra-thin
`photoresist layer is contacted by a silicon containing com-
`pound in a UV or ozone environment. The same conditions
`and components discussed above in connection with silyla-
`tion are applicable here, and therefore, they are repeated.
`is
`While not wishing to be bound by any theory,
`it
`believed that
`the UV or ozone environment accelerates
`incorporation of silicon atoms into the ultra-thin resist,
`which in turn, increases the etch resistance of the patterned
`ultra-thin resist. In particular, the UV or ozone environment
`may induce decomposition of the silicon containing com-
`pound in a manner that promotes incorporation of silicon
`atomsinto the ultra-thin resist.
`
`Thesize of the cross-section of the exposed portion of the
`underlying layer of the semiconductor substrate is about
`0.18 zm or less, including about 0.15 wm orless, about 0.13
`um or less and about 0.1 xm or less, depending uponthe type
`of radiation employed. Larger cross-sections are thus easily
`obtainable.
`
`The present invention is now discussed in conjunction
`with the Figures. FIGS. 1-5 illustrate one embodimentofthe
`present invention while FIGS. 1, 2 and 6-8 illustrate another
`
`10
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`15
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`20
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`25
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`30
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`35
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`40
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`45
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`50
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`55
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`60
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`65
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`8
`invention. The procedures
`embodiment of the present
`described in the Figures may be used with any suitable
`semiconductor technology including but not
`limited to
`NMOS, PMOS, CMOS, BiCMOS, bipolar, multi-chip mod-
`ules (MCM)and III-IV semiconductors.
`In one embodiment, referring to FIG. 1, a semiconductor
`structure 10 including a semiconductor substrate 12 having
`an underlying layer 14 thereover is provided (underlying
`with respect to the subsequently described ultra-thin resist
`layer). Semiconductor substrate 12 may include any suitable
`semiconductor material (one or more layers of semiconduc-
`tor materials), for example, a monocrystalline silicon sub-
`strate. Semiconductor substrate 12 may additionally include
`of one or more layers including substrate layers, diffusion
`regions, dielectric layers such as oxides and nitrides,
`devices, polysilicon layers, and the like. Although shown as
`continuous, the underlying layer 14 may be continuous or
`intermittent. That is, underlying layer 14 may coverall or
`portion of semiconductor substrate 12. The underlying layer
`14 is typically a silicon based layer such as polysilicon, a
`dielectric layer, a metal layer, or a silicide layer. In this
`embodiment, the underlying layer 14 is a conductive metal
`layer. Specific examples of metal layers include one or more
`of aluminum, copper, gold, nickel, palladium, platinum,
`silver, tantalum,titanium, tungsten, zinc, aluminum-copper
`alloys, aluminum alloys, copper alloys,
`titanium alloys,
`tungsten alloys, titantum-tungsten alloys, gold alloys, nickel
`alloys, palladium alloys, platinum alloys, silver alloys, tan-
`talum alloys, zinc alloys, and any other alloys thereof.
`An ultra-thin photoresist layer 16 is then formed over the
`underlying layer 14. The ultra-thin photoresist is deposited
`over the underlying layer 14 using any suitable technique,
`such as conventional spin-coating or spin casting tech-
`niques. The ultra-thin photoresist layer 16 has a thickness of
`about 1,000 A orless. Since the ultra-thin photoresist layer
`16 is relatively thin compared with I-line and other
`photoresists, improved resolution over I-line photoresists is
`realized. In this embodiment, the ultra-thin photoresist layer
`16 is a positive type extreme UV photoresist.
`Referring to FIG. 2, the ultra-thin photoresist layer 16 of
`the semiconductorstructure 10 is then selectively exposed to
`actinic radiation (shown by the arrows) through a lithogra-
`phy mask 18. The ultra-thin photoresist layer 16 is selec-
`tively exposed using electromagnetic radiation having a
`relatively small wavelength (for example, less than 250 nm).
`In this embodiment, electromagnetic radiation having a
`wavelength of about 13 nm and or 11 nm is employed. Since
`relatively small wavelengths are used, reflectivity concerns
`are mini