Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 1 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 1 of 18
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`EXHIBIT 10
`EXHIBIT 10
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`case 6:20-ev-01216-ADA DocumentMHIFMAMHEN AEEUTTA
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 2 of 18
`US006162587A
`
`United States Patent 55
`[11] Patent Number:
`6,162,587
`Yang etal.
`[45] Date of Patent:
`Dec. 19, 2000
`
`
`Inventors: Chih Yuh Yang, San Jose; Christopher
`F. Lyons, Fremont; Harry J. Levinson,
`.
`.
`Saratoga; Khanh B. Nguyen, San
`Mateo; Fei Wang; Scott A. Bell, both=Primary Examiner—Mark F. Hutt
`of San Jose,all of Calif.
`Assistant Examiner—Saleha R. Mohamedulla
`Attorney, Agent, or Firm—Amin, Eschweiler & Turocy,
`LLP
`[57]
`
`[54] THIN RESIST WITH TRANSITION METAL
`HARD MASKFORVIA ETCH APPLICATION
`
`[75]
`
`[73] Assignee: Advanced Micro Devices, Sunnyvale,
`Calif.
`
`Dec. 1, 1998
`
`[21] Appl. No.: 09/203,450
`.
`Filed:
`[22]
`Go3C 5/00
`Int. C1.”
`[51]
`[52] US. Checence430/314:430/316: 430/317:
`ee ,
`” 430318
`:
`[58] Field of SNeSe3ad883aoa,1ear
`;
`;
`;
`;
`;
`39
`References Cited
`U.S. PATENT DOCUMENTS
`
`[56]
`
`7/1998 Jang et al. ccs cee 438/424
`5,786,262
`5,817,567 10/1998 Jang et al. oe eesesesseccneeeees 438/427
`11/1999 Chapman.....
`« 430/316
`5,976,769
`
`11/1999 Wuetal. ..
`-- 438/700
`5,985,766
`11/1999 Felter voce ceseseeteeeeee 430/270.1
`5,989,776
`
`ABSTRACT
`
`A method of forming a via structure is provided. In the
`method, a dielectric layer is formed on an anti-reflective
`coating (ARC) layer covering a first metal layer; and a
`transition metal layer is formed on the dielectric layer. An
`ultra-thin photoresist layer is formed on the transition metal
`layer, and the ultra-thin photoresist layer is patterned with
`short wavelength radiation to define a pattern for a via. The
`patterned ultra-thin photoresist
`layer is used as a mask
`during a first etch step to transfer the via pattern to the
`transition metal layer. The first etch step includes an etch
`chemistry that is selective to the transition metal layer over
`the ultra-thin photoresist layer and the dielectric layer. The
`transition metal layer is employed as a hard mask during a
`second etch step to form a contact hole corresponding to the
`via pattern by etching portions of the dielectric layer.
`
`4,299,911
`5,040,020
`5,534,312
`5,757,077
`
`11/1981 Ochi et al. eee 430/286
`
`8/1991 Rauschenbach et al.
`oe. 355/53
`
`7/1996 Hill et abe eee
`eeeeceeeeeeee 427/533
`5/1998 Chunget al.eee 257/736
`
`SN
`
`14 Claims, 9 Drawing Sheets
`
`190
`
`66
`
`62
`
`60
`
`

`

`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 3 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 3 of 18
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`U.S. Patent
`
`Sheet 1 of 9
`
`6,162,587
`
`Dec. 19, 2000
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`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 4 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 4 of 18
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`U.S. Patent
`
`Dec. 19, 2000
`
`Sheet 2 of 9
`
`6,162,587
`
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`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 5 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 5 of 18
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`U.S. Patent
`
`Sheet 3 of 9
`
`Dec. 19, 2000
`
`6,162,587
`
`

`

`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 6 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 6 of 18
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`U.S. Patent
`
`Dec. 19, 2000
`
`Sheet 4 of 9
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`6,162,587
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`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 7 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 7 of 18
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`U.S. Patent
`
`Dec. 19, 2000
`
`Sheet 5 of 9
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`6,162,587
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`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 8 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 8 of 18
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`U.S. Patent
`
`Dec. 19, 2000
`
`Sheet 6 of 9
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`6,162,587
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`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 9 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 9 of 18
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`U.S. Patent
`
`Dec. 19, 2000
`
`Sheet 7 of 9
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`6,162,587
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`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 10 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 10 of 18
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`U.S. Patent
`
`Dec. 19, 2000
`
`Sheet 8 of 9
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`6,162,587
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`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 11 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 11 of 18
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`U.S. Patent
`
`Dec. 19, 2000
`
`Sheet 9 of 9
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`6,162,587
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`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 12 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 12 of 18
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`6,162,587
`
`1
`THIN RESIST WITH TRANSITION METAL
`HARD MASKFOR VIA ETCH APPLICATION
`
`TECHNICAL FIELD
`
`invention generally relates to photo-
`The present
`lithography, and moreparticularly relates to a method of
`forming sub-micron vias using short wavelength radiation
`and ultra-thin photoresists.
`BACKGROUND OF THE INVENTION
`
`2
`(EUV) radiation and/or deep UV radiation in fabricating
`vias. As noted above, EUV and deep UV radiation are
`preferred radiation sources in lithographic processes where
`fine resolution is desired. The short wavelengths of these
`types of radiation afford for fine patterning (e.g., critical
`feature sizes <0.25 um). However, these types of radiation
`are highly absorbed by photoresist material which conse-
`quently limits the depth of penetration by the radiation into
`the photoresist material.
`By employing a transition metal layer to be patterned as
`a hard mask for use in connection with etching the vias, the
`In the semiconductor industry, there is a continuing trend
`present invention affords for expanding available etch chem-
`toward higher device densities. To achieve these high
`istries useable in EUV and/or deep UV lithographic pro-
`densities, there has been and continues to be efforts toward
`cesses. In particular, these types of lithographic processes
`scaling down the device dimensions (e.g., at submicron
`require the use of very thin photoresists as a result of the
`levels) on semiconductor wafers. In order to accomplish
`depth of penetration limitations of the short wavelength
`such high device packing density, smaller and smaller fea-
`radiation. Such very thin photoresists are limited in their
`ture sizes are required. This may include the width and
`capacity as etch barriers due to the thickness thereof.
`spacing of interconnecting lines, spacing and diameter of
`is
`In the present
`invention,
`the ultra-thin photoresist
`contact holes (vias), and the surface geometry such as
`employed in patterning and etching (e.g., with a high selec-
`corners and edges of various features.
`tivity fluorocarbon plasma) the transition metal layer there-
`The requirement of small features with close spacing
`under to form a hard mask. A via pattern formed in the
`between adjacent features requires high resolution photo-
`photoresist with the short wavelength radiation is transferred
`lithographic processes.
`In general,
`lithography refers to
`to the transition metal layer byafirst etch step. The patterned
`processes for pattern transfer between various media. It is a
`transition metal layer is used as a hard maskfor a subsequent
`second etch step to etch a dielectric layer so as to form
`technique used for integrated circuit fabrication in which a
`contact holes therein corresponding to the via pattern.
`siliconslice, the wafer, 1s coated uniformly with a radiation-
`Thereafter, standard via formation processes are performed
`sensitive film, the photoresist, and an exposing source (such
`to fill the contact holes, planarize the filler material, etc. to
`as optical light, x-rays, or an electron beam) illuminates
`form the via having a cross-section with a largest transverse
`selected areas of the surface through an intervening master
`dimension less than 0.25 wm. Thus, the present invention
`template, the mask, for a particular pattern. The photoresist
`affords for taking advantageofthe fine resolution patterning
`receives a projected image of the subject pattern. Once the
`available from EUV and deep UV lithographic processes
`imageis projected, it is indelibly formed in the photoresist.
`and mitigates the limitations associated therewith with
`The projected image may beeither a negative or a positive
`respect to etch chemistry.
`image of the subject pattern. Exposure of the photoresist
`One specific aspect of the present invention relates to a
`through a photomask causes the image area to becomeeither
`method of forminga via structure. In the method,a dielectric
`more or less soluble (depending on the coating) in a par-
`layer is formed on an anti-reflective coating (ARC) covering
`ticular solvent developer. The more soluble areas are
`a first metal layer. A transition metal layer is formed on the
`removed in the developing process to leave the pattern
`dielectric layer. An ultra-thin photoresist layer is formed on
`image in the photoresist as less soluble polymer.
`the transition metal layer, and the ultra-thin photoresist layer
`Projection lithography is a powerful and essential tool for
`is patterned with short wavelength radiation to define a
`microelectronics processing. As feature sizes are driven
`pattern for the via structure. The patterned ultra-thin pho-
`smaller and smaller, optical systems are approaching their
`toresist layer is used as a mask duringafirst etch step to
`limits caused by the wavelengths of the optical radiation. A
`transfer the via pattern to the transition metal layer. The first
`recognized way of reducing the feature size of circuit
`etch step includes an etch chemistry that is selective to the
`elements is to lithographically image the features with
`transition metal layer over the ultra-thin photoresist layer.
`radiation of a shorter wavelength. “Long” or “soft” x-rays
`Thetransition metal layer is employed as a hard mask during
`(a.k.a, extreme ultraviolet (EUV)), wavelength range of
`a second etch step to form a contact hole corresponding to
`lambda=50 to 700 Angstroms(A)are nowatthe forefront of
`the via pattern by etching portions of the dielectric layer.
`research in an effort to achieve the smaller desired feature
`sizes.
`Another aspect of the present invention relates to a via
`structure having a largest transverse dimension below about
`Although EUV lithography provides substantial advan-
`0.18 um. In forming the structure, In the method,a dielectric
`tages with respect to achieving high resolution patterning,
`layer is formed on an anti-reflective coating coveringafirst
`the shorter wavelength radiation is highly absorbed by the
`metal
`layer. A transition metal
`layer is formed on the
`photoresist material. Consequently, the penetration depth of
`dielectric layer. An ultra-thin photoresist layer is formed on
`the radiation into the photoresist is limited. The limited
`the transition metal layer. The ultra-thin photoresist layer is
`penetration depth of the shorter wavelength radiation
`patterned with short wavelength radiation to define a pattern
`requires the use of ultra-thin photoresists so that the radia-
`for the via structure. The ultra-thin photoresist layer is used
`tion can penetrate the entire depth of the photoresist in order
`as a mask duringafirst etch step to transfer the via pattern
`to effect patterning thereof. However, the thinness of such
`60
`to the transition metal layer, the first etch step including an
`ultra-thin photoresists results in the etch resistance thereof to
`etch chemistry that is selective to the transition metal layer
`be relatively low.
`In other words,
`the etch protection
`over the ultra-thin photoresist layer. The transition metal
`afforded by ultra-thin photoresists is limited which in turn
`layer is used as a hard mask during a second etch step to
`limits the EUV lithographic process.
`form a contact hole corresponding to the via pattern by
`SUMMARYOF THE INVENTION
`etching portions of the dielectric layer.
`Another aspect of the present
`invention relates to a
`method of forminga via structure. In the method,a dielectric
`
`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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`65
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`The present invention relates to a method to facilitate
`lithographic processes employing extreme ultra-violet
`
`

`

`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 13 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 13 of 18
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`6,162,587
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`30
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`3
`4
`FIG. 5 is a schematic cross-sectional illustration of a
`layer is formed on an anti-reflective coating coveringafirst
`metal
`layer. A transition metal
`layer is formed on the
`dielectric layer formed over the ARC layer of FIG. 4 in
`dielectric layer, the transition metal layer having a thickness
`accordance with one aspect of the present invention;
`FIG. 6 is a schematic cross-sectional illustration of a
`within the range of 50 A-2000 A. An ultra-thin photoresist
`layer is formed on the transition metal layer, the ultra-thin
`transition metal layer formed over the dielectric layer of
`photoresist layer having a thickness within the range of 50
`FIG. 5 in accordance with one aspect of the present inven-
`A-—2000 A. Theultra-thin photoresist layer is patterned with
`tion;
`FIG. 7 is a schematic cross-sectional illustration of an
`short wavelength radiation to define a pattern for the via
`structure, the short wavelength radiation falling within the
`ultra-thin photoresist layer formed over the transition metal
`range of about 11 nm to 13 nm. The ultra-thin photoresist
`layer of FIG. 6 in accordance with one aspect of the present
`layer is used as a mask duringa first etch step to transfer the
`invention;
`FIG. 8 is a schematic cross-sectional illustration of the
`via pattern to the transition metal layer, the first etch step
`including an etch chemistrythat is selective to the transition
`ultra-thin photoresist layer of FIG. 7 undergoing a patterning
`metal layer over the ultra-thin photoresist layer and the
`step in accordance with one aspect of the present invention;
`dielectric layer. The transition metal layer is used as a hard
`FIG. 9 is a schematic cross-sectional illustration of the
`mask during a second etch step to form a contact hole
`ultra-thin photoresist layer of FIG. 8 after the patterning step
`corresponding to the via pattern by etching portions of the
`is substantially complete in accordance with one aspect of
`dielectric layer.
`the present invention;
`Yet another aspect of the present invention relates to a
`FIG. 10 is a schematic cross-sectional illustration of the
`method of forming a multi-layered interconnect structure. In
`transition metal layer of FIG. 9 undergoing an etching step
`the method, a first dielectric layer is formed on an anti-
`in accordance with one aspect of the present invention;
`reflective coating covering a first metal layer. A transition
`FIG. 11 is a schematic cross-sectional illustration of the
`metal layer is formed on the dielectric layer, the transition
`transition metal layer of FIG. 10 after the etching step is
`metal
`layer having a thickness within the range of 50
`substantially complete in accordance with one aspect of the
`A-2000 A. An ultra-thin photoresist layer is formed on the
`present invention;
`transition metal layer, the ultra-thin photoresist layer having
`FIG. 12 is a schematic cross-sectional illustration of the
`a thickness within the range of 50 A-2000 A.Theultra-thin
`transition metal layer and dielectric layer of FIG. 11 under-
`photoresist layer is patterned with short wavelength radia-
`going an etching step in accordance with one aspect of the
`tion to define a pattern for a via,
`the short wavelength
`present invention;
`radiation falling within the range of about 11 nm to 13 nm.
`FIG. 13 is a schematic cross-sectional illustration of the
`The ultra-thin photoresist layer is used as a mask during a
`transition metal layer and dielectric layer of FIG. 12 after the
`first etch step to transfer the via pattern to the transition
`etching step is substantially complete to form a contact hole
`metal layer. The first etch step includes an etch chemistry
`in accordance with one aspect of the present invention;
`that
`is selective to the transition metal
`layer over the
`FIG. 14 is a schematic cross-sectional illustration of the
`ultra-thin photoresist layer. The transition metal layer is
`contact hole of FIG. 13 undergoingafilling (plugging) step
`35
`with a conductive material to form a via in accordance with
`employed as a hard mask during a second etch step to form
`a contact hole corresponding to the via pattern by etching
`one aspect of the present invention;
`FIG. 15 is a schematic cross-sectional illustration of a via
`portionsof the dielectric layer. The contacthole is filled with
`a conductive material so as to form the via. The hard mask
`after the filling step of FIG. 14 is substantially complete in
`is removed and the conductive material planarized via CMP.
`accordance with one aspect of the present invention;
`FIG. 16 is a schematic cross-sectional illustration of the
`A second metal layer is formed over the via, and a second
`dielectric layer is formed over the second metal layer.
`conductive material of FIG. 15 undergoing a planarization
`To the accomplishmentof the foregoing and related ends,
`process in accordance with one aspect of the present inven-
`tion;
`the invention, then, comprises the features hereinafter fully
`FIG. 17 is a schematic cross-sectional illustration of the
`described and particularly pointed out in the claims. The
`following description and the annexed drawingsset forth in
`via substantially complete in accordance with one aspect of
`detail certain illustrative embodiments of the invention.
`the present invention;
`FIG. 18 is a schematic cross-sectional illustration of a
`These embodimentsare indicative, however, of but a few of
`second metal layer being formed over the via structure in
`the various ways in which the principles of the invention
`accordance with one aspect of the present invention;
`may be employed. Other objects, advantages and novel
`FIG. 19 is a schematic cross-sectional illustration of the
`features of the invention will become apparent from the
`following detailed description of the invention when con-
`second metal layer formed in substantial part in accordance
`sidered in conjunction with the drawings.
`with one aspect of the present invention;
`illustration of
`FIG. 20 is a schematic cross-sectional
`BRIEF DESCRIPTION OF THE DRAWINGS
`second dielectric layer being formed over the second metal
`layer in accordance with one aspect of the present invention;
`FIG. 21 is a schematic cross-sectional illustration of the
`second dielectric layer formed in substantial part so as to
`form a multi-layered interconnect structure in accordance
`with one aspect of the present invention; and
`FIG. 22 is a perspective illustration of the multi-layered
`interconnect structure of FIG. 21 in accordance with one
`aspect of the present invention.
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`40
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`45
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`50
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`60
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`65
`
`FIG. 1 is a prior art schematic cross-sectional illustration
`of a conventional patterned resist used in the formation of
`vias;
`FIG. 2 is a perspective illustration of a multi-layered
`interconnectstructure employing vias formed in accordance
`with one aspect of the present invention;
`FIGS. 3a—3e illustrate representative filled via structures
`which may be formed in accordance with the present inven-
`tion
`FIG. 4 is a schematic cross-sectional illustration of a
`metal layer having an anti-reflective coating (ARC) formed
`thereon in accordance with one aspect of the present inven-
`tion;
`
`The present invention will now be described with refer-
`ence to the drawings, wherein like reference numerals are
`
`

`

`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 14 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 14 of 18
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`6,162,587
`
`5
`usedto refer to like elements throughout. The method of the
`present invention will be described with reference to the
`formation of vias using a photolithographic process employ-
`ing radiation of short wavelength (e.g., EUV radiation
`and/or deep UVradiation) and an ultra-thin photoresist. The
`following detailed description is of the best modes presently
`contemplated by the inventors for practicing the invention.
`It should be understood that the description of these pre-
`ferred embodiments are merely illustrative and that they
`should not be taken in a limiting sense.
`FIG. 1 is a cross-sectional illustration of a conventional
`photoresist layer 20 being used in the formationof via(s). As
`shown, the photoresist layer 20 is substantially thick (e.g.,
`5,000-10,000 A). The photoresist layer 20 is shown pat-
`terned so as to define a via which will be etched into an
`
`underlying dielectric layer 22 so as to form a contact hole to
`an underlying anti-reflective coating layer 24 and a metal
`layer 26 However, the thickness of the photoresist layer 20
`is not conducive for use with short wavelength radiation
`because these types of radiation would be highly absorbed
`by the photoresist layer 20 and not penetrate the entire
`thickness “t” of the layer 20. As a result, such a conventional
`scheme for forming a via would not be able to take advan-
`tage of the improved resolution of patterning offered by the
`short wavelength radiation.
`Turning now to the present invention in detail, FIG. 2
`illustrates an interconnect structure 30 having vias 32
`formed in accordance with the present invention. The vias
`32 are filled with a suitable material (e.g., tungsten, copper)
`to form plugs which provide conductive pathways through
`an insulating dielectric medium 40 to connect interconnects
`of different conductor layers 50, 52. Although, the present
`invention is described with respect to forming only two
`conductive layers 50, 52 for ease of understanding,it is to be
`appreciated that many more conductive layers (selectively
`electrically isolated with the dielectric material 40) may be
`formed, and suchstructures are intended to fall within the
`scope of the hereto appended claims.
`The vias 32 are formed employing photolithographic
`techniques utilizing short wavelength radiation and ultra-
`thin photoresists. Accordingly, substantially smaller dimen-
`sions of the vias 32 are achieved as compared to vias formed
`in accordance with the prior art technique discussed with
`respect
`to FIG. 1. For example,
`the vias 32 may have
`respectively a critical feature dimension of less than about
`0.25 um, and such small dimension is not typically obtain-
`able using conventional lithographic processes. In another
`embodiment, the vias may have respectively a critical fea-
`ture dimension of less than about 0.18 um.
`FIGS. 3a—3e illustrate representative filled via structures
`which may be formed in accordance with the present inven-
`tion. FIG. 3a depicts a via structure 32, which is substan-
`tially cylindrical and has a substantially circular cross-
`section 34,. A diameter “d,” of the cross-section 34a in one
`particular embodimentis less than about 0.25 um. In another
`embodiment, the d, is less than about 0.18 um.
`FIG. 35 depicts a via structure 32, which is substantially
`cylindrical and has a substantially elliptical cross-section
`34,. A length dimension for a major axis “d,” of the
`cross-section 34, in one particular embodimentis less than
`about 0.25 um. In another embodiment, the d, is less than
`about 0.18 um.
`FIG. 3¢ depicts a via structure 32c which is substantially
`cylindrical and has a substantially square cross-section 34,.
`A diagonal length dimension “d.” of the cross-section 34, in
`one particular embodimentis less than about 0.25 wm. In
`another embodiment, the d, is less than about 0.18 um.
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`15
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`20
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`25
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`30
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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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`6
`FIG. 3d depicts a via structure 32d which is substantially
`cylindrical and has a substantially rectangular cross-section
`34,. A diagonal length dimension “d,” of the cross-section
`34d in one particular embodimentis less than about 0.25 um.
`In another embodiment, the d, is less than about 0.18 um.
`FIG. 3e depicts a via structure 32, which is substantially
`cylindrical and has a substantially irregular shaped cross-
`section 34,. A largest
`transverse dimension “d,” of the
`cross-section 34, in one particular embodimentis less than
`about 0.25 um. In another embodiment, the d, is less than
`about 0.18 um.
`The various aforementioned dimensions (d,, d,, d., dy,
`and d,) will be referred to as the largest
`transverse
`dimensions, which are respectively the maximum length
`dimension of a transverse cross-section of the via 32 with
`
`respect to a y-axis as shown in FIGS. 3a-3e.
`Turning now to FIGS. 421, the fabrication of the vias 32
`is discussed in greater detail. FIG. 4 is a cross-sectional
`illustration of a first metal layer 60, which is part of the
`conductive layer 50 and a graded anti-reflective coating
`(ARC) 62 formed thereon. Although not shown,it is to be
`appreciated that the first metal layer 60 may be formed over
`a substrate, for example. The first metal
`layer 60 may
`comprise any suitable conductive material employable for
`forming conductive patterns in the semiconductor industry.
`Preferably,
`the conductive material
`includes a member
`selected from the group consisting of refractory materials,
`such as titanium and titanium alloys, tungsten and tungsten
`alloys, aluminum and aluminum alloys, copper and copper
`alloys and polycrystalline silicon. The ARC 62 is left over
`from a previous patterning of the first metal layer 60 (e.g.,
`to pattern metal lines). The ARC 62 preferably comprises
`titanium nitride (TiN), however, any like material may be
`employed. The ARC 62 serves as an etch stop layer for a
`dielectric etch step discussed in greater detail below. The
`ARC 62 is conductive and thus if remaining after the
`dielectric etch, the ARC 62 will not inhibit an electrically
`conductive connection between the first metal layer 60 and
`the via 32 which mayserve as an electrically conductive link
`to another metal layer or element(e.g., conductive line).
`Furthermore, the ARC 62 serves as an etch stop region
`during the dielectric etch to provide for a margin of error in
`the dielectric etch so as to mitigate damageto the first metal
`layer 60 by the dielectric etch. The thickness of the ARC
`layer 62 is preferably within the range of 300 A-1500 A,
`however, any thickness suitable for carrying out the afore-
`mentioned functions of the ARC 62 may be employed.
`FIG. 5 illustrates a dielectric layer 66 formed over the
`ARClayer 62. The dielectric layer 66 is part of the dielectric
`40. The dielectric layer provides for insulating conductive
`elements (e.g., adjacent metal lines) from each other so as to
`mitigate electrical shorting and/or capacitive crosstalk there
`between. Preferably, the dielectric layer 66 includestetra-
`ethyorthosilicate (TEOS). However, and suitable insulating
`material (e.g., phosphosilicate glass (PSG), borophospho-
`silicate glass (BPSG), any suitable spin-on glass (SOG), or
`polyimides having a suitably low dielectric constant) may be
`employed. The dielectric layer 66 may be deposited by any
`suitable process (e.g., Low Pressure Chemical Vapor Depo-
`sition (LPCVD), Plasma Enhanced Chemical Vapor Depo-
`sition (PECVD), or High Density Plasma Chemical Vapor
`Deposition (HDPCVD)) to a desired thickness.
`Next, as shown in FIG. 6, a transition metal layer 70 is
`formed over the dielectric layer 66. The transition metal
`layer 70 will serve as a hard mask during etching of the
`underlying dielectric layer 66. The transition metal layer 70
`
`

`

`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 15 of 18
`Case 6:20-cv-01216-ADA Document 41-10 Filed 10/06/21 Page 15 of 18
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`6,162,587
`
`8
`Kodak, Hoechst Celanese Corporation, Brewer and IBM.
`The scope of the present invention as defined by the hereto
`appended claims is intended to include any ultra-thin pho-
`toresist suitable for carrying out the present invention.
`Referring to FIG. 8, the ultra-thin photoresist layer 80
`then undergoes an exposure/developmentstep 90 to provide
`a patterned photoresist 100 (FIG. 9). The patterned photo-
`resist 100 is formed using electromagnetic radiation having
`a relatively small wavelength (for example, less than 200
`nom). In this embodiment, electromagnetic radiation having
`a wavelength of about 13 nm is employed. Since relatively
`small wavelengths are used, reflectivity concerns are mini-
`mized because larger wavelengths are more frequently asso-
`ciated with reflectivity problems. The ultra-thin photoresist
`layer 80 is selectively exposed to radiation; that is, selected
`portions of the ultra-thin photoresist layer 80 are exposed to
`radiation. Either the exposed or unexposed portions of the
`ultra-thin photoresist layer 80 are removed or developed to
`provide the patterned photoresist 100.
`Thecritical feature dimension “d” of the exposed portion
`of the transition metal layer 70 (opening 102 in the patterned
`photoresist 100) is about 0.25 um orless, including about
`0.18 um orless, about 0.09 um or less, about 0.075 um or
`less and about 0.05 zum or less, depending on the wavelength
`of the radiation used.
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`7
`may comprise any one or more of Ti, Ta, W, TiN, TaN, and
`WN,for example. Any suitable technique for forming the
`transition metal layer 70 may be employed such as LPCVD,
`PECVD, HDCVD, sputtering or high density plasma chemi-
`cal vapor deposition (HDPCVD)techniques to a thickness
`suitable for serving as a hard maskfor a selective etch of the
`dielectric layer 66. Thus, for example, in one aspect of the
`present invention the thickness of the transition metal layer
`70 is between the range of about 50 A-10,000 A.In another
`aspect,
`the thickness of the transition metal
`layer 70 is
`between the range of about 50 A-5000 A.In another aspect,
`the thickness ofthe transition metal layer 70 is between the
`range of about 50 A-3000 A.In another aspect, the thickness
`of the transition metal layer 70 is betweenthe range of about
`50 A-2000 A.
`In another aspect,
`the thickness of the
`transition metal layer 70 is between the range of about 50
`A-1500 A. In another aspect, the thickness of thetransition
`metal layer 70 is between the range of about 50 A-1000 A.
`In still another aspect, the thickness of the transition metal
`layer 70 is between the range of about 50 A-500 A.
`FIG. 7 illustrates an ultra-thin photoresist layer 80 formed
`over the transition metal layer 70. The ultra-thinphotoresist
`layer 80 has a thickness of about 500 A-5000 A, however,
`it is to be appreciated that the thickness thereof may be of
`any dimension suitable for carrying out the present inven-
`The selectively exposed ultra-thin photoresist layer 80 is
`tion. Accordingly, the thickness of the ultra-thin photoresist
`developed by contact with a suitable developer that removes
`80 can vary in correspondence with the wavelength of
`either the exposed or unexposed portions of the ultra-thin
`radiation used to pattern the ultra-thin photoresist 80. One
`photoresist layer 80. The identity of the developer depends
`aspect of the present invention provides for forming the
`ultra-thin photoresist layer 80 to have a thickness within the
`upon the specific chemical constitution of the ultra-thin
`photoresist
`layer 80. For example, an aqueous alkaline
`range of 1000 A to 4000 A. Another aspect of the present
`invention provides for forming the ultra-thin photoresist
`solution may be employed to remove unexposed portions of
`the ultra-thin photoresist layer 80. Alternatively, one or more
`layer 80 to have a thickness within the range of 2000 A to
`of dilute aqueousacid solutions, hydroxide solutions, water,
`3000 A. Yet another aspect of the present invention provides
`for forming the ultra-thin photoresist layer 80 to have a
`and organic solvent solutions may be employed to remove
`selected portions of the ultra-thin photoresist layer 80. The
`thickness within the range of 500 A to 2000 A. Theultra-thin
`developer is selected so that it does not degrade or etch the
`photoresist 80 may be formed overthe transition metal layer
`material of the transition metal layer 70, or at least degrades
`70 via conventional spin-coating or spin casting deposition
`or etches the material of the transition metal layer 70 at a
`techniques.
`subst