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`Case 2:20-cv-00048—JRG Document 1—6 Filed 02/21/20 Page 1 of 12 PageID #: 169


`Case 2:20-cv-00048-JRG Document 1-6 Filed 02/21/20 Page 2 of 12 PageID #: 170
`(12) United States Patent
`Gibson, Jr. et al.
`(10) Patent No.:
`US 6,879,046 B2
`(45) Date of Patent:
`Apr. 12, 2005
`(*) Notice:
`(51) Int. Cl." ......................... H01L23/48; H01L 23/52;
`HO1L 59/40
`(52) U.S. Cl. ....................... 257/760; 257/750; 257/751;
`257/752; 257/758; 438/760; 174/258; 174/256;
`428/428; 428/446; 428/447; 428/448
`(58) Field of Search ................................. 257/750-760,
`257/762; 438/760; 174/258, 256; 428/428,
`446, 447, 448, 209, 210,901
`References Cited
`5,456,762 A * 10/1995 Kariya et al. ............... 136/258
`5,494,859 A 2/1996 Kapoor
`6,037,664 A 3/2000 Zhao et al.
`6,037,668 A
`3/2000 Cave et al. ................. 257/784
`6,071,809 A
`6/2000 Zhao .......................... 438/634
`6,083,822 A
`7/2000 Lee.........
`... 438/624
`A E R. O. E.
`OOl el all. . . . . . . . . . . . . . . . .
`2-a-s/ - 2
`6,191,028 B1
`2/2001 Huang et al.
`(75) Inventors: Gerald W Gibson, Jr., Orlando, FL
`(US); Scott Jessen, Orlando, FL (US);
`6,265,321 B1
`7/2001 Chooi et al. ................ 438/725
`Steven Alan Lytle, Orlando, FL (US);
`Kurt George Steiner, Orlando, FL
`(US); Susan Clay Vitkavage, Orlando,
`FL (US)
`2341484. A 9/1998 ......... HO1 L/21/285
`2365215 A 2/2002 ........... HO1 L/21/02
`(73) Assignee: Agere Systems Inc., Allentown, PA
`2367426 A
`4/2002 ......... HO1 L/23/532
`2001085523 A * 3/2001
`Subject to any disclaimer, the term of this
`past is Sh used " U.S. Appl. No. 10,038,352, filed Jan. 2, 2002.
`Primary Examiner-George Eckert
`(21) Appl. No.: 10/038,371
`ASSistant Examiner-Chris C. Chu
`(22) Filed:
`Jan. 2, 2002
`Prior Publication Data
`A Split barrier layer enables copper interconnect wires to be
`US 2003/0003765 A1 Jan. 2, 2003
`it." y dielectric is S. R.S.
`Ing line dIIIuSIon OI N-1 base groups into pnotores.ISIS
`Related U.S. Application Data
`where they can render the photoresist insoluble. The split
`(60) Provisional application No. 60/301.295, filed on Jun. 28,
`barrier layer is disposed between the copper and the low-k
`dielectric and includes a nitrogen-containing, oxygen-free
`film which contacts the copper, and an oxygen-containing,
`nitrogen-free film which contacts the low-k dielectric film.
`The nitrogen-containing film prevents the formation of
`undesirable copper oxides, and the oxygen-containing film
`prevents the diffusion of N-H base groups into the low-k
`dielectric films. The oxygen-containing film may be an
`oxygen-doped Silicon carbide film in an exemplary embodi
`ment. In another embodiment, a film Stack of low-k dielec
`tric films includes an etch-Stop layer and hardmask each
`formed of oxygen-doped Silicon carbide. The hardmask and
`etch-Stop layer enable the formation of a dual-damascene
`opening in the film Stack, and the film Structure of the
`present invention precludes N-H base groups from diffus
`ing from the low-k dielectric films and neutralizing acid
`catalysts in the photoresist used to define the dual dama
`Scene opening.
`13 Claims, 4 Drawing Sheets
`A -/-
`5 65 3
`1 1


`Case 2:20-cv-00048-JRG Document 1-6 Filed 02/21/20 Page 3 of 12 PageID #: 171
`US 6,879,046 B2
`Page 2
`6,297,162 B1 * 10/2001 Jang et al. .................. 438/706
`6,323,121 B1 11/2001 Liu et al.
`6,340,435 B1 * 1/2002 Bjorkman et al. ............ 216/72
`7/2002 Kudo
`6,420.261 B2
`9/2003 Passemard .................. 438/584
`6,624,053 B2
`6,632,478 B2 * 10/2003 Gaillard et al. ........ 427/255.37
`* cited by examiner


`Case 2:20-cv-00048-JRG Document 1-6 Filed 02/21/20 Page 4 of 12 PageID #: 172
`U.S. Patent
`Apr. 12, 2005
`Sheet 1 of 4
`US 6,879,046 B2
`2 - 2
`1 1
`3 1
`) \ \ \ \ 1z\ \
`2 22


`Case 2:20-cv-00048-JRG Document 1-6 Filed 02/21/20 Page 5 of 12 PageID #: 173
`U.S. Patent
`Apr. 12, 2005
`Sheet 2 of 4
`US 6,879,046 B2
`FIG. 3
`35 25 J3 5 15 13 11 23 J
`S/ 27 | |
`| | | |
`FIG. 4
`23 2547 43 33 35
`5 15 49 47 3.
`1 1


`Case 2:20-cv-00048-JRG Document 1-6 Filed 02/21/20 Page 6 of 12 PageID #: 174
`U.S. Patent
`Apr. 12, 2005
`Sheet 3 of 4
`US 6,879,046 B2
`5 J
`1 1
`FIC. 6
`151 Ns
`125 N, 127
`1 1 7
`1 O5
`1 O3 1 1 1


`Case 2:20-cv-00048-JRG Document 1-6 Filed 02/21/20 Page 7 of 12 PageID #: 175
`U.S. Patent
`Apr. 12, 2005
`Sheet 4 of 4
`US 6,879,046 B2


`Case 2:20-cv-00048-JRG Document 1-6 Filed 02/21/20 Page 8 of 12 PageID #: 176
`US 6,879,046 B2
`This application claims priority of U.S. provisional appli
`cation Ser. No. 60/301.295, entitled Full Via First Integra
`tion Method of Manufacture, and filed on Jun. 28, 2001, the
`contents of which are herein incorporated by reference.
`The present invention relates most generally to Semicon
`ductor devices and methods for manufacturing the same.
`More particularly, the present invention provides a method
`and structure for preventing base groups from becoming
`nested in a low-k dielectric material and Subsequently ren
`dering photoresists insoluble.
`Deep ultra-violet (DUV) lithography is widely used in the
`fabrication of advanced VLSI (Very Large Scale Integration)
`semiconductor devices. Chemically amplified DUV photo
`resists improve the performance of the lithography Systems
`and improve device feature resolution. Low dielectric con
`Stant (low-k) dielectrics are favored in today's Semiconduc
`tor manufacturing industry because of the performance
`improvements they provide by way of reducing parasitic
`capacitance, reducing propagation delay and therefore
`increasing device Speed. The use of copper interconnect
`features is also favored to reduce line resistance of the
`interconnect lines. Typical copper interconnect Schemes
`incorporate damascene manufacturing techniques to define
`the interconnect paths. A dual damascene approach is
`favored because it provides lower cost processing, improved
`level-to-level alignment tolerance and thus allows for tighter
`design rules and improved performance.
`A Shortcoming associated with the use of low-k dielectrics
`in conjunction with copper interconnect lines and chemi
`cally amplified photoresists used in DUV lithography, is that
`base groups which become nested in porous low-k dielectric
`materials, can interact with the acid catalysts included in
`chemically amplified photoresists to render the exposed
`photoresist insoluble in developer. This insoluble photoresist
`distorts the pattern being formed and is difficult to remove.
`The distorted pattern may result in electrical opens because
`via and contact openings cannot be formed. Base groups
`Such as amines and other N-H base groups, are typically
`produced in association with conventional hardmask films,
`etch-Stop layerS and barrier films used in the film Stack that
`also includes low-k dielectric films, and which is advanta
`geously used in dual damascene processing. Etch-Stop films
`and barrier films are commonly nitrogen-containing films,
`and amine or other N-H base groups may be produced
`during the formation of Such films.
`The use of copper as an interconnect material requires the
`use of a barrier layer which typically includes nitrogen and
`is free of oxygen. The presence of oxygen in an adjoining
`film or during the formation of an adjacent film, undesirably
`causes the formation of copper oxides by reaction with
`copper. Copper oxides undesirably degrade adhesion which
`could lead to mechanical failure. Moreover, after copper
`interconnect lines are formed using damascene technology,
`for example, organic corrosion inhibitors are typically
`formed over the copper Surface. The organic corrosion
`inhibitors prevent the formation of copper oxides and pre
`vent corrosion from occurring while the Substrate including
`the exposed copper film, is transferred from a polishing tool,
`for example, to a film deposition tool used to form films over
`the copper Surface. A plasma chemistry including ammonia,
`NH, is typically used to clean or treat the copper Surface,
`remove any copper oxides which may form, and to remove
`the organic corrosion inhibitor. This ammonia-containing
`chemistry also produces amines or other N-H base groups
`which can diffuse into the porous low-k dielectric material
`and then into the photoresists.
`It is therefore desirable to enjoy the benefits provided by
`copper interconnect lines, low-k dielectric films and chemi
`cally amplified photoresists in DUV lithography Systems,
`without degrading the chemically amplified photoresist by
`interaction with base groups from the porous low-k dielec
`tric film.
`The present invention provides a method and structure for
`isolating a copper Surface and a nitrogen-containing barrier
`layer film, from a low-k dielectric material. An oxygen
`containing, Substantially nitrogen-free film is formed
`between the nitrogen-containing barrier layer film and the
`low-k dielectric material. The nitrogen-containing, Substan
`tially oxygen-free film and oxygen-containing, Substantially
`nitrogen-free film combine to form a composite barrier layer.
`In another exemplary embodiment, the composite barrier
`layer is used to isolate a conductive material which is readily
`oxidizable and Subject to corrosion, from a low-k dielectric
`According to another exemplary embodiment, the present
`invention provides a film Stack including low-k dielectric
`films, a hardmask film formed over the low-k dielectric
`films, and an etch-Stop layer formed between low-k dielec
`tric films. Each of the hardmask film and the etch-stop layer
`are formed of oxygen-doped Silicon carbide, SiC-O. A
`dual-damascene opening may be formed in the film Stack to
`include a wider upper portion that extends through the
`hardmask and upper low-k dielectric layer, and a narrower
`lower portion extending through the lower low-k dielectric
`According to another exemplary embodiment, the film
`Stack may be formed over an oxygen-doped, Substantially
`nitrogen-free barrier layer formed over a nitrogen containing
`barrier layer formed, in turn, over a copper-containing
`According to another exemplary embodiment, the present
`invention provides a proceSS for forming a Semiconductor
`product. The process includes treating a Surface with an
`ammonia-containing chemistry, forming a first barrier layer
`over the Surface and a Second barrier layer over the first
`barrier layer, and forming a low-k dielectric film over the
`Second barrier layer. The first barrier layer includes nitrogen
`and is Substantially free of oxygen, and the Second barrier
`layer includes oxygen and is Substantially free of nitrogen.
`According to another exemplary embodiment, the present
`invention provides a further process for forming a Semicon
`ductor product. The proceSS includes providing a copper
`Surface, forming a first barrier layer over the copper Surface,
`forming a Second barrier layer of oxygen-doped Silicon
`carbide over the first barrier layer, and forming a porous
`low-k dielectric film over the second barrier layer. The first
`barrier layer includes nitrogen and is Substantially free of
`The invention is best understood from the following
`detailed description when read in conjunction with the


`Case 2:20-cv-00048-JRG Document 1-6 Filed 02/21/20 Page 9 of 12 PageID #: 177
`US 6,879,046 B2
`accompanying drawing. It is emphasized that, according to
`common practice, the various features of the drawing are not
`to scale. On the contrary, the dimensions of the various
`features are arbitrarily expanded or reduced for clarity. Like
`numerals denote like features throughout the Specification
`and drawing. Included in the drawing are the following
`FIG. 1 is a cross-sectional view showing exemplary
`copper interconnect wires formed using damascene tech
`FIG. 2 is a cross-sectional view showing an exemplary
`composite barrier layer structure formed over a conductive
`material, and a low-k dielectric film formed over the com
`posite barrier layer;
`FIG. 3 is a cross-sectional view showing an exemplary
`etch-stop layer, upper low-k dielectric film and hardmask
`formed over the structure shown in FIG. 2;
`FIG. 4 is a cross-sectional view showing an opening
`formed in the structure shown in FIG.3 and a photosensitive
`film formed over the structure and within the opening;
`FIG. 5 shows the structure shown in FIG. 4 after portions
`of the photosensitive material have been exposed;
`FIG. 6 is a cross-sectional view showing insoluble pho
`toresist in a via opening according to the PRIOR ART, and
`FIG. 7 is a cross-sectional view showing a dual
`damascene opening formed in the structure shown in FIG. 5.
`The present invention provides a split barrier layer includ
`ing a layer of a nitrogen-containing material Such as
`nitrogen-doped silicon carbide or silicon nitride, and a layer
`of an oxygen-containing film. The split barrier layer is
`advantageously formed between a conductive film, and a
`low-k dielectric material. The conductive film may be
`readily oxidizable and Susceptible to corrosion. In one
`exemplary embodiment, the split barrier layer is formed
`between a copper-containing Surface and a low-k dielectric
`film. The layer which includes nitrogen is Substantially free
`of oxygen and forms a boundary with the conductive film
`such as copper and prevents copper oxidation in an exem
`plary embodiment. The oxygen-containing film is Substan
`tially free of nitrogen and is preferably formed of oxygen
`doped silicon carbide in an exemplary embodiment. It forms
`a boundary with the low-k dielectric material and prevents
`amines and other N-H base groups such as amino-silanes,
`from diffusing into the low-k dielectric material. The amine
`or other N-H base groups may be contained within the
`nitrogen-containing portion of the split barrier layer. The
`amine or other N-H base materials may additionally or
`alternatively be produced during the formation process
`which is used to form the nitrogen-containing barrier layer
`film. Typical deposition chemistries used to form the
`nitrogen-containing film include or produce ammonia, NH,
`which readily diffuses into and throughout low-k dielectric
`material. Ammonia, various amines and other N-H base
`groups may be used in the film formation chemistry and/or
`may be by-products and may diffuse into and throughout the
`porous low-k dielectric film if not suppressed by the pres
`ence of the oxygen-containing film of the split barrier layer.
`A film stack of an exemplary embodiment of the present
`invention includes a low-k dielectric film or films formed
`over the split barrier layer, and the film Stack may further
`include at least one etch-stop layer and hardmask film, each
`preferably formed of oxygen-doped silicon carbide, SiC
`O. These SiC-O films are formed using a process that
`preferably does not utilize or generate chemistries which
`include N-H base groups. Other oxygen-containing films
`which are substantially free of nitrogen and do not generate
`amines or other N-H base groups during their formation
`may be used in other exemplary embodiments. An advan
`tage of the present invention is the hardmask film, etch-Stop
`layer, and oxygen-containing portion of the split barrier
`layer film which preclude amine or other N-H base groups
`from diffusing into the low-k dielectric materials and then
`diffusing into the photoresist, rendering the photoresist
`insoluble. According to the embodiment in which cooper is
`used as the conductive interconnect material, the present
`invention also retains the advantageous aspect of performing
`an ammonia plasma copper oxide reduction operation and
`organic clean on the copper Surface, without having ammo
`nia or other basic by-products of the ammonia plasma
`chemistry becoming nested within the low-k dielectric films.
`FIG. 1 is a cross-sectional view showing an exemplary
`sub-structure of the present invention. Conductive lines 5
`are formed with an insulating material 7. Conductive lines 5
`may be formed of copper in the exemplary embodiment, but
`other suitable conductive materials may be used according
`to other exemplary embodiments. Insulating material 7 may
`be a low-k dielectric or other dielectric or insulating mate
`rial. In the exemplary embodiment, conductive lines 5 and
`insulating material 7 include a common, planar upper Sur
`face including upper surface 3 of conductive line 5. The
`structure may be formed using damascene techniques and
`using chemical mechanical polishing.
`Low-k dielectric films are characterized by a dielectric
`constant being less than the dielectric constant of Silicon
`dioxide, which is typically about 3.9–4.1. In an exemplary
`embodiment, the low-k dielectric may have a dielectric
`constant that is less than 3.5. Low-k dielectric materials are
`favored because dielectric constant is directly proportional
`to capacitance and propagation delay, and therefore
`inversely proportional to circuit speed. Methods for reduc
`ing the dielectric constant of a Silicon dioxide film include
`doping with fluorine, doping with carbon, and incorporating
`porosity, since vacuum has a dielectric constant of about 1.0.
`As such, a porous low-k dielectric material is favored. In an
`exemplary embodiment, the low-k dielectric film may be an
`organo-silicate-glass (OSG). According to another exem
`plary embodiment, the low-k dielectric material may be a
`porous low-k dielectric such as SiOC-H, such as deposited
`from tetra-methyl-cyclo-tetra-siloxane, oxygen, and carbon
`dioxide using a PECVD process. According to another
`exemplary embodiment, the low-k dielectric may be a
`spin-on aromatic carbon with porogen, that is Subsequently
`baked to create pores. According to other exemplary
`embodiments, commercially-available OSG materials Such
`as Black Diamond (Applied Materials Corporation), Coral
`(Novellus), FlowFill (Trikon), and Eagel2 (ASM) may be
`used. Such low-k dielectric materials are intended to be
`exemplary only, and other low-k dielectric materials may be
`used according to other exemplary embodiments. The low-k
`dielectric material may be formed using PECVD (plasma
`enhanced chemical vapor deposition) or spin-on techniques,
`but other methods of formation may be used in other
`exemplary embodiments.
`Returning to FIG. 1, after the exemplary structure shown
`in FIG. 1 has been formed, such as by chemical mechanical
`polishing, and includes copper as conductive wires 5 in the
`exemplary embodiment, upper Surface 3 may be coated with
`an organic corrosion inhibitor to inhibit corrosion which
`may otherwise result when substrate 1 is removed from the


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`US 6,879,046 B2
`polishing or CMP (chemical mechanical polishing) system.
`According to other exemplary embodiments, other conduc
`tive material Such as metals which may be readily oxidizable
`and/or Susceptible to corrosion, may be used and coated with
`a corrosion inhibitor. The coated, upper Surface 3 is then
`treated using an ammonia plasma. The ammonia plasma is
`used to clean Surface 3 and remove the organic corrosion
`inhibitor and any other organic residuals, as well as any
`oxides Such as copper oxide, which may have formed. After
`upper surface 3 is so treated, the substructure shown in FIG.
`1 is ready to have a film stack formed thereover.
`The film stack that is to be formed over the Substructure
`includes at least one low-k dielectric film and additional
`films Such as etch-Stop layers, barrier layers, and a hardmask
`which aid in the formation of a dual-damascene opening
`formed within the film Structure. The dual-damascene open
`ing may be used to provide contact to a Subjacent conductive
`wire or wires, Such as conductive wire 5.
`FIG. 2 shows exemplary composite barrier layer 9 and
`low-k dielectric film 17 formed over upper surface 3. In the
`exemplary embodiment shown in FIG. 2, upper Surface 3 is
`the upper surface of a conductive wire 5 which may be
`copper in an exemplary embodiment. Other Suitable con
`ductive materials may be used alternatively. Lower barrier
`layer 11 includes top Surface 12 and may be Silicon nitride
`or nitrogen-doped Silicon carbide, according to the exem
`plary embodiments. According to one exemplary
`embodiment, lower barrier layer 11 may be nitrogen-doped
`silicon carbide formed using a PECVD process which
`includes tetra-methyl-Silane, Silane, ammonia, and nitrogen
`in the plasma chemistry. According to another exemplary
`embodiment in which barrier layer 11 is a silicon nitride
`film, a PECVD process utilizing silane, ammonia and N
`may be used. Other techniques for forming lower barrier
`layer film 11 may be used alternatively. A fundamental
`concept of the present invention is that lower barrier layer 11
`is a nitrogen-containing film and is Substantially free of
`oxygen. This Suppresses the undesirable oxidation of the
`conductive material that forms conductive wire 5. Upper
`barrier layer film 13 includes top surface 15 and is advan
`tageously formed of oxygen-doped Silicon carbide, but
`Silicon dioxide or other oxygen-containing films that are
`substantially free of nitrogen and which preferably do not
`generate amines or other N-H base groups in their forma
`tion processes, may be used in other exemplary embodi
`ments. A PECVD process which includes tetra-methyl
`Silane and carbon dioxide in the plasma chemistry may be
`used to form oxygen-doped Silicon carbide upper barrier
`layer film 13, in an exemplary embodiment. Generally
`Speaking, upper barrier layer film 13 is an oxygen
`containing, Substantially nitrogen-free film.
`Lower low-k dielectric film 17 includes top surface 19
`and is as described above. Thickness 21 of lower low-k
`dielectric film 17 will vary according to application and may
`range from 1000 to 10000 angstroms in various exemplary
`embodiments. Other thicknesses may be used in other exem
`plary embodiments. In an exemplary embodiment, lower
`low-k dielectric film 17 may be a SiOC -H film deposited
`using a PECVD process and using tetra-methyl-cyclo-tetra
`Siloxane, oxygen, and carbon dioxide in the plasma chem
`Now turning to FIG. 3, etch-stop layer 23 is formed over
`top surface 19 of lower low-k dielectric film 17. Etch-stop
`layer 23 may be formed of oxygen-doped Silicon carbide or
`other oxygen-containing, nitrogen-free films which prefer
`ably do not generate amines or other N-H base groups in
`their formation processes. Upper low-k dielectric film 27 is
`formed over top surface 25 of etch-stop film 23. Upper
`low-k dielectric film 27 includes thickness 31 which may
`range from 1000 to 10000 angstroms depending on appli
`cation and other thicknesses may be used according to other
`exemplary embodiments. Hardmask film 33 is formed over
`upper low-k dielectric film 27. In an exemplary
`embodiment, hardmask film 33 may be formed of oxygen
`doped silicon carbide, SiC-O, but other oxygen
`containing, Substantially nitrogen-free films which prefer
`ably do not generate amines or other N-H base groups in
`their formation processes, may be used alternatively. An
`advantage of the film stack structure shown in FIG. 3 is that
`any amines, amino-Silanes and other N-H base groups
`which may be produced during the formation of lower
`barrier layer 11 and/or the treatment of upper Surface 3, are
`prevented by upper barrier layer film 13 from diffusing into
`the low-k dielectric films. Additionally, Since each of etch
`stop layer 23 and hardmask film 33 are formed of SiC O,
`or other oxygen-containing, nitrogen-free films, no amine or
`other N-H base groups are produced during the formation
`of films 23 and 33 to become nested in the low-k dielectric
`FIG. 4 shows opening 43 extending down from top
`surface 35 of hardmask film 33 and extending through
`hardmask film 33, upper low-k dielectric film 27, etch-stop
`layer 23 and lower low-k dielectric film 17. Opening 43
`terminates on top surface 15 of upper barrier layer film 13.
`Opening 43 may take on various other configurations
`according to other exemplary embodiments. Opening 43
`may extend to various widths and various different depths
`according to other exemplary embodiments. In other
`embodiments, opening 43 may not fully extend down to top
`surface 15 of upper barrier layer film 13. Opening 43
`includes width 49, and sidewalls 47 are formed between
`low-k dielectric materials and opening 43. Various Suitable
`means, Such as plasma etching, may be used to form opening
`43, after a masking pattern has been formed over the film
`Subsequent to the formation of opening 43, a dual
`damascene opening will desirably be formed utilizing open
`ing 43 as a portion of the dual-damascene, or two-tiered
`opening. AS Such, photosensitive film 45 is formed over the
`Structure using conventional methods Such as by coating.
`Photosensitive film 45 is formed over top surface 35 and fills
`opening 43. Photosensitive film 45 may be a commercially
`available photoresist such as DUV (deep ultra-violet) pho
`toresist. In an exemplary embodiment, photosensitive film
`45 may be a chemically-amplified DUV photoresist that
`includes acid catalysts which render the photoresist material
`soluble in developer when exposed to ultraviolet light. Other
`photosensitive materials may be used alternatively. Upper
`barrier layer film 13 prevents photosensitive film 45 from
`contacting lower barrier layer film 11. After photosensitive
`film 45 is formed as shown in FIG. 4, a pattern may be
`formed within photosensitive film 45 to create the dual
`damascene Structure.
`FIG. 5 shows the structure shown in FIG. 4 after an
`exemplary pattern has been formed using photomask 53.
`Photomask 53 includes transmissive section 57 and opaque
`Sections 55, chosen to be transmissive and opaque,
`respectively, to the light used to expose photoSensitive film
`45. The light which is used for exposure is chosen in
`conjunction with photosensitive film 45. In an exemplary
`embodiment, ultraViolet light may be used in conjunction
`with a DUV photoresist. When portions of photosensitive
`film 45 are exposed by a DUV light source through the
`transmissive portions of the pattern formed in photomask


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`US 6,879,046 B2
`53, these Selective, exposed portions of photoSensitive film
`45 become soluble in developer. When a developer Subse
`quently contacts photoSensitive film 45, the Sections which
`have been exposed and are Soluble in developer, are devel
`oped away, and a pattern is formed in photoSensitive film 45.
`A Substantially identical pattern can then be formed in the
`underlying Structure, Such as in the exemplary film Stack,
`using etching or other techniques. FIG. 5 shows exposed
`section 51 of photosensitive film 45. Exposed section 51
`includes width 59 and is soluble in developer. Due to upper
`barrier layer film 13, etch-stop layer 23, and hardmask film
`33 of the present invention, low-k dielectric films 17 and 27
`do not include base groupS. Such as N-H base groups or
`other nitrogen-containing base groupS. Such as amines or
`amino-Silicates. If present, Such base groups could pass
`through sidewalls 47, neutralize the acid catalysts within
`photosensitive film 45, and render insoluble portions of
`photosensitive film 45 which are desirably exposed and
`soluble in developer. Similarly, photosensitive film 45 is
`isolated from nitrogen-containing lower barrier layer film
`11, by upper barrier layer film 13 which prevents diffusion
`of base groups, as above, from lower barrier layer film 11
`and/or upper Surface 3, into photoSensitive film 45. Accord
`ing to the present invention, eXposed Section 51 of photo
`sensitive film 45 extends down to the bottom of opening 43
`(surface 15) and is substantially fully soluble in developer
`because the acid catalysts in photosensitive film 45 have not
`complexed with base groupS and have not been neutralized
`and rendered ineffective. The acid catalysts in exposed
`section 51 of photosensitive film 45 therefore render
`exposed Section 51 Soluble in developer after being exposed
`by ultraviolet light. After exposed section 51 has been
`developed and removed, an etching process may be used to
`form the exemplary dual-damascene Structure shown in FIG.
`In comparison, FIG. 6 is a cross-sectional view showing
`an exemplary structure as in the PRIOR ART. According to
`the prior art, a barrier layer Structure capable of preventing
`the diffusion of N-H base groups is not used, and at least
`one of optional barrier layer film 111, etch-stop layer 123,
`and hardmask film 127 may be formed to include nitrogen.
`Ammonia and other nitrogen-containing Species may be
`used to treat Surface 103 of conductive interconnect material
`105, and to form films 111, 123 and 127. AS Such, amines,
`amino-Silicates, and other N-H base groups may be pro
`duced during these Surface treatment and film production
`processes. In Some cases, barrier layer 111 may not be used
`and N-H or other base groups present on surface 103 may
`diffuse directly into low-k dielectric film 117. These amines,
`amino-Silicates, and other N-H base groups may addition
`ally or alternatively be included within formed films 111,
`123 and 127. These N-H base groups become nested in
`low-k dielectric films 117 and 125, by diffusion. From the
`low-k dielectric films, the N-H or other base groups diffuse
`through sidewall 137 and into photosensitive film 135 as
`indicated by arrows 151. Photosensitive film 135 includes
`exposed Section 141, but also includes neutralized Section
`167 in which N-H or other base groups have complexed
`with the acid catalysts to neutralize the acid catalysts and
`thereby render neutralized portion 167 insoluble. If the
`structure shown in the prior art illustration of FIG. 6 is
`exposed to developer, only exposed Section 141 will be
`developed away, and neutralized portion 167 will remain
`and prevent effective etching of the desired dual damascene
`Structure. If the desired dual damascene Structure is not
`properly formed and/or if the neutralized portion 167 of
`photoresist is not removed, opens may result between Sub
`jacent conductive interconnect material 105 and a conduc
`tive interconnect material desired to be introduced into the
`dual damascene Structure.
`FIG. 7 shows an exemplary dual-damascene or two-tiered
`opening formed after the Structure of the present invention
`shown in FIG. 5, has been exposed to developer, thereby
`forming a masking pattern in photosensitive film 45 (FIG.
`5), and Subsequently etched. Conventional etching tech
`niques Such as plasma etching may be used to form dual
`damascene opening 61. According to one exemplary
`embodiment, a Sequence of etch operations may be used to
`achieve the final, dual-damascene opening and may include
`an intermediate etching Step which terminates at etch-stop
`layer 23 and a Subsequent etching process Step to remove
`exposed portions of lower barrier layer film 11 and etch-Stop
`layer 23. Other etch proceSS Sequences may be used in other
`exemplary embodiments.
`Dual-damascene opening 61 extends down from top Sur
`face 35 of hardmask film 33 and through hardmask film 33,
`upper low-k dielectric film 27, etch-stop film 23, lower
`low-k dielectric film 17, upper barrier layer 13 and lower
`barrier layer film 11 and terminates on upper surface 3 of
`conductive line 5. Dual-damasce

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