United States Patent £19J
`Yu et al.
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`US005244534A
`[11] Patent Number:
`(45) Date of Patent:
`
`5,244,534
`Sep. 14, 1993
`
`(7S)
`
`(54] TWO.STEP CHEMICAL MECHANICAL
`POLISHING I'ROCESS FOR PRODUCING
`FLUSH AND PROTRUDING TUNGSTEN
`PLUGS
`Inventors: <luis C. Yu; Tnma T. Dou, both of
`Boise, ld.
`[73) Assignee: Micron TedulolOi)',IDc., Boise, Id.
`[21] Appl. No.: 124,980
`[22] Filed:
`Jan. 24, 1992
`IDt. a.s ............................................. H01L 21/00
`[51)
`[52) u.s. a. .................................... 156/636; 156/645;
`156/651; 437/195; 437/228
`(S8) Fielcl of Seardl ....................... 156/636, 651, 645;
`.
`437/195, 228
`
`[56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`3,841,031 10/ 1974 Walsh .
`4,193,226 3/1980 Gill, Jr. et al ..
`4,714,686 12/1987 Sander et al ........................ 437/195
`4,811,522 3/1989 Gill, Jr. et al ..
`4,936,950 6/1990 Doan et al .......................... 156/ 643
`4,992,135 211991 Doan ................................... 156/636
`5,055,426 10/1991 Manning ......... ; ................... 437/195
`5,137,597 8/1992 Curry, II et al . ................... 156/65 1
`5,152,868 10/1992 Schiltz et at . ....................... 156/651
`Primary Examin~r-Brian E . Hearn
`
`Assistant Examin~r-Laura M. Holtzman
`Attorney, Agent, or Firm- Stanley N. Protigal
`A.BSTRACT
`[57)
`A method for forming conductive plugs within an insu(cid:173)
`lation material is described. The inventive process re·
`suits in a plug of a material such as tungsten which is
`more even with the insulation layer surface than con·
`ventional plug formation techniques. Conventional pro(cid:173)
`cesses result in recessed plugs which are not easily or
`reliably coupled with subsequent layers of sputtered
`aluminum or other conductors. The inventive process
`uses a two-step chemical mechanical planarization tech(cid:173)
`nique. An insulation layer with contact boles is formed,
`and a metal layer is formed thereover. A polishing pad
`rotates against the wafer surface while a slurry selective
`to the metal removes the metal overlying the '.wafer
`surface, and also recesses the metal within the contact
`boles due to the chemical nature and fibrous element of
`the polishing pad. A second CMP step uses a slurry
`having an acid or base selective to the insulation mate(cid:173)
`rial to remove the insulator from around the metal. The
`slurry also contains abrasive materials which polish the
`metal surface so as to make the metal level with the
`insulation layer surface. Removal of the insulation ma(cid:173)
`terial can continue, thereby producing a slightly pro(cid:173)
`truding plug whic}) results in a more reliable contact
`from the substrate to subsequent conductive layers.
`
`23 Claims, l Drawing Sheets
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`16
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`001
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`SONY 1007
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`U.S. Patent
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`Sep. 14, 1993
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`Sheet 1 of 2
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`5,244,534
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`AG.2
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`U.S. Patent
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`Sep. 14, 1993
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`Sheet 2 of 2
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`AG.3
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`AG.4
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`1
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`5,244,534
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`15
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`TWO-STEP CHEMICAL MECHANICAL
`POLISHING PROCESS FOR PRODUCING FLUSH
`AND PROTRUDING TUNGSTEN PLUGS
`
`2
`4,193,226 and 4,811,522 to Gill, Jr. and U.S. Pat. No.
`3,841,031 to Walsh, for instance, disclose such appara(cid:173)
`tus.
`Deposited conductors are an integral part of every
`5 integrated circuit, and provide the role of surface wir-
`ing for conducting current. Specifically, the deposited
`FIELD OF THE INVENTION
`conductors are used to wire together the various com-
`The disclosed invention relates to the field of semi·
`ponents that are formed in the surface of the wafer.
`conductor manufacture. More specifically, a chemical
`Electronic devices formed within the wafer have active
`mechanical wafer polishing process is described which
`produces improved flush and protruding tungsten plugs 10 areas which must be contacted with conductive run-
`ners, such as metal. Typically, a layer of insulating
`rather than the recessed plugs produced by conven-
`material is applied atop the wafer and selectively
`tional tungsten plug etchback techniques. Coupling
`with subsequent layers of conductive material such as
`masked to provide contact opening patterns. The layer
`sputtered aluminum is therefore more easily accom-
`is subsequently etched for instance with a reactive ion
`1. h
`'
`P IS ed.
`etch (RIE), to provide contact openings from the upper
`BACKGROUND OF THE INVENTION
`surface of the insulating layer down into the wafer to
`provide electrical contact with selected active areas.
`. Integrat~ circuits are chemically. ~d physi~ly
`Certain metals and alloys deposited by vacuum evap(cid:173)
`lnteg~ated Into a substrate,. such ~ a Sl~tcon or galhum
`oration and sputtering techniques do not provide the
`20
`arserude wafe~, by pattemmg regtons m the subst~ate, most desired coverage within the contact openings
`and by patterrung layers ~n the substrate. These re~ons when applied to the surface of a wafer. An example of
`and layers can be conducttve, for conductor and reststor
`tal h. h t
`· all
`·d
`h
`·
`fabrication. They can also be of different conductivity
`a me w tc
`.Yptc Y provl es sue .poor c~ver~~e ts
`sputtered alummum, or allo~s o_f alummum wtt~ sdtcon
`types, which is essential for transistor and diode fabrica-
`tion. Up to a thousand or more devices are formed 25 and/?r copper. One meta~l~tton schem.e ~hich does
`provi~e good coverage ~thin contact vt~. ts tungsten
`simultaneously on the surface of a single wafer of semi-
`depostted by the chemtcal vapor depos1t10n (CVD)
`conductor material.
`tech~ique. Tungste? is not, however, as co~ducti.ve as
`It is essential for high device yields to start with a flat
`semiconductor wafer. If the process steps of device
`alummum. A~cordmgly, a tungs~en layer ts ~y~tcally
`fabrication are performed on a wafer surface that is not 30 etched or pohshed back to prov1de a plug Withm the
`uniform, various problems can occur which may result
`insulation layer, the plug having a flat upper surface
`in a large number of inoperable devices.
`which is flush with the surface of the insulator. A layer
`of aluminum would subsequently be applied atop the
`Previous methods used to ensure the wafer surface
`planarity included forming an oxide such as borophos-
`wafer surface to contact the plug. The aluminum layer
`phosilicate glass (BPSG) layer on the wafer surface, 35 is then selectively etched to provide the desired inter-
`then heating the wafer to reflow and planarize the oxide
`connecting runners coupling the tungsten with other
`layer. This "reflow" method of planarizing the wafer
`circuitry.
`FIG. 1 shows a desirable outcome of a process to
`surface was sufficient with fairly large device geome-
`tries, but as the technology allowed for smaller device
`produce a tungsten plug. In accordance with wafer
`feature sizes, this method produced unsatisfactory re- 40 fabrication techniques, a material such as an oxide layer
`suits.
`10 covers the material of the wafer substrate 12. The
`Another method ~hich has been ~sed to produce a
`tungsten 14 which fdls the contact hole 16 in the oxide
`plana~ wafer surface ts t? use the oxtde refl.ow method
`material 10 is level with the surface of the oxide layer.
`~escnbed a?ove, t~en spm coat the. wafer wtth photore-
`FIG.l illustrates one problem with present methods of
`stst. The spm coatm~ of the matenal on the wafer sur- 45 tungsten etch backs, an over etching within the contacts
`face fills .the low pomts and produces a pl~nar surface
`which recesses the tungsten 14 within the contact hole
`from wh~ch to sta~. Next, a dry etc?, whtch removes
`16 in the wafer surface 10. This can provide for poor
`photorestst and oxtde .at a rate suf!ictent~y close to 1:1,
`contact between the tungsten plug 14 with the alumi-
`removes the photo~estst and the ~gh pomts of the wa-
`num or aluminum alloy layer (not shown) which would
`f~thereby producmg a planar oxtde layer on the wafer SO be subsequently deposited by sputtering. It is difficult to
`5 ~:~ recently, chemical mechanical planarization
`provide reliable contacts be~ween the aluminum an~ the
`recessed tungsten plugs ~hich result from ~on~enttonal
`(CMP) processes have been used to planarize the sur-
`~ungsten etch back_ techniques such as reacttve lon etch-
`face of wafers in preparation for device fabrication. The
`CMP process involves holding a thin flat wafer of semi- 55 mg (RIE~..
`.
`In addttton to ~IE, anoth~r conventional tungsten
`conductor material against a rotating wetted polishing
`et~h back I?~s mcludes a smg~e-~tep CMP etchback
`pad surface under a controlled downward pressure. A
`polishing slurry such as a mixture of either a basic or
`usmg a J!?hshmg slurry and pohshmg pad. A layer of
`acidic solution used as a chemical etch component in
`tungsten 1s formed by CV:D or other means on~o the
`combination with alumina or silica particles used as an 60 wafer surface, thereby fdhng the contact holes m the
`abrasive etch component may be used. A rotating pol-
`insulation layer with tungsten._ The surface of the wafer
`ishing head or wafer carrier is typically used to hold the
`is polished to remove the tungsten overlying the surface
`of the wafer, which leaves the contact holes filled with
`wafer under controlled pressure against a rotating pol-
`ishing platen. The polishing platen is typically covered
`tungsten. Due to the chemical nature of the slurry and
`with a relatively soft wetted pad material such as blown 65 compressible nature of the polishing pad, a certain
`polyurethane.
`amount of the tungsten material is removed from the
`contact holes, leaving the recessed tungsten structure 14
`Such apparatus for polishing thin flat semiconductor
`wafers are well known in the art. U.S. Pat. Nos.
`of FIG. 2.
`
`004
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`

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`5,244,534
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`3
`U.S. Pat. No. 4,992,135 describes a method of etching
`back tungsten layers, which is incorporated herein by
`reference.
`A need remains for improved methods of etching
`back tungsten layers on semiconductor wafers to allow
`for good contact with layers of metal or other conduc(cid:173)
`tive material which are subsequently deposited.
`
`4
`DETAILED DESCRIPTION OF THE
`INVENTION
`The inventive process formed plugs from a conduc-
`5 tive material (in the instant case tungsten) which were
`even with, and in a second embodiment slightly pro(cid:173)
`truding from, a insulation layer such as oxide (BPSG in
`the instant case, or other materials such as Si02). The
`shape of the protruding plugs was controllably convex
`SUMMARY OF THE INVENTION
`An object of the invention is to provide a process for 10 and allowed for an improved surface with which to
`couple a subsequent layer of conductive material such
`forming contacts (plugs) of tungsten or other conduc-
`as aluminum.
`tive materials that results in a more uniform, nonre-
`The inventive process began with a wafer as shown in
`cessed plug.
`FIG. 3 fabricated by means known in the art having a
`Another object of the invention is to provide a pro- 15 layer of insulation material 10 such as an oxide (BPSG)
`cess for forming a plug of tungsten or other conductive
`which is approximately 2-3 p.m thick. Contact holes 16
`were formed into material 10 by any conventional pro-
`material which results in a better surface to connect
`with another material such as a layer of aluminum by
`cess. A layer of metal 30, tungsten in the instant case,
`virtue of the more uniform, nonrecessed characteristics
`filled the contact holes 16 and extended over the insula-
`of the plug.
`20 tion 10 surface. The tungsten layer 30 was formed by
`Yet another object of the invention is to provide a
`chemical vapor deposition (CVD) to most efficiently
`process for forming a plug of tungsten or other conduc-
`flll the contact holes 16, but workable methods known
`tive material which can produce uniform, protruding
`in the art are also possible. The layer of tungsten 30 over
`plugs which allow for easier coupling with subsequent
`the oxide s'!rface 10 in the instant case was approxi-
`layers of conductive material than recessed plugs pro- 25 mately lOKA thick, but other thicknesses are possible as
`duced by conventional methods.
`the layer is removed in subsequent wafer processing
`These objects of the invention are realized with an
`steps.
`.
`.
`.
`Next~ th_e wafer was subJected t~ a chem1cal me~ham-
`inventive two-step process of plug formation which
`cal pohshmg (CMP) process which was ~l~ctlve to
`uses chemical mechanical planarization (CMP) technol-
`ogy. A substrate of a material such as silicon having a 30 tungsten. The pr?Cess employed a poh~~ng pad
`~ounted_on a rotatmg platen. A slurry, contammg abra-
`layer of oxide (BPSG) is manufactured with contact
`s1ve particles such as Ah03 and etchants such as H202
`.
`.
`holes therem, and a layer of metal such as tungsten IS
`and either KOH or Nli40H, or other acids or bases,
`formed upon the s~bst~ate to ~lll the contact holes .. A
`removed the tungsten at a predictable rate, while re-
`first CMP step, wh1ch 1s select1ve to the plug mate~al, 35 moving very little of the insulation. This process is
`described in u.s. Pat. No. 4,992,135. The polishing pad
`removes t~e upper _layer of ~ungsten fro~ the ox1de
`surface while remo~mg very httle or no ox1de from !he
`was held in contact with the wafer surface at a pressure
`wafer surface. Dunng the last phase of the step wh1ch
`of 7-9 psi for approximately 5-10 minutes. This process
`completely removes metal residue including barriers
`resulted in the structure of FIG. 2, a tungsten plug 14
`such as titanium nitride and titanium layers over the 40 within the contact holes 16 in the oxide 10. The tung-
`sten 14 was slightly recessed at this stage in the process
`surface of the wafer, a portion of the tungsten below the
`level of the oxide surface is also removed, thereby re-
`as shown resulting from the mechanical erosion of the
`cessing the tungsten plugs. This recessed plug, which is
`tungsten from the fibers of the polishing pad. The mag-
`typical of conventional plug formation, is difficult to
`nitude of the recess typically varied from approximately
`couple with a subsequent layer of metal or other mate- 45 0.5KA to 3KA below the surface of the oxide 10. To
`rial.
`selectively remove the tungsten, the chemical compo-
`Therefore, a second CMP step which is selective to
`nent of the slurry oxidized the tungsten, and the tung-
`oxide material of the wafer surface, removes a portion
`sten oxide was removed mechanically with the abrasive
`of the insulation material to a level even with or material in the slurry. Additionally, a small portion of
`slightly below, the level of the tungsten plugs. To shape 50 the tungsten was remov~ by the ~brasive. In any case,
`the CMP proc~s u~d IS sel:cttve to d,ungsten and
`the tungsten extending above the surface so as to re-
`move the concave shape resulting from the plug recess,
`leaves the msulatlo? ayer relatively una ected:
`Th: second step m:'olved a ~MP ~rocess which was
`the slurry of the oxide CMP can be formulated so as to
`· d
`d
`t f
`t
`Thi
`be
`select1ve to the matenal of the msulauon layer, although
`remov~ a eSJr: amo.un ° tungs en.
`s can
`a~- 55 it may be desirable to remove a small amount of the
`comp~1shed by mcrea~mg the amount of etchant that 1s
`tungsten as well to either to polish the tungsten or to
`provide a convex protruding plug. If tungsten is re-
`selective to the matenal of the plug.
`BRIEF DESCRIPTION OF THE DRAWINGS
`moved at this step, it is done at a much slower rate than
`the removal of the insulation material. A slurry contain(cid:173)
`ing etchants selective to the oxide was added between a
`rotating polish pad and the wafer surface. The colloidal
`silica slurry used in the instant case contained abrasives
`as described above, and also etchants selective to the
`oxide, such as a basic mixture of H20 and KOH. In most
`cases, if other nonoxide insulators are used other chemi(cid:173)
`cal etchants would be required. As shown in FIG. 1, the
`insulation material 10 was removed from around the
`tungsten plugs 14, resulting in a plug 14 which was even
`
`FIG. 1 is a cross-section of a desirable plug;
`FIG. 2 is a cross-section of a recessed plug typically
`produced by a conventional CMP process;
`FIG. 3 is a cross-section of a first step in the inventive
`process showing a layer of conductive material (such as
`tungsten) formed over the substrate; and
`FIG. 4 is a cross-section of a protruding plug embodi(cid:173)
`ment which can be produced by the inventive two-step
`process.
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`60
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`5
`with the surface of the insulation material 10. The ac(cid:173)
`tion of the pad abraded the surface of the tungsten and
`the oxide material sufficient to polish out surface irregu(cid:173)
`larities. The tungsten was polished at a slow rate, less
`than SOA/minute, but the oxide underlayer was pol- S
`ished at a high rate, greater than 2SOOA/minute. Typi(cid:173)
`cally, a layer of O.S:KA-3KA of the insulation material
`is removed at the second CMP step, as this is the usual
`extent to which the tungsten is recessed within the
`contact hole.
`A second embodiment of the first step was also used
`to successfully form the tungsten plugs. This process
`used a novel polishing slurry comprising aluminum
`oxide (AhOJ) abrasive particles and a basic mixture of
`H20 and H202.It was found that the second base of the IS
`mixture as described above, KOH or Nf40H, had little
`effect on the speed or quality of the etch. In this novel
`slurry, H202 is used to oxidize the tungsten surface,
`forming tungsten oxide. The formed tungsten oxide is
`subsequently removed by the polishing process, creat- 20
`ing a fresh tungsten surface for continued surface reac(cid:173)
`tion between H202 and the tungsten surface. In con(cid:173)
`trast, the first embodiment of the first step describes the
`use of H202 and a second chemical component such as
`KOH or Nf40H which served to remove tungsten
`oxide chemically. It has been found that the tungsten
`oxide is sufficiently removed by the mechanical polish(cid:173)
`ing effect of the abrasive within the slurry. With this
`new slurry, a polishing rate of 1KA/minute to 3KA/mi- 30
`nute was found, depending on the H202 to H20 ratio. A
`100% solution of H202 removed the tungsten oxide at
`about 3KA/minute, while a 1:1 ratio by volume of
`H202 to H20 removed the tungsten oxide at around
`O.SKA/minute. Using the inventive slurry, a good tung- 35
`sten to insulation (i.e. BPSG) polishing selectivity was
`obtained, and was determined to be approximately 20:1.
`In another embodiment of the invention, the second
`wafer polishing step which removed the oxide 10 was
`continued to remove additional insulation material 10 40
`and to produce a convexly rounded protruding tungsten
`plug 40 as shown in FIG. 4, although this is not a re(cid:173)
`quirement of the inventive process. The rounded sur(cid:173)
`faces of the tungsten plugs 40 provided surfaces which
`were easily coupled to layers of aluminum (not shown) 45
`formed by sputtering or other means during subsequent
`wafer processing steps. Tungsten plugs with a diameter
`of less than 1 micron were produced
`In addition to producing uniform plugs which were
`not recessed within the insulation layer, the inventive so
`two-step process resulted in more planarized wafer
`surface due to the oxide polishing in the second step.
`What have been described are specific configurations
`of the invention, as applied to particular embodiments.
`Clearly, variations can be made to the original methods ss
`and materials described in this document for adapting
`the invention to other embodiments. For example, insu(cid:173)
`lators other than those comprising oxide could be used,
`for example Si3N4. For these nonoxide insulators, how(cid:173)
`ever, a chemical etchant other than the KOH and water 60
`solution would most likely be required. Also, various
`acids, bases, and abrasive materials can be used in the
`CMP slurry to maintain the scope and spirit of the in(cid:173)
`vention. Therefore, the invention should be read as
`limited only by the appended claims.
`What is claimed is:
`1. A method of producing a conductive plug in an
`insulation layer, comprising the steps of:
`
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`6
`a) removing a portion of the insulation layer to form
`a contact hole within the insulation layer;
`b) applying a layer of conductive material to a surface
`of the insulation layer, thereby filling said contact
`hole with said conductive material and resulting in
`a layer of said conductive material over said insula·
`tion layer surface;
`c) removing at least a portion of said conductive
`material from said surface of the insulation layer
`and leaving said contact hole substantially filled
`• with said conductive material, said removing being
`performed by chemical mechanical planarization
`with a slurry comprising an abrasive material and
`an oxidizing component, said oxidizing component
`comprising hydrogen peroxide and water wherein
`a ratio by volume of hydrogen peroxide to water is
`in the range of 1:0 to 1:1;
`d) removing some of the insulation layer to lower said
`insulation layer surface with respect to an upper
`surface of said conductive material.
`l. The method of claim 1, wherein said contact hole
`is formed by etching.
`3. The method of claim 1, wherein said conductive
`layer is formed by chemical vapor deposition.
`4. The method of claim 1, wherein said abrasive mate(cid:173)
`rial comprises aluminum oxide.
`5. The method of claim 1, wherein step d) is done by
`chemical mechanical planarization.
`6. The method of claim 5, wherein step d) comprises
`the use of a slurry having an abrasive material and a
`compound which selectively removes a portion of the
`insulation layer.
`7. The method of claim 6, wherein said abrasive mate(cid:173)
`rial comprises silica.
`8. The method of claim 6, wherein said compound
`comprises potassium hydroxide.
`9. The method of claim 1, wherein between O.SKA
`and 3KA of the substrate material is removed during
`step d).
`10. The method of claim 1, wherein step d) continues
`until said insulation layer surface is substantially even
`with said upper surface of said conductive material.
`11. The method of claim 1, wherein step d) continues
`until said insulation layer surface is lower than said
`upper surface of said conductive material, thereby re(cid:173)
`sulting in said conductive material protruding from said
`insulation layer surface.
`ll. The method of claim 1, wherein the plug formed
`comprises tungsten.
`13. The method of claim ll, wherein during step c) a
`portion of said tungsten reacts with said hydrogen per(cid:173)
`oxide to form tungsten oxide.
`14. The method of claim 1, wherein the insulation
`layer comprises an insulating dielectric layer.
`15. The method of claim 14, wherein between O.S KA
`and 3KA of the substrate material is removed in step d).
`16. The method of claim 1, wherein the substrate
`material comprises polyimide.
`17. A method of chemical mechanical planarization
`of an oxide material, comprising the steps of:
`a) etching a portion of the oxide material to form a
`contact hole within said oxide material;
`b) applying a layer of tungsten to a surface of the
`oxide material, thereby filling said contact hole
`with said tungsten and resulting in a layer of said
`tungsten material over said oxide material;
`c) chemically and mechanically removing at least a
`portion of said tungsten from said surface of said
`
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`a layer of said conductive material over said insula(cid:173)
`tion layer surface;
`c) removing at least a portion of said conductive
`material from said surface of the insulation layer
`and leaving said contact hole substantially filled
`with said conductive material;
`d) removing some of the insulation layer by chemical
`mechanical planarization using a slurry, said slurry
`having an abrasive material and a compound which
`selectively removes a portion of said insulation
`layer to lower said insulation layer surface with
`respect to an upper surface of said conductive ma(cid:173)
`terial;
`e) removing at least a portion of said conductive
`material from said surface of the insulation layer
`and leaving said contact hole substantially filled
`with said conductive material, said removing being
`performed by chemical mechanical planarization
`with a slurry comprising an abrasive material and
`an oxidizing component and a carrier, wherein a
`ratio by volume of the oxidizing component to the
`carrier is in the range of 1 :0 to 1:1;
`f) removing some of the insulation layer to lower said
`insulation layer surface with respect to an upper
`surface of said conductive material.
`22. The method of claim 21, wherein said abrasive
`material comprises silica.
`23. The method of claim 21, wherein said compound
`comprises potassium hydroxide.
`• • • • *
`
`7
`oxide material with a flrst solution compnsmg
`H202 water, and an abrasive material, and leaving
`said contact hole substantially flied with said tung(cid:173)
`sten, wherein a ratio by a volume of said H202 to
`said water is in the range of 1:0 to 1:1;
`d) chemically and mechanically removing a portion
`of the oxide material with a second solution com(cid:173)
`prising KOH and an abrasive material to lower said
`surface of said oxide material with respect to an
`upper surface of said tungsten;
`whereby a plug of tungsten is formed in said contact
`hole.
`18. The method of claim 17, wherein between o.sKA
`and 3KA of said oxide material is removed during step
`4
`19. The method of claim 17, wherein step d) contin(cid:173)
`ues until said surface of said oxide material is substan(cid:173)
`tially even with said upper surface of said tungsten.
`20. The method of claim 17, wherein step d) contin(cid:173)
`ues until said surface of said oxide material is lower than 20
`said upper surface of said conductive material, thereby
`resulting in said tungsten protruding from the oxide
`material.
`21. A method of producing a conductive plug in an
`insulation layer, comprising the steps of:
`a) removing a portion of the insulation layer to form
`a contact hole within the insulation layer;
`b) applying a layer of conductive material to a surface
`of the insulation layer, thereby fllling said contact
`hole with said conductive material and resulting in 30
`
`25
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`35
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`40
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`45
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`so
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`ss
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`60
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`65
`
`007