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`USOO6057237A
`
`United States Patent
`
`[19]
`
`[11] Patent Number:
`
`6,057,237
`
`
`Ding et al.
`[45] Date of Patent:
`May 2, 2000
`
`[54] TANTALUM-CONTAINING BARRIER
`LAYERS FOR COPPER
`
`5,676,587 10,’1997 Landers et a].
`
`451/57
`
`[75]
`
`Inventors: Peijun Ding, San Jose; Tony
`Ping-Chen Chiang, Mountain View,
`both of Calif.
`
`Primary Examiner—Olik Chaudhuri
`Assistant Examiner—Ginette Peralta
`
`Attorney, Agent, or Firm—Birgit E. Morris
`
`[73] Assignee: Applied Materials, Inc., Santa Clara,
`Calif.
`
`[57]
`
`ABSTRACT
`
`[
`
`[
`
`l
`
`]
`
`Appl' NO" 08/841’058
`Filed:
`Apr. 29, 1997
`
`.... .. H01L 21/44
`Int. Cl.7
`[51]
`
`[
`l
`52 US. Cl.
`............
`438/687; 438/653; 257/751
`l
`]
`58
`Field of Search ..................................... 438/687, 751,
`438/653, FOR 350, FOR 352; 257/751
`
`[56]
`
`Raferences cued
`U.S. PATENT DOCUMENTS
`
`An improved barrier layer of tantalum to prevent diffusion
`of copper into a dielectric layer or silicon substrate is made
`by alternately sputter depositing thin amorphous tantalum
`layers and tantalum nitride layers. The resultant wholly
`amorphous tantalum-containing layer leads to a stronger
`barrier and prevents formation of a columnar structure in
`thick tantalum layers. The sputter depositions of tantalum
`and tantalum nitride can be repeated until
`the desired
`thickness of the barrier is obtained.
`
`5,391,517
`
`2/1995 Gelatos et a1.
`
`.......................... 437/190
`
`4 Claims, 2 Drawing Sheets
`
`
`
`Page 1 0f 5
`
`TSMC Exhibit 1029
`TSMC v. lP Bridge
`IPR2016-01249 & lPR2016-01264
`
`Page 1 of 5
`
`

`

`_ US. Patent
`
`May 2, 2000
`
`Sheet 1 0f2
`
`6,057,237
`
`
`
`Page 2 0f 5
`
`Page 2 of 5
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`

`

`XRD OF Ta/TaN SANDWICHED STRUCTURE
`
`800
`
`600
`
`Ta (002) PEAK HEIGHT 400
`
`200
`
`TaN = 50A
`
`TOTAL Ta = 1000A
`
`
`
`Ta(1000A)
`
`Ta/TaNfl'a
`
`Ta/TaN X2
`
`Tafl'aN X3
`
`Ta/TaN X4
`
`SAMPLES
`
`FIG. 3
`
`
`
`1119:le‘S'fl
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`000Z‘Z53W
`
`ZJ0Z199118
`
`L9Z‘LSO‘9
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`Page 3 of 5
`
`

`

`6,057,237
`
`1
`TANTALUM-CONTAINING BARRIER
`LAYERS FOR COPPER
`
`This invention relates to depositing improved tantalum
`barrier layers for overlying copper metal lines in the manu-
`facture of semiconductor devices. More particularly, this
`invention relates to the deposition of tantalum-containing
`barrier layers having enhanced barrier performance.
`BACKGROUND OF THE INVENTION
`
`u-
`
`10
`
`In the manufacture of semiconductor devices, conductive
`metal contacts and lines are deposited over dielectric layers,
`such as silicon oxide. The metal
`lines connect various
`devices to each other to form integrated circuits. Openings
`are made in the dielectric layer and filled with a conductive
`material so that contact between overlying lines and under-
`lying devices can also be made.
`As devices become smaller and more devices are made in
`a single semiconductor (silicon) wafer, the openings in the
`dielectric layer have a smaller diameter. These small diam-
`eter openings are difficult to fill, particularly using conven-
`tional sputter deposition processing.
`FIG. 1 illustrates a conventional sputtering chamber. A
`vacuum chamber 10 includes a target 12 of the material to
`be sputtered and a substrate support 14. A source of DC
`power 13 is connected to the target 12. A pair of opposed
`magnets 16 and 18 are mounted on top of the target 12. A
`power source 20, such as a source of RF power, is connected
`to the substrate support 14. During sputter deposition, a
`substrate 22 is mounted on the substrate support 14. A gas
`inlet 19 permits gases to be passed into the chamber. Argon
`is generally used as a sputtering gas. The argon is ionized in
`the chamber and is attracted to the target 12 by the magnets
`16, 18. The argon atoms strike the surface of the target and
`sputter off particles of target material which deposit on the
`substrate 22. If a material such as a nitride is to be formed
`on the substrate, nitrogen gas is also passed into the chamber
`where it is ionized and reacts with sputtered metal on the
`substrate.
`'
`
`Since sputtered particles are sputtered from a target in
`numerous random directions, comparatively few of the
`sputtered particles impact the target in a direction perpen-
`dicular to the substrate. Most of the sputtered particles thus
`impact the openings in the substrate at some other angle,
`causing the sputtered layer to build up along the sides and
`top of an opening rather than on the bottom. Further, as the
`aspect ratio of the opening becomes higher, it is even more
`difficult to cover the bottom of the opening. This top and side
`buildup creates an overhang over the opening, as shown in
`FIG. 2, which further prevents particles from depositing on
`the bottom of the opening. FIG. 2 illustrates an opening 100
`partially filled with sputtered metal 110.
`Aluminum has been widely used for the manufacture of
`conductive lines and contacts, but more recently copper has
`been tried. Copper is more conductive than aluminum, but
`has a similar problem as aluminum with respect
`to an
`underlying silicon substrate, i.e., at elevated temperatures
`the copper dilfuses and reacts with other materials in the
`integrated circuit, and thus a barrier layer needs to be
`deposited between the conductive metal and the substrate.
`Tantalum and tantalum nitride have been accepted as
`good barrier materials for copper to prevent the diffusion of
`copper into underlying layers. Tantalum can be deposited by
`sputtering, and, when sputtered in the presence of nitrogen,
`tantalum nitride is formed. Tantalum nitride is not as con-
`ductive as tantalum, and it has a tendency to peel otf the
`
`20
`
`30
`
`4O
`
`50
`
`6O
`
`2
`underlying substrate, probably due to high stress in the
`tantalum nitride film. This peeling also has the disadvantage
`that it causes the formation of particles, which is always
`undesirable.
`
`Tantalum is a better conductor and a better wetting agent,
`and thus is a good adhesive between copper and the under-
`lying substrate. However, the use of tantalum alone has the
`disadvantage that it is not as good a barrier as tantalum
`nitride. Thus efforts to improve tantalum-containing barrier
`layers for copper have continued.
`SUMMARY OF THE INVENTION
`
`We have found that by alternately depositing layers of
`tantalum and tantalum nitride, improved barrier layers for
`copper metal conductors are obtained.
`BRIEF DESCRIPTION OF THE DRAWING
`
`FIG. 1 is a schematic cross sectional view of a cnventional
`sputtering chamber.
`FIG. 2 is a schematic cross sectional view of a partially
`sputter filled opening in accordance with the prior art.
`FIG. 3 is an X-ray diffraction study of tantalum/tantalum
`nitride sandwiched films.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`X-ray difiraction results have shown that sputter depos-
`ited tantalum nitride has a highly amorphous structure that
`contributes to its excellent barrier properties. We have also
`found that when tantalum alone is deposited into an opening
`in silicon oxide,
`the amorphous silicon oxide structure
`causes the initial tantalum layer to be amorphous as well.
`This provides an initial dense tantalum layer. However, as
`the tantalum layer becomes thicker, the structure of the layer
`changes so that a loose, columnar structure is formed. This
`structure is not as good a barrier because an overlying metal
`layer, such as of copper, can move or ditfuse along the
`columnar pathways to the underlying substrate.
`Thus in accordance with the present process, after an
`initial dense amorphous tantalum layer is sputter deposited,
`a layer of amorphous tantalum nitride is deposited over the
`amorphous tantalum layer by adding nitrogen gas to the
`sputtering chamber. This tantalum nitride layer prevents
`formation of a columnar structure in the growing tantalum
`film. Thus by alternately depositing tantalum and tantalum
`nitride layers, a dense amorphous barrier layer that
`is
`adherent to the substrate is deposited. If a thicker barrier
`layer is required, the tantalum and tantalum nitride deposi-
`tions can be repeated as many times as are necessary to form
`the barrier layer thickness required. The tantalum nitride can
`also be deposited as the first layer, alternating with tantalum.
`FIG. 3 is an X—ray dilIraction study of tantalum (002
`crystal orientation) versus the number of alternating tanta-
`lum and tantalum nitride layers. Deposition of tantalum
`alone (1000 A thick) becomes less crystalline when a
`tantalum nitride layer is sandwiched between two tantalum
`layers. The total tantalum thickness is fixed at 1000 A in the
`study. As the layering is repeated, the composite becomes
`still more amorphous and dense, and very little crystallinity
`is to be seen.
`
`Another advantage to the present process and structure is
`that less nitrogen is used in the composite film than when
`tantalum nitride is deposited alone. This reduces the high
`film stress characteristic of tantalum nitride. High film stress
`contributes to a lack of adhesion between a barrier layer and
`
`Page 4 of 5
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`Page 4 of 5
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`

`
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`6,057,237
`
`3
`a substrate, and results in barrier layer peeling, and the
`consequent formation of particles. Thus in accordance with
`the Pmsmt Process, Pamde redumlofl 15 also Oblamed
`The Opening, HOW lined With a dense, wholly amOFPhOUS
`tantalum'comaining layer, F“ be filled Wlth CORP“, also by 5
`spunermg’ to form a hlghly conducuve Vla that has
`improved barrier properties that prevent diffusion of copper
`into an adjacent dielectric material during subsequent pro-
`gassing steps,
`Although the invention has been described in terms of 10
`specific embodiments,
`the invention is only meant to be
`limited by the Scope 0f the appended Claims
`We Clam]:
`1. A method of making amorphous barrier layers to line an
`opening to be filled with copper comprising
`a) sputter depositing a first layer selected from the group
`consisting of tantalum and tantalum nitride in said
`opening;
`b) s’putter depositing a second layer of the other of 20
`tantalum and tantalum nitride to line the bottom and
`sidewalls of the opening; and
`
`15
`
`4
`c) alternately repeating steps a) and b) until the layer is
`substantiany amorphous.
`2. A method according to claim 1 wherein the first layer
`is tantalum and the second layer is tantalum nitride.
`3. A method according to claim 1 wherein the first layer
`is tantalum nitride and the second layer is tantalum.
`1,.
`.
`.
`.
`.
`4' A methOd 0f m
`g a conducnve Vla compnsmg
`a) sputter depositing a first layer selected from the group
`consisting of tantalum and tantalum nitride in said
`opening,
`b) sputter depositing a second layer of tantalum and
`tantalum nitride to line the bottom and sidewalls of the
`opening;
`
`c) alternately repeating steps a) and b) until a preselected
`thickness of the liner is obtained and the liner is
`
`substantially amorphous, and
`
`d) filling said opening with copper.
`
`>k
`
`a:
`
`*
`
`a:
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`Page 5 0f 5
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`Page 5 of 5
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