`Tagami et al.
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`US006538324Bl
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,538,324 Bl
`Mar.25,2003
`
`(54) MULTI-LAYERED WIRING LAYER AND
`METHOD OF FABRICATING THE SAME
`
`(75)
`
`Inventors: Masayoshi Tagami, Tokyo (JP);
`Yoshihiro Hayashi, Tokyo (JP)
`
`(73) Assignee: NEC Corporation, Tokyo (JP)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/596,415
`
`(22) Filed:
`
`Jun. 19,2000
`
`(30)
`
`Foreign Application Priority Data
`
`Jun. 24, 1999
`
`(JP) ........................................... 11-214110
`
`Int. CI? .......................... HOlL 23/48; HOlL 23/52
`(51)
`(52) U.S. Cl. ........................................ 257/751; 257/762
`(58) Field of Search ................................. 257!751, 752,
`257!753, 758, 762, 773; 438/626, 627,
`628, 643, 644, 645
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`5,668,411 A * 9/1997 Hong eta!. ................. 257/751
`5,858,873 A * 1!1999 Vitkavage et a!. .......... 438/626
`
`FOREIGN PATENT DOCUMENTS
`
`JP
`JP
`JP
`JP
`JP
`
`8-139092
`8-274098
`9-64044
`9-293690
`10-256256
`
`5/1996
`10/1996
`3/1997
`* 11/1997
`9/1998
`
`OTHER PUBLICATIONS
`
`Semiconductor World Nobuyoshi Awaya, Feb. 1998, pp.
`91-96.
`Kee-Won Kwon et al., "Characteristics of Ta As An Under(cid:173)
`layer for Cu Interconnects", Advanced Metallization and
`Interconnect Systems for ULSIApplications in 1997, 1998,
`pp. 711-716.
`M. T. Wang, et al., "Barrier Properties of Very Thin Ta and
`TaN Layers Against Copper Diffusion", Journal Electro(cid:173)
`chemical Society, Jul. 1998, pp. 2538-2545.
`D. Denning, et al., An Inlaid CVD Cu Based Integration for
`Sub 0.25,um Technology, 1998 Symposium on VLSI Tech(cid:173)
`nology Digest of Technical Papers, 1998, pp. 22-23.
`
`* cited by examiner
`
`Primary Examiner-Tom Thomas
`Assistant Examiner-Hung Kim Vu
`(74) Attorney, Agent, or Firm---Scully, Scott, Murphy &
`Presser
`
`(57)
`
`ABSTRACT
`
`There is provided a barrier film preventing diffusion of
`copper from a copper wiring layer formed on a semicon(cid:173)
`ductor substrate. The barrier film has a multi-layered struc(cid:173)
`ture of first and second films wherein the first film is
`composed of crystalline metal containing nitrogen therein,
`and the second film is composed of amorphous metal nitride.
`The barrier film is constituted of common metal atomic
`species. The barrier film prevents copper diffusion from a
`copper wiring layer into a semiconductor device, and has
`sufficient adhesion characteristic to both a copper film and
`an interlayer insulating film.
`
`10 Claims, 20 Drawing Sheets
`
`18
`
`TSMC Exhibit 1001
`
`Page 1 of 31
`
`
`
`U.S. Patent
`
`Mar. 25, 2003
`
`Sheet 1 of 20
`
`US 6,538,324 Bl
`
`1
`
`3
`
`6
`
`4
`
`FIG. 1
`(Prior Art)
`
`FIG. 2
`(Prior Art)
`
`FIG. 3
`(Prior Art)
`
`5
`
`Sa
`
`Page 2 of 31
`
`
`
`U.S. Patent
`
`Mar. 25, 2003
`
`Sheet 2 of 20
`
`US 6,538,324 Bl
`
`FIG. 4A
`
`FIG. 48
`
`17
`
`Page 3 of 31
`
`
`
`U.S. Patent
`
`Mar. 25, 2003
`
`Sheet 3 of 20
`
`US 6,538,324 Bl
`
`FIG. 4C
`
`18
`
`FIG. 40
`
`Page 4 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 4 of 20
`
`US 6,538,324 Bl
`
`21
`
`25
`
`"-""''-"""'-"""'-""''-""'-"""'-"""'-"""'-'"''-"'
`'-"""'-"""'-""'-""'-'"''-"''-""'-'"''-'"''-'"' ...........
`'-""''-"""'-'"''-""''-"""'-'"''-'"''-'"''-"''-'"''-"'-'"'
`......................................................... '-'"''-""'-'"''-'"''-'"''-""''-'"''-""'
`'-'"'"-"" ........... '-'"''-"""'-'"''-'"' ........................................ '-"'"-""
`
`.................................................................................................................................................
`
`............................................................................... ~ ..................... .._,... ........... ' - J '
`
`...................... ._..... ................................................................................................. '-"""
`..................................... ,_....,_ ................................................. '-""' .............
`.............
`'-'"''-'"' ........................................ '-'"' ......... '-'"' .........
`...,.... .........................................................................
`,__
`~~~~r~
`
`26
`
`22
`I
`
`34
`
`60
`
`33
`
`FIG. 5
`
`(.!)
`
`40
`
`30
`
`20
`
`- 50
`~ 0 -w
`~ w
`>
`0
`(.)
`:!'!
`0
`1-
`1-
`0 m
`
`10
`
`0
`
`1
`
`1.5
`
`2
`
`3
`2.5
`3.5
`ASPECT RATIO
`
`4
`
`4.5
`
`5
`
`FIG. 6
`
`Page 5 of 31
`
`
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 5 of 20
`
`US 6,538,324 Bl
`
`35
`
`j
`
`FIG. 7
`
`37
`
`FIG. 8
`
`Page 6 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 6 of 20
`
`US 6,538,324 Bl
`
`1000
`
`-
`
`E
`(.)
`I
`c:
`::i.
`..___..
`Q..
`
`~
`-
`>
`-
`1-
`en
`-
`en
`w a:
`
`800
`
`600
`
`400
`
`200
`
`:.c
`
`I
`I
`
`I 13Pa, 3kW
`
`I
`I
`I
`I
`I
`I
`
`13Pa, 2kW
`0
`
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`
`... *
`
`13Pa, 6kW
`
`13Pa, 8kW
`
`-·
`
`_. _. ........
`
`0
`
`0
`
`.~
`
`2
`
`4
`
`6
`
`8
`
`10
`
`FIG. 9
`
`Page 7 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 7 of 20
`
`US 6,538,324 Bl
`
`20000 ,---------r------.-------.-1----,
`
`-rJ)
`Q,) -c:
`
`c.
`.......
`0
`>-
`.:t:::
`rJ)
`c:
`
`15000 r-
`
`10000 r-
`
`5000
`
`(3-Ta(002)
`
`0 ~---~--~/~\-----~--~
`25
`30
`35
`40
`45
`28 (deg.)
`FIG. 10
`
`I
`
`I
`
`I
`
`(3-Ta(002)
`
`TaN0 1 (011)
`'
`-
`
`5000
`
`4000 1--
`
`3000
`
`1-
`
`2000 -
`
`1000
`
`-rJ)
`Q,) -s:::
`
`c.
`.......
`0
`>-
`.:t:::
`rJ)
`c:
`
`0
`25
`
`30
`
`J
`
`35
`28 (deg.)
`FIG. 11
`
`40
`
`45
`
`Page 8 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 8 of 20
`
`US 6,538,324 Bl
`
`2000 ~----~------~----~------~
`
`Q.
`
`-t/)
`(.) ->-:!::
`t/) r::
`.... r::
`
`Q)
`
`1500
`
`1000
`
`500
`
`Ta2 N
`
`0
`
`25
`
`30
`
`40
`
`45
`
`35
`20 (deg.)
`FIG. 12
`
`5000
`
`4000
`
`3000
`
`2000
`
`1000
`
`-t/) c.
`(.) ->-.:!:::
`t/) r::
`.... r::
`
`Q)
`
`Ta2 N5 (113) or (041)
`
`Ta 3 N5 (132)
`or (042)
`
`0
`
`25
`
`30
`
`35
`
`40
`
`45
`
`20 (deg.)
`FIG. 13
`
`Page 9 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 9 of 20
`
`US 6,538,324 Bl
`
`300
`
`250
`
`200
`
`-E
`::t - 150
`.::!!!: -.~ 100
`
`(J
`I
`
`c:
`
`>-::::
`
`en
`(1)
`a:
`
`CRYSTALLINE
`o .. (3- Ta & TaN 0.1
`.. o-------0
`
`8
`
`10
`
`2
`
`6
`4
`RF Power (kW)
`FIG. 14
`
`Ta2 N
`
`50
`
`0
`
`0
`
`-en c.
`(J ->-.:!::
`(1) -c::::
`
`en
`c::::
`
`1500
`
`1000
`
`500
`
`25
`
`30
`
`40
`
`45
`
`35
`28 (deg.)
`FIG. 15
`
`Page 10 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 10 of 20
`
`US 6,538,324 Bl
`
`1 0000 .------------,------,--------;------,
`
`TaN0_1
`(11 0)
`
`-rn c.
`C1) -c::::
`
`(,)
`.........
`>
`:!::: rn
`c::::
`
`8000
`
`6000
`
`4000
`
`2000
`
`-rn c.
`
`C1) -c::::
`
`(,)
`.........
`~ 10000
`rn
`c::::
`
`0 L-----~~~~~~-~==~==~
`45
`40
`35
`30
`25
`
`28 (deg.)
`FIG. 16
`20000 .--------;------,---------;-----,
`
`15000
`
`TaN 0 _1 (11 0)
`
`5000
`
`0
`25
`
`~-Ta(002)
`)\.
`35
`
`L
`30
`
`~
`
`40
`
`45
`
`28 (deg.)
`FIG. 17
`
`Page 11 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 11 of 20
`
`US 6,538,324 Bl
`
`20000 r - - - - - - - , - , - - - - - , - - - - - - - - - r - - - - - - - - ,
`
`~-Ta
`
`15000 f-
`
`-UJ c.
`(.) -~ 10000 f-
`Q) -c:
`
`.:t::=
`UJ
`c:
`
`5000
`
`-
`
`-
`
`-
`
`Taho.1
`
`28 {deg.)
`
`FIG. 18
`
`Page 12 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 12 of 20
`
`US 6,538,324 Bl
`
`··············I· .... G·· .. 1
`
`. : : .. :· ·.
`
`.
`
`. 511
`
`:.·.
`
`;
`: .
`• '
`
`'
`
`:
`: .
`
`'
`
`;
`.
`
`:
`' .
`
`F·
`
`Page 13 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 13 of 20
`
`US 6,538,324 Bl
`
`. ·.·· .'-
`1:j6_: '·· ....... .
`
`----- --G-
`Fl··· •·••·
`
`2··--o···._
`
`••·······•·.·.·••,••.•
`
`Page 14 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 14 of 20
`
`US 6,538,324 Bl
`
`17
`
`FIG. 21
`
`Page 15 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 15 of 20
`
`US 6,538,324 Bl
`
`15
`
`'F'IG 2· 2·
`
`~
`
`>
`
`: i
`
`.. · .. · •. ·.. :ll
`
`. . • . . . . .· .. > > > > •
`
`Page 16 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 16 of 20
`
`US 6,538,324 Bl
`
`16
`
`FIG. 23
`
`29
`
`41
`
`21
`
`22
`
`31
`
`33
`---+--+
`
`34
`
`FIG. 24
`
`Page 17 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 17 of 20
`
`US 6,538,324 Bl
`
`16
`
`FIG. 25
`
`FIG. 26
`
`Page 18 of 31
`
`
`
`U.S. Patent
`
`Mar. 25, 2003
`
`Sheet 18 of 20
`
`US 6,538,324 Bl
`
`50
`~
`
`45
`
`FIG. 27
`
`Page 19 of 31
`
`
`
`U.S. Patent
`
`Mar.25,2003
`
`Sheet 19 of 20
`
`US 6,538,324 Bl
`
`z
`0
`~ a:
`
`.... ~ ze Wo o(cid:173)zcn
`
`oE
`u.S
`w..!..
`z
`a:
`0
`:;:)
`..J
`LL
`
`: Barrier Film
`MOCVD-Cu :
`After Annealing
`(3-Ta
`
`Ta2 N
`
`I
`
`LTaN0.1
`
`-~..
`/
`-~.
`~-
`~ ·, ·~
`I
`i i ..
`
`I
`
`Just After
`Film
`Deposition :
`Ta2N
`1015~----~~--~~~~~~~~~~
`1000
`500
`0
`DEPTH {A)
`FIG. 28
`
`z
`0
`~
`a:(cid:173)
`t-C'?
`ZE wo
`O(i)
`ZE
`Oo o-;
`a:(cid:173)
`w
`c.
`a.
`0
`()
`
`i Barrier Film
`, _ __.,
`
`After Annealing
`
`, ,-)(3-Ta
`·
`TaN
`2
`
`1 O 19 MOCVD-~u
`
`Just Afte'r Film
`Deposition
`Ta2N
`
`1015~~--~~--~~-U--~~~~~~~
`1000
`500
`0
`
`DEPTH (A)
`FIG. 29
`
`Page 20 of 31
`
`
`
`U.S. Patent
`
`Mar. 25, 2003
`
`Sheet 20 of 20
`
`US 6,538,324 Bl
`
`53
`
`17
`
`FIG. 30
`
`FIG. 31
`
`Page 21 of 31
`
`
`
`US 6,538,324 Bl
`
`1
`MULTI-LAYERED WIRING LAYER AND
`METHOD OF FABRICATING THE SAME
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The invention relates to a semiconductor integrated circuit
`including a copper wiring layer, and more particularly to a
`barrier film which prevents copper diffusion from such a
`copper wiring layer.
`2. Description of the Related Art
`As a semiconductor device has been designed to be
`smaller and smaller in size, wiring delay exerts greater
`influence on a silicon ULSI device. As a result, though a 15
`wiring layer has been composed of aluminum, it is necessary
`to compose a wiring layer of copper in place of aluminum.
`Resistivity of copper is equal to about 70% of resistivity
`of aluminum. However, since copper does not form passive
`state composed of an oxide film, at a surface thereof, unlike 20
`aluminum, copper is more corrosive than aluminum.
`In addition, since copper has a high diffusion rate in both
`silicon (Si) and silicon dioxide (Si0 2), if copper enters
`MOSFET formed on a silicon substrate, copper would
`induce reduction in carrier lifetime.
`Hence, it is absolutely necessary for a semiconductor
`device having a copper wiring layer to have a diffusion(cid:173)
`barrier film for preventing diffusion of copper into an
`interlayer insulating film formed between copper wiring
`layers. In addition, since such a diffusion-barrier film has to
`have high adhesion characteristic to both an interlayer
`insulating film and a copper wiring layer in order to keep
`reliability in wiring.
`Thus, there have been made many suggestions about a
`structure of a barrier metal layer and a method of fabricating 35
`the same, in order to prevent copper diffusion form a copper
`wiring layer.
`For instance, a structure of a barrier metal layer is
`suggested in the following articles:
`(a) Semiconductor World, Nobuyoshi Awaya, February
`1998, pp. 91-96 (hereinafter, referred to as Prior Art 1);
`(b) Advanced Metallization and Interconnect Systems for
`ULSI Applications in 1997, Kee-Won Kwon et al.,
`1998, pp. 711-716 (hereinafter, referred to Prior Art 2);
`(c) Journal Electrochemical Society, M. T. Wang et al.,
`July 1998, pp. 2538-2545 (hereinafter, referred to as
`Prior Art 3); and
`(d) 1998 Symposium on VLSI Technology Digest of
`Technical Papers, D. Denning et al., 1998, pp. 22-23. 50
`In addition, a structure of a barrier metal layer and a
`method of fabricating the same both for preventing copper
`diffusion is suggested also in Japanese Unexamined Patent
`Publications 8-139092, 8-274098, 9-64044 and 10-256256,
`and Japanese Patent Application No. 10-330938. Herein, 55
`Japanese Patent Application No. 10-330938 is not published
`yet, and hence does not constitute prior art to the present
`invention. However, it is explained in the specification only
`for better understanding of the present invention. The appli(cid:173)
`cant does not admit that Japanese Patent Application No. 60
`10-330938 constitutes prior art to the present invention.
`It is quite difficult to dry-etch copper, and hence, a copper
`wiring layer is formed generally by chemical mechanical
`polishing (CMP).
`Specifically, a copper wiring layer is formed as follows. 65
`An insulating film is formed on an underlying copper
`wiring layer. Then, the insulating film is formed with a
`
`2
`recess and a through-hole reaching the underlying copper
`wiring layer. Then, a thin diffusion-barrier film is formed on
`surfaces of the recess and the through-hole therewith such
`that the recess and the through-hole is completely covered at
`5 surfaces thereof with the diffusion-barrier film in order to
`prevent copper diffusion from uncovered region.
`Thereafter, a copper film is deposited filling the recess and
`the through-hole therewith by CVD or sputtering. Then, the
`copper film and the diffusion-barrier film are removed in
`10 selected regions by CMP. Thus, a copper wiring layer is
`completed.
`As will be obvious to those skilled in the art, the diffusion(cid:173)
`barrier film is required to have high coverage as well as
`capability of preventing copper diffusion and adhesion to
`copper.
`The diffusion-barrier film is composed, for instance, of
`refractive metal such as tungsten (W), tantalum (Ta) or
`titanium (Ti), or nitride of such refractive metal such as
`tungsten nitride (WN), titanium nitride (TiN) or tantalum
`nitride (TaN).
`As explained in Prior Art 2, for instance, a tantalum (Ta)
`barrier film has high adhesion with a copper film formed on
`the tantalum barrier film by sputtering, ensuring improve(cid:173)
`ment in crystallinity of the copper film. However, since
`25 copper is diffused into the tantalum film, it would be
`necessary for the tantalum barrier film formed below the
`copper film, to have a thickness of 50 nm or greater.
`Prior Art 4 reports that if a copper film is formed on a
`tantalum film by CVD, fluorine (F) segregates at an interface
`30 between the copper film and TaN, resulting in degradation in
`adhesion therebetween.
`Prior Art 3 reports that a crystalline TaN barrier film
`oriented in directions of (200) and (111) can prevent copper
`diffusion more highly than a crystalline Ta barrier film.
`As an solution to enhance a characteristic of preventing
`copper diffusion and adhesion to copper, a multi-layered
`structure of a metal film and a metal nitride film has been
`suggested.
`For instance, the above-mentioned Japanese Patent Appli-
`40 cation No. 10-330938 has suggested a method of fabricating
`a multi-layered barrier film including a titanium film and
`formed by sputtering.
`As illustrated in FIG. 1, in accordance with the suggested
`method, only an argon gas is introduced into a sputter
`45 chamber to thereby form a titanium film 1. Then, a nitrogen
`gas is introduced into the sputter chamber, and a thin
`titanium nitride film 2 is formed on the titanium film 1
`auxiliarily making use of reaction between titanium and
`nitrogen. Thus, there is formed a multi-layered barrier
`structure 3 comprised of the titanium film 1 and the thin
`titanium nitride film 2.
`In the method, a metal oxide film formed on an underlying
`wiring film is removed by argon plasma prior to carrying out
`sputtering.
`However, the conventional barrier film for preventing
`copper diffusion is accompanied with the following prob(cid:173)
`lems.
`The first problem is that it is quite difficult to make a
`diffusion-barrier film have both a characteristic of prevent(cid:173)
`ing copper diffusion and a sufficient adhesive force with
`copper.
`As illustrated in FIG. 2, it is now assumed to form a metal
`film 5 having a crystallized pillar structure, on a semicon(cid:173)
`ductor substrate 4. In the metal film 5, a lot of grains each
`comprised of individual crystals, and grain boundaries 7
`each defining an interface between the grains 6 exist
`throughout the metal film 5, that is, from an upper surface to
`
`Page 22 of 31
`
`
`
`US 6,538,324 Bl
`
`3
`a bottom of the metal film S. The grain boundaries 7 define
`paths 8 through which copper is diffused. As a result, the
`metal film S has low barrier characteristic of preventing
`copper diffusion.
`As illustrated in FIG. 3, it is now assumed to form a metal 5
`film Sa on a semiconductor substrate 4. If the metal film Sa
`is composed of metals having small resistivity, such as
`tungsten (W), titanium (Ti) or tantalum (Ta), the metal film
`S would have a polycrystal structure. As a result, the metal
`film Sa would have a pillar-like structure similarly to the 10
`metal filmS illustrated in FIG. 2, and accordingly, the metal
`film Sa would have small barrier characteristic of preventing
`copper diffusion.
`However, it should be noted that if a copper film is formed
`on a crystalline metal film, such as a ~-Ta (002) film as 15
`obtained in sputtering of a tantalum film, by sputtering, the
`copper film would have high adhesion and rich crystal
`orientation, though a barrier characteristic of preventing
`copper diffusion would be deteriorated. As a result, the
`copper film would enhance reliability in copper wiring.
`In contrast, the metal film Sa illustrated in FIG. 3, which
`is composed of particles 9 such as amorphous TaN and
`formed on the semiconductor substrate 4, has small
`resistivity, specifically in the range of about 200 to 250
`,uQcm, and does not have the paths through which copper is 25
`diffused unlike the crystalline metal filmS illustrated in FIG.
`2. As a result, the metal film Sa would have high barrier
`characteristic of preventing copper diffusion.
`However, since a surface of the metal film Sa is amor(cid:173)
`phous and hence crystal lattice is not uniformly arranged, if 30
`a copper film s formed on the amorphous metal film Sa by
`CVD or sputtering, copper crystallinity and adhesion to
`copper are degraded.
`As mentioned so far, it is quite difficult to form a
`diffusion-barrier film having a single-layered structure com- 35
`prised only of a crystalline metal film or an amorphous metal
`nitride film, and further having high barrier characteristic of
`preventing copper diffusion and high adhesion to copper.
`The second problem is caused when a diffusion-barrier
`film is designed to have a multi-layered structure in order to 40
`avoid the above-mentioned problem of the single-layered
`diffusion-barrier film.
`For instance, if a diffusion-barrier film is designed to have
`a multi-layered structure comprised of a crystalline metal
`film having high adhesion to copper and an amorphous
`metal nitride film having high barrier characteristic, such as
`TaN, there would be obtained a diffusion-barrier film having
`high barrier characteristic of preventing copper diffusion and
`high adhesion to copper.
`However, since it was not possible in a conventional 50
`method to successively form a crystalline metal film and an
`amorphous metal nitride film by sputtering, the crystalline
`metal film and the amorphous metal nitride film had to be
`separately formed in the same sputtering chamber or be
`formed in separate sputtering chambers.
`For instance, the above-mentioned Japanese Patent Appli(cid:173)
`cation No. 10-330938 has suggested a method including the
`steps of introducing an argon gas into a sputtering chamber
`to thereby form a titanium film, and introducing a nitrogen
`gas into the sputtering chamber to thereby form a titanium 60
`nitride film on the titanium film.
`However, in accordance with this method, the titanium
`nitride film cannot be formed until partial pressures of argon
`and nitrogen become stable by varying a mixture ratio of
`argon and nitrogen. Hence, it is impossible to enhance a 65
`fabrication yield of fabricating a diffusion-barrier film hav(cid:173)
`ing a multi-layered structure.
`
`4
`The third problem relates to coverage of a film formed by
`sputtering.
`In general, when a metal film or a metal nitride film is
`formed by sputtering, a metal target is sputtered by argon
`plasma generated by virtue of rotational magnetic field and
`application of DC bias, and resultingly, a metal film or a
`metal nitride film is deposited on a substrate located in
`facing relation to the metal target.
`In sputtering, a pressure at which a metal target is sput(cid:173)
`tered is low, specifically, equal to 1 Pa or smaller. Since
`metal particles sputtered by argon plasma are radiated ran(cid:173)
`domly to a surface of a substrate, for instance, if the
`substrate is formed at a surface thereof with a deep recess or
`hole, it would almost impossible to deposit a metal film such
`that such a recess or hole is completely covered with the
`metal film.
`In addition, since a sputtering pressure is low, argon
`plasma could have a low plasma density, and hence, there
`cannot be expected re-sputtering effect in which a metal film
`20 deposited onto a surface of a substrate is sputtered by argon
`plasma.
`In order to enhance coverage of a metal film, there has
`been suggested collimate sputtering in which a metal plate
`formed with a lot of through-holes is located between a
`sputtering target and a substrate, and metal particles are
`caused to pass through the through-holes to thereby uniform
`direction of metal particles. In accordance with the collimate
`sputtering, it is possible to deposit a metal film on a bottom
`of a recess formed at a surface of a substrate, but it is not
`possible to deposit a metal film onto an inner sidewall of the
`recess.
`The fourth problem is that a crystalline metal film having
`high adhesion with a copper film tends to react with atmo(cid:173)
`sphere to thereby a reaction layer at a surface thereof.
`Such a reaction layer would much deteriorate adhesion of
`a metal film with a copper film.
`The fifth problem is a copper oxide film is adhered again
`to a recess or hole.
`An oxide film formed on a surface of an underlying wiring
`metal film is removed by argon plasma prior to deposition of
`a diffusion-barrier film by sputtering. When an underlying
`wiring layer is composed of copper, a copper oxide film is
`scattered by argon sputtering, and as a result, the thus
`scattered copper oxide is adhered again to a recess or hole
`45 formed at a surface of an insulating film.
`The sixth problem is that when a copper film is formed on
`a tantalum film and an amorphous TaN film by CVD,
`adhesion between the copper film and a diffusion-barrier
`film is deteriorated.
`
`SUMMARY OF THE INVENTION
`In view of the above-mentioned problems in a conven(cid:173)
`tional diffusion-barrier film, it is an object of the present
`invention to provide a diffusion-barrier film having both a
`55 diffusion-barrier characteristic of preventing copper from
`being diffused into a semiconductor device and high adhe(cid:173)
`sion between a copper film and an interlayer insulating film.
`It is also an object of the present invention to provide a
`multi-layered wiring structure including the above(cid:173)
`mentioned diffusion-barrier film.
`Another object of the present invention is to provide a
`method of fabricating such the above-mentioned diffusion(cid:173)
`barrier film.
`A further object of the present invention is to provide a
`method of fabricating a multi-layered copper wiring layer in
`which copper is buried above the above-mentioned
`diffusion-barrier film.
`
`Page 23 of 31
`
`
`
`US 6,538,324 Bl
`
`5
`
`5
`In one aspect of the present invention, there is provided a
`barrier film preventing diffusion of copper from a copper
`wiring layer formed on a semiconductor substrate, including
`a multi-layered structure of first and second films, the first
`film being composed of crystalline metal containing nitro(cid:173)
`gen therein, the second film being composed of amorphous
`metal nitride, the barrier film being constituted of common
`metal atomic species.
`It is preferable that the first film is formed on the second
`film.
`It is preferable that the second film has a thickness in the
`range of 80 angstroms to 150 angstroms both inclusive.
`It is preferable that the first film has a thickness in the
`range of 60 angstroms to 300 angstroms both inclusive.
`In another aspect of the present invention, there is pro(cid:173)
`vided a multi-layered wiring structure including a barrier
`film which prevents diffusion of copper from a copper
`wiring layer formed on a semiconductor substrate, the
`barrier film having a multi-layered structure of first and
`second films, the first film being composed of crystalline
`metal containing nitrogen therein, the second film being
`composed of amorphous metal nitride, the barrier film being
`constituted of common metal atomic species.
`It is preferable that the barrier film covers a recess and a 25
`hole formed throughout an insulating film formed on an
`underlying wiring layer.
`It is preferable that the multi-layered wiring structure
`further includes a copper film formed on the first film.
`In still another aspect of the present invention, there is 30
`provided a method of forming a diffusion-barrier film by
`sputtering, including the steps of (a) preparing gas contain(cid:173)
`ing nitrogen therein, and (b) varying only power of an
`electric power source for generating plasma to thereby
`successively form a diffusion-barrier film having a multi- 35
`layered structure of first and second films, the first film being
`composed of crystalline metal containing nitrogen therein,
`the second film being composed of amorphous metal nitride,
`the barrier film being constituted of metal atomic species of
`sputter target.
`It is preferable that the gas containing nitrogen therein has
`a pressure equal to or greater than 5 Pa.
`It is preferable that the gas contains nitrogen at 10 volume
`%or smaller.
`It is preferable that the metal atomic species of sputter
`target is one of tantalum, tungsten, titanium, molybdenum
`and niobium alone or in combination.
`It is preferable that the second film has a thickness in the
`range of 80 angstroms to 150 angstroms both inclusive.
`It is preferable that the first film has a thickness in the
`range of 60 angstroms to 300 angstroms both inclusive.
`There is further provided a method of forming a diffusion(cid:173)
`barrier film by RF magnetron sputtering making use of
`rotational magnetic field and RF power, including the steps 55
`of (a) preparing gas containing nitrogen therein, and (b)
`varying the RF power to thereby successively form a
`diffusion-barrier film having a multi-layered structure of first
`and second films, the first film being composed of crystalline
`metal containing nitrogen therein, the second film being 60
`composed of amorphous metal nitride, the barrier film being
`constituted of metal atomic species of sputter target.
`There is still further provided a method of forming a
`diffusion-barrier film by RF magnetron sputtering, including
`the steps of (a) setting an electric power source for genera- 65
`tion plasma to generate power having a first value, to thereby
`a first film, with a concentration of nitrogen in plasma gas
`
`6
`being kept at a constant, and (b) setting the electric power
`source to generate power having a second value greater than
`the first value at the moment when the first film is formed by
`a predetermined thickness, to thereby form a second film on
`the first film.
`It is preferable that the first film is composed of amor(cid:173)
`phous metal nitride, and the second film is composed of
`crystalline metal containing nitrogen therein.
`There is yet further provided a method of forming a
`10 copper wiring film, including the steps of (a) radiating
`plasma of argon containing hydrogen therein, to a recess or
`hole formed at an insulating film formed on a semiconductor
`substrate, (b) forming a diffusion-barrier film to cover the
`recess or hole therewith without exposing to atmosphere, the
`15 diffusion-barrier film having a multi-layered structure of first
`and second films, the first film being composed of crystalline
`metal containing nitrogen therein, the second film being
`composed of amorphous metal nitride, and (c) forming a
`copper film on the diffusion-barrier film without exposing to
`20 atmosphere.
`It is preferable that the diffusion-barrier film is formed by
`sputtering.
`It is preferable that the copper film is formed in vacuum.
`It is preferable that the copper film is formed by thermal
`chemical vapor deposition in which thermal dismutation in
`a complex of organic metal is utilized.
`It is preferable that the copper film is formed by sputtering
`in which copper target is used.
`The advantages obtained by the aforementioned present
`invention will be described hereinbelow.
`In the diffusion-barrier film in accordance with the present
`invention, a copper film makes direct contact with a crys(cid:173)
`talline metal film containing nitrogen therein, ensuring high
`adhesion therebetween and high crystallinity of a copper
`film.
`In addition, since the metal film contains nitrogen therein,
`copper diffusion into a semiconductor device can be pre-
`40 vented more effectively than a metal film having pure
`crystals.
`In the diffusion-barrier film in accordance with the present
`invention, an amorphous metal film containing nitrogen
`therein lies under a crystalline metal film containing nitro-
`45 gen therein. Hence, it is possible to effectively prevent
`copper diffusion, and to ensure high adhesion with an
`underlying insulating film such as a silicon dioxide film.
`That is, by forming a copper wiring layer on the diffusion(cid:173)
`barrier film in accordance with the present invention, it is
`50 possible to not only ensure high crystallinity and high
`adhesion of a copper wiring layer, but also to prevent copper
`diffusion.
`The method in accordance with the present invention
`makes it possible to successively form a diffusion-barrier
`film having a multi-layered structure of first and second
`films, by varying only power of an electric power source for
`generating plasma in sputtering in which gas containing
`nitrogen therein is employed. Herein, the first film is com(cid:173)
`posed of crystalline metal containing nitrogen therein, and
`the second film is composed of amorphous metal nitride.
`The barrier film is constituted of metal atomic species of
`sputter target.
`Specifically, an electric power source for generating
`plasma is first set to generate relatively low power with a
`concentration of nitrogen in plasma gas being kept constant.
`A film is formed in such a condition. Target metal makes
`sufficient reaction with nitrogen, and resultingly, an amor-
`
`Page 24 of 31
`
`
`
`US 6,538,324 Bl
`
`10
`
`7
`phous metal nitride film is formed. Immediately after the
`formation of the amorphous metal nitride film, the electric
`power source is set to generate relatively high power to
`thereby form a film without allowing sufficient time for
`reaction between nitrogen and target metal. As a result, there 5
`is obtained a crystalline metal film containing nitrogen
`therein.
`Thus, it is possible to successively form a diffusion(cid:173)
`barrier film in the same chamber, wherein the diffusion(cid:173)
`barrier film has a multi-layered structure including a crys(cid:173)
`talline metal film containing nitrogen therein and an
`amorphous metal nitride film.
`The method of fabricating a diffusion-barrier film
`employs RF magnetron sputtering in which rotational mag(cid:173)
`netic field and RF power are utilized. Since the method 15
`makes it possible to carry out sputtering where a nitrogen(cid:173)
`containing gas has a pressure equal to or greater than 5 Pa,
`plasma density of argon which is a main constituent of
`sputtering gas can be enhanced, and thus, there can be
`obtained coverage for entirely covering a recess or hole 20
`formed at a surface of a substrate, with the diffusion-barrier
`film.
`The method of fabricating a diffusion-barrier film, in
`accordance with the present invention, includes the step of
`radiating plasma of argon containing hydrogen therein, to a 25
`recess or hole formed at an insulating film formed on a
`semiconductor substrate. This step reduces a copper oxide
`film formed on a surface of an underlying copper wiring
`layer, to thereby turn copper oxide back to copper, ensuring
`remarkable reduction in re-sputtering of a copper oxide film 30
`to a surface of a recess or hole formed at a surface of an
`insulating film.
`Then, a diffusion-barrier film is formed to cover the recess
`or hole therewith without exposing to atmosphere, wherein 35
`the diffusion-barrier film has a multi-layered structure of
`first and second films, the first film being composed of
`crystalline metal containing nitrogen therein, the second film
`being composed of amorphous metal nitride. Then, a thin
`copper film is formed on the diffusion-barrier film in
`vacuum. As a result, there is obtained a multi-layered
`structure comprised of the diffusion-barrier film and the
`copper wiring film without a