Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 1 of 32 PageID #: 1184
`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 1 of 32 PageID #: 1184
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`EXHIBIT A
`EXHIBIT A
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`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 2 of 32 PageID #: 1185
`
`(12) United States Patent
`Tagami et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,538,324 B1
`Mar. 25, 2003
`
`US006538324B1
`
`(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
`
`(51) Int. Cl.7 ........................ .. H01L 23/48; H01L 23/52
`(52) US. 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 et al. ............... .. 257/751
`5,858,873 A * 1/1999 Vitkavage et a1. ........ .. 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
`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
`chemical Society, Jul. 1998, pp. 2538—2545.
`D. Denning, et al., An Inlaid CVD Cu Based Integration for
`Sub 0.25pm Technology, 1998 Symposium on VLSI Tech
`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 ?lm preventing diffusion of
`copper from a copper Wiring layer formed on a semicon
`ductor substrate. The barrier ?lm has a multi-layered struc
`ture of ?rst and second ?lms Wherein the ?rst ?lm is
`composed of crystalline metal containing nitrogen therein,
`and the second ?lm is composed of amorphous metal nitride.
`The barrier ?lm is constituted of common metal atomic
`species. The barrier ?lm prevents copper diffusion from a
`copper Wiring layer into a semiconductor device, and has
`suf?cient adhesion characteristic to both a copper ?lm and
`an interlayer insulating ?lm.
`
`10 Claims, 20 Drawing Sheets
`
`/ :2
`
`\
`
`\
`
`1 2\b/\\
`
`\ \
`
`\§$/
`
`I
`
`/
`‘
`
`\
`
`\
`\ /
`
`\
`
`w/ m/ w
`\\\\\b
`/\\ \\\\ /
`/ /) /
`/\/ /
`44
`44
`>
`<
`
`12a
`
`11
`
`“>
`<
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 3 of 32 PageID #: 1186
`
`U.S. Patent
`
`Mar. 25, 2003
`
`Sheet 1 0f 20
`
`US 6,538,324 B1
`
`9
`
`GMA
`
`4 9
`
`FIG. 1
`(PriorArt)
`
`FIG. 2
`(PriorArt)
`
`Y:
`
`7
`
`5 }
`
`<>
`
`A
`
`m
`
`q | M: “ l? '
`r. 1%“
`4 ? 5a
`2! =6? #9 -
`9V
`| x)“
`
`9
`
`4 <3
`
`<>
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 4 of 32 PageID #: 1187
`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 4 of 32 PageID #: 1187
`
`US. Patent
`
`Mar. 25, 2003
`
`Sheet 2 0f 20
`
`US 6,538,324 B1
`
`7
`
`V
`
`w‘‘% //A
`r
`
`
` b
`
`FIG. 4A
`
`A
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 5 of 32 PageID #: 1188
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 3 0f 20
`
`US 6,538,324 B1
`
`j>17
`
`57 / ///
`
`FIG 4c
`
`y///
`
`\
`
`\
`
`/> /
`/
`44
`
`FIG. 4D
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 6 of 32 PageID #: 1189
`
`U.S. Patent
`
`Mar. 25, 2003
`
`Sheet 4 0f 20
`
`US 6,538,324 B1
`
`;
`
`
`
`BOTTOM COVERAGE (%)
`
`3O
`
`10
`
`17Pa
`
`13Pa
`
`2Pa
`4Pa
`
`4
`
`4.5
`
`5
`
`1.5
`
`2
`
`2.5
`3
`3.5
`ASPECT RATIO
`FIG. 6
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 7 of 32 PageID #: 1190
`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 7 of 32 PageID #: 1190
`
`US. Patent
`
`Mar. 25, 2003
`
`Sheet 5 0f 20
`
`US 6,538,324 B1
`
`
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 8 of 32 PageID #: 1191
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 6 0f 20
`
`US 6,538,324 B1
`
`1000 -
`
`800 -
`
`13Pa, 3kW
`
`600 -
`
`13Pa, 2kW
`
`400 _
`
`0 O 2
`
`_
`
`a, P 3 1
`
`W k 8,
`
`1O
`
`N2/(Ar+N2)|=|_0w RATE RATIO (%)
`
`FIG. 9
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 9 of 32 PageID #: 1192
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 7 0f 20
`
`US 6,538,324 B1
`
`20000
`
`
`
`A38 56:25
`
`O O 0 0 O O 0 O O 5 O 5
`
`_ _ _
`
`T3
` m.) 0 mw
`
`
`_ _
`
`25
`
`30
`
`I. \\
`
`IJ
`
`35
`26 (deg.)
`FIG. 10
`
`40
`
`45
`
`
`
`Awnuv 36:25
`
`5000
`
`4000 *
`
`3000
`
`2000 —
`
`1000 -
`
`25
`
`26 (deg.)
`FIG. 11
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 10 of 32 PageID #: 1193
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 8 0f 20
`
`US 6,538,324 B1
`
`2000
`
`I
`
`.
`
`I
`
`1500 -
`
`17
`D.
`8
`a 1000 -
`'17:
`C
`2
`E
`
`500 -
`
`Ta2N
`
`0
`25
`
`so
`
`l
`35
`26 (deg.)
`
`4o
`
`45
`
`5000
`
`I
`
`I
`
`-
`
`_
`
`_
`
`Ta2N5(113) or (041)
`
`-
`
`Ta3N5(132)
`or (042)
`
`I
`40
`
`45
`
`4000 -
`
`3 3000 -
`8
`a
`2 2000 -
`2
`s
`
`1000 ~
`
`O
`25
`
`30
`
`l
`35
`26 (deg.)
`FIG. 13
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 11 of 32 PageID #: 1194
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 9 0f 20
`
`US 6,538,324 B1
`
`300
`
`2 4|
`O O 5 5
`0 0 2
`
`P _
`_
`
`100 —
`
`50
`
`2000
`
`1500 "
`
`1000 —
`
`
`
`A38 35:25
`
`500 *
`
`Ta2N
`
`CRYSTALLINE
`O _ _[J’-Ta&TaNO1
`. o____---o
`
`10
`
`RF Power (kW)
`FIG. 1 4
`
`Ta2N
`
`25
`
`30
`
`45
`
`40
`
`35
`26 (deg.)
`FIG. 15
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 12 of 32 PageID #: 1195
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 10 0f 20
`
`US 6,538,324 B1
`
`10000
`
`|
`
`l
`
`I
`
`TaNom
`(110)
`
`8000 -
`
`I?
`g 6000 —
`3'
`'5
`5 E 4000 -
`
`2000 -
`
`O
`25
`
`_l‘
`30
`
`35
`
`20 (deg.)
`
`20000
`
`I
`
`1
`
`,
`
`15000 -
`
`17>‘
`Q.
`8
`,5‘ 10000 -
`U)
`C
`‘D
`
`E
`
`5000 -
`
`TaNO1(110)
`
`I
`
`‘
`
`*
`
`‘
`
`O
`25
`
`._L
`30
`
`6-Ta(002)
`J./\\ L
`35
`20 (deg.)
`FIG. 17
`
`40
`
`45
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 13 of 32 PageID #: 1196
`
`U.S. Patent
`
`Mar. 25, 2003
`
`Sheet 11 0f 20
`
`US 6,538,324 B1
`
`20000
`
`15000
`
`
`
`Intensity (cps)
`
`10000
`
`I
`
`5000
`
`25
`
`TaNm
`
`.Jl
`
`30
`
`35
`
`40
`
`45
`
`26 (deg.)
`
`FIG. 18
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 14 of 32 PageID #: 1197
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 12 0f 20
`
`US 6,538,324 B1
`
`3 -.
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 15 of 32 PageID #: 1198
`
`U S Patent
`
`Mar. 25,2003
`
`Sheet 13 0f 20
`
`US 6,538,324 B1
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 16 of 32 PageID #: 1199
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 14 0f 20
`
`US 6,538,324 B1
`
`FIG. 21
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 17 of 32 PageID #: 1200
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 15 0f 20
`
`US 6,538,324 B1
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 18 of 32 PageID #: 1201
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 16 0f 20
`
`US 6,538,324 B1
`
`16
`
`////
`
`//////
`
`/13,14
`
`\
`\
`/)
`44
`
`FIG. 23
`
`m,\\\ \\\\\\3
`1:
`28 26
`
`r
`
`FIG. 24
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 19 of 32 PageID #: 1202
`Case 1:16-cv-OO290-MN Document 45-1 Filed 11/22/17 Page 19 of 32 PageID #: 1202
`
`US. Patent
`
`Mar. 25, 2003
`
`Sheet 17 0f 20
`
`US 6,538,324 B1
`
`. 1
`“
`
`.
`A
`‘ Vlr'I’A 44
`
`
`A§‘\ /§!“ ’1‘
`»
`
` Q
`
`i -
`
`A
`‘1 1111111114. \§ 11111111
`
`I]; 445’ A
`
`k\\
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 20 of 32 PageID #: 1203
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 18 0f 20
`
`US 6,538,324 B1
`
`FIG. 27
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 21 of 32 PageID #: 1204
`
`U.S. Patent
`
`Mar. 25,2003
`
`Sheet 19 0f 20
`
`US 6,538,324 B1
`
`(atoms/cm 3)
`
`
`
`FLUORINE CONCENTRATION
`
`1023 -
`
`E Barrier Film
`MOCVD-Cu I
`After Annealing
`
`1021
`
`' ‘
`
`?-Ta
`
`1019 ~'
`
`,1
`‘I
`"' ‘Just After
`1017 _
`Film
`
`Deposition : Ta2N
`1
`s
`
`1015
`O
`
`.
`
`
`
`' I
`
`.
`
`I.
`I
`I
`500
`DEPTH (A)
`
`
`
`COPPER CONCENTRATION
`
`1023 _
`
`I
`
`Barrier Film
`
`21 _
`
`1 O
`
`1019
`
`(atoms/cm 3)
`
`[AL-Fa
`
`1017 _ Just A?e'r Film \
`
`\.
`
`-
`
`1015
`
`.
`
`Ta:N
`
`i
`
`.
`
`Depositiowk‘wdg
`
`-
`
`'
`
`.
`
`. alum. HI.
`1 OOO
`5 0O
`DEPTH ()3)
`FIG. 29
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 22 of 32 PageID #: 1205
`Case 1:16-cv-OO290-MN Document 45-1 Filed 11/22/17 Page 22 of 32 PageID #: 1205
`
`US. Patent
`
`Mar. 25, 2003
`
`Sheet 20 0f 20
`
`US 6,538,324 B1
`
`12b
`
`123
`
`11
`
`
`
`gal/411:" A
`
`V
`
`
`
`
`
`
`b
`
`
`54
`
`12b $7It§ V
`
`
`
`‘
`'
`h
`
`
`
`
`
`
`11
`
`12a
`
`FIG. 31
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 23 of 32 PageID #: 1206
`Case 1:16-cv-OO290-MN Document 45-1 Filed 11/22/17 Page 23 of 32 PageID #: 1206
`
`US 6,538,324 B1
`
`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
`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
`aluminum, copper is more corrosive than aluminum.
`In addition, since copper has a high diffusion rate in both
`silicon (Si) and silicon dioxide (SiOz), if copper enters
`MOSFET formed on a silicon substrate, copper would
`induce reduction in carrier lifetime.
`
`layer is
`
`it is absolutely necessary for a semiconductor
`Hence,
`device having a copper wiring layer to have a diffusion-
`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
`the same, in order to prevent copper diffusion form a copper
`wiring layer.
`For
`instance, a structure of a barrier metal
`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.
`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,
`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-
`cant does not admit that Japanese Patent Application No.
`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.
`An insulating film is formed on an underlying copper
`wiring layer. Then,
`the insulating film is formed with a
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`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
`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
`selected regions by CMP. Thus, a copper wiring layer is
`completed.
`As will be obvious to those skilled in the art, the diffusion-
`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-
`ment in crystallinity of the copper film. However, since
`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
`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-
`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
`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.
`the conventional barrier film for preventing
`However,
`copper diffusion is accompanied with the following prob-
`lems.
`
`The first problem is that it is quite difficult to make a
`diffusion-barrier film have both a characteristic of prevent-
`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-
`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
`
`

`

`Case 1:16-cv-00290-MN Document 45-1 Filed 11/22/17 Page 24 of 32 PageID #: 1207
`Case 1:16-cv-OO290-MN Document 45-1 Filed 11/22/17 Page 24 of 32 PageID #: 1207
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`US 6,538,324 B1
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`3
`a bottom of the metal film 5. The grain boundaries 7 define
`paths 8 through which copper is diffused. As a result, the
`metal film 5 has low barrier characteristic of preventing
`copper diffusion.
`As illustrated in FIG. 3, it is now assumed to form a metal
`film 5a on a semiconductor substrate 4. If the metal film 5a
`
`is composed of metals having small resistivity, such as
`tungsten (W), titanium (Ti) or tantalum (Ta), the metal film
`5 would have a polycrystal structure. As a result, the metal
`film 5a would have a pillar-like structure similarly to the
`metal film 5 illustrated in FIG. 2, and accordingly, the metal
`film 5a 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 B-Ta (002) film as
`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 5a 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
`chm, and does not have the paths through which copper is
`diffused unlike the crystalline metal film 5 illustrated in FIG.
`2. As a result, the metal film 5a would have high barrier
`characteristic of preventing copper diffusion.
`However, since a surface of the metal film 5a is amor-
`phous and hence crystal lattice is not uniformly arranged, if
`a copper film s formed on the amorphous metal film 5a by
`CVD or sputtering, copper crystallinity and adhesion to
`copper are degraded.
`to form a
`is quite difficult
`it
`As mentioned so far,
`diffusion-barrier film having a single-layered structure com-
`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
`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
`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-
`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
`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
`fabrication yield of fabricating a diffusion-barrier film hav-
`ing a multi-layered structure.
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`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-
`tered is low, specifically, equal to 1 Pa or smaller. Since
`metal particles sputtered by argon plasma are radiated ran-
`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
`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-
`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
`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-
`tional diffusion-barrier film, it is an object of the present
`invention to provide a diffusion-barrier film having both a
`diffusion-barrier characteristic of preventing copper from
`being diffused into a semiconductor device and high adhe-
`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-
`mentioned diffusion-barrier film.
`
`Another object of the present invention is to provide a
`method of fabricating such the above-mentioned diffusion-
`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.
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`US 6,538,324 B1
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`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-
`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-
`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
`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
`provided a method of forming a diffusion-barrier film by
`sputtering, including the steps of (a) preparing gas contain-
`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-
`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-
`barrier film by RF magnetron sputtering making use of
`rotational magnetic field and RF power, including the steps
`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
`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-
`tion plasma to generate power having a first value, to thereby
`a first film, with a concentration of nitrogen in plasma gas
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`
`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-
`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
`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
`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
`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-
`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-
`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-
`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-
`barrier film in accordance with the present invention, it is
`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-
`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-
`
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`US 6,538,324 B1
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`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
`is obtained a crystalline metal film containing nitrogen
`therein.
`
`is possible to successively form a diffusion-
`it
`Thus,
`barrier film in the same chamber, wherein the diffusion-
`barrier film has a multi-layered structure including a crys-
`talline metal
`film containing nitrogen therein and an
`amorphous metal nitride film.
`film
`The method of fabricating a diffusion-barrier
`employs RF magnetron sputtering in which rotational mag-
`netic field and RF power are utilized. Since the method
`makes it possible to carry out sputtering where a nitrogen-
`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
`formed at a surface of a substrate, with the diffusion-barrier
`film.
`
`in
`The method of fabricating a diffusion-barrier film,
`accordance with the present invention, includes the step of
`radiating plasma of argon containing hydrogen therein, to a
`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
`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
`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,
`