llllllllllllllllllllllIlllllllllllllllllllIllllllllllllllllllllllllllllllll
`
`USOOS780908A
`
`United States Patent
`
`[191
`
`Sekiguchi et al.
`
`[11] Patent Number:
`5,780,908
`[45] Date of Patent: Jul. 14, 1998
`
`
`
`
`
`2577740
`5/1995 Thomas .
`5,414,301
`257/770
`8/1995 Nishitsuji
`5,440,174
`257F751
`........
`5,561,326 10/1996 Ito et a1.
`. 257/924 X
`5,589,712 12/1996 Kawashima et al.
`2571751
`5,592,024
`1/1997 Aoyamo et a].
`................... 257/751 X
`5,623,157
`4/1997 Miyazaki et a].
`FOREIGN PATENT DOCUMENTS
`
`363216334 A 9/1988
`406005604 A
`1/1994
`
`Japan ..................................... 257/751
`Japan ..................................... 257/751
`
`Primary Examiner—William Mintel
`Attorney Agent, or Firm—McDerrnott. Will & Emery
`[57]
`ABSTRACT
`
`Through exposure of the top surface of a tungsten film to
`plasma of a gas including nitrogen at a temperature of 550°
`C. or less. a tungsten nitride layer having a structure in
`which nitrogen atoms and tungsten atoms are bonded is
`formed in an area in the vicinity of the surface of the
`tungsten film. Then, an aluminum alloy film is deposited on
`the tungsten film, thereby forming a metallic interconnec-
`tion. Since the nitrogen atoms and the tungsten atoms are
`bonded in the tungsten nitride layer formed by such plasma
`nitridation. the tungsten nitric layer not only has a good
`barrier function to prevent the diffusion of other metal atoms
`but also can be formed in a small thiclmess. Accordingly.
`formation of an alloy layer with a high resistance otherwise
`caused due to counter diffusion during an annealing process
`and a junction leakage can be avoided.
`
`8 Claims, 14 Drawing Sheets
`
`[54] SEMICONDUCTOR APPARATUS WITH
`TUNGSTEIN NITRIDE
`
`[75]
`
`Kyoto; Michinari
`Inventors: Mitsuru
`Yamanaka. Osaka. both of Japan
`
`[73] Assignee: Matsushita Electric Industrial Co.,
`Ltd.. Osaka. Japan
`
`[21] Appl. No.: 751,810
`
`[22] Filed:
`
`Nov. 19, 1996
`
`Related US. Application Data
`
`[62] Division of Ser. No. 646,535, May 8, 1996.
`
`Foreign Application Priority Data
`[30]
`May 9, 1995
`[JP]
`Japan .................................... 7-110433
`Aug. 3, 1995
`[JP]
`Japan .................................... 7-198502
`
`Int. Cl.6 ..................................................... H01L 23/02
`[51]
`[52] US. Cl.
`.......................... 757/383; 257/412; 257/751;
`257/763; 257/924
`[58] Field of Search ..................................... 257/924. 751.
`257/412. 382. 383. 763. 767. 770
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,829,363
`5,350,711
`
`........................... 357/71
`5/1989 Thomas et al.
`9/1994 Hall
`......................................... 437/192
`
`
`
`30
`
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`IPR2016-01249 & IPR2016-01264
`
`Page 1 of 24
`
`

`

`US. Patent
`
`Jul. 14, 1998
`
`Sheet 1 of 14
`
`5,780,908
`
`TITANIUM/TITANIUM
`
`3b TUNGSTEN FILM
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`
`Page 2 0f 24
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`Page 2 of 24
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`

`

`
`
`US. Patent
`
`Jul. 14, 1998
`
`Sheet 2 of 14
`
`5,780,908
`
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`Page 3 0f 24
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`Page 3 of 24
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`

`

`US. Patent
`
`Jul. 14, 1998
`
`‘ Sheet 3 of 14
`
`5,780,908
`
`CONTACT HOLE
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`7 TUNGSTEN FILM
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`
`Page 4 0f 24
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`Page 4 of 24
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`

`

`
`
`US. Patent
`
`Jul. 14, 1998
`
`Sheet 4 of 14
`
`5,780,908
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`Page 5 of 24
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`

`

`US. Patent
`
`Jul. 14,1998
`
`Sheet 5 of 14
`
`5,780,908
`
`GATE ELECTRODE
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`Page 6 of 24
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`

`

`US. Patent
`
`Jul. 14, 1998
`
`Sheet 6 of 14
`
`5,780,908
`
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`Page 7 of 24
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`

`

`V US. Patent
`
`Jul. 14, 1998
`
`Sheet 7 of 14
`
`-
`
`5,780,908
`
`Fig. 8 (a)
`
`+AFTER ANNEALING AT 450°C FOR 30min.
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`Page 8 of 24
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`Page 11 of 24
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`

`

`US. Patent
`
`Jul. 14, 1998
`
`Sheet 11 of 14
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`5,780,908
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`Page 12 0f 24
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`Page 12 of 24
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`

`

`
`
`US. Patent
`
`Jul. 14, 1998
`
`Sheet 12 0f 14
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`5,780,908
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`Page 13 0f 24
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`Page 13 of 24
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`

`

`US. Patent
`
`Jul. 14, 1998
`
`Sheet 13 of 14
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`5,780,908
`
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`Page 14 of 24
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`

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`
`
`US. Patent
`
`Jul. 14, 1998
`
`Sheet 14 of 14
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`5,780,908
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`Page 15 0f 24
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`Page 15 of 24
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`

`

`1
`SEMICONDUCTOR APPARATUS WITH
`TUNGSTEIN NITRIDE
`
`5.780.908
`
`2
`
`This is a divisional of application Ser. No. 08/646535.
`filed May 8. 1996.
`BACKGROUND OF THE INVENTION
`
`The present invention relates to a semiconductor appara-
`tus comprising a refractory metal. used as interconnections
`and electrodes for the production of a VLSI. and a metallic
`interconnection formed thereon. and a production method
`for the semiconductor apparatus.
`As VLSIs have recently been developed to be more highly
`integrated and have a higher density. Al/W bilayer intercon-
`nection has been earnestly studied (for example. H;
`Yamaguchi. et al.. Proc. Int. VMIC. 393—395. 1993). In the
`formation of metallic interconnection by using the AW
`bilayer interconnection. chemical vapor deposition
`(hereinafter referred to as the CVD). which is excellent in
`the coating property. is adopted to deposit tungsten on the
`entire surface of a substrate (which process is hereinafter
`referred to as the blanket tungsten CVD). On the deposited
`tungsten is deposited an aluminum alloy film to decrease the
`resistance of the interconnection. and then. both the tungsten
`and the aluminum alloy film are made into a pattern. so as
`to form the metallic interconnection.
`Now. the conventionally proposed method of forming the
`AUW bilayer interconnection will be described referring to
`FIGS. 12(a) through 12(d).
`In the procedure shown in FIG. 12(a). a first insulating
`film 2 is deposited on a silicon substrate 1 bearing a
`semiconductor device such as a transistor. 0n the first
`insulating film 2 is deposited a titanium/titanium nitride
`bilayer film 30 as an adhesion layer for tungsten by a
`sputtering method. On the titanium/titanium nitride bilayer
`film 3a is deposited a tungsten film 3b by the blanket
`tungsten CVD. At this point. the films 3a and 3b are formed
`so as to bury a contact hole shown with broken lines in FIG.
`12(a).
`Then. as is shown in FIG. 12(b). an aluminum alloy film
`3c including silicon (approximately 1%) and copper
`(approximately 0.5%) is deposited on the tungsten film 3b
`by the sputtering method. 0n the aluminum alloy film 30 is
`deposited a titanium nitride film 3d so as to ease the
`formation of an interconnection pattern in the subsequent
`photolithography. At this point. the aluminum alloy film 3c
`functions to decrease the resistance of the interconnection.
`and the titanium nitride film 3d functions to decrease the
`reflectance thereof at a wavelength of exposing light.
`Next. as is shown in FIG. 12(c). the titanium/titanium
`nitride bilayer film 3a. the tungsten film 3b. the aluminum
`alloy film 3c and the titanium nitride film 3d are made into
`a desired pattern by the photolithography and dry etching.
`thereby forming a first metallic interconnection 3.
`Then. as is shown in FIG. 12(d). the resultant semicon-
`ductor apparatus is placed in annealing equipment 9 to be
`subjected to annealing at a temperature of 450° C. This
`annealing is conducted in order to recover a damage of
`groundwork caused by the dry etching and stabilize the
`interface between the metals. When the metals for the
`interconnection include aluminum as described above. the
`annealing is generally conducted at a temperature of
`approximately 450° C. in order to retain the thermal stability
`of aluminum. It is generally considered that a temperature of
`450° C. or more is preferred for the recovery of a dry etching
`damage and removal of water contents from the insulating
`film.
`
`5
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`10
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`15
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`35
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`45
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`50
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`Page 16 of 24
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`With regard to the contact hole for connecting upper and
`lower metallic interconnection layers. when a film is formed
`within a fine contact hole having a diameter of 0.8 pm or less
`by a conventional sputtering method. the formed film lacks
`for step coverage. resulting in insufficient reliability under
`application of a current. Therefore. it is necessary to adopt
`a method of forming a buried plug with good step coverage.
`As an example of the method of forming a buried plug.
`tungsten is deposited on the entire top surface of a semi-
`conductor substrate by the CVD. and unnecessary tungsten
`excluding that deposited within a contact hole is removed by
`etching (which process is designated as the etch back). so as
`to bury the contact hole alone in tungsten. When this method
`is adopted. an aluminum alloy film is thereafter deposited on
`the buried plug and an interlayer insulating film. and the
`aluminum alloy film is made into a pattern by the photoli-
`thography so as to form a metallic interconnection. In this
`case. the tungsten is in contact with the aluminum alloy on
`the contact hole.
`
`Now. procedures for burying a via in a metal by a
`conventional buried plug method will be described referring
`to FIGS. 13(0) through 13(d).
`'
`As is shown in FIG. 13(a). a first insulating film 2 and a
`first metallic interconnection 3 are formed on a silicon
`substrate 1 bearing a semiconductor device such as a tran-
`sistor. On the first metallic interconnection 3 is formed a
`second insulating film 4 of a silicon oxide film by. for
`example. plasma CVD. Then. a contact hole 5 is formed at
`a desired position on the second insulating film 4 by the dry
`etching so as to reach the first metallic interconnection 3.
`Next. a titanium/titanium nitride bilayer film 6 serving as
`an adhesion layer for tungsten is deposited within the
`contact hole 5 and on the second insulating film 4 by the
`sputtering method. 0n the titanium/titanium nitride bilayer
`film 6 is deposited a tungsten film 7 by the blanket tungsten
`CVD.
`Then as is shown in FIG. 13(b). the tungsten film 7 and
`the titanium/titanium nitride bilayer film 6 on the second
`insulating film 4 are subjected to the etch back by the dry
`etching. so as to have the tungsten film 7 and the titanium/
`titanium nitride bilayer film 6 remained within the contact
`hole 5 alone. Thereafter. an aluminum alloy film 8a includ-
`ing silicon (approximately 1%) and copper (approximately
`0.5%) and a titanium nitride film 8b are successively depos-
`ited thereon by the sputtering method. The aluminum alloy
`film 8a functions to decrease the resistance of the
`interconnection. and the titanium nitride film 8b functions to
`decrease the reflectance thereof at a wavelength of exposing
`light.
`Next. as is shown in FIG. 13(0). the aluminum alloy film
`80 and the titanium nitride film 81) are made into a desired
`pattern by the photolithography and the dry etching. thereby
`forming a second metallic interconnection 8.
`Then. as is shown in FIG. 13(d). the resultant semicon-
`ductor apparatus is placed in annealing equipment 9. so as
`to be subjected to annealing in the same manner as described
`referring to FIG. 12(d).
`Furthermore. for the purpose of decreasing a sheet resis-
`tance of a source/drain region and a gate electrode of a MOS
`semiconductor apparatus to attain a higher operation speed.
`selective formation of a tungsten film on the source/drain
`region and the gate electrode. that is. so-called tungsten
`adhesion technique. has recently been proposed (for
`example. M. Sekine. et al.. Tech. Dig. IEDM. 493-496.
`1994). In this technique. when a metach interconnection of
`an aluminum alloy film is formed within a contact hole. the
`tungsten is in contact with the aluminum alloy below the
`contact hole.
`
`Page 16 of 24
`
`

`

`5,780,908
`
`3
`Now. the procedures of the conventionally proposed tung—
`sten adhesion technique will be described referring to FIGS.
`14(a) through 14(a').
`First. as is shown in FIG. 14(a). a source/drain region 12
`and a gate electrode 13 made of polycrystal silicon of a MOS
`semiconductor apparatus are formed on a silicon substrate 1.
`and then. a tungsten film 7 is selectively formed on the gate
`electrode 13 and the source/drain region 12 by the CVD.
`Next. as is shown in FIG. 14(b). a first insulating film 2
`is formed on the resultant semiconductor apparatus. and a
`contact hole 5 is formed in the first insulating film 2.
`Then. as is shown in FIG. 14(c). anAl alloy is deposited
`within the contact hole 5 and on the first insulating film 2 by.
`for example. sputtering the Al alloy at a temperature of 500°
`C.. and the obtained Al alloy film is made into a pattan.
`thereby forming a first metallic interconnection 3 including
`a contact member Within the contact hole 5.
`
`the semiconductor
`Then. as is shown in FIG. 14(d).
`apparatus is placed in annealing equipment 9. where anneal-
`ing is conducted in the same manner as described referring
`to FIG. 12(a').
`However. in any of the procedures shown in FIGS. 12
`through 14. there arise common problems as follows:
`It has been found that. in the annealing process shown in
`FIGS. 12(d). 13(d) and 14(d). counter difiusion of tungsten
`and aluminum causes a reaction between the tungsten and
`the aluminum.- so as to form an alloy of tungsten and
`aluminum (such as WAIR). Since WAl12 has a high
`resistance.
`the resistance of the interconnection can be
`undesirably increased and heat caused by a current flowing
`through the interconnection can disadvantageously discon-
`nect the interconnection (for example. H. Yamaguchi. et al..
`Proc. Int. VMIC. 393-395. 1993).
`Furthermore. in the case where the silicon substrate is
`present below the tungsten film as shown in FIGS. 14(a)
`through 14(d) and a PN junction is formed by diffusing an
`impurity in the silicon substrate. aluminum diffused due to
`the counter difiusion between the tungsten and the alumi-
`num can punch through the PN junction. In such a case. a
`junction leakage can be undesirably caused.
`These problems of the interconnection resistance and the
`junction leakage can similarly arise in adopting selective
`tungsten CVD in which tungsten is selectively deposited in
`a via or contact by the CVD.
`In order to avoid the formation of the alloy layer of
`WAllz. means for preventing the aluminum from being
`directly in contact with the tungsten is generally provided.
`For example. between the aluminum alloy film and the
`tungsten film. a titanium nitride film is interposed as a
`diffusion preventing film However. the titanium nitride film
`is good at working as a barrier layer but has the following
`problems: The titanium nitride film is composed of needle-
`like crystals. In order to give the barrier function. it is
`necessary to oxidize the surface to stuff oxygen betwoen the
`crystals. Oxidation is conducted by exposing the titanium
`nitride film to air. and hence. it is required to change the
`atmosphere in the chamber from substantial vacuum to air
`for the oxidation and to change it again to the substantial
`vacuum after the oxidation. Furthermore. since the number
`of film formation is increased. the production cost can be
`increased and the yield can be decreased due to generation
`of particles.
`On the other hand. it is disclosed that a tungsten nitride
`layer with a thickness of approximately 3 nm can be formed
`by exposing a tungsten film to an NH3 gas at a high
`
`4
`temperature of 550° C. for a long period of time (Japanese
`Laid-Open Patent Publication No. 63-84154). In this
`method. however. the speed of forming the tungsten nitride
`layer is as low as 3 nm/60 min. In addition. an impurity in
`a source/drain region is absorbed by the tungsten through the
`annealing at a high temperature for a long period of time. so
`as to cause a reaction between the tungsten film and the
`silicon substrate. As a result. a junction leakage can be
`caused.
`thereby degrading the saturation current of the
`transistor.
`
`Furthermore. as is disclosed in Japanese Laid-Open
`Patent Publication No. 7—231037. formation of a tungsten
`nitride film on a tungsten film by a reactive sputtering
`method is also known. Howevar. according to the descrip-
`tion of Japanese Laid-Open Patent Publication No.
`7—231037. when the tungsten nitride layer formed at 500° C.
`in an atmosphere of the Nl-I3 gas. the composition of the
`nitrided layer is not homogenous. and the resistance value is
`largely increased after the annealing. This means that it is
`diflicult to form a nitrided layer having a barrier function
`merely by exposing a tungsten film to the NH3 gas at a
`temperature lower than 500° C.
`On the other hand. although the tungsten nitride film
`formed by the reactive sputtering method has a sufficient
`function as a barrier layer. the resistance value of the entire
`bilayer film is large. and the resistance obtained when a
`current is allowed to flow in the vertical direction to the
`tungsten nitride layer. that is. the contact resistance of a
`buried layer in a contact hole. is large. and therefore. it is
`difficult to form a brn'ied layer having small resistance. This
`is because. in addition to the high resistance of the tungsten
`nitride film itself. the tungsten nitride layer formed by the
`reactive sputtering method has a thickness of 20 through 200
`am because it must be continuously formed. and it is difficult
`to attain a small thickness of 20 nm or less.
`
`SUMMARY OF THE INVENTION
`
`The present inventors have made it clear that the structure
`of a tungsten nitride layer largely aflects the function thereof
`as a barrier layer. and as a result. it has been found that a
`tungsten nitride layer formed via atomic bond between
`nitrogen atoms and tungsten atoms exhibits a good barrier
`function. The object of the invention is providing a semi-
`conductor apparatus and a production method for the same
`in which the formation of a compound with a high resistance
`and the occurrence of a junction leakage are prevented by
`using means for forming a tungsten nitride layer in a
`thickness as small as possible so as to have a structure in
`which the nitrogen atoms and the tungsten atoms are
`bonded.
`
`The semiconductor apparatus of this invention comprises
`a semiconductor substrate; a conductive layer formed on a
`part of the semiconductor substrate; a refractory metal film
`formed on the conductive layer; a nitrided metal layer
`formed in an area in the vicinity of a top surface of the
`refractory metal film and having a structure in which nitro-
`gen atoms and refractory metal atoms are bonded; and a
`metallic interconnection formed on the refractory metal film
`with the nitrided metal layer interposed therebctween and
`made of a metal material reactive with the refractory metal.
`In one aspect. the conductive layer is an active area
`formed by introducing an impurity into the semiconductor
`substrate. the semiconductor apparatus is further provided
`with an insulating film formed on the active area and a
`contact hole formed in a part of the insulating film so as to
`reach the active area. and the refractory metal film is buried
`in the contact hole
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`5,780,908
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`5
`In another aspect. the semiconductor apparatus further
`comprises a gate electrode formedon the semiconductor
`substrate. The conductive layer is a source/drain region
`formed by introducing an impurity into the semiconductor
`substrate so as to be positioned on both sides of the gate
`electrode. and the refractory metal film can be formed on the
`gate electrode and the source/drain region.
`Owing to the aforementioned configuration. the nitrided
`metal layer. in which the nitrogen atoms and the tungsten
`atoms are bonded. is excellent in a function to prevent the
`difi‘usion of the metal atoms. namely has a good barrier
`function. Therefore.
`in the annealing process during the
`production of the semiconductor apparatus.
`the counter
`difl‘usion of the composing atoms between the refractory
`metal film and the metallic interconnection can be pre-
`vented. As a result. the resistances of an interconnection. a
`plug layer and the like can be prevented from being
`increased due to the counter diffusion of the composing
`atoms between the refractory metal film and the metallic
`interconnection. and a junction leakage is prevented from
`being caused by metal invasion of the semiconductor sub-
`strate.
`
`Preferably. the nitrided metal layer has a thickness of 10
`nm or less.
`
`As a result. the nitrided metal layer having a high resis-
`tance value can be very thin. and hence. the resistances of
`the intaconnection. the plug layer and the like can be made
`as small as possible.
`Preferably. the content of nitrogen in a part of the nitrided
`metal layer is in a range where an amorphous nitrided metal
`layer is formed in a part of the nitrided metal layer.
`As a result. the function to prevent the counter diffusion
`of the composing atoms between the refractory metal film
`and the metallic interconnection can be further enhanced.
`
`Preferably. the content of nitrogen in a part of the nitrided
`metal
`layer is larger than a stoichiometric ratio of the
`nitriding metal.
`As a result. the barrier function of the nilrided metal layer
`can be more remarkably exhibited.
`The nitrided metal layer can be formed so as to have a
`substantially uniform thickness from the top surface of the
`refractory metal film.
`As a result. even through the nitrided metal layer has a
`small thickness. the barrier function of the nitrided metal
`layer can be securely exhibited in the entire boundary
`between the refractory metal film and the metallic intercon-
`nection.
`
`The nitrided metal layer can include oxygen.
`As a result. the barrier function of the nitrided metal layer
`can be further enhanced.
`
`The refractory metal can be tungsten.
`As a result. while a tungsten film having good character-
`istics that it does not harmfully affect a semiconductor can
`be used as a buried plug layer and an electrode. the forma-
`tion of an alloy layer between the tungsten film and the
`metallic interconnection can be securely avoided.
`The metallic interconnection can be made of a metal
`material including aluminum.
`.
`As a result. even when the metallic interconnection
`includes aluminum. which has a low resistance but can form
`an alloy layer having a high resistance together with the
`refractory metal through the annealing process and can
`invade the semiconductor substrate so as to cause ajunction.
`leakage.
`the increase of
`the resistances of the
`
`6
`interconnection. the plug layer and the like as well as the
`increase of the junction leakage can be securely prevented in
`the semiconductor apparatus.
`The first production method for a semiconductor appara-
`tus of this invention comprises a first step of forming a
`conductive layer on a part of a semiconductor substrate; a
`second step of depositing a refractory metal film on the
`conductive layer; a third step of emitting nitrogen ions onto
`a surface of the refractory metal film so as to form a nitrided
`metal layer. which has a struaure in which nitrogen atoms
`and refractory metal atoms are bonded. in an area in the
`vicinity of the surface of the refractory metal film; a fourth
`step of depositing a metal film for interconnection on the
`refractory metal film after the third step; and a fifth step of
`forming a metallic interconnection by patterning the metal
`film for interconnection.
`
`the production method can further
`In one aspect.
`comprise. after the first step and before the second step. a
`step of forming an insulating film on the conductive layer
`and a step of forming a contact hole in a part of the insulating
`film so as to reach the conductive layer. In the second step.
`the refractory metal film can be formed within the contact
`hole.
`
`In another aspect. the production method can furtha
`comprise. before the first step. a step of forming a gate
`electrode on the semiconductor substrate. In the first step. a
`source/drain region serving as the conductive layer can be
`formed by introducing an impurity into the semiconductor
`substrate so as to be positioned on both sides of the gate
`electrode. and in the second step. the refractory metal film
`can be formed on the gate electrode and the sourceJdrain
`region.
`According to this method when nitrogen ions in the
`plasmatic state enter the area in the vicinity of the top
`surface of the refractory metal film in the second step. the
`nitrogen atoms are substituted with the refractory metal
`atoms. thereby forming the nitrided metal layer having a
`structure in which the nitrogen atoms and the refractory
`metal atoms are bonded. Accordingly. even when the anneal—
`ing process is thereafter conducted for the recovery of a
`damage caused by another process and for the stabilization
`of the films. the alloy layer having a high resistance can be
`prevented from being formed by the counter diffusion of the
`composing metals between the refractory metal film and the
`metallic interconnection. and the increase of a junction
`leakage can be avoided. As a result.
`it is possible to
`manufacture a semiconductor apparatus having excellent
`characteristics in which the resistances of an
`interconnection. the plug layer and the like are small.
`The third step can be conducted by generating plasma in
`an atmosphere of a N2 gas.
`As a result. by using the N2 gas. which conventionally has
`a difficulty in nitridation through annealing alone.
`the
`nitrided metal layer can be formed in a neutral atmosphere
`without harrnfully affecting the characteristics of the semi-
`conductor apparatus.
`The third step can be conducted by generating plasma in
`an atmosphere of an NH3 gas at a temperature of 550° C. or
`less.
`'
`The third step can be conducted by emitting at least one
`of UV and ionizing radiation in an atmosphere of a gas
`including nitrogen atoms onto the refractory metal fihn at a
`temperature of 550° C. or less.
`The third step can be conducted by emitting an ion beam
`including nitrogen atoms onto the refractory metal film at a
`temperature of 550° C. or less.
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`5,780,908
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`7
`In any of these methods. the nitrided metal layer can be
`formed so as to have a structure in which the nitrogen atoms
`and the refractory metal atoms are bonded. similarly to the
`plasma nitridation.
`The third step can be conducted by CVD.
`According to this method. even on the refractory metal
`film formed by the CVD and having rough morphology. the
`nilrided metal layer can be formed in a uniform and small
`thickness.
`
`Preferably. the third step is conducted by using a plasma
`generation apparatus in which a positive electrode and a
`negative electrode are disposed parallel to each other and
`applying a negative potential to the semiconductor substrate.
`Preferably. the third step is conducted with a potential
`difference between the positive electrode and the negative
`electrode retaining at 100 V or more.
`As a result. the ratio of the atomic bond between the
`nitrogen atoms and the refractory metal atoms can be
`increased.
`
`The second production method for a semiconductor appa-
`ratus of this invention comprises a first step of forming a
`conductive layer on a part of a semiconductor substrate; a
`second step of depositing a tungsten film on the conductive
`layer; a third step of depositing a metal film for intercon—
`nection made of a metal material including aluminum on the
`tungsten film; a fourth step of forming a metallic intercon-
`nection by patterning the metal film for interconnection; and
`a fifth step of conducting annealing at a temperature ranging
`between 400° C. and 430° C. after the fotn1h step. so as to
`recover a damage caused in the metal film for interconnec-
`tion in the fourth sep.
`Also according to this method. the alloy layer having a
`high resistance can be prevented from being formed by the
`counter diifusion between the tungsten and the aluminum
`through the annealing process for the recovery of the dam—
`age.
`
`BRIEF DESCRIFI'ION OF THE DRAWINGS
`
`FIG. 1(a) through 1(e) are sectional views for showing
`production procedures for a semiconductor apparatus of a
`first embodiment;
`FIG. 2 is a sectional view of the semiconductor apparatus
`of the first embodiment;
`FIGS. 3(a) through 3(a) are sectional views for showing
`production procedures for a semiconductor apparatus of a
`second embodiment;
`FIG. 4 is a sectional view of the semiconductor apparatus
`of the second embodiment;
`FIGS. 5(a) through 5(e) are sectional views for showing
`production procedures for a semiconductor apparatus of a
`third embodiment;
`FIG. 6 is a sectional view of the semiconductor apparatus
`of the third embodiment;
`FIG. 7 is a sectional View of a semiconductor apparatus of
`a fourth embodiment;
`FIGS. 8(a) and 8(b) are characteristic diagrams showing
`variation in an interconnection resistance against a line
`width in samples with and without a N2 plasma treatment;
`FIGS. 9(a) and 9(b) are diagrams showing data of X-ray
`difi‘raction in samples with and without
`the N2 plasma
`treatment;
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`FIG. 10 is a diagram showing the results of an XPS
`analysis in the area in the vicinity of the surface of the
`tungsten film in the semiconductor apparatus of the inven-
`tion;
`
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`8
`FIG. 11 is a diagram showing the results of an AES depth
`analysis in the area in the vicinity of the surface of the
`tungsten film in the semiconductor apparatus of the inven-
`tion;
`FIGS. 12(a) through 12(d) are sectional views for show-
`ing production procedures for a conventional semiconductor
`apparatus including an Al/W bilayer interconnection;
`FIGS. 13(a) through 13(d) are sectional views for show—
`ing production procedures for another conventional semi—
`conductor apparatus including a buried plug;
`FIGS. 14(a) through 14(d) are sectional views for show-
`ing production procedures for a still another conventional
`semiconductor apparatus utilizing tungsten adhesion tech-
`nique; and
`FIG. 15 is a TEM microphotograph of an area in the
`vicinity of the boundary between a tungsten film and an
`aluminum alloy film in the semiconductor apparatus of the
`first embodiment.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`(Embodiment 1)
`A production method for a semiconductor apparatus
`according to the first embodiment will now be described
`refen‘ing to FIGS. 1(a) through 1(a).
`In the procedure shown in FIG. 1(a). a first insulating film
`2 of a silicon oxide film is depos