US20060086618A1

US20060086618A1 - Method and apparatus for forming interconnects

Info

Publication number: US20060086618A1
Application number: US11/254,789
Authority: US
Inventors: Akira Fukunaga; Manabu Tsujimura
Original assignee: Individual
Current assignee: Ebara Corp
Priority date: 2004-10-21
Filing date: 2005-10-21
Publication date: 2006-04-27
Also published as: JP2006120870A

Abstract

An interconnects-forming method can form a film of interconnect material, having a sufficient adhesion, by electroplating uniformly on an entire surface of a substrate and thus can form highly-reliable embedded interconnects even when the design rule is strict, and which can remove an extra interconnect material at a lower pressure. The interconnects-forming method, including: forming a conductive film on a surface of a substrate having interconnect recesses formed in an insulating film, said conductive film being insoluble in an electrolytic plating solution for the formation of a film of an interconnect material; forming a film of the interconnect material by electroplating on a surface of the conductive film serving as a seed film while filling the interconnect recesses with the interconnect material; and removing an extra interconnect material of the film formed on the conductive film, thereby forming interconnects of the interconnect material embedded in the interconnect recesses.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a method and an apparatus for forming interconnects, and more particularly to a method and an apparatus for forming interconnects which are useful for embedding a conductive material (interconnect material), such as copper or silver, into interconnect recesses provided in a surface of a substrate, such as a semiconductor wafer, to thereby form embedded interconnects, and selectively covering surfaces of the embedded interconnects with a metal film (protective film) to provide a multi-level structure.
2. Description of the Related Art
As an interconnect formation process for semiconductor devices, there is getting employed a process (so-called damascene process) in which metal (interconnect material) is embedded in interconnect recesses composed of trenches and contact holes. This process includes embedding aluminum or, recently, interconnect material (metal) such as copper or silver into interconnect recesses such as trenches or contact holes, which have previously been formed in an interlevel dielectric film, and then removing excessive metal by chemical mechanical polishing (CMP) for planarization.
In the production of such interconnects, for example, copper interconnects using copper as an interconnect material, a barrier film containing tungsten, tantalum or titanium is formed on a surface of an interlevel dielectric film for the purpose of preventing diffusion of copper into the interlevel dielectric film, and then a seed film of copper, which serves as an electric supply layer during electroplating, is formed on a surface of the barrier film by PVD or ALD. Thereafter, a copper film is formed on the entire surface of the substrate (barrier film), for example, by copper sulfate electroplating, followed by removal of extra copper and barrier films formed in the substrate surface, for example by CMP, thereby forming interconnects composed of the interconnect material embedded in interconnect recesses.
As is widely practiced, the surfaces of the thus-formed interconnects are selectively covered with a film of a cobalt alloy or a nickel alloy formed by electroless plating or with a film of a vanadium compound formed by CVD to provide a multi-level interconnect structure.

SUMMARY OF THE INVENTION

As the design rule becomes stricter, a thinner seed film is required to be formed on a surface of a barrier film. As the thickness of a seed film becomes smaller, however, it is becoming increasingly difficult to form such a thin seed film with a uniform thickness. Should a uniform seed film be formed, the seed film can be dissolved in an acidic plating solution on its immersion in the plating solution, leading to difficulty in stably forming a plated film. Therefore, in the interconnects-forming technology of the 45 nm-node or later generation, the possibility of directly forming a copper film by electroplating without forming a seed film on a surface of a barrier film is envisaged. However, when forming a copper film by electroplating directly on a conventional barrier film which is generally formed of a tungsten, tantalum or titanium-based material, because of the too high electric resistance of the barrier film, a copper film can be formed uniformly over the entire substrate surface with difficulty. Further, an oxide film can be present on a surface of a barrier film. In such a case, a sufficient adhesion between the barrier film and copper (plated film) may not be obtained.
On the other hand, the use of a low-k material for an interlevel dielectric film is contemplated in the 45 nm-node or later generation in order to improve the so-called RC delay. However, low-k materials are generally weak, and therefore it is difficult to use the conventional CMP technology as it is when employing a low-k material for an interlevel dielectric film. A CMP technique that enables a lower-pressure polishing is now in demand.
The present invention has been made in view of the above situation in the related art. It is therefore an object of the present invention to provide a method and an apparatus for forming interconnects which can form a film of interconnect material, having a sufficient adhesion, by electroplating uniformly on an entire surface of a substrate and thus can form highly-reliable embedded interconnects even when the design rule is strict, and which can remove an extra interconnect material at a lower pressure.
In order to achieve the above object, the present invention provides an interconnects-forming method, comprising: forming a conductive film on a surface of a substrate having interconnect recesses formed in an insulating film, said conductive film being insoluble in an electrolytic plating solution for the formation of a film of an interconnect material; forming a film of the interconnect material by electroplating on a surface of the conductive film serving as a seed film while filling the interconnect recesses with the interconnect material; and removing an extra interconnect material of the film formed on the conductive film, thereby forming interconnects of the interconnect material embedded in the interconnect recesses.
By using a conductive film, which is insoluble in an electrolytic plating solution for the formation of a film of an interconnect material, as a seed film in electroplating and forming a film of the interconnect material directly on the conductive film, dissolution of the conductive film in the plating solution can be avoided even when the conductive film (seed film) is thin and the film of the interconnect material can be formed after a sufficient contact between the conductive film and the plating solution. This makes it possible to form an interconnect material (plated film), having a sufficient adhesion to the conductive film, by electroplating uniformly on an entire surface of a substrate (conductive film) and thus can form highly-reliable embedded interconnects with good reproducibility.
Preferably, after the formation of the conductive film, the conductive film is subjected to pre-electroplating processing.
As the size of a substrate becomes larger and the thickness of a conductive film becomes smaller, it becomes difficult to form a conductive film as a plating base uniformly on an entire surface of a substrate. Thus, electroplating is required to be carried out uniformly on an entire surface of a non-uniform base. It will, therefore, be necessary to carryout appropriate pre-plating processing to improve the uniformity of the plating base. Examples of the pre-plating may include water-washing, a surfactant processing, etc. to uniformize wetting, chemical processing, plasma processing, etc. to remove or chemically reduce a non-uniform oxide film, and a plating seed-forming processing to apply the same material as a plated film to the substrate surface with a thickness of not more than 10 nm e.g. by plating, PVD or CVD.
Preferably, after the formation of the interconnects, the conductive film present outside the interconnect recesses is removed.
Methods for removing the conductive film on an insulating film include polishing, etching with a chemical and plasma etching. An appropriate method can be selected in consideration of the properties of the conductive film, consistency with the previous or next processing, the morphology of the surface after the removal of the conductive film, etc.
The present invention provides another interconnects-forming method, comprising: forming an adhesive film on a surface of a substrate having interconnect recesses formed in an insulating film; forming a conductive film on a surface of the adhesive film, said conductive film being insoluble in an electrolytic plating solution for the formation of a film of an interconnect material; forming a film of the interconnect material by electroplating on a surface of the conductive film serving as a seed film while filling the interconnect recesses with the interconnect material; and removing an extra interconnect material of the film formed on the conductive film, thereby forming interconnects of the interconnect material embedded in the interconnect recesses.
By forming a conductive film on a surface of an adhesive film formed on a substrate (insulating film), it becomes possible to secure with the adhesive film a sufficient adhesion between the conductive film and the insulating film (interlevel dielectric film), thus preventing a loss of reliability due to insufficient adhesion between the conductive film and the insulating film. The adhesive film can be formed by any known method such as PVD, CVD or ALD.
Preferably, after the formation of the interconnects, the conductive film and the adhesive film both present outside the interconnect recesses are removed.
Methods for removing the conductive film and the adhesive film include polishing, etching with a chemical and plasma etching. As with the above-described removal of conductive film, an appropriate method can be selected in consideration of the properties of the films, consistency with the previous or next processing, the morphology of the surface after the removal of the films, etc.
In a preferred embodiment of the present invention, the adhesive film contains tungsten, tantalum or titanium.
In a preferred embodiment of the present invention, the conductive film contains palladium, rhodium or ruthenium.
The conductive film is required to be thin film-formable, have a relatively high electric conductivity and hardly form an oxide film, a conductive one if formed, on the surface. A conductive film containing palladium, rhodium or ruthenium can meet these requirements. The conductive film can be formed by any known method such as PVD, CVD or ALD.
Preferably, the removal of the extra interconnect material of the film formed on the conductive film is carried out by electrolytic polishing using a polishing liquid containing phosphoric acid or hydroxyethane bisphosphonic acid and not containing abrasive grains.
By removing an extra interconnect material of the film formed on the substrate (conductive film) by electrolytic polishing, damage to the interconnect structure can be minimized, thus meeting the requirement for the interconnects-forming technology of the 45 nm-node or later generation.
There is a case in which copper as an interconnect material is removed by electrolytic polishing using a polishing liquid containing abrasive grains and a complexing agent for forming an insoluble copper complex, for example. In this case, polishing off with the abrasive grains of an insoluble copper complex formed on the surface of interconnects can cause damage, such as scratches, to the copper surface itself. As the size of interconnects becomes smaller, even a slight damage to interconnects will lead to an increase in the resistance of the interconnects. Thus, in the 45 nm-node or later generation, control of the morphology of the surfaces of interconnects after flattening will be of importance and it will be required to use an electrolytic polishing liquid which can effect flattening without the use of abrasive grains. The requirement can be met by a polishing liquid containing a highly-viscous acid, such as phosphoric acid or hydroxyethane bisphosphonic acid, and not containing abrasive grains.
The interconnect material is, for example, copper, a copper alloy, silver or a silver alloy.
The use of copper, a copper alloy, silver or a silver alloy as an interconnect material e.g. for a highly-integrated semiconductor device can provide a higher-speed, higher-density semiconductor device.
Preferably, a metal film is formed selectively on the surfaces of interconnects.
Instead of forming an insulating film, such as a silicon nitride film, having good adhesion and high effect of preventing diffusion of an interconnect material into an upper interlevel dielectric film, on an entire surface of a substrate having an embedded-interconnect structure, it is possible to selectively form a metal film only on the surfaces of interconnects in order to prevent oxidation of the interconnects, improve adhesion of the interconnects to the upper film and prevent diffusion of the interconnect material into the upper interlevel dielectric film. This can decrease the volume between interconnects and enhance the reliability of interconnects e.g. in a semiconductor device of the 45 nm-node or later generation.
The present invention provides an interconnects-forming apparatus, comprising: a conductive film-forming apparatus for forming a conductive film on a surface of a substrate having interconnect recesses, said conductive film being insoluble in an electrolytic plating solution for the formation of a film of an interconnect material; an electroplating apparatus for forming a film of the interconnect material on a surface of the conductive film; and a polishing apparatus for removing an extra interconnect material of the film formed on the conductive film.
The interconnects-forming apparatus is comprised of, for example, a PVD apparatus, a CVD apparatus or an ALD apparatus.
In a preferred embodiment of the present invention, the interconnects-forming apparatus further comprises a conductive film removal apparatus for removing the conductive film present outside the interconnect recesses.
The conductive film removal apparatus is comprised of, for example, a polishing apparatus, a chemical etching apparatus or a plasma etching apparatus. The polishing apparatus for removing an extra interconnect material of the film formed on the conductive film may also be used as the conductive film removal apparatus.
In a preferred embodiment of the present invention, the interconnects-forming apparatus further comprises an adhesive film-forming apparatus for forming an adhesive film on the surface of the substrate having the interconnect recesses.
The adhesive film-forming apparatus is comprised of, for example, a PVD apparatus, a CVD apparatus or an ALD apparatus.
In a preferred embodiment of the present invention, the interconnects-forming apparatus further comprises an adhesive film removal apparatus for removing the adhesive film present outside the interconnect recesses.
The adhesive film removal apparatus is comprised of, for example, a polishing apparatus, a chemical etching apparatus or a plasma etching apparatus. The polishing apparatus for removing an extra interconnect material of the film formed on the conductive film or the conductive film removal apparatus for removing the conductive film may also be used as the adhesive film removal apparatus.
In a preferred embodiment of the present invention, the electroplating apparatus includes a dummy resistor disposed between an anode and the substrate upon plating.
Though palladium, rhodium or ruthenium, to be used as a material for the conductive film, is each electrically conductive, partly-because of the thinness of the film, the conductive film has a remarkably higher sheet resistance compared to a conventional copper seed film or the like. For instance, a copper film having a thickness of 60 nm has a sheet resistance of about 0.3 Ω/sq, whereas a ruthenium film of the same thickness has a considerably higher sheet resistance of about 8 Ω/sq. When forming a film of an interconnect material, such as copper, by electroplating on a substrate, contact for electricity feeding is generally made in a peripheral region of the substrate. When the electric resistance of the base is high, a phenomenon called terminal effect can occur, i.e., an electric current concentrates in the peripheral region of the substrate whereby the plated film becomes thicker in the peripheral region. By providing a dummy resistor formed of, for example, a porous ceramic between an anode and a substrate in carrying out plating, it becomes possible to increase the resistance on the plating solution side to such a degree as to reduce the influence of the electric resistance of the base, thereby preventing the occurrence of the phenomenon called terminal effect. A method may be considered in which the acid concentration or the copper ion concentration of a plating solution is lowered to lower the electric conductivity of the plating solution to thereby prevent the occurrence of the phenomenon called terminal effect. This method, however, would adversely affect the plating properties, such as an embedding property, of the plating solution. The provision of a dummy resistor is therefore preferred.
In a preferred embodiment of the present invention, the polishing apparatus is comprised of an electrolytic polishing apparatus.
In a preferred embodiment of the present invention, the interconnects-forming apparatus further comprises a metal film-forming apparatus for forming a metal film selectively on the surfaces of interconnects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the overall construction of an interconnects-forming apparatus according to an embodiment of the present invention;
FIG. 2 is a plan view showing an electroplating apparatus for use in the interconnects-forming apparatus shown in FIG. 1;
FIG. 3 is a cross-sectional view taken along the line A-A of FIG. 2;
FIG. 4 is a cross-sectional view of a substrate holder and a cathode section of the electroplating apparatus shown in FIG. 2;
FIG. 5 is a cross-sectional view of an electrode arm section of the electroplating apparatus shown in FIG. 2;
FIG. 6 is a plan view of the electrode arm section, whose housing is not shown, of the electroplating apparatus shown in FIG. 2;
FIG. 7 is a schematic view of an anode and a high resistance structure of the electroplating apparatus shown in FIG. 2;
FIG. 8 is a schematic view of a polishing apparatus (electrolytic polishing apparatus) for use in the interconnects-forming apparatus shown in FIG. 1;
FIG. 9 is a flow chart of a process for forming interconnects by the interconnects-forming apparatus shown in FIG. 1;
FIG. 10 is a schematic diagram illustrating a substrate having an interconnect pattern formed in an insulating film;
FIG. 11 is a schematic diagram illustrating the formation of an adhesive film on a surface of the substrate (insulating film) shown in FIG. 10;
FIG. 12 is a schematic diagram illustrating the formation of a conductive film on a surface of the adhesive film shown in FIG. 11;
FIG. 13 is a schematic diagram illustrating the embedding of interconnect material (copper) by copper plating of the surface of the substrate shown in FIG. 12;
FIG. 14 is a schematic diagram illustrating the removal of unnecessary interconnect material, conductive film and adhesive film from the substrate shown in FIG. 13;
FIG. 15 is a schematic diagram illustrating the selective formation of a protective film on surfaces of interconnects of the substrate shown in FIG. 14; and
FIG. 16 is a schematic diagram illustrating the formation of an interlevel barrier film on the surface of the substrate shown in FIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described in detail with reference to the drawings. The following description illustrates the case of forming interconnects of copper (copper interconnects) on a substrate such as a semiconductor wafer, and forming a metal film (protective film) of a CoWP alloy selectively on surfaces of interconnects to protect the interconnects.
FIG. 1 shows an overall layout plan of an interconnects-forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, the interconnects-forming apparatus includes loading/ unloading chambers 10, 12 for carrying in a cassette housing substrates and carrying out a cassette housing substrates after a series of processings, and a rectangular apparatus frame 14 communicating with the loading/unloading chambers 10. 12.
In the interior of the apparatus frame 14 are housed an adhesive film-forming apparatus 36, a conductive film-forming apparatus 38, an electroplating apparatus 40, a heat treatment apparatus 42, a polishing apparatus 44, a conductive film/adhesive film removal apparatus 46, and a metal film (protective film)-forming apparatus 48, which are disposed along a substrate transport route. A movable transport robot 50, as a transport device, is disposed in a position surrounded by these apparatuses.
The adhesive film-forming apparatus 36 is to form an adhesive film containing e.g. tungsten, tantalum or titanium on a surface of a substrate (insulating film) and, according to this embodiment, is comprised of a PVD apparatus which includes a processing chamber 52 capable of vacuum evacuation, and a load lock chamber 58. The adhesive film-forming apparatus 36 may also be comprised of a CVD apparatus or an ALD apparatus.
The adhesive film-forming apparatus 36 is to form an adhesive film on a surface of a substrate (insulating film) prior to the formation of the below-described conductive film on the adhesive film so as to secure with the adhesive film a sufficient adhesion between the insulating film (interlevel dielectric film) and the conductive film, thereby preventing a loss of reliability due to insufficient adhesion between the conductive film and the insulating film. The adhesive film-forming apparatus 36 may be omitted when the conductive film can be formed with good adhesion on a surface of a substrate (insulating film).
The conductive film-forming apparatus 38 is to form a conductive film, which is insoluble in an electrolytic plating solution for the formation of a film of an interconnect material and which contains, for example, palladium, rhodium or ruthenium, on the surface of the adhesive film which has been formed on the surface of the substrate (insulating film) by the adhesive film-forming apparatus 36 and, according to this embodiment, is comprised of a PVD apparatus which includes a processing chamber 60 capable of vacuum evacuation, and a load lock chamber 62. The conductive film-forming apparatus 38 may also be comprised of a CVD apparatus or an ALD apparatus.
The conductive film is required to be thin film-formable, have a relatively high electric conductivity and hardly form an oxide film, a conductive one if formed, on the surface. A conductive film containing palladium, rhodium or ruthenium can meet these requirements.
In the case where the adhesive film-forming apparatus 36 is omitted, as described above, the conductive film is formed directly on the surface of the substrate (insulating film) by the conductive film-forming apparatus 38.
The electroplating apparatus 40 is to carry out electroplating of the surface of the substrate so as to form a film of the interconnect material (copper) on the surface of the conductive film serving as a seed film while filling interconnect recesses, such as trenches and via holes, with the interconnect material (copper).
The electroplating apparatus 40 is preferably provided with a dummy resistor disposed between an anode and the substrate during plating. FIGS. 2 through 7 show an example of such plating apparatus 40.
The electroplating apparatus 40, as shown in FIG. 2, is provided with a substrate processing section 2-1 for performing plating process and processing incidental thereto, and a plating solution tray 2-2 for storing a plating solution is disposed adjacent to the substrate processing section 2-1. There is also provided an electrode arm portion 2-6 having an electrode portion 2-5 which is held at the front end of a pivoting arm 2-4 pivotable about a rotating shaft 2-3 and which is swung between the substrate processing section 2-1 and the plating solution tray 2-2.
Furthermore, a pre-coating/recovering arm 2-7, and fixed nozzles 2-8 for ejecting pure water or a chemical liquid such as ion water, or a gas or the like toward a substrate are disposed laterally of the substrate processing section 2-1. In this embodiment, three of the fixed nozzles 2-8 are disposed, and one of them is used for supplying pure water. The substrate processing section 2-1, as shown in FIGS. 3 and 4, has a substrate holder 2-9 for holding a substrate W with its surface (surface to be plated) facing upward, and a cathode portion 2-10 located above the substrate holder 2-9 so as to surround a peripheral portion of the substrate holder 2-9. Further, a substantially cylindrical bottomed cup 2-11 surrounding the periphery of the substrate holder 2-9, for preventing scatter of various chemical liquids used during processing, is provided so as to be vertically movable by an air cylinder 2-12.
The substrate holder 2-9 is adapted to be raised and lowered by the air cylinder 2-12 between a lower substrate transfer position A, an upper plating position B, and a pretreatment/cleaning position C intermediate between these positions. The substrate holder 2-9 is adapted to rotate at an arbitrary acceleration and an arbitrary velocity integrally with the cathode portion 2-10 by a rotating motor 2-14 and a belt 2-15. Substrate carry-in and carry-out openings (not shown) are provided in confrontation with the substrate transfer position A in a frame side surface. When the substrate holder 2-9 is raised to the plating position B, a sealing member 2-16 and cathodes 2-17 (to be described below) of the cathode portion 2-10 are brought into contact with the peripheral edge portion of the substrate W held by the substrate holder 2-9. On the other hand, the cup 2-11 has an upper end located below the substrate carry-in and carry-out openings, and when the cup 2-11 ascends, the upper end of the cup 2-11 reaches a position above the cathode portion 2-10, as shown by imaginary lines in FIG. 3.
When the substrate holder 2-9 has ascended to the plating position B, the cathodes 2-17 are pressed against the peripheral edge portion of the substrate W held by the substrate holder 2-9 for thereby allowing electric current to pass through the substrate W. At the same time, an inner peripheral end portion of the sealing member 2-16 is brought into contact with an upper surface of the peripheral edge of the substrate W under pressure to seal its contact portion in a water tight manner. As a result, the plating solution supplied onto the upper surface of the substrate W is prevented from seeping from the end portion of the substrate W, and the plating solution is prevented from contaminating the cathodes 2-17.
As shown in FIG. 5, an electrode portion 2-5 of the electrode arm portion 2-6 has a housing 2-18 at a free end of a pivoting arm 2-4, a hollow support frame 2-19 surrounding the housing 2-18, and an anode 2-20 fixed by holding the peripheral edge portion of the anode 2-20 between the housing 2-18 and the support frame 2-19. The anode 2-20 covers an opening portion of the housing 2-18, and a suction chamber 2-21 is formed inside the housing 2-18. Further, as shown in FIGS. 6 and 7, a plating solution introduction pipe 2-28 and a plating solution discharge pipe (not shown), for introducing and discharging the plating solution, are connected to the suction chamber 2-21. Further, many passage holes 2-20 b communicating with regions above and below the anode 2-20 are provided over the entire surface of the anode 2-20.
In this embodiment, a high resistance structure 2-22 comprising a water retaining material and covering the entire surface of the anode 2-20 is attached to the lower surface of the anode 2-20. The high resistance structure 2-22 serves as a dummy resistor by causing the plating solution to enter its interior complicatedly.
The high resistance structure (dummy resistor) 2-22 is, for example, composed of porous ceramics such as alumina, SiC, mullite, zirconia, titania or cordierite, or a hard porous material such as a sintered compact of polypropylene or polyethylene, or a composite material comprising these materials, or a woven fabric or an un-woven fabric. In case of the alumina-based ceramics, for example, the ceramics with a pore diameter of 30 to 200 μm is used. In case of the SiC, SiC with a pore diameter of not more than 30 μm, a porosity of 20 to 95%, and a thickness of about 1 to 20 mm, preferably 5 to 20 mm, more preferably 8 to 15 mm, is used. The high resistance structure 2-22, in this embodiment, is constituted of porous ceramics of alumina having a porosity of 30%, and an average pore diameter of 100 μm. The porous ceramic plate per se is an insulator, but has a lower electric conductivity than a plating solution by causing plating solution to enter its interior complicatedly and follow a considerably long path in the thickness direction.
The high resistance structure (dummy resistor) 2-22, which has the high resistance, is disposed on the lower surface of the anode 2-20. Hence, the influence of the resistance of a conductive film (see FIG. 12) becomes a negligible degree. Consequently, the difference in current density over the surface of the substrate due to electrical resistance on the surface of the substrate W becomes small, and the uniformity of the plated film over the surface of the substrate improves.
Though palladium, rhodium or ruthenium, to be used as a material for the conductive film, is each electrically conductive, partly because of the thinness of the film, the conductive film has a remarkably higher sheet resistance compared to a conventional copper seed film or the like. For instance, a copper film having a thickness of 60 nm has a sheet resistance of about 0.3 Ω/sq, whereas a ruthenium film of the same thickness has a considerably higher sheet resistance of about 8 Ω/sq. When contact for electricity feeding is made in a peripheral region of the substrate, a phenomenon called terminal effect can occur as the electric resistance of the base is high, i.e. an electric current concentrates in the peripheral region of the substrate whereby the plated film becomes thicker in the peripheral region.
By providing the high resistance structure (dummy resistor) 2-22 formed of, for example, a porous ceramic between the anode 2-20 and the substrate W in carrying out plating, according to this embodiment, it becomes possible to increase the resistance on the plating solution side to such a degree as to reduce the influence of the electric resistance of the base, thereby preventing the occurrence of the phenomenon called terminal effect. A method may be considered in which the acid concentration or the copper ion concentration of a plating solution is lowered to lower the electric conductivity of the plating solution to thereby prevent the occurrence of the phenomenon called terminal effect. This method, however, would adversely affect the plating properties, such as an embedding property, of the plating solution. The provision of a dummy resistor is therefore preferred.
Further, by impregnating the high resistance structure 2-22 with the plating solution to thereby wet the surface of the anode 2-20, falling of a black film onto a surface to be plated of a substrate can be prevented and air can be discharged easily when supplying the plating solution between the surface to be plated of the substrate and the anode 2-20.
Attachment of the high resistance structure 2-22 to the anode 2-20 is performed as follows. Specifically, a large number of fixing pins 2-25 each having a head portion at the lower end thereof are arranged such that the head portion is housed in the high resistance structure 2-22 so as not to be releasable upward and a shaft portion of the fixing pin 2-25 extends through the anode 2-20. The fixing pins 2-25 are urged upward by U-shaped plate springs 2-26, so that the high resistance structure 2-22 is brought into close contact with the lower surface of the anode 2-20 by elastic forces of the leaf springs 2-26. With this arrangement, even when the thickness of the anode 2-20 is gradually reduced according to progress of plating, the high resistance structure 2-22 can be reliably brought into close contact with the lower surface of the anode 2-20. Accordingly, air is prevented from entering between the lower surface of the anode 2-20 and the high resistance structure 2-22 to cause plating defects.
The electrode portion 2-5 is lowered to a degree such that when the substrate holder 2-9 is located at the plating position B (see FIG. 4), the gap between the substrate W held by the substrate holder 2-9 and the high resistance structure 2-22 is in a range of about 0.1 to 10 mm, preferably 0.3 to 3 mm, and more preferably about 0.5 to 1 mm. In this state, the plating solution is supplied from a plating solution supply pipe to fill a space between the upper surface (surface to be plated) of the substrate W and the anode 2-20 with the plating solution while the high resistance structure 2-22 is impregnated with the plating solution. The surface, to be plated, of the substrate W is plated by applying a voltage from a power source between the upper surface (surface to be plated) of the substrate W and the anode 2-20.
Next, there will be described the plating process performed in the electroplating apparatus 40.
First, a substrate W to be plated is transferred to the substrate holder 2-9 located at the substrate transfer position A and placed on the substrate holder 2-9. Then, the cup 2-11 is lifted up and, at the same time, the substrate holder 2-9 is lifted up to the pretreatment/cleaning position C. In this state, the pre-coating/recovering arm 2-7 in the retracting position is moved to a position where the pre-coating/recovering arm 2-7 faces the substrate W, and a pre-coating solution of, for example, a surface-active agent is intermittently ejected from a pre-coating nozzle provided at the tip end of the pre-coating/recovering arm 2-7 onto the surface, to be plated, of the substrate W. At that time, the substrate holder 2-9 is rotated. Accordingly, the pre-coating solution can spread over an entire surface of the substrate W. Then, the pre-coating/recovering arm 2-7 is returned to the retracting position, and the rotational speed of the substrate holder 2-9 is increased so as to scatter the pre-coating solution on the surface, to be plated, of the substrate W by centrifugal forces to thereby dry the substrate.
Subsequently, after the substrate holder 2-9 is lifted up to the plating position B (see FIG. 4), the electrode arm section 2-6 is horizontally swung so that the electrode portion 2-5 is moved from above the plating solution tray 2-2 to above a position for plating. The electrode portion 2-5 is lowered toward the cathode portion 2-10 at that position. After lowering of the electrode portion 2-5 is completed, a plating voltage is applied between the anode 2-20 and the cathodes 2-17 while a plating solution is supplied into the electrode portion 2-5 so that the plating solution is supplied to the high resistance structure 2-22 through plating solution supply ports extending through the anode 2-20. At that time, the high resistance structure 2-22 is not brought into contact with the surface, to be plated, of the substrate W but is close to the surface, to be plated, of the substrate W at a distance of about 0.1 to 10 mm, preferably about 0.3 to 3 mm, more preferably about 0.5 to 1 mm.
When supply of the plating solution is continued, the plating solution containing copper ions, which oozes out of the high resistance structure 2-22, is filled in a space between the high resistance structure 2-22 and the surface, to be plated, of the substrate W, to thereby carry out copper plating on the surface, to be plated, of the substrate W. At that time, the substrate holder 2-9 may be rotated at a low speed.
After completion of the plating process, the electrode arm section 2-6 is lifted up and then swung so that the electrode portion 2-5 is returned to above the plating solution tray 2-2. Thereafter, the electrode portion 2-5 is lowered to the normal position. Next, the pre-coating/recovering arm 2-7 is moved from the retracting position to a position at which the pre-coating/recovering arm 2-7 faces the substrate W and then lowered. The plating solution remaining on the substrate W is recovered through a plating solution recovery nozzle (not shown). After completion of recovery of the remaining plating solution, the pre-coating/recovering arm 2-7 is returned to the retracting position. Thereafter, pure water is ejected toward the center of the substrate W and, at the same time, the substrate holder 2-9 is rotated while a speed of the substrate holder 2-9 is increased, to thereby replace the plating solution on the surface of the substrate W with pure water.
After the rinsing, the substrate holder 2-9 is lowered from the plating position B to the pretreatment/cleaning position C, and water washing is carried out by supplying pure water from the fixed nozzle 2-8 for pure water while the substrate holder 2-9 and the cathode portion 2-10 are rotated. At that time, the sealing member 2-16 and the cathodes 2-17 can also be cleaned together with the substrate W by pure water supplied directly to the cathode portion 2-10 or by pure water scattered from the surface of the substrate W.
After completion of the water washing, supply of pure water from the fixed nozzle 2-8 is stopped, and the rotational speed of the substrate holder 2-9 and the cathode portion 2-10 is increased to scatter the pure water on the surface of the substrate W by centrifugal forces to thereby dry the substrate. Simultaneously, the sealing member 2-16 and the cathodes 2-17 can also be dried. After completion of the drying, the rotation of the substrate holder 2-9 and the cathode portion 2-10 is stopped, and the substrate holder 2-9 is lowered to the substrate transfer position A.
The electroplating apparatus 40 of this embodiment includes a processing chamber 64 whose internal atmosphere is replaceable with an inert gas atmosphere, such as N₂gas, and a load lock chamber 66. A series of electrolytic plating processings of pre-plating processing, electroplating and post-plating processing can be carried out successively in an inert gas atmosphere, such as N₂gas, in the electroplating apparatus 40.
The heat treatment apparatus 42 is to carry out heat treatment (annealing) e.g. at 100-600° C. of the film of the interconnect material (copper) which has been formed in the electroplating apparatus 40 and, according to this embodiment, is comprised of a lamp annealing apparatus which includes a processing chamber (lamp annealing oven) 68 whose internal atmosphere is replaceable with an inert gas atmosphere, such as N₂gas, and a load lock chamber 70. The heat treatment apparatus 42 may also be comprised of an apparatus having a radiation heat oven, a reflected heat oven, a hot plate oven or a heat convection oven.
The polishing apparatus 44 is to remove an extra interconnect material (copper) of the film which has been formed on the surface of the conductive film in the electroplating apparatus 40, thereby forming interconnects composed of the interconnect material embedded in the interconnect recesses such as trenches and via holes and, according to this embodiment, is comprised of an electrolytic polishing apparatus which includes a processing chamber 72 whose internal atmosphere is replaceable with an inert gas atmosphere, such as N₂gas, and a load lock chamber 74.
By removing an extra interconnect material of the film formed on the substrate (conductive film) by electrolytic polishing, damage to the interconnect structure can be minimized, thus meeting the requirement for the interconnects-forming technology of e.g. the 45 nm-node or later generation.
The polishing apparatus (electrolytic polishing apparatus) 44 preferably uses a polishing liquid containing phosphoric acid or hydroxyethane bisphosphonic acid and not containing abrasive grains. FIG. 8 shows an example of such polishing apparatus (electrolytic polishing apparatus) 44.
The polishing apparatus (electrolytic polishing apparatus) 44 includes an upwardly-open bottomed cylindrical electrolytic bath 714 for holding therein a polishing liquid 712, and a substrate holder 716 a, disposed above the electrolytic bath 714, for detachably holding a substrate W with its front surface facing downwardly. The polishing liquid 712 contains phosphoric acid or hydroxyethane bisphosphonic acid but does not contain abrasive grains.
The electrolytic bath 714 is directly coupled to a main shaft 718 that rotates by the actuation of a motor or the like, and is provided at the bottom with a horizontally-disposed flat cathode plate 720 which is made of a metal, such as SUS, Pt/Ti, Ir/Ti, Ti, Ta or Nb that is stable to the polishing liquid and is not passivated by electrolysis, and which is to be immersed in the polishing liquid 712 and become a cathode. In an upper surface of the cathode plate 720, there are provided a lattice-form of long grooves 720 a extending linearly over the full length of the cathode plate 720. Further, a polishing tool 722, for example, a continuous-foam, hard polishing pad of a non-woven fabric type (e.g. SUBA800 manufactured by Rodel Nitta Company) is attached to the upper surface of the cathode plate 720. The polishing tool 722 is provided optionally.
As the main shaft 718 rotates, the electrolytic bath 714 rotates together with the polishing tool 722. As the polishing liquid 712 is supplied, the polishing liquid 712 flows through the long grooves 720 a, and products produced during electrolytic polishing, hydrogen gas, oxygen gas, etc. also pass through the long grooves 720 a and are discharged out from between the substrate W and the polishing tool 722.
The substrate holder 716 a is connected to the lower end of a support rod 724 which is provided with a rotating mechanism that can control rotational speed and a lifting mechanism that can adjust polishing pressure. The substrate holder 716 a attracts and holds the substrate W to its lower surface in a vacuum-attraction manner, for example.
At a peripheral portion of the lower surface of the substrate holder 716 a, there are provided electrical contacts 726 which, when the substrate W is attracted and held by the substrate holder 716 a, contact a peripheral or bevel portion of the substrate W to make the film of the interconnect material (copper) formed on the substrate W an anode. The electrical contacts 726 are connected, via a roll sliding connector built in the support rod 724 and a wire 728 a, to the anode terminal of an externally-disposed rectifier 730 as a power source, and the cathode plate 720 is connected via a wire 728 b to the cathode terminal of the rectifier 730.
Further, located above the electrolytic bath 714, a polishing liquid supply unit 732 for supplying the polishing liquid 712 into the electrolytic bath 714 is provided. The polishing apparatus 44 is also provided with a control unit 734 for adjusting and controlling the devices and the overall operation, and with a safety device (not shown).
In the operation of the polishing apparatus (electrolytic polishing apparatus) 44, the polishing liquid 712, containing phosphoric acid or hydroxyethane bisphosphonic acid and not containing abrasive grains, is supplied into the electrolytic bath 714, and the polishing liquid 712 is allowed to overflow the electrolytic bath 714 while the electrolytic bath 714 is rotated together with the polishing tool 722. On the other hand, the substrate W, having the surface film of interconnect material (copper), is attracted and held with its front surface facing downwardly by the substrate holder 716 a. While rotating the substrate W in the opposite direction to the rotating direction of the electrolytic bath 714, the substrate W is lowered and, as necessary, the front surface (lower surface) of the substrate W is brought into contact with the surface of the polishing tool 722, and, at the same time, an electric current is passed between the cathode plate 720 and the electrical contacts 726 by the rectifier 730. The interconnect material (copper) is then effectively polished and flattened.
If copper, as an interconnect material, is removed by electrolytic polishing using a polishing liquid containing abrasive grains and a complexing agent for forming an insoluble copper complex, polishing off with the abrasive grains of an insoluble copper complex formed on the surfaces of interconnects can cause damage, such as scratches, to the copper surface itself. As the size of interconnects becomes smaller, even a slight damage to interconnects will lead to an increase in the resistance of interconnects. Thus, in the 45 nm-node or later generation, for example, control of the morphology of the surfaces of interconnects after flattening will be of importance and it will be required to use an electrolytic polishing liquid which can effect flattening without the use of abrasive grains. The requirement can be met by a polishing liquid containing a highly-viscous acid, such as phosphoric acid or hydroxyethane bisphosphonic acid, and not containing abrasive grains.
The conductive film/adhesive film removal apparatus 46 is to remove the extra conductive film present outside the interconnect recesses, which has been formed by the conductive film-forming apparatus 38, and to remove the extra adhesive film present outside the interconnect recesses, which has been formed by the adhesive film-forming apparatus 36, in a successive manner and, according to this embodiment, is comprised of a polishing apparatus which includes a processing chamber 76 whose internal atmosphere is replaceable with an inert gas atmosphere, such as N₂gas, and a load lock chamber 78. The conductive film/adhesive film removal apparatus 46 may also be comprised of a chemical etching apparatus or a plasma etching apparatus. An appropriate type of apparatus can be selected in consideration of the properties of the conductive film and the adhesive film, consistency with the previous or next processing, the morphology of the surface after the removal of the films, etc.
In the case of not forming an adhesive film, the conductive film/adhesive film removal apparatus 46 functions as a conductive film removal apparatus for removing only the conductive film. Though in this embodiment the conductive film and the adhesive film are removed successively by the single polishing apparatus (conductive film/adhesive film removal apparatus) 46, depending on the materials, etc. of the conductive film and the adhesive film, it is also possible to separately provide a conductive film removal apparatus for removing the extra conductive film and an adhesive film removal apparatus for removing the extra adhesive film. Further, it is also possible to remove the conductive film and/or the adhesive film by the above-described polishing apparatus 44 for removing the extra interconnect material (copper).
The metal film (protective film)-forming apparatus 48 is to form a metal film (protective film) of a CoWP alloy or the like selectively on the surfaces of interconnects (copper interconnects), which have become exposed on the substrate surface by the removal of the extra interconnect material (copper), to protect the interconnects and, according to this embodiment, is comprised of an electroless plating apparatus which includes a processing chamber 80 whose internal atmosphere is replaceable with an inert gas atmosphere, such as N₂gas, and a load lock chamber 82. The electroless plating apparatus (metal film-forming apparatus) 48 includes in the processing chamber 80 a pre-processing tank, a plating tank and a post-processing tank, so that a series of plating processings can be carried out successively.
Though not shown diagrammatically, it is also possible to provide in the apparatus frame 14 an interlevel barrier film-forming apparatus for forming an interlevel barrier film of SiN or the like on the surface of the substrate after the selective formation of the metal film in the metal film-forming apparatus 48. The interlevel barrier film-forming apparatus is comprised of, for example, a CVD apparatus, a PVD apparatus or a wet plating apparatus.
A pair of gate valves 16 a, 16 b is provided at the inlet of the loading/unloading chamber 10 and at the outlet on the apparatus frame side. Similarly, a pair of gate valves 18 a, 18 b is provided at the inlet of the loading/unloading chamber 12 and at the outlet on the apparatus frame side. An inert gas supply line 20 and a gas discharge line 22 are connected to each of the loading/ unloading chambers 10, 12. Supply and discharge of gas for the loading/unloading chamber 10 and for the loading/unloading chamber 12 can be performed independently by shut-off valves.
The apparatus frame 14 is designed to be hermetically closable, and is connected to an inert gas supply line 30 extending from an inert gas supply source 26 and having, on its way, a gas supply pump 28 and a pair of shut-off valves disposed on either side of the pump 28, and is also connected to a gas discharge line 34 having, on its way, a gas discharge valve 32 that opens at a predetermined pressure higher than atmospheric pressure. Thus, by the actuation of the gas supply pump 28, an inert gas, such as N₂gas, is supplied into the apparatus frame 14, and the gas discharge valve 32 of the gas discharge line 34 opens when the pressure in the apparatus frame 14 has reached the predetermined pressure higher than atmospheric pressure, so that the interior of the apparatus frame 14 can be kept in the inert gas atmosphere at the predetermined pressure high than atmospheric pressure.
By thus keeping the pressure in the apparatus frame 14 at a higher pressure (positive pressure) than atmospheric pressure, the air can be prevented from flowing into the apparatus frame 14 replaced with the inert gas atmosphere.
By keeping the interior of the apparatus frame 14 in an inert gas atmosphere, as described above, the substrate W can be prevented from being exposed to the air during its transportation between the above apparatuses, whereby the substrate surface can be prevented from being oxidized on the way to the formation of interconnects.
A series of processins for forming interconnects by the interconnects-forming apparatus will now be described with reference to FIGS. 9 through 16.
First, a substrate W, as shown in FIG. 10, is prepared by forming an insulating film (interlevel dielectric film) 100 of SiO₂or the like by, for example, PVD, CVD or wet coating, and then forming an interconnect pattern comprising interconnect recesses, such as trenches 102 and via holes 104, in the insulating film 100 by, for example, RIE, CDE, sputter etching or wet etching. Such substrates W are housed in a cassette, and the cassette is carried into the loading/unloading chamber 10. At the same time, an empty cassette is carried into the loading/unloading chamber 12. Thereafter, the internal atmosphere of each of the loading/ unloading chambers 10, 12 is replaced with an inert gas atmosphere, such as N₂gas.
In particular, when the gate valves 16 a, 18 a on the inlet sides of the loading/ unloading chambers 10, 12 are open while the gate valves 16 b, 18 b on the outlet sides are closed, the cassettes are carried into the loading/ unloading chambers 10, 12. Thereafter, the gate valves 16 a, 18 a on the inlet sides are closed. While evacuating the loading/ unloading chambers 10, 12 through the gas discharge line 22, an inert gas, such as N₂gas, is supplied through the inert gas supply line 20 into the loading/ unloading chambers 10, 12, thereby replacing the internal atmosphere of each of the loading/ unloading chambers 10, 12 with the inert gas atmosphere at a higher pressure (positive pressure) than atmospheric pressure.
Similarly, while evacuating the apparatus frame 14 through the gas discharge line 34, an inert gas, such as N₂gas, is supplied through the inert gas supply line 30 into the apparatus frame 14, thereby replacing the internal atmosphere of the apparatus frame 14 with the inert gas atmosphere at a higher pressure than atmospheric pressure. Thereafter, the gate valves 16 b, 18 b at the outlets on the apparatus frame 14 sides of the loading/ unloading chambers 10, 12 are opened. Though in this embodiment a substrate W before the formation of interconnects is carried in from the loading/unloading chamber 10 and the substrate W after the formation of interconnects is carried out from the loading/unloading chamber 12, it is, of course, possible to employ a single loading/unloading chamber and to carry in a substrate W from a cassette and, after the formation of interconnects, return the substrate W, having interconnects, to the same cassette.
Next, the substrates W, having the interconnect pattern, are taken one by one by the transport robot 50 out of the cassette in the loading/unloading chamber 10, and the substrates W is carried into the adhesive film-forming apparatus 36. In the adhesive film-forming apparatus 36, as shown in FIG. 11, an adhesive film 106 containing tungsten, tantalum or titanium is formed on a surface of the insulating film 10 by, for example, sputtering.
The substrate W after the formation of the adhesive film 106 is carried into the conductive film-forming apparatus 38. In the conductive film-forming apparatus 38, as shown in FIG. 12, a conductive film 108 e.g. containing palladium, rhodium or ruthenium, which is insoluble in an electrolytic plating solution for the formation of a film of interconnect material, is formed on a surface of the adhesive film 106. As described previously, the adhesive film 106 is to secure a sufficient adhesion between the insulating film 100 and the conductive film 108 via the adhesive film 106. In case the conductive film 108 can be formed with good adhesion on the surface of the insulating film 100, it is possible to form the conductive film 108 directly on the surface of the insulating film 100 without forming an adhesive film.
The substrate W after the formation of the conductive film 108 is carried into the electroplating apparatus 40. In the electrolytic plating apparatus 40, the conductive film 108 is brought into contact with an electrolytic copper-plating solution while applying a given voltage between the conductive film 108 and the anode 2-20, thereby forming a film of copper 110 as an interconnect material on the surface of the conductive film 108 to fill the trenches 102 and the via holes 104 with the copper, as shown in FIG. 13. The substrate W after plating is spin-dried by rotating it at a high speed.
By thus using the conductive film 108, which is insoluble in an electrolytic plating solution for the formation of a film of the interconnect material (copper) 119, as a seed film in electroplating and forming a film of the interconnect material (copper) 110 directly on the conductive film 108, dissolution of the conductive film 108 in the plating solution can be avoided even when the conductive film (seed film) 108 is thin, and the film of the interconnect material can be formed after a sufficient contact between the conductive film 108 and the plating solution. This makes it possible to form a plated film of the interconnect material (copper) 110, having a sufficient adhesion to the conductive film 108, by electroplating uniformly on the entire surface of the conductive film 108 and thus can form highly-reliable embedded interconnects with good reproducibility. The internal atmosphere of the electroplating apparatus 40 may either be atmospheric or an inert gas atmosphere, and may be selected depending on the processing and the overall construction of the apparatus.
The substrate W after the formation of the film of copper 110 is carried into the heat treatment apparatus (lamp annealing apparatus) 42. In the heat treatment apparatus 42, the substrate W is subjected to heat treatment (lamp annealing), for example, at 350° C. for 5 minutes in an N₂gas atmosphere.
The substrate W after the heat treatment (annealing) is carried into the polishing apparatus (electrolytic polishing apparatus) 44. The substrate W after the heat treatment may be transported to a film thickness-measuring device to measure the thickness of the copper film. Based on the measured film thickness, the plating time of the next substrate, for example, may be adjusted and, in case of a shortage of the film thickness, an additional copper film formation by plating of the substrate W may be carried out.
In the polishing apparatus 44, the unnecessary copper 110 of the film formed on the conductive film 108, i.e., the copper 110 present outside the trenches 102 and the via holes 104, is removed. By removing the extra interconnect material (copper) 110 of the film formed on the conductive film 108 by electrolytic polishing, damage to the interconnect structure can be minimized. During polishing, the film thickness or the finish of the substrate may be checked with a monitor, and polishing may be terminated when the end point is detected with the monitor. The surface of the substrate W after the flattening is cleaned with a chemical and further cleaned (rinsed) with pure water, and the substrate W is then rotated at a high speed to spin-dry the substrate W.
The substrate W after the removal of the unnecessary copper 110 is carried into the conductive film/adhesive film removal apparatus 46. In the conductive film/adhesive film removal apparatus 46, the extra conductive film 108 and the extra adhesive film 106 present outside the trenches 102 and the via holes 104 are removed, thereby forming interconnects (copper interconnects) 112 of copper in the insulating film 100, as shown in FIG. 14.
In the case where the removal of the conductive film 108 and the adhesive 106 is carried out by the polishing apparatus 44, the interconnect material (copper) 110, the conductive film 108 and the adhesive film 106 can be removed successively in the polishing apparatus 44.
The substrate W after the removal of the interconnect material (copper) 110, the conductive film 108 and the adhesive film 106 is carried into the metal film-forming apparatus (electroless plating apparatus) 48. In the metal film-forming apparatus 48, the substrate surface is first brought into contact with a pre-processing solution in the pre-processing tank to carry out pre-processing of the surfaces of interconnects 112, such as cleaning processing (CMP residue removal processing) and catalyst application processing to apply a catalyst such as Pd to the surfaces of interconnects 112. The substrate W after the pre-processing is subjected to a series of electroless plating processings of: immersing the substrate W in an electroless CoWP-plating solution, held in the plating tank, e.g. at 80° C. for three minutes; bringing the surface of the substrate W after the plating into contact with a post-cleaning liquid in the post-cleaning tank to carry out post-processing, such as post-cleaning, of the substrate W; and rotating the cleaned substrate W at a high speed to spin-dry the substrate W.
A metal film (protective film) 114 of a CoWP alloy with a thickness of e.g. 20 nm is thus formed selectively on the surfaces of interconnects 112, formed in the insulating film 100, to protect the interconnects 112, as shown in FIG. 15. The thickness of the protective film 114 is about 0.1 to 500 nm, preferably about 1 to 200 nm, more preferably about 10 to 100 nm. During the plating, the thickness of the metal film 114 may be monitored, and the electroless plating may be terminated when the film thickness has reached a predetermined value, i.e., when the end point is detected.
The selective formation of the metal film 114 only on the surfaces of interconnects 112 can prevent oxidation of the interconnects 112, improve adhesion of the interconnects 112 to the upper film and prevent diffusion of the interconnect material into the upper interlevel dielectric film. This can decrease the volume between interconnects and enhance the reliability of interconnects e.g. in a semiconductor device of the 45 nm-node or later generation.
In the case where an interlevel barrier film-forming apparatus is provided in the apparatus frame 14, the substrate W after the formation of the protective film 114 is transported to the interlevel barrier film-forming apparatus, where an interlevel barrier film 116 of SiN or the like, e.g. having a thickness of about 30 nm, is formed on the surface of the substrate W e.g. by CVD, as shown in FIG. 16.
The substrate W after the formation of the interlevel barrier film 116 is carried by the transport robot 50 into the cassette in the loading/unloading chamber 12.
Though in this embodiment copper is used as an interconnect material, it is also possible to use a copper alloy, silver or a silver alloy, besides copper. Further, though a CoWP alloy is used for the protective film 114, it is also possible to use Co as a simple substance, or a Co alloy other than CoWP, such as a CoWB alloy, a CoP alloy or a CoB alloy. Furthermore, Ni as a simple substance, or a Ni alloy, such as a NiWP alloy, a NiWB alloy, a NiP alloy or a NiB alloy, may also be employed.
The present invention makes it possible to form a plated film of interconnect material, having a sufficient adhesion to a conductive film which has previously been formed on a substrate, by electroplating uniformly on the entire surface of the substrate (conductive film) and thus can form highly-reliable embedded interconnects with good reproducibility. Further, by carrying out the removal of an extra interconnect material of the film formed on the conductive film by electrolytic polishing, damage to the interconnect structure can be minimized, thus meeting the requirement for the interconnects-forming technology of the 45 nm-node or later generation.

Claims

1. An interconnects-forming method, comprising:

forming a conductive film on a surface of a substrate having interconnect recesses formed in an insulating film, said conductive film being insoluble in an electrolytic plating solution for the formation of a film of an interconnect material;

forming a film of the interconnect material by electroplating on a surface of the conductive film serving as a seed film while filling the interconnect recesses with the interconnect material; and

removing an extra interconnect material of the film formed on the conductive film, thereby forming interconnects of the interconnect material embedded in the interconnect recesses.

2. The interconnects-forming method according to claim 1, wherein after the formation of the conductive film, the conductive film is subjected to pre-processing prior to the formation of the film of the interconnect material by electroplating.

3. The interconnects-forming method according to claim 1, wherein after the formation of the interconnects, the conductive film present outside the interconnect recesses is removed.

4. The interconnects-forming method according to claim 1, wherein the conductive film contains palladium, rhodium or ruthenium.

5. The interconnects-forming method according to claim 1, wherein the interconnect material comprises copper, a copper alloy, silver or a silver alloy.

6. The interconnects-forming method according to claim 1, wherein a metal film is formed selectively on the surfaces of interconnects.

7. An interconnects-forming method, comprising:

forming an adhesive film on a surface of a substrate having interconnect recesses formed in an insulating film;

forming a conductive film on a surface of the adhesive film, said conductive film being insoluble in an electrolytic plating solution for the formation of a film of an interconnect material;

8. The interconnects-forming method according to claim 7, wherein after the formation of the conductive film, the conductive film is subjected to pre-processing prior to the formation of the film of the interconnect material by electroplating.

9. The interconnects-forming method according to claim 7, wherein after the formation of the interconnects, the conductive film and the adhesive film both present outside the interconnect recesses are removed.

10. The interconnects-forming method according to claim 7, wherein the adhesive film contains tungsten, tantalum or titanium.

11. The interconnects-forming method according to claim 7, wherein the conductive film contains palladium, rhodium or ruthenium.

12. The interconnects-forming method according to claim 8, wherein the interconnect material comprises copper, a copper alloy, silver or a silver alloy.

13. The interconnects-forming method according to claim 7, wherein a metal film is formed selectively on the surfaces of interconnects.

14. An interconnects-forming apparatus, comprising:

a conductive film-forming apparatus for forming a conductive film on a surface of a substrate having interconnect recesses, said conductive film being insoluble in an electrolytic plating solution for the formation of a film of an interconnect material;

an electroplating apparatus for forming a film of the interconnect material on a surface of the conductive film; and

a polishing apparatus for removing an extra interconnect material of the film formed on the conductive film.

15. The interconnects-forming apparatus according to claim 14, further comprising a conductive film removal apparatus for removing the conductive film present outside the interconnect recesses.

16. The interconnects-forming apparatus according to claim 14, further comprising an adhesive film-forming apparatus for forming an adhesive film on the surface of the substrate having the interconnect recesses.

17. The interconnects-forming apparatus according to claim 14, further comprising an adhesive film removal apparatus for removing the adhesive film present outside the interconnect recesses.

18. The interconnects-forming apparatus according to claim 14, wherein the electroplating apparatus includes a dummy resistor disposed between an anode and the substrate upon plating.

19. The interconnects-forming apparatus according to claim 14, wherein the polishing apparatus is comprised of an electrolytic polishing apparatus.

20. The interconnects-forming apparatus according to claim 19 further comprising a metal film-forming apparatus for forming a metal film selectively on the surfaces of interconnects.