JP2013122970A - Method for forming wiring structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a wiring structure, which is capable of increasing embedding properties of a wiring layer formed by electrolytic plating.SOLUTION: The method for forming a wiring structure comprises a metal nitride film forming step of forming a WN film 43 on a semiconductor substrate 41 on which an insulating film 42 having a through hole 42a has been laminated, a tungsten silicide film forming step of laminating a WSi film 44 on the WN film 43, and a wiring forming step of forming a wiring layer 46 made of Cu by electrolytic plating, in the through hole 42a in which the WN film 43 and the WSi film 44 have been formed.

Description

  The technology of the present disclosure relates to a method for forming a wiring structure having a wiring layer embedded in a hole of an insulating layer through a metal nitride film.

  Conventionally, as described in Patent Document 1, for example, a metal nitride film such as a tungsten nitride (WN) film has been widely used for a barrier metal layer of a copper (Cu) wiring buried in a via hole or a contact hole. ing.

  Examples of the metal nitride film used as the barrier metal layer include a WN film, a titanium nitride (TiN) film, and a tantalum nitride (TaN) film. These metal nitride films enhance the adhesion between the Cu wiring and the insulating film or suppress mutual diffusion between the Cu wiring and the insulating film. By such a function of the barrier metal layer, the electrical connection in the semiconductor device having the Cu wiring is stably maintained.

International Publication No. 2004/061154

  By the way, the Cu wiring is formed through the process shown in FIG. That is, when forming the Cu wiring, as shown in FIG. 7A, a WN film as a barrier metal layer 53 is formed on the insulating film 52 formed on the semiconductor substrate 51 by, for example, the ALD method. The

  When the barrier metal layer 53 is formed, as shown in FIG. 7B, a seed layer 54 made of Cu is formed on the barrier metal layer 53 by sputtering, for example. At this time, since the sputtered Cu particles easily reach the bottom surface of the through hole 52a and the side surface near the opening of the through hole 52a, the seed layer 54 having a predetermined film thickness is formed. On the other hand, since the sputtered particles do not easily reach the side surface near the bottom surface of the through hole 52a, the seed layer 54 is not formed, or a discontinuous portion 54a in which the seed layer 54 is thinner than other regions is generated. become.

  Thereafter, as shown in FIG. 7C, a wiring layer 55 is formed in the through hole 52a by electrolytic plating. At this time, it is difficult for current to flow through the discontinuous portion 54a, and the resistance of WN forming the barrier metal layer 53 is high, so that Cu is unlikely to precipitate near the discontinuous portion 54a. As a result, a gap 55 a is formed near the discontinuous portion 54 a in the wiring layer 55. When Cu wiring is directly formed on the WN film, the current flows only through the WN film having a higher resistance than the seed layer 54, so that there are more voids 55 a in the wiring layer 55. It tends to occur.

  Such a problem is not limited to the case where the material for forming the barrier metal layer 53 is WN, but when the barrier metal layer 53 is formed from another metal nitride film such as TaN or TiN. In addition, it is also common in the case of a recess such as a through hole or a trench formed in the semiconductor substrate. The problem is generally common regardless of the film formation method of the barrier metal layer 53 and the seed layer 54.

  The technology of the present disclosure has been made in view of the above circumstances, and an object thereof is to provide a method for forming a wiring structure that can improve the embedding property of a wiring layer formed by electrolytic plating.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
One aspect of the technology of the present disclosure is a method for forming a wiring structure, wherein a metal nitride film formed of a nitride of tantalum, titanium, or tungsten is formed on a substrate having a recess, and A tungsten silicide film forming step in which a tungsten silicide film is laminated on the metal nitride film, and a copper wiring layer is electrolyzed in the recess in which the metal nitride film and the tungsten silicide film are formed. Wiring formation process formed by plating.

  In the above aspect, after the metal nitride film is formed on the substrate, a tungsten silicide film having a resistance lower than that of the metal nitride film is laminated on the metal nitride film. For this reason, when the copper wiring is formed by electrolytic plating, current flows more easily on the inner wall of the recess than when only the metal nitride film is formed. As a result, a region where no current flows is less likely to be generated on the inner wall of the recess, so that a void is less likely to occur in the wiring layer formed in the recess. That is, according to the above aspect, the embedding property of the wiring layer formed by electrolytic plating can be improved.

  In another aspect of the method for forming a wiring structure in the present disclosure, in the above-described aspect, a seed layer made of copper is formed on the tungsten silicide film between the tungsten silicide film forming step and the wiring forming step. A seed layer forming step is further provided.

  In the above aspect, since the seed layer made of copper is formed on the tungsten silicide film, a current flows through the metal nitride film, the tungsten silicide film, and the seed layer during electrolytic plating. As a result, voids are less likely to be formed in the wiring layer. In addition, since the tungsten silicide film is formed as the lower layer of the seed layer, current flows through the tungsten silicide film even when the seed layer is not formed on the entire inner wall surface of the recess. In the wiring layer, voids are hardly formed. Therefore, the seed layer can be made thinner than when the seed layer is formed directly on the metal nitride film.

  According to another aspect of the method for forming a wiring structure in the present disclosure, in the above aspect, in the metal nitride film forming step and the tungsten silicide film forming step, the metal nitride film and the tungsten silicide film are formed by a CVD method and an ALD. Formed by any of the law.

  According to the above aspect, the metal nitride film and the tungsten silicide film are formed by either the CVD method or the ALD method. Therefore, compared with the case where the metal nitride film and the tungsten silicide film are formed by, for example, sputtering, these films are more easily formed by the entire inner wall surface of the recess. Therefore, the embedding property of the wiring layer formed by electrolytic plating is improved.

  According to another aspect of the method for forming a wiring structure in the present disclosure, in the above aspect, in the metal nitride film forming step and the tungsten silicide film forming step, the metal nitride film and the tungsten silicide film are formed by the ALD method. In the metal nitride film forming step, a first source gas supply step in which a source gas containing tungsten is supplied to the substrate, and a reducing gas supply step in which a reducing gas for reducing the source gas is supplied to the substrate. And a second source gas supplying step in which the source gas is supplied to the substrate and a nitriding gas supplying step in which a nitriding gas for nitriding tungsten is supplied to the substrate are repeated in this order, whereby the tungsten nitride film is formed. In the tungsten silicide film forming step, a source gas supply step for supplying the source gas, a reducing gas supply step, , It is repeated in this order.

  In the above aspect, the tungsten nitride film as the metal nitride film and the tungsten silicide film are formed by the ALD method in which several atomic layers are formed on the substrate. In this case, the tungsten silicide film is formed by repeating the process of removing the second source gas supply process and the nitride gas supply process from the process of forming the tungsten nitride film. Therefore, according to the tungsten silicide film laminated on the tungsten nitride film, the embedding property of the wiring layer can be improved, and an open tungsten silicide film composed of several atomic layers can be formed with fewer steps. Can do.

The block diagram which shows the whole structure of the multi-chamber type | mold formation apparatus which forms the WN film | membrane, WSi film | membrane, and seed layer which have a wiring structure. Schematic which shows schematic structure of the ALD apparatus which forms a WN film and a WSi film. The timing chart which shows the supply aspect of various gas in one Embodiment which actualized the formation method of the wiring structure of this indication. (A) (b) (c) Process drawing which shows the manufacturing method of the semiconductor device in the embodiment in order of a process. (A) (b) SEM image which shows the cross-sectional structure of the hole formed in the silicon substrate, and the wiring layer formed in the hole. The graph which shows the relationship between the cycle number at the time of formation of a WN film | membrane and a WSi film | membrane, and a film thickness. (A) (b) (c) Process drawing which shows the formation method of the conventional wiring structure in order of a process.

  Hereinafter, an embodiment embodying a method for forming a wiring structure according to the present disclosure will be described with reference to FIGS. First, a multi-chamber type film forming apparatus for forming a tungsten nitride film (WN film) and a tungsten silicide film (WSi film) having a wiring structure will be described with reference to FIG. In FIG. 1, the direction in which the substrate to be processed is transported is indicated by an arrow.

[Configuration of multi-chamber deposition system]
As shown in FIG. 1, the transfer chamber 11 included in the multi-chamber film forming apparatus 10 includes a carry-in chamber 12, a carry-out chamber 13, a pretreatment chamber 14, a film formation chamber 15, and a seed layer forming chamber 16. It is connected. The transfer chamber 11 is equipped with a transfer robot 11a for transferring a substrate. The substrate is an object to be processed in the multi-chamber type film forming apparatus 10, and is a semiconductor substrate in which an insulating film having a through hole, for example, a silicon oxide film is stacked. The substrate may be a semiconductor substrate such as a silicon substrate having a recess such as a through hole or a trench. In this case, an insulating film such as a silicon oxide film is formed in the upper surface of the silicon substrate and in the through hole. Has been.

  The transport robot 11a transports the unprocessed substrate carried into the carry-in chamber 12 to the pre-treatment chamber 14, the film formation chamber 15, and the seed layer formation chamber 16 in this order, and processes in these chambers 14-16. Then, the processed substrate is transferred to the carry-out chamber 13.

  The carry-in chamber 12 carries in a substrate before processing from the outside in a state where the inside is at atmospheric pressure, and puts the substrate before processing into the transfer chamber 11 in a state where the inside is reduced from atmospheric pressure by an exhaust unit (not shown). Take it out.

  The carry-out chamber 13 carries in the processed substrate from the transfer chamber 11 in a state where the inside is decompressed by an exhaust unit (not shown), and carries out the processed substrate outside in a state where the inside is at atmospheric pressure. The carry-in chamber 12 and the carry-out chamber 13 may be provided as one load lock chamber having both the carry-in / out functions.

The pretreatment chamber 14 is a plasma treatment chamber that generates plasma from hydrogen (H ₂ ) gas. Pretreatment chamber 14, for example, a high-frequency power frequency is 13.56MHz to supply the _{H 2} gas to generate a plasma from the _{H 2} gas.

  The film forming chamber 15 is an ALD chamber that forms several atomic films of WN film and WSi film on the substrate. The film forming chamber 15 forms a laminated film in which a WN film and a WSi film are laminated in this order.

  The seed layer forming chamber 16 is a sputtering chamber for forming a copper (Cu) film on the substrate. The Cu film formed on the substrate and the laminated film serve as a seed layer when copper wiring is formed in the through hole by electrolytic plating.

  The transfer chamber 11, the pretreatment chamber 14, the film formation chamber 15, and the seed layer formation chamber 16 have an exhaust unit (not shown), similar to the carry-in chamber 12 and the carry-out chamber 13, and atmospheric pressure is generated by the exhaust unit. The pressure is maintained under reduced pressure.

[Structure of deposition chamber]
The configuration of the film forming chamber 15 will be described in more detail with reference to FIG. As shown in FIG. 2, a substrate stage 22 that holds the substrate S is installed in a vacuum chamber 21 of the film forming chamber 15. A heater 23 for heating the substrate stage 22 is mounted inside the substrate stage 22. A heater power supply 24 that outputs a direct current is connected to the heater 23. The heater 23 generates heat by supplying current from the heater power supply 24, thereby heating the substrate S to a predetermined temperature via the substrate stage 22.

  Two exhaust ports P1 penetrating the bottom wall 21a are formed in the bottom wall 21a of the vacuum chamber 21. An exhaust unit 25 that exhausts the inside of the vacuum chamber 21 is connected to the two exhaust ports P1. The exhaust unit 25 includes, for example, various vacuum pumps and a valve that adjusts the exhaust flow rate of the vacuum pump.

  A shower plate 26 is attached to the upper wall 21 b of the vacuum chamber 21 at a position facing the substrate stage 22. The shower plate 26 is formed with a plurality of openings 26 a that open to the substrate stage 22 side. A gas supply port P <b> 2 that penetrates the upper wall 21 b of the vacuum chamber 21 and the attachment surface of the shower plate 26 to the upper wall 21 b is formed.

  Connected to the gas supply port P2 are a hydrogen-based gas pipe GL1 for supplying a gas containing hydrogen to the vacuum chamber 21 and a fluorine-based gas pipe GL2 for supplying a gas containing fluorine to the vacuum chamber 21.

The hydrogen-based gas pipe GL1 includes a silane gas pipe connected to a silane gas supply unit 31 that supplies a silane gas such as monosilane (SiH ₄ ) gas to the vacuum chamber 21, and a nitriding gas such as ammonia (NH ₃ ) gas in the vacuum chamber 21. It branches off to a nitriding gas pipe to which the nitriding gas supply section 32 to be supplied is connected. The silane gas pipe is connected to an inert gas supply unit 33 for supplying an inert gas such as nitrogen (N ₂ ) gas to the vacuum chamber 21 through the pipe, while the nitriding gas pipe is connected to the silane gas pipe through the pipe. An inert gas supply unit 34 for supplying N ₂ gas to the vacuum chamber 21 is connected.

A raw material gas supply unit 35 that supplies a raw material gas containing tungsten such as tungsten hexafluoride (WF ₆ ) gas to the vacuum chamber 21 is connected to the fluorine-based gas pipe GL2. From the fluorine-based gas pipe GL2, an inert gas pipe connected to an inert gas supply unit 36 for supplying N ₂ gas to the vacuum chamber 21 is branched.

[Method of forming wiring structure]
Hereinafter, a method for forming a wiring structure in the present embodiment will be described with reference to FIGS. The wiring structure is formed by a process in which the WN film, the WSi film, and the seed layer are formed in the multi-chamber type film forming apparatus 10, and the wiring layer is formed in another apparatus that performs electrolytic plating. Process. In the following, the process of forming the WN film and the WSi film will be described with reference to FIG. 3, and the process of forming the seed layer and the wiring layer will be described with reference to FIG.

  When the WN film and the WSi film are formed by the multi-chamber type film forming apparatus 10, first, the substrate S before processing is carried into the carry-in chamber 12 by an external transfer robot. When the substrate S is loaded into the loading chamber 12, the substrate S is loaded into the pretreatment chamber 14 by the transfer robot 11a.

Next, in the pretreatment chamber 14, as shown in FIG. 3, at timing T1, supply of H ₂ gas and supply of high-frequency power to the H ₂ gas are started. Thereby, plasma generated from the H ₂ gas is supplied to the substrate S, and the surface of the insulating film formed on the substrate S is terminated with hydrogen. Alternatively, excited species containing hydrogen are adsorbed on the surface of the semiconductor substrate. When such a hydrogen plasma supply process is continued for a predetermined time, the supply of H ₂ gas and high-frequency power is stopped at timing T2. When the H ₂ plasma is supplied, the substrate S is transferred from the pretreatment chamber 14 to the film forming chamber 15 by the transfer robot 11a.

When the substrate S is carried into the film forming chamber 15, supply of SiH ₄ gas from the silane gas supply unit 31 to the vacuum chamber 21 is started at timing T3. When the supply of the SiH ₄ gas is continued for a predetermined time, the supply of the SiH ₄ gas is stopped at a timing T4. Thereby, SiH ₄ is adsorbed on substantially the entire surface of the substrate S through the hydrogen.

Similarly, at timing T4, supply of WF ₆ gas, which is a raw material gas for forming the WN film, is started. Thus, since the timing at which the supply of the SiH ₄ gas is stopped and the timing at which the supply of the WF ₆ gas is started are made simultaneous, the timing when the WF ₆ gas is supplied is larger than the subsequent timing. There is a high possibility that SiH ₄ is adsorbed on the substrate S. Therefore, WF ₆ is easily adsorbed on the entire substrate S. Note that before the introduction of the WF ₆ gas at the timing T4, evacuation time for the uniformity and particle measures the deposition surface, or even if the N ₂ gas introduction time is provided for introducing the N ₂ gas into the vacuum chamber In that case, for example, the exhaust time and the N ₂ gas introduction time are 1 to 2 seconds.

When the supply of the WF ₆ gas from the source gas supply unit 35 to the vacuum chamber 21 is continued for a predetermined time, the supply of the WF ₆ gas is stopped at timing T5. In such a first source gas supply process, WF ₆ supplied to the substrate S is adsorbed on the substrate S through the SiH ₄ .

When the supply of the WF ₆ gas to the substrate S is performed, the supply of N ₂ gas from the inert gas supply unit 36 to the vacuum chamber 21 is started at the timing T5, and at a timing T6 after a predetermined time. Thus, the supply of N ₂ gas is stopped. Thus, WF ₆ in the vacuum chamber 21 is evacuated with _{N 2} gas.

The exhaust gas by the N ₂ gas is performed at a timing T6, supplied from the silane gas supply unit 31 of the SiH ₄ gas as a reducing gas into the vacuum chamber 21 is started at time T7 after a predetermined time, SiH ₄ gas Is stopped. Through such a reducing gas supply process, WF ₆ and SiH ₄ react on the substrate S, and as a result, a W film of several atomic layers containing Si is formed on the substrate S.

When W film is formed, at the timing T7, the supply of N ₂ gas into the vacuum chamber 21 from the inert gas supply unit 33 is started, at the timing T8 after a predetermined time, the supply of N ₂ gas Stopped. Thereby, the SiH ₄ gas in the vacuum chamber 21 is exhausted together with the N ₂ gas.

When the exhaust gas by the N ₂ gas is carried out, at the timing T8, the supply from the feed gas supply section 35 of the WF ₆ gas into the vacuum chamber 21 is started again, at the timing T9 after a predetermined time, the supply of WF ₆ gas Is stopped. By such a second source gas supply step, WF ₆ is adsorbed on the substrate S on which the W film of several atomic layers is formed.

When the supply of WF ₆ gas is performed at a timing T9, the supply of N ₂ gas into the vacuum chamber 21 is started from the inert gas supply unit 36, at the timing T10 after the predetermined time, the supply of N ₂ gas Is stopped. Thus, WF ₆ in the vacuum chamber 21 is evacuated with _{N 2} gas.

When the exhaust gas by the N ₂ gas is carried out, at the timing T10, supplied from the nitriding gas supply unit 32 of the NH ₃ gas as a nitriding gas into the vacuum chamber 21 is started at timing T11 after the predetermined time, NH ₃ Gas supply is stopped. Through such a nitriding gas supply step, W (NH ₂ ) F ₅ having a higher reactivity with W than NH ₃ is generated by a reaction between WF ₆ adsorbed on the substrate S and NH ₃ . When this W (NH ₂ ) F ₅ reacts with W formed on the substrate S, a WN film of several atomic layers is formed.

When WN film is formed, at the timing T11, the supply of N ₂ gas from the inert gas supply unit 34 into the vacuum chamber 21 is started at timing T12 after the predetermined time, the supply of N ₂ gas Stopped. Thereby, NH ₃ in the vacuum chamber 21 is exhausted together with the N ₂ gas.

  The cycle from timing T4 to timing T12 is one cycle, and the film formation cycle is repeated a predetermined number of times, whereby a WN film having a predetermined film thickness is formed. A subsequent cycle is started simultaneously with the end of the preceding cycle. That is, the timing T12 of the preceding cycle and the timing T4 of the subsequent cycle are simultaneous. A WN film is formed on the substrate S by such a metal nitride film forming step.

When WN film is formed, at the timing T13, the supply of WF ₆ gas from the feed gas supply section 35 into the vacuum chamber 21 is started at timing T14 after the predetermined time, the supply of WF ₆ gas is stopped The By such a raw material gas supply step, WF ₆ is adsorbed to substantially the entire WN film formed on the substrate S. Note that the first cycle in forming the WSi film is started simultaneously with the end of the final cycle in forming the WN film. That is, the timing T12 in the final cycle of WN film formation and the timing T13 in the first cycle of WSi film formation are simultaneous.

When WF ₆ gas is supplied at the timing T14, the supply of _{N 2} gas into the vacuum chamber 21 is started from the inert gas supply unit 36, at the timing T15 after the predetermined time, the supply of _{N 2} gas Stopped. Thus, WF ₆ in the vacuum chamber 21 is evacuated with _{N 2} gas.

When the exhaust gas by the N ₂ gas is carried out, at the timing T15, the supply of the SiH ₄ gas into the vacuum chamber 21 is started from the silane gas supply unit 31, at the timing T16 after the predetermined time, SiH ₄ gas supply is stopped Is done. Through such a reducing gas supply process, WF ₆ adsorbed on the substrate S reacts with SiH ₄ , whereby a several atomic layer WSi film is formed on the substrate S.

When the WSi film is formed, the supply of N ₂ gas from the inert gas supply unit 33 to the vacuum chamber 21 is started at timing T16, and the supply of N ₂ gas is stopped at timing T17 after a predetermined time. Is done. Thereby, SiH ₄ in the vacuum chamber 21 is exhausted together with the N ₂ gas.

  The cycle from timing T13 to timing T17 is one cycle, and the film formation cycle is repeated a predetermined number of times, whereby a WSi film having a predetermined film thickness is formed. A subsequent cycle is started simultaneously with the end of the preceding cycle. That is, the timing T13 of the preceding cycle and the timing T17 of the following cycle are simultaneous. By such a tungsten silicide film forming step, a WSi film is formed on the WN film.

  Thus, the WN film and the WSi film are formed by the ALD method in which the films are formed by several atomic layers. Therefore, the WN film and the WSi film are formed substantially uniformly on the upper surface of the substrate S and the entire inner wall surface of the through hole.

  Thus, as shown in FIG. 4A, the insulating film 42 on the semiconductor substrate 41 is formed with the WN film 43 and the WSi film 44 on the upper surface of the insulating film 42 and the inner wall surface of the through hole 42a. The When the WN film and the WSi film are formed, the substrate S is transferred from the film forming chamber 15 to the seed layer forming chamber 16 by the transfer robot 11a.

  When the substrate S is transferred to the seed layer forming chamber 16, the Cu target is sputtered by plasma generated from an inert gas such as argon gas, for example, as shown in FIG. A seed layer 45 made of is formed on the WSi film 44. In this seed layer forming step, since the sputtered particles easily reach the upper surface of the insulating film 42 and the vicinity of the opening and the bottom surface of the through hole 42a, the seed layer 45 is formed relatively thick. On the other hand, since the sputtered particles hardly reach the bottom surface side of the inner wall surface of the through hole 42a, a discontinuous portion 45a in which the seed layer 45 is not formed or the seed layer 45 is formed relatively thin is generated.

  When the seed layer 45 is formed on the substrate S, the substrate S is transported to the unloading chamber 13 by the transport robot 11a, and the substrate S is unloaded from the multi-chamber type film forming apparatus 10 by the unloading chamber 13. Is done.

  When the substrate S is unloaded from the multi-chamber type film forming apparatus 10, the substrate S is loaded into an apparatus for electrolytic plating, and the formation of a wiring layer using electrolytic plating on the substrate S is performed in the apparatus. Done. That is, after the substrate S and the copper source are immersed in the electrolytic solution, the WN film 43, the WSi film 44, and the seed layer 45 included in the substrate S become the cathode, and the copper source becomes the anode. A direct current is supplied from the power source. By such wiring formation process, copper ions eluted from the copper source are reduced on the seed layer 45, so that the wiring layer 46 penetrates the surface of the insulating film 42 and penetrates as shown in FIG. It is formed in the hole 42a. As a result, a wiring structure having the WN film 43, the WSi film 44, and the wiring layer 46 made of Cu is formed.

  At this time, in the discontinuous portion 45a on the inner wall surface of the through hole 42a, current does not flow through the seed layer 45, but current flows through the WSi film 44, which is the lower layer of the seed layer 45. For this reason, even if the discontinuous portion 45a is generated in the seed layer 45, the precipitation of Cu occurs in substantially the entire inner wall surface of the through hole 42a. Therefore, voids are less likely to occur in the wiring layer 46 formed in the through hole 42a. In other words, the embedding property of the wiring layer 46 is improved.

[Test example]
[Cu wiring embedding]
A plurality of holes having an opening diameter of 5.7 μm and a depth of 51 μm were formed on a silicon substrate having a diameter of 8 inches. Then, after supplying the H ₂ plasma and SiH ₄ gas to the silicon substrate while the silicon substrate is heated to 180 ° C., the WN film and the WSi film are sequentially formed using the ALD method. Formed. An insulating film is formed on the upper surface of the silicon substrate and the inner wall surface of the hole.

When supplying H ₂ plasma, the flow rate of H ₂ gas was 200 sccm, the pressure in the pretreatment chamber was 37 Pa, the high frequency power was 200 W, and the treatment time was 60 seconds. Further, when the supply of the SiH ₄ gas was the flow rate of SiH ₄ gas 70 sccm, the pressure in the vacuum chamber 21 Pa, the processing time of 60 seconds.

The WN film is supplied with WF ₆ gas, N ₂ gas, SiH ₄ gas, N ₂ gas, WF ₆ gas, N ₂ gas, NH ₃ gas, and N _A cycle consisting of supplying _two gases was repeated a plurality of times. When the supply of WF ₆ gas was 20sccm and the flow rate of the WF ₆ gas, 60 Pa pressure of the vacuum chamber, the treatment time is 2 seconds. SiH ₄ at the time of the supply of gas to the flow rate of SiH ₄ gas 70 sccm, the pressure in the vacuum chamber 70 Pa, and the processing time of 4 seconds. When the supply of the NH ₃ gas, the flow rate of NH ₃ gas 5 sccm, and the pressure in the vacuum chamber 10 Pa, the processing time and 2 seconds. When the supply of N ₂ gas was 400sccm flow rate of _{N 2} gas, 1.7 Pa pressure of the vacuum chamber, the treatment time is 2 seconds. As a result, a WN film having a thickness of 5 nm was formed on the upper surface of the silicon substrate and the inner wall surface of the hole.

The WSi film was formed by repeating a cycle of supplying WF ₆ gas, supplying N ₂ gas, supplying SiH ₄ gas, and supplying N ₂ gas a plurality of times. The supply of WF ₆ gas, the supply of SiH ₄ gas, and the supply of N ₂ gas were performed under the same conditions as when the WN film was formed. As a result, a WSi film having a thickness of 25 nm was formed on the WN film.
Next, a 500 nm Cu film was formed on the WSi film by sputtering, and a Cu wiring was formed by electrolytic plating.

  FIG. 5A is an SEM image obtained by imaging the cross-sectional structure of the Cu wiring thus formed. As shown in FIG. 5A, when the Cu wiring was formed after forming the WN film and the WSi film, it was recognized that no void was formed in the Cu wiring.

Also, after forming holes similar to the above in the 8-inch silicon substrate, the silicon substrate is heated to 180 ° C., and the H ₂ plasma and SiH ₄ gas are supplied to the silicon substrate. After that, only the WN film was formed using the ALD method. An insulating film is formed on the upper surface of the silicon substrate and the inner wall surface of the hole. The supply of H ₂ plasma, the supply of SiH ₄ gas, and the formation of the WN film were all performed under the same conditions as described above. Thereafter, a 500 nm Cu film was formed on the WN film by sputtering, and a Cu wiring was formed by electrolytic plating.

  FIG. 5B is an SEM image obtained by imaging the cross-sectional structure of the Cu wiring thus formed. As shown in FIG. 5B, it was recognized that when only a WN film was formed to form a Cu wiring, a void was formed in the Cu wiring.

  When the aspect ratio of the hole formed in the silicon substrate is larger than the above, or when the thickness of the WSi film formed on the silicon substrate is smaller than the above, the WSi film is formed on the WN film. However, voids may occur in the Cu wiring. However, even in such a case, it was recognized that voids are less likely to be formed and the embeddability of the Cu wiring is improved as compared with the case where the Cu wiring is formed without forming the WSi film. Further, the same result as described above was observed even when the formation target of the Cu wiring was a hole formed in the insulating film or a hole formed in the semiconductor substrate.

[Deposition rate of WN film and WSi film]
The film thickness when each of the WN film and the WSi film was formed under the above conditions was measured. In addition, about the WN film | membrane, the film thickness when repeating the said cycle 4 times, the film thickness when repeating 8 times, and the film thickness when repeating 12 times were measured. For the WSi film, the thickness when the above cycle was repeated 3 times and the thickness when the cycle was repeated 12 times were measured.

  The measurement results are shown in FIG. As shown in FIG. 6, it was recognized that the WN film was formed with a film thickness of about 0.4 nm per cycle, while the WSi film was formed with a film thickness of about 1 nm per cycle. In addition, when the WN film is formed, the time required for one cycle is 18 seconds. On the other hand, when the WSi film is formed, the time required for one cycle is 10 seconds. The WN film was found to be 1.2 nm and the WSi film was found to be 5 nm.

  As described above, when the WSi film is formed on the WN film, the number of processes constituting one cycle is increased although the number of films formed on the silicon substrate is increased to two types as compared with the case of forming only the WN film. The time required for one cycle and the number of gases necessary for film formation can be reduced, and the film formation rate per unit time can be increased. Therefore, even when the number of types of films formed on the silicon substrate is increased, it is possible to suppress the complexity of the formation method, the time required for the formation, and the increase in the cost for the formation. It can be said.

As described above, according to the embodiment, the effects listed below can be obtained.
(1) After the WN film 43 is formed on the substrate S, a WSi film 44 having a lower resistance than the WN film 43 is laminated on the WN film 43. For this reason, when the wiring layer 46 is formed by electrolytic plating, current flows more easily on the inner wall surface of the through hole 42a than when only the WN film 43 is formed. As a result, a region where no current flows is less likely to be generated on the inner wall surface of the through hole 42a, so that a void is less likely to occur in the wiring layer 46 formed in the through hole 42a. That is, the embedding property of the wiring layer 46 formed by electrolytic plating can be improved.

  (2) Since the seed layer 45 made of Cu is formed on the WSi film 44, current flows through the WN film 43, the WSi film 44, and the seed layer 45 during electroplating. As a result, voids are less likely to be formed in the wiring layer 46. In addition, since the WSi film 44 is formed as a lower layer of the seed layer 45, current flows through the WSi 44 film even when the seed layer 45 is not formed on the entire inner wall surface of the through hole 42a. As a result, voids are hardly formed in the wiring layer 46. Therefore, the seed layer 45 can be made thinner than when the seed layer 45 is formed directly on the WN film 43.

  (3) The WN film 43 and the WSi film 44 are formed by the ALD method. Therefore, compared with the case where the WN film 43 and the WSi film 44 are formed by, for example, sputtering, these films are more easily formed by the entire inner wall surface of the through hole 42a. Therefore, the embedding property of the wiring layer 46 formed by electrolytic plating can be improved.

  (4) The WN film 43 and the WSi film 44 are formed using the ALD method in which several atomic layers are formed on the substrate S. In this case, the WSi film 44 is formed by repeating the process of forming the WN film 43, excluding the second source gas supply process and the nitriding gas supply process. Therefore, according to the WSi film 44 laminated on the WN film 43, the embedding property of the wiring layer 46 can be improved, and several atomic layers can be formed with fewer steps.

In addition, the said embodiment can also be suitably changed and implemented as follows.
In the lower layer of the WSi film 44, not only the WN film 43 but also a TiN film or a TaN film that is a metal nitride film may be formed. Even if it is such a structure, the effect according to said (1)-(4) can be acquired.

  The seed layer 45 may not be formed on the WSi film 44. Even if it is such a structure, the effect according to said (1), (3), (4) can be acquired. Even when the wiring layer 46 is formed without forming the seed layer 45 in this way, the wiring layer is formed more than when the wiring layer 46 is formed on the WN film 43 as long as the WSi film 44 is formed. The embeddability of 46 is improved.

The WN film 43 and the WSi film 44 may be formed by a CVD method. Even if it is such a structure, the effect according to said (1) and (2) can be acquired.
The WN film 43 and the WSi film 44 may be formed by a film forming method other than the CVD method and the ALD method, for example, a sputtering method. Even in such a configuration, as compared with the case where only the WN film 43 is formed by the same formation method, the embedding property of the wiring layer 46 is improved by the amount of the WSi film 44 formed.

The formation of the WN film 43 may be performed by repeating the supply of WF ₆ gas, supply of N ₂ gas, supply of NH ₃ gas, and supply of N ₂ gas in this order. However, the reaction between WF ₆ and NH _3, the reaction between WF ₆ and SiH _4, and than the reaction between WF ₆ and NH _3, are required higher heat energy. Therefore, the temperature of the substrate S can be made lower when the WN film is formed by the method described in the above embodiment.

The formation of the WN film 43 is such that the supply of WF ₆ gas, supply of N ₂ gas, supply of SiH ₄ gas, supply of N ₂ gas, supply of NH ₃ gas, and supply of N ₂ gas are repeated in this order. May be performed. However, in order to nitride W formed by the reaction between WF ₆ and SiH ₄ with NH ₃ , the thermal energy is higher than when nitriding W with W (NH ₂ ) F ₅ described in the above embodiment. Needed. Therefore, the temperature of the substrate S can be made lower when the WN film is formed by the method described in the above embodiment.

The plasma generated from the H ₂ gas is supplied to the surface of the substrate S prior to the supply of the SiH ₄ gas, but the supply of the H ₂ plasma may be omitted. Further, both the supply of H ₂ plasma and the supply of SiH ₄ gas may be omitted.

The supply stop of SiH ₄ gas and the start of supply of WF ₆ gas in the silane gas supply process are performed at the same time, but supply of WF ₆ gas after a predetermined time after the supply of SiH ₄ gas is stopped. May be started.

The multi-chamber type film forming apparatus 10 may have a processing chamber other than the above, or may not have a seed layer forming chamber.
Although the pretreatment chamber 14 is provided separately from the film formation chamber 15, the film formation chamber 15 is provided with a high frequency power source, an H ₂ gas supply unit, or an Ar gas supply unit, so that Processing may be performed. In this case, the pretreatment chamber 14 can be omitted.

In the pretreatment chamber 14, H ₂ plasma or Ar plasma is formed using high frequency power having a frequency of 13.56 MHz. However, if it is possible to generate plasma from these gases, the high frequency power The frequency and the configuration of the pretreatment chamber 14 can be arbitrarily changed.

  The seed layer forming chamber 16 is not limited to the sputtering method, but may be a chamber for forming a Cu film by a film forming method such as a CVD method or a PVD method other than sputtering. When the Cu film is formed by the CVD method, the Cu film is more uniformly formed on the inner wall surface of the through hole 42a than when the Cu film is formed by the sputtering method. However, even when the CVD method is used, a Cu film is less likely to be formed near the bottom surface of the inner wall surface than the bottom surface of the through hole 42a. Therefore, by forming the WSi film, the wiring layer The embeddability of 46 is improved.

The silane gas supply unit 31 and the nitriding gas supply unit 32 of the film forming chamber 15 may be connected to different pipes.
The gas used in the silane gas supply step and the reducing gas supply step is not limited to SiH ₄ gas, but may be silane gas represented by Si _n H _{2n + 2} , such as disilane (Si ₂ H ₆ ) gas.

The exhaust of various gases performed after the first source gas supply step, the reducing gas supply step, the second source gas supply step, and the nitridation gas supply step is not limited to N ₂ gas, but other inert gases such as Ar Gas or helium gas may be used.

The gas used in the source gas supply process may be a gas containing W other than WF ₆ gas, for example, tungsten hexachloride, tungsten oxyhalides such as WOF ₂ , WOF ₄ , WOCl ₂ , and WOCl ₄ Good.

As the gas used in the nitriding gas supply step, a gas containing N other than NH ₃ gas, for example, hydrazine gas (N ₂ H ₄ ) or a hydrazine derivative gas in which hydrogen in hydrazine is substituted with a hydrocarbon group is used. You may do it. In short, any gas capable of nitriding W may be used.

-When WN film, WSi film, and WSiN film are formed, after WF ₆ gas, SiH ₄ gas, or NH ₃ gas is supplied to the substrate, the N ₂ gas is exhausted, but it is inactive Exhaust in the vacuum chamber 21 by only the exhaust part 25 may be performed without supplying gas.

The conditions such as the gas supply flow rate, the pressure in the processing chamber, and the processing time in each of the above steps can be arbitrarily changed as long as the WN film can be formed.
The inert gas supply unit 33 is N with respect to the vacuum chamber 21 when NH ₃ gas is supplied from the nitriding gas supply unit 32 and when WF ₆ gas is supplied from the source gas supply unit 35. _Two gases may be supplied. Thus, NH ₃ gas and WF ₆ gas is suppressed to flow back into silane gas pipe side.

The inert gas supply unit 34 is N _{2 with} respect to the vacuum chamber 21 when SiH ₄ gas is supplied from the silane gas supply unit 31 and when WF ₆ gas is supplied from the source gas supply unit 35. Gas may be supplied. Thus, SiH ₄ gas and WF ₆ gas is suppressed to flow back into the nitriding gas pipe side.

The inert gas supply unit 36 is N _{2 with} respect to the vacuum chamber 21 when SiH ₄ gas is supplied from the silane gas supply unit 31 and when NH ₃ gas is supplied from the nitriding gas supply unit 32. Gas may be supplied. Thus, SiH ₄ gas and NH ₃ gas is suppressed to flow back into the fluorine-based gas pipe GL2 side.

  The insulating film included in the substrate S is not limited to a silicon oxide film, and may be a silicon nitride film and a metal boron oxide. Examples of the metal boron oxide include ZrBO, TaBO, TiBO, and HfBO.

  The semiconductor substrate constituting the substrate S may be a semiconductor substrate other than the silicon substrate.

  DESCRIPTION OF SYMBOLS 10 ... Multi-chamber type film-forming apparatus, 11 ... Transfer chamber, 11a ... Transfer robot, 12a ... Loading chamber, 13 ... Unloading chamber, 14 ... Pretreatment chamber, 15 ... Film-forming chamber, 16 ... Seed layer chamber, 21 ... Vacuum Tank, 21a ... Bottom wall, 21b ... Upper wall, 22 ... Substrate stage, 23 ... Heater, 24 ... Heater power supply, 25 ... Exhaust part, 26 ... Shower plate, 26a ... Opening part, 31 ... Silane gas supply part, 32 ... Nitriding Gas supply unit 33, 34, 36 ... inert gas supply unit, 35 ... source gas supply unit, 41, 51 ... semiconductor substrate, 42, 52 ... insulating film, 42a, 52a ... through hole, 43, 53 ... WN film 44 ... WSi film, 45, 54 ... seed layer, 46,55 ... wiring layer, GL1 ... hydrogen gas pipe, GL2 ... fluorine gas pipe, P1 ... exhaust port, P2 ... gas supply port , S ... substrate.

Claims (4)

A metal nitride film forming step in which a metal nitride film made of a nitride of tantalum, titanium, and tungsten is formed on a substrate having a recess;
A tungsten silicide film forming step in which a tungsten silicide film is laminated on the metal nitride film;
A wiring structure forming method comprising: a wiring forming step in which a wiring layer made of copper is formed by electrolytic plating in the recess in which the metal nitride film and the tungsten silicide film are formed. Between the tungsten silicide film forming step and the wiring forming step,
The method for forming a wiring structure according to claim 1, further comprising a seed layer forming step in which a seed layer made of copper is formed on the tungsten silicide film. In the metal nitride film forming step and the tungsten silicide film forming step,
The method for forming a wiring structure according to claim 1, wherein the metal nitride film and the tungsten silicide film are formed by one of a CVD method and an ALD method. In the metal nitride film forming step and the tungsten silicide film forming step, the metal nitride film and the tungsten silicide film are formed by the ALD method,
In the metal nitride film forming step,
A first source gas supply step in which a source gas containing tungsten is supplied to the substrate;
A reducing gas supply step in which a reducing gas for reducing the source gas is supplied to the substrate;
A second source gas supply step in which the source gas is supplied to the substrate;
A nitriding gas supply step in which a nitriding gas for nitriding tungsten is supplied to the substrate is repeated in this order to form a tungsten nitride film,
In the tungsten silicide film forming step,
A source gas supply step in which the source gas is supplied to the substrate;
The method for forming a wiring structure according to claim 3, wherein the reducing gas supply step is repeated in this order.