JP4537721B2 - Deposition method - Google Patents

Description

  The present invention relates to a film forming method. More specifically, the present invention relates to a method for forming a thin film containing a metal over a substrate in which a conductive substance and an insulating substance are mixed.

In recent semiconductor devices, the delay of signal propagation in the wiring determines the element operation. Therefore, it is necessary to reduce the RC delay in the wiring in order to increase the device operation speed. For this reason, it is conceivable to use a low dielectric constant (Low-k) insulating film having a dielectric constant lower than that of SiO ₂ which is a conventional insulating film material, and a low resistivity as a wiring material. It is contemplated to use materials.

  Currently, as a wiring material having a low resistivity, application of Cu or a Cu alloy is specifically studied. Cu has a specific resistance of about 35% lower than Al conventionally used as a wiring material and also has a high electromigration resistance. Therefore, a highly reliable wiring material in a highly integrated semiconductor device. As expected.

  In the case of using Cu as a wiring, from the viewpoints of preventing diffusion of Cu into the insulating film, improving adhesion with the insulating film, preventing progress of oxidation into the insulating film, etc., between the insulating film and Cu. A means for forming a barrier metal film is frequently used. In general, a single-layer film or a laminated film of Ta, TaN or the like is used as the barrier metal film, and a sputtering method is used as the film formation method.

  However, the presence of the barrier metal film at the bottom of the via, for example, reduces the electromigration reliability of the wiring. Here, electromigration is a phenomenon in which Cu and electrons diffuse in the direction of electrons when Cu and electrons exchange momentum when a high-density current is passed through the wiring. That is, since the barrier metal film is present at the bottom of the via, this diffusion is interrupted, so that Cu vacancies are easily formed.

  In general, the resistance is higher than that of Cu, resulting in an increase in via resistance. In particular, the barrier metal film formed by sputtering is easily formed thick at the bottom of the via, and therefore the via resistance tends to be high.

  In order to solve such a problem, a method of forming a wiring structure having no barrier metal film at the bottom of the via is considered. When this wiring structure is formed, only the barrier metal film at the bottom of the via is selectively removed after the barrier metal film is formed. Then, Cu is buried with the lower layer wiring exposed at the bottom of the via. Here, as a method of removing the barrier metal film at the bottom of the via, a technique of removing the barrier metal film by ion irradiation such as reverse sputtering is used (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 11-220023

  However, when forming the Cu wiring by the dual damascene method, it is difficult to etch away only the barrier metal film at the bottom of the via by ion irradiation. That is, in the dual damascene method, the barrier metal film is formed after the via and the trench are formed. Therefore, when removing the barrier metal film, the barrier metal film exposed to the bottom of the trench is removed simultaneously with the bottom of the via. May also be removed.

  Further, when a technique such as reverse sputtering is used for removing the barrier metal film at the bottom of the via, Cu used for the lower layer wiring is sputtered simultaneously. The sputtered Cu may be implanted into a portion where the barrier metal film at the bottom of the via is thin to deteriorate the wiring characteristics.

  Furthermore, as described above, when only the barrier metal film at the bottom of the via is selectively removed after the barrier metal film is formed, it is necessary to perform ion irradiation after forming the mask, which increases the number of processes, It is conceivable to reduce the productivity of the semiconductor device.

  The present invention solves the above-described problems and provides a film forming method in which a barrier metal film is selectively formed only on a portion in contact with an insulating film.

A film forming method of the present invention is a film forming method for selectively forming a film containing a metal only on the insulating material of a sample substrate in which a conductive material and an insulating material are mixed.
An organic compound adsorption step of adsorbing an organic compound on the conductive material;
An organometallic compound adsorption step of adsorbing the organometallic compound containing the metal on the insulating material;
The conductive material of the organic compound adsorbed onto desorbed, and the insulating said material on adhering to by reducing organometallic compound to deposit a film containing the metal, a reducing agent supplying a reducing agent A supply process;
Is provided.

  In this invention, an organic compound and an organometallic compound are sequentially supplied to a sample substrate in which a conductive substance and an insulating substance are mixed. Thereby, an organic compound can be adsorbed on the conductive material, and an organometallic compound can be adsorbed on the insulating material. Thereafter, a film containing a metal can be deposited only on the insulating material by supplying the reducing agent. Therefore, a metal-containing film can be selectively formed only on the insulating material by this method.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

  In this invention, vapor phase monoatomic layer growth is performed by repeatedly forming a single layer film of metal or metal compound atoms or molecules on a sample substrate to form a metal or metal compound film having a desired film thickness. A metal or metal compound film having a conductivity lower than that of the conductive material on the sample substrate is formed.

  Specifically, an organic compound is first supplied onto a sample substrate in which a conductive material and an insulating material are mixed. As a result, the organic compound is adsorbed only on the conductive material. Here, the organic compound is adsorbed only on the conductive substance because it is easy to exchange electrons with the conductive substance.

  Next, an organometallic compound containing a metal element is supplied. Here, as the organic compound to be supplied first, an organic compound having low reactivity with an organic substance composed of an element excluding a metal contained in the organometallic compound is used. By adsorbing such an organic compound on the conductive material in advance, even if the organometallic compound is supplied, it does not adsorb on the conductive material, but only on the insulating material. Can be adsorbed.

  Thereafter, a reducing agent is supplied. The reducing agent used here desorbs the organic compound adsorbed on the conductive substance, reduces the organometallic compound adsorbed on the insulating substance, and deposits the substance containing the metal element contained in the organometallic compound. To do. Thus, a single layer film made of a compound containing a metal element is formed only on the insulating material. By repeating such steps, a metal-containing film can be formed only on the insulating material.

Embodiment 1 FIG.
FIG. 1 is a schematic cross-sectional view for explaining a sample substrate formed by the film forming method according to Embodiment 1 of the present invention.
As shown in FIG. 1, in the sample substrate in the first embodiment, a Cu film 4 and a Si oxide film 6 are formed on a Si substrate 2. On the Si oxide film 6, a TaN film 8 having a thickness of about 1 nm is formed.

FIG. 2 is a flowchart for explaining the film forming method according to Embodiment 1 of the present invention. 3 to 6 are schematic cross-sectional views for explaining states in the film forming process according to the first embodiment of the present invention.
Hereinafter, a film forming method according to Embodiment 1 of the present invention will be described with reference to FIGS.

  As shown in FIG. 3, in the sample substrate, on the Si substrate 2, a Cu film 4 is formed as a conductive material, and a Si oxide film 6 is formed as an insulating material. Such a sample substrate is maintained at a temperature of about 150 to 350 degrees.

Here, dimethylamine (HN _{(CH 3) 2)} and the argon (Ar), to supply about 0.2 to about 1 second (step S2). Thereby, as shown in FIG. 4, the methylamino group (NC ₂ H ₅ ) 12 is selectively adsorbed only on the Cu film 4. Here, it adsorbs only on the Cu film 4 because it is easy to exchange electrons with Cu, which is a conductive material. Thereafter, only argon is supplied for about 0.2 to about 1 second to remove excess dimethylamine on the sample substrate (step S4).

Next, pentadimethylamino tantalum (Ta [N (CH ₃ ) ₂ ] ₅ ) and argon are supplied for about 0.2 to about 1 second (step S6). At this time, the temperature of the raw material to be supplied is about 60 to 100 degrees. As a result, as shown in FIG. 5, the compound 14 containing Ta and N (CH ₃ ) ₂ is adsorbed only on the Si oxide film 6. Since the methylamino group 12 having low reactivity with pentadimethylaminotantalum is adsorbed on the Cu film 4, it is not adsorbed on the Cu film 4. Thereafter, argon alone is supplied for about 0.2 to about 1 second to remove excess pentadimethylamino tantalum on the sample substrate (step S8).

Next, as shown in FIG. 6, ammonia (NH ₃ ) 16 is supplied for about 0.2 to about 1 second (step S10). The ammonia 16 supplied here reacts with the compound 14 containing Ta and N (CH ₃ ) ₂ adsorbed on the Si oxide film 6 to precipitate TaN. On the other hand, the methylamino group 12 adsorbed on the Cu film 4 is desorbed. Thereby, the thin TaN film 8 at the atomic single layer level can be formed only on the Si oxide film 6. Thereafter, argon is supplied for about 0.2 to about 1 second to remove excess ammonia 16 (step S12).

As described above, supply of dimethylamine and argon (step S2), supply of argon (step S4), supply of pentadimethylaminotantalum and argon (step S6), supply of argon (step S8), supply of ammonia (step) S10), by repeating the cycle consisting of argon supply (step S12) about 10 to 50 times, a single TaN film is formed to overlap, and a TaN film 8 having a thickness of about 1 nm is formed by Si oxidation. It can be formed only on the film 6.

As described above, according to the first embodiment, first, dimethylamine, which is an organic compound, is supplied to a sample substrate to adsorb the ethylamino group 12. Thereby, pentadimethylamino tantalum, which is an organometallic compound to be supplied next, does not adsorb on the Cu film 4 but adsorbs only on the Si substrate 6. Therefore, even if ammonia is subsequently supplied, no metal compound is deposited on the Cu film 4, and a TaN film can be formed only on the Si oxide film 6.

  Further, according to the method described in the first embodiment, the film can be selectively formed only on the Si oxide film 6 which is an insulating film without performing reverse sputtering by ion irradiation. Therefore, the TaN film can be formed more reliably and easily.

In the first embodiment, the case where dimethylamine is used has been described. However, in the present invention, the material used as the organic compound is not limited to dimethylamine. For example, ethyl azide (C ₂ H ₅ N ₃ ), dimethylhumanrazine (H ₂ NN (CH ₃ ) ₂ ), diethylamine (HN ( C ₂ H _{5) 2),} trimethylamine _{(N (CH 3) 3)} , triethylamine _{(N (C 2 H 5)} 3), trimethylsilane _{(HSi (CH 3) 3)} , tetramethylsilane (Si _(CH 3) ₄ ), triethylsilane (HSi (C ₂ H ₅ ) ₃ ), tetraethylsilane (Si (C ₂ H ₅ ) ₄ ), or other organic compounds may be used.

In the first embodiment, the case where pentadimethylaminotantalum is used as the organometallic compound has been described. However, in the present invention, the organometallic compound is not limited to this. For example, terbutylimide trisdimethylamido tantalum ([C ₂ H ₅ ] ₂ N) ₃ TaN (C ₄ H ₉ )), pentadiethylamino tantalum _{(Ta [N (C 2 H} 5) 2] 5) or the like, may be those with other organometallic compounds.

In the first embodiment, the case where the TaN film 8 is formed has been described. However, in the present invention, the film containing metal is not limited to the TaN film, and may be a film containing other metal. In this case, an organometallic compound containing another metal may be supplied. Specifically, for example, the metal contained in the organometallic compound may be Ti, Zr, or the like in addition to tantalum (Ta). That is, in this case, TiN, ZrN, or the like can be formed on the insulating film. The organometallic compound containing Ti is not necessarily limited to this. For example, tetrakisdimethylaminotitanium (Ti [N (CH ₃ ) ₂ ] ₄ ) or tetrakisdiethylaminotitanium (Ti [N (C ₂ H ₅ ) ₂ ] ₄ ) etc. are conceivable. In addition, the organometallic compound containing Zr is not necessarily limited to this, but tetrakisdimethylaminozirconium (Zr [N (CH ₃ ) ₂ ] ₄ ) or tetrakisdiethylaminozirconium (Zr [N (C ₂ H _5). ) ₂ ] ₄ ) etc. are conceivable.

In the first embodiment, the case where ammonia is used as the reducing agent has been described. However, in this invention, the reducing agent is not limited to ammonia. In the present invention, the reducing agent may be any agent that desorbs the organic compound adsorbed on the conductive substance and deposits the metal-containing substance by reducing the organometallic compound adsorbed on the insulating substance. For example, it is conceivable to use hydrazine (N ₂ H ₄ ) or a hydrogen radical in addition to ammonia. Although not necessarily limited to this, when hydrogen radicals are used, it is conceivable to supply the reducing agent using, for example, He / H ₂ plasma.

  In the first embodiment, the case where the Cu film 4 is formed as the conductive material and the Si oxide film 6 is formed as the insulating material on the sample substrate has been described. However, in the present invention, the sample substrate is not limited to this, and may be a mixture of another conductive substance and another insulating substance.

  In the present invention, the film formation conditions such as the film formation temperature are not limited to the conditions described in the first embodiment. However, for example, when supplying an organic compound or an organometallic compound, it is preferable to maintain the temperature at such a level that precipitation due to a thermal decomposition reaction does not occur. Moreover, in Embodiment 1, the case where each process (steps S2-S12) for TaN film formation was repeated about 10 to 50 times was demonstrated. However, the present invention is not limited to this. The number of repetitions may be appropriately determined in consideration of the temperature and the film thickness to be formed.

Embodiment 2. FIG.
FIG. 7 is a schematic sectional view for illustrating the semiconductor device according to the second embodiment of the present invention.
As shown in FIG. 7, the semiconductor device formed in Embodiment 2 has a wiring structure formed by a dual damascene method. In the second embodiment, when the barrier metal film is formed in this wiring structure, the film forming method according to the present invention is applied.

  As shown in FIG. 7, in the semiconductor device of the second embodiment, a Cu wiring 24 is formed on the substrate 22. A gate electrode, an interlayer insulating film, a wiring layer, etc. (not shown) are formed on the substrate 22 as necessary. A low dielectric constant film 26 is formed on the substrate 22. In addition, a Cu wiring 28 that penetrates the low dielectric constant film 26 and is connected to the Cu wiring 24 is formed in the low dielectric constant film 26. The Cu wiring 28 has a dual damascene structure. That is, in the Cu wiring 28, a TiN film 34 is formed inside the via 30 and the groove 32 formed so as to penetrate the low dielectric constant film 26, and Cu 38 is embedded using the Cu seed film 36 as a seed film. Configured.

FIG. 8 is a flowchart for explaining the method for manufacturing a semiconductor device in the second embodiment. 9 to 13 are schematic cross-sectional views for explaining states in the manufacturing process of the semiconductor device of the second embodiment.
A method for manufacturing a semiconductor device according to the second embodiment of the present invention will be described below with reference to FIGS.

  First, as shown in FIG. 9, a low dielectric constant film 26 is formed on a substrate 22 on which a Cu wiring 24 is formed, and vias 30 and grooves are exposed on the low dielectric constant film 26 so that the surface of the Cu wiring 24 is exposed. 32 is formed (step S22).

Next, the substrate 22 is maintained at a temperature of about 150 to 350 degrees, and dimethylamine (HN (CH ₃ ) ₂ ) and nitrogen (N ₂ ) are supplied (step S24). As a result, as shown in FIG. 10, the methyl groups 42 are thinly adsorbed on the surface of the Cu wiring 24 exposed at the bottom of the via 30 at the monomolecular layer level. Thereafter, nitrogen is supplied to remove excess dimethylamine (step S26).

Next, tetrakisdimethylaminotitanium (Ti [N (CH ₃ ) ₂ ] ₄ ) and nitrogen are supplied (step S28). Here, the raw material is heated to about the same temperature as room temperature to about 50 degrees and supplied together with nitrogen (bubbling), or is supplied by liquid conveyance supply using a vaporizer. As a result, as shown in FIG. 11, the compound 44 containing Ti and (C ₂ H ₅ ) ₂ is thinned at the monomolecular layer level on the exposed portion of the low dielectric constant film 26 including the inner walls of the via 30 and the groove 32. Adsorb. At this time, since dimethylamine 42 is adsorbed on the bottom of the via 30, tetramethylaminotitanium is not adsorbed on the bottom of the via 30. Thereafter, nitrogen is supplied to remove excess tetrakisdimethylaminotitanium (step S30).

Next, as shown in FIG. 12, ammonia (NH ₃ ) 46 is supplied (step S32). Thereby, the ammonia 46 reduces the compound 44 containing Ti and (C ₂ H ₅ ) ₂ adsorbed on the surface of the low dielectric constant film 26, and precipitates TiN. Thereby, a thin TiN film at the molecular layer level is formed on the exposed portion of the low dielectric constant film 26 including the via 30 and the inner wall of the groove 32. At this time, the methyl group 42 adsorbed on the bottom of the via 30 is desorbed by the ammonia 46. Thereafter, nitrogen is supplied to remove excess ammonia (step S34).

  Thereafter, until the TiN film reaches the required thickness as a barrier metal film, a monolayer TiN film forming process as described above, that is, supply of dimethylamine and nitrogen, supply of nitrogen, tetrakisdimethyl The steps of supplying aminotitanium and nitrogen, supplying nitrogen, supplying ammonia, and supplying nitrogen (steps S24 to S34) are repeated.

After the TiN film 34 is formed to a desired thickness, a Cu seed film 36 is formed as shown in FIG. 13 (step S36). Thereafter, Cu 38 is embedded by electrolytic plating using the Cu seed film 36 as a seed film (step S38). Further, planarization by CMP (Chemical Mechanical Polishing) is performed (step S40), and a wiring structure having a dual damascene structure as shown in FIG. 7 is formed.
Thereafter, if necessary, an insulating film, a wiring, and the like are formed to form a semiconductor device having a multilayer wiring structure.

As described above, in the second embodiment, first, dimethylamine 42 is adsorbed only on the Cu wiring as the organic compound. Thereby, the compound 44 containing Ti and (C ₂ H ₅ ) ₂ supplied later is not adsorbed on the Cu wiring 24 but adsorbed only on the portion where the low dielectric constant film 26 is exposed. Therefore, after that, even if ammonia is supplied as a reducing agent, the TiN film is deposited only on the surface of the low dielectric constant film 26. Therefore, Cu can be embedded on the Cu wiring 24 without forming a barrier metal film (TiN film 34). That is, at the bottom of the via 30, the Cu wiring 24 that is the lower layer wiring and the Cu embedded in the via 30 are in direct contact. Therefore, it is possible to obtain a highly reliable wiring structure in which deterioration of the wiring shape due to electromigration is suppressed.

  In the second embodiment, the barrier metal film is not removed by reverse sputtering as in the prior art. Therefore, the TiN film 34 is formed on the low dielectric constant film 26 exposed at the bottom of the trench 32, and can be directly functioned as a barrier metal film without being removed. Therefore, the diffusion of Cu into the low dielectric constant film 26 at the bottom of the groove 32 can be suppressed.

  Further, in the second embodiment, it is not necessary to perform a removal process of the barrier metal film at the via bottom by reverse sputtering after the barrier metal film is formed. Accordingly, the productivity of the semiconductor device can be improved.

  In the second embodiment, the case where the TiN film 34 is formed as the barrier metal film has been described. However, in the present invention, the barrier metal film is not limited to the TiN film, and may be, for example, a TaN film, a ZrN film, or the like. The barrier metal film is not limited to a single layer film of a metal compound, and may have a laminated structure such as Ta and TaN, Ti and TiN, and Zr and ZrN. Note that descriptions of the organometallic compound, the organic compound, the reducing agent, and the like used when forming the barrier metal film are the same as those described in Embodiment 1, and thus the description thereof is omitted.

  In the second embodiment, the case where the Cu wiring 28 having the dual damascene structure is formed has been described. If the method described in the second embodiment is used, a barrier metal film is reliably formed also on the low dielectric constant film 26 exposed at the bottom of the trench 32, while a barrier metal film is formed at the bottom of the via 30. You can avoid it. Therefore, it is particularly effective for improving the wiring characteristics by the dual damascene method. However, the present invention is not used only in the dual damascene method, and when it is necessary to form a thin film having a metal only on an insulating material on a substrate in which a conductive material and an insulating material are mixed, Can be applied.

In the second embodiment, the case where the electrolytic plating method using the Cu seed film 36 as an electrode is used when Cu 38 is embedded in the formation of the Cu wiring 28 has been described. However, in the present invention, the Cu 38 burying method is not limited to this. For example, the Cu 38 may be buried by electroless plating without forming the Cu seed film 36.
Others are the same as those in the first embodiment, and thus description thereof is omitted.

  For example, the Cu film 4 and the Cu wiring 24 in the first and second embodiments correspond to the conductive material of the present invention, and the Si oxide film 6 and the low dielectric constant film 26 correspond to the insulating material. Further, the TaN film 8 and the TiN film 34 in the first and second embodiments correspond to the film containing metal in the present invention.

  Further, for example, the organic compound adsorption process of the present invention is executed by executing steps S2 and S24 in the first and second embodiments, and the organometallic compound adsorption process of the present invention is performed by executing steps S6 and S28. Is executed, and the reducing agent supply process of the present invention is executed by executing steps S10 and S32.

It is a cross-sectional schematic diagram for demonstrating the thin film formed in Embodiment 1 of this invention. It is a flowchart for demonstrating the film-forming method in Embodiment 1 of this invention. It is a cross-sectional schematic diagram for demonstrating the state in the film-forming process in Embodiment 1 of this invention. It is a cross-sectional schematic diagram for demonstrating the state in the film-forming process in Embodiment 1 of this invention. It is a cross-sectional schematic diagram for demonstrating the state in the film-forming process in Embodiment 1 of this invention. It is a cross-sectional schematic diagram for demonstrating the state in the film-forming process in Embodiment 1 of this invention. It is a cross-sectional schematic diagram for demonstrating the semiconductor device in Embodiment 2 of this invention. It is a flowchart for demonstrating the film-forming method in Embodiment 2 of this invention. It is a cross-sectional schematic diagram for demonstrating the state in the manufacture process of the semiconductor device in Embodiment 2 of this invention. It is a cross-sectional schematic diagram for demonstrating the state in the manufacture process of the semiconductor device in Embodiment 2 of this invention. It is a cross-sectional schematic diagram for demonstrating the state in the manufacture process of the semiconductor device in Embodiment 2 of this invention. It is a cross-sectional schematic diagram for demonstrating the state in the manufacture process of the semiconductor device in Embodiment 2 of this invention. It is a cross-sectional schematic diagram for demonstrating the state in the manufacture process of the semiconductor device in Embodiment 2 of this invention.

Explanation of symbols

2 Si substrate 4 Cu film 6 Si oxide film 8 TaN film 12 Methylamino group 14 Compound containing Ta and N (CH3) 2 16 Ammonia 22 Substrate 24 Cu wiring 26 Low dielectric constant film 28 Cu wiring 30 Via 32 groove 34 TiN film 36 Cu seed film 38 Cu
42 Methyl group 44 Compound containing Ti and N (C ₂ H ₅ ) ₂ 46 Ammonia

Claims (6)

In a film forming method for selectively forming a film containing a metal only on the insulating material of the sample substrate in which a conductive material and an insulating material are mixed,
An organic compound adsorption step of adsorbing an organic compound on the conductive material;
An organometallic compound adsorption step of adsorbing the organometallic compound containing the metal on the insulating material;
The conductive material of the organic compound adsorbed onto desorbed, and the insulating said material on adhering to by reducing organometallic compound to deposit a film containing the metal, a reducing agent supplying a reducing agent A supply process;
A film forming method comprising: 2. The film forming method according to claim 1, wherein an organic substance composed of an element excluding the metal contained in the organometallic compound has low reactivity with the organic compound.   The organic compound includes any one of dimethylamine, diethylamine, trimethylsilane, tetramethylsilane, triethylsilane, tetraethylsilane, ethyl azide, dimethylhumanrazine, trimethylamine, or triethylamine. 2. The film forming method described in 1. The film forming method according to claim 1, wherein the metal contains any one of titanium, zirconium, and tantalum . The organometallic compound comprises pentamethylene dimethylamino tantalum, Tel butylimido tris diethylene methylamide tantalum, penta diethylamino tantalum, tetrakis (dimethylamino) titanium, tetrakis (diethylamino) titanium, tetrakis (dimethylamino) zirconium, or any of tetrakis (diethylamino) zirconium The film forming method according to claim 4.   The film forming method according to claim 1, wherein the reducing agent includes ammonia, hydrazine, or hydrogen radicals.

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