JP2012114208A - Method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent galvanic corrosion on the surface of a copper film due to exposure to water during conveyance of a wafer on which copper interconnections are formed after CMP polishing.SOLUTION: Surface of a copper film 3 is changed to cuprous oxide (CuO)5 insoluble to water by polishing the wafer surface by using a cleaning agent having pH adjusted to 7-12 immediately after a barrier metal film polishing process in the Cu-CMP process when copper interconnections are formed, and an antioxidation film 6 is formed by making an oxidation inhibitor adhere to the surface of CuO5.

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a process for preventing corrosion of copper wiring after CMP.

  Conventionally, aluminum has been used as a wiring material in a semiconductor device such as a large-scale integrated circuit (LSI). However, in order to obtain a finer, faster, and lower power consumption semiconductor device, a low resistance copper wiring is used. It is becoming used.

  However, since copper is difficult to dry-etch like aluminum, a copper wiring forming method called a damascene method has been established. In the damascene method, a trench is formed in the interlayer insulating film, a barrier metal film for preventing copper diffusion, and further copper (Cu) is formed, and the surplus on the interlayer insulating film is formed by a chemical mechanical polishing (CMP) method. A method of removing the copper and barrier metal film is employed.

  In CMP at the time of copper wiring formation (hereinafter referred to as Cu-CMP), a Cu-BTA film is conventionally formed on a copper surface using a polishing slurry containing a corrosion inhibitor such as benzotriazole (BTA). Surface corrosion is suppressed, and dishing due to etching of the copper film during barrier metal film polishing is prevented. In addition, a slurry containing a readily water-soluble corrosion inhibitor such as a hydroxyalkyl group-containing benzotriazole (HA-BTA) compound described in Patent Document 1 has a polishing rate in low-pressure polishing as compared with conventional BTA. It has been shown to be excellent.

JP 2005-175218 A

The structure immediately after polishing the barrier metal film is as shown in FIG. By polishing with the above slurry, it has a structure of an interlayer insulating film (oxide film) 1, a barrier metal film 2, and a Cu film 3, and the surface of the Cu film 3 is an anticorrosive film 4 (actually a Cu-BTA complex). Covered with. However, with a water-soluble corrosion inhibitor such as H-BTA, the anticorrosion film 4 is dissolved when water is applied during the conveyance after wafer polishing, and the anticorrosion effect is reduced. As a result, a potential difference is generated between the barrier metal film 2 and the Cu film 3, the anticorrosion film 4 at the interface is broken, and is eluted from the surface of the Cu film 3 as Cu ²⁺ . Furthermore, elution progresses, and there is a problem that galvanic corrosion of the Cu film 3 proceeds as shown in FIG.

Immediately after the barrier metal film polishing step in the Cu-CMP step during copper wiring formation, the surface of the copper film is polished with a cleaning agent having a pH adjusted to 7 to 12 so that the copper film surface is insoluble in water. By changing to copper (Cu ₂ O) and attaching the above-mentioned antioxidant to the Cu ₂ O surface, a means for preventing corrosion of the barrier metal film and the copper film interface due to water being conveyed is provided.

That is, according to one embodiment of the present invention,
Forming a wiring trench in an interlayer insulating film on a semiconductor substrate;
Forming a barrier metal film and a copper film;
Polishing a copper film and a barrier metal film by a chemical mechanical polishing method to expose the interlayer insulating film and embedding the copper film and the barrier metal film in the wiring groove;
In a method for manufacturing a semiconductor device comprising steps of cleaning and drying a semiconductor substrate,
Immediately after polishing the barrier metal film, the surface of the semiconductor substrate is polished using a cleaning agent having a pH adjusted to 7 to 12 to change the copper film surface to cuprous oxide, and to the cuprous oxide surface. A method of manufacturing a semiconductor device is provided, wherein a film of the antioxidant is formed.

According to one embodiment of the present invention, the corrosion of the barrier metal film and the copper film interface due to water being transported is formed by forming a water-insoluble Cu ₂ O film instead of the anticorrosion film on the surface of the copper film after CMP. Product yield can be improved.

It is the schematic for demonstrating the subject of this invention. It is a process flowchart explaining the Cu-CMP process of this invention and a prior art. It is a schematic sectional drawing which shows the surface state change of Cu film | membrane by Cu-CMP based on this invention. It is an electrogram of copper and a copper compound. It is the schematic which shows the structure of CMP apparatus.

  Hereinafter, the present invention will be described with reference to embodiments, but the present invention is not limited thereto.

  The formation of fine copper wirings used in semiconductor devices is formed by a damascene method because it is difficult to pattern by copper dry etching. In the damascene method, as described above, in the damascene method, a wiring trench is formed in an interlayer insulating film, a barrier metal film for preventing copper diffusion is formed, and then a copper (Cu) film is formed, and chemical mechanical polishing (CMP) is performed. The excess copper and barrier metal film on the interlayer insulating film are removed by a polishing method.

  FIG. 2 is a polishing process flow of Cu-CMP. Usually, as surrounded by a broken line, the wafer flows in the order of a) Cu polishing, b) barrier polishing, c) cleaning, and d) drying. In the present invention, e) cleaning is performed immediately after b).

  The a) Cu polishing and b) barrier polishing can be performed by a conventionally known method.

FIG. 3 is a schematic cross-sectional view showing changes in the surface state of the Cu film by Cu-CMP according to the present invention. As shown in FIG. 3A, the surface of the Cu film 3 immediately after the polishing of the barrier metal film 2 is the anti-corrosion film in the structure of the interlayer insulating film (oxide film) 1, the barrier metal film 2, and the Cu film 3. It is covered with (Cu-BTA) 4, which is the same as the conventional one. Thereafter, when polishing with the cleaning agent according to the present invention is performed on the polishing pad, the anticorrosion film 4 on the surface is removed as shown in FIG. 3B, and in this case, in an alkaline solution having a pH of 7 to 12 In order to stabilize with Cu ₂ O as shown in the potential diagram of FIG. 4, a Cu ₂ O film 5 is formed on the outermost surface. In FIG. 4, the horizontal axis represents pH, and the vertical axis represents oxidation-reduction potential (V vs. NHE: relative value). Furthermore, the Cu surface can be covered with the antioxidant film 6 as shown in FIG. As the potential diagram shown in FIG. 4, for Cu 2 _O is stable in PH7～12 (insoluble), it is possible to prevent galvanic corrosion due to the pure water is applied.

  As the cleaning agent used in the present invention, one having a pH in the range of 7 to 12 is used, for example, including a metal chelating agent and an antioxidant, and water or water and a water-soluble organic solvent (for example, alcohols) as a solvent ) And a solvent containing a mixed solvent.

  Any metal chelating agent can be used as long as it can form a chelate with copper. Examples thereof include various organic acid salts used in abrasives.

Examples of the antioxidant include secondary organic amines, tertiary organic amines, and quaternary organic ammonium salts. Secondary organic amines include dialkylamines such as dimethylamine and diethylamine, diethanolamine, 2- (ethylamino) ethanol, 2- (methylamino) ethanol, N-methyldiethanolamine, and alkanolamines such as dimethylaminoethanol. Can be mentioned. Examples of tertiary organic amines include trialkylamines such as trimethylamine, triethylamine, and dimethylethylamine, and alkanolamines such as triethanolamine. Examples of the quaternary organic ammonium salt include salts such as tetramethylammonium ((CH ₃ ) ₄ N ⁺ ) and choline ((CH ₃ ) ₃ N ⁺ CH ₂ CH ₂ OH).

  Furthermore, in order to adjust pH to 7-12, a cleaning agent contains a pH adjuster. Since the secondary organic amine, tertiary organic amine or quaternary organic ammonium salt used as the antioxidant exhibits alkalinity, various acids can be used as the pH adjuster, and organic acids, particularly lactic acid is preferred.

Each component in the cleaning agent may have any composition ratio as long as the Cu ₂ O film 5 can be formed in a desired film thickness in the range of pH 7-12. Moreover, if the range of pH is said range, the commercially available cleaning agent for CMP can also be used.

Polishing with a cleaning agent is performed immediately after the normal CMP barrier metal film polishing step. At this time, the polishing with the cleaning agent may be performed by another CMP apparatus as long as galvanic corrosion does not occur. However, it is preferable to continue the CMP barrier metal film polishing process using the same CMP apparatus. FIG. 5 is a view showing an outline of a general CMP apparatus. A polishing pad 11 is installed on a platen 10 which is a polishing surface plate. A semiconductor substrate 12 to be polished has a polishing surface on a pressure head 13. It is installed so as to face the polishing pad 11. The platen 10 and the pressure head 13 are rotated in the same direction, and in the CMP process, polishing slurry is applied to the polishing pad 11 from the abrasive nozzle 14 to perform polishing. Further, in the polishing step using the cleaning agent, the cleaning agent is applied to the polishing pad 11 from the cleaning agent nozzle 15 to remove the anticorrosion film formed on the surface of the Cu film and simultaneously form the Cu ₂ O film.

In polishing using a cleaning agent, the Cu ₂ O film 5 having a thickness sufficient to prevent galvanic corrosion of the Cu film 3 may be formed.

Thereafter, as in the conventional case, pure water cleaning and drying are performed, and the processed substrate is subjected to the next step. For example, in the case of forming a multilayer wiring, an interlayer insulating film can be further formed on the copper wiring, and similarly, a second copper wiring can be formed. The Cu ₂ O film 5 on the Cu film 3 can be formed on the Cu ₂ O film 5 as it is without being removed, and may be removed as necessary when a contact is formed.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited only to these Examples.

Example After forming the TaN barrier film and the copper film by the damascene method, the copper film polishing and the barrier film polishing were performed by a conventional method, and then polishing using a commercially available cleaning agent was performed. The polishing slurry used for polishing the barrier film was a polishing slurry containing a readily water-soluble corrosion inhibitor. The polishing slurry was washed away with water before the polishing treatment using a cleaning agent. The polishing conditions using the cleaning agent are shown below.
Polishing device: FREX300S2 manufactured by EBARA
Polishing time: 5-15 sec
Pressure: 100 hpa
Rotation speed: 100 rpm
Cleaning agent: pH = 8
Immediately after the polishing treatment with the cleaning agent, the wafer was held for 10 minutes during the transfer in the apparatus, and the number of defects per wafer was observed. The results are shown below. Moreover, the case where grinding | polishing using a cleaning agent was not performed as a comparative example is shown.

  As is clear from the above results, it is possible to suppress the occurrence of defects by carrying out the cleaning agent polishing according to the present invention.

DESCRIPTION OF SYMBOLS 1 Interlayer insulating film 2 Barrier metal film 3 Cu film 4 Anticorrosion film (Cu-BTA)
5 Cu ₂ O film 6 Antioxidation film

Claims (5)

Forming a wiring trench in an interlayer insulating film on a semiconductor substrate;
Forming a barrier metal film and a copper film;
Polishing a copper film and a barrier metal film by a chemical mechanical polishing method to expose the interlayer insulating film and embedding the copper film and the barrier metal film in the wiring groove;
In a method for manufacturing a semiconductor device comprising steps of cleaning and drying a semiconductor substrate,
Immediately after polishing the barrier metal film, the surface of the semiconductor substrate is polished using a cleaning agent having a pH adjusted to 7 to 12 to change the copper film surface to cuprous oxide, and to the cuprous oxide surface. A method of manufacturing a semiconductor device, comprising forming a film of the antioxidant.   The polishing of the copper film and the barrier metal film is performed using a polishing slurry containing a readily water-soluble corrosion inhibitor, and the film of the corrosion inhibitor on the surface of the copper film is removed by polishing using the cleaning agent. 2. A method for manufacturing a semiconductor device according to 1.   3. The method of manufacturing a semiconductor device according to claim 1, wherein the cleaning agent includes a metal chelating agent, an antioxidant, a remaining solvent and a pH adjusting agent necessary for adjusting the cleaning agent to pH 7 to 12. 4.   The semiconductor according to claim 3, wherein the cleaning agent contains an organic acid salt as a metal chelating agent, a secondary or tertiary organic amine or a quaternary organic ammonium salt as an antioxidant, and an organic acid as a pH adjuster. Device manufacturing method.   The method for manufacturing a semiconductor device according to claim 1, wherein the polishing using the cleaning agent is continuously performed by a polishing apparatus that polishes the copper film and the barrier metal film.