JP2004022855A - Process for producing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing a semiconductor device in which the surface of a buried wiring layer formed by CMP processing can be cleaned by removing copper complex effectively from the surface. <P>SOLUTION: The process for producing a semiconductor device comprises a step for forming grooves corresponding to the shape of the wiring layer in an insulating film formed on a semiconductor substrate, a step for forming a wiring material film of copper or a copper alloy on the insulating film including the inner surface of the groove, a step for forming the wiring layer in the groove by polishing the wiring material film chemomechanically using polishing slurry for copper based metal containing an organic acid for forming a copper complex and an oxidizing agent, and a step for cleaning the surface of the insulating film including the wiring layer with cleaning liquid containing organoalkali and chelating agent. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device.
[0002]
[Prior art]
In recent years, with the increase in the degree of integration of semiconductor devices, circuit wiring has become finer. The use of Al as a wiring material and Cu having a low specific resistance and a high allowable current density has been studied, and research and development have been actively conducted. .
[0003]
In a semiconductor device having such a Cu wiring, a method of forming a buried wiring layer by using the following chemical mechanical polishing (Chemical Mechanical Polishing: CMP) technique to eliminate a step on the surface is adopted.
[0004]
That is, a groove is formed in an interlayer insulating film made of, for example, SiO ₂ on a semiconductor substrate, and a wiring material film made of copper or a copper alloy is formed on the entire surface of the interlayer insulating film including the groove so as to sufficiently fill the groove. Thereafter, the wiring material film is subjected to a CMP process using a polishing apparatus and a polishing slurry for a copper-based metal containing an organic acid for forming a copper complex (for example, 2-quinolinecarboxylic acid) and an oxidizing agent (for example, hydrogen peroxide). A buried wiring layer is formed by leaving a copper or copper alloy film in the trench.
[0005]
By the way, since the copper complex remains on the surface of the wiring layer after the formation of the buried wiring layer by the CMP treatment using the polishing slurry, the wiring resistance increases and varies.
[0006]
For this reason, conventionally, after the formation of the buried wiring layer, cleaning with a cleaning liquid containing an organic alkali such as tetramethyl ammonium hydroxide is performed.
[0007]
[Problems to be solved by the invention]
However, it has been difficult to always sufficiently remove the copper complex on the surface of the embedded wiring layer by the conventional cleaning method.
[0008]
An object of the present invention is to provide a method of manufacturing a semiconductor device capable of effectively removing a copper complex on a surface of an embedded wiring layer formed by a CMP process and cleaning the surface.
[0009]
[Means for Solving the Problems]
A method of manufacturing a semiconductor device according to the present invention includes a step of forming a groove corresponding to a shape of a wiring layer in an insulating film on a semiconductor substrate;
Forming a wiring material film made of copper or a copper alloy on the insulating film including the groove inner surface,
A step of forming a wiring layer in the groove by chemically and mechanically polishing the wiring material film using a polishing slurry for a copper-based metal containing an organic acid for forming a copper complex and an oxidizing agent, comprising an organic alkali and a chelating agent Cleaning the surface of the insulating film including the wiring layer with a cleaning liquid.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method for manufacturing a semiconductor device according to the present invention will be described (first step).
First, a groove corresponding to the shape of a wiring layer is formed in an insulating film on a semiconductor substrate. Subsequently, a wiring material film made of copper or a copper alloy is formed on the insulating film including the inner surface of the groove.
[0011]
As the insulating film, for example, a silicon oxide film, a boron-doped glass film (BPSG film), a phosphorus-doped glass film (PSG film), or the like can be used. Further, as the insulating film, for example, a film made of an insulating material such as SiOF, organic spin-on-glass, or polyimide can be used.
[0012]
As the Cu alloy, for example, a Cu-Si alloy, a Cu-Al alloy, a Cu-Si-Al alloy, a Cu-Ag alloy, or the like can be used.
[0013]
The wiring material film made of Cu or Cu alloy is formed by sputter deposition, vacuum deposition, electroless plating, or the like. Specifically, copper or a copper alloy is deposited by a sputtering method or a CVD method, and further subjected to electroless copper plating to form a wiring material film made of copper or a copper alloy.
[0014]
It is allowed to form a copper diffusion preventing film before forming a wiring material film in the trench. This copper diffusion prevention film is made of, for example, one layer or two or more layers selected from Ta, TaN, TaNb, and W. Such a copper diffusion barrier film preferably has a thickness of 15 to 50 nm.
[0015]
(2nd process)
The wiring material film is subjected to chemical mechanical polishing (CMP) using a polishing slurry for a copper-based metal containing an organic acid for forming a copper complex and an oxidizing agent to form a buried wiring layer in the groove.
[0016]
The CMP is performed using the polishing apparatus shown in FIG. 1 and the polishing slurry for copper-based metal. That is, the turntable 1 is covered with a polishing pad 2 made of, for example, cloth, polyurethane foam having closed cells, or the like. A first supply pipe 3 for supplying the polishing slurry for copper-based metal is disposed above the polishing pad 2. A substrate holder 5 having a support shaft 4 on the upper surface is arranged above the polishing pad 2 so as to be vertically movable and rotatable. In such a polishing apparatus, the substrate 6 is held by the holder 5 so that the polishing surface (eg, Cu film) of the polishing pad 2 faces the polishing pad 2, and the polishing slurry 7 having the above-described composition is supplied from the first supply pipe 3. While supplying, the substrate 6 is given a desired weight toward the polishing pad 2 by the support shaft 4, and the holder 5 and the turntable 1 are respectively rotated in the same direction so that Cu on the substrate 6 is The film is polished.
[0017]
Examples of the organic acid include 2-quinoline carboxylic acid (quinaldic acid), 2-pyridine carboxylic acid, 2,6-pyridine carboxylic acid, and quinoline.
[0018]
The organic acid is preferably contained in the polishing slurry in an amount of 0.1% by weight or more.
[0019]
The oxidizing agent has an action of generating a hydrate of copper when the polishing composition is brought into contact with copper or a copper alloy. As such an oxidizing agent, for example, an oxidizing agent such as hydrogen peroxide (H ₂ O ₂ ) or sodium hypochlorite (NaClO) can be used.
[0020]
It is preferable that the content of the oxidizing agent is 3 to 20 times the weight of the organic acid by weight.
[0021]
The polishing slurry for a copper-based metal is allowed to further contain abrasive grains. Examples of the abrasive grains include alumina powder such as colloidal alumina and silica powder such as colloidal silica.
[0022]
It is preferable that the abrasive grains are contained in the polishing slurry at 0.8 to 20% by weight. When the content of the abrasive grains is less than 0.8% by weight, it is difficult to sufficiently achieve the effect. On the other hand, when the content of the abrasive grains exceeds 20% by weight, the polishing composition becomes difficult to handle, for example, the viscosity of the polishing composition increases. A more preferable content of the abrasive grains is 0.8 to 3% by weight.
[0023]
The polishing slurry for a copper-based metal is allowed to further contain another organic acid having one carboxyl group and one hydroxyl group. This other organic acid has an effect of promoting the formation of copper hydrate by the oxidizing agent. Such other organic acids include, for example, lactic acid, tartaric acid, mandelic acid, malic acid and the like, and these can be used in the form of one or a mixture of two or more. Lactic acid is particularly preferably used as the other second organic acid.
[0024]
The polishing slurry for copper-based metal allows the addition of a nonionic, zwitterionic, anionic, or cationic surfactant. The polishing composition further containing such a surfactant makes it possible to enhance selective polishing of Cu or a Cu alloy and an insulating film such as a SiN film and SiO ₂ as described later.
[0025]
The polishing slurry for copper-based metal is allowed to further contain a dispersant for the polishing abrasive grains. Examples of the dispersant include polyvinylpyrrolidone (PVP).
[0026]
In the polishing process using the polishing apparatus, the load applied to the polishing pad by the substrate held by the substrate holder is appropriately selected depending on the composition of the polishing composition, and is preferably, for example, 50 to 1000 g / cm ² .
[0027]
When a copper diffusion preventing film is formed prior to forming a wiring material film in the groove, the wiring material film is subjected to chemical mechanical polishing (CMP) using the copper-based metal polishing slurry, and The exposed copper diffusion preventing film is subjected to CMP to form a buried wiring layer in the trench, the periphery of which is covered with the copper diffusion preventing film except for the surface.
[0028]
(3rd step)
The surface of the insulating film including the embedded wiring layer of the semiconductor substrate is cleaned with a cleaning liquid containing an organic alkali and a chelating agent to manufacture a semiconductor device.
[0029]
The cleaning operation is performed, for example, by supplying the cleaning liquid 9 having the composition through the second supply pipe 8 to the polishing pad 2 of the polishing apparatus following the CMP processing of the wiring material film by the polishing apparatus shown in FIG. Done.
[0030]
Examples of the organic alkali include quaternary ammonium salts such as tetramethylammonium hydroxide, tetramethylammonium chloride, and tetramethylhydroxide.
[0031]
The amount of the organic alkali in the cleaning solution is preferably set to 1 to 10% by weight. If the amount of the organic alkali is less than 1% by weight, it becomes difficult to sufficiently remove the copper complex on the surface of the embedded wiring layer. On the other hand, when the amount of the organic alkali exceeds 10% by weight, the wiring layer surface may be damaged.
[0032]
The chelating agent may be any as long as it has a property of forming a chelate with copper and dissolving the chelate compound in water, and can be used at pH 10 to 12. As such a chelating agent, for example, benzotriazole and its derivatives can be used. Examples of the benzotriazole derivative include 1- (2,3-dihydroxypropyl) benzotriazole, 1- [N, N-bis (hydroxydiethyl) aminomethyl] benzotriazole and the like.
[0033]
It is preferable that the amount of the chelating agent in the cleaning liquid is 0.01 to 10% by weight. When the amount of the chelating agent is less than 0.01% by weight, it becomes difficult to sufficiently remove the copper complex on the surface of the embedded wiring layer. On the other hand, if the amount of the chelating agent exceeds 10% by weight, a thick coating may be formed on the surface of the wiring layer.
[0034]
The present invention is applicable not only to the manufacture of semiconductor devices but also to the manufacture of other semiconductor devices such as liquid crystal display devices.
[0035]
According to the present invention described above, a groove corresponding to the shape of a wiring layer is formed in an insulating film on a semiconductor substrate, and a wiring material film made of copper or a copper alloy is formed on the insulating film including the inner surface of the groove. After forming a wiring layer in the groove by chemically and mechanically polishing the wiring material film using a polishing slurry for a copper-based metal containing an organic acid for forming a copper complex and an oxidizing agent, containing an organic alkali and a chelating agent By cleaning the surface of the insulating film including the wiring layer with a cleaning liquid, the copper complex on the surface of the buried wiring layer can be effectively removed and the surface can be cleaned. As a result, a highly reliable semiconductor device in which a low-resistance buried wiring layer having the original resistance value of copper or a copper alloy is formed can be manufactured.
[0036]
【Example】
Hereinafter, preferred embodiments of the present invention will be described in detail.
[0037]
(Example 1)
A washing solution was prepared in which 2.5% by weight of tetramethyl ammonium hydroxide and 0.1% by weight of 1- [N, N-bis (hydroxydiethyl) aminomethyl] benzotriazole were dissolved.
[0038]
(Comparative Example 1)
A washing solution in which 2.5% by weight of tetramethyl ammonium hydroxide was dissolved was prepared.
[0039]
The silicon wafer 6 having the Cu film formed on the substrate holder 5 is turned upside down using the polishing apparatus shown in FIG. 1 so that the Cu film faces the polishing pad (trade name: IC1000, manufactured by Rodale) 2. The wafer 6 is applied with a load of 300 gf / cm ² to the polishing pad 2 by the support shaft 4, and the turntable 1 and the holder 5 are rotated in the same direction at a speed of 63 rpm and 60 rpm, respectively. The Cu film was polished by supplying the polishing slurry for copper-based metal to the polishing pad 2 at a rate of 100 mL / min from the first supply pipe 3.
[0040]
<Polishing slurry for copper-based metal; each component is in proportion to water>
-2-quinolinecarboxylic acid (quinaldic acid); 0.67% by weight,
-Lactic acid: 0.67% by weight,
Colloidal alumina; 1.67% by weight;
Hydrogen peroxide; 4.67% by weight,
Ammonium dodecyl sulfate; 0.576% by weight
-Polyvinylpyrrolidone (PVP); 0.4% by weight.
[0041]
Next, the supply of the polishing slurry for copper-based metal from the first supply pipe 3 of the polishing apparatus of FIG. 1 is stopped, and the rotation of the turntable 1 and the holder 5 is continued, while the rotation of the turntable 1 and the holder 5 is continued. By supplying the cleaning liquid of Comparative Example 1 to the polishing pad 2 at a rate of 200 mL / min, the polished Cu film surface was cleaned.
[0042]
The number of particles of 0.2 μm or more on the surface of the Cu film after cleaning with the cleaning liquids of Example 1 and Comparative Example 1 was measured with a particle inspection device (trade name: SFS6420 manufactured by Tencor). The result is shown in FIG. In FIG. 2, the value of Example 1 is shown as a relative value when the number of particles after cleaning in Comparative Example 1 is set to 100.
[0043]
As is clear from FIG. 2, the number of particles on the surface of the Cu film cleaned with the cleaning liquid of Example 1 is significantly reduced as compared with that on the surface of the Cu film cleaned with the cleaning liquid of Comparative Example 1.
[0044]
In addition, the contact angle of the Cu film surface after cleaning with the cleaning liquids of Example 1 and Comparative Example 1 (if the copper complex remains, the contact angle becomes hydrophobic and the contact angle increases). As a result, the contact angle of the pure Cu film surface was 66 °, whereas that of Example 1 was 57 ° and that of Comparative Example 1 was 89 °.
[0045]
These results show that the use of the cleaning liquid of Example 1 can clean the polished Cu film surface.
[0046]
(Example 2)
First, as shown in FIG. 3A, an SiO ₂ film 22 having a thickness of, for example, 1000 nm as an interlayer insulating film is formed on a silicon substrate 21 having a diffusion layer such as a source and a drain (not shown) formed on a surface thereof by a CVD method. After the deposition, a plurality of trenches 23 having a shape corresponding to the wiring layer and having a depth of 500 nm were formed in the SiO ₂ film 22 by a photoetching technique. Subsequently, as shown in FIG. 3B, a copper diffusion preventing film 24 made of Ta and having a thickness of 15 nm and a Cu film 25 having a thickness of 600 nm are formed on the SiO ₂ film 22 including the groove 23 by sputtering deposition. Formed in order.
[0047]
Next, the substrate 21 shown in FIG. 3B is held upside down on the substrate holder 5 of the polishing apparatus shown in FIG. 1 and the substrate is turned on the turntable 1 by the support shaft 4 of the holder 5. Ltd. trade name; the polishing pad 2 consisting of IC1000 applying a load of 500 g / cm ^2, 103 rpm the turntable 1 and the holder 5, respectively, while rotating in the same direction at 100rpm speed, polishing copper-based metal of the composition The slurry is supplied from the first supply pipe 3 to the polishing pad 2 at a rate of 50 ml / min to expose the Cu film 25 formed on the substrate 21 to the surface of the copper diffusion preventing film 24 on the SiO ₂ film 22. Polished until. In this polishing step, the polishing slurry did not undergo any etching at the time of contact with the Cu film, and the polishing rate at the time of polishing with the polishing pad was about 600 nm / min. Therefore, in the polishing step, the convex Cu film 25 shown in FIG. 3B was preferentially polished from the surface that mechanically contacts the polishing pad.
[0048]
Next, the substrate 21 shown in FIG. 3B is held upside down on the substrate holder 5 of the same polishing apparatus, and the substrate is mounted on the turntable 1 by the support shaft 4 of the holder 5; the polishing pad 2 consisting of applying a load of 500 g / cm ^2, 103 rpm the turntable 1 and the holder 5, respectively, while rotating in the same direction at 100rpm speed, abrasive grains weight than the copper-based metal polishing slurry A large amount of the polishing slurry for copper diffusion preventing material is supplied from the first supply pipe 3 to the polishing pad 2 at a rate of 100 ml / min to expose the copper diffusion preventing film 24 formed on the substrate 21 to the surface of the SiO ₂ film 22. Polished until.
[0049]
As a result, as shown in FIG. 3C, the copper diffusion prevention film 24 remains in the trench 23 and is buried substantially flush with the surface of the SiO ₂ film 22 covered with the copper diffusion prevention film 24. The Cu wiring layer 26 was formed.
[0050]
Then, the supply of the polishing slurry for the copper diffusion preventing material from the first supply pipe 3 of the polishing apparatus of FIG. 1 is stopped, and the rotation of the turntable 1 and the holder 5 is continued, and the second supply pipe 8 is used to stop the polishing. A semiconductor device was manufactured by cleaning the buried Cu wiring layer 26 after polishing by supplying the polishing pad 2 with a cleaning liquid having the same composition as that of No. 1 at a rate of 200 mL / min.
[0051]
In the semiconductor device obtained in Example 2, a buried Cu wiring layer having a low resistance inherent to copper was formed.
[0052]
【The invention's effect】
As described above, according to the present invention, the copper complex on the surface of the buried wiring layer formed by the CMP treatment can be effectively removed to clean the surface, and the low resistivity inherent to copper or copper alloy can be obtained. And a method for manufacturing a highly reliable semiconductor device having a buried wiring layer having
[Brief description of the drawings]
FIG. 1 is a schematic view showing a polishing apparatus used in a polishing step of the present invention.
FIG. 2 is a characteristic diagram showing the number of particles (relative value) on the surface of a Cu film after cleaning with a cleaning liquid of Example 1 and Comparative Example 1 of the present invention.
FIG. 3 is a sectional view showing a manufacturing step of the semiconductor device according to the second embodiment of the present invention.
[Explanation of symbols]
1. Turntable,
2. Polishing pad,
3, 8 ... supply pipe,
5. Holder,
11 ... silicon substrate,
15 ... Cu film,
12: SiO ₂ film,
23 ... groove,
14. Copper diffusion preventing film,
26 ... Cu wiring layer,

Claims (3)

Forming a groove corresponding to the shape of the wiring layer in the insulating film on the semiconductor substrate;
Forming a wiring material film made of copper or a copper alloy on the insulating film including the groove inner surface,
A step of forming a wiring layer in the groove by chemically and mechanically polishing the wiring material film using a polishing slurry for a copper-based metal containing an organic acid for forming a copper complex and an oxidizing agent, comprising an organic alkali and a chelating agent Cleaning the surface of the insulating film including the wiring layer with a cleaning liquid. 2. The method according to claim 1, wherein the organic alkali is tetramethyl ammonium hydroxide. The method according to claim 1, wherein the chelating agent is benzotriazole or a derivative thereof.

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