JP2004023068A - Polishing slurry for copper-based metal and method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive slurry for copper-based metals, which contains alumina abrasive grains that are restrained from subsiding, condensing and solidifying and stably dispersed in the slurry when the slurry is stored. <P>SOLUTION: The abrasive slurry contains a water-soluble organic acid that produces a complex reacting on copper, the alumina abrasive grains, and polyacrylic alkyl oxide. The amount (wt.%) of polyacrylic alkyl oxide contained in the abrasive slurry for copper-based metals is calculated through formula, 3146.9×A<SP>-0.6166</SP>(wherein, A denotes weight-average molecular weight). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polishing slurry for copper-based metal and a method for manufacturing a semiconductor device.
[0002]
[Prior art]
2. Description of the Related Art In forming a wiring layer, which is one of the manufacturing steps of a semiconductor device, there is known a method of forming a buried wiring layer by using the following chemical mechanical polishing (CMP) technique to eliminate a step on a surface. 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 to leave a copper or copper alloy film in the groove to form a buried wiring layer. In forming such a buried wiring layer, a copper diffusion prevention film such as a Ta film is formed on the interlayer insulating film including the inner surface of the groove, if necessary, after the formation of the groove and before the formation of the wiring material film. .
[0003]
By the way, as a conventional polishing slurry for performing the CMP treatment on the wiring material film, a polishing abrasive made of a water-soluble organic acid which reacts with copper such as quinaldic acid to form a complex and alumina such as colloidal alumina is used. The composition containing the following is used.
[0004]
[Problems to be solved by the invention]
However, since the polishing slurry using alumina as abrasive grains is settled and condensed during storage and the like and solidified, the dispersibility of the abrasive grains composed of alumina in the polishing slurry is impaired, and the amount of dispersed abrasive grains is reduced. fluctuate. As a result, when the wiring material film such as Cu is subjected to the CMP process, the polishing rate fluctuates between lots and between lots. Therefore, if the polishing time is set within a certain design range, the polishing of the wiring material film becomes too small or too large. In addition, it becomes difficult to form a buried wiring layer having an intended processing shape.
[0005]
An object of the present invention is to provide a polishing slurry for copper-based metal in which the polishing abrasive grains are stably dispersed by suppressing the sedimentation and solidification of the abrasive grains made of alumina during storage or the like.
[0006]
According to the present invention, in a step of forming a buried wiring layer by performing a CMP process on a wiring material film made of copper or a copper alloy, the wiring material film can be stably formed without causing polishing variation between lots and within a lot. It is an object of the present invention to provide a method of manufacturing a semiconductor device which can be polished.
[0007]
[Means for Solving the Problems]
The polishing slurry for a copper-based metal according to the present invention comprises a water-soluble organic acid which reacts with copper to form a complex, abrasive grains made of alumina, and a weight average molecular weight of 10,000 to 8,000,000. Including polyacrylalkyl oxide,
The polyacrylalkyl oxide contains an amount (% by weight) calculated from 3146.9 × A− ^0.6166 (where A represents the weight average molecular weight of the polyacrylalkyl oxide). It is.
[0008]
In the method for manufacturing a semiconductor device according to the present invention, a step of forming at least one embedding member selected from a groove corresponding to a shape of a wiring layer and an opening corresponding to a shape of a via fill 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 inner surface of the embedding member;
Forming at least one conductive member selected from a wiring layer and a via fill in the embedding member by chemically and mechanically polishing the wiring material film using the copper-based metal polishing slurry;
It is characterized by including.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the polishing slurry for copper-based metal according to the present invention will be described in detail.
[0010]
This polishing slurry for a copper-based metal is composed of a water-soluble organic acid that reacts with copper to form a complex, abrasive grains made of alumina, and a polyacrylalkyl having a weight average molecular weight of 10,000 to 8,000,000. Oxide (hereinafter referred to as PAAO). The content (% by weight) of the PAAO is calculated from 3146.9 × A− ^0.6166 (where A indicates the weight average molecular weight of PAAO). Specifically, the weight average molecular weight of PAAO and the content of PAAO have the relationship shown in FIG.
[0011]
Examples of the organic acid include acetic acid, aminoacetic acid (glycine), 2-quinoline carboxylic acid (quinaldic acid), 2-pyridine carboxylic acid, 2,6-pyridine carboxylic acid, quinoline, and the like. Particularly, 2-quinoline carboxylic acid (quinaldic acid) is preferable.
[0012]
Examples of the alumina include at least one selected from colloidal alumina and θ-alumina.
[0013]
It is preferable that the abrasive grains have an average primary particle size of 0.02 to 0.1 μm, and have a spherical shape or a shape close to a sphere. When Cu or a Cu alloy is polished using a polishing slurry containing such polishing abrasive grains, damage to the polished surface of Cu or the Cu alloy can be suppressed.
[0014]
Examples of the polyacrylalkyl oxide (PAAO) include polyacrylethyl oxide, polyacrylpropyl oxide, and polyacrylbutyloxide.
[0015]
The polishing slurry according to the present invention is allowed to contain a complex formation promoter. An oxidizing agent such as hydrogen peroxide (H ₂ O ₂ ) or sodium hypochlorite (NaClO) can be used as the complex formation promoter.
[0016]
The polishing slurry for copper-based metal according to the present invention allows the addition of a nonionic, zwitterionic, anionic, or cationic surfactant. The polishing slurry further containing such a surfactant can enhance selective polishing of Cu or a Cu alloy and an insulating film such as a SiN film and SiO ₂ as described later.
[0017]
Examples of the nonionic surfactant include polyethylene glycol phenyl ether and ethylene glycol fatty acid ester.
[0018]
Examples of the zwitterionic surfactant include imidazoribetaine and the like.
[0019]
Examples of the anionic surfactant include sodium dodecyl sulfate and ammonium dodecyl sulfate.
[0020]
Examples of the cationic surfactant include stearin trimethylammonium chloride and the like.
[0021]
The aforementioned surfactants may be used in the form of a mixture of two or more.
[0022]
For example, a groove is formed in an insulating film on a substrate using the polishing slurry for a copper-based metal according to the present invention, and a Cu film or a Cu alloy film is formed on the insulating film including the groove. To polish the alloy film, a polishing apparatus shown in FIG. 2 is used. That is, the turntable 1 is covered with a polishing pad 2 made of, for example, a cloth or a polyurethane foam having closed cells. A supply pipe 3 for supplying the polishing slurry 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.
[0023]
In such a polishing apparatus, the substrate 6 is held by the holder 5 so that the polishing surface (eg, Cu film) faces the polishing pad 2, and the polishing liquid 7 having the above-described composition is supplied from the supply pipe 3. While applying a desired weight to the substrate 6 by the support shaft 4 toward the polishing pad 2, and further rotating the holder 5 and the turntable 1 in the same direction, the Cu film on the substrate 6 is formed. Polished.
[0024]
The polishing slurry for a copper-based metal according to the present invention described above is, for example, a water-soluble organic acid which reacts with copper such as quinaldic acid to form a complex, abrasive grains made of alumina, and a weight average molecular weight of 10 8,000 to 8,000,000 polyacrylalkyl oxide (PAAO), and the PAAO is 3146.9 × A- ^{0. 6166} (where A represents the weight-average molecular weight of PAAP), by containing the amount (% by weight) calculated from the abrasive grains made of alumina during storage and the like to prevent solidification by sedimentation and condensation during storage and the like. Since it can be suppressed by PAAO, the amount of alumina abrasive particles dispersed in the polishing slurry before and after storage can be made substantially constant. As a result, when the Cu film is subjected to the CMP processing using the polishing slurry of the present invention, the polishing rate can be kept constant without changing between the processing lots, so that the Cu film can be polished stably.
[0025]
Next, a method for manufacturing a semiconductor device according to the present invention will be described.
[0026]
First, at least one embedding member selected from a groove corresponding to the shape of a wiring layer and an opening corresponding to the shape of a via fill is formed in an insulating film on a semiconductor substrate. Subsequently, after forming a wiring material film made of copper or a copper alloy on the insulating film including the inner surface of the embedding member, the wiring material film is subjected to a CMP process using a polishing slurry for a copper-based metal having the above-described composition. To form at least one conductive member selected from a wiring layer made of copper or a copper alloy and a via fill in the embedding member, thereby manufacturing a semiconductor device.
[0027]
Examples of the insulating film include a silicon oxide film, a boron-doped glass film (BPSG film), a phosphorus-doped glass film (PSG film), SiOF, organic spin-on glass, polyimide, fluorinated polyimide, polytetrafluoroethylene, and polyallyl fluoride. Ether, fluorinated parelin, Low-K film, or the like can be used.
[0028]
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.
[0029]
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.
[0030]
The CMP process using the copper-based metal polishing slurry is performed using, for example, the above-described polishing apparatus shown in FIG.
[0031]
In the polishing process using the polishing apparatus shown in FIG. 2, the load applied to the polishing pad by the substrate held by the substrate holder is appropriately selected according to the composition of the polishing slurry, but is preferably, for example, 50 to 1000 g / cm ^2. .
[0032]
In the method for manufacturing a semiconductor device according to the present invention, after the formation of the burying member and before the formation of the wiring material film, a copper diffusion preventing film may be formed on the insulating film including the burying member. This copper diffusion prevention film is made of, for example, one layer or two or more layers selected from Ta, TaN, and W.
[0033]
The above-described method of manufacturing a semiconductor device according to the present invention includes the steps of: forming a wiring material film made of copper or a copper alloy on an insulating film including an inner surface of an embedding member; A water-soluble organic acid which forms a complex by reacting with copper such as an acid, abrasive grains made of alumina, and a polyacrylalkyl oxide (PAAO) having a weight average molecular weight of 10,000 to 8,000,000. And a polishing slurry for copper-based metal containing PAAO in an amount (% by weight) calculated from 3146.9 × A ^−0.6166 (where A represents the weight average molecular weight of PAAO). Done. Such a polishing slurry can suppress, by the PAAO, the polishing abrasive grains made of the alumina from settling and consolidating during storage or the like as described above. The dispersibility can be almost maintained in a state before storage, and the amount of the dispersed abrasive grains of alumina can be made substantially constant. As a result, by subjecting the wiring material film to the CMP treatment using the polishing slurry, the polishing rate of the wiring material film can be kept constant between lots (semiconductor devices) and within a lot, so that the intended purpose can be maintained. It is possible to manufacture a semiconductor device in which a conductive member such as a buried wiring layer having the above processed shape is formed with good reproducibility.
[0034]
【Example】
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0035]
(Example 1)
First, a SiO ₂ film is deposited by a CVD method on a silicon substrate on which a diffusion layer such as a source and a drain is formed, and a plurality of 500 nm-thick portions having a shape corresponding to a wiring layer are formed on the SiO ₂ film by a photoetching technique. Grooves 23 were formed. Subsequently, a Cu film having a thickness of 600 nm was formed on the SiO ₂ film including the groove by sputtering deposition.
[0036]
Then, the substrate is held upside down on the substrate holder 5 of the polishing apparatus shown in FIG. 2 described above, and the substrate is polished on the turntable 1 by a support shaft 4 of the holder 5; applying a load of 500 g / cm ² to the pad 2, the turntable 1 and the holder 5, respectively 103 rpm, while rotating in the same direction at 100rpm speed, storage days is 7 days, 60 days, following after the lapse of 180 days The polishing slurry for copper-based metal having the composition was supplied from the supply pipe 3 to the polishing pad 2 at a rate of 50 ml / min, and the Cu film formed on the substrate was polished until the surface of the SiO ₂ film was exposed.
[0037]
<Polishing slurry for copper-based metal; each component is in proportion to water>
-2-quinolinecarboxylic acid (quinaldic acid); 0.67% by weight,
· Θ alumina; 1.67% by weight,
Hydrogen peroxide; 4.67% by weight,
-Polyacrylethyl oxide having a weight average molecular weight of 6000; 20% by weight.
[0038]
As a result, irrespective of the storage days of the polishing slurry for copper-based metal, the uniformity of polishing between lots and within a lot is kept within 10%, and the embedding has an intended processing shape almost flush with the surface of the SiO ₂ film. A Cu wiring layer could be formed.
[0039]
(Comparative Example 1)
A buried Cu wiring layer was formed under the same conditions as in Example 1 except that four copper-based metal polishing slurries having the following composition after storage days of 1, 7, 60 and 180 days were used.
[0040]
<Polishing slurry for copper-based metal; each component is in proportion to water>
-2-quinolinecarboxylic acid (quinaldic acid); 0.67% by weight,
· Θ alumina; 1.67% by weight,
-Hydrogen peroxide: 4.67% by weight.
[0041]
As a result, the shape of the buried Cu wiring layer formed in the groove of the SiO ₂ film between lots and within the lot varied. In particular, when the polishing slurry for a copper-based metal having a long storage time is used, the CMP treatment of the wiring material film made of Cu is not sufficiently performed, and the embedded Cu wiring layer formed in the plurality of grooves of the same SiO ₂ film is not sufficiently processed. The shape of the sample varied.
[0042]
(Example 2)
First, as shown in FIG. 3A, an SiO ₂ film 22 having a thickness of, for example, 1000 nm as an insulating film is deposited on a silicon substrate 21 having a diffusion layer such as a source and a drain (not shown) formed on the surface thereof by a CVD method. After that, 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 photoetching technology. Subsequently, as shown in FIG. 3B, a copper diffusion preventing film 24 made of TaN 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 sputter deposition. Formed in order.
[0043]
Next, the substrate 21 shown in FIG. 3B is held upside down on the substrate holder 5 of the polishing apparatus shown in FIG. 2 described above, and the substrate is mounted on the turntable 1 by the Rodel Company on the support shaft 4 of the holder 5. A trade name: After a load of 500 g / cm ² is applied to the polishing pad 2 made of IC1000, and the turntable 1 and the holder 5 are rotated in the same direction at a speed of 103 rpm and 100 rpm, respectively, after a storage period of one day, Is supplied to the polishing pad 2 at a rate of 50 ml / min from a supply pipe 3 at a rate of 50 ml / min to prevent the Cu film 25 formed on the substrate 21 from diffusing into the copper on the SiO ₂ film 22. Polishing was performed until the surface of the film 24 was exposed.
[0044]
<Polishing slurry for copper-based metal; each component is in proportion to water>
-2-quinolinecarboxylic acid (quinaldic acid); 0.67% by weight,
· Θ alumina; 1.67% by weight,
Hydrogen peroxide; 4.67% by weight,
-Polyacrylethyl oxide having a weight average molecular weight of 6000; 20% by weight.
[0045]
In the 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 800 nm / min. For this reason, in the polishing step, the convex Cu film 25 shown in FIG. 3B was preferentially polished from the surface that is in mechanical contact with the polishing pad.
[0046]
Next, the substrate 21 shown in FIG. 3B is held upside down on the substrate holder 5 of another polishing apparatus having the same structure as that of FIG. 2 and adjacent to the polishing apparatus used for polishing the Cu film. A load of 500 g / cm ² is applied to the polishing pad 2 made of Rodel on the turntable 1 by the support shaft 4 of the holder 5, and the turntable 1 and the holder 5 are put at 103 rpm and 100 rpm, respectively. While rotating in the same direction at a speed, a polishing slurry for a copper diffusion preventing material having the following composition is supplied from the supply pipe 3 to the polishing pad 2 at a rate of 100 ml / min to remove the copper diffusion preventing film 24 formed on the substrate 21. Polishing was performed until the surface of the SiO ₂ film 22 was exposed. As a result, as shown in FIG. 3C, the copper diffusion preventing film 24 remains in the groove 23 and the surface of the SiO ₂ film 22 is formed in the groove 23 covered with the copper diffusion preventing film 24. The buried Cu wiring layer 26 having a desired processed shape which is almost even was formed.
[0047]
<Polishing slurry for copper diffusion prevention material; each component is in proportion to water>
-2-quinolinecarboxylic acid (quinaldic acid); 0.67% by weight,
* Θ-alumina; 1.67% by weight,
-Hydrogen peroxide: 17% by weight.
[0048]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a polishing slurry for copper-based metal in which the abrasive grains are stably dispersed by suppressing sedimentation and condensation of the abrasive grains made of alumina during storage and the like, and solidifying the abrasive grains. Can be.
[0049]
Further, according to the present invention, in a process of forming a conductive member such as a buried wiring layer by performing a CMP process on a wiring material film made of copper or a copper alloy, polishing variation between lots and within a lot does not occur. A method for manufacturing a semiconductor device capable of stably polishing a film and forming a conductive member having an intended processing shape between lots and within a lot can be provided.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the weight average molecular weight of PAAO and the content of PAAO.
FIG. 2 is a schematic view showing a polishing apparatus used in the polishing step 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 ... supply pipe,
5. Holder,
21 ... silicon substrate,
25 ... Cu film,
22 ... SiO ₂ film,
23 ... groove,
24 ... Copper diffusion prevention film,
26 ... Cu wiring layer.

Claims (5)

A water-soluble organic acid which reacts with copper to form a complex, abrasive grains made of alumina, and a polyacrylalkyl oxide having a weight average molecular weight of 10,000 to 8,000,000,
The said polyacrylalkyl oxide contains 3146.9xA- ^0.6166 (however, A shows the weight average molecular weight of polyacrylalkyl oxide), The copper content contains the amount (weight%) calculated. Polishing slurry for base metals. The polishing slurry for copper-based metal according to claim 1, wherein the alumina is at least one selected from colloidal alumina and Θ-alumina. The polishing slurry for copper-based metals according to claim 1, further comprising a complex formation promoter. Forming at least one embedding member selected from a groove corresponding to the shape of the wiring layer and an opening corresponding to the shape of the via fill 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 inner surface of the embedding member;
A step of forming at least one conductive member selected from a wiring layer and a via fill in the burying member by chemically and mechanically polishing the wiring material film using the polishing slurry for copper-based metal according to claim 1;
A method for manufacturing a semiconductor device, comprising: 5. The method according to claim 4, further comprising forming a copper diffusion prevention film on the insulating film including the burying member after forming the burying member and before forming the wiring material film. .

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