JP2002261051A - Polishing slurry and polishing method using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To maintain a constant slurry condition including manganese oxide
By setting it to the H region, it becomes possible to process copper as a wiring material, and the obtained processed surface uses an abrasive slurry and a polishing slurry having a smooth surface having metallic luster without scratches and the like. And a method for polishing. A slurry comprising at least one selected from the group consisting of MnO ₂ , Mn ₂ O ₃ and Mn ₃ O ₄ ,
A slurry for polishing, characterized in that the slurry has a pH of 0.1 to 3.0, and a polishing method using the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing slurry used as an abrasive, and more particularly to a polishing slurry used for flattening by a chemical mechanical polishing technique in a wiring process of a semiconductor integrated circuit. .

[0002]

2. Description of the Related Art In recent years, with the rapid progress of information technology, there has been a trend to increase the speed by miniaturization, higher density, and higher integration of large-scale integrated circuits (LSI, ULSI, VLSI). Technology development is being carried out by increasing the number of layers. In order to achieve multi-layered wiring, it is necessary to reduce the wiring pitch width and the capacitance between wirings. As a solution for reducing the wiring pitch width, tungsten and aluminum, which are existing metal wiring materials, have higher resistivity. Technology development to change to low copper (Cu) is being vigorously studied.

[0003] It is considered difficult to form copper wiring due to the vapor pressure of the product by the dry etching method. Therefore, the damascene process by embedding tends to be the mainstream.
Further, when the wiring material is made of Cu, the diffusion speed of the wafer material into silicon (Si) and the thermal oxide film (SiO ₂ ) becomes extremely high, which affects the transistor function, thereby interposing a barrier metal that prevents diffusion. The structure is applied.

[0004] Multi-layering of wiring is based on high-precision flattening of wiring patterns and wiring layers of respective layers, and flattening of wiring buried by the damascene method utilizes a synergistic property of a mechanical polishing action and a chemical polishing action. So-called CMP (Chemica)
1 Mechanical Polishing), and the copper wiring material is polished by the same method.

As a conventional general CMP agent for a metal wiring layer, alumina, cerium oxide or the like is used as abrasive grains, and a polishing agent in a system to which an oxidizing agent is added to impart a chemical action is applied. ing. However, Cu has low corrosion resistance with respect to a medium having an oxidizing power and is difficult to control. In addition, when a polishing agent containing an oxidizing agent has minute defects or the like in wiring recesses, the polishing agent penetrates into a defective portion during polishing and causes defects. There is a possibility of causing a problem such as enlarging.

As a new polishing material, for example, Japanese Patent Application Laid-Open No. 9-22887 discloses manganese dioxide (Mn).
There has been proposed a technique for planarizing a metal wiring layer, particularly tungsten, using an abrasive comprising O ₂ ) and an additive.
Japanese Patent Application Laid-Open No. 9-69501 proposes a technique of polishing a metal wiring layer using an abrasive containing MnO ₂ and using a nitride of a high melting point metal as a stopper. These proposals are polishing agents that apply the self-oxidizing power of MnO ₂ and are different from polishing agents to which an oxidizing agent is added. However, as a result of investigations by the present inventors, the slurry composition of the polishing agent in these proposals mainly uses water as a solvent, and with these slurry compositions, the Cu wiring material cannot be polished or the polishing is extremely difficult. It turned out to be sufficient.

On the other hand, Japanese Patent Application Laid-Open No. Hei 10-72578 proposes a technique using an abrasive composed of Mn ₂ O ₃ , Mn ₃ O ₄ and a mixture thereof. These manganese oxides are used for polishing an insulating layer. There is a statement that the processing speed is insufficient for polishing metal wiring.

[0008]

According to the present invention, the wiring material is C
In order to solve the above-mentioned problem with respect to polishing of a semiconductor device composed of u, it is possible to process copper as a wiring material by setting conditions of a slurry containing manganese oxide in a constant pH region, and obtain the obtained slurry. An object of the present invention is to provide an abrasive slurry having a processed surface having a metallic luster without scratches and the like and having excellent smoothness, and a method of polishing using such an abrasive slurry.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies for the purpose of solving the above-mentioned problems, and as a result, by maintaining the pH of the slurry containing manganese oxide in a certain range, the wiring material was formed as Cu. That the surface of the semiconductor device to be formed has a metallic luster and has a very small degree of unevenness and has no scratches on the surface, that the processing speed can be arbitrarily controlled by adjusting the pH, and that the lower manganese oxide It was also found that copper can be polished by controlling the pH to a certain range, and the present invention was proposed.

That is, the present invention relates to a slurry having at least one selected from the group consisting of MnO ₂ , Mn ₂ O ₃ and Mn ₃ O ₄ , wherein the slurry has a pH of 0.1 to 3.0.
And a method for polishing a semiconductor integrated circuit using the polishing slurry. Particularly, in the polishing slurry of the present invention, the wiring material of the semiconductor integrated circuit is copper (C).
u), which is suitable for polishing and flattening the Cu.

The present invention will be described in more detail.

The polishing slurry used in the present invention is Mn.
It contains at least one of O ₂ , Mn ₂ O ₃ and Mn ₃ O ₄ as an abrasive. That is, when these are used as abrasives, not only one kind alone, but also two kinds or all of them are used as a polishing slurry.

The pH of the slurry is preferably in the range from 0.1 to 3.0, and more preferably in the range from 0.1 to 2.0. When the pH exceeds 3.0, the slurry does not have a polishing effect on the metal wiring, and the surface of the Cu wiring material forms an oxide film. On the other hand, pH
If is less than 0.1, the basic effect as an abrasive is not hindered, but there is a possibility that workability and maintenance and management of equipment materials may be problematic.

The agent used for adjusting the pH of the slurry is not particularly limited, and hydrochloric acid, sulfuric acid,
An inorganic acid represented by a mineral acid such as nitric acid, an organic acid such as formic acid, and the like are used, but usually an inorganic acid is preferably used for operation. Although the particle size of the abrasive is not limited, it is preferable that the particle size is fine in consideration of the influence of the abrasive on the surface of the wiring material such as scratches.
0) is preferably 1.0 μm or less.

The concentration of the abrasive can be applied in any range from the low concentration to the high concentration as long as the object of the present invention can be achieved. However, considering the economy and the number of man-hours for slurry treatment, use the abrasive at the lowest concentration possible. Preferably, according to the polishing slurry of the present invention, as shown in Examples,
Polishing at an unprecedented low concentration of about 1% by weight is also possible.

The polishing slurry of the present invention can be suitably used when the wiring material of a semiconductor integrated circuit is composed of Cu, and this Cu wiring is usually formed by sputtering, CVD, plating or the like.

MnO ₂ used as an abrasive in the polishing slurry of the present invention is γ-MnO ₂ , β-MnO ₂
Although not particularly limited, usually γ-MnO
It is preferable to use electrolytic manganese dioxide which is ₂ .

When polishing a copper wiring material using a polishing slurry containing MnO ₂ as an abrasive, if the pH of the slurry is 3.0 or more, the slurry is not processed or becomes extremely low. Also, the polished surface results in the formation of an oxide film. on the other hand,
By setting the pH of the slurry to 3.0 or less, polishing characteristics appear. Further, the polishing characteristics improve as the pH decreases. In particular, by setting the pH of the slurry at 2.0 or less, the Cu surface changes dramatically, exhibits metallic luster, and forms a smooth surface without scratches. Mn ₂ O ₃ used as an abrasive in the polishing slurry of the present invention is:
Although there is no particular limitation on the powder material and the synthesis method, etc., generally, manganese oxide is used in air at 450 to 9
It can be easily obtained by firing at 00 ° C.

The Mn ₃ O ₄ used as an abrasive in the polishing slurry of the present invention is not particularly limited in its powder material, synthesis method, etc., and any material can be used. Usually, it can be obtained by firing manganese oxide in air at 900 ° C. or higher.

As described above, the polishing slurry of the present invention contains M
It is constituted by containing at least one or more of nO ₂ , Mn ₂ O ₃ and Mn ₃ O ₄ .

The application of a dispersant, a chelating agent, etc., which is generally added as an additive of a CMP slurry, does not cause any problem unless the conditions deviate from the pH range of the slurry of the present invention. In some cases, the polishing characteristics can be suitably achieved.

The polishing slurry of the present invention can be used as it is in the polishing step, but may be in a form that can be temporarily stored in consideration of storage, transportation and the like. In this case, the abrasive, liquid, additives and the like in the polishing slurry can be appropriately selected, and the pH of this agent may be within a range that can achieve the object of the present invention. What is necessary is just to be able to provide to the polishing slurry used for the above. Then, it may be mixed with an appropriate liquid or the like before or during the polishing operation.

As described in Chemical Dictionary 3, page 941 (published by Kyoritsu Shuppan Co., Ltd., first edition published on September 39, 1964), the manganese oxide species used as an abrasive in the present invention is a dilute acid. ^Has the advantage that it is reduced by a reducing agent, for example, H ₂ O _2, and is easily dissolved as Mn ^{2+ in} the presence of, so that it is also suitable for cleaning after polishing a semiconductor device.

The polishing using the polishing slurry of the present invention can be performed by a known polishing method. For example, a semiconductor integrated circuit, which is a material to be polished, is pressed against a polishing platen, The semiconductor integrated circuit can be polished and flattened by polishing while adding the polishing slurry of the present invention while sliding the integrated circuit and / or the polishing platen in rubbing motion of both or one of them.

[0025]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 An electrolytic manganese dioxide (manufactured by Tosoh Hyuga) having an average particle diameter (D50) of 1 μm was made into a 1 wt% slurry with ultrapure water. The pH was adjusted to any slurry from 13.5 to 0.2. Next, a 15 mm square dicing product of a Cu-plated wafer was used as a sample, mounted on the work plate 1 shown in FIG. The previously adjusted slurry is passed through the slurry supply nozzle 4 of FIG.
Polishing was performed with the rotation speed of the platen 3 in FIG. 1 set to 30 rpm while supplying at a dropping speed of 0 ml / min. Load amount is 2
50 g / cm ² , and the pad was made by Rodale Nitta
C1000 / SUBA400 was used.

FIG. 2 shows the results of the processing speed in the sheet resistance measurement using the four terminals. It is apparent that the processing is hardly performed when the pH is 4.0 or more. Also, the slurry p
By setting H to 3.0, polishing characteristics appear and the processing speed is 100 nm / min. If the pH of the slurry is further reduced, the processing speed increases with the pH. When the pH of the Cu surface was 2.0 or less, the glossiness was remarkably improved and no trace of scratches or the like was observed, and Ra as an index of the surface roughness was 0.7 nm.

Example 2 A 1 wt% slurry was prepared using electrolytic manganese dioxide having an average particle diameter (D50) of 4 μm (manufactured by Tosoh Hyuga), and sulfuric acid diluted with a special grade reagent was added dropwise to adjust the pH of the slurry.
Was arbitrarily adjusted from 4.0 to 0.5. When the same evaluation was performed under the same conditions as in Example 1, it was confirmed that polishing was impossible at a pH of 4.0. However, by setting the pH of the slurry to 3.0, processing characteristics appeared, and the processing speed was 100 nm / min. When the pH is further lowered, the processing speed increases.
The u surface exhibited luster, and no surface damage or the like was observed by microscopic observation.

Example 3 Using the manganese dioxide of Example 1, the pH of the slurry was arbitrarily set from 4.0 to 1.0 using special grade nitric acid. Using this slurry, a 50 mm square dicing product of a Cu-plated wafer was polished as a sample. The polishing conditions were the same as in Example 1. The obtained results are shown in FIG. 2, but the behavior was the same as in Example 1. When the pH of the slurry was 3.0 or less, a polishing action appeared, and scratches and the like on the Cu surface after polishing were not observed. .

Example 4 Using β-MnO ₂ synthesized by calcining MnOOH, the pH of the slurry was arbitrarily adjusted from 4.0 to 1.0 by using the sulfuric acid used in Example 1. It was confirmed that polishing was not possible when the pH of the slurry was 4.0.
On the other hand, when the pH was 3.0 or less, a behavior showing a polishing action was observed.

Example 5 Electrolytic manganese dioxide was calcined in the air at 700 ° C., and the obtained Mn ₂ O ₃ was pulverized into a powder having an average particle diameter of 1 μm. The polishing characteristics were evaluated under the same conditions as in Example 1 by changing the pH. Fig. 3 shows the results.
It was confirmed that the obtained polishing behavior was the same as in Example 1.

Example 6 Electrolytic manganese dioxide was calcined at 950 ° C. in the air, and the obtained Mn ₃ O ₄ was pulverized into a powder having an average particle diameter of 1 μm. The polishing characteristics were examined by changing the pH. As a result, it was confirmed that the obtained polishing behavior was the same as in Example 1.

Example 7 The electrolytic manganese dioxide of Example 2 and Mn ₂ O ₃ of Example 5 were mixed at a ratio of 1: 1 to form a slurry.
H was arbitrarily set from 4.0 to 1.0. It was confirmed that the obtained results were basically the same as those in Example 2.

[0034]

As described in detail above, the polishing pad of the present invention
Rally is MnO_Two, Mn_TwoO_Three, Mn_ThreeO _FourMore than one kind of
An abrasive is used, and the pH of the slurry containing the abrasive is adjusted to 0.1.
The polishing slurry of the present invention.
Can be used to polish various materials to be polished,
It is suitable when the wiring material of the semiconductor integrated circuit is Cu.
You. Furthermore, a semiconductor device in which the wiring material is made of Cu
The flattening of the chair can be established with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic view of a polishing apparatus according to an embodiment used in the present invention.

FIG. 2 is an explanatory diagram of a first embodiment and a second embodiment showing the effect of the present invention.

FIG. 3 is an explanatory diagram of Embodiment 5 showing the effects of the present invention.

[Explanation of symbols]

 1: Work plate 2: Correction ring 3: Surface plate 4: Slurry supply nozzle

Claims (5)

[Claims] 1. A slurry having at least one selected from the group consisting of MnO ₂ , Mn ₂ O ₃ and Mn ₃ O ₄ , wherein the slurry has a pH of 0.1 to 3.0. Polishing slurry. 2. A slurry provided to the polishing slurry according to claim 1, wherein the slurry is MnO ₂ , Mn ₂ O ₃ and Mn ₃ O _4.
A polishing slurry having at least one member selected from the group consisting of: 3. The polishing slurry according to claim 1, wherein the wiring material of the semiconductor integrated circuit is copper, and the wiring material can be polished and planarized. 4. A semiconductor integrated circuit is pressed against a polishing platen,
The semiconductor integrated circuit is polished and flattened while the polishing slurry according to claim 1 or 3 is added while the semiconductor integrated circuit and / or the polishing platen are rubbed. Polishing method. 5. A polishing method, wherein a wiring material of a semiconductor integrated circuit is copper.