JP2000212776A - Aqueous dispersion for mechanochemical polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous dispersion for mechanochemical polishing useful for a metallic layer such as a film to be worked in a semiconductor device. SOLUTION: This aqueous dispersion contains an oxidizing agent such as hydrogen peroxide, peracetic acid, an organic peroxide or a permanganic acid compound, abrasive grains having 0.01-3 μm, particularly 0.05-1.0 μm average grain diameter and comprising inorganic particles of silica, alumina or the like or organic particles of polystyrene, polymethyl methacrylate or the like and water. When a body with a metallic layer to be polished is immersed in the aqueous dispersion for 30 min, the etching depth of the metallic layer is <=2,000 Å. The aqueous dispersion is used for mechanochemically polishing a metallic layer such as a film to be worked in a semiconductor device. The aqueous dispersion may further contain 3-3,000 ppm ions of a polyvalent metal such as aluminum, titanium or chromium, an organic acid such as p- toluenesulfonic acid or dodecylbenzenesulfonic acid and an inorganic acid such as nitric acid or hydrochloric acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aqueous dispersion for chemical mechanical polishing. More specifically, the present invention relates to an aqueous dispersion particularly useful in chemical mechanical polishing of a metal layer such as a film to be processed of a semiconductor device. If the metal layer is polished using the chemical mechanical polishing aqueous dispersion of the present invention, the polishing rate is high, the polishing can be efficiently performed, and excessive etching, thinning, dishing, keyhole, scratch, etc. The generation of the surface is low and the surface to be processed can be highly finished.

[0002]

2. Description of the Related Art With the improvement of the degree of integration of semiconductor devices and multi-layer wiring, a technique of chemical mechanical polishing has been introduced for polishing a film to be processed. JP-A-62-102543, JP-A-64-55845, JP-A-5-275
As disclosed in Japanese Patent Application Publication No. 366, Japanese Patent Application Laid-Open No. Hei 8-51037, Japanese Patent Application Laid-Open No. 8-17831, Japanese Patent Application Laid-Open No. 8-197414, and Japanese Patent Application Laid-Open No. 10-44047, etc. There is known a method of forming a wiring by embedding a wiring material such as tungsten, aluminum, or copper in a hole or a groove formed in a film and then removing excess wiring material by polishing.

[0003] In such polishing, it is necessary to effectively combine chemical etching and mechanical polishing, and the balance between the chemical action and the mechanical action is a good polished surface with high precision. Is important in obtaining
If the chemical etching is too strong, problems such as excessive etching, thinning, dishing, and keyhole may occur. On the other hand, if the mechanical polishing is too strong, mechanical damage is large and causes scratches. Further, when both chemical etching and mechanical polishing are weak, the polishing rate is too low to be practical.

As an abrasive for this chemical mechanical polishing,
Japanese Patent Publication No. 6-103681 discloses a polishing composition comprising abrasive particles, a transition chelate salt and a solvent dissolving the salt. Furthermore, Japanese Patent Publication No. 6-3133164
Japanese Patent Application Laid-Open Publication No. H11-157, discloses a polishing composition composed of an abrasive made of aqueous colloidal silica sol or gel and a polishing accelerator made of persulfate. Also, Japanese Patent Laid-Open No. 7-2
No. 33485 describes a polishing composition containing aminoacetic acid, amidosulfuric acid, an oxidizing agent and water. However, in many of these polishing compositions, as a result of enhancing the chemical polishing performance, the wiring material is excessively etched, and although the polishing rate is high, corrosion marks remain on the polished surface, and a good finished surface is obtained. There is a problem that can not be.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has a high polishing rate, can be efficiently polished, and has excessive etching, thinning, dishing, and keyholes. It is another object of the present invention to provide a chemical mechanical polishing aqueous dispersion that can produce a high-precision and good finished surface with less occurrence of scratches and the like. Another object of the present invention is to provide a chemical mechanical polishing aqueous dispersion useful in polishing a metal layer such as a film to be processed of a semiconductor device.

[0006]

An aqueous dispersion for chemical mechanical polishing according to the first invention comprises an oxidizing agent, an average particle diameter of 0.01 to 3 μm.
Wherein the metal layer has an etching depth of 2000 ° or less when it is brought into contact with the metal layer for 30 minutes, and is used for polishing the metal layer. Further, the chemical mechanical polishing aqueous dispersion of the second invention contains a polyvalent metal ion, an oxidizing agent, an acid, abrasive grains having an average particle diameter of 0.01 to 3 μm and water, and was brought into contact with the metal layer for 30 minutes. In this case, the metal layer has an etching depth of 2000 ° or less, and is used for polishing the metal layer.

The "oxidizing agent" can be used without any particular limitation as long as it is water-soluble. For example, depending on the electrochemical properties of a metal layer such as a film to be processed of a semiconductor device, for example, It is preferable to select and use an appropriate one according to a Pourbaix diagram or the like. Specific examples of the oxidizing agent include organic peroxides such as hydrogen peroxide, peracetic acid, perbenzoic acid, tert-butyl hydroperoxide, permanganate compounds such as potassium permanganate, and potassium dichromate. Dihalic acid compounds, such as potassium iodate, nitric acid compounds such as nitric acid and iron nitrate, perhalic acid compounds such as perchloric acid, transition metal salts such as potassium ferricyanide, and persulfates such as ammonium persulfate. , As well as heteropoly acids. Among these, hydrogen peroxide and organic peroxides which do not contain a metal element and whose decomposition products are harmless are particularly preferred.
By including these oxidizing agents, the polishing rate can be greatly improved particularly when polishing a metal layer such as a film to be processed of a semiconductor device.

[0008] The content of the oxidizing agent can be 0.1 to 15 parts by weight, especially 1 to 10 parts by weight, more preferably 2 to 8 parts by weight, when the aqueous dispersion is 100 parts by weight. Is preferred. If this content is less than 0.1 part by weight, the polishing rate of the aqueous dispersion will not be sufficiently high. Meanwhile, 1
When the content is 5 parts by weight, the polishing rate can be sufficiently improved, and when the content is more than 15 parts by weight,
Corrosion occurs on the surface to be polished and is dangerous in handling, which is not preferable.

As the above "abrasive grains", inorganic abrasive grains such as silica, alumina, titania and zirconia can be used. Also, polyvinyl chloride, polystyrene and styrene copolymers, polyacetal, saturated polyester, polyamide, polycarbonate, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-
Organic abrasive grains made of a thermoplastic resin such as a polyolefin and an olefin copolymer such as 1-pentene, a (meth) acrylic resin such as a phenoxy resin, and polymethyl methacrylate, and an acrylic copolymer can also be used.

The organic abrasive is obtained by copolymerizing styrene, methyl methacrylate or the like with divinylbenzene, ethylene glycol dimethacrylate or the like.
A polymer composed of a polymer having a crosslinked structure can also be used. Further, organic abrasive grains made of a thermosetting resin such as a phenol resin, a urea resin, a melamine resin, an epoxy resin, an alkyd resin, and an unsaturated polyester resin can also be used. These inorganic abrasive grains and organic abrasive grains may each be used alone or in combination of two or more. Further, inorganic abrasive grains and organic abrasive grains can be used in combination.

The shape of the polymer particles functioning as abrasive grains is preferably spherical. The spherical shape also means a substantially spherical shape having no acute angle portion, and does not necessarily need to be close to a true sphere. The use of spherical abrasive particles prevents or at least suppresses the occurrence of scratches on the surface to be polished during polishing and the roughening of the surface to be polished.

The average particle size of the abrasive grains is "0.01 to 3 μm"
If the average particle size is less than 0.01 μm, an aqueous dispersion having a sufficiently high polishing rate cannot be obtained.
On the other hand, when the average particle diameter exceeds 3 μm, the abrasive grains settle and separate, and it is not easy to obtain a stable aqueous dispersion. This average particle diameter is particularly 0.05 to 1.0.
μm, and more preferably 0.1 to 0.7 μm. Abrasive particles having an average particle diameter in this range can provide a stable chemical mechanical polishing aqueous dispersion that has a high polishing rate and does not cause sedimentation and separation of particles. In addition, this average particle diameter can be measured by observing with a transmission electron microscope.

[0013] The content of the abrasive grains is 10% for the aqueous dispersion.
When it is 0 parts by weight, it can be 0.1 to 20 parts by weight, particularly preferably 1 to 15 parts by weight, more preferably 2 to 10 parts by weight. When the content of the abrasive grains is less than 0.1 part by weight, the polishing performance is not sufficiently improved. On the other hand, when the content exceeds 20 parts by weight, the cost increases and the stability of the aqueous dispersion decreases. Therefore, it is not preferable.

In the second invention, the "polyvalent metal ion" includes aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc,
Examples include ions of metals such as germanium, zirconium, molybdenum, tin, antimony, tantalum, tungsten, lead, and cerium. These may be only one kind or two or more kinds of polyvalent metal ions may coexist. As the polyvalent metal ion, as in the third invention,
It is particularly preferable that the ion is at least one metal selected from aluminum, titanium, chromium, manganese, iron, copper, zinc, tin, and cerium because the polishing rate is higher.

The content of polyvalent metal ions contained in the aqueous dispersion is preferably 3 to 3000 ppm as in the third invention. This content is especially 10 to 2000p
pm, more preferably 30 to 1,000 ppm. This polyvalent metal ion has an action of promoting the function of the oxidizing agent, and the content of the polyvalent metal ion is 3%.
If the amount is less than ppm, the accelerating effect becomes insufficient, and the polishing rate is not sufficiently increased. On the other hand, 30
It is not preferable to include a polyvalent metal ion exceeding 00 ppm because a film to be processed of a semiconductor device is contaminated by the metal ion.

This polyvalent metal ion can be formed by adding a salt or complex such as a sulfate or an acetate containing a polyvalent metal element to an aqueous medium, and adding an oxide of the polyvalent metal element to the aqueous medium. It can also be generated. Further, even a compound which is added to an aqueous medium and generates a monovalent metal ion can be used as long as this ion becomes a polyvalent metal ion by an oxidizing agent.

By adding the above "acid" and adjusting the pH, the dispersibility, stability and polishing rate of the aqueous dispersion can be further improved. This acid is not particularly limited, and any of an organic acid and an inorganic acid can be used.
Examples of organic acids include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, isoprenesulfonic acid, gluconic acid, lactic acid, citric acid, tartaric acid, malic acid, glycolic acid, malonic acid, formic acid, oxalic acid, succinic acid, fumaric acid,
Maleic acid and phthalic acid; One of these organic acids may be used alone, or two or more thereof may be used in combination. Examples of the inorganic acid include nitric acid, hydrochloric acid, sulfuric acid and the like. These inorganic acids may be used alone or in combination of two or more. Further, an organic acid and an inorganic acid can be used in combination. These acids can be contained in an amount of 0.1 to 10 parts by weight, particularly 1 to 8 parts by weight, based on 100 parts by weight of the aqueous dispersion. When the content of the acid is in the range of 0.1 to 10 parts by weight, the dispersibility is excellent, and a sufficiently stable aqueous dispersion can be obtained. Further, etching and the like are suppressed, and the polishing rate is improved. preferable.

In the aqueous dispersions of the first and second inventions, when the metal layer such as a film to be processed of a semiconductor device is brought into contact with the aqueous dispersion for 30 minutes, the "etching depth" of this metal layer is " 2000 mm or less ". The etching depth can be about 30 to 1500 °, and more preferably about 20 to 1000 °. The oxidizing agent content and the polyvalent metal ion concentration are taken into consideration in consideration of the polishing rate and the presence or absence of corrosion on the surface to be polished. It is preferable that the etching depth is appropriately adjusted to obtain a required etching depth.

In the present invention, the degree of etching is adjusted by the composition of the aqueous dispersion as described above.
An aqueous dispersion for chemical mechanical polishing having a required polishing performance can be obtained. The method of contacting the metal layer and the aqueous dispersion is not particularly limited, but a method of immersing a film to be processed of a semiconductor device having the metal layer in the aqueous dispersion,
It is preferable because the contact can be made more reliably and it is simple.

In the aqueous dispersion of the present invention, as the medium, water and a mixture containing water as a main component such as water and methanol can be used, but it is particularly preferable to use only water.

Further, as a film to be processed having a metal layer,
A pure tungsten film, a pure aluminum film provided on a semiconductor substrate in a process of manufacturing a semiconductor device such as an VLSI,
Alternatively, in addition to a pure copper film or the like, a film made of an alloy of tungsten, aluminum, copper, or the like and another metal may be used.

Further, the chemical mechanical polishing of a film to be processed of a semiconductor device using the aqueous dispersion according to the present invention is performed by using a commercially available chemical mechanical polishing apparatus used in a conventional method using metal oxide particles as abrasive particles. Lapmaster SFT, model "LGP-510, LGP-552" etc.).

After polishing, it is preferable to remove abrasive grains remaining on the surface to be polished. The removal of the abrasive grains can be performed by a normal cleaning method. However, when the abrasive grains are organic particles, the surface to be polished is heated to a high temperature in the presence of oxygen to burn the organic abrasive grains and remove the abrasive grains. You can also. Specific methods of combustion include exposing to oxygen plasma, ashing treatment by plasma such as supplying oxygen radicals in a down flow, and the like, whereby residual organic abrasive grains can be easily removed from the surface to be polished. Can be removed.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples. Example l 0.214 parts by weight of copper gluconate (30% as copper ion)
It will contain 0 ppm. ) 4 parts by weight of hydrogen peroxide, 4 parts by weight of succinic acid and 5 parts by weight of fumed silica particles (Aerosil # 50) were mixed with ion-exchanged water, and 100 parts by weight of an aqueous dispersion for chemical mechanical polishing. Was prepared.

When a film to be processed having a tungsten layer of a semiconductor device was immersed in the aqueous dispersion for 30 minutes, the etching depth of the tungsten layer was 400 °. In addition, a tungsten film (thickness: 3000 mm) on a silicon wafer having a 6-inch thermal oxide film was set on a chemical mechanical polishing apparatus (Lapp Master SFT, model "LGP-510") and polished with porous polyurethane. Polishing was performed using a pad (trade name “ICl000” manufactured by Rodel Nitta Co., Ltd.) so that the weight became 300 g / cm ² . The surface of the urethane pad was rotationally polished at 50 rpm for 1 minute while supplying the aqueous dispersion at a rate of 150 cc / min. As a result, the polishing rate was 1500 ° / min. Further, when observed with a scanning electron microscope, no corrosion was observed on the surface of the tungsten film.

The etching depth was determined by measuring the sheet resistance with a resistivity measuring device (manufactured by NSP, Sigma 5 type) by a four probe method. The polishing rate was calculated based on the sheet resistance by calculating the residual film thickness from a calibration curve prepared in advance and following the formula below. Polishing rate (Å / min) = (Film thickness before polishing-Residual film thickness) / Polishing time

Examples 2 to 12 and Comparative Examples 1 and 2 Example 2 was repeated in the same manner as in Example 1 except that the types and amounts of the compounds for producing polyvalent metal ions were as shown in Table 1. 2 to 12 and Comparative Examples 1 and 2 were prepared. Using this aqueous dispersion, the etching depth and polishing rate were measured in the same manner as in Example 1,
The presence or absence of corrosion was observed. The results are also shown in Table 1.

[0028]

[Table 1]

According to the results shown in Table 1, in Examples 1 to 11, the etching depth was in the range of 50 to 1400 ° and the polishing rate was in the range of 50 to 1400 °, although there was a difference depending on the type of polyvalent metal ion and its concentration. There is no correlation with
It can be seen that the polishing was performed at a sufficient speed of 800 to 2400 ° / min. In addition, no or little corrosion was observed, indicating that there was almost no problem. Further, Example 1
In No. 2, the etching depth was 200 °, the polishing rate was 600 ° / min, and it was found that the polishing rate was sufficiently high and no corrosion occurred even if polyvalent metal ions were not contained. . On the other hand, in Comparative Examples 1 and 2, although the polishing can be performed at a sufficient speed, it can be seen that the etching depth is large and the corrosion is large.

FIG. 1 shows the correlation between the immersion time of the aqueous dispersions of Example 8 and Comparative Example 1 and the etching depth. According to FIG. 1, it can be seen that in Example 8, the etching proceeds gently, and is 100 ° even after 30 minutes. On the other hand, in Comparative Example 1, the etching progressed at a considerable speed, and reached a depth of 3000 ° after 30 minutes. Therefore, as described above, the surface of the metal layer after polishing is severely corroded, and although it can be polished, it is not practical.

[0031]

When the metal layer such as a film to be processed of a semiconductor device is polished using the aqueous dispersion for chemical mechanical polishing of the first and second inventions as an abrasive, the polishing rate is high and the surface to be polished is scratched. Does not occur. In particular, when the specific oxide of the fourth invention is used, it is safe because it does not contain heavy metals, and its decomposition products are also harmless.

[Brief description of the drawings]

FIG. 1 is a graph showing a correlation between an immersion time and an etching amount in Example 8 and Comparative Example 1.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C09K 3/14 550 C09K 3/14 550E 550H 550M (72) Inventor Masayuki Motonari Tsukiji, Chuo-ku, Tokyo 2-11-11 24 Inside JSR Co., Ltd. (72) Inventor Akira Iio 2-11-24 Tsukiji, Chuo-ku, Tokyo FSR Inside JSR Co., Ltd. 3C058 AA07 CA01 CB01 CB02 CB03 CB10 DA02 DA12 DA17 4K057 WA11 WB04 WB05 WB08 WB15 WE02 WE03 WE08 WE11 WE13 WE14 WE25 WE30 WG03 WG04 WN01 5F043 AA24 AA26 BB16 BB18 DD16

Claims (4)

[Claims] 1. An etching agent containing an oxidizing agent, abrasive grains having an average particle diameter of 0.01 to 3 μm, and water, and having an etching depth of 2000 ° or less when brought into contact with the metal layer for 30 minutes. An aqueous dispersion for chemical mechanical polishing, which is used for polishing a metal layer. 2. A metal layer containing polyvalent metal ions, an oxidizing agent, an acid, abrasive grains having an average particle diameter of 0.01 to 3 μm, and water.
An aqueous dispersion for chemical mechanical polishing, wherein the metal layer has an etching depth of 2000 ° or less when contacted for 0 minutes, and is used for polishing the metal layer. 3. The method according to claim 2, wherein the polyvalent metal ion is aluminum,
The chemical mechanical polishing aqueous dispersion according to claim 2, wherein the dispersion is at least one metal ion selected from titanium, chromium, manganese, iron, copper, zinc, tin, and cerium, and has a concentration of 3 to 3000 ppm. 4. The chemical mechanical polishing aqueous dispersion according to claim 1, wherein the oxidizing agent is at least one selected from hydrogen peroxide and a water-soluble organic peroxide. body.