JP2003286477A - Polishing composition and polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing composition which, when used in a CMP (chemical mechanical polishing) process of a semiconductor device having a copper film and a tantalum compound, exhibits a higher rate of polishing copper during polishing the copper surface and exhibits a lowered rate of polishing copper and a higher rate of polishing the tantalum compound during polishing the tantalum compound and to provide a polishing method using the composition. <P>SOLUTION: The polishing composition is one comprising (A) an abrasive, (B) an organic acid, (C) an oxidizing agent, (D) an antioxidant, (E) a polishing rate modifier, and (F) water, wherein the abrasive comprises particles prepared by coating inorganic particles comprising at least one member selected from among fumed silica, colloidal silica, fumed alumina, and colloidal alumina with an organic resin. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polishing composition used for polishing semiconductors, substrates for various memory hard disks, and the like, and more particularly to a polishing composition preferably used for surface flattening of semiconductor device wafers. It is about.

[0002]

2. Description of the Related Art With the recent remarkable development of the electronics industry, it has evolved into transistors, ICs, LSIs, and VLSIs, and the design of semiconductor devices has increased with the rapid increase in the degree of integration of circuits in these semiconductor elements. The rules are becoming finer year by year, the depth of focus in the device manufacturing process is becoming shallower, and the flatness of the pattern formation surface is becoming more and more severe.

On the other hand, in order to cover an increase in wiring resistance due to the miniaturization of wiring, copper wiring having a smaller electric resistance has been studied from aluminum or tungsten as a wiring material. However, when copper is used for wiring layers or interconnections between wirings, after forming wiring grooves or holes on the insulating film, a copper film is formed by sputtering or plating, and then chemical mechanical polishing (CMP) is used. The unnecessary copper on the insulating film is removed.

In such a process, copper diffuses into the insulating film and deteriorates the device characteristics. Therefore, it is common to provide a tantalum or tantalum nitride layer as a barrier layer on the insulating film to prevent the diffusion of copper. It has become a target.

In the flattening CMP process of the device in which the copper film is formed on the uppermost layer in this manner, the unnecessary portion of the copper film is first polished to the surface layer of the tantalum compound formed on the insulating layer, In the next step, the tantalum compound layer on the insulating film should be polished and the polishing should be completed when the SiO2 surface is exposed. Such a process is shown in FIG. 1. In the CMP polishing in such a process, it is necessary that the polishing rate be selective with respect to different materials such as copper, tantalum compound and SiO ₂ .

That is, in step 1, the polishing rate for copper is high and the selectivity for tantalum compounds is such that there is almost no polishing ability. Further, in step 2, although the polishing rate for the tantalum compound is large, SiO2
It is preferable that the polishing rate is smaller than that of SiO ₂ because it can prevent excessive shaving of SiO ₂ .

Ideally, it is desired that this process can be polished with one abrasive, but since the selectivity of the polishing rate for different materials cannot be changed during the process, the process is divided into two steps and different. Each CMP step is performed with two slurries that have selectivity. Usually, in order to prevent excessive cutting (dishing, recess, erosion) of the copper film in the grooves and holes, polishing is finished in step 1 with the copper film on the tantalum compound slightly left. Then, in step 2, a slight amount of remaining copper and tantalum compound is polished and removed by using the SiO ₂ layer as a stopper.
It is necessary for the polishing composition used in Step 1 to have a high polishing rate only for the copper film without causing surface defects (scratches) that cannot be recovered in Step 2.

A polishing composition for such a copper film is disclosed in JP-A-7-233485.
At least one selected from aminoacetic acid and amidosulfate
A polishing composition containing various kinds of organic acids, an oxidizing agent, and water. A relatively large polishing rate was obtained for copper, which can be presumed to be because copper ionized by the oxidizing agent forms a chelate with the above-mentioned organic acid to facilitate mechanical polishing.

However, using the above polishing composition,
When polishing a semiconductor device having a copper film and a tantalum compound, the polishing selectivity between copper and the tantalum compound is not sufficient, or if the selectivity to copper is increased, the copper film in the wiring groove or hole is excessively scraped, or the copper film surface However, there was a problem that the smoothness of the

[0010]

SUMMARY OF THE INVENTION In the CMP process of a semiconductor device having a copper film and a tantalum compound, the present invention has a large copper polishing rate when polishing a copper surface, but does not provide a high polishing rate when polishing a tantalum compound. It is intended to provide a polishing composition and a polishing method in which the polishing rate of copper is reduced and the polishing rate of a tantalum compound is improved. Further, the polishing composition for CMP processing is excellent in the smoothness of the copper film surface. is there.

[0011]

[Means for Solving the Problems] (A) Abrasive, (B) Organic acid, (C) Hydrogen peroxide, (D) Benzotriazole or its derivative, (E) Polishing rate regulator and (F) Water In the polishing composition having (A), the abrasive is a particle obtained by coating at least one kind of inorganic particles selected from fumed silica, colloidal silica, fumed alumina and colloidal alumina with an organic resin, The primary particle diameter of the abrasive is 0.01 to 1 μm, the concentration in the polishing composition is 3 to 30% by weight, and the concentration of the organic acid (B) in the polishing composition is 0.01 to 10%. % By weight, and the concentration of (C) hydrogen peroxide in the polishing composition is 0.0
3 to 10% by weight, and the concentration of (D) benzotriazole or its derivative in the polishing composition is 0.01 to 10%.
% By weight, (E) the polishing rate modifier is a salt of an inorganic acid or an organic acid and a basic compound, and the concentration in the polishing composition is 0.001 to 1% by weight. is there.

In a further preferred form, the organic acid is at least one selected from oxalic acid, succinic acid, citric acid, tartaric acid, malic acid, lactic acid, and amino acids,
A polishing composition in which the polishing rate modifier is at least one salt selected from sodium carbonate, potassium carbonate, sodium sulfate, potassium sulfate, potassium oxalate, sodium oxalate, and ammonium oxalate.

Further, when the three layers of the insulating layer, the barrier metal layer and the wiring metal layer are flatly polished, the polishing composition described above is used to polish the uppermost wiring metal layer. In this case, the polishing pressure is 7 to 35 KPa, and when the second barrier metal layer is reached, the polishing pressure is 35 to 70 KP.
This is a polishing method in which the polishing pressure is raised to a and the polishing pressure is again reduced to 7 to 35 KPa before polishing of the barrier metal layer is completed and up to the third insulating layer is polished. A more preferable form is a polishing method in which the insulating layer is SiO ₂ , the barrier metal layer is Ta or TaN, and the wiring metal layer is a Cu layer.

[0014]

DETAILED DESCRIPTION OF THE INVENTION As a result of various studies in order to solve the above problems, the present invention uses a specific polishing composition and raises the polishing pressure at the end of polishing of a wiring metal layer. After polishing by increasing the initial polishing pressure of the layer and then lowering the polishing pressure again, the polishing rate for the metal film is large when polishing the wiring metal layer, and the barrier metal layer is removed when polishing the barrier metal layer. The present inventors have completed the invention by discovering that one type of polishing composition slurry having a high polishing rate and a low polishing rate for a wiring metal layer can be used for polishing.

The abrasive used in the present invention is at least one selected from fumed silica, colloidal silica, fumed alumina, and colloidal alumina.
It is a kind of inorganic particles, and the surface of the inorganic particles is composed of particles coated with an organic resin.

The method of coating the inorganic particles with the organic resin is, for example, a method of polymerizing on the surface of the particles with a radical initiator such as peroxide fixed on the surface of the inorganic particles, a silane coupling agent having a side chain of a certain molecular weight, etc. The surface of the inorganic particles
Method of reacting with OH group (Koji Yoshinaga: Coloring material, 72 [8],
501-509 (1999)) or a method of making composite particles by colliding organic resin fine particles having a smaller diameter with inorganic particles in a high-speed air flow (Masumi Koishi, Ed .: Fine Particle Design, Industrial Research Committee, (1987)) Known methods can be used. Here, examples of the organic resin include polyolefin such as polyethylene and polypropylene, acrylic resin such as polymethylmethacrylate, elastomer such as polybutadiene, phenol resin and melamine resin, and the like.

These may be used alone or in any combination. The combination and ratio are not particularly limited. Further, these abrasives prevent the occurrence of scratches due to the abrasive on the surface of the object to be polished,
It is preferable that the particles have a relatively uniform particle diameter and a small diameter so that the composition does not change due to precipitation during storage.

The primary particle size of the abrasive can be observed with a scanning electron microscope, but it is preferably in the range of 0.01 to 1 μm. If it is less than the lower limit, the polishing rate is hard to increase, which is not preferable, and if it exceeds the upper limit, scratches are likely to occur on the surface of the object to be polished, which is not preferable.

The concentration of the abrasive in the polishing composition is 3 to 30.
It is desirable that the content is wt%. If the concentration of the abrasive is too low, the mechanical polishing ability will decrease and the polishing rate will decrease, which is not preferable.If the concentration is too high, the mechanical polishing ability will increase and the polishing rate of the tantalum compound cannot be suppressed. However, the selectivity is lowered, which is not preferable.

The polishing composition of the present invention contains an organic acid. The organic acid is not particularly limited, but is preferably at least one selected from oxalic acid, succinic acid, citric acid, tartaric acid, malic acid, lactic acid, and amino acid. The concentration in the polishing composition is preferably 0.01 to 10% by weight. If the amount is less than 0.01% by weight, the polishing rate of the copper film becomes small, which is not preferable and is 10% by weight.
If it exceeds, the polishing rate of the copper film becomes excessively large and cannot be controlled, which is not preferable.

Hydrogen peroxide is used in the polishing composition of the present invention. Hydrogen peroxide exerts an oxidizing action on a metal of a wiring metal layer such as a copper film and promotes ionization, thereby increasing the polishing rate of the metal. The concentration in the polishing composition is preferably 0.03 to 10% by weight. If the concentration in this range is increased or decreased too much, the polishing rate of the metal of the wiring metal layer and the metal of the barrier metal layer is lowered, which is not preferable.

The polishing composition of the present invention contains benzotriazole or its derivative as an antioxidant, and the concentration in the polishing composition is 0.01 to 10% by weight. 0.0
If it is less than 1% by weight, the effect of antioxidation is poor and defects are likely to occur on the copper surface, which is not preferable.
If it exceeds, the polishing rate of the copper film is extremely reduced, which is not preferable.

The polishing composition of the present invention contains a polishing rate modifier. The polishing rate modifier adjusts the polishing rate of the metal of the wiring metal layer and the metal of the barrier metal layer. The polishing rate modifier is preferably an inorganic acid or organic acid and a basic compound. Examples include sodium carbonate, potassium carbonate, sodium sulfate, potassium sulfate, potassium oxalate, sodium oxalate, ammonium oxalate, and the like. At least one selected from the above is preferable. The concentration in the polishing composition is 0.001 to 1% by weight
Is. If it is less than the lower limit, the effect of lowering the metal polishing rate of the wiring metal layer is poor, and therefore it is not preferable.

The medium of the polishing composition of the present invention is water,
It is desirable that ionic impurities and metal ions are reduced as much as possible. The amount of water in the polishing composition is 40-9.
It is 5% by weight. If it is less than the lower limit, the slurry viscosity becomes high and the workability is lowered, or heat is generated during polishing, which is not preferable, and if it exceeds the upper limit, the polishing rate is lowered and polishing selectivity is lowered, which is not preferable.

The polishing composition of the present invention is produced by mixing, dissolving and dispersing in water each of the above components, the abrasive, the organic acid, the oxidizing agent, the antioxidant and the polishing rate modifier. Hydrogen peroxide
Immediately before polishing, the above-mentioned mixed solution is added and mixed, but it is also possible to mix it in advance. The mixing method can be performed by any device. For example, a blade type rotary stirrer, an ultrasonic disperser, a bead mill disperser, a kneader, a ball mill and the like are applicable.

In addition to the above components, various polishing aids may be blended. Examples of such a polishing aid include a dispersion aid, a rust preventive, an antifoaming agent, a pH adjuster, an antifungal agent, and the like. These improve dispersion storage stability of the slurry and polishing rate. It is added for the purpose. Examples of the dispersion aid include sodium hexametaphosphate and the like. Of course, it is needless to say that various surfactants and the like can be added to improve the dispersibility. Preservatives include benzotriazole and its derivatives. Examples of the pH adjuster include basic compounds such as ammonia and acidic compounds such as acetic acid, hydrochloric acid and nitric acid. Liquid paraffin as an antifoaming agent,
Dimethyl silicone oil, stearic acid mono, diglyceride mixture, sorbitan monopalmitiate and the like can be mentioned.

The most important factor in the polishing method of the present invention is pressure. The uppermost wiring metal is formed by using the above-described polishing composition when flatly polishing a three-layer structure including an insulating layer such as SiO ₂ , a barrier metal layer such as Ta, and a metal wiring layer such as a Cu layer. When polishing the metal of the layer, the polishing pressure is 7 to 35 KPa, and when the second barrier metal layer such as Ta is reached, the polishing pressure is increased to 35 to 70 KPa, and the polishing of the barrier metal layer is completed. It is preferable to lower the polishing pressure to 7 to 35 KPa again and polish the third insulating layer such as SiO ₂ as well. In this way, it is desirable to change the polishing pressure for each polishing target when polishing the metal of the metal wiring layer at a pressure not exceeding 35 KPa. This is preferable because if it does not exceed 35 KPa, the surface will be polished with the organic resin component and the metal can be polished without damaging it. If it is less than 7 KPa, the polishing rate of the metal decreases, which is not preferable. After the polishing of the metal layer of the metal wiring layer is completed, the polishing pressure is preferably raised to 35 to 70 KPa to polish the metal layer of the barrier metal layer. Within this pressure range, the organic resin fine particles on the surface of the abrasive particles are easily peeled off and the hard barrier metal layer can be polished with the inorganic particles, which is preferable. If it exceeds 70 KPa, the remaining metal layer of the metal wiring layer is likely to be scratched. The polishing pressure is again reduced to 7 to 35 KPa before the insulating layer is polished. If it exceeds 35 KPa, the metal surface of the metal wiring layer and the insulating layer such as SiO ₂ below may be damaged, such as scratches, and if it is less than 7 KPa, the polishing rate practically required cannot be obtained. SiO ₂ is used as the insulating layer, Ta and TaN are used as the barrier metal layer, and a Cu layer is used as the metal wiring layer.
It is preferable in terms of ease of use.

[0028]

EXAMPLES The present invention will be specifically described with reference to Examples. <Example 1> As an abrasive, the average particle size of primary particles is 30 n.
To a 5 wt% ethanol solution of colloidal silica, which is m, is added methyl methacrylate and 2,2′-azobis (aminopropane) dibasic salt as an initiator, and the mixture is heated to 85 ° C. under a nitrogen atmosphere to produce polymethacrylic acid on the surface. The particles covered with methyl were obtained. The average particle size was 100 nm. Using these particles, succinic acid, hydrogen peroxide, benzotriazole, and potassium carbonate were mixed with ion-exchanged water filtered with a cartridge filter of 0.5 μm so as to have the concentrations shown in Table 1, and stirred with a high-speed homogenizer. Then, it was uniformly dispersed to obtain a polishing composition.

<Evaluation of Abrasiveness> An object to be abraded was formed by forming a SiO ₂ film on an 8-inch silicon wafer and having a width of 10 μm and a thickness of 5.
A μm groove was formed using a photoresist, a tantalum film was formed by sputtering to a thickness of 200 Å, and a 15000 Å copper film was prepared by electrolytic plating and polished.

For polishing, a single-side polishing machine having a platen diameter of 600 mm was used. A polyurethane polishing pad IC-1000 / Suba400 manufactured by Rodel Co. (USA) was attached to a surface plate of the polishing machine with a dedicated double-sided tape, and polishing was performed while a polishing liquid composition (slurry) was flowed. The polishing rate of solid electrolytically plated copper is measured in advance with each slurry, and approximately 15,000Å
When the copper was polished, the load was 20 KPa, the number of rotations of the surface plate was 40 rpm, the number of rotations of the wafer was 40 rpm, and the flow rate of the abrasive composition was 200 ml / min.

Thereafter, the polishing pressure was increased to 50 KPa and the polishing pressure was increased to 20
Before the polishing of the 0Å tantalum film was completed, the pressure was lowered to 20 KPa to complete the polishing. 10 after cleaning and drying the wafer
The dishing amount of the copper wiring having a width of μm was measured by using an atomic force microscope. The polishing time for the copper film and the tantalum film was measured in advance for each solid film under the above-mentioned polishing conditions, and the respective time was based on the time obtained by dividing the thickness of each film by the polishing rate. The ratio of the polishing rate of copper to the polishing rate of tantalum was defined as the selection ratio. In addition, the polished surface was observed with an optical microscope to examine the polished state and classified into the following ranks. ⊚: Good, ○: Slightly lacking smoothness in part, but generally good, ×: Insufficient smoothness, XX: Remarkably corroded and not smooth

<Examples 2 to 7, Comparative Examples 1 to 5> A polishing composition was prepared in the same manner as in Example 1 with the formulations shown in Table 1, and the polishing property was evaluated in the same manner as in Example 1. .

<Comparative Example 6> The same polishing evaluation as in Example 1 was carried out except that the polishing composition obtained in the formulation shown in Table 1 was used, and polishing was performed at a pressure of 28 KPa from the beginning to the end. Carried out.

The evaluation results are shown in Table 1.

[Table 1]

[0035]

According to the present invention, a polishing liquid composition capable of preferentially polishing a copper film is obtained in a CMP process of a semiconductor device containing a copper film and a tantalum film, and a semiconductor device is efficiently manufactured. can do.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a polishing process of a device having a copper film formed thereon.

[Explanation of symbols]

1. Cu 2. Ta 3. SiO ₂

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) H01L 21/304 H01L 21/304 622R

Claims (5)

[Claims] 1. A polishing composition comprising (A) an abrasive, (B) an organic acid, (C) hydrogen peroxide, (D) benzotriazole or a derivative thereof, (E) a polishing rate modifier, and (F) water. (A) abrasive is fumed silica,
A composition comprising at least one kind of inorganic particles selected from colloidal silica, fumed alumina, and colloidal alumina coated with an organic resin, wherein the abrasive has a primary particle diameter of 0.01 to 1 μm. The concentration in the polishing composition is 3 to 30% by weight, the concentration of (B) the organic acid in the polishing composition is 0.01 to 10% by weight, and the concentration of (C) hydrogen peroxide in the polishing composition. Is 0.03 to 10% by weight
And (D) the concentration of benzotriazole or its derivative in the polishing composition is 0.01 to 10% by weight,
(E) The polishing rate modifier is a salt of an inorganic acid or an organic acid and a basic compound, and the concentration in the polishing composition is 0.001.
~ 1% by weight, a polishing composition. 2. The polishing composition according to claim 1, wherein the organic acid is at least one selected from oxalic acid, succinic acid, citric acid, tartaric acid, malic acid, lactic acid, and amino acids. 3. The polishing rate modifier is at least one salt selected from sodium carbonate, potassium carbonate, sodium sulfate, potassium sulfate, potassium oxalate, sodium oxalate, and ammonium oxalate. Polishing composition. 4. An insulating layer, a barrier metal layer, and a wiring metal layer
The polishing composition according to claim 1 is used to flatly polish a layer consisting of layers, and the polishing pressure is 7 to 35 KPa when polishing the uppermost wiring metal layer. The polishing pressure is 35 to 70 KP when the barrier metal layer is reached.
The polishing method is characterized in that the polishing pressure is raised to a and the polishing pressure is again reduced to 7 to 35 KPa before polishing of the barrier metal layer is finished, and up to the third insulating layer is polished. 5. The insulating layer is SiO ₂ , and the barrier metal layer is Ta.
Alternatively, the polishing method according to claim 4, wherein TaN and the wiring metal layer are Cu layers.