JP2005136118A - Polishing composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing composition, in which there are the problems that, when a semiconductor device having a copper film and a tantalum compound is polished, a polish selection ratio of the copper and the tantalum compound is not sufficient, and, when a selection ratio to the copper is raised, a copper film of a wiring groove or hole is deleted excessively, the smoothness of the front surface of the copper film is spoiled, etc., and these problems are improved. <P>SOLUTION: The polishing composition is obtained by mixing colloidal silica having a mean particle size of 30 nm, a copolycondensate of PMMA having a mean particle size of 40 nm and divinylbenzene, a tartaric acid, a benzotriazol and a hydrogen peroxide with an ion exchange water filtered with a 0.5 μm cartridge filter to become a specific concentration, by agitating the mixture by a high speed homogenizer, and by dispersing it uniformly. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polishing composition used for polishing semiconductors, various memory hard disk substrates and the like, and more particularly to a polishing composition suitably used for surface planarization of semiconductor device wafers.

  Recent advances in the electronics industry have evolved into transistors, ICs, LSIs, and super LSIs. As the degree of integration of circuits in these semiconductor elements has increased rapidly, the design rules for semiconductor devices have become finer year by year. The depth of focus in the device manufacturing process has become shallower, and the flatness of the pattern formation surface has become increasingly severe

  On the other hand, in order to cover the increase in wiring resistance due to the miniaturization of wiring, copper wiring having a smaller electrical resistance has been studied as a wiring material from aluminum or tungsten. However, when copper is used for interconnection between wiring layers and wirings, after forming wiring grooves and holes on the insulating film, a copper film is formed by sputtering or plating, and unnecessary portions are chemically and mechanically polished. It is necessary to remove unnecessary copper on the insulating film by (CMP).

  In such a process, copper diffuses into the insulating film and degrades 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 copper diffusion. ing.

In the planarization CMP process of the device having the copper film formed as 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, and the next step Then, the tantalum compound layer on the insulating film must be polished and the polishing must be completed when the SiO ₂ surface comes out. Such a process is shown in FIG. 1, and CMP polishing in such a process requires that the polishing rate be selective with respect to different materials such as copper, a tantalum compound, and SiO ₂ .

That is, in Step 1, the polishing rate with respect to copper is high and the tantalum compound needs to be selective enough to have no polishing ability. Further, in step 2, the polishing rate for the tantalum compound is large, but the smaller the polishing rate for SiO ₂ is, the more preferable it is because it is possible to prevent excessive polishing of SiO ₂ .

Ideally, this process can be polished with a single abrasive, but the selectivity of the polishing rate for different materials cannot be changed during the process, so the process is divided into two steps and has different selectivity. Each CMP step is performed with two slurries. In order to prevent excessive etching (dishing, recessing, erosion) of the copper film in the normal groove or hole, the polishing is finished in step 1 with a little copper film on the tantalum compound left. In step 2, the remaining copper and tantalum compound are removed by polishing using the SiO ₂ layer as a stopper.

  For the polishing composition used in Step 1, it is necessary to have a large polishing rate only for the copper film without causing surface defects (scratches) that cannot be corrected in Step 2.

As such a polishing composition for a copper film, Patent Document 1 discloses a polishing composition containing at least one organic acid selected from aminoacetic acid and amidosulfuric acid, an oxidizing agent, and water. . This polishing composition has a relatively high polishing rate with respect to copper, and this is because copper ionized by an oxidizing agent forms a chelate with the above organic acid and is easily mechanically polished. It can be estimated that this is because
However, when polishing a semiconductor device having a copper film and a tantalum compound using the polishing composition, the polishing selectivity of copper and tantalum compound is not sufficient, or if the selectivity to copper is increased, the wiring trench and hole copper There have been problems such as excessive film shaving and loss of smoothness on the copper film surface.
JP-A-7-233485

An object of the present invention is to provide a polishing composition having a high selectivity in which the polishing rate of copper is high but the polishing rate of tantalum compound is low in the CMP process of a semiconductor device having a copper film and a tantalum compound. It is a polishing composition for CMP processing excellent in smoothness of the copper film surface.

  The present invention is a polishing composition containing (A) colloidal silica, (B) organic resin fine particles, (C) an organic acid (D) benzotriazole, (E) hydrogen peroxide and (F) water, A) The average particle diameter of colloidal silica is in the range of 10 to 200 nm, the concentration in the polishing composition is 0.1 to 5% by weight, and (B) the average particle diameter of the organic resin fine particles is 10 to 200 nm. The concentration in the polishing composition is 0.1 to 5% by weight, and (C) the organic acid is at least selected from oxalic acid, succinic acid, malic acid, tartaric acid, citric acid and lactic acid One or more, the concentration in the polishing composition is 0.01 to 5% by weight, and the concentration of (D) benzotriazole in the polishing composition is 0.0001 to 0.5% by weight. Yes, (E) The concentration of hydrogen peroxide in the polishing composition is 0 A polishing composition characterized by from 01 to 5 percent by weight.

  ADVANTAGE OF THE INVENTION According to this invention, the polishing composition which can grind | polish a copper film preferentially in the CMP processing process of the semiconductor device containing a copper film and a tantalum film is obtained, and a semiconductor device can be manufactured efficiently.

As a result of various investigations to solve the above-mentioned problems, the present invention uses a polishing composition containing a specific abrasive, compound, oxidant and water, so that the polishing rate for a copper film is large and tantalum is used. The inventors have found that the polishing rate with respect to the compound is small, that high selectivity can be obtained, and that the smoothness of the copper film surface is excellent, and that the present invention has been completed.

The present invention includes colloidal silica as an abrasive. Colloidal silica is mainly effective in increasing the polishing rate. The average particle size of colloidal silica is preferably in the range of 10 to 200 nm. If it is smaller than 10 nm, it is not preferable because the polishing rate is difficult to increase. Moreover, it is preferable that the density | concentration in the polishing composition of colloidal silica is the range of 0.1-5 weight%. If it is less than 0.1% by weight, it is not preferable because the effect of increasing the polishing rate is small even if it is added. .

  The organic resin fine particles used in the present invention are used to reduce the polishing rate of the tantalum compound and increase the selectivity with copper. It is considered that the organic resin fine particles act as an abrasive for a relatively soft copper film and as a cushion material for a hard tantalum compound. It is not particularly limited as long as it is a fine particle of an organic polymer compound, but for example, an organic polymer compound obtained by polycondensation such as fine particles of an organic polymer compound obtained by emulsion polymerization of a vinyl monomer, polyester, polyamide, polyimide, polybenzoxazole or the like. Examples thereof include fine particles of molecular compounds and fine particles of organic polymer compounds obtained by addition condensation such as phenol resin and melamine resin, and these can be used alone or in any combination. A vinyl polymer having a relatively low price and a uniform particle size is preferred.

  The average particle diameter of the organic resin fine particles of the present invention is preferably in the range of 10 to 200 nm. If it is smaller than 10 nm, the effect of reducing the polishing rate of the tantalum compound is not seen, and this is not preferred, and if it exceeds 200 nm, it is difficult to disperse the particles. The concentration of the organic resin fine particles in the polishing composition is desirably 0.1 to 5% by weight. If the concentration is less than 0.1% by weight, no effect is seen even if organic resin fine particles are added, and if it exceeds 5% by weight, it becomes difficult to disperse the particles, and problems such as aggregation and sedimentation tend to occur. .

  The polishing composition of the present invention contains an organic acid. The organic acid in the present invention is preferable because it forms a chelate with copper and easily controls the polishing rate of copper. Specific examples include at least one organic acid selected from oxalic acid, succinic acid, malic acid, tartaric acid, citric acid and lactic acid. About addition amount, it uses in the range of 0.01 to 5 weight% in polishing composition. If it is less than 0.01% by weight, the chelate-forming effect is insufficient, and if it exceeds 5% by weight, the polishing rate cannot be controlled and overpolishing is not preferable.

The polishing composition of the present invention contains benzotriazole. The concentration in the polishing composition is preferably 0.0001 to 0.5% by weight. If it is less than 0.0001% by weight, the polishing rate of the copper film cannot be controlled sufficiently, which is not preferable, and if it exceeds 0.5% by weight, the polishing rate of the copper film extremely decreases, which is not preferable.

  The polishing composition of the present invention contains hydrogen peroxide. In the polishing composition of the present invention, hydrogen peroxide acts as an oxidizing agent. Hydrogen peroxide exerts an oxidizing action on the copper film and works to increase the polishing rate of the copper film by promoting ionization, but the concentration in the polishing composition is 0.01 to 5% by weight. It is desirable. If the concentration in this range is too high or too low, the polishing rate of the copper film decreases, which is not preferable.

  The medium of the polishing composition of the present invention is water, and it is desirable to reduce ionic impurities and metal ions as much as possible.

  The polishing composition of the present invention is produced by mixing, dissolving, and dispersing the above-described components, colloidal silica, organic resin fine particles, organic acid, and benzotriazole in water. Hydrogen peroxide is added to and mixed with the above-mentioned liquid mixture immediately before polishing, but can also be mixed in advance. The mixing method can be performed with any apparatus. 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 polishing aids include dispersants, rust inhibitors, antifoaming agents, pH adjusters, fungicides, etc., and these are intended to improve the dispersion storage stability of the slurry and the polishing rate. Added in. Needless to say, the dispersibility can be improved by adding a water-soluble polymer such as polyvinyl alcohol. Examples of the pH adjuster include basic compounds such as ammonia, acetic acid, hydrochloric acid, nitric acid and the like. Examples of antifoaming agents include liquid paraffin, dimethyl silicone oil, stearic acid glyceride mixture, sorbitan monopalmitate and the like.

The present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
<Example 1>
Colloidal silica with an average particle size of 30 nm, co-condensate of polymethyl methacrylate (PMMA) with an average particle size of 40 nm and divinylbenzene, hydrogen peroxide, tartaric acid, and benzotriazole so that the concentrations shown in Table 1 are 0.5 μm. Was mixed with ion-exchanged water filtered with a cartridge filter of No. 1 and stirred uniformly with a high-speed homogenizer to uniformly disperse to obtain the polishing composition of Example 1.

<Abrasiveness evaluation>
The object to be polished was prepared by forming a 1500-inch tantalum (Ta) film by sputtering on an 8-inch silicon wafer and 15000-thick copper film by electrolytic plating, and polishing the copper and Ta surfaces.

For polishing, a single-side polishing machine having a surface plate diameter of 600 mm was used. A polyurethane polishing pad IC-1000 / Suba400 manufactured by Rodel (USA) was attached to the surface plate of the polishing machine, and a copper and tantalum film was polished for 1 minute while flowing the polishing composition (slurry). As polishing conditions, the load was 300 g / cm ² , the rotation speed of the surface plate was 40 rpm, the rotation speed of the wafer was 40 rpm, and the flow rate of the polishing composition was 200 ml / min.

The polishing rate (Å / min) was determined by determining the film thickness that decreased after washing and drying the wafer. The ratio of the polishing rate of copper to the polishing rate of tantalum was taken as the selection ratio. Further, the polished surface was examined by observing the polished surface with an optical microscope, and the following ranking was performed.
◎: Good, ○: Partially slightly smooth but usable, △: Good smoothness but partial corrosion, ×: Corrosion occurred

<Examples 2-6, Comparative Examples 1-6>
Colloidal silica AB, organic resin fine particles AB, hydrogen peroxide, organic acid, and benzotriazole were mixed with ion-exchanged water filtered through a 0.5 μm cartridge filter so as to have the concentrations shown in Table 1. The composition for polishing was prepared in the same manner as in Example 1 by stirring with a high-speed homogenizer and uniformly dispersed, and the polishing property was evaluated in the same manner as in Example 1.
The evaluation results are shown in Table 1.

  The polishing composition of the present invention is suitably used for surface planarization of a semiconductor device wafer.

Schematic of polishing process for devices with copper film

Explanation of symbols

1 Cu
2 Ta
3 SiO ₂

Claims (1)

A polishing composition containing (A) colloidal silica, (B) organic resin fine particles, (C) organic acid (D) benzotriazole, (E) hydrogen peroxide and (F) water, and (A) colloidal The average particle diameter of silica is in the range of 10 to 200 nm, the concentration in the polishing composition is 0.1 to 5% by weight, and the average particle diameter of the organic resin fine particles is in the range of 10 to 200 nm. The concentration in the polishing composition is 0.1 to 5% by weight, and (C) the organic acid is at least one selected from oxalic acid, succinic acid, malic acid, tartaric acid, citric acid and lactic acid The concentration in the polishing composition is 0.01 to 5% by weight, the concentration of (D) benzotriazole in the polishing composition is 0.0001 to 0.5% by weight, E) The concentration of hydrogen peroxide in the polishing composition is 0.01 to Polishing composition characterized by percentages by weight.

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