JP2005136255A - Abrasive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive composition that can reduce the erosion, caused when a wiring concentrating area is polished excessively as compared with a non-wiring area to ≤30 nm in an area having a narrow wiring width, during the course of a CMP process performed on a semiconductor device, having a copper film, a barrier layer composed of a tantalum compound, and an SiO<SB>2</SB>insulating layer. <P>SOLUTION: The abrasive composition is obtained by mixing colloidal silica having the association ratio of 1.5 and the mean particle diameter of primary particles of 20 nm, polymethyl methacrylate having a ratio of the weight-average particle diameter to the number-average particle diameter (weight-average molecular weight/number-average molecular weight) of 1.00-1.50 and the mean particle diameter of 30 nmm, oxalic acid, hydrogen peroxide, and benzotriazole as abrasives in ion-exchanged water filtered through a 0.5 μm cartridge filter and uniformly dispersing the abrasives in the water by agitating the water with a high-speed homogenizer. <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. Accordingly, the depth of focus in the device manufacturing process has become shallow, and the flatness of the pattern forming 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. (CMP) removes unnecessary copper on the insulating film.

  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, it is necessary to polish the tantalum compound layer on the insulating film, and then polish Cu and SiO ₂ by optimum amounts depending on the wiring width, wiring depth, and the like. Although such a process is shown in FIG. 1, the 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, while suppressing erosion and dishing, the polishing rate for the tantalum compound is large, the polishing rate for Cu is 200 to 500 (Å / min), and the polishing rate for SiO ₂ is 100 to 500 (Å / min). It is necessary to be able to polish the optimum amount.

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 step 1, the polishing is completed with the copper film on the tantalum compound completely removed. Next, in step 2, the Ta layer is completely removed, and the SiO ₂ layer and Cu are polished and removed in an appropriate amount to be planarized.

For the polishing composition used in Step 2, the polishing rate necessary for selectively polishing the tantalum compound mainly from the state polished in Step 1 is about 1000 to 1100 (Å / min.). The copper polishing rate is preferably 200 to 500 (Å / min.), And the SiO ₂ polishing rate is preferably about 100 to 500 (Å / min.).

As such a polishing composition for Step 2 polishing, a polishing composition containing colloidal silica, hydrogen peroxide, benzotriazole, oxalic acid and water and adjusted to pH 2 to 5 with KOH or the like is disclosed in Patent Document 1. Is shown in However, this polishing composition has a copper polishing rate larger than that of the tantalum compound, but the ratio is about 3 and the selectivity is not sufficient. Moreover, although the 2nd step polishing composition which used the organic particle and the inorganic particle together for the abrasive grain is shown by patent document 2, it is a composition by which hydrogen peroxide, an acetic acid, KOH, maleate, etc. were mix | blended. However, the selectivity of polishing between the tantalum compound and copper was about 1.1, and the selectivity of polishing between the tantalum compound and SiO ₂ was about 1.2, indicating that the selectivity was not sufficient.

In addition, when the conventional polishing composition is used, in the region where the wiring width is narrow, the wiring dense region is polished excessively compared to the non-wiring region, and the insulating film in the wiring dense region becomes thinner than the non-wiring region. There is a problem that erosion, which is a phenomenon that occurs, or dishing, which is a phenomenon that the center of the Cu wiring becomes thin, is likely to occur.
JP 2001-247853 A JP 2001-196336 A

The present invention relates to an erosion caused by excessive polishing of a wiring dense region in a narrow wiring width region compared to a non-wiring region in a CMP processing process of a semiconductor device having a copper film, a tantalum compound barrier layer, and an SiO ₂ insulating layer. It is providing the polishing composition which can be 30 nm or less.

The present invention
A polishing composition comprising (A) an abrasive, (B) an organic acid, (C) an oxidant, (D) an antioxidant, and (E) water, wherein (A) the abrasive is an average particle The main component is a (methyl methacrylate / divinylbenzene) copolymer having a diameter of 1 nm to 35 nm, and the ratio of the weight average particle diameter to the number average particle diameter (weight average molecular weight / number average molecular weight) is in the range of 1.00 to 1.50. A mixture of inorganic particles composed of at least one of fumed silica, colloidal silica, fumed alumina, and colloidal alumina having an association ratio of 1.5 or less and an average particle size in the range of 15 nm to 25 nm. The weight ratio of organic particles to inorganic particles is in the range of 95/5 to 0/100, the concentration in the polishing composition is 2 to 10% by weight, and (B) the main component of the organic acid is Shu Acid and polishing set The concentration in the composition is 0.01 to 1.0% by weight, (C) the oxidizing agent is hydrogen peroxide, the concentration in the polishing composition is 0.05 to 1.0% by weight, (D) The antioxidant is benzotriazole or a derivative thereof, and the concentration in the polishing composition is 0.01 to 1.0% by weight. Preferably, the wet etching rate of copper is 5 (ｍｉｎ / min). Hereinafter, the polishing composition is characterized in that erosion and dishing are 30 nm or less.

  According to the present invention, in the case of a polishing composition using inorganic particles such as colloidal silica having an association ratio of 1.5 or less and an average particle size of 15 to 25 nm, the erosion should be 1/2 or less of the above-described one. In the polishing composition in which an organic resin having a ratio of the weight average particle diameter to the number average particle diameter (weight average molecular weight / number average molecular weight) in the range of 1.00 to 1.50 is mixed, the erosion is further increased by 1 It can be reduced by about 20%.

 As a result of various investigations in order to solve the above-mentioned problems, the present invention results in an organic abrasive grain comprising a resin particle specific to a polishing composition comprising an inorganic abrasive grain, an organic acid, an oxidizing agent, a benzotriazole compound, and water. By using the copper, the wet etching rate of copper can be reduced to 5 (） / min) or less, and the erosion caused by excessive polishing of the wiring dense region as compared with the non-wiring region can be reduced to 30 nm or less in the region where the wiring width is narrow. And found the invention.

The abrasive used in the present invention is a mixture of organic particles and inorganic particles made of a specific resin having a specific average particle size and a specific compounding ratio.
The organic particles of the present invention are (methyl methacrylate / divinylbenzene) copolymer having an average particle size of 1 nm to 35 nm. If it exceeds 35 nm, the polishing rate of the copper film increases, which is not preferable.

 The organic particles of the present invention have a ratio of weight average particle diameter to number average particle diameter (weight average molecular weight / number average molecular weight) in the range of 1.00 to 1.50. Outside this range, the abrasive grains made of organic particles cause aggregation and cause scratches and the like, which is not preferable.

 The organic particles are not particularly limited as long as the (methyl methacrylate / divinylbenzene) copolymer is a main component, but are preferably produced by emulsion polymerization that generates particles having a uniform particle size at a relatively low cost.

 The association ratio of the inorganic particles of the present invention is preferably 1.5 or less. Outside this range, erosion is 30 nm or more, which is not preferable.

The average particle size of the inorganic particles of the present invention is preferably in the range of 15 nm to 25 nm. If the thickness is less than 15 nm, the polishing rate at the time of polishing the SiO ₂ film is extremely low, which is not preferable. If the thickness exceeds 25 nm, the Ta film polishing rate becomes low, which is not preferable.

The inorganic particles are a mixture of inorganic particles composed of at least one of fumed silica, colloidal silica, fumed alumina, and colloidal alumina,
These can be used alone or in any combination. Combinations and ratios are not particularly limited.

The weight ratio of organic particles to inorganic particles is preferably in the range of 95/25 to 0/100. If there are more organic particles than this range, the polishing rate at the time of polishing the tantalum film and the SiO ₂ film decreases, which is not preferable.

The concentration of the abrasive in the polishing composition is desirably 2 to 10% by weight. If the concentration of the abrasive is too small, the mechanical polishing ability decreases and the polishing rate decreases, which is not preferable. If the concentration is too high, the mechanical polishing ability increases and selection of polishing of tantalum compound, copper, and SiO ₂ This is not preferable because the properties are lowered.

  The polishing composition of the present invention contains an organic acid. The organic acid is preferably oxalic acid. The concentration in the polishing composition is preferably 0.01 to 1.0% by weight. If it is less than 0.01% by weight, the polishing rate of the tantalum compound film is not preferable because it is not preferable, and if it exceeds 1.0% by weight, the copper film polishing rate becomes large and cannot be controlled.

 The polishing composition of the present invention contains an oxidizing agent. Hydrogen peroxide is preferred as the oxidizing agent. Hydrogen peroxide exerts an oxidizing action on the tantalum compound film and works to increase the polishing rate of the tantalum compound film by promoting ionization, but the concentration in the polishing composition is 0.05 to 1.0. It is desirable to be weight percent. If the concentration in this range is too high or too low, the polishing rate of the tantalum compound film decreases, which is not preferable. In addition, 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 0.05 to 1. It is desirable to be 0% by weight. When the concentration is higher than this range, the polishing rate for the copper film becomes too large, and when it is low, the polishing rate for the copper film is extremely lowered.

  The polishing composition of the present invention contains benzotriazole or a derivative thereof as an antioxidant, and the concentration in the polishing composition is 0.01 to 1.0% by weight. If it is less than 0.01% by weight, the effect of suppressing the polishing rate of the copper film becomes poor, which is not preferable. If it exceeds 1.0% by weight, the polishing rate of the tantalum compound film extremely 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 each of the above components, abrasive, organic acid, oxidizing agent, and antioxidant 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. These mixing methods can be carried out in 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 dispersion aids, rust inhibitors, antifoaming agents, pH adjusters, fungicides, etc., but these improve the dispersion storage stability of the slurry and the polishing rate. Added on purpose. Examples of the dispersion aid include sodium hexametaphosphate. Of course, it is needless to say that dispersibility can be improved by adding various surfactants. Examples of the pH adjuster include basic compounds such as ammonia and acidic compounds such as acetic acid, hydrochloric acid and nitric acid. Examples of the antifoaming agent include liquid paraffin, dimethyl silicone oil, stearic acid mono, diglyceride mixture, sorbitan monopalmitate, and the like.

The present invention will be specifically described with reference to examples.
<Example 1>
Colloidal silica having an association ratio of 1.5 and an average primary particle diameter of 20 nm as an abrasive and a ratio of weight average particle diameter to number average particle diameter (weight average molecular weight / number average molecular weight) is 1.00 to 1. Table 1 shows (methyl methacrylate / divinylbenzene) copolymer (methyl methacrylate / divinylbenzene: 95/5 mol%), oxalic acid, hydrogen peroxide, and benzotriazole, having an average particle size of 30 nm. The mixture was mixed with ion-exchanged water filtered through a cartridge filter of 0.5 μm so as to have a concentration, and stirred and dispersed uniformly with a high-speed homogenizer to obtain a polishing composition.

<Polishing evaluation>
The object to be polished was prepared by forming a solid film of SiO ₂ film, tantalum compound film and copper film on an 8-inch silicon wafer, and the polishing rate of each film was measured to obtain the selection ratio.

For polishing, a single-side polishing machine having a surface plate diameter of 600 mm was used. A polishing pad IC-1000 / Suba400 made by Rodel (USA) was attached to the surface plate of the polishing machine with a special double-sided tape, and polishing was performed while flowing the polishing composition (slurry). The load was 3 psi, the rotation speed of the surface plate was 70 rpm, the wafer rotation speed was 72 rpm, and the flow rate of the abrasive composition was 150 ml / min. The wet etching rate was determined from the amount of change in film thickness after placing a Cu wafer in the slurry and stirring at 300 rpm for 10 minutes at room temperature. The pH was measured using a pH meter. For erosion and dishing, the level difference between the non-wiring portion and the wiring portion after 2nd step was measured using a surface roughness meter.
The average particle size was determined from a dynamic scattering particle size measuring machine.

<Examples 2-4, Comparative Examples 1-5>
A polishing composition was prepared in the same manner as in Example 1 according to the formulation shown in Table 1, and the polishing characteristics were evaluated.
The results are shown in Table 1.

 As described above, according to the present invention, a polishing liquid composition capable of preferentially polishing a tantalum compound film in a CMP processing process of a semiconductor device including a copper film and a tantalum film is obtained, and the semiconductor device is efficiently manufactured. It is industrially useful.

Schematic diagram of device polishing process with copper film

Explanation of symbols

1 Cu
2 Ta
3 SiO ₂

Claims (3)

A polishing composition comprising (A) an abrasive, (B) an organic acid, (C) an oxidant, (D) an antioxidant, and (E) water, wherein (A) the abrasive is an average particle The main component is a (methyl methacrylate / divinylbenzene) copolymer having a diameter of 1 nm to 35 nm, and the ratio of the weight average particle diameter to the number average particle diameter (weight average molecular weight / number average molecular weight) is in the range of 1.00 to 1.50. And inorganic particles composed of at least one of fumed silica, colloidal silica, fumed alumina, and colloidal alumina having an association ratio of 1.5 or less and an average particle size in the range of 15 to 25 nm. The mixture ratio of the organic particles and the inorganic particles is in the range of 95/5 to 0/100, the concentration in the polishing composition is 2 to 10% by weight, and (B) the main organic acid The ingredient is oxalic acid, The concentration in the polishing composition is 0.01 to 1.0% by weight, (C) the oxidizing agent is hydrogen peroxide, and the concentration in the polishing composition is 0.05 to 1.0% by weight. And (D) a polishing composition, wherein the antioxidant is benzotriazole or a derivative thereof, and the concentration in the polishing composition is 0.01 to 1.0% by weight. The polishing composition according to claim 1, wherein the wet etching rate of copper is 5 (ｍｉｎ / min) or less. The polishing composition according to claim 1, wherein both erosion and dishing are 30 nm or less.

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