JP2003151928A - Polishing composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition which has high selectivity, in which the polishing rate for copper is large but the polishing rate for a tantalum compound is small and is superior in giving smoothness of surface to a copper- film in a CMP work process for a semiconductor device, having a copper film and a tantalum compound. SOLUTION: The polishing composition is composed of (A) an abrasive, (B) pyridinecarboxylic acid, (C) an organic acid, (D) hydrogen peroxide, and (E) water, where the abrasive is a composite composed of at least one from among fumed silica, colloidal silica, fumed alumina, and colloidal alumina, and the size of the primary grains of the abrasive is 0.01-0.2 μm.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing composition used for polishing semiconductors, substrates for various types of memory hard disks, etc., and more particularly, to planarizing the surface of semiconductor device wafers. The present invention relates to a polishing composition suitably used for processing. 2. Description of the Related Art With recent remarkable developments in the electronics industry, transistors, ICs, LSIs, and super LSIs have been evolving. As the degree of integration of circuits in these semiconductor devices has rapidly increased, semiconductors have been developed. The design rules of devices have been miniaturized 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 an increase in wiring resistance due to miniaturization of wiring, copper wiring having a lower electric resistance is being studied from aluminum and tungsten as a wiring material. However, when copper is used for wiring layers and interconnections between wirings, after forming wiring grooves and holes on the insulating film, a copper film is formed by sputtering or plating, and the film is formed by chemical mechanical polishing (CMP). Unnecessary copper on the insulating film is removed. In such a process, copper diffuses into the insulating film to deteriorate device characteristics. Therefore, it is usual to provide a tantalum or tantalum nitride layer as a barrier layer on the insulating film in order to prevent the diffusion of copper. It is becoming. [0005] In the planarization CMP process of a device in which a copper film is formed on the uppermost layer as described above, an unnecessary portion of the copper film is first polished to a tantalum compound surface layer formed on the insulating layer. In the next step, the tantalum compound layer on the insulating film must be polished and the polishing must be completed when the SiO ₂ surface comes out. Although such a process is shown in FIG. 1, 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 for copper is high, and the selectivity is such that there is almost no polishing ability for tantalum compounds. Although further polishing rate is greater for Step 2 in tantalum compound SiO ₂
The smaller the polishing rate is, the more preferable it is because it can prevent excessive removal of SiO ₂ . [0007] Ideally, it is desired that this process can be polished with a single abrasive. However, since the selectivity of the polishing rate for different materials cannot be changed during the process, the process is divided into two steps. Each CMP step is performed with two selective slurries. In order to prevent the copper film in the grooves and holes from being excessively ground (dishing, recess, erosion), the polishing is terminated in step 1 with the copper film on the tantalum compound being left slightly. Then, in step 2, a small amount of copper and tantalum compound remaining using the SiO ₂ layer as a stopper is polished and removed. The polishing composition used in step 1 needs to have a high polishing rate only for the copper film without generating surface defects (scratch) that cannot be recovered in step 2. It is. [0009] Such a polishing composition for a copper film is disclosed in JP-A-7-233485.
At least one selected from aminoacetic acid and amidosulfuric acid
This is a polishing composition containing various organic acids, an oxidizing agent, and water. A relatively large polishing rate is obtained for copper, which is presumed to be because copper ionized by the oxidizing agent forms a chelate with the above-mentioned organic acid and is easily polished mechanically. [0010] However, using the polishing composition,
When a semiconductor device having a copper film and a tantalum compound is polished, the polishing selectivity of copper and the tantalum compound is not sufficient. There was a problem that the smoothness was deteriorated. SUMMARY OF THE INVENTION The present invention has a high selectivity that a polishing rate of copper is high but a polishing rate of tantalum compound is low in a CMP processing process of a semiconductor device having a copper film and a tantalum compound. An object of the present invention is to provide a polishing composition and a polishing composition for a CMP process which is excellent in the smoothness of a copper film surface. The present invention provides (A) an abrasive, (B) a pyridinecarboxylic acid represented by the formula (1), (C) an organic acid, (D) hydrogen peroxide, and (E) a polishing composition containing water, wherein (A) the abrasive is at least one selected from fumed silica, colloidal silica, fumed alumina, and colloidal alumina; The particles have a concentration of 0.01 to 0.2 μm, the concentration of (B) in the polishing composition is 5 to 30% by weight, and the concentration of pyridinecarboxylic acid in the polishing composition is 0.01 to 5% by weight. Wherein (C) the organic acid is citric acid,
At least one acid selected from tartaric acid and malic acid; the concentration in the polishing composition is 0.01 to 5% by weight; and (D) the concentration of hydrogen peroxide in the polishing composition. Is 0.03 to 5% by weight. Embedded image DETAILED DESCRIPTION OF THE INVENTION As a result of various studies to solve the above problems, the present invention uses a polishing composition containing a specific abrasive, a specific compound, an oxidizing agent and water. Thereby, the polishing rate for the copper film is large, the polishing rate for the tantalum compound is small, high selectivity can be obtained, and it has been found that excellent results can be obtained also on the smoothness of the copper film surface, and the invention is completed. It has been reached. The abrasive used in the present invention is at least one selected from fumed silica, colloidal silica, fumed alumina, and colloidal alumina.
It consists of types. These can be used alone or in any combination. The combination and ratio are not particularly limited. These abrasives have a relatively small particle diameter so as to prevent the generation of scratches due to the abrasive on the surface of the object to be polished, and to prevent precipitation and change in composition during storage. Is preferred. The primary particle size of the abrasive can be observed with a scanning electron microscope.
Is preferably within the range. If it is smaller than 0.01 μm, it is not preferable because the polishing rate is difficult to increase,
If the thickness exceeds 0.2 μm, scratches are likely to occur on the surface of the object to be polished, and it becomes difficult to suppress the polishing rate of the tantalum compound, which is not preferable. The concentration of the abrasive in the polishing composition is 5 to 30.
% By weight. If the concentration of the abrasive is too low, 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 the polishing rate of the tantalum compound cannot be suppressed. This is not preferred because the selectivity decreases. The polishing composition of the present invention contains a pyridinecarboxylic acid derivative represented by the formula (1). Examples include 2-pyridinecarboxylic acid, 3-pyridinecarboxylic acid, 4-pyridinecarboxylic acid, quinolinic acid, 2,4-pyridinedicarboxylic acid, 2,5-pyridinedicarboxylic acid,
2,6-pyridinedicarboxylic acid, 3,4-pyridinedicarboxylic acid, 3,5-pyridinedicarboxylic acid and the like. The concentration in the polishing composition is desirably 0.01 to 5% by weight. If the amount of the quinoline carboxylic acid is less than 0.01% by weight, the polishing rate of the copper film is small, which is not preferable. If it is more than 5% by weight, the polishing rate of the copper film becomes excessively large and cannot be controlled. The polishing composition of the present invention contains an organic acid. The organic acid in the present invention forms a chelate with copper,
This is preferable because the polishing rate of copper can be easily controlled. Specific examples include at least one organic acid selected from citric acid, tartaric acid, and malic acid. The additive amount is used in the range of 0.01 to 5% by weight in the polishing composition. If it is less than 0.01% by weight, the effect of forming a chelate is insufficient, and if it exceeds 5% by weight, the polishing rate cannot be controlled, resulting in overpolishing, 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 effect on the copper film and has a function of increasing the polishing rate of the copper film by promoting ionization, but the concentration in the polishing composition is 0.03 to 5% by weight. It is desirable. If the concentration is too high or too low, the polishing rate of the copper film is undesirably reduced. [0021] 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 80 to 9
4% by weight. If the amount is less than 80% by weight, the slurry viscosity becomes high and the workability decreases, and heat is generated during polishing, which is not preferable. If the amount exceeds 94% by weight, the polishing rate decreases, and the polishing selectivity decreases. Absent. The polishing composition of the present invention is prepared by mixing, dissolving and dispersing the above-mentioned abrasive, pyridinecarboxylic acid, organic acid and the like in water. Hydrogen peroxide is added to and mixed with the above mixed solution immediately before polishing, but it is also possible to mix them in advance. These mixing methods can be performed with any device. For example, a blade-type rotary stirrer, an ultrasonic disperser, a bead mill disperser, a kneader, a ball mill and the like can be applied. Various polishing aids other than the above components may be blended. Examples of such polishing aids include dispersing aids, rust preventives, defoamers, pH adjusters, fungicides, and the like, which are used to improve the dispersion storage stability of the slurry and the polishing rate. Added for purpose. Examples of the dispersing aid include sodium hexametaphosphate. Of course, it is needless to say that the dispersibility can be improved by adding various surfactants and the like. 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, monostearic acid, a mixture of diglycerides, and sorbitan monopalmitate. EXAMPLES The present invention will be specifically described with reference to Examples. <Example 1> The average particle size of primary particles as an abrasive was 30 n.
m, colloidal silica, hydrogen peroxide, 2-pyridinecarboxylic acid, and citric acid were mixed with ion-exchanged water filtered through a 0.5 μm cartridge filter so as to have the concentration shown in Table 1, The mixture was uniformly dispersed by stirring with a homogenizer to obtain a polishing composition. <Examples 2 to 8 and Comparative Examples 1 to 7> Polishing compositions were prepared according to the formulations shown in Table 1 in the same manner as in Example 1, and the polishing properties were evaluated. <Evaluation of Abrasiveness> An object to be polished was prepared by forming a 2000-inch tantalum (Ta) film on a 6-inch silicon wafer by sputtering and a 10000-cm copper film by electrolytic plating, and the copper and Ta surfaces were polished. . For polishing, a single-side polishing machine having a platen diameter of 600 mm was used. A polishing pad IC-1000 / Suba400 made by Rodale (USA) is attached to the surface plate of the polishing machine with a special double-sided tape, and the copper and tantalum films are polished for 1 minute while flowing a polishing composition (slurry). did.
The polishing conditions were a load of 300 g / cm ² , a rotation speed of the platen of 40 rpm, a wafer rotation speed of 40 rpm, and a flow rate of the abrasive composition of 200 ml / min. After the wafer was washed and dried, the reduced film thickness was determined to determine the polishing rate (Å / min). The ratio of the polishing rate of copper to the polishing rate of tantalum was used as the selectivity. In addition, the polished surface was observed with an optical microscope to check the polished state, and the following ranking was made. ：: good, ：: only a part of the surface was slightly insufficiently smooth, but generally good, ×: insufficiently smooth, XX: markedly corroded and NG. The results are shown in Table 1. [Table 1] According to the present invention, in a CMP process of a semiconductor device including a copper film and a tantalum film, a polishing composition capable of preferentially polishing a copper film can be obtained, and the efficiency of the semiconductor device can be improved. It can be manufactured in a special way.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a polishing process of a device having a copper film formed thereon. Cu 2. Ta3. SiO ₂

Claims (1)

Claims 1. An abrasive (A), a pyridinecarboxylic acid (B) represented by the formula (1), an organic acid (C), hydrogen peroxide (D), and water (E) A polishing composition comprising:
(A) the abrasive is at least one selected from fumed silica, colloidal silica, fumed alumina, and colloidal alumina, and the primary particles of the abrasive are 0.01 to 0.2 μm; B) The concentration in the polishing composition is 5 to 30% by weight, the concentration of pyridinecarboxylic acid in the polishing composition is 0.01 to 5% by weight, and (C) the organic acid is citric acid or tartaric acid. , At least one acid selected from malic acid, the concentration in the polishing composition is 0.01 to 5% by weight, and the concentration of (D) hydrogen peroxide in the polishing composition is A polishing composition characterized by being 0.03 to 5% by weight. Embedded image