JP2003100676A - Abrasive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive composition which can solve the problem that, when a semiconductor device having copper films and a tantalum compound is polished, the polishing selection rates against the copper and tantalum compound become insufficient and, when the selection rate against the copper is raised, copper films in wiring grooves or holes are over-polished or the surface smoothness of the copper films is impaired. SOLUTION: This abrasive composition is composed of an abrasive, 1- hydroxybenzotrizole, malic acid, hydrogen peroxide, polyvinyl alcohol, and water. The abrasive is composed of at least one kind selected from among fumed silica, colloidal silica, fumed alumina, and colloidal alumina and the primary particles of the abrasive have a particle diameter of 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 wiring, after forming wiring grooves and holes on the insulating film, a copper film is formed by sputtering or plating, and unnecessary parts 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 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. FIG. 1 shows such a process. In the CMP polishing in such a process, it is necessary that the polishing rate be selectable 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, but since the selection ratio of the polishing rate for different materials cannot be changed in the course of the process, the process is divided into two steps and different selections are made. Each CMP step is performed with two slurries having properties. 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 corrected 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 due to the fact that 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. Means for Solving the Problems (A) Abrasive, (B) 1
-Hydroxybenzotriazole, (C) malic acid,
A polishing composition comprising (D) hydrogen peroxide, (E) polyvinyl alcohol and (F) water, wherein the polishing material is selected from at least one of fumed silica, colloidal silica, fumed alumina, and colloidal alumina. The primary particles of the abrasive are 0.01 to 0.2 μm, and the respective concentrations in the polishing composition are 5 to 5 in the abrasive.
30% by weight, 0.1% with 1-hydroxybenzotriazole.
1 to 5% by weight, 0.05 to 5% by weight of malic acid, 0.03 to 3% by weight of hydrogen peroxide, and 0.05 to 0.5% by weight of polyvinyl alcohol. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been studied in various ways to solve the above-mentioned problems, and as a result, it has been found that a polishing composition containing a specific abrasive, a compound, an oxidizing agent and water is used. , The polishing rate for the copper film is large, the polishing rate for the tantalum compound is small, it is possible to obtain high selectivity and it is possible to obtain excellent results in the smoothness of the copper film surface, and the invention has been completed. Things. The abrasive used in the present invention comprises at least one selected from fumed silica, colloidal silica, fumed alumina and colloidal alumina. Two or more of these can be used alone or in any combination. The combination and ratio are not particularly limited. Further, these abrasives have a uniform particle diameter so as to prevent generation of scratches caused by the abrasive on the surface of the object to be polished, and to prevent precipitation and change in composition during storage.
Those having a small diameter are preferred. The primary particle size of the abrasive can be observed with a scanning electron microscope, and the particle size is preferably in the range of 0.01 to 0.2 μm. If it is less than 0.01 μm, the polishing rate is not easily increased, and if it exceeds 0.2 μm, it is not preferable because scratches are easily generated on the surface of the object to be polished and it becomes difficult to suppress the polishing rate of the tantalum compound. The concentration of the abrasive in the polishing composition is 5 to 5.
Desirably, it is 30% by weight. When the concentration of the abrasive is less than 5% by weight, the mechanical polishing ability is reduced and the polishing rate is lowered, which is not preferable. When it exceeds 30% by weight, the mechanical polishing ability is increased and the polishing rate of the tantalum compound is suppressed. And the selectivity decreases, which is not preferable. The polishing composition of the present invention contains 1-hydroxybenzotriazole. The concentration in the polishing composition is desirably 0.1 to 5% by weight. If the amount of 1-hydroxybenzotriazole is less than 0.1% by weight, the polishing rate of the copper film becomes small, which is not preferable.
Exceeding the weight percent is not preferred because the polishing rate of the copper film becomes large and the control of the polished surface becomes difficult, or overpolishing tends to occur. In particular, excessive use is not preferred because the smoothness of the surface of the object to be polished is impaired. The polishing composition of the present invention contains malic acid. Malic acid in the present invention is preferable because it forms a chelate with copper and easily controls the polishing rate of copper. About the addition amount of malic acid, 0.05 to 5 in the polishing composition
Use in the range of weight%. If it is less than 0.05% by weight, the effect of forming a chelate is insufficient. 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 3% by weight. It is desirable. If the concentration is too high or too low, the polishing rate of the copper film is undesirably reduced. The polishing composition of the present invention contains polyvinyl alcohol. In the polishing composition of the present invention, polyvinyl alcohol has an effect of uniformly dispersing the abrasive in water, and even if stored for a long period of time, the abrasive is unlikely to settle, and secondary aggregation is likely to cause scratches. Can be prevented. The addition amount is preferably in the range of 0.05 to 0.5% by weight in terms of the concentration in the polishing composition.
If it is less than 5% by weight, the dispersing effect is poor, and if it exceeds 0.5% by weight, the viscosity of the slurry becomes high and the polishing workability 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 components such as the abrasive, 1-hydroxybenzotriazole, malic acid and polyvinyl alcohol in water. It is preferable that hydrogen peroxide is added to and mixed with a liquid mixture obtained by mixing the above components immediately before polishing. The mixing method 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, etc., which are intended to improve the dispersion storage stability of the slurry and the polishing rate. Added in. 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. As the pH adjuster, acetic acid, hydrochloric acid, nitric acid and the like can be mentioned. 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. <Examples 1 to 8 and Comparative Examples 1 to 6> Using colloidal silica as an abrasive, hydrogen peroxide, 1-hydroxybenzotriazole (1-HBT), malic acid, and polyvinyl alcohol were adjusted to the concentrations shown in Table 1. Mixed with ion-exchanged water filtered through a 0.5 μm cartridge filter so as to be uniformly dispersed by stirring with a high-speed homogenizer,
Polishing compositions of Examples 1 to 8 and Comparative Examples 1 to 6 were obtained. Note that hydrogen peroxide was mixed and used immediately before polishing. <Evaluation of Abrasiveness> A 6-inch silicon wafer was prepared as an object to be polished by forming a film of tantalum (Ta) of 2000 ° by sputtering and a film of 10000 ° of copper 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 adhered 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 the polishing composition (slurry). did.
The polishing conditions were a load of 300 g / cm ² , a platen rotation speed of 40 rpm, a wafer rotation speed of 40 rpm, and a flow rate of the polishing 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, ○: can be used even though there is some lack of smoothness,
Δ: Smooth but scratches occurred; X: Smoothness was insufficient. The evaluation 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 diagram of a polishing process of a device having a copper film formed thereon. Cu 2. Ta3. SiO ₂

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/3205 H01L 21/88 MR

Claims (1)

Claims: 1. An abrasive, (B) 1-hydroxybenzotriazole, (C) malic acid, (D) hydrogen peroxide, (E) polyvinyl alcohol and (F) water. Polishing composition, wherein the abrasive is at least one of fumed silica, colloidal silica, fumed alumina, and colloidal alumina, and the primary particles of the abrasive are 0.01 to 0.2 μm. Each concentration in the polishing composition is 5 to 30% by weight for the abrasive and 0.1 to 5 for the 1-hydroxybenzotriazole.
% By weight, 0.05 to 5% by weight of the malic acid, 0.03 to 3% by weight of the hydrogen peroxide, and 0.05 to 0.5% by weight of the polyvinyl alcohol. Composition.