JP2003197572A - Composition for polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for polishing to be used for a CMP process which has a good selectivity in that a polishing rate for copper is large while that for a tantalum compound is small in a CMP process of a semiconductor device having a copper film and a tantalum compound, and which is capable of making the surface of the copper film smooth. <P>SOLUTION: The composition for polishing comprises (A) a polishing substance, (B) quinoxaline and/or quinazoline, (C) organic acid, (D) hydrogen peroxide, and (E) water. The polishing substance is formed of at least one substance among fumed silica, colloidal silica, fumed alumina, and colloidal alumina, and a primary grain diameter of the polishing material is 0.01 to 0.2 μm, and the concentration of the polishing substance in the composition for polishing is 5 to 30 wt.%. <P>COPYRIGHT: (C)2003,JPO

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. [0002] The recent remarkable development of the electronics industry has evolved into transistors, ICs, LSIs, and ultra-LSIs. As the degree of integration of circuits in these semiconductor devices has increased rapidly, 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. 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. 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) quinoxaline and / or quinazoline, (C)
A polishing composition comprising an organic acid, (D) hydrogen peroxide, and (E) water, wherein (A) the polishing material is fumed silica,
Colloidal silica, fumed alumina, and at least one selected from colloidal alumina, the primary particles of the abrasive are 0.01 to 0.2 μm, and the concentration in the polishing composition is 5 to 30% by weight. %
(B) the concentration of quinoxaline and / or quinazoline in the polishing composition is 0.01 to 5% by weight, and (C) the organic acid is at least one or more selected from citric acid, tartaric acid, and malic acid. A polishing composition which is an acid and has a concentration of 0.01 to 5% by weight in the polishing composition and (D) a concentration of hydrogen peroxide in the polishing composition of 0.03 to 5% by weight; It is. 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 made of at least one selected from fumed silica, colloidal silica, fumed alumina and colloidal alumina. These can be used alone or in any combination. The combination and ratio are not particularly limited. [0015] These abrasives have a relatively uniform particle diameter so as to prevent scratches caused by 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, but is preferably in the range of 01 to 0.2 μm. If the value is smaller than the lower limit, the polishing rate is difficult to increase, 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 quinoxaline and / or quinazoline. The concentration in the polishing composition is desirably 0.01 to 5% by weight. If the value is less than the lower limit, the polishing rate of the copper film becomes excessively large and control becomes impossible, so that it is not preferable. 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. Below the lower limit, the chelate formation effect is insufficient,
Exceeding the upper limit is not preferred because the polishing rate cannot be controlled and overpolishing occurs. 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 60 to 9
8% by weight. If the amount is less than the lower limit, the slurry viscosity is increased and the workability is reduced, and heat is generated at the time of polishing. The polishing composition of the present invention is obtained by mixing the above-mentioned components such as an abrasive, a quinoline carboxylic acid, and an organic acid with water.
It is manufactured by dissolving and dispersing. 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. Preservatives include benzotriazole or derivatives thereof. Examples of the pH adjuster include basic compounds such as ammonia and acidic compounds such as acetic acid, hydrochloric acid, and nitric acid. As antifoaming agents, liquid paraffin, dimethyl silicone oil, monostearic acid,
A diglyceride mixture, sorbitan monopalmitate and the like can be mentioned. 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, quinoxaline, 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, and stirred with a high-speed homogenizer. To obtain a polishing composition. <Examples 2 to 8, Comparative Examples 1 to 7> Polishing compositions were prepared in the same manner as in Example 1 by using the formulations shown in Table 1, and the polishing characteristics 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, ×: insufficient smoothness, XX: markedly corroded and smoothness NG. 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 view 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 KM F term (Reference) 3C058 AA07 CB01 DA02 DA12 DA17 5F033 HH11 HH21 MM01 MM12 MM13 PP15 PP27 QQ48 QQ50 WW01 WW04 XX00 XX01 XX03

Claims (1)

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