TW201930542A - Slurry for polishing - Google Patents

Abstract

The present invention relates to a polishing slurry for polishing an interlayer insulating film and comprising ceria abrasive grains and an organic ammonium cation having a molecular weight of 155 or less.

Description

Grinding slurry

The present invention relates to a slurry for polishing.

In the polishing slurry for polishing the interlayer insulating film to be polished, a polishing slurry containing cerium oxide abrasive grains is used (for example, Patent Document 1).
[Previous Technical Literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2006-61995

[The problem that the invention wants to solve]

When the abrasive grains are large, the polishing object tends to cause polishing damage. On the other hand, if the abrasive grains are small, the polishing rate tends to decrease. Therefore, the abrasive grains are required to be of a moderate size.

Here, the polishing slurry is subjected to dynamic load (pressure, shear, etc.) during transportation, polishing, or the like, and the abrasive grains in the polishing slurry are aggregated.
As a result, there is a problem that the abrasive grains are likely to be generated and the polishing damage is likely to occur.

Therefore, the present invention has been made in view of the above problems, and it is an object of the invention to provide a polishing slurry which is suppressed in the change in the size of abrasive grains.
[Technical means to solve the problem]

The polishing slurry of the present invention is used for polishing an interlayer insulating film and contains:
Cerium oxide abrasive grains; and organic ammonium cations having a molecular weight of 155 or less.

Hereinafter, an embodiment of the present invention will be described.

The polishing slurry of the present embodiment is used for polishing an interlayer insulating film.
Examples of the interlayer insulating film include a ruthenium oxide film, a tantalum nitride film, and a Low-k film.
Examples of the ruthenium oxide film include a film containing SiO ₂ formed by plasma CVD (Chemical Vapor Deposition) using tetraethoxy decane (TEOS).
Further, the above Low-k film means a film having a relative dielectric constant lower than that of the yttrium oxide film (SiO ₂ film).

Further, the polishing slurry of the present embodiment contains cerium oxide abrasive grains and an organic ammonium cation having a molecular weight of 155 or less.
Further, the polishing slurry of the present embodiment further contains an alkali and water.

The polishing slurry of the present embodiment can be used for polishing after being diluted with water or the like, or can be directly used for polishing without dilution.

The pH of the polishing slurry of the present embodiment is preferably from 8 to 12, more preferably from 10 to 12. The polishing slurry of the present embodiment has a preferable pH value by containing the above-mentioned alkali.

When the polishing slurry of the present embodiment is directly used for polishing without being diluted, it is preferably 1.0 to 25% by mass of cerium oxide abrasive particles, more preferably 5.0 to 20% by mass, and further preferably It is contained in an amount of 9.0 to 14% by mass.
Further, when the polishing slurry of the present embodiment is used after being diluted (for example, when the components other than water are diluted to a half concentration), it is preferable to contain 1.5 to 40% by mass of cerium oxide abrasive grains. More preferably, it contains 10 to 30% by mass, and more preferably 20 to 26% by mass.

In addition, the polishing slurry of the present embodiment preferably contains 0.1 to 1.0 part by mass of the organic ammonium cation, more preferably 0.1 to 0.25 part by mass, based on 100 parts by mass of the cerium oxide abrasive particles.
In the polishing slurry of the present embodiment, the organic ammonium cation is contained in an amount of 0.1 part by mass or more based on 100 parts by mass of the cerium oxide abrasive grains, whereby the change in the size of the abrasive grains is further suppressed.
In addition, the polishing slurry of the present embodiment contains 1.0 part by mass or less of the above-mentioned organic ammonium cation with respect to 100 parts by mass of the above-mentioned ceria abrasive grains, thereby having an advantage that the polishing rate can be improved.

The molecular weight of the above organic ammonium cation is preferably 135 or less, more preferably 35 to 95, still more preferably 70 to 90, and still more preferably 75 to 90.
The above organic ammonium cation is represented by the following formula (1). Further, regarding the following formula (1), R ₁ is H or a monovalent organic group, R ₂ is H or a monovalent organic group, R ₃ is H or a monovalent organic group, and R ₄ is H or a monovalent organic group. . However, the case where R ₁ , R ₂ , R ₃ and R ₄ are all H is excluded.
Examples of the monovalent organic group include an alkyl group, an allyl group, and an aromatic alkyl group.
R _{1 is} preferably a one-valent organic group or H having a carbon number of 3 or less. R _{2 is} preferably a one-valent organic group or H having a carbon number of 3 or less. R _{3 is} preferably a one-valent organic group or H having a carbon number of 3 or less. R _{4 is} preferably a one-valent organic group or H having a carbon number of 3 or less.
Further, R ₁ is preferably a one-valent organic group having a carbon number of 3 or less or H, R ₂ is a one-valent organic group having a carbon number of 3 or less, or H, and R ₃ is a one-valent organic group having a carbon number of 3 or less. Or H, R ₄ is a one-valent organic group or H having a carbon number of 3 or less.
Examples of the organic ammonium cation include a primary ammonium cation, a secondary ammonium cation, a tertiary ammonium cation, and a quaternary ammonium cation.
As the above organic ammonium cation, a quaternary ammonium cation is preferred.
Examples of the primary ammonium cation include ethylenediamine and spermine. Further, the spermine is also a secondary ammonium cation.
Examples of the secondary ammonium cation include piperazine, piperidine and the like.
Examples of the quaternary ammonium cation include a tetramethylammonium cation, an ethyltrimethylammonium cation, and a tetraethylammonium cation.

[Chemical 1]

The organic ammonium cation is contained in the polishing slurry of the present embodiment by mixing the organic ammonium salt with another material of the polishing slurry.
Examples of the organic ammonium salt include organic ammonium hydroxide, halogen organic ammonium, and organic ammonium nitrate.

The cerium oxide abrasive grains are included in the polishing slurry of the present embodiment in the form of primary particles or secondary particles obtained by agglomerating a plurality of primary particles.
Examples of the cerium oxide abrasive grains include fumed cerium oxide abrasive grains and colloidal cerium oxide abrasive grains, and preferably fumed cerium oxide abrasive grains.

The above-mentioned base may, for example, be an inorganic alkali agent or the like as an inorganic substance.
Examples of the inorganic alkali agent include potassium hydroxide, sodium hydroxide, and ammonia.

Since the polishing slurry of the present embodiment is configured as described above, it has the following advantages.

The polishing slurry of the present embodiment contains ceria abrasive grains and an organic ammonium cation having a molecular weight of 155 or less.
This polishing slurry is a suppressor in which the change in the size of the abrasive grains is suppressed.
The reason why the polishing slurry is suppressed in the change in the size of the abrasive grains is that the organic ammonium cation is adsorbed on the SiO ^- based group existing on the surface of the cerium oxide abrasive grain, and the cerium oxide abrasive grains are sterically hindered. It is difficult for the cerium oxide abrasive grains to agglomerate each other.

Further, the polishing slurry of the present invention is not limited to the above embodiment. Moreover, the slurry for polishing of the present invention is not limited by the above-described effects. Further, the polishing slurry of the present invention can be variously modified without departing from the spirit and scope of the invention.
[Examples]

Next, the present invention will be specifically described by way of examples and comparative examples.

(Test 1: Dynamic stability)
A slurry for polishing containing 800 ppm of an organic ammonium cation and a hydroxide salt as shown in Table 1 below, 20.0% by mass of fumed cerium oxide, potassium hydroxide as an alkali, and water, and a comparative example were prepared. (pH: 11.0).

<Evaluation of Dynamic Stability>
The evaluation of the dynamic stability was carried out by applying an oscillation (dynamic load) to the polishing slurry of the examples and the comparative examples for 10 days in a oscillating machine, and confirming the growth of the abrasive grains of the polishing slurry. The conditions of the oscillation are shown below. Further, the growth rate of the abrasive grains was determined by the following formula. The diameter of the abrasive grains of the following formula was determined by a laser diffraction/scattering particle size distribution measuring apparatus (LA-920) manufactured by Horiba, Ltd.
The results are shown in Table 1 below and Figures 1 and 2.
Oscillation mode: reciprocating oscillation speed: 310 times / minute amplitude: 40 mm
Sample container capacity: 50 mL
Sample size: 20 mL
Grinding grain growth rate (%) = (the diameter of the abrasive grains after the oscillation / the diameter of the abrasive grains before the oscillation -1) × 100

[Table 1]

As shown in the above Table 1 and Figs. 1 and 2, the polishing slurry of the example and the polishing slurry of Comparative Example 1 in which the organic ammonium cation was not used, and the polishing slurry of Comparative Example 2 in which the molecular weight of the organic ammonium cation was large was large. The growth rate of the abrasive grains is small compared to the slurry.

(Test 2: Grinding rate)
A slurry containing a salt of ethyltrimethylammonium cation and hydroxide, 20.0% by mass of fumed cerium oxide, potassium hydroxide as an alkali, and water (pH: 11.0, concentration of the above salt: 200 ppm, 800 ppm, 2000 ppm).
Then, the polishing slurry described above was diluted two-fold with water immediately prior to the polishing, the polishing using diluted slurry having a SiO use of tetraethyl orthosilicate (TEOS) by plasma CVD and form ₂ of The blank wafer of the film was polished to determine the polishing rate. The polishing conditions are shown below.
Grinding machine: EPO222D (manufactured by Ebara Seisakusho Co., Ltd.)
Grinding pressure: 35 MPa
Grinding table revolutions: 60 min ^-1
Carrier revolutions: 40 min ^-1
Slurry flow rate: 150 mL/min
Grinding time: 60 min
The polishing rate was determined by dividing the thickness reduced by the polishing by the polishing time.
Further, the thickness was measured using a nanospec AFT 5100 manufactured by Nano-metrics.
The results are shown in Fig. 3.

As shown in FIG. 3, the smaller the amount of the organic ammonium cation relative to the amount of the cerium oxide abrasive particles, the higher the polishing rate.

(Test 3: Number of defects)
A slurry for polishing of Example 5 containing 500 ppm of ethyl trimethylammonium cation and hydroxide salt, 12.5% by mass of fumed cerium oxide, potassium hydroxide as an alkali, and water (pH: 11.0) was prepared. ).
Further, a polishing slurry of Comparative Example 3 produced in the same manner as the polishing slurry except that the above salt was not used was produced.
Grinding of a blank wafer having a SiO ₂ film formed by plasma CVD using tetraethoxy decane (TEOS) using a slurry for polishing (area of wafer: 706.5 cm ² , number of wafers: 20 sheet). The polishing conditions are shown below.
Grinding machine: FREX (manufactured by Ebara Manufacturing Co., Ltd.)
Grinding head: G2
Grinding pressure CAP/RAP/OAP/EAR/RRP/PCP[hPa]: 285/280/250/240/ 350/140
Polishing head / the number of revolutions of the polishing table [min ^-1]: 60/61
Slurry flow rate: 200 mL/min
Grinding time: 60 min
Then, the number of defects (pad/wafer) of the wafer is measured.
The number of defects was measured using a wafer surface inspection apparatus (model name: LS6600) manufactured by Hitachi High-Technologies Corporation.
The results are shown in Table 2 below and Figure 4 below.

[Table 2]

As shown in the above Table 2 and FIG. 4, the polishing slurry of Example 5 had a smaller number of defects than the polishing slurry of Comparative Example 3 in which no organic ammonium cation was used.

Figure 1 is a graph showing the relationship between the molecular weight of the organoammonium cation and the growth rate of the abrasive particles.

Fig. 2 is a diagram showing changes in the scale of Fig. 1.

Fig. 3 is a graph showing the relationship between the amount (parts by mass) of the organoammonium cation, the polishing rate, and the growth rate of the abrasive grains with respect to 100 parts by mass of the cerium oxide abrasive grains.

4 is a view showing the number of defects when the polishing slurry of Example 5 and Comparative Example 3 was used.

Claims (3)

A polishing slurry for polishing an interlayer insulating film and comprising: Cerium oxide abrasive grains, and An organic ammonium cation having a molecular weight of 155 or less. The slurry for polishing according to claim 1 which contains 0.1 to 1.0 part by mass of the above organic ammonium cation with respect to 100 parts by mass of the above-mentioned ceria abrasive grains. The slurry for polishing according to claim 1 or 2, which contains fumed cerium oxide abrasive grains as the above-mentioned ceria abrasive grains.