JP2008235491A - Abrasive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive composition for final polishing which ensures the dispersion stability of abrasive grains even after dilution, and does not cause clogging at filtration via a filter. <P>SOLUTION: The abrasive composition contains abrasive grains, a water-soluble polymer compound, one or two or more types of positive ion surfactants, and a basic monomer composition. Particularly, the abrasive composition contains a water-soluble polysaccharide, such as hydroxyethyl cellulose, as the water-soluble polymer compound, a fourth-class ammonium compound as the positive ion surfactant, and a nitride-element-containing basic compound as the basic monomer composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polishing composition used for CMP polishing treatment.

  Polishing of a silicon wafer by CMP realizes high-precision flattening by performing multi-stage polishing of three stages or four stages. The primary polishing and secondary polishing performed in the first stage and the second stage mainly aim at surface smoothing and require a high polishing rate.

  The final polishing performed in the third stage or the final stage of the fourth stage is mainly intended to suppress haze (surface haze). Specifically, the processing pressure is lowered to suppress haze, and the slurry composition is changed from the composition used for the primary polishing and the secondary polishing to make the surface hydrophilic simultaneously with the polishing.

  Patent Document 1 describes a conventional slurry that suppresses haze on a wafer surface in final polishing. The polishing composition described in Patent Document 1 contains a cellulose derivative or polyvinyl alcohol, which is a water-soluble polymer compound, and is coated with a water-soluble polymer compound during polishing to make the wafer surface hydrophilic. As the cellulose derivative, hydroxyethyl cellulose is particularly preferable, and its molecular weight and concentration are optimized.

  In the primary polishing and the secondary polishing in the multi-stage polishing, a filter (filtration accuracy: 5 μm to 30 μm) is installed in the polishing composition supply device or the polishing device to remove coarse particles and aggregated particles that cause scratches. It is common to remove. However, in the case of the polishing composition used in the final stage, no filter is installed in the supply device and the polishing device.

  A water-soluble polymer is added to the polishing composition used in the final stage for the above-mentioned purpose, and when used for polishing, it is often diluted 20 to 50 times. The reason why the filter is not installed in the final stage is that the filter is clogged in a short time by installing the filter. This clogging is different from the normal mechanism in which coarse particles contained in the polishing composition cause clogging. In the case of water-soluble polymers, particularly cellulose polymers, the dispersion stability of the abrasive grains after dilution is reduced. This is due to the decline.

  It should be noted that even if the components of the polishing composition are individually passed through the filter, the filter is not clogged, and each component is not adsorbed on the filter media (made of polypropylene) and clogged. I know that.

  While the abrasive grains in the polishing composition as a stock solution are stably in a monodispersed state, after dilution, the surface state (electric double layer) of the abrasive grains changes, and the abrasive grain surface becomes cellulose-based. It is thought that this is because the polymer is easy to cover and the abrasive grains tend to aggregate. That is, it is considered that when the abrasive grains that have become unstable due to dilution pass through the filter, the aggregation of the water-soluble polymer and the abrasive grains further proceeds, and the filter is clogged in a short time. . Such clogging also occurs in a precision filter having a filtration accuracy of 1 μm and a filter having a relatively coarse filter for semiconductors such as 90 μm.

JP 2001-3036 A

  An object of the present invention is to provide a polishing composition for final polishing which ensures the dispersion stability of abrasive grains even after dilution and does not clog even when passed through a filter.

  The present invention is an abrasive composition comprising abrasive grains, a water-soluble polymer compound, one or more cationic surfactants, and a basic monomer compound.

  In the present invention, the water-soluble polymer compound is a water-soluble polysaccharide or polyvinyl alcohol.

  In the present invention, the water-soluble polysaccharide is hydroxymethyl cellulose or hydroxyethyl cellulose, and has an average weight molecular weight of less than 1,500,000.

  In the invention, it is preferable that the cationic surfactant contains at least a quaternary ammonium compound.

  Moreover, this invention is characterized by the weight ratio of the said abrasive grain, the said quaternary ammonium compound, and an abrasive grain being 1-1500.

  In the invention, it is preferable that the basic monomer compound is an alkali metal hydroxide, an alkali metal or alkaline earth metal carbonate compound, or a basic compound having a nitrogen element.

  In the present invention, the basic compound having a nitrogen element is one or more selected from ammonia, a primary amine compound, a secondary amine compound, and a tertiary amine compound. .

  According to this invention, it is characterized by including an abrasive grain, a water-soluble polymer compound, 1 type, or 2 or more types of cationic surfactant, and a basic monomer compound.

  Thereby, the dispersion stability of the abrasive grains is ensured even after dilution, and a polishing composition for final polishing that does not clog even when passed through a filter can be realized.

  According to the invention, the water-soluble polymer compound may be a water-soluble polysaccharide or polyvinyl alcohol.

  According to the invention, it is preferable to use hydroxymethyl cellulose or hydroxyethyl cellulose as the water-soluble polysaccharide, and it is preferable that the average weight molecular weight is less than 1,500,000.

  According to the invention, the cationic surfactant preferably contains at least a quaternary ammonium compound, and the weight ratio of the abrasive grains to the quaternary ammonium compound abrasive grains is 1 ˜1500 is preferred.

  According to the invention, the basic monomer compound may be an alkali metal hydroxide, an alkali metal or alkaline earth metal carbonate compound, or a basic compound having a nitrogen element.

  According to the present invention, the basic compound having nitrogen element may be one or more selected from ammonia and primary amine compounds, secondary amine compounds, and tertiary amine compounds. preferable.

  The composition for semiconductor polishing of this invention is an abrasive | polishing agent composition characterized by including an abrasive grain, a water-soluble polymer compound, 1 type, or 2 or more types of cationic surfactant, and a basic monomer compound.

  The water-soluble polymer compound is a water-soluble polysaccharide or polyvinyl alcohol, and a water-soluble polysaccharide is preferable.

  As the water-soluble polysaccharide, nonionic hydroxymethyl cellulose and hydroxyethyl cellulose (HEC) are preferable. The average weight molecular weight of the water-soluble polysaccharide is preferably less than 1,500,000, more preferably 500,000 to 800,000.

  When the molecular weight of the water-soluble polysaccharide is too small, sufficient hydrophilicity cannot be exhibited, and when the molecular weight is too large, the abrasive grains are aggregated.

  The content of the water-soluble polymer compound in the polishing composition of the present invention is 0.005 to 0.02% by weight of the total amount of the polishing composition.

  The cationic surfactant preferably contains at least a quaternary ammonium compound. The quaternary ammonium compound is preferably a tetramethylammonium salt, a tetraethylammonium salt or a tetrabutylammonium salt, more preferably a hydroxide thereof, particularly TMAH (tetramethylammonium hydroxide).

  The content of the cationic surfactant in the polishing composition of the present invention is 0.001 to 0.01% by weight of the total amount of the polishing composition.

  The weight ratio of the abrasive grains to the quaternary ammonium compound (abrasive grain weight / quaternary ammonium compound weight) is 1-1500, preferably 50-200.

  The basic monomer compound is an alkali metal hydroxide, an alkali metal and alkaline earth metal carbonate compound, or a basic compound having a nitrogen element, and is preferably a basic compound having a nitrogen element.

  As a basic compound which has a nitrogen element, it is 1 type, or 2 or more types chosen from ammonia and a primary amine compound, a secondary amine compound, and a tertiary amine compound, Preferably it is ammonia.

  The concentration of the basic monomer compound varies depending on the degree of dissociation of the compound used in an aqueous solution, but the preferred pH range for the polishing composition is 9.5 to 11.0, more preferably 10 0.0-10.5. When one kind of basic monomer compound is used and ammonia is used, the concentration is suitably 0.01 wt% to 0.05 wt%.

  As the abrasive grains, those commonly used in this field can be used. For example, fumed silica and colloidal silica, ceria, alumina, etc., which are silica-based abrasive grains, are preferable. More preferred is colloidal silica. An abrasive grain may be used independently and may mix and use multiple types of abrasive grains.

  Moreover, the density | concentration of an abrasive grain is 0.1-5.0 weight% as a density | concentration at the time of using for grinding | polishing, Preferably it is 0.1-1.0 weight%.

  In order to make the abrasive surface potential (electric double layer) stronger and more stable with the diluted polishing composition, positive potential ions covering the outside of the silanol group (negative potential) on the abrasive surface is necessary.

  In the conventional polishing composition, since ammonium ions cover the surface of the abrasive grains as cationic ions, it is conceivable to increase the concentration of ammonia in order to make the electric double layer stronger and more stable. However, if the ammonia concentration is increased too much, the wafer surface may be adversely affected. That is, LPD (light point defects) due to abrasive grains deteriorates due to deterioration of the haze level and insufficient hydrophilicization of the wafer surface after polishing.

  Therefore, in the present invention, by using ammonia and a cationic surfactant, it is possible to improve the dispersion stability of the abrasive grains and to make the surface hydrophilic.

Furthermore, the polishing composition of the present invention does not cause clogging when passing through a polypropylene filter.
The polishing composition of the present invention is produced, for example, by the following steps.

(1) Preparation of alkaline aqueous solution A water-soluble polymer compound, a cationic surfactant and a basic monomer compound are added to obtain an alkaline aqueous solution.

(2) Mixing The abrasive dispersion and the alkaline aqueous solution are mixed to obtain the polishing composition of the present invention.

Hereinafter, examples and comparative examples of the present invention will be described.
Examples and Comparative Examples of the present invention were prepared with the following compositions, respectively. In addition, the composition shown below is a diluted composition and the remainder is pure water.

(Example 1)
Abrasive grains: 0.45% by weight of silica particles
Basic monomer: Ammonia 0.025% by weight
Water-soluble polysaccharide: HEC (molecular weight 800,000) 0.012% by weight
Cationic surfactant: TMAH 0.003% by weight

(Example 2)
Abrasive grains: 0.45% by weight of silica particles
Basic monomer: Ammonia 0.025% by weight
Water-soluble polysaccharide: HEC (molecular weight 800,000) 0.012% by weight
Cationic surfactant: TMAH 0.006% by weight

(Comparative Example 1)
Abrasive grains: 0.45% by weight of silica particles
Basic monomer: Ammonia 0.025% by weight
Water-soluble polysaccharide: HEC (molecular weight 800,000) 0.012% by weight

(Comparative Example 2)
Abrasive grains: 0.45% by weight of silica particles
Basic monomer: Ammonia 0.038% by weight
Water-soluble polysaccharide: HEC (molecular weight 800,000) 0.012% by weight

(Comparative Example 3)
Abrasive grains: 0.45% by weight of silica particles
Basic monomer: Ammonia 0.050% by weight
Water-soluble polysaccharide: HEC (molecular weight 800,000) 0.012% by weight

  In Examples 1 and 2, ammonia was used as a basic monomer, hydroxyethyl cellulose was used as a water-soluble polysaccharide, and TMAH (tetramethylammonium hydroxide) was used as a cationic surfactant. The TMAH concentration is 0.003% by weight in Example 1 and 0.006% by weight in Example 2.

  The weight ratio of the abrasive grains of Example 1 to TMAH is 0.45 / 0.003 = 150, and the weight ratio of the abrasive grains of Example 2 to TMAH is 0.45 / 0.06 = 75. is there.

  Comparative Examples 1 to 3 differ from Examples 1 and 2 only in that they do not contain TMAH, which is a cationic surfactant. The concentration of the basic monomer is 0.025% by weight in Comparative Example 1, 0.038% by weight in Comparative Example 2, and 0.050% by weight in Comparative Example 3.

[Zeta potential]
The zeta potentials of Examples 1 and 2 and Comparative Examples 1 to 3 were measured. The zeta potential was measured using a zeta potential measuring device (DT-1200, manufactured by Dispersion Technology).

FIG. 1 is a graph showing the measurement results of zeta potential.
As can be seen from the graph, the zeta potentials of Comparative Examples 2 and 3 were larger in absolute value than Comparative Example 1, and Examples 1 and 2 were larger. The value of the zeta potential represents the surface potential with respect to the diluted particles. From these results, Comparative Examples 2 and 3 are superior in dispersion stability of abrasive grains compared to Comparative Example 1. Examples 1 and 2 were found to be further superior.

  In Comparative Examples 2 and 3, the dispersion stability is improved because the content of ammonia is larger than that in Comparative Example 1, and since Examples 1 and 2 contain TMAH, the dispersion stability is further increased. It is thought that it is improving.

[Filter transmission test]
Using Examples 1 and 2 and Comparative Examples 1 to 3, the filter was permeated under the following conditions, and clogging was confirmed.
Filter: Nippon Pole Profile II (1 inch), filter size 90 μm
Polishing composition usage: 20 liters Circulation rate: 6 kilograms per minute (circulation rate at the start of the test without clogging)

  Whether the filter was clogged was determined by monitoring the differential pressure of the filter and determining that clogging occurred when the maximum differential pressure exceeded 0.4 MPa. The results are shown in Table 1. ○ indicates that no clogging has occurred, and x indicates that clogging has occurred.

  Furthermore, in the above test, the dry weights of Examples and Comparative Examples were measured before and after filter permeation, and the change in the solid content before and after filter permeation was confirmed.

  Regarding the dry weight, the polishing composition was dried at 115 ° C. before and after permeation of the filter, and the weight of the remaining solid content was measured. The results are shown in Table 2. In addition, the weight after permeation | transmission of a filter is shown by a relative value by setting the weight before permeation | transmission of a filter to 1.

  In Comparative Example 1, the dry weight after passing through the filter decreased compared with that before passing through the filter, and when combined with the result of the filter permeation test, solid content including abrasive grains was collected in the filter and clogging occurred. I understand that.

  In Examples 1 and 2 and Comparative Examples 2 and 3, since the solid content did not change before and after filter permeation, it was confirmed that no clogging occurred.

[Polishing test]
A polishing test was conducted under the following conditions using Examples 1 and 2 and Comparative Examples 1 to 3, and the polishing rate, haze value, and LPD were evaluated.
Polishing substrate: 8-inch silicon wafer Polishing device: Strasbaugh 20 "single wafer type Polishing pad: Whitex100 (manufactured by Nitta Haas Co.)
Polishing surface plate rotation speed: 115 rpm
Carrier rotation speed: 100rpm
Polishing load surface pressure: 100 hPa
Flow rate of semiconductor polishing composition: 300 ml / min
Polishing time: 5 minutes

  The polishing rate is represented by the thickness (μm / min) of the wafer removed by polishing per unit time. The thickness of the wafer removed by polishing was calculated by measuring the reduction in wafer weight and dividing by the area of the polished surface of the wafer. The results are shown in FIG.

  The polishing rate indicates a relative polishing rate when the polishing rate of Comparative Example 1 is 1.0.

  The haze value and LPD were measured using a wafer surface inspection apparatus (LS6600, manufactured by Hitachi Electronics Engineering Co., Ltd.). LPD was measured for particles having a particle size of 0.1 μm or more. The result of haze value is shown in FIG. 3, and the result of LPD is shown in FIG.

  The haze value and LPD are also shown as relative values when the comparative example 1 is 1.0, similarly to the polishing rate.

  In Examples 1 and 2, a decrease in the polishing rate has occurred, but compared with LPD and haze level, it is acceptable as a substantial polishing characteristic, and an improvement in haze level has been confirmed, which is more effective. It was a result.

  The haze value of Comparative Example 2 was almost the same as that of Comparative Example 1, Comparative Example 3 was lower than Comparative Example 1, and Examples 1 and 2 were greatly improved. Further, regarding LPD, both Comparative Examples 2 and 3 were lower than Comparative Example 1, and Examples 1 and 2 were improved over Comparative Example 1.

  In Comparative Examples 2 and 3, since the ammonia concentration is too high, the adhesive force of the water-soluble polymer film covering the wafer surface is weak, and it is considered that the hydrophilicity of the wafer surface is lowered. In addition, it is considered that the etching action by ammonia caused an adverse effect on the wafer surface.

  In addition, about Example 1, 2, although the grinding | polishing characteristic before and behind filter permeation | transmission was confirmed, a change was not seen before and behind permeation | transmission, but it turned out that it is the same characteristic.

[Comprehensive evaluation]
The polishing rate, haze value, and LPD were evaluated according to the following criteria, and comprehensive evaluation was performed including the results of the filter transmission test described above. The results are shown in Table 3.

(Polishing rate)
○ Relative value exceeds 0.9 × Relative value is 0.9 or less (Haze value)
○ Relative value is 1.0 or less × Relative value exceeds 1.0 (LPD)
○ Relative value is 1.0 or less × Relative value exceeds 1.0 (overall evaluation)
○ All evaluations are ○
× 1 or more evaluations

  In Comparative Example 1, there is no problem with the polishing rate, haze value, and LPD, but there is a problem as a comprehensive evaluation because clogging of the filter occurs. Moreover, although the filter clogging does not generate | occur | produce in Comparative Examples 2 and 3, since polishing rate, a haze value, and LPD are inferior, there exists a problem as comprehensive evaluation.

  In Examples 1 and 2, the filter was not clogged, and it was found that the polishing rate, haze value, and LPD were excellent in all polishing property evaluations.

It is a graph which shows the measurement result of zeta potential. It is a graph which shows the polishing rate when an Example and a comparative example are used. It is a graph which shows a haze value when an Example and a comparative example are used. It is a graph which shows LPD when an Example and a comparative example are used.

Claims (7)

  An abrasive composition comprising abrasive grains, a water-soluble polymer compound, one or more cationic surfactants, and a basic monomer compound.   The polishing composition according to claim 1, wherein the water-soluble polymer compound is a water-soluble polysaccharide or polyvinyl alcohol.   The polishing composition according to claim 2, wherein the water-soluble polysaccharide is hydroxymethyl cellulose or hydroxyethyl cellulose, and has an average weight molecular weight of less than 1,500,000.   The polishing composition according to claim 1, wherein the cationic surfactant contains at least a quaternary ammonium compound.   The polishing composition according to claim 4, wherein a weight ratio of the abrasive grains, the quaternary ammonium compound, and the abrasive grains is 1-1500.   2. The polishing composition according to claim 1, wherein the basic monomer compound is an alkali metal hydroxide, an alkali metal and alkaline earth metal carbonate compound, or a basic compound having a nitrogen element.   7. The basic compound having a nitrogen element is one or more selected from ammonia, a primary amine compound, a secondary amine compound, and a tertiary amine compound. Polishing composition.

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