KR101134596B1 - Ceruim-based abrasive slurry - Google Patents

Abstract

A cerium-based abrasive slurry is provided that can minimize scratch generation while maintaining a high polishing rate. The cerium-based abrasive slurry is an abrasive slurry comprising water, cerium oxide powder, and a dispersant, the abrasive slurry having a volume average particle diameter of about 130 nm or more and having a filter having fine pores having an average diameter of about 800 to 1000 nm. The concentration of the macroparticles remaining in the filter of the macroparticle analyzer by using the macroparticle analyzer is about 500 ppm or less by the following formula.

(Wc is the weight of cerium oxide powder, Wf1 is the weight of the filter, Wf2 is the weight of the dried filter after filtering the slurry slurry with the filter.)

CMP, slurry, cerium, macroparticles

Description

Cerium-based abrasive slurry

1 is a cross-sectional view schematically showing a macro particle analysis apparatus capable of measuring the content of the macroparticles contained in the abrasive slurry according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10: upper vessel 20: filter

30: lower container 35: vacuum exhaust port

40: guide tube 50: abrasive slurry

100: large particle analysis device

The present invention relates to a cerium-based abrasive slurry, and more particularly, to a cerium-based abrasive slurry having a low concentration of large particles through a large particle t amount measuring device.

BACKGROUND ART A cerium-based abrasive slurry containing cerium-based particles as a main component is rapidly expanding its use due to its excellent polishing effect. The cerium-based abrasive slurry is used not only for polishing optical glass but also for polishing semiconductor glass for magnetic recording media such as liquid crystal glass and hard disk, and for semiconductor manufacturing in electronic circuits such as LSI.

In chemical mechanical polishing (CMP) of semiconductors, cerium-based abrasives are usually dispersed in slurry in water to be used after slurrying. Until now, cerium-based abrasive slurries showing a large amount of polishing (or high polishing rate) have been used. Has been the main purpose. However, in recent years, as the wiring of semiconductor processes is gradually miniaturized and the spacing between chips is reduced, the chemical mechanical polishing slurry is required to have a small number of scratches and a reduction in the size of scratches generated in addition to the polishing rate.

The cerium-based abrasive slurry used in the conventional chemical mechanical polishing is subjected to a crushing process in the manufacturing process, but the macroparticles produced during the manufacturing process are not completely filtered, which is a major cause of the scratch. Such abnormally large grown cerium-based abrasive particles, even in the presence of trace amounts, may produce micro-size scratches or defects on the surface of semiconductor wafers during chemical mechanical polishing processes, resulting in poor yields.

Also, in recent years, the reduction in line width has been promoted in semiconductor manufacturing, leading to an increase in the number of chips produced on a single wafer. In the case of using a conventional cerium-based abrasive slurry in a semiconductor process having such a reduced line width, the micro ( Micro-size scratches are also lethal, limiting yields. Moreover, since the number of chemical mechanical polishing processes is gradually applied to the semiconductor manufacturing process, the presence and size of scratches after such polishing process are closely related to the yield of chips in the wafer.

Efforts have been made to control the particle size to 3 μm or less in order to reduce such scratches. However, in the fine pattern of 0.16 μm or less, the yield is significantly reduced due to scratches. It is a large particle having a particle size of 700 nm or more, especially 800 nm or more, which causes scratches on the wafer surface, even if the cumulative 100% particle size (D ₁₀₀ ) of the abrasive slurry is measured by a particle size analyzer using an actual laser diffraction to obtain a value of about 300 to 500 nm. This is because they are not observed with the particle size analyzer. This is because the number of such large particles is relatively small compared to the number of abrasive particles close to the mean volume diameter.

If the volume average particle diameter of the abrasive slurry is reduced by the method of preparing a cerium-based abrasive slurry according to the prior art, the number of large particles of 800 nm or less can be reduced, but the slurry having a small volume average particle diameter is reduced due to a decrease in the polishing rate. The problem arises. In addition, if the volume average particle diameter of the abrasive slurry is increased in order to increase the polishing rate, the number of the large particles increases, which causes a significant drop in yield due to scratches.

The technical problem to be achieved by the present invention is to provide a cerium-based abrasive slurry that can minimize the occurrence of scratches by increasing the polishing rate by increasing the volume average particle diameter to contain a large particle below the reference value.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

The cerium-based abrasive slurry according to an embodiment of the present invention for solving the above technical problem is an abrasive slurry containing water, cerium oxide powder and a dispersant, the volume average particle diameter of the abrasive slurry is about 130nm or more, about The concentration of the macroparticles remaining in the filter of the macroparticle analyzer is about 500 ppm or less by using the macroparticle analyzer equipped with a filter having fine pores having an average diameter of 800 to 1000 nm. do.

(Wc is the weight of the cerium oxide powder, Wf1 is the weight of the filter, Wf2 is the weight of the filter dried after filtering the abrasive slurry with the filter.)

Specific details of other embodiments are included in the detailed description and the accompanying drawings.

Advantages and features of the present invention, and methods for achieving them will be apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be embodied in various different forms, and only the present embodiments make the disclosure of the present invention complete and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, with reference to the accompanying drawings will be described in detail a method for producing a cerium-based abrasive slurry according to an embodiment of the present invention, a manufacturing apparatus used for this and a cerium-based abrasive slurry produced thereby.

The cerium-based abrasive slurry according to the present invention can be obtained by adding a dispersant to a mixture of cerium oxide and water to disperse the dispersion, followed by centrifugation and optionally further filtering. Such an abrasive slurry may be used as an abrasive slurry for chemical mechanical polishing after being tested for suitability for a polishing process through a large particle analysis device.

First, the cerium oxide powder used in the cerium-based abrasive slurry according to the present invention is not particularly limited in its production method, and may be produced by a conventional method. For example, raw materials such as cerium carbonate and cerium hydroxide may be pulverized using a wet mill or a dry mill, and then fired at 650 to 900 ° C. to oxidize to prepare a fine cerium oxide powder having a size of 10 to 100 nm. . The present invention is not limited thereto, and raw materials, such as cerium carbonate and cerium hydroxide, may be calcined and oxidized at 650 to 900 ° C., and then ground using a wet mill or a dry mill to produce fine cerium oxide powder.

The cerium oxide powder thus prepared is dispersed in water to make a cerium oxide dispersion, wherein a concentration of cerium oxide for facilitating dispersion is preferably in the range of 0.5 to 20 wt%. Thereafter, the cerium oxide powder contained in the cerium oxide dispersion is divided into hundreds of nano-sized particles through an opposing collision or ultrasonic wave or a wet milling process to evenly disperse them in water.

The dispersant used in the dispersion is preferably selected in consideration of the surface potential value of cerium oxide in the cerium oxide dispersion, there is no particular limitation. Dispersion of cerium oxide is usually in the range of pH 4-8, since the surface potential value of cerium oxide has a positive value, an anionic organic compound may be preferably used as the dispersant, and specific examples thereof include polyacrylic acid , Polyvinyl sulfate, polymethacrylic acid, polyacrylamide, polyarylamine and the like. Preferably, the dispersant has a weight average molecular weight of 1,000 or more and 50,000 or less, and when the molecular weight is less than 1,000, it is difficult to secure dispersion stability of the cerium oxide slurry, and when it exceeds 50,000, the viscosity of the cerium oxide slurry is increased to ensure long-term stability. Difficult to do

In order to remove the large particles present in the dispersion with respect to the cerium oxide dispersion dispersed as described above, it is possible to remove the large particles by centrifugation using a centrifugal separator, or to use methods such as spontaneous sedimentation and cyclone. These methods are commonly used to remove large particles by using the difference in sedimentation rate according to the gravity of cerium oxide particles, and there is a difference in their efficiency or degree of classification.

In this way, the large particles are removed from the cerium oxide dispersion to form a cerium-based abrasive slurry. In order to remove the macroparticles of the cerium-based abrasive slurry according to the present invention, after passing through a centrifugal separator as described above, the macroparticles may be removed by a natural sedimentation process. In some cases, the filtering process may be further performed after the second natural precipitation process. Here, the filtering process may be circulated a predetermined number of times using a multistage filter of one or more stages, preferably three or more stages, so that the macroscopic particles may be more completely removed. In this filtering process, a polypropylene filter formed of several layers may be used.

As such, the slurry prepared by spontaneous sedimentation or spontaneous sedimentation and filtering is measured by a particle size analyzer (UPA150 ™ of Microtrac Co., Ltd.) using laser diffraction, and has a cumulative 100% particle size (D ₁₀₀ : particle size using laser diffraction). The particle size in which the cumulative distribution becomes 100% when measured by the analyzer was in the range of about 200 nm to 500 nm, and the volume average particle diameter was about 130 nm or more. Preferably, the volume average particle diameter of this slurry was at least about 180 nm.

Here, after grasping the content of the macroparticles having a particle size of 800 nm or more, the particle size does not appear in the particle size analyzer, it can be used as an abrasive slurry for chemical mechanical polishing only in the case of the abrasive slurry content is below the reference value.

The content of the macroparticles can be measured through the macroparticle analyzer shown in FIG. 1. 1 is a cross-sectional view schematically showing a macro particle analysis apparatus capable of measuring the content of the macroparticles contained in the abrasive slurry according to an embodiment of the present invention.

As shown in FIG. 1, the large particle analysis apparatus 100 is coupled to an upper container 10 for storing an abrasive slurry 50 and an upper container 10, and a vacuum exhaust hole 35 is formed on one side thereof. And a hydrophilic resin filter 20 interposed between the upper container 10 and the lower container 30 to filter the large particles of the abrasive slurry 50.

The upper container 10 may be open at the top so that the abrasive slurry 50 may be easily introduced. In addition, an opening is formed in the portion corresponding to the lower container 30 of the upper container 10 so that the abrasive slurry 50 can escape to the lower container 30.

The lower vessel 30 is coupled with the upper vessel 10 through the opening of the upper vessel 10 so that the abrasive slurry 50 flows from the upper vessel 10 to the lower vessel 30 through this place. The filter 20 is interposed between the lower container 30 and the upper container 10 to filter large particles of the abrasive slurry 50. A vacuum pump (not shown) is formed through the vacuum exhaust port 35 formed at one side of the lower container 30 to maintain the inside of the lower container 30 in a vacuum state. By the forced filtering by the vacuum pressure, the large particles having a particle size of 800 nm or more in the abrasive slurry 50 are filtered by the filter 20, and the remaining particles pass through the filter 20.

The lower container 30 may be formed with a guide tube 40 for guiding the flow path of the abrasive slurry 50 passing through the filter 20.

The filter 20 may be formed of a hydrophilic resin so that the abrasive slurry 50 may be well absorbed and filtered by the filter 20. For example, polycarbonate may be used as the filter 20. In addition, pores having an average diameter of about 800 to 1000 nm are formed in the filter 20 so that the abrasive slurry 50 having a large particle size may be filtered in the filter 20. Such pores may be formed in any uniform size using a laser, and the size of the macroparticles to be filtered may be variously adjusted according to the size of the pores.

Using such a large particle analysis device 100, the concentration of the large particles of the abrasive slurry 50 not observed by the particle size analyzer is measured using the following method.

As described above, the abrasive slurry includes cerium oxide powder, water, and a dispersant. Here, the weight (hereinafter, referred to as Wc) of the cerium oxide powder and the weight (hereinafter, referred to as Wf1) of the filter are measured. And after filtering an abrasive slurry with the macroparticle analyzer 100, the filter which passed the abrasive slurry is dried. The weight of the dried filter (Wf2) is measured.

The above measured values can be substituted in the following Equation 1 to determine the concentration of the large particles in ppm.

As such, the concentration of the macroparticles contained in the abrasive slurry may be calculated using the macroparticle analysis apparatus 100. Here, the content of the calculated macroparticles is so small that they are not observed in the particle size analyzer using laser diffraction, but the particle size is large, and the scratches generated by such macroparticles may act fatally to the polished film. Although not observed in the particle size analyzer, the macroparticle concentration having a particle size of 800 nm or more observed by the macroparticle analyzer of the present invention is preferably 500 ppm or less. If the large particle concentration is more than 500 ppm, a lot of scratches may occur.

In order to obtain an appropriate etching rate required by the process conditions, the cerium-based abrasive slurry according to an embodiment of the present invention preferably has a volume average particle size of at least 130 nm. When the volume average particle diameter is smaller than 130 nm, the concentration of the large particles is low but it is difficult to have a high polishing rate. More preferably, the cerium-based abrasive slurry according to one embodiment of the present invention has a volume average particle diameter of 180 nm or more.

In addition, the cumulative 100% particle size (D ₁₀₀ ) of the cerium-based abrasive slurry according to an embodiment of the present invention is preferably in the range of about 200 nm to 500 nm. Since the abrasive slurry generally has a Gaussian distribution, the cumulative 100% particle size (D ₁₀₀ ) is larger than about 200 nm when the volume average particle size is 130 nm or more. When the cumulative 100% particle size (D ₁₀₀ ) is larger than 500 nm, many large particles having a particle size of 800 nm or more may be generated.

As such, after testing the concentration of the macroparticles contained in the abrasive slurry of the present invention using the macroparticle analyzer shown in FIG. 1, the abrasive slurry of the present invention is chemical and mechanical only when the concentration of the macroparticles is 500 ppm or less. It can be used as an abrasive slurry for polishing.

The cerium-based abrasive slurry according to one embodiment of the present invention is not only used for polishing a semiconductor thin film for a fine pattern of 0.16 μm or less, but also an inter-layer dielectric (ILD) and a metal interlayer dielectric layer polished with a conventional silica slurry. It can also be applied to the polishing of (Inter-Metal Dielectric) and Shallow Trench Isolation (STI) processes.

More detailed information about the present invention will be described through the following specific experimental examples, and details not described herein will be omitted because it can be inferred technically by those skilled in the art.

Experimental Example 1

A silicon dioxide film was formed on the 8-inch silicon wafer with a thickness of 10,000 Å using a plasma enhanced chemical vapor deposition (PE-CVD) process of TEE (TetraEthyl OrthoSilicate), PE-TEOS process, and LP-CVD on a silicon dioxide film. A silicon nitride film was formed to a thickness of 2,000 kPa using a Low Pressure Chemical Vapor Deposition method to form a polished film.

Dry milling of cerium hydroxide using a ball mill was followed by oxidation at about 900 ° C. to obtain cerium oxide having a primary particle size of about 35 nm measured by XRD. 800 g of the obtained cerium oxide powder was added to 9160 g of deionized water, followed by stirring for 30 minutes using a propeller stirrer so that the powder lumps agglomered during preparation of the cerium oxide powder remained in water to prepare a mixed liquid. 20 g of polyacrylic acid (weight average molecular weight: 3000, concentration: 40 wt%) as a dispersant was added to the cerium oxide aqueous suspension while stirring.

Thereafter, the particles were collided at a pressure of 200 MPa using an anti-collision disperser to obtain a cerium oxide slurry having a concentration of 8 wt% uniformly dispersed in water.

This cerium oxide slurry is injected at the bottom of the cylindrical centrifuge in rotation at 1200rpm and pulled out to the top (at this time, the large particles are attached to the base wall of the centrifuge and come out to the top discharge pipe, and only small particles come out to the top of the centrifuge). ), The large particles were removed first. Thereafter, the slurry was discharged from the upper discharge pipe by using the same centrifuge in rotation at 350 rpm to remove the large particles secondarily.

Thereafter, two stages of the polypropylene filter having a size of 3 μm were rotated for 3 hours at a flow rate of 10 L / min. After measuring the wt% of the slurry passed through the polypropylene filter, distilled water was added to prepare a 5 wt% slurry.

The volume average particle size and the cumulative 100% particle size (D ₁₀₀ ) were obtained using the particle size analyzer (UPA150 ™ manufactured by Microtrac Co., Ltd.) using laser diffraction for the cerium-based abrasive slurry thus prepared. In this case, the volume average particle diameter was about 191 nm, and the cumulative 100% particle size (D ₁₀₀ ) was about 458 nm.

After dilution to 0.25 wt% by adding deionized water to the cerium-based abrasive slurry, the content of the macroparticles in the abrasive slurry was measured using the macroparticle analyzer shown in FIG. 1. Here, the filter used in the macroscopic particle analyzer used 'Membrane Filter 1.2 micrometer' ™ made of Millipore's polycarbonate having an average diameter of about 800 nm. At this time, the large particle concentration was measured to be about 369.6 ppm.

Experimental Example 2

The cerium-based abrasive slurry according to Experimental Example 2 was prepared in the same manner as in Experimental Example 1 except for the following. That is, after removing the first large particles using a centrifuge, using the same centrifuge in rotation at 200rpm to obtain a slurry discharged from the upper discharge pipe to remove the large particles. At this time, the volume average particle diameter of the cerium-based abrasive slurry was about 220 nm, the cumulative 100% particle size (D ₁₀₀ ) was about 467 nm, and the large particle concentration was about 343.2 ppm.

Comparative Example 1

The cerium-based abrasive slurry according to Comparative Example 1 was prepared in the same manner as in Experimental Example 1 except for the following. That is, the process of removing the large particles by the second centrifuge was excluded. In this case, the volume average particle diameter was about 310 nm, the cumulative 100% particle size (D ₁₀₀ ) was about 492 nm, and the large particle concentration was about 680.2 ppm.

Comparative Example 2

The cerium-based abrasive slurry according to Comparative Example 2 was prepared in the same manner as in Experimental Example 1 except for the following. That is, the dry pulverized cerium hydroxide powder was oxidized at about 700 ° C. to obtain cerium oxide having a primary particle size of about 30 nm measured by XRD. In addition, the process of removing the large particles by the second centrifuge was excluded. At this time, the volume average particle diameter was about 128 nm, the cumulative 100% particle size (D ₁₀₀ ) was about 461 nm, and the large particle concentration was about 384.5 ppm.

Comparative Example 3

The cerium-based abrasive slurry according to Comparative Example 3 was prepared in the same manner as in Experimental Example 1 except for the following. That is, the dry pulverized cerium hydroxide powder was oxidized at about 650 ° C. to obtain cerium oxide having a primary particle size of about 28 nm measured by XRD. In addition, the process of removing the large particles by the second centrifuge was excluded. At this time, the volume average particle size was about 118 nm, the cumulative 100% particle size (D ₁₀₀ ) was about 450 nm, and the large particle concentration was about 851.6 ppm.

Thus, using Experimental Example 1 and Experimental Example 2, and each of the cerium-based abrasive slurry obtained in Comparative Examples 1 to 3 and the 8-inch CMP polishing machine (Amir's Mirra ™ device), The polishing film composed of the silicon nitride film formed on the silicon dioxide film was polished for 90 seconds at a pressure of 3.5 psi. Each cerium-based abrasive slurry was supplied at a rate of 150 mL / min, the rotation speed of the top plate wafer head was 104 rpm, and the rotation speed of the bottom plate was 110 rpm. The pad used here used an 'IC1000 / suba IV stacked pad' ™ (Rodel).

After polishing the polished film with each cerium-based abrasive slurry, the polishing rate obtained by measuring the thickness of the polished film was measured, and AIT-UV ™ (KLA-Tenco Co., Ltd.), a scratch evaluation equipment, was used. The results of evaluating the number of scratches having a size of 0.16 μm or more are shown in Table 1 below.

Volume average particle diameter
(nm) D ₁₀₀
(nm) Large particle concentration
(ppm) scratch
Count Polishing Speed
(Å / min) Experimental Example 1 191 458 369.6 2 3674.1 Experimental Example 2 220 467 343.2 9 3872.8 Comparative Example 1 310 492 680.2 54 3754.3 Comparative Example 2 128 461 384.5 5 2670.2 Comparative Example 3 118 450 851.6 37 2178.6

Looking at Table 1, the slurry of Comparative Example 1 obtained a high polishing rate with a volume average particle diameter of 130 nm or more, preferably 180 nm or more, but a large particle concentration of 500 ppm or more generated a large amount of scratches. In the slurry of Comparative Example 2, a large particle concentration was 500 ppm or less, but less scratch occurred, but a high polishing rate was not obtained with a volume average particle size of 130 nm or less. The slurry of Comparative Example 3 was not only low in polishing rate with a volume average particle diameter of 130 nm or less, but also a large amount of scratches were generated at a large particle concentration of 500 ppm or more.

On the other hand, the slurry of Experimental Example 1 and Experimental Example 2 obtained a high polishing rate with a volume average particle diameter of 130 nm or more, and generated small scratches with a large particle size t of 500 nm or less.

As can be seen from Table 1, the cumulative 100% particle size (D ₁₀₀ ) of each of the slurry according to Experimental Example 1 and Experimental Example 2 and Comparative Examples 1 to 3 were all measured to be 500 nm or less, but the large particles of 800 nm or more were It can be seen that it cannot be measured through the analyzer. This is because, as mentioned above, the content of the large particles is very small.

As can be seen from the above experiments and comparative examples, in the case of the cerium-based abrasive slurry having a volume average particle diameter of about 130 nm or more and a concentration of the large particles having a particle size of about 800 nm or more through the macro particle analyzer of about 500 ppm or less, high etching Not only can the speed be obtained, but the scratches caused by the large particles can be reduced.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above embodiments but may be manufactured in various forms, and having ordinary skill in the art to which the present invention pertains. It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

As described above, according to the cerium-based abrasive slurry according to the present invention, it is possible to realize a high etching rate and at the same time to prevent scratches.

Claims (9)

An abrasive slurry comprising water, cerium oxide powder, and a dispersant, The volume average particle diameter of the abrasive slurry is 130 nm or more, A cerium-based abrasive material having a concentration of macroparticles remaining in the filter of the macroparticle analyzer by 500 ppm or less by using the following formula using a macroparticle analyzer including a filter having micropores having an average diameter of 800 to 1000 nm. Slurry.

(Wc is the weight of the cerium oxide powder, Wf1 is the weight of the filter, Wf2 is the weight of the filter dried after filtering the abrasive slurry with the filter.) The method according to claim 1, A cerium-based abrasive slurry having a cumulative 100% particle size (D ₁₀₀ ) of the cerium-based abrasive slurry of 200 to 500 nm. The method according to claim 1, A cerium-based abrasive slurry having a particle size of 800 nm or more of the macroparticles remaining in the filter. The method according to claim 1, Cerium-based abrasive slurry of the filter of the macroparticle analyzer is made of a hydrophilic resin filter. 5. The method of claim 4, The filter is a cerium-based abrasive slurry made of polycarbonate. The method according to claim 1, The cerium oxide powder is a cerium-based abrasive slurry is a powder of cerium carbonate or oxide of cerium hydroxide. The method according to claim 1, The dispersant is a cerium-based abrasive slurry made of an anionic organic compound. 8. The method of claim 7, The dispersant is a cerium-based abrasive slurry made of at least one material selected from the group consisting of polyacrylic acid, polyvinyl sulfate, polymethacrylic acid, polyacrylamide and polyarylamine. The method according to claim 1, A cerium-based abrasive slurry having a weight average molecular weight of the dispersant of 1,000 or more and 50,000 or less.

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