KR101117525B1 - Cerium oxide abrasive grain and manufacturing method of the same - Google Patents

Abstract

Disclosed are a cerium oxide abrasive particle having reduced fine scratches in a chemical mechanical polishing (CMP) process for forming a semiconductor multilayer structure, and a method of manufacturing the same using a hydrothermal reaction. The manufacturing method comprises a mixing step of mixing the cerium oxide abrasive particles and water; Milling process of grinding the cerium oxide abrasive particles in the mixed solution; Hydrothermal reaction for dissolving the sharp particle surface of the pulverized cerium oxide abrasive particles by adding a mineralizer; And a washing step of removing the remaining mineralizer after the hydrothermal reaction using a washing agent. The present invention also provides a chemical mechanical polishing slurry composition comprising cerium oxide abrasive particles, abrasive particle dispersant, pH adjuster and water prepared using the hydrothermal reaction.

Chemical Mechanical Polishing, STI Process, Polishing Slurry, Hydrothermal Reaction, Fine Scratch, Cerium Oxide

Description

Cerium oxide abrasive grain and manufacturing method of the same

1 is a manufacturing process of the cerium oxide abrasive particles according to the present invention.

Figure 2 is a photograph of ordinary cerium oxide abrasive particles measured by transmission electron microscope.

Figure 3 is a photograph of the cerium oxide abrasive particles subjected to hydrothermal reaction in accordance with an embodiment of the present invention by transmission electron microscope.

4 is an X-ray diffraction analysis (XRD) graph of cerium oxide abrasive particles according to an embodiment of the present invention.

The present invention relates to a cerium oxide abrasive particle and a method for manufacturing the same, and more particularly, to a cerium oxide abrasive particle capable of reducing fine scratches in a chemical mechanical polishing (CMP) process for forming a semiconductor multilayer structure. It relates to a method for producing cerium oxide abrasive particles using the hydrothermal reaction.

     Recently, as the degree of integration of semiconductor devices increases, a wide area flattening process is required to secure a margin for a high-performance exposure process. Chemical mechanical polishing is a process used for wide-area flattening of such semiconductor devices, and has the advantages of superior planarization capability and simple process compared to other planarization methods. The polishing slurry used in the chemical mechanical polishing process generally includes abrasive particles, deionized water, and additives. Colloidal silica particles or fumed silica particles are mainly used as the abrasive particles. It is not high enough, and the polishing selectivity of the oxide film and the nitride film is low, and there is a problem in that various steps of the process must be further performed.

In order to supplement the above problem, the use of a slurry containing cerium oxide particles used in the existing glass processing process is contemplated. Cerium oxide particles have the advantage of high polishing rate and high polishing selectivity of oxide film and nitride film, but specific gravity is 6 ~ 8 times higher than silica particles, which makes dispersion stability less during slurry production. There is a problem that a fine scratch occurs. Particularly, during the chemical mechanical polishing process, the trench is thin and fine in the shallow trench isolation (STI) process, so that the fine scratches have serious consequences in terms of the performance and production yield of the semiconductor device. Therefore, the polishing slurry particles used in the chemical mechanical polishing process during the semiconductor process should have a high polishing rate and no micro scratches during the polishing process.

Methods for producing metal oxide fine particles such as cerium oxide particles are classified into a gas phase method, a solid phase method, and a liquid phase method according to the prepared phase. The gas phase method has a manufacturing method such as vaporization method, pyrolysis method, flame combustion decomposition method, etc., but there are disadvantages in that it consumes a lot of manufacturing energy, is expensive in equipment, and in which manufacturing productivity is low. In addition, there are disadvantages in that the solid phase method includes a calcination method and a mechanical chemical synthesis method, but requires a reaction for a long time at a high temperature, and a process for reducing the size of particles by performing milling and fixing after the reaction. In addition, the particles that have been refined by the milling process has a disadvantage in that the edges of the particles are sharpened due to their crystallinity, causing fine scratches in the chemical mechanical polishing process. In addition, the liquid phase method includes a sol-gel method and a precipitation method, but these methods have a disadvantage in that a material cost is high and excessive waste solution is generated after the process. Therefore, the production of cerium oxide particles suitable for a chemical mechanical polishing process having a high polishing rate and at the same time preventing the occurrence of microscratches cannot be expected by using the above-described method for producing metal oxide fine particles such as cerium oxide.

Accordingly, an object of the present invention is to provide a cerium oxide abrasive particle having a high polishing rate during the chemical mechanical polishing process and capable of reducing fine scratches.

Another object of the present invention is to provide a method for producing cerium oxide abrasive particles using hydrothermal reaction.

Still another object of the present invention is to provide a chemical mechanical polishing slurry composition comprising cerium oxide abrasive particles prepared through the hydrothermal reaction.

In order to achieve the above object, the present invention is a mixing process of mixing cerium oxide abrasive particles and water; Milling process of grinding the cerium oxide abrasive particles in the mixed solution; And hydrothermal reaction of the pulverized cerium oxide abrasive particles in the presence of a mineralizer. The present invention also provides a chemical mechanical polishing slurry composition comprising a cerium oxide abrasive grain prepared for chemical mechanical polishing according to the preparation method and a cerium oxide abrasive grain prepared according to the preparation method, an abrasive grain dispersant, a pH adjuster and water. to provide.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a manufacturing process diagram of the cerium oxide abrasive particles according to the present invention, as shown in Figure 1, in order to manufacture the cerium oxide abrasive particles according to the present invention, first, a mixing process of mixing the cerium oxide abrasive particles and water Is carried out. The cerium oxide abrasive particles used in the mixing process is to perform mechanical polishing of the oxide film and / or nitride film, it can be used cerium oxide particles commonly used. The purity of the cerium oxide abrasive grains is preferably at least 99.0% by weight, more preferably at least 99.9% by weight. If the purity is less than 99.0% by weight, even after the semiconductor device cleaning process after polishing, impurities remain, which adversely affects the characteristics of the semiconductor device. As a result, defects may increase, leading to a decrease in production yield.

The water mixed with the cerium oxide abrasive particles is used to smoothly perform the milling process of the cerium oxide abrasive particles, and may be water that is commonly used. It is preferable to use deionized water or ultrapure water from which all dissolved ions are removed. . The amount of cerium oxide abrasive grains used in the mixing step is 1.0 to 50.0 parts by weight based on 100 parts by weight of water. If the amount of the cerium oxide abrasive particles used is too small or too large, there is a concern that the subsequent milling process may not be performed smoothly.

When the cerium oxide abrasive particles and water are uniformly mixed, a milling process of grinding the cerium oxide particles in the mixed solution is performed. The milling process is a process of subdividing the cerium oxide secondary particles, which are relatively weakly aggregated in an agglomerate state, into desired particle diameters. Types of milling processes include bead milling, ultrasonic milling, jet milling, and the like. The bead milling has a high degree of contamination by the beads and reaction vessels used to grind the abrasive particles evenly in the dispersion, and the finely divided particles. The milling efficiency and productivity are deteriorated, such as dispersion degree, and the ultrasonic milling process is difficult to achieve ultrafine granulation to a desired degree, and the tendency of the milled secondary particles to re-aggregate is strong so that the stability is lowered and metal impurities are generated in the ultrasonic processing apparatus. There is a problem that the risk is large. In contrast, the jet milling process used in the present invention is a milling process in which the abrasive grains in the abrasive grain dispersion are collided with each other so as to break the abrasive grains. There is an advantage that the productivity is excellent. The jet milling process may be performed using a variety of jet milling equipment, such as a commercially available brand name Nanomizer, Microfluidizer, Ultimateizer, etc., and face collision of the initial mixed solution of abrasive particles The pressure is preferably 500 to 3000 kgf / cm ² , more preferably 700 to 3000 kgf / cm ² , and even more preferably 1000 to 3000 kgf / cm ² . If the impact pressure is 500kgf / cm ^{2 It} is difficult to crush the particles, if the exceeding 3000kgf / cm ² The size of the particles to be crushed is too small, there is a disadvantage that the life of the equipment is shortened.

The cerium oxide particles adjusted to the desired particle size by the milling method have sharp particle surfaces, which cause fine scratches during the chemical mechanical polishing process. In the present invention, to reduce the fine scratches, hydrothermal reaction is performed to dissolve the sharp particle surface of the milled particles. Conventional hydrothermal reaction is a method of synthesizing an inorganic oxide under conditions of high temperature and high pressure, but in the present invention, the hydrothermal reaction is controlled to introduce a step of dissolving the sharp surface of the cerium oxide particles. 60-250 degreeC is preferable and, as for the reaction temperature of the hydrothermal reaction performed by this invention, it is more preferable if it is 80-220 degreeC. If the reaction temperature is less than 60 ℃ do not dissolve the sharp surface of the cerium oxide particles, if it exceeds 250 ℃ there is a disadvantage that the durability of the reaction vessel is poor. The reaction time is preferably 10 minutes to 48 hours, more preferably 0.5 to 24 hours. If the reaction time is less than 10 minutes, the sharp surface of the cerium oxide particles may not be dissolved, and if the reaction time exceeds 48 hours, the cerium oxide particles may grow crystals, resulting in large particle size and aggregation.

The hydrothermal reaction is carried out in the presence of a mineralizer, which creates conditions under which the insoluble compounds have minimal solubility, and moves freely in solution to promote hydrothermal reaction on the surface of the solid compound. . That is, in the general hydrothermal reaction method, the mineralizer increases the supersaturation of the solution and helps the hydrothermal reaction to occur easily. As the mineralizer, conventionally known inorganic acids may be used without limitation, and preferably phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid and mixtures thereof may be used. The content of the mineralizer is an amount sufficient to dissolve the sharp surface of the cerium oxide abrasive particles, and may vary depending on the type and concentration of the inorganic acid and its mixture, but preferably 0.1 to 50% by weight of the total hydrothermal reaction solution. It is more preferable if it is 1.0-30 weight%. If the content of the mineralizer is less than 0.1% by weight, the reaction with the cerium oxide particles does not occur sufficiently, so that dissolution of the sharp particle surface is weak. If the content of the mineralizer exceeds 50% by weight, the surface zeta charge of the cerium oxide abrasive particles is changed after hydrothermal reaction. Agglomeration occurs and there is a problem of deteriorating chemical mechanical polishing properties.

In addition, the content of the cerium oxide particles added to the hydrothermal reaction is preferably 0.1 to 50% by weight of the total solution, more preferably 1.0 to 30% by weight. If the content of the cerium oxide particles is less than 0.1% by weight of the production efficiency is lowered, if the content of more than 50% by weight has a disadvantage that the dissolution efficiency of the cerium oxide particles. The remaining components of the hydrothermal reaction solution is water.

After performing the hydrothermal reaction as described above, a process of washing the cerium oxide abrasive particles subjected to the hydrothermal reaction with a washing agent and a drying process of drying the washed cerium oxide abrasive particles in a dry oven may be further performed as necessary. . The washing step is for removing the inorganic acid remaining on the surface of the cerium oxide particles after the hydrothermal reaction. If the washing process is not performed properly, the mineral acid, which is a mineralizer of hydrothermal reaction, remains on the cerium oxide particle surface, thereby reducing the dispersibility of the particles during slurry production and preventing the implementation of the polishing selectivity by the additives used. The cleaning agent used in the washing process may be used conventionally known weak base without limitation, preferably may be used a weak base such as ammonia, potassium hydroxide, tetramethylammonium hydroxide (TMAH). The washing process is carried out at least once, preferably 3 to 10 times. When the washing step is performed, the drying step of drying the cerium oxide abrasive particles in a dry oven may be further performed. The temperature of the dry oven is preferably 90 to 120 ℃, the drying time is preferably 8 to 48 hours. Of course, the cerium oxide abrasive particles may also be used to prepare the slurry immediately after the washing process, and in addition to the weak base, a process of washing with deionized water may be added.

The present invention provides cerium oxide abrasive particles for chemical mechanical polishing prepared according to the above production method using hydrothermal reaction. 3 is a photograph of the cerium oxide abrasive particles subjected to hydrothermal reaction according to the present invention measured by transmission electron microscope. The cerium oxide abrasive particles have a characteristic that the sharp particle surface is dissolved and blunted as compared with the conventional cerium oxide abrasive particles of FIG. 2. Therefore, it is possible to reduce the fine scratches in the chemical mechanical polishing (CMP) process. The average size of the cerium oxide particles is preferably 5 to 700 nm, more preferably 10 to 500 nm. If the particle size is less than 5 nm, the polishing rate may be lowered during the chemical mechanical polishing process and adsorbed onto the wafer surface during the chemical mechanical polishing process, making it difficult to clean the wafer after polishing. In addition, when the particle size exceeds 700nm, there is a fear that fine scratches on the polishing surface.

The chemical mechanical polishing slurry composition according to the present invention comprises cerium oxide abrasive particles, abrasive particle dispersant, pH adjuster and water prepared according to the above production method using hydrothermal reaction.

The content of the cerium oxide abrasive particles may vary depending on process conditions such as pressure and speed of the polishing process, but is preferably 0.05 to 50% by weight based on the total slurry composition, and more preferably 0.1 to 30% by weight. If the content of the cerium oxide abrasive particles is less than 0.05% by weight, the polishing rate of the oxide film is lowered. If the content of the cerium oxide abrasive particles is more than 50% by weight, the initial dispersibility may be lowered.

The abrasive grain dispersant serves to improve the dispersibility of the cerium oxide abrasive grains in the slurry by coating the abrasive grains, and may be used a conventional dispersant such as carboxylic acid or salt thereof, and preferably polycarboxyl. Acids or salts thereof can be used. Specific examples of the carboxylic acid include glutaric acid, gluconic acid, glycolic acid, lauric acid, lactic acid, malic acid, malonic acid, valeric acid, citric acid, stearic acid, succinic acid, acetic acid, oxalic acid, adipic acid, capric acid , Caproic acid, caprylic acid, formic acid, fumaric acid, phthalic acid, propionic acid, pyruvic acid, tartaric acid, polyacrylic acid, salts thereof, and mixtures thereof. As the salt of the carboxylic acid, conventional carboxylic acid salts such as sodium salt, ammonium salt, and potassium salt may be used. The said carboxylic acid or its salt can be used individually or in combination of 2 or more types, It is preferable that the usage-amount is 0.01-20 weight% with respect to the whole slurry composition, More preferably, it is 0.05-10 weight%. If the amount of the carboxylic acid or its salt is less than 0.01% by weight, the polishing selectivity of the oxide film and the nitride film is reduced, and if it exceeds 20% by weight, the polishing rate may be lowered.

The pH of the polishing slurry according to the present invention can be adjusted using a pH adjuster such as conventional acids, bases, specifically, phosphoric acid, hydrochloric acid, sulfuric acid, nitric acid, ammonia, potassium hydroxide, tetramethylammonium hydroxide (TMAH ) May be used as the pH adjusting agent. The pH adjusting agent is used within a range in which a desired pH can be obtained without compromising the function of other components.

As the remaining component of the abrasive grain slurry for chemical mechanical polishing according to the present invention, deionized water may be preferably used. If necessary, a buffer solution for suppressing pH change, various salts for reducing the viscosity of the abrasive grain slurry, etc. It may further comprise a conventional additive of.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples. The following examples are intended to illustrate the present invention more specifically, but the scope of the present invention is not limited by the following examples.

Comparative Example 1

In order to prepare a cerium oxide slurry used for chemical mechanical polishing, cerium oxide powder having a purity of 99.999% was mixed in deionized water to 20% by weight, and then ground using a millizer (Ultimaizer). The counter-impact pressure of the optimizer was adjusted to 2000 kgf / cm ² , and the milling process was performed until the average particle size of cerium oxide became 200 nm. 2 is a photograph of the cerium oxide abrasive particles measured using a transmission electron microscope.

Example 1

 20% by weight of the cerium oxide particles having the average particle size prepared in Comparative Example 1 was adjusted to 200 nm in deionized water, 20% by weight of nitric acid, a mineralizer of hydrothermal reaction, and 20% by weight of the total solution. After hydrothermal reaction for an hour, it was washed 5 times using 20% TMAH (Tetra Methyl Ammonium Hydroxide) and 3 times using deionized water. Then dried in an oven at 110 ℃ for 24 hours.

[Example 2]

 Cerium oxide particles were added in the same manner as in Example 1 except that 10 wt% of the total solution was added and hydrothermally reacted at 120 ° C. for 24 hours.

4 is a graph of XRD diffraction analysis for measuring the size of the crystal phase, crystallinity, and grains of the cerium oxide particles. The grain size of the cerium oxide powder measured using the Scherrer equation was 34 nm.

Example 3-5

After adding 20% by weight of the cerium oxide particles having an average particle size of 190 nm and 20% by weight of nitric acid, a mineralizer of hydrothermal reaction, to deionized water in the same manner as in Comparative Example 1, 160 As shown in Table 1 below, the hydrothermal reaction time was adjusted. Next, after separation of the cerium oxide particles, the remaining supernatant is analyzed by inductively coupled plasma emission spectroscopy (ICP-AES) to measure the amount of cerium oxide dissolved and removed by hydrothermal reaction. It is shown in Table 1 below. The separated cerium oxide particles were washed five times with 20% TMAH, washed three times with deionized water and dried in an oven at 110 ° C. for 24 hours.

In order to evaluate the chemical mechanical polishing performance of the cerium oxide slurry, 1.0% by weight of cerium oxide prepared according to the above method, 1.0% by weight of polyacrylic acid (weight average molecular weight 300,000), 0.01% by weight of zyritol, TMAH for adjusting the pH of the slurry And a residual amount of ultrapure water was prepared. In order to measure the polishing characteristics of the polishing slurry, an oxide film having a thickness of 10,000 Å was deposited on a substrate using a high density plasma deposition (HDP) method, and a nitride film having a thickness of 1,200 Å was deposited using a low pressure chemical vapor deposition method. After polishing the oxide film and the nitride film using a Speedman Co., Ltd. Momantum ^TM polishing equipment, a Rodel IC1400 pad and the polishing slurry, the polishing rate was measured and the polishing selectivity was calculated therefrom. Polishing conditions were 600 rpm orbital, speed, average load pressure of 4.8 psi, and slurry feed rate was 200 ml / min. In addition, fine scratches were measured using KLA2531 equipment of TENCOR, and the measurement results are shown in Table 1 below.

Example
number Hydrothermal reaction time (hr) Amount of dissolved cerium oxide (%) Polishing speed of oxide film
(Å / min) Flatness of oxide film
(%) Polishing speed of nitride film
(Å / min) Nitride
% Flatness Selectivity Fine scratch count (count / sheet) 3 8.0 1.27 2701 8.3 87 6.3 31 24 4 12.0 1.63 2687 7.5 81 5.8 33 21 5 16.0 2.42 2655 7.2 83 5.7 32 15 Comparative Example 1 0 0 2724 7.2 83 5.3 33 31

As shown in Table 1, when the hydrothermal reaction is added to the conventional cerium oxide slurry manufacturing process, it can be seen that the dissolution of the cerium oxide particles increases as the hydrothermal reaction time increases, and as a result, fine scratches are reduced.

As described above, the slurry composition including the cerium oxide abrasive grains for chemical mechanical polishing prepared using hydrothermal reaction has a high polishing rate and can significantly reduce fine scratches. Therefore, by using the polishing slurry composition according to the present invention, it is possible to produce semiconductor devices having excellent quality.

Claims (10)

A mixing process of mixing cerium oxide abrasive particles and water; Milling process of grinding the cerium oxide abrasive particles in the mixed solution; And And hydrothermally reacting the pulverized cerium oxide abrasive particles in the presence of a mineralizer. The method of claim 1, further comprising the step of washing the cerium oxide abrasive particles subjected to the hydrothermal reaction with a cleaning agent. The method for producing cerium oxide abrasive particles according to claim 1 or 2, further comprising the step of drying the washed cerium oxide abrasive particles. The method of claim 1, wherein the milling process is a jet milling process. The method of claim 1, wherein the reaction temperature of the hydrothermal reaction is 60 to 250 ℃ and the reaction time is 10 minutes to 48 hours. The method of claim 1, wherein the mineralizer used in the hydrothermal reaction is selected from the group consisting of phosphoric acid, sulfuric acid, nitric acid and mixtures thereof. The method of claim 6, wherein the content of the mineralizer is 0.1 to 50% by weight of the total hydrothermal solution. The method of claim 2, wherein the cleaning agent used in the cleaning process is selected from the group consisting of ammonia, potassium hydroxide, tetramethylammonium hydroxide (TMAH), and mixtures thereof. Cerium oxide abrasive particles for chemical mechanical polishing prepared according to the method of claim 1.  A chemical mechanical polishing slurry composition comprising cerium oxide abrasive particles, abrasive particle dispersant, pH adjuster and water prepared according to the method of claim 1.

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