KR101094161B1 - Method of manufacturing slurry for chemical mechanical polishing - Google Patents

Abstract

Disclosed is a method of preparing a slurry for chemical mechanical polishing. The method for preparing a chemical mechanical polishing slurry includes preparing abrasive particles; Dry milling the abrasive particles; Mixing the dry milled abrasive particles with a dispersion medium and a dispersant to prepare a mixture for preparing a slurry; Wet milling the mixture for slurry preparation using a wet mill including beads; And filtering the mixture for preparing the wet milled slurry.

Description

Method for producing slurry for chemical mechanical polishing {METHOD OF MANUFACTURING SLURRY FOR CHEMICAL MECHANICAL POLISHING}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the preparation of polishing slurries, and more particularly, to a method of manufacturing a chemical mechanical polishing slurry used in a chemical mechanical polishing (CMP) process in the manufacture of ultra-high density semiconductors.

Chemical mechanical polishing is a technique of planarizing a surface of a polishing film, i.e., a polishing object, formed on a silicon substrate used in manufacturing an ultra-high density semiconductor. In the chemical mechanical polishing process, generally, polishing such as silica, alumina, ceria, etc. Slurries containing particles are used.

Specifically, the slurry is classified into a slurry for oxide, a slurry for metal, and a slurry for poly silicon according to the kind of polishing object. Among them, the slurry for oxide is a slurry used to polish a silicon oxide layer (SiO ₂ Layer) used in an interlayer insulating film and a shallow trench isolation (STI) process, and a ceria slurry using ceria as the abrasive particles is mainly used. . Hereinafter, the ceria slurry will be described as an example.

Polishing of the ceria slurry is performed by chemical reaction with an oxide film deposited on a wafer while poly-crystal ceria particles are broken into a single crystal, and then subjected to mechanical friction with pads. It is a method of grinding away by grinding. At this time, as the proportion of the macroparticles in the abrasive grains increases, a large number of micro scratches occur in the process of breaking the polycrystal into single crystals and in the process of the secondary particles breaking into smaller secondary or primary particles. May occur. The micro scratches adversely affect the quality of the polishing surface. For this reason, it is very important to remove large particles efficiently among abrasive particles.

The present invention provides a method for producing a slurry for chemical mechanical polishing that can minimize micro scratches in the manufacture of ultra-high density semiconductors through the control of process variables in the milling process.

Further objects to be solved by the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description. Could be.

Method for producing a chemical mechanical polishing slurry according to an aspect of the present invention comprises the steps of preparing abrasive particles; Dry milling the abrasive particles; Mixing the dry milled abrasive particles with a dispersion medium and a dispersant to prepare a mixture for preparing a slurry; Wet milling the mixture for preparing the slurry to satisfy the following equation using a wet mill including a bead; And filtering the mixture for preparing the wet milled slurry.

y = -a * Ln (x) + b

In the above equation (1)

y is the average particle diameter of the abrasive particles of the filtered chemical mechanical polishing slurry, 50 to 400 nm,

a represents the average particle diameter of the beads of the wet mill,

x represents wet milling time,

b shows the average particle diameter of dry milled abrasive particle.

According to the present invention, the process variable during wet milling, that is, the average particle diameter of the beads of the wet mill, the wet milling time and the average particle diameter of the dry milled abrasive particles introduced during wet milling can be correlated, so that the process variable Optimization of these components can minimize micro-scratches in the manufacture of ultra-high density semiconductors.

Hereinafter, a method for preparing a chemical mechanical polishing slurry according to an embodiment of the present invention will be described in detail.

1 is a process flowchart for schematically illustrating a manufacturing process of a slurry for chemical mechanical polishing according to an embodiment of the present invention.

Referring to Figure 1, the method for producing a chemical mechanical polishing slurry according to an embodiment of the present invention comprises the steps of preparing abrasive particles (S100), dry milling the abrasive particles (S110), the dry milled polishing Mixing the particles with a dispersion medium and a dispersant to prepare a mixture for preparing a slurry (S120), wet milling the slurry for preparing a slurry (S130), and filtering the wet milled slurry for preparing a mixture (S140). do. Hereinafter, each step will be described in detail.

The method for preparing a chemical mechanical polishing slurry according to an embodiment of the present invention starts with preparing the abrasive particles. Although it does not specifically limit as said abrasive particle, For example, silica, alumina, ceria particle, etc. can be used.

Next, dry milling of the abrasive particles is performed. Recovery of the dry milling is not particularly limited, but may be performed at least twice, for example, to prepare a slurry for chemical mechanical polishing comprising abrasive particles having a smaller average particle diameter. For example, the dry milling may include performing primary dry milling of the abrasive particles such that the average particle diameter of the prepared abrasive particles is 5 to 10 μm, and the average particle diameter of the primary dry milled abrasive particles is 550 to 900 nm. Secondary dry milling of the abrasive particles as much as possible, but the present invention is not limited thereto.

Next, the dry milled abrasive particles may be mixed with a dispersion medium and a dispersant to prepare a mixture for preparing a slurry. When ceria particles are used as the abrasive particles, the ceria particles have a weakly acidic property when mixed with a dispersion medium, for example, ultrapure water. When a dispersant, for example, an anionic polymer dispersant is added to the ultrapure water mixed with the ceria particles, the ceria particles may be aggregated or precipitated may be accelerated due to a difference in pH of the ultrapure water and the dispersant. Therefore, it is preferable to first mix the ultrapure water and the anionic polymer dispersant to stabilize the solvent, and then to mix and wet the ceria particles. That is, after mixing the ultrapure water and the anionic polymer dispersant in a high shear mixer for a predetermined time, the mixture for preparing the slurry can be prepared by mixing and wetting ceria particles as desired, but the present invention is not limited thereto. Here, the anionic polymer compound used as the dispersant is, for example, polymethacrylic acid, polyacrylic acid, ammonium polymethacrylate, ammonium polycarboxylate, carboxyl acrylic polymer, or the like alone or two or more. It can be used in combination.

Next, the mixture for preparing the slurry prepared as described above may be milled with a high energy milling machine to reduce the size of the abrasive particles. The mill can be a wet or dry mill. Among them, the dry mill is low in comparison with the wet mill in terms of the efficiency of the particle size grinding, it is preferable to mill using a wet mill including a bead. In the case of the wet milling, precipitation and reduction of milling efficiency due to agglomeration of abrasive particles, large particle generation, large area size distribution, and the like may occur. In order to prevent this, the size and filling rate of the zirconia beads (adad), adjusting the concentration of the abrasive particles, pH and conductivity control, strengthening dispersion stability using a dispersant may be performed. The size of the abrasive particles may be adjusted by changing the time and the number of times of the milling process.

When wet milling the mixture for preparing the slurry, the recovery thereof is not particularly limited, but may be repeated, for example, at least twice. In addition, the wet milling may be performed to satisfy the following Equation 1.

[Equation 1]

y = -a * Ln (x) + b

In the above equation (1)

y is the average particle diameter of the abrasive particles of the filtered chemical mechanical polishing slurry, 50 to 400 nm,

a represents the average particle diameter of the beads of the wet mill,

x represents the wet milling time or number of passes in the milling process,

b shows the average particle diameter of dry milled abrasive particle.

In Equation 1 above, the average particle diameter of the beads of the wet mill, the wet milling time, and the average particle diameter of the dry milled abrasive particles all correspond to process variables in the wet milling process. Among them, a representing the average particle diameter of the beads of the wet mill may be 150 to 350 μm. In addition, x representing wet milling time or number of passes in the milling process can be from 2 to 200 hours. In addition, b representing the average particle diameter of the dry milled abrasive particles may be 550 to 900 nm. The above process variables may have a specific value within the above range according to the specification of the slurry for chemical mechanical polishing prepared according to one embodiment of the present invention. As such, in an embodiment of the present invention, the correlation between the process variables may be analyzed to optimize them, thereby minimizing micro scratches in the manufacture of ultra-high density semiconductors.

Next, the wet milled slurry mixture may be prepared using a filter to filter large particles in the mixture to prepare a slurry for chemical mechanical polishing according to an embodiment of the present invention. The filtering may be repeated at least twice as necessary.

Since the macroparticles can be filtered as the filter, the filter is not particularly limited. For example, a membrane filter, a depth filter, or a pleated filter may be used. The membrane filter has a porous film shape, and unlike a filter medium formed by interlocking fibers with each other, the membrane filter has a ball structure in which holes close to a circle are connected to each other. The depth filter has a structure having a thick filter layer, and the filter has a density gradient (that is, a denser structure in the inner layer and a coarse structure in the outer layer) to gradually capture particles in the liquid step by step. This is a filter that can be done. The pleated filter is a filter having a continuous pleated structure, and can maintain maximal filtration area to improve filtration performance even at a low differential pressure.

Pores are formed in the filter, and the pore size may vary depending on the size of the large particles to be filtered or the average particle size of the abrasive particles remaining in the filtered slurry preparation. For example, when the average particle diameter of the abrasive particles remaining in the filtered slurry preparation mixture is to be 80 to 150 nm, the pore size may be 0.1 to 0.8 μm. As another example, when the average particle diameter of the abrasive particles remaining in the filtered slurry preparation is to be greater than 150 and less than or equal to 270 nm, the pore size may be greater than 0.8 and 1.2 µm or less. As another example, when the average particle diameter of the abrasive particles remaining in the filtered slurry preparation is to be greater than 270 and less than 400 nm, the pore size may be greater than 1.2 and less than 4 μm. However, since the average particle diameter of the abrasive particles remaining in the filtered slurry preparation and the corresponding pore size may vary depending on the type, structure, and size of the filter, and the filtering speed, time and recovery, and the like. It is not limited.

While the embodiments of the present invention have been described above, it will be understood by those skilled in the art that the present invention may be implemented in other specific forms without changing the technical spirit or essential features thereof.

Therefore, it should be understood that the above-described embodiments are provided so that those skilled in the art can fully understand the scope of the present invention. Therefore, it should be understood that the embodiments are to be considered in all respects as illustrative and not restrictive, The invention is only defined by the scope of the claims.

1 is a process flowchart for schematically illustrating a manufacturing process of a slurry for chemical mechanical polishing according to an embodiment of the present invention.

Claims (8)

Preparing abrasive particles; Dry milling the abrasive particles; Mixing the dry milled abrasive particles with a dispersion medium and a dispersant to prepare a mixture for preparing a slurry; Wet milling the mixture for preparing the slurry to satisfy the following equation using a wet mill including a bead; And Filtering the mixture for preparing the wet milled slurry Method for producing a chemical mechanical polishing slurry comprising a. y = -a * Ln (x) + b (In the above equation, y is the average particle diameter of the abrasive particles of the filtered chemical mechanical polishing slurry, 50 to 400 nm, a represents the average particle diameter of the beads of the wet mill, x represents wet milling time, b represents the average particle diameter of dry milled abrasive particles.) The method of claim 1, Method for producing a slurry for chemical mechanical polishing, wherein the abrasive particles are silica, alumina, or ceria particles. The method of claim 1, Wherein the dry milling is performed at least twice. The method of claim 1, wherein the dry milling step, Primary dry milling the abrasive particles so that the average particle diameter of the prepared abrasive particles is 5 to 10 μm; And Secondary dry milling the abrasive particles so that the average particle diameter of the primary dry milled abrasive particles is 550 to 900 nm Method for producing a chemical mechanical polishing slurry comprising a. The method of claim 1, Wherein the wet milling is performed at least twice. The method of claim 1, Formula a is a method for producing a slurry for chemical mechanical polishing is 150 to 350㎛. The method of claim 1, X in the above formula is a method for producing a chemical mechanical polishing slurry for 2 to 200 hours. The method of claim 1, B in the formula is 550 to 900nm method for producing a slurry for chemical mechanical polishing.

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