KR100341141B1 - Slurry for Polishing Inter Layer Dielectric of Semiconductor in Chemical Mechanical Polishing Process and Method for Preparing the Same - Google Patents

Abstract

The present invention relates to an oxide polishing slurry and a method for manufacturing the same in a semiconductor planarization process (CMP), 5 to 25 parts by weight of fumed silica, 75 to 95 parts by weight of deionized ultrapure water, 0.1 to 0.5 parts by weight of pH regulator, and alkaline properties. Mixing 0.0001 to 0.1 parts by weight of one or more additives selected from the group consisting of min, tetravalent ammonium compounds and cutting surfactant in a high shear mixer; Repeating the process of filtration with a filter to remove impurities in the mixture and silica particles of 10 µm or more and a process of dispersing at high pressure to uniformly disperse the silica concentration within a range of 8-25%; And it relates to a method comprising the step of filtration with a filter to remove particles of 700nm or more and the oxide film polishing slurry of the semiconductor CMP process prepared by the method. The method according to the invention is characterized by not only controlling the uniform particle size distribution and particles of 0.7 micron or more, but also strictly controlling the metal ions contained in the slurry solution, and the prepared slurry exhibits excellent polishing properties.

Description

Slurry for Polishing Inter Layer Dielectric of Semiconductor in Chemical Mechanical Polishing Process and Method for Preparing the Same}

The present invention relates to a slurry for polishing an oxide film in a semiconductor mechanical mechanical polishing (CMP) process and a manufacturing method thereof, and more particularly to a slurry used for planarizing an oxide film of a semiconductor in a semiconductor mechanical polishing process. It relates to a manufacturing method.

Recently, the VLSI semiconductor device has a structure in which an oxide insulating film and a wiring metal thin film are alternately layered, and the number of insulating-metal layers is increasing. As the layer builds up, the curvature of the surface expands, resulting in poor flatness, which is beyond the margin of focus depth in lithography. Therefore, after the thin film deposition, a flat surface having a surface roughness (step difference) of several hundred nm is required, and a separate process (CMP-Chemical Mechanical Planarization) has a global planarization of memory semiconductors and non-memory semiconductors having a line width of 0.35 μm or less. Is being applied to.

On the other hand, the slurry is classified into an oxide [ILD (Inter Layer Dielectric)], a metal (W, Ti, TiN, Al, Cu), and a polysilicon depending on the object to be polished. Slurry is a key element to polish the surface by direct contact with the semiconductor, and it is a very important process material that needs to be applied sensitively according to the kind of surface to be planarized and the required polishing specification. 6 months), storage temperature is low temperature (below 5 ℃) or high temperature (40 ℃ or more) agglomeration of particles, etc., causing strict quality control and a lot of research and development is required.

Existing abrasives are abrasives for planarizing the surface of the wafer, that is, abrasives used for polishing a substrate surface such as silicon and film formation on the substrate, and include abrasive particles such as silica, water as a solvent, It consists of water-soluble cellulose for forming a hydrophilic film, and pH adjusters, such as ammonia added as needed. In most cases, similar methods and similar additives are used, and most of them are only homogeneous and finely dispersed silica particles in an aqueous solution.

However, since the CMP process is used as a method for planarizing the surface curvature due to the high integration of the memory semiconductor device, the CMP process is essentially used in the 64 mega memory class and the non-memory semiconductor. In other words, as semiconductor design rules are beginning to become finer and semiconductor processes and device structures are different, the developed slurry is applied to semiconductor CMP processes and evaluated as a slurry. In addition, as the device progresses in miniaturization, the purity of the slurry is also important, and there is a demand for a slurry of higher purity and high precision polishing that does not cause scratching. Oxide polishing slurries reported so far contain a large amount of alkali metals and metal impurities such as Na, which may cause various environmental problems, polysilicon resistance abnormalities, short circuits, and the like. In the case of a slurry using a material having a low standard of breaking point such as ammonia, alkali agents tend to vaporize, and thus there are problems such as retention of abrasives and stability of polishing at that time.

The composition of the slurry consists of additives such as water, abrasive grains, alkali, various inorganic salts and organic compounds, and the specific slurry is prepared by appropriate selection of these compositions. The most important characteristics of the slurry include the uniform dispersion of abrasive particles, such as scratches, the minimization of metal residual amount that causes polysilicon resistance abnormalities or wiring short circuits, selective polishing characteristics, viscosity, and storage stability. Commonly used solvents are deionized high-purity ultrapure water having a resistivity of about 5 to 18 MΩcm, in which most impurities such as ions, fine particles, microorganisms, and organic substances are removed. Slurry is composed of abrasives (Fumed Silica, etc.), additive types and the size of particles dispersed according to the dispersion method and dispersion process, the concentration of metal ions in the slurry, the change over time of the dispersed particles, polishing characteristics, residual metal after polishing It shows different physical properties such as ions and detergency.

Planarization of the oxide film is more important than the metal film mechanical or physical properties of the slurry particles. The oxide film requiring planarization is an isolation trench, an intermetal dielectric, a pre-metal dielectric, and the like, and the composition and composition of the slurry polishing liquid vary depending on the application. The abrasive particles include fumed silica, colloidal silica, Al ₂ O ₃ , CeO ₂ , TiO ₂ , MgO, ZrO ₂ , Fe ₃ O ₄ , HfO _2, and the like. The size of the dispersed particles is on the order of several hundred nm, and the average size, surface area, particle size distribution, composition, hardness, structure and shape of the particles have an absolute influence on the polishing rate and defects on the polishing surface. In addition to the abrasive particles, various additives are included for controlling the stability, chemical polishing, and physical properties of the slurry. Alkaline salts, for example, act as a buffer to control the pH appropriate for the polishing process and to minimize the change in pH during the process. Anionic or nonionic surfactants are used to increase the stability of the abrasive particles dispersed in the suspension solution, and also to control the surface charge density and surface growth of the slurry to improve the cleanability on the wafer surface after the process. Water-soluble polymers and organic substances of alcohols or amines may be added for particle dispersion and colloidal stability.

In order to prepare a slurry suitable for planarization of silicon oxide, it is possible to select abrasive particles which ensure fast polishing speed and leave no defects on the surface, fine and uniform dispersion by controlling secondary agglomerated particles, and controlling chemical reactions in the process. Selection of additive chemicals and control of added concentrations is important, and control of viscosity and dielectric constant, physical properties that affect the process, and prevention of flocculation and zeta potential control to improve storage stability of the final product. Finally, the ease of cleaning of the slurry and the slurry metal impurity content should be reached to an appropriate level to suppress surface contamination after the process.

Accordingly, an object of the present invention is to provide a method for producing an oxide film polishing slurry used in a semiconductor planarization process that can solve the above-described problems of the prior art.

Another object of the present invention is to provide a slurry prepared by the above method.

The production method of the present invention for achieving the above object is 5 to 25 parts by weight of fumed silica, 75 to 95 parts by weight of deionized ultrapure water, 0.1 to 0.5 parts by weight of pH adjusting agent and alkali component, tetravalent ammonium compound and cutting surfactant Mixing 0.0001 to 0.1 parts by weight of one or more additives selected from the group consisting of in a high shear mixer; Repeating the process of filtration with a filter to remove impurities in the mixture and silica particles of 10 µm or more and a process of dispersing at high pressure to uniformly disperse the silica concentration within a range of 8-25%; And filtering with a filter to remove particles at least 700 nm.

In addition, the slurry prepared according to the present invention is characterized in that the uniform particle size distribution and particles of 700nm or more are controlled, and the metal ions contained in the slurry solution are strictly controlled, and the slurry exhibits excellent polishing characteristics. It is done.

In the slurry production method of the present invention, after dispersing the fumed silica as an abrasive in a high share in an aqueous solution to prepare a slurry having an initial particle size of 10 μm or less, an additive which can control various characteristics of the slurry is added to a high pressure. It is characterized in that the dispersion.

1 is a graph showing the particle size distribution of the slurry prepared according to the present invention,

Figure 2 is a graph showing the storage stability at room temperature and low temperature of the slurry prepared in the present invention,

3 is a graph showing the metal ion content contained in the slurry of the present invention,

4a to c are graphs showing a CMP process window test using the slurry of the present invention;

5 is a graph showing the performance and repeat tests of the slurry according to the invention evaluated in the CMP process.

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

First, in the present invention, 5 to 25 parts by weight of fumed silica, 75 to 95 parts by weight of deionized ultrapure water, 0.1 to 0.5 parts by weight of pH adjusting agent, and an alkali component, a tetravalent ammonium compound, and a cutting surfactant 0.0001 to 0.1 parts by weight of the additive selected above is mixed in a high shear mixer.

Conventional fumed silica is used as the abrasive particles in the present invention, but the fumed silica in the present invention is a grade of purity of 99.9% or more in which HCl and metal impurities produced through gas phase combustion reaction are suppressed to the maximum, and slurry performance is achieved. For the purpose of improvement and control, the surface area of the silica particles is in the range of 70 to 160 m 2 / g, the shape is spherical, the density of hydroxyl groups (-OH) on the surface is 2 to 10 / nm ² , and the average density is 0.1 to 0.5 g / cm 3 is used. If the above conditions are exceeded, there is a problem in controlling particle aggregation and controlling particle size microdistribution due to a change in the surface characteristics of silica. In addition, the amount of fumed silica is preferably 5 to 25 parts by weight, in order to exhibit excellent polishing characteristics while suppressing aggregation of silica particles in alkaline water-soluble.

In order to prepare the slurry according to the present invention, ultrapure water must be used to remove metal ions in the aqueous slurry solution. The ultrapure water was used in consideration of the stability of the dispersed silica 75 to 95 parts by weight, less than 75 parts by weight has a problem in stability, when exceeding 95 parts by weight is poor in polishing performance.

Polishing compositions according to the present invention is usually used in the form of a slurry and its pH condition is preferably in the range of 10 to 12. This pH is not only an important factor affecting the state of silica in the dispersion process, but also an important factor in the polishing performance of the slurry. KOH is used as the pH adjusting agent, and the amount of use thereof is preferably in the range of 0.1 to 0.5 parts by weight.

In addition, as the other additive, one or more additives selected from the group consisting of an alkali component, a tetravalent ammonium compound, and a cutting surfactant are used at 0.0001 to 0.1 parts by weight. If the amount of the additive is less than 0.0001 parts by weight, the effect on the slurry is reduced, and when it exceeds 0.1 parts by weight, the properties of the slurry, such as pH, are affected.

The alkali component not only affects the interfacial properties of the slurry particles and the polishing properties during the CMP process, but also adjusts the pH of the slurry. The alkali component is preferably a potassium-based compound such as KCl, K ₂ CO ₃ or KHCO ₃ .

The tetravalent ammonium compound is used for the purpose of increasing detergency, and tetramethylammonium hydroxide or tetraethylammonium hydroxide is preferable. In addition, a surfactant for cutting may be used for the purpose of adjusting the polishing performance.

According to the present invention, the mixture is mixed in a high shear mixer, and then filtered to remove impurities and silica particles of 10 µm or more in the mixture, and to uniformly disperse the silica concentration within the range of 8-25%. The process of dispersing at high pressure is repeated. The filtration and dispersion process is filtered using a filter under a pressure of 1 ~ 10kg / ㎠, dispersed, and filtered again to repeat the process of dispersing it. After the repetition process, the filter is filtered and terminated to remove particles larger than 700 nm.

Fumed silica, when dispersed in ultrapure water, has a uniform distribution in size distribution of secondary agglomerated particles, and undergoes at least two or three dispersion processes to reduce the distribution width and reduce the average particle size. The primary dispersion process is to disperse the fumed silica in ultrapure water for fine dispersion, so that the maximum size of the dispersed particles is 10 μm or less. The first dispersion process is a dispersion process consisting of a high-speed rotation method of shear stress of 5,000 / sec to 1,000,000 / sec using a hermetic rotor / stator type disperser and an inline pump type rotor / stator. to be. In the second dispersion process, the dispersion process is performed at a high pressure of 2,000 psi or more to maintain the concentration of silica in the range of 8 to 25%.

Through this process, impurities in the mixture and silica particles larger than 700 nm are removed, and the measurement of the secondary agglomerated particle size and distribution of the slurry is carried out using a Malvern mastersizer and a Matech CHDF equipment. Used. As the average particle size, as shown in the mastersizer measurement result in FIG. 1, the center size (D ₅₀ ) was taken from the size distribution for the volume% of each particle, and the mono-dispersity (Mono) representing the degree of dispersion. -dispersity) were adopted, divided by the size (D ₂₅₎ is one-quarter the size (D ₇₅₎ which is 3/4 in size distribution (D ₇₅ / D ₂₅₎ mean value particle 140~190nm, and the surface tension The viscosity was 50 to 70 dyen / cm, and the viscosity was adjusted to 10 cps or less at 60 rpm using a Brookfield viscometer, and the zeta potential of the slurry was -30 mV or less.

In the present invention, to minimize the secondary (Secondary) particles of the slurry that causes scratches in the semiconductor. As shown in Table 1 below, the secondary particles of the slurry having a silica fraction of 12 wt% showed an average of 160 to 190 nm, and analyzed by an Accusizer 780 device of Particle Sizing System. The number of particles having a size of 1 μm or more is 20,000 or less per 1 ml of slurry, the number of particles having a size of 3 μm or more is 2,000 or less per 1 ml of slurry, and the number of particles having a size of 7 μm or more is slurry 1 Less than 200 values per ml was shown, and as shown in FIG.

Slurry in the present invention minimizes the content of Fe, Cu, Al, Ni, Ca, Mg, and Zn ions, which are metals that cause abnormal polysilicon resistance or wiring short, to 50 ppb or less as shown in FIG. It was. As shown in FIG. 3, the slurry obtained in the present invention is a slurry having a low concentration of Al ions and Fe ions of 6 to 20 times or more compared to the compared slurries.

Analysis and evaluation in the Examples and Comparative Examples in the present invention was carried out by the following method.

-: Specific Gravity

KS M 0004, how to use a pycnometer with a gay Lussac thermometer (@ 25)

-: Mean Particle Size

Equipment 1: Matec Applied Sciences Model CHDF 2000

Principle: Capillary Hydrodynamic Fractionation

Equipment 2: PSS NICOMP 370

Principle: Laser Scattering

-: Particle number counting

Equipment: PSS Accusizer 780

Principle: Single Particle Optical Sensing

-: pH

Equipment Used: Mettler DL 25 / Glass Electrode (@ 25)

-: Viscosity

Equipment used: Brookfield Model DV II + Viscometer, UL adapter (@ 25)

-: Surface Tension

Equipment Used: Advancing Rheology Surface Science Processor Tensiometer K10ST

Adopting method: Ring method and Plate method

-: Zeta Potential

Equipment used: Brookhaven Instruments, Zetaplus (Zeta Potential Analyser)

Principle: Dynamic light scattering

-: ICP Mass

Metal ion content evaluation

-: CMP rating

CMP performance evaluation was performed using the IPEC 776 equipment of the slurry prepared in the present invention, the process conditions were slurry feed rate 200ml / min, spindle rotation speed 280rpm, Load pressure was 5psi. As the polished silicon oxide film, 8 inch diameter silicon wafer of PETEOS film (Film) was used, and the polishing rate was calculated by TENCOR UV1250 after the CMP process. As shown in Figure 4, the slurry obtained in the present invention was found to be able to adjust the polishing rate according to the CMP conditions. That is, the polishing speed is proportional or uniform according to down force, orbital speed, and slurry flow rate, resulting in a numerical value that can be adjusted appropriately according to the device. It was found to be a suitable slurry for the CMP process.

As a result of performing the CMP test with 50 wafers under the same conditions for the repetitive test of the slurry obtained in the present invention, as shown in FIG. 5, the average polishing rate was 2098 Å, and WTW RR NU ( Wafer to Wafer Removal Rate Non-uniformity was 2.72% and mean nonuniformity was 0.97%.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the following examples.

Example 1

After adding 10 kg of fumed silica having a surface area of 90 m2 / g to a reactor containing 72.27 kg of ultrapure water, 300 g of KOH, 14 g of K ₂ CO ₃ , 11 g of KHCO ₃ , and 0.5 g of tetramethyl ammonium hydroxide were mixed together to prepare a high shear mixer. Mix using. The mixture was filtered under a pressure of about 5 kg / cm 2, and the shear stress was first dispersed in a high speed rotation method of about 100,000 / sec using a hermetically sealed rotor / stator type disperser so that the maximum size of the dispersed particles was 10 μm or less. Was made. The solution was again filtered and filtered under a pressure of about 5 kg / cm 2, and then dispersed under a pressure of 8,000 psi using a high pressure disperser to obtain a uniform solution having a silica concentration of about 12%. Physical properties of the slurry-like substance of the obtained solution are as shown in Table 1 below.

Example 2

10 kg of fumed silica having a surface area of 90 m 2 / g was added to a reaction tank containing 72.27 kg of ultrapure water, and then 300 g of KOH, 14 g of K ₂ CO ₃ , 11 g of KHCO ₃ , and 0.5 g of polysilanol-based surfactant were mixed together. The same procedure as in Example 1 was carried out except that the mixture was mixed using a high shear mixer. The physical properties of the slurry-like substance of the obtained solution are shown in Table 1 below.

Example 3

After adding 10 kg of fumed silica with a surface area of 130 m2 / g to a reactor containing 72.27 kg of ultrapure water, 300 g of KOH, 14 g of K ₂ CO ₃ , 11 g of KHCO ₃ and 0.5 g of tetramethyl ammonium hydroxide were mixed together to prepare a high shear mixer. It carried out similarly to Example 1 except having used and mixed. The physical properties of the slurry-like substance of the obtained solution are shown in Table 1 below.

Example 4

After adding 10 kg of fumed silica having a surface area of 90 m2 / g to a reactor containing 86.72 kg of ultrapure water, 280 g of KOH, 14 g of K ₂ CO ₃ , 11 g of KHCO ₃ , and 0.5 g of tetramethylammonium hydroxide were mixed together to prepare a high shear mixer. It carried out similarly to Example 1 except having used and mixed. A uniform solution having a silica concentration of about 10% was obtained, and the physical properties of the slurry-like material of the obtained solution are shown in Table 1 below.

Comparison of Slurry Properties and CMP Performance Results Example One 2 3 4 Average secondary particle size (NICOMP 370 equipment) 160 nm 180 nm 190 nm 160 nm Mono-dispersity 1.45 1.57 1.65 1.40 Average secondary particle size (CHDF equipment) 140 nm 160 nm 155 nm 140 nm pH 10.8 10.6 10.7 10.8 Viscosity (cP, @ 21 ° C, 60 rpm 5.0 5.2 5.2 5.0 Removal Rate (TEOS Oxide) 210nm / min 210nm / min 200 nm / min 180 nm / min WIWNU 0.97% 2.55% 2.10% 1.23

As described above, the slurry prepared by the method of the present invention has a shape in which the size distribution of the aggregated particles is uniformly distributed, and can control a uniform particle size distribution and particles of 0.7 micron or more. In addition, the slurry prepared according to the present invention is characterized in that the metal ions contained in the slurry solution are strictly controlled, and the prepared slurry has an effect of exhibiting excellent polishing characteristics.

Claims (7)

5 to 25 parts by weight of fumed silica, 75 to 95 parts by weight of deionized ultrapure water, 0.1 to 0.5 parts by weight of pH adjusting agent, and one or more additives selected from the group consisting of an alkali component, a tetravalent ammonium compound and a cutting surfactant 0.0001 Mixing -0.1 parts by weight in a high shear mixer; Repeating the process of filtration with a filter to remove impurities in the mixture and silica particles of 10 µm or more and a process of dispersing at high pressure to uniformly disperse the silica concentration within a range of 8-25%; And A method for producing an oxide film polishing slurry of a semiconductor CMP process comprising the step of filtration with a filter to remove particles of 700 nm or more. The semiconductor according to claim 1, wherein the fumed silica has a surface area of 70 to 160 m 2 / g, a density of hydroxyl groups on the surface of 2 to 10 atoms / nm ² , and an average density of 0.1 to 0.5 g / cm 3. A method for producing an oxide film polishing slurry in a CMP process. The method of claim 1, wherein the pH adjusting agent is potassium hydroxide. The method of claim 1, wherein the alkali component is KCl, K ₂ CO _3, or KHCO ₃ . The method of claim 1, wherein the tetravalent ammonium compound is tetramethylammonium hydroxide or tetraethylammonium hydroxide. The semiconductor CMP process according to claim 1, wherein the first dispersion process in the dispersion process is performed by a high-speed rotation method of 5,000 to 1,000,000 / sec shear stress, and the second dispersion process is performed at a high pressure of 2,000 psi or more. Method for producing an oxide film polishing slurry. It is prepared by the method of any one of claims 1 to 6, the average particle size is 140 ~ 190nm, the surface tension is 50 ~ 70dyen / cm, the viscosity is 10cps or less, Fe, Cu, Al, Ni, Ca, Mg And an oxide film polishing slurry of a semiconductor CMP process, wherein the Zn ion content is 50 ppb or less.