KR100665300B1 - Ceria slurry for chemical mechanical polishing and its fabrication method - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing slurry, which is used in a CMP process for an STI process, which is essentially applied to an ultra-high density semiconductor manufacturing process having a design rule of 256 mega DRAM or more, for example, 0.13 μm or less. It relates to a slurry having a high selectivity ratio of the oxide layer to the layer and a method for producing the same. The present invention is suitable for the STI process of ultra-high density semiconductor manufacturing process of 0.13㎛ or less by appropriately operating the method and apparatus for pretreatment of abrasive particles, dispersion equipment and its operation method, method and amount of adding chemical additives, transporting device for samples and the like. The present invention relates to the preparation of high performance nano ceria slurries that are essential for a CMP process.

CMP, slurry, surface area, anionic polymer dispersant, macroparticles, particle size, interfacial potential behavior, milling

Description

Ceria slurry for chemical mechanical polishing and its manufacturing method {CERIA SLURRY FOR CHEMICAL MECHANICAL POLISHING AND ITS FABRICATION METHOD}

1 is a process flow diagram of slurry production according to the present invention

2 is a schematic diagram of a polishing mechanism of ceria abrasive

3 is a particle size distribution of the slurry by the number of milling in the milling process

4 is a process flow diagram of preliminary step milling and main step milling.

5 is a particle size distribution adjusted through preliminary step milling.

6 is a particle size distribution of the final slurry in the case of preliminary milling and when prepared without preliminary milling.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to polishing slurries, in particular to chemical mechanical polishing (hereinafter abbreviated as 'CMP'), to polishing slurries used in chemical mechanical polishing processes for planarization of semiconductor laminates. More specifically, the shallow trench isolation CMP process, which is essential for ultra-high-density semiconductor manufacturing processes of 256 mega DRAM or more (design rule of 0.13 µm or less), is high in the nitride layer used as a barrier layer in the CMP process. The present invention relates to a polishing slurry having a polishing selectivity and capable of suppressing the occurrence of scratches on a flattening surface and a method for producing the same.

Chemical mechanical polishing (CMP) is one of the semiconductor processing techniques in which the mechanical processing by the abrasive present between the pressed wafer and the polishing pad and the chemical etching of the slurry are performed simultaneously. This is an essential process of global planarization technology in the manufacture of submicron scale semiconductor chips since it was developed by IBM in the late 1980s.

The type of slurry is largely classified into an oxide slurry, a slurry for metals, and a polysilicon slurry according to the kind of object to be polished. An oxide slurry is a slurry used to polish a silicon oxide layer (SiO ₂ layer) used in an interlayer insulating film and shallow trench isolation (STI) process, and is mainly composed of abrasive particles, deionized water, a pH stabilizer, and a surfactant. It is composed. Double abrasive particles act to mechanically polish the surface under pressure from a polishing machine, and mainly silica (SiO ₂ ), ceria (CeO ₂ ), alumina (Al ₂ O ₃ ), and the like are used.

In particular, a ceria slurry using ceria as abrasive particles is widely used to polish a silicon oxide layer in an STI process, and a silicon nitride layer is mainly used as a polishing stop layer. Generally, certain additives are added to the ceria slurry to improve the selectivity of the oxide layer to the nitride layer, but in this case, not only the nitride layer removal rate but also the oxide layer removal rate is reduced. In addition, since the abrasive particles of the ceria slurry are usually larger than the abrasive particles of the silica slurry, and a large amount of large particles are present, relatively agglomeration is caused, there is a problem of causing scratches on the wafer surface.

On the other hand, when the polishing rate selection ratio of the oxide layer to the nitride layer is small, there is a problem in that a dishing phenomenon in which the oxide layer is excessively removed due to the loss of the adjacent nitride layer pattern, may not achieve uniform surface planarization. .

Therefore, the properties required for these STI CMP slurries are high selectivity, polishing rate, dispersion stability, micro-scratch stability, and a large number of particles having a narrow uniform uniform particle size distribution and a size of 1 μm or more. It must be within a certain range.

As a prior art for preparing a slurry for STI CMP, US Pat. Nos. 6,221,118 and 6,343,976 to Hitachi disclose a method for synthesizing ceria particles and a method for preparing a high selectivity slurry using the same. Here, the characteristics of the particles required for the slurry properties for STI CMP, the types of additives including polymers, and the manufacturing method and process using them are described in a very difficult and wide range. In particular, a wide range is given for the average grain size, average primary particles and average secondary particles. Particular attention is given to the change in grain size with the calcination temperature and the resulting scratch. Another conventional technique is a method of synthesizing various ceria particles described in US Pat. No. 6,420,269 to Hitachi, and a method for producing a high selectivity slurry using the same. On the other hand, US Patent Publication No. 6,615,499 of Hitachi mentions the change of ratio between peak intensity of a specific region and the change of polishing rate according to the X-ray analysis result according to the heating rate in the calcination process. have.

Also, as another conventional technique, US Pat. Disclosed is a method and a method for preparing a high selectivity slurry using the same. These inventions mainly describe the types of additives in the slurry, the effects thereof, and the coupling agent.

However, this prior art only describes the average particle size and range of the abrasive particles constituting the polishing slurry, and detailed considerations on the characteristics of the particle size distribution of the slurry and how to make the particle size distribution as narrow and uniform as possible are described. Lack. However, considering the micro scratches caused by the large particles in the slurry, it is very important to narrow the particle size distribution of the slurry and minimize the long tail. Accordingly, the present invention provides a method capable of minimizing micro scratches by appropriately utilizing milling and dispersing equipment. In particular, it is much narrower than single-step milling using one type of milling machine, but not through the limit value of the size of the particles that can be ground, that is, multi-step milling using several types of mills with different milling efficiencies. The milling process proceeds to provide a slurry of uniform particle size distribution. According to the present invention, by providing a slurry having a narrow and uniform particle size distribution, not only to facilitate the filtering process, but also to maintain a high polishing rate while minimizing micro scratches.

Therefore, in order to solve the above problems, the present invention provides a method of pretreatment and apparatus for dispersing various particles, a dispersing equipment and its operating method, a method and amount for adding chemical additives, and a transportation device for samples. It is an object of the present invention to provide a high performance nano ceria slurry that can be applied to an STI process in an ultra-high-density semiconductor manufacturing process and can minimize a deadly micro scratch in a semiconductor device.

In particular, the present invention uses a milling process that is made by mixing ceria powder and ultrapure water (DI water), a milling process that can adjust the particle size of the slurry using a variety of milling machines with different milling efficiency rather than a single step using a milling machine. Proceeding to multi-step provides a dispersion stabilized slurry that has a very narrow and uniform particle size distribution, and that microscratches can be obtained at an appropriate polishing rate with minimal.

The present invention relates to a polishing slurry comprising abrasive particles, wherein the milling of at least two stages is carried out using a milling machine having a different limit value of the crushable particle size, and the grain size of the abrasive grains is 50 탆 or less before the final stage milling. It provides a polishing slurry having a range. In particular, the particle size before the final stage milling is distributed in the range of 0.1 μm to 50 μm.

Very narrow particle size distribution by performing the milling process that can control the particle size of the polishing slurry including the abrasive particles to at least two stages of multi-step milling rather than a single stage using a mill having a different efficiency With this, it is possible to obtain a dispersion stabilized polishing slurry which can obtain an appropriate polishing rate while minimizing micro scratches.

In the above, the mill may use any one of a low efficiency mill, which grinds large particles, a medium efficiency mill, and a high efficiency mill that grinds small particles into fine particles, and the particle size of the abrasive particles before the final stage milling may be 0.5 µm to It is distributed in the range of 40 µm. It is also preferable that the particle size of the abrasive particles before the final step milling has a range of 0.6 μm to 30 μm.

In addition, the present invention comprises the steps of preparing the abrasive particles, performing the preliminary milling so that the particle size of the abrasive particles is in the range of 50㎛ or less and the limit value of the particle size that can be crushed with the preliminary milling is different It provides a method for producing a polishing slurry comprising the step of performing the main step milling using a milling machine.
In the main step milling, milling may be performed using a high efficiency mill that grinds small particles into fine particles.
The preliminary step milling may be performed by milling at least one or more times using a low efficiency mill or a medium efficiency mill that grinds large particles, or after performing at least one milling with a low efficiency mill, The milling can be carried out at least once.

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In the above, the high efficiency mill includes a wet bead mill, and the low efficiency mill includes a dry mill or a ball mill. In addition, the medium efficiency mill includes a ball mill or bead mill that can be used by adjusting the size of the ball and the beads to a few mm.

Hereinafter, each part will be described in detail by dividing the manufacturing process of the polishing slurry of the present invention and the analysis and analysis of the resulting polishing slurry. In the following description of the present invention with specific examples, ceria is used as an example of an abrasive and ultrapure water (DI water) and anionic polymer dispersant are used as the dispersion medium and the dispersant. In addition, the CMP results such as the production method of the polishing ceria slurry and the oxide film polishing rate and selectivity of the slurry prepared in a single step and a multi-step process will be described. The present invention described below may be modified in many different forms, and the scope of the present invention is not limited to the following description.

[Ceria Slurry Preparation]

The ceria slurry of the present invention contains additives such as ceria powder, ultrapure water (DI water) and anionic polymer dispersant, a weak acid or a weak base. The method for producing the polishing ceria slurry is approximately as follows (see FIG. 1).

First, a precursor such as cerium carbonate is pretreated. That is, ceria powder is prepared by solid phase synthesis (S1). The ceria powder is mixed and wetted with ultrapure water (DI water) in a mixing tank (S2), and milled with a milling machine (S3) for particle size reduction and dispersion. Anionic polymer dispersant is added to the initial slurry prepared by the above method to increase dispersion stability (S4), and the pH is adjusted by mixing additives such as weak acid or weak base with a high speed mixer. After dispersion stabilization through additional milling (S5), the weight ratio of the slurry (wt%), that is, the solid load to the desired range (S6), and then remove the large particles through filtering to prevent scratches during precipitation and polishing (S7) and further aging (stabilize) the slurry (S8).

Such a method for producing a polishing ceria slurry of the present invention will be described in detail for each step as follows.

1. Preparation of Ceria Powder

The preparation of the ceria slurry of the present invention begins with the preparation of ceria powder with ceria raw material precursor (precursor) through solid phase synthesis. The ceria powder may be synthesized by calcining a precursor such as cerium carbonate, for example, and may be subjected to a separate drying process to remove moisture adsorbed before full calcining. This is because precursors treated through the drying process are excellent in terms of ease of transfer and treatment in the process.

The ceria powder varies depending on the conditions for calcining cerium carbonate and the configuration of the calcining apparatus. Cerium carbonate has crystalline water and adsorbed water, and crystalline water often has tetravalent, pentavalent, hexavalent and the like, and the calcination conditions vary depending on the number of crystallized water and the amount of adsorbed water. When calcining, firstly, crystal water and adsorbed water are removed. The ceria powder then begins to synthesize as a carbon dioxide decarbonation occurs in which the carbonate function is removed in the form of carbon dioxide through further elevated temperature and first heat treatment. Next, ceria powder having particles of various sizes is formed by recrystallization by an additional second heat treatment. It is effective to perform calcination in 500-1000 degreeC temperature range.

2. Mixing and Milling

The ceria powder prepared by the above method is mixed and wetted using ultra pure water (DI water) and a high shear mixer. Thereafter, the mixture is milled to reduce particle size and dispersed to produce nano-sized ceria slurry.

After the mixing and wet process, a low efficiency milling machine, a middle efficiency milling machine, or a high efficiency milling machine to control the particle size and disperse the aggregated abrasive particles ) Can be used to proceed with particle size reduction and dispersion. Here, the efficiency of the mill represents the limit value of the particle size that can be crushed during milling according to each machine.

The above mill is a low efficiency mill including a dry mill or a wet ball mill using a large ball size of several centimeters depending on the milling efficiency, a medium efficiency mill or wet bead including a wet ball mill using a small millimeter of ball size. It can be distinguished by high efficiency mills including mills, each of which has different milling performance and characteristics. For example, low-efficiency mills with relatively large limits on the size of particles that can be ground are efficient at breaking large particles quickly, but are difficult to break small particles. On the other hand, high efficiency mills with a relatively small limit on the size of the particles that can be ground are effective for grinding small particles into fine particles. However, in the case of the slurry for CMP, it is important to obtain fine abrasive particles free of contamination, and therefore, milling using a wet mill mainly made of a ceramic material is preferable. On the other hand, in the case of using the wet milling method, in order to prevent precipitation and reduction of milling efficiency due to agglomeration of abrasive particles, generation of large particles, large area size distribution, etc., the concentration of abrasive particles, pH and conductivity control, and a dispersant may be used. It is effective to enhance dispersion stability.

The present invention takes advantage of the different performance of these different mills before the preliminary stage milling by the high efficiency wet mill, the preliminary stage milling using a low or medium efficiency mill to improve the overall milling efficiency and polishing The particle size distribution, ie the particle size distribution, of the particles is narrow and uniform. That is, milling using two or more different mills having different efficiencies may be performed in succession, or several mills may be connected to each other. In such a milling process, the particle size distribution and the number of scratches are changed according to a combination of milling and dispersing apparatus or a change in the number of steps, which will be described later.

3. Dispersion Stabilization and Mixing of Additives

Next, as an example of the dispersant, anionic polymer dispersant is added to the slurry to stabilize the dispersion, and additives such as a weak acid and a weak base are added to adjust the pH to stabilize the slurry. The anionic polymer compound used as the dispersant may be any one selected from the group consisting of polymethacrylic acid, polyacrylic acid, ammonium polymethacrylate, ammonium polycarboxylate, and carboxyl-acrylic polymer or a combination thereof. Can be used. This is because, since the slurry of the present invention is water-based, it has an appropriate solubility in water at room temperature of such a polymer compound. At this time, the pH of the slurry is preferably 6.5 to 13. In addition, the addition range of the anionic polymer compound is preferably 0.0001 to 10.0 wt% based on the abrasive particles, preferably 0.001 to 3.0 wt%, more preferably 0.02 to 2.0 wt%. The viscosity behavior of the stabilized ceria slurry is preferably in Newtonian behavior.

At this time, the mixture mixed with the dispersant and the additive may be milled with a high-efficiency mill to reduce the particle size and proceed with dispersion. Thereafter, the pulverized and dispersed slurry may be transferred to a separate tank using a pump and then dispersed using an appropriate dispersing device to secure dispersion stability and prevent further aggregation and precipitation.

4. Solid load (wt%) control and large particle removal

After the dispersion stabilization process of the slurry is finished as described above, the solid load (wt%) of the ceria slurry is adjusted to a desired range, and filtering may remove large particles that may cause scratches during the CMP process and may cause precipitation and aggregation. do. The concentration of the solid load is preferably 15 wt% or less. The greater the presence of the larger particles, the greater the force due to gravity than the dispersion force due to the repulsive force between the particles, and the larger the particle area, the smaller the surface area of the microparticles. Lose. Due to these two causes, agglomeration and precipitation occur a lot and the slurry becomes unstable as a whole. Therefore, it is necessary to remove the large particles. Filtering to remove such large particles may increase the rate of large particle reduction as the number of filtering increases.

5. Slurry Aging

Next, the slurry is stabilized through aging. That is, it is effective to further stabilize the slurry by stirring the slurry in the tank and mixing for 24 hours. This can be done in addition to the finished slurry, and may be omitted if necessary.

[Changing Characteristics of Ceria Slurry with Milling Process]

Hereinafter, when manufacturing a ceria slurry using the manufacturing process as described above, the effect of the change in the method of operating a milling process, and the combination of a milling and a dispersing apparatus on the characteristic of a ceria abrasive grain is analyzed. In particular, the change in the size of the particle size distribution of the ceria slurry and the degree of change in the long tail according to the multi-step milling are classified and analyzed, and thus the change of the micro scratches is described in detail.

Polishing slurries can cause micro-scratches that have a fatal effect on semiconductor devices during the ultra-high density semiconductor manufacturing process of 0.13 μm or less depending on the amount of the large particles and the small amount thereof. In other words, the polishing mechanism of the ceria abrasive is a poly-crystal type ceria particle as shown in FIG. 2 is broken into a single crystal form as a chemical reaction with an oxide film deposited on the wafer and then the pad and It is a method of grinding by grinding away by mechanical frictional force. At this time, as the proportion of the macroparticles in the abrasive grains increases, the number of microparticles 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 is increased. Scratch can occur. Therefore, there is a need to minimize the proportion of large particles in ceria abrasive particles and to enhance dispersion stability. At this time, these large particles are concentrated in the portion corresponding to the long tail on the particle size distribution of the ceria slurry. And one of the important factors that can greatly affect the long tail (long tail) in the particle size distribution of the ceria slurry is the operation method and combination of milling and dispersing equipment in the manufacturing process of the ceria slurry.

Milling and dispersing machines have a limit value of the particle size that can be milled during milling, depending on the respective machine. In other words, as the large particles are milled, they are crushed or dispersed into fine particles, which are reduced in size. In fact, in FIG. 3, as the milling process is continued while increasing the number of millings (pass times) using the same wet mill, the particle size decreases rapidly in the region of 20 μm to 30 μm, but there is almost no change in the particle size near 100 nm. . In other words, near 100 nm is the limit value of such a wet milling machine.

Depending on the performance and characteristics of each mill, the limit values differ from mill to mill, and multiple pre-step milling is used before the high-efficiency wet mill is used for the main particle size control. The particle size distribution of the slurry can be obtained more narrowly. In the following the pre-step milling is carried out using milling machines having a relatively large limit on the size of particles that can be ground, that is, low and / or medium efficiency mills, and the limit on the size of particles that can be ground. Will be described for multi-step milling, where main-step milling is carried out using a relatively small mill, that is, a high efficiency wet mill. As shown in Fig. 4, the present invention performs preliminary step milling using a mill having a different efficiency from that used in the main step milling before the main step milling. That is, preliminary stage milling may be performed using a low-efficiency milling machine before the main stage milling as shown in FIG. 4 (a), and preliminary stage milling may be performed before the main stage milling as shown in FIG. 4 (b). Step milling may be performed, or preliminary step milling may be performed using a low efficiency mill and a medium efficiency mill before the main step milling as shown in FIG. In addition, preliminary mills can be used in various combinations with mills of other efficiencies and mills used in main milling. For example, preliminary step milling may be performed in the order of low efficiency mills, medium efficiency mills, and other medium efficiency mills, and preliminary step milling may be performed in the order of low efficiency mills and other low efficiency mills. It is also possible to adjust the number of times of milling using the same mill in each stage of milling in multiple times. For example, when preliminary milling is performed using a low efficiency mill, low efficiency milling may be performed once, and low efficiency milling may be performed two or more times. These are several examples of operating and combining mills with different efficiencies, and the operation and combination of mills can be utilized in various ways.

This preliminary step milling increases the milling efficiency, reduces the large particle size, and provides a narrow and uniform abrasive particle size distribution. Table 1 shows the particle size distribution of the abrasive grain in the case of making a slurry by making other slurry manufacturing conditions the same except milling conditions, and changing milling conditions. The particle size distribution comparison accordingly is shown in FIG. 5.

Milling conditions Particle size distribution max size-min size Without preliminary step milling (A) 1 ㎛ ~ 70 ㎛ 69 μm One low-efficiency milling operation (B) 0.8 μm to 40 μm 39.2 μm 2 times low efficiency milling 0.8 μm to 21 μm 20.2 μm When medium efficiency milling is performed once (D) 0.8 μm to 21 μm 20.2 μm Low and medium efficiency milling each time (E) 0.6 μm to 13 μm 12.4㎛

As shown in Table 1 and FIG. 5 above, all preliminary step milling using a low efficiency milling machine, a medium efficiency milling machine, or a mixture of the two is performed before main-step milling by high efficiency wet milling. In this case, it can be seen that the maximum size of the abrasive grains is remarkably reduced, and the particle size distribution is narrowed, as compared with the case of not performing the preliminary step milling (A). In addition, when milling twice with a low efficiency milling machine (C) or milling with a medium efficiency milling machine (D), rather than performing one milling with a low efficiency milling machine (B), ceria It can be seen that the particle size distribution of the slurry becomes narrower. In addition, when the first milling using a low efficiency milling machine followed by the second milling using a medium efficiency milling machine (E), the maximum size of the abrasive grains was reduced and the particle size distribution was narrower than those of these cases. Can be.

6 and Table 2 show the comparison of the particle size distribution after the main wet milling process in the case where the prepared abrasive particles and the slurry are subjected to pre-step milling and non-preparation.

Milling conditions Particle size distribution Max size-min size When wet milling without preliminary milling (A ') 0.09㎛ ~ 2.8㎛ 2.71 μm When wet milling after one time of low efficiency milling (B ') 0.09㎛ ~ 1.8㎛ 1.71 μm When wet milling after two low-efficiency mills (C ') 0.09㎛ ~ 1.2㎛ 1.11 μm When wet milling after one time of medium efficiency milling (D ') 0.09㎛ ~ 1.2㎛ 1.11 μm When wet milling after each low and medium efficiency milling process (E ') 0.08㎛ ~ 1.1㎛ 1.02 μm

In FIG. 6, pre-step milling is compared to slurry A 'which has undergone the main-step milling process by high efficiency wet milling without undergoing pre-step milling. It can be seen that the particle size distribution of the slurry in all cases through) is relatively narrow and the long tail is short. In addition, when preliminary milling with a low efficiency mill is performed once (B '), preliminary milling with a low efficiency mill is performed twice (C') or preliminary milling with a medium efficiency mill. In the case of (D '), a narrower and more uniform particle size distribution can be obtained. In addition, it can be seen that when the continuous milling process (E ') is performed once in each successive milling process using the low-efficiency mill and the medium-efficiency mill, the larger particles are reduced and the particle size distribution is narrower.

As such, the particle size distribution of the abrasive particles may be controlled by multi-step milling including preliminary step milling, which is closely related to the number of micro scratches. The narrower the particle size distribution and the shorter the long tail, the shorter the number of micro scratches. We will discuss this in more detail later in “Changing Micro Scratch with Changes in Milling Process”.

[Micro Scratch Variation According to Milling Process Variation]

Hereinafter, the ceria powder and the slurry are prepared under each condition by the slurry production method as described above, and the characteristics of the abrasive particles and the slurry properties prepared under the respective conditions will be described. The properties of these abrasive particles and slurry were measured, and then summarized in Table 3 below.

First, measuring equipment for various analysis is described first.

1) Particle size distribution: measured by LA-910 of Horiba, Japan

2) XRD: Measured by Philips' X'PERT Pro MRB

(1) Preparation of the First to Fifth Ceria Powders

25 kg of high purity cerium carbonate was put in a container (800g) about 800g each and calcined for 4 hours at 700 ℃ in a tunnel (tunnel kiln) to prepare a first ceria powder. In addition, the calcined at 700 ℃ for 4 hours in the same manner to prepare a second to 5 ceria powder. At this time, the temperature increase rate at the time of calcination was 5 ℃ / min, the cooling is natural cooling and 20 ㎥ / Hour gas was flowed in the direction opposite to the moving direction of the saggar to effectively remove the by-product CO ₂ gas. The calcined ceria powder was confirmed by X-ray diffraction to obtain high purity ceria (cerium oxide).

(2) Preparation of the First to Fifth Ceria Slurry

10 kg of the high purity first ceria powder synthesized under the above conditions was added to 90 kg of ultrapure water, in which ammonium polymethacrylate was mixed with 1 wt% of ceria powder as an anionic dispersant, for 1 hour for sufficient wetting in a high shear mixer. Mix over. Thereafter, the mixed 10 wt% slurry is milled using a high efficiency wet milling method. Milling adjusts the particle size to the desired range and also disperses the aggregated slurry. Subsequently, filtering removes the large particles to prepare a first ceria slurry.

In addition, 10 kg of the high purity second ceria powder synthesized under the conditions described above is pre-step milled using a dry mill, that is, a low efficiency mill. 10 kg of ceria powder after pre-step milling is used as anionic dispersant and 90 kg of ultrapure water mixed with 1 wt% of ammonium polymethacrylate relative to ceria powder and 1 hour for sufficient wetting in a high shear mixer. After the mixing, the mixed 10 wt% slurry is milled using a high efficiency wet milling method. Subsequently, a second ceria slurry is prepared by filtering.

The third ceria slurry is prepared in the same manner as the second ceria slurry using 10 kg of the high purity third ceria powder synthesized under the above conditions, but preliminary milling using a low efficiency mill is performed twice. In other words, using ceria powder, first pre-step milling is performed using a low efficiency dry mill, and then second pre-step milling is performed using a low efficiency dry mill. milling).

In addition, a fourth ceria slurry was prepared in the same manner as the second ceria slurry using 10 kg of the high purity fourth ceria powder synthesized under the above conditions, but preliminary milling using a medium efficiency milling machine was performed once. In addition, a fifth ceria slurry was prepared by the same method as the third ceria slurry using 10 kg of the high purity fifth ceria powder synthesized under the same conditions as above, but the first preliminary step milling was performed using a low efficiency mill to continuously The second preliminary step milling is carried out using an efficiency mill. That is, first pre-step milling using low efficiency dry milling machine, and then second pre-step milling using medium efficiency wet milling machine continuously do.

The slurry subjected to each preliminary step milling is milled using a high efficiency wet milling method, and filtered to prepare third to fifth ceria slurries.

(3) Comparison of the first to fifth ceria slurry and the CMP test results

Hereinafter, using the ceria slurry prepared as described above, the polishing agent is polished, and the polishing rate, the number of scratches, the polishing selectivity, and the like are examined, and the respective slurries are compared. The CMP polishing performance test was performed on the abrasive using the first to fifth ceria slurry prepared as described above. The CMP polishing machine used 6EC from the US company Strasbaugh, and the target wafer was coated with plasma enhanced chemical vapor deposition TEOS oxide (PE-TEOS) to form an oxide film on the entire 8-inch wafer, and Si ₃ N ₄ was applied to the wafer on which the nitride film was formed on the entire 8-inch wafer, and test conditions and consumables were as follows.

1) Pad: IC1000 / SUBAIV (Rodel, USA)

2) Film thickness meter: Nano-Spec 180 (manufactured by US Nano-metrics)

3) table speed: 70 rpm

4) Spindle speed: 70 rpm

5) down force: 4 psi

6) Back pressure: 0 psi

7) Slurry feed amount: 100 ml / min

8) Residual Particles and Scratch Measurement: Measured by Surfscan SP1 from KLA-Tencor, USA

As described above, after polishing the entire surface of the wafer on which the oxide film (PE-TEOS) and the nitride film (Si ₃ N ₄ ) were formed with the first to fifth slurries prepared under the respective conditions, the polishing rate was changed from the thickness change removed by polishing. The micro-scratches were measured using Sufken's SP1. The polishing performance for each slurry was averaged after the polishing was performed three or more times on the blank wafer prepared as described above.

division Particle size distribution before the main milling process Particle size distribution after the main milling process Oxide Polishing Rate (Å / min) Nitride Film Polishing Rate (Å / min) Oxide: Nitride Polishing Ratio (Selective Ratio) WIWNU (%) Oxide Residual Particles (> 0.20㎛, #) scratch(#) First slurry 1 ㎛ ~ 70 ㎛ 0.09㎛ ~ 2.8㎛ 2673 51 52.4 1.0 810 6 2nd slurry 0.8 μm to 40 μm 0.09㎛ ~ 1.8㎛ 2562 50 51.2 1.0 129 2 Third slurry 0.8 μm to 21 μm 0.09㎛ ~ 1.2㎛ 2453 50 48.5 1.0 65 0 Fourth slurry 0.8 μm to 21 μm 0.09㎛ ~ 1.2㎛ 2501 50 50.0 1.0 80 0 5th slurry 0.6 μm to 13 μm 0.08㎛ ~ 1.1㎛ 2400 50 49.8 1.0 55 0

As described above, the same CMP conditions using the first to fifth slurries prepared by varying the particle size distribution of the slurry by adjusting pre-step milling conditions through multi-step milling In the CMP test, the results are shown in Table 3. First, the abrasive grain size before main stage milling of the first slurry without preliminary milling is distributed between 1 μm and 70 μm, whereas the abrasive grain size before main stage milling of the second slurry is between 0.8 μm and 40 μm. Distributed in the range. In addition, it can be seen that the particle size distribution before the main stage milling of the third to fourth slurries is 0.8 μm to 21 μm, and the particle size distribution of the fifth slurry is 0.6 μm to 13 μm. As such, the present invention can control the particle size distribution of the ceria slurry before the main step milling to 50 μm or less through multi-step milling including a pre-step milling process.

Further, the first to fifth slurries are all usable in terms of polishing rate and polishing selectivity (polishing ratio of oxide film to nitride film), and also have excellent in-plane nonuniformity (WIWNU) which shows polishing in-plane polishing uniformity during polishing. However, when the preliminary milling is not performed (first slurry), it can be seen that the number of micro scratches and the number of oxide film residual particles are considerably higher than when the preliminary milling is performed (second slurry to fifth slurry). . This preliminary milling reduces the particle size distribution of the abrasive grains before the high-efficiency wet milling process and reduces the long tail to reduce the number of micro scratches and oxide particles.

As described above, according to the present invention, it is possible to prepare a slurry having excellent physical properties with respect to various properties that are essential for polishing the STI CMP process in semiconductor manufacturing, and in particular, may cause a fatal defect in a device after CMP. Micro scratches and residual particles can be reduced.

According to the present invention, it is also possible to control the particle size distribution before the main stage milling of the abrasive particles to control the large particle ratio to reduce the maximum size of the abrasive particles in the final slurry (remove the long tail) and narrow the particle size distribution. The slurry of the present invention having such an excellent particle size distribution can maintain a high polishing rate while at the same time reducing the micro scratches that can cause device defects in the CMP process.

In addition, according to the present invention, it is possible to prepare a slurry having excellent physical properties for the various properties that must be essentially provided as an abrasive for STI CMP, when using the slurry as an abrasive for STI CMP, ultra-high integration semiconductor process while minimizing micro scratch Various patterns can be polished as required.

Claims (12)

In the polishing slurry comprising abrasive particles, The abrasive particles are subjected to at least two stages of milling using a mill having a different limit value of the particle size that can be crushed, and the polishing slurry has a particle size of 50 μm or less before the final stage milling. The polishing slurry according to claim 1, wherein the mill is at least one of a low efficiency mill for crushing large particles, a medium efficiency mill and a high efficiency mill for crushing small particles into fine particles. The polishing slurry according to claim 1 or 2, wherein the polishing particles have a particle size in the range of 0.5 µm to 40 µm before the final step milling. The polishing slurry according to claim 1 or 2, wherein the polishing particles have a particle size in the range of 0.6 µm to 30 µm before the final step milling. The polishing slurry of claim 1 or 2, wherein the abrasive particles comprise ceria. Preparing abrasive particles; Performing preliminary milling so that the particle size of the abrasive particles is in the range of 50 μm or less; And The preliminary step milling and the method for producing a polishing slurry comprising the step of performing the main stage milling using a mill having a different limit value of the particle size that can be ground. 7. The method of claim 6, wherein the performing of the main step milling comprises milling using a high efficiency mill that grinds small particles into fine particles. 8. The method of claim 7, wherein the preliminary step milling comprises milling at least one or more times using a low efficiency mill or a medium efficiency mill that grinds large particles. 8. The polishing slurry of claim 7, wherein the preliminary step milling comprises milling at least one or more times with a low efficiency mill that grinds large particles, and then milling at least one or more times with a medium efficiency mill. Way. 10. The method of any one of claims 7 to 9, wherein the high efficiency mill comprises a wet bead mill. 10. The method of claim 8 or 9, wherein the medium efficiency mill comprises a ball mill or bead mill that can be used by adjusting the size of the ball and beads to a few millimeters. 10. The method of claim 8 or 9, wherein the low efficiency mill comprises a dry mill or a ball mill.

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