KR100584007B1 - Slurry for polishing and method of manufacturing the same - 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, Dispersant, pH, Surface Area, Aggregation, Dispersion Stability

Description

Slurry for polishing and method of manufacturing the same

1 is a process flow diagram of typical slurry production.

2 is a schematic view showing a polishing mechanism of ceria abrasive.

3 is a conceptual diagram of D15, D50, and D85.

4 is a graph showing a change in dispersion stability according to the dosage of the dispersant.

5 is a graph showing the change in dispersion stability according to the dosage of the pH and dispersant.

6 is a conceptual diagram showing the degree of adsorption of the dispersant according to the pH change.

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 essentially applied to the ultra-high-density semiconductor manufacturing process of 256 megaramm or more (design rule of 0.13㎛ or less), has a high level of nitride layer used as a barrier layer in the CMP process. The present invention relates to a slurry having a polishing selectivity and capable of suppressing the occurrence of scratches on a planarized surface and a method of polishing a substrate using 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 simultaneously performed. Since it was developed by IBM in the late 1980s, it has become an essential process for global planarization technology in the manufacture of submicron-scale semiconductor chips.

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. The oxide slurry is a slurry used to polish an interlayer insulating film and a silicon oxide layer (SiO ₂ layer) used in a shallow trench isolation (STI) process, and is mainly composed of abrasive particles, deionized water, a pH stabilizer, and a surfactant. It is composed. Among these, the abrasive particles act to mechanically polish the surface under pressure from the 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 removal rate selection rate of the oxide layer relative to the nitride layer, but in this case, not only the nitride layer removal rate but also the oxide layer removal rate is decreased, thereby substantially improving the selection ratio. It doesn't work. In addition, since the abrasive particles of the ceria slurry are usually larger than the abrasive particles of the silica slurry, 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 occurs in which an oxide layer is excessively removed due to the loss of the adjacent nitride layer pattern, thereby preventing 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 and uniform proper particle size distribution and a size of 1 μm or more are constant. It must be within the limits.

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. In particular, the change in grain size according to the calcination temperature and the resulting scratch (Scratch) is mentioned. 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. Hitachi, U.S. Patent No. 6,615,499, mentions the ratio of the peak intensity (Peak Intensity) of a specific region on the X-ray and the change of the polishing rate according to the heating rate in the calcination process .

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 describes only the average particle size and the range of the abrasive particles constituting the polishing slurry and lacks detailed consideration of how to disperse these particles. Dispersion of the slurry is very important especially considering the micro scratches that can be caused by the large particles produced due to the aggregation of the slurry. However, in the case of the existing patent, although the type of dispersant and the dispersing device are mentioned, specific considerations about the dispersant added for dispersing are insufficient.

Incomplete dispersion may occur depending on the amount of the dispersant, and agglomeration of the slurry may occur due to bridging by an excessive amount of the dispersant. Considering the fact that the amount of such dispersant is not determined by one absolute value and the optimum value is changed by the surface area of the particles and the pH of the slurry, the surface area as a method for minimizing micro scratches and device defects due to dispersion of the slurry is minimized. It is very important to identify the optimum value of the amount of dispersant added under various conditions of various variables including pH.

Therefore, in order to solve the above problems, the present invention provides a method of pretreatment and apparatus for dispersing various particles, dispersing equipment and its operating method, method and amount of chemical additive addition, transporting device for sample, etc. 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 a highly integrated semiconductor manufacturing process and can minimize fatal micro scratches in a semiconductor device.

The present invention focuses on the fact that incomplete dispersion occurs depending on the amount of the dispersant, and that agglomeration of the slurry may occur due to bridging by an excessive amount of the dispersant. Provide a review of the optimal dosage. In particular, the optimum amount of dispersant is changed by various conditions of the slurry, which are representative examples, such as the pH of the slurry.

That is, the present invention is to consider the optimum dispersant input amount according to the pH change, and to provide a dispersion stabilized slurry, which can obtain an appropriate polishing rate while minimizing micro scratches.

In order to achieve the above object, the present invention comprises the steps of preparing abrasive particles, ultrapure water and dispersant, milling the mixture of abrasive particles and ultrapure water, measuring the pH of the mixture, the dosage of the dispersant according to the pH It provides a method for producing a polishing slurry comprising the step of determining and milling by adding the dispersant to the mixture of the abrasive particles and ultrapure water.

Determining the input amount of the dispersant, when the pH of the mixture is 8.7 to 9.5 determines the input amount of the dispersant to 2.2 to 3.0wt% relative to the abrasive particles, and when the pH of the mixture is 8.0 to 8.7 The dosage is determined to be 1.4 to 2.2 wt% based on the abrasive particles, and when the pH of the mixture is 7.4 to 8.0, the dosage of the dispersant is determined to be 0.6 to 1.4 wt% based on the abrasive particles.

The abrasive particles are characterized in that they comprise ceria.

The present invention provides a polishing slurry, characterized in that prepared according to the above description. It is preferable that the conductivity of the polishing slurry is 300 to 900 kW / cm, and more preferably, the conductivity of the polishing slurry is 550 to 600 kW / cm.

Hereinafter, each part will be described in detail by dividing the manufacturing process of the polishing slurry of the present invention and the characteristics of the polishing slurry produced as a result. In addition, 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 thereof. The CMP results such as oxide polishing rate and selectivity according to the slurry production method and process conditions 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, ultra pure water (DI Water) and anionic polymer dispersant, a weak acid or a weak base. A general method for preparing such polishing ceria slurry is 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) and 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 further stabilized dispersion through additional milling (S5), to adjust the weight ratio of the slurry (wt%), that is, the solid load to the desired range (S6). Then, the macroparticles are removed through filtering to prevent scratches during precipitation and polishing (S7), and further aging to 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 is synthesized, for example, by calcining a precursor such as cerium carbonate, and may be subjected to a separate drying process to remove moisture adsorbed before full calcining. This is because the precursors treated through the drying process are excellent in terms of ease of transfer and treatment in the process.

The ceria powder varies in characteristics depending on the conditions for calcining cerium carbonate and the configuration of the calcining apparatus. The bulk density of cerium carbonate is preferably 0.7 or less and the tapping density is 1.2 or less. 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.

Here, the degree of crystallization (Crystallinity) and grain size may vary depending on the calcination temperature. The higher the calcination temperature, the larger the grain size or the size of one crystal. In addition, the porosity and the crystallinity vary according to the holding time and the loading amount of the saggar in the maximum temperature range of the calcination process.

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.

In order to control the particle size and to disperse the aggregated abrasive particles after the mixing and wet process, it is effective to reduce the particle size and disperse using a high energy milling machine. In addition, the mill may use a wet or dry mill. Dry mills are preferably milled using wet mills made of ceramic material, because metal milling is a concern due to wear of the metal parts during the milling process. 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, dispersion using a dispersant Enhancing stability is effective. In this embodiment, it is effective to carry out at least three times using a pass milling.

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 the slurry of the present invention is water-based, so that the polymer compound has an appropriate solubility in water at room temperature. 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. The viscosity behavior of the stabilized ceria slurry is preferably Newtonian behavior.

The mixture mixed with the dispersant and the additive may be milled with a high energy mill to reduce particle size and to 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 equipment to secure dispersion stability and prevent further aggregation and precipitation.

 By controlling the dispersion stability of the ceria slurry, it is possible to easily obtain a slurry property that can minimize the micro scratch while maintaining a high polishing rate and selectivity.

According to the present invention, by adding an appropriate amount of dispersant according to the pH of the slurry, it is possible to obtain a slurry capable of increasing dispersion stability and minimizing micro scratch while maintaining high polishing rate and selectivity, which will be described later.

4. Adjusting solid load (wt%) and removing large particles

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 removes large particles that may cause scratches during the CMP process and may cause precipitation and aggregation. . The concentration of the solid load is preferably 15 wt% or less. It is also most preferred that the concentration of the solid load is in the range of 3 to 10 wt%. 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 particles, and the smaller the surface area of the larger particles compared to that of the finer particles, the smaller the dispersion rate of the larger particles. . 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 can increase the rate of large particle reduction further by increasing the number of filtering.

5. Slurry Aging

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

[Change of Dispersion Stability According to Amount of Dispersant]

In the following, the effect of the amount of dispersant on the dispersion stability of the ceria slurry in the case of preparing the ceria slurry using the manufacturing process as described above is analyzed. In particular, changes in optimal dispersant dosage, changes in dispersion stability, and resulting microscratches with pH change are described in detail.

The polishing slurry may cause micro scratches that have a fatal effect on the semiconductor device during the ultra-high density semiconductor manufacturing process of 0.13 μm or less depending on the aggregation of the abrasive particles. In other words, the polishing mechanism of the ceria abrasive is a mechanical device with a pad after chemical reaction with an oxide film deposited on a wafer while poly-crystal-like ceria particles are broken into single crystals as shown in FIG. 2. It is a method of grinding away by the frictional force. At this time, as the agglomeration of the abrasive grains increases, a large number of micro scratches occur in the process of crushing the polycrystal into a single crystal, and in the process of the agglomerated secondary particles into smaller secondary or primary particles. May occur. Therefore, it is necessary to minimize the aggregation of the abrasive particles and to enhance the dispersion stability. At this time, one of the important factors that can greatly affect the dispersion stability of the abrasive particles is the amount of dispersant added to the ceria slurry.

First, dD1, dD15 and dD50 can be used as a good standard for measuring the degree of aggregation of the slurry. That is, particle size can be measured by using LA910 of Horiba, Japan, and can be obtained by using the result. Each definition is as follows.

dD1 = D1 without sonication-D1 with sonication

dD15 = D15 without sonication-D15 with sonication

dD50 = D50 without sonication-D50 with sonication

However, each term is defined as follows.

D1 without sonication, D15 without sonication, D50 without sonication

: D1, D15, D50 particle size measured with the ultrasonic off

D1 with sonication, D15 with sonication, D50 with sonication

: Particle size of D1, D15, D50 measured with ultrasound on

3 is a conceptual diagram for explaining the definition of D50 according to the particle size.

As shown in FIG. 3, D50 is a medium size and corresponds to a value of 50% of the total size distribution, and a D15 value corresponds to 15% from a large size. In addition, the value of D1 is similarly 1% from the large size. That is, the value of D1 is the number indicating the size of the secondary particles, and the larger the aggregation, the poorer the dispersion stability, the larger the value of D1, and accordingly the dD1 value becomes larger.

When measuring the particle size using Horiba's LA910 model, when the ultrasonic wave is turned on and measured, the aggregated slurry can be redispersed and the dispersed particle size can be measured. The slurries that have not been redispersed can measure the particle size of the aggregated slurry. Therefore, the degree of aggregation of the slurry can be known by comparing the particle size before and after the forced dispersion using ultrasonic waves. In this case, the more agglomerates and the lower the dispersion stability, the greater the value of dD1, dD15 and dD50.

Table 1 below measured the values of dD1, dD15 and dD50 of the polishing slurry prepared by varying the amount of dispersant to determine the degree of aggregation according to the amount of dispersant. That is, sample 1 was added a dispersant of 3.82wt%, sample 2 was added a 2.5wt% dispersant, sample 3 was added a 1.6wt% dispersant. The pH of each polishing slurry was 9.1, and other conditions other than the dispersant loading were made the same.

Figure 4 is a graph showing the results shown in Table 1, showing the value of dD1, dD15 or dD50 according to the dispersant input amount.

Here, sample 1 can be seen that the amount of the dispersant is relatively agglomerated much without the effective dispersing effect. This is due to the bridging action of the polymer dispersant because the amount of dispersant is too large, rather the particles aggregate together. On the other hand, sample 3 shows that the amount of dispersant is too small to cause sufficient dispersing effect, resulting in agglomeration. Since dispersion stability does not increase in proportion to the amount of dispersant, an appropriate amount of dispersant should be added according to various conditions such as pH and surface area.

In the case of sample 2, it is possible to minimize the aggregation and stabilized dispersion stability by adding the appropriate amount of dispersant.

The optimal dosage of dispersant can be determined based on the conductivity. The higher the conductivity, the more residual dispersant in the bulk solution, which means that a much larger amount of dispersant has entered than the optimum dose. In other words, when the conductivity is too high, a large amount of dispersant may be added, which may cause aggregation of particles due to bridging of the excess dispersant. Therefore, the dosage of the dispersant may be adjusted based on the conductivity.

In the present invention, the conductivity is preferably 300 to 900 mW / cm. More preferably, the conductivity is 550 to 600 mW / cm. In this case, increasing the dispersant input increases the conductivity, and decreasing the dispersant input decreases the conductivity.

As shown in Table 1 and FIG. 4, when the amount of the dispersant is too small, the conductivity is very low, and there is not sufficient dispersion, thereby increasing the aggregation. On the other hand, when the amount of the dispersant is too large, the conductivity is very high, and the crosslinking of the polymer ( Due to the bridging action, there is a lot of aggregation. Therefore, it is important to add an appropriate amount of dispersant, which is determined in consideration of various conditions such as pH.

Table 2 below was to determine the degree of aggregation according to the pH and to measure the value of dD1, dD15 and dD50 of the polishing slurry prepared by changing the pH and the amount of dispersant in order to control the dispersant input. That is, sample 2 had a pH of 9.1 of the slurry, sample 4 had a pH of 8.4 of the slurry, and the polishing slurry was charged with the same amount of dispersant of 2.5 wt%. In addition, sample 5 has a pH of 8.4 and a dispersant of 1.71 wt% was added thereto. The other conditions of each polishing slurry were the same.

5 is a graph showing the results shown in Table 2, showing the value of dD1, dD15 or dD50 according to the pH and dispersant dosage.

Here, sample 2 minimized the aggregation level by appropriately adding dispersant according to pH. On the other hand, sample 4 is lower than the pH of sample 2, but by adding the same amount of dispersant, it can be seen that the conductivity is sharply increased and the aggregation is significantly increased. This is due to the difference in the degree of adsorption of the dispersant according to the pH as shown in FIG. Referring to the drawings, when the pH is 3, the particle interface has a positive (+) potential, and the anionic polymer dispersant has a strong adsorption force on the particle interface in the form of twisted chains. As the pH increases, the particle interface has a negative (-) potential, which lowers the surface adsorption of the anionic dispersant and the twisted chain form of the polymer begins to unwind. When the pH is as high as 10, the particle interface is almost negative (-) potential, the anionic polymer dispersant is expanded with a repulsive force on the particles, it can be easily stabilized by the force between the strong ions in the aqueous solution.

As the pH is lowered as described above, the adsorption force of the anionic polymer dispersant on the particle interface becomes stronger. Therefore, excessive bridging occurs due to the strong adsorption of the dispersant, which causes the particles to aggregate rapidly.

That is, when comparing sample 2 and sample 4, the pH is lowered and the adsorption power of the dispersant to the particles is increased, so that the conductivity is very high and a lot of aggregation can be seen. Therefore, when the pH of the polishing slurry is low, the amount of dispersant should be reduced.

Sample 5 has a pH of 8.4 and the amount of dispersant is adjusted in the same manner as in Sample 4. That is, sample 4 was added 2.5 wt% of the dispersant, sample 5 was added less than 1.71wt% of the dispersant. In this way, if the input amount of dispersant is lowered while maintaining the pH at 8.4, the conductivity decreases, and the increase in adsorption amount due to the decrease in pH is offset by the decrease in input amount, so that the degree of aggregation is very small and stable dispersion stability can be obtained. It can be seen that.

In adjusting the amount of the dispersant as described above, it is important to add an appropriate amount in consideration of the pH of the slurry. The amount of this dispersant is based on conductivity as described above, which is very good in dispersion stability when it is 550-600 cc / cm.

In addition, the amount of the dispersant is 2.2 to 3.0wt% relative to the abrasive particles when the pH of the slurry is 8.7 to 9.5, 1.4 to 2.2wt% relative to the abrasive particles when the pH of the slurry is 8.0 to 8.7, the pH of the slurry is In the case of 7.4 to 8.0, the amount is preferably 0.6 to 1.4 wt% based on the abrasive grains.

[Change of Micro Scratch According to Change of Dispersant]

In the following, the ceria powder and the slurry are prepared under each condition using the slurry production method as described above, and the characteristics of the abrasive particles and the slurry properties such as particle size and number of large particles of the slurry prepared under each condition will be described.

First, measuring equipment for various analysis is described first.

1) pH & Conductivity: Measured by pH and conductivity meter of Orion, USA

2) Particle size: measured by Philips' X'PERT Pro MRB

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

4) Transmission electron microscope (TEM): measured by JEM-2010 of JEOL, Japan

(1) Preparation of the first to fifth ceria powder

25 kg of high-purity cerium carbonate was placed in a container about 800 g each and calcined for 4 hours at 800 ° C. in a tunnel kiln to prepare first to fifth ceria powder. However, the heating rate of each calcining is 5 ℃ / min, cooling is natural cooling and 20m ³ / in the direction opposite to the direction of movement of the saggar to effectively remove the CO ₂ gas produced by by-product (by-product) The gas of Hour flowed. The calcined ceria (cerium oxide) powder was confirmed by X-ray diffraction, and each obtained high purity ceria.

(2) Preparation of the First to Fifth Ceria Slurry

10 kg of the high purity first ceria powder synthesized under the above conditions and 90 kg of ultrapure water are mixed in a high shear mixer for at least 1 hour for sufficient wetness, and then the mixed 10 wt% slurry is milled using a pass milling method. . Milling adjusts the particle size to the desired range and also disperses the aggregated slurry. Next, ammonium polymethacrylate is added as an additional anionic dispersant to 3.82 wt% of ceria powder, and the mixture is dispersed by mixing for 2 hours or more in consideration of their adsorption, followed by filtering to prepare a ceria slurry. The second and third ceria slurries are prepared in the same manner as the first ceria slurry, but the dosage of dispersant is changed to 2.5 wt% and 1.6 wt%, respectively. The first to third ceria slurries titrate the pH to 9.1. The fourth ceria slurry is prepared in the same manner as the second ceria slurry, but the pH is adjusted to 8.4 using acetic acid. In addition, the fifth ceria slurry was prepared in the same manner as the fourth ceria slurry, but the amount of dispersant was adjusted to 1.71 wt%.

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

In the following, the abrasive is polished using the ceria slurry prepared as described above, and the polishing rate, the number of scratches, the polishing selectivity, and the like are examined, and each slurry is 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 of the American 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 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 Nano-metrics, USA)

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 Measurements: Measured by Surfscan SP1 from KLA-Tencor, USA

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 ceria slurries prepared under the above conditions for 1 minute, the polishing was performed from the thickness change removed by polishing. Velocity was measured and micro-scratches were measured using Sufskken SP1. In particular, before the CMP test, in order to clearly see the difference in dispersion stability and aggregation degree due to the difference in surface area, the slurry and the DI water are mixed without special redispersion after aging for at least one month. Mixing) to proceed with the test. The polishing performance of each slurry was performed three or more times on the blank wafer prepared as described above, and then the polishing property results were measured.

The pH, conductivity, dD50, dD15, and dD1 values for each slurry are shown in Table 1 or Table 2 above. That is, the first ceria slurry is prepared sample 1, the second ceria slurry is prepared sample 2, the third ceria slurry is prepared sample 3, the fourth ceria slurry is prepared sample 4, The fifth slurry prepared Sample 5.

As described above, the CMP test under the same CMP conditions using the first to fifth slurries prepared by varying the amount of dispersant introduced into the ceria slurry by adjusting the pH is as shown in Table 3 above. First, it can be seen that the first to fifth slurries all have usable ranges in terms of polishing rate and polishing selectivity (oxide to nitride film polishing ratio), and also exhibit excellent in-plane nonuniformity (WIWNU) indicating polishing uniformity in polishing. have. However, it can be seen that the degree of agglomeration or dispersion of the abrasive particles changes according to the amount of the dispersant added and the number of microscratches changes. That is, it can be seen that the first slurry has a large amount of dispersant and thus agglomerates a lot, and the third slurry has a small amount of dispersant. In addition, the fourth slurry did not properly adjust the dosage of the dispersant as the pH was lowered, leading to agglomeration of particles due to the overdosing of the dispersant, which caused a significant amount of micro scratches.

As described above, the slurry is agglomerated as the amount of dispersant added is less than the optimum value, so that the dispersing efficiency is low and the condensation effect such as bridging may occur due to the addition of too much dispersant. Therefore, an appropriate amount of dispersant should be added in consideration of the pH of the slurry.

The proper dosage of this dispersant should be lower the lower the pH of the slurry. The proper dosage of the dispersant is 2.2 to 3.0 wt% relative to the abrasive particles when the pH of the slurry is 8.7 to 9.5, 1.4 to 2.2 wt% relative to the abrasive particles when the pH of the slurry is 8.0 to 8.7, and the pH of the slurry is In the case of 7.4 to 8.0, the amount is preferably 0.6 to 1.4 wt% based on the abrasive grains.

The most suitable amount of dispersant is when the conductivity is 300 to 900 kW / cm, more preferably when the conductivity is 550 to 600 kW / cm.

According to the present invention, it is possible to easily obtain a slurry property that can minimize the micro scratch while maintaining a high polishing rate and selectivity by controlling the dispersion stability of the ceria slurry by changing the input amount of the dispersant to a given pH conditions.

As described above, the present invention enables the production of a slurry having excellent physical properties with respect to various properties that must be essential as an abrasive for STI CMP process in semiconductor manufacturing, and in particular, scratches that can cause fatal defects in the device after CMP. And residual particles can be reduced.

In addition, according to the present invention, by adjusting the amount of the dispersant added to the slurry, it is possible to develop a slurry that can maintain a high polishing rate while reducing 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 with respect to various properties that must be essentially provided as an abrasive for STI CMP, and when such a slurry is used as an abrasive for STI CMP, Excellent results can be achieved for the application and corresponding polishing rate, polishing selectivity, in-plane nonuniformity (WIWNU) indicating polishing uniformity, and micro-scratch minimization.

Claims (8)

Preparing abrasive particles, ultrapure water and a dispersant; Milling the mixture of abrasive particles and ultrapure water; Measuring the pH of the mixture; Determining the dosage of the dispersant according to the pH; And Method for producing a polishing slurry comprising the step of milling the dispersant in the mixture of the abrasive particles and ultrapure water. The method according to claim 1, Determining the input amount of the dispersant, When the pH of the mixture is 8.7 to 9.5, the amount of dispersant is determined to 2.2 to 3.0wt% of the polishing slurry, characterized in that for producing a polishing slurry. The method according to claim 1, Determining the input amount of the dispersant, When the pH of the mixture is 8.0 to 8.7, the amount of dispersant is determined to 1.4 to 2.2wt% of the polishing particles, characterized in that for producing a polishing slurry. The method according to claim 1, Determining the input amount of the dispersant, When the pH of the mixture is 7.4 to 8.0, the input amount of the dispersant is determined to 0.6 to 1.4wt% relative to the abrasive particles, characterized in that for producing a polishing slurry. The method according to claim 1, The abrasive particle is a manufacturing method of the slurry for polishing, characterized in that it comprises ceria. Polishing slurry prepared according to any one of claims 1 to 5. The method according to claim 6, A polishing slurry having a conductivity of 300 to 900 kW / cm of the polishing slurry. The method according to claim 6, A polishing slurry having a conductivity of 550 to 600 Pa / cm of the polishing slurry.

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