KR100588404B1 - Ceria slurry for polishing semiconductor thin layer - Google Patents

Abstract

The present invention relates to an aqueous cerium oxide slurry for polishing a semiconductor thin film. According to the present invention, a cerium oxide slurry for polishing a semiconductor thin film having a weight change of 20% or less in a slurry concentration reduction (CSL) test by centrifugation has excellent long-term stability. In addition, the polishing productivity is excellent during the planarization of the semiconductor wafer, and scratches are not generated on the polished film.

Description

Cerium oxide slurry for semiconductor thin film polishing {CERIA SLURRY FOR POLISHING SEMICONDUCTOR THIN LAYER}

The present invention relates to a cerium oxide slurry for polishing a semiconductor thin film, and more particularly, to a cerium oxide slurry having a high polishing rate and excellent scratch characteristics with a weight change of 20% or less in a slurry concentration test by centrifugation.

In the chemical mechanical polishing (CMP) application of semiconductors, cerium oxide is mainly dispersed in an aqueous suspension and then used in slurry. Until now, the main purpose of the cerium oxide slurry has been to show a large amount of polishing. However, in recent years, as the wiring of semiconductor processes is gradually miniaturized and the spacing between chips is reduced, a small number of scratches in addition to the amount of polishing and the size of the generated scratches are required.

The cerium oxide used in the conventional chemical mechanical slurry has a high density, which causes most particles to sink when stored for a long time, and when redispersed, the particles aggregate and cause scratches. Therefore, many efforts have been made to prepare a slurry having dispersion stability, and the dispersion stability has been substantially improved by applying a surfactant to abrasive particles and developing a disperser.

In recent years, it has been found that defects after polishing are mainly caused by scratches, in particular, large particles present in trace amounts in the slurry. As an effort to reduce such scratches, Japanese Patent Laid-Open Publication No. 2003-171653 manages the particle size of the aggregated particles to 3 microns or less, but in addition, in the fine pattern of 0.16 μm or less, the yield is significantly reduced by scratching. Will occur. This is because the particles causing scratches on the actual wafer surface are particles of 700 nm or more, particularly 1 μm or more.

In addition, in recent years, the reduction of line width has been promoted in semiconductor manufacturing, and the number of chips produced on a single wafer has been increased, and when the conventional slurry is used as it is in a semiconductor chip manufacturing process with a reduced pattern, Scratches also act as lethality, limiting the yield. Moreover, since the number of chemical mechanical polishing processes is gradually applied to the semiconductor manufacturing process, the presence and size of scratches after such polishing process are closely related to the yield of chips in the wafer.

Therefore, the removal of large particles directly related to the occurrence of scratches is a more important technique, if the average particle size of the slurry is reduced for such scratches, there is a problem that the production amount decreases due to the decrease in the amount of polishing. For example, Japanese Patent Laid-Open Publication No. 2003-188122 regulates the amount of abrasive particles of 0.56 μm or more in order to reduce scratches, but the slurry actually used has an average particle diameter of 30 to 88 nm, which is too small. Problems can also occur in the flatness of the wafer, and the effectiveness thereof is low.

Accordingly, an object of the present invention is to provide a cerium oxide slurry which can minimize the defect rate due to scratches by reducing the scratches as well as reducing the scratches by effectively removing large particles without reducing the polishing amount.

In order to achieve the above object, the present invention provides a cerium oxide slurry for polishing a semiconductor thin film comprising a cerium oxide powder having an average particle diameter in the range of 0.1 to 0.2 ㎛ and satisfies the following equation:

(C ₀ -C ₁ ) / C ₀ X 100 ≤20

C ₀ is the solids concentration of the original slurry,

C ₁ is the solid content concentration after centrifugation for 2 minutes under the condition that the average centrifugal force g of the slurry is 1970 g ₀ , and g ₀ is the acceleration of gravity (9.8 m / sec ² ).

Hereinafter, the present invention will be described in detail.

Slurry of the present invention, characterized in that the weight change is 20% or less during centrifugation under certain conditions, satisfying the above Equation 1, the average particle size (mean volume size) measured by a laser scattering particle size distribution analyzer ) Ranges from 0.1 to 0.2 μm, and D ₁₀₀ (particle diameter at which the cumulative distribution value becomes 100 as measured by a particle size distribution) ranges from about 0.5 to 0.7 μm.

Cerium oxide slurries, which have been passed through conventional dispersion processes such as counter-colliders or sonicators, or have undergone wet milling, disperse evenly into the water, with most of the particles splitting from tens of microns to hundreds of nanosizes. The slurry dispersed through the disperser was used as it was, or a filter was used to filter large particles that were not split. However, as the width of the semiconductor wiring became 0.16 µm or less, the scratch was the biggest cause of lowering the semiconductor wafer yield, and this direct cause was found to be the presence of large particles of 0.7 µm or more. However, in the case of the conventional slurry, the average particle diameter of the particle size distribution of the cerium oxide slurry was around 350 nm, and small particles of 1 μm or more existed, and these large particles contained a large number of scratches on the thin film in the CMP process even though the amount of the particles in the slurry was extremely small. The size and depth of scratches generated are large, which can have a fatal effect on yield. However, the slurry according to the present invention, which satisfies the above conditions, has a small amount of solids that sinks to the bottom of the container even when stored for a long period of time, thereby preventing agglomeration between the cerium oxide particles, thereby greatly improving stability, and thus, using it after long-term storage. Even if the scratch count does not increase.

The cerium oxide slurry according to the present invention can be obtained by centrifugation and optionally further filtering process of the slurry obtained by dispersing the cerium oxide powder in water.

Specifically, the cerium oxide powder used for producing the cerium oxide slurry according to the present invention is not particularly limited in its production method, and may be produced by conventional methods. For example, raw materials, such as cerium carbonate, cerium hydroxide, cerium nitrate, cerium chloride, and cerium acetate, are calcined at 650 to 900 ° C. to oxidize to obtain cerium oxide, and then wet mill, dry mill, and the like. It can be obtained by grinding using, and may have an average size in the range of 10 to 100 nm. The firing process and the milling process may be performed in reverse order.

The cerium oxide powder thus prepared is dispersed in water, and the concentration of cerium oxide to facilitate dispersion is preferably in the range of 0.5 to 20% by weight. The dispersion process is not particularly limited, and a counter collision method, an ultrasonic method, a wet milling method, or the like may be used.

A dispersant may be used to facilitate dispersion during the dispersion, and the dispersant may be selected in consideration of the surface potential value of cerium oxide in water, but there is no particular limitation. Dispersion of cerium oxide is usually in the range of pH 4-9, wherein the surface potential of cerium oxide has a positive value, an anionic organic compound may be preferably used. Specific examples thereof include polyacrylic acid and poly Vinyl sulfuric acid, poly methacrylic acid, polyacrylamide, polyarylamine, and the like. Preferably, the dispersant has a weight average molecular weight of 1,000 or more and 50,000 or less, and if the molecular weight is less than 1,000, it is difficult to secure dispersion stability of the cerium oxide slurry. If the dispersant exceeds 50,000, the viscosity of the slurry increases, making it difficult to secure long-term stability. .

As described above, in order to remove the large particles existing in the slurry with respect to the cerium oxide slurry treated as described above, in the present invention, the large particles having a particle diameter of 0.7 μm or more are forcibly removed by centrifugation. For example, by passing the slurry through a cylinder rotating at several thousand rpm, preferably 1,000 to 5,000 rpm, large particles in the slurry can adhere to the inner wall of the cylinder, thereby removing particles having a relatively large particle size. When the slurry passes through the cylinder at a constant flow rate, the centrifugal force acts on the large walls in the case of large particles, and the small particles pass through the cylinder without being attached to the walls.

Ceria slurry to remove the large particles in a centrifugal separation process as described above, before and after the after in accordance with the present invention, the slurry is the average centrifugal force to the second rotary minutes at the conditions 1970g ₀ (g ₀ = gravitational acceleration) force sedimentation the particles receive test When carrying out a test comparing the weight of the (centrifugal slurry concentration reduction test), it is possible to exhibit a slurry concentration (ie solids) reduction of up to 20% by weight, preferably up to 10% by weight.

While it is difficult to obtain information on the large particles present in the 1% or less when analyzing by using a commonly used particle size analyzer, the centrifugal slurry concentration reduction test according to the present invention is a slurry for the same average particle diameter It can be said that the large particle content of.

The slurry of the present invention prepared in this way is that most of the large particles are already reduced, and when used as a finished abrasive product in the chemical mechanical polishing process, excellent polishing performance can be obtained compared to a slurry using only a conventional disperser and a significant scratch reduction effect. That is, since the ceria slurry according to the present invention only removes large particles, the average particle diameter is maintained in the range of 0.1 to 0.2 μm, so that polishing productivity can be reduced by more than 90% when polishing is performed according to the conventional process. Can be.

The slurry according to the present invention may be subjected to a filtering process as necessary after the centrifugation process for removing large particles as described above in the slurry manufacturing process.

The cerium oxide slurry according to the present invention is applicable not only to polishing semiconductor films for fine patterns of 0.16 μm or less, but also to CMP polishing of semiconductor interlayer insulating layer (ILD layer) and shallow trench isolation (STI), which have been polished with conventional silica slurry. It is possible, and the long-term stability is also very good due to the small amount of sinking particles even after long-term storage.

The following examples are provided for illustrative purposes only to aid in understanding the present invention and are not intended to limit the scope of protection described in the claims.

Example

Preparation Example 1 Cerium Oxide Powder Preparation

The cerium hydroxide was heat treated at 750 ° C. to obtain cerium oxide, which was then milled with a ball mill to obtain a cerium oxide having a size of 40 nm as measured by XRD.

Preparation Example 2 Preparation of Abrasive Finish

On an 8-inch silicon wafer, a silicon dioxide film was deposited to a thickness of 10,000 Å by plasma enhanced-chemical vapor deposition (PE-CVD) method using TEOS (tetraethyl orthosilicate), or PE-TEOS process. An abrasive film was prepared.

Preparation Example 3 Preparation of Cerium Oxide Slurry

After adding 800 g of cerium oxide powder obtained in Preparation Example 1 to 9160 g of deionized water, the mixture was stirred for 30 minutes using a propeller stirrer so that the powder agglomerates agglomerated in the preparation of cerium oxide powder did not remain in water. After adding 20 g of polyacrylic acid (weight average molecular weight 3000, concentration 40% by weight) as a dispersing agent with stirring, the particles were collided at a pressure of 200 MPa using an anti-collision disperser to uniformly disperse 8% by weight of water. Cerium oxide slurry was obtained.

Preparation of Cerium Oxide Polishing Slurry

Example 1

Injecting the cerium oxide slurry of Preparation 3 from the bottom of the cylindrical centrifuge rotating at 1,500rpm and withdrawn to the top (at this time, the large particles are attached to the base wall of the centrifuge and only small particles come out of the top of the centrifuge) , Large particles were removed. Then, after measuring the wt% of the slurry, deionized water was added to prepare a 5 wt% ceria slurry.

Example 2

A 5 wt% ceria slurry was prepared in the same manner as in Example 1 except that the rotation speed of the centrifuge was 2,000 rpm.

Example 3

The cerium oxide slurry of Preparation Example 3 was centrifuged at 1,500 rpm to remove large particles first, and then filtered using a filter having a size of 1 μm. The process was then performed in the same manner as in Example 1 to prepare a 5 wt% ceria slurry. .

Comparative Example 1

The cerium oxide slurry of Preparation Example 3 was added to only deionized water without centrifugation to prepare a 5 wt% ceria slurry.

Comparative Example 2

Cerium oxide slurry of Preparation Example 3 was filtered directly at a flow rate of 10L / min in a 3㎛ size filter without centrifugation, and the process was carried out in the same manner as in Example 1 to prepare a 5wt% ceria slurry.

Comparative Example 3

 Cerium hydroxide was heat-treated at 650 ° C. to obtain cerium oxide, which was then milled with a ball mill to obtain a cerium oxide powder having an average particle diameter of 25 nm as measured by XRD. This was carried out in the same manner as in Preparation Example 3 and Example 1 to prepare a 5wt% ceria slurry.

Reference Example

The CSL test was performed while changing the rpm and time for the cerium oxide slurry according to Example 1, and the results are shown in Table 1 below.

Particle size measurement of particles in slurry

For the slurries of Examples 1 to 3 and Comparative Examples 1 to 3, the average particle diameter was measured using a particle size analyzer LA910 manufactured by Horiba, Japan, and the results are shown in Table 2.

Centrifugal sedimentation concentration reduction test and large particle content test

For the slurries of Examples 1 to 3 and Comparative Examples 1 to 3, a tubular centrifuge (Hanil Science Industrial MF80) was used to determine the content of particles that could sink and agglomerate to the bottom of the slurry storage container during long term storage. Forced sedimentation to reduce the concentration of cerium oxide solids. The test method was filled with 40 ml of 5% by weight cerium oxide slurry in a centrifuge tube having a height of 11.5 cm and a volume of 50 ml, respectively, and rotated at 4,000 rpm for 2 minutes (when centrifuged, the test tube was in a horizontal state. The distance from the center of rotation to the bottom of the test tube is 14 cm and the distance to the test tube entrance is 2.5 cm, the centrifugal force of the slurry is 1970 g ₀ ), and the supernatant except for the solid cake that has settled to the bottom of the test tube After transferring to the weight percentage of the supernatant was calculated as shown in Equation 1 to obtain the centrifugal sedimentation concentration reduction% (CSL%). A smaller percentage reduction means less concentration of larger particles. Through this test, long-term stability can be confirmed, and the content of large particles can also be confirmed. The test results are shown in Table 2.

Polishing Characteristics of Finished Film

Each cerium oxide slurry obtained in Examples 1 to 3 and Comparative Examples 1 to 3, as an 8-inch CMP polishing machine, to be polished obtained in Preparation Example 2 using a Mirra apparatus (AMAT USA) The membrane was polished for 90 seconds at a pressure of 3.5 psi. The slurry was supplied at a rate of 150 ml / min, the rotation speed of the top plate wafer head was 104 rpm, and the rotation speed of the bottom plate was 110 rpm. The pad used here used IC1000 / suba IV stacked pads of Rodel, USA.

After polishing of the finished film, the results were evaluated for the number of scratches with a size of 0.16 μm or more using AIT-XP, a scratch evaluation device of KLA-Tenco, USA, and before and after polishing using Therma-wave Optiprobe 300 series, THERMA-WAVE, USA. Table 2 also shows the results of evaluating the amount of polishing by the film thickness measurement.

From Table 2, it can be seen that the cerium oxide slurry according to the present invention maintains an average particle diameter of 0.1 to 0.2 μm, and thus has excellent polishing amount and low CSL%, which is excellent in long-term stability and can significantly reduce the number of scratches generated during semiconductor polishing. Can be.

According to the present invention, a cerium oxide slurry having a weight percent concentration change of 20% or less in a CSL test under predetermined conditions has a significantly smaller number of scratches and a smaller size during chemical mechanical polishing, and also a bottom of a storage container. As there are few particles sinking in, there is no agglomeration between particles, so the number of scratches does not increase even after long-term storage.

Claims (5)

A cerium oxide slurry for polishing a semiconductor thin film comprising an cerium oxide powder having an average particle diameter in the range of 0.1 to 0.2 μm, and satisfying Equation 1 below: <Equation 1> (C ₀ -C ₁ ) / C ₀ X 100 ≤20 C ₀ is the solids concentration of the original slurry, C ₁ is the solid content concentration after centrifugation for 2 minutes under the condition that the average centrifugal force g received by the slurry is 1970 g ₀ , and g ₀ is the gravitational acceleration. The method of claim 1, A cerium oxide slurry, which is prepared by dispersing cerium oxide powder in water at a concentration of 0.5 to 20% by weight and centrifuging at a rotational speed of 1,000 to 5,000 rpm. The method of claim 2, The cerium oxide slurry, characterized in that the centrifugation process is a method of injecting the slurry at a constant flow rate at the lower end of the cylinder rotating at a high speed to discharge to the top. A method of polishing a semiconductor thin film or an insulating film using the cerium oxide slurry according to any one of claims 1 to 3. The method of claim 4, wherein A method of grinding a semiconductor thin film for fine patterns having a line width of 0.16 µm or less.