KR20040050721A - Slurry composition for final polishing of silicon wafer - Google Patents

Abstract

PURPOSE: A slurry composition for final polishing of silicon wafer is provided to increase polishing speed and improve polishing characteristics. CONSTITUTION: A slurry composition for final polishing of silicon wafer contains colloid silica of 2-10 weight% as an abrasive, ammonia of 0.5-1.5 weight%, and a hydroxide alkyl cellulose based water-soluble polymer thickener of 0.2-1.0 weight%. At this time, the grain diameter of the colloid silica is in the range of 60-80 nm. The last polishing slurry composition further contains an amine compound of 0.01-1 weight%, quaternary ammonium salt of 0.01-0.5 weight%, and deionized water. Preferably, the amine compound is one selected from a group consisting of monoethanolamine, diethylene glycolamine, diethanolamine, triethanolamine, (dimethylamino)ethoxyethanol, aminoethylethanolamine, or piperidineethanol.

Description

Slurry Composition for Final Polishing of Silicon Wafer

The present invention relates to a slurry composition for secondary polishing of a semiconductor wafer, and more particularly, to a polishing slurry composition for manufacturing a semiconductor wafer having improved polishing quality while improving polishing rate during secondary polishing of a semiconductor wafer.

The chemical mechanical polishing (CMP) process in silicon wafer fabrication is the last step to reduce the microroughness of the wafer surface to create a smooth surface and remove physical surface defects such as microscratch. Wafers that have undergone this CMP process are capable of producing mirror surfaces of low surface defects. Residual microscratches on the wafer surface are defects that cause problems in the photolithography process that implements the circuit. It is important to remove microscratches in the CMP process to lower the residual value.

Silicon wafers, which serve as substrates in semiconductor manufacturing, are manufactured through various processes such as single crystal growing, slicing, lapping, etching, mirror polishing, and cleaning. . The mirror polishing process, the final stage of the manufacturing process, eliminates surface or subsurface defects created in the previous process, such as scratches, cracks, grain distortion, surface roughness, and surface topography. It is removed and processed into a defect-free mirror wafer.

The CMP process of the wafer is a multi-step process, which removes the remaining microscratches and removes the microroughness of the surface by several seconds, which requires a fast polishing rate to remove deep scratches on the surface. It consists of a second (final) polishing step that lowers the mirror surface.

Abrasive processing requires two important components in addition to polishers and deionized water. It is a silica slurry which is a soft or hard urethane polishing cloth and polishing liquid.

The polishing of the wafer surface is explained by the reaction of Chemical Mechanical Polishing. The polishing cloth serves as mechanical polishing, and the polishing liquid (slurry) assists in mechanical polishing of the pad and also causes chemical polishing. It is. The large diameter of wafers and their high quality demands require the improvement of performance of abrasive cloth and slurry. In particular, since slurry is regarded as the final regulator of wafer quality, products with various physicochemical properties have been released and are being studied continuously.

In the CMP process, a chemically and physically accelerated slurry is used. An abrasive, a pH adjusting base, and deionized water are common components, and organic or inorganic additives may be added to achieve a specific polishing quality.

Silica is mainly used as a silica, it is common to use potassium hydroxide, sodium hydroxide or ammonia water as a pH adjuster. In addition to these components, additives are used, such as nonionic surfactants and amines for improving the polishing rate, improving the cleanliness of the polishing surface, and improving the dispersibility of the abrasive.

It is common to use separate slurries that match the process characteristics for each CMP process. The primary polishing slurry and the final polishing slurry are formulated with different physical properties to double the process specific properties. In order to double the polishing rate, the primary slurry greatly adjusts the size (80-120 nm) and concentration (2-30% by weight) of the abrasive, and the pH is in the range of 11-12 to enhance both mechanical and chemical polishing power. On the other hand, since the final slurry is a key to removing surface defects rather than promoting the polishing rate, the mechanical polishing effect is lowered by lowering the size of the abrasive (10 to 80 nm) and the concentration (0.2 to 10 wt%), while the chemical polishing effect is reduced. In order to promote the clean mirror surface, various functional additives may be blended.

Trennnick et al., In U.S. Patent No. 3,715,842, disperse silica particles of 100 nm or less in water, add 0.05% by weight or more of ammonia thereto, and bring the pH to 7 or more, followed by methyl cellulose (HMC). In addition, ethyl cellulose hydroxide (HEC) and propyl cellulose hydroxide (HPC) were added to 0.05 to 2.5% by weight to prepare a slurry for the final polishing to suppress the precipitation of silica to reduce the scratch.

Payne et al. Use particles ranging in size from 4 to 100 nm in a series of patents (US Pat. Nos. 4,169,337, 4,462,188, and 4,588,421) and use amines of aminoethanolamine or ethylenediamine. The polishing rate was improved by adding 2 to 4% by weight or by adding 4 to 4% by weight of a quaternary ammonium salt such as tetramethylammonium chloride or tetramethylammonium hydroxide (TMAH).

Sasaki et al. Proposed a slurry using colloidal silica, a water-soluble polymer, and a water-soluble salt in US Pat. No. 5,352,277. Silica was 5 ~ 500nm 20 to 50%, the amount of water-soluble polymer is about 100ppm, salt is selected from Na, K, NH ₄ cation, Cl, F, NO ₃ , ClO ₄ anion Was set to 20 to 100 ppm. This slurry was used to produce a soft surface with reduced surface roughness below 5 nm.

Longcki et al. Used in the international patent publication WO 96/38262 0.2 to 0.5% by weight of silica and less than 0.01 to 0.1% by weight of amine and 0.02 to 0.05% by weight of polyvinyl alcohol (PVA). And it was prepared as a final polishing slurry using an amine to maintain pH 8-11. When the 150 mm wafer was polished, the HAZE level was 0.06 ppm and the LPD of 0.1-0.3 micron averaged less than 90 qualities, but no other defects were noted.

Inoue et al. Presented a secondary or final polishing composition in Japanese Patent Application 2000-6327. The abrasive of the composition used a silica of 20 ~ 300nm and used as the base at 0.001 ~ 0.3% by weight TMAH. It was mentioned to improve the hydrophilicity of the wafer surface after polishing by adding ethyl cellulose hydroxide (HEC) having a molecular weight of 1.3 million or more, but did not deviate from the composition of the general polishing slurry.

As seen from the above example, the polishing slurry used in the related art may be added to the colloidal silica abrasive as a basic dispersion phase and additionally, a polishing rate accelerator or dispersion stabilizer. In addition, in order to lower the level of LPD representing the surface residual bonds, it is important to implement a unique combination of the slurry composition.

The present invention is to solve the problems of the prior art as described above, it is an object of the present invention to provide a slurry composition having excellent polishing speed and improved polishing characteristics such as LPD surface defects and uniformity (uniformity).

That is, the present invention is an abrasive, 2 to 10% by weight colloidal silica having a particle size of 60 to 80nm, 0.5 to 1.5% by weight of ammonia, 0.2 to 1.0% by weight of a water-soluble polymer thickener of alkyl cellulose, 0.01 to 1% by weight of an amine compound, A slurry composition for secondary polishing of a semiconductor wafer comprising 0.01 to 0.5% by weight of quaternary ammonium base and ultrapure water as the remaining components.

Hereinafter, the present invention will be described in more detail.

The slurry composition of the present invention comprises ultrapure water, silica abrasive, ammonia, water-soluble polymer thickeners of alkyl celluloses, amine compounds and quaternary ammonium bases.

As the silica abrasive, colloidal silica having an average size in the range of 60 to 80 nm is used to reduce the effect of mechanical polishing.

The concentration of silica in the total composition is in the range of 2 to 10% by weight, preferably 4 to 6% by weight. Although the dispersion stability between particles is increased due to the low concentration of the abrasive, there is a problem that the polishing rate is reduced. The present invention achieves a polishing rate of 0.5 to 1 micron per minute using an abrasive of 60 nm to 80 nm larger than the general particle diameter of 30 to 40 nm to compensate for this disadvantage. As mentioned above, dispersing stability and storage stability can be increased by low concentration of silica, and this dispersion stabilization suppresses the generation of large particle impurities in the slurry, thereby obtaining a polishing quality in which scratches, especially submicro scratches, are reduced.

In order to double the chemical dispersibility of silica and add chemical polishing effect in the CMP process, ammonia, a weak base, was used as a pH regulator. Ammonia water was added so that the pH was 10.4-10.7. The amount of such ammonia used is in the range of 0.5 to 1.5% by weight.

In order to further double the dispersion stability of the particles, a water-soluble polymer thickener is used. As the polymer thickener, water-soluble alkyl hydroxide celluloses are used. Specifically, hydroxypropyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxyethyl cellulose adjusted to lipophilic, Hydroxymethyl cellulose, methyl cellulose, etc. are mentioned, It can be used individually and in mixture of 2 or more types.

These alkyl hydroxide celluloses play a key role in making the wafer surface a mirror soft surface, which doubles the action of the silica abrasive to contact the surface in a regular orientation. It also acts as a dispersion stabilizer for silica because thickeners create a three-dimensional network, which delays the aggregation or settlement of silica.

The alkyl hydroxide cellulose is stable at high temperature, the clouding point (clouding point) is preferably 50 ℃ or more. In this respect, it is preferable to use hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose. In addition, the molecular weight of the alkyl cellulose is preferably used in the range of 200,000 to 1.5 million to generate a laminar flow. The usage-amount is used within the range whose viscosity of a slurry is 7-80 cP, Preferably it is 20-80 cP, More preferably, it is 30-70 cP. The amount of the polymer thickener used is in the range of 0.2% to 1.0% by weight.

In the present invention, in order to improve the polishing rate and to improve the uniformity (waveness) of the surface, the amine compound and the quaternary ammonium base are added in combination.

The amine compound added to improve the polishing rate is specifically monoethanolamine, diethylene glycolamine, diethanolamine, triethanolamine, and (dimethylamino) ethoxy. Ethanol ((Dimethylamino) ethoxyethanol), aminoethylethanolamine

(Aminoethylethanolamine), Piperidineethanol (Piperidineethanol) is an example.

The concentration in the total composition is 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight. If it is less than 0.01% by weight, the effect of promoting the polishing is not exerted, and if it is more than 0.5% by weight, especially 1% by weight, the surface roughness increases and the LPD increases greatly, which is not preferable. However, when the proper concentration is added, the polishing rate can be greatly increased to 1 to 1.5 microns per minute while maintaining the surface roughness stably. However, in this case, since LPD quality deterioration occurs, the present invention uses a quaternary ammonium base to prevent LPD deterioration due to the addition of amines.

Quaternary ammonium bases used for this purpose include tetramethylammonium hydroxide and tetraethylammonium hydroxide.

(Tetraethylammoniumhydroxide) trimethyl (ethoxy) ammonium hydroxide

(Trimethyl (ethoxy) ammoniumhydroxide), N, N-dimethylpiperidine hydroxide (N, N-

Dimethylpiperidinehydroxide) etc. are mentioned, for example. These quaternary ammonium bases have been considered to have the effect of neutralizing the reactivity of the siloxane derivative, which is a polishing remover, to suppress surface resorption or particle destabilization.

In addition to these effects, when the quaternary ammonium base was used together with the amine used in the present development, it was confirmed that the surface flatness was also improved.

The quaternary alkylammonium base is used in the range of 0.01 to 0.5% by weight in the range of pH 10.4 ~ 10.7 of the final product. If the concentration is less than 0.01% by weight, it is difficult to obtain the effect of improving the polishing quality. If the concentration is higher than 0.5%, the dispersion stability of the silica is broken, so that precipitation phenomenon occurs and the polishing effect cannot be exhibited.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not intended to be limited by the following Examples.

In the Example, Rodel 2371 was used for primary polishing, and polishing quality was compared by polishing using a slurry of the present invention for secondary and tertiary polishing. Polishing surface was analyzed by SURFSCAN SP-1 of KLA-TENCOR.

[Polishing condition]

Polishing Machine: STRAUGHBAUGH MARK9K

Table speed: 50rpm

Head speed: 30rpm

Slurry Flow Rate: 0.5L / min

Pressure: 5psi

[Examples 1-4 and Comparative Examples 1-3]

Colloidal silica with an average particle diameter of 70 nm was diluted with ultrapure water to have a particle content of 4% by weight (based on the final composition), and ammonia was added to 1% by weight (based on the final composition) to obtain a pH of 10.3-10.5. . As a thickener, hydroxypropyl cellulose having an average molecular weight of 500,000 was mixed in an amount of 0.7% by weight (based on the final composition), an amine compound and a quaternary ammonium base were mixed with the ingredients and contents shown in Table 1, and then IMO HOMOGENIZER Was stirred at 2000 RPM to prepare a slurry composition having a viscosity of 65 cP.

The slurry thus prepared was diluted 10-fold with ultrapure water and used for secondary and final polishing.The p-type 200mm flat wafer of (10) orientation was used for speedfam multihead with hard urethane polishing cloth. Polishing with a polishing machine. SCRATCH on the wafer surface was analyzed by KLA-Tencor SP1.

Amine (% by weight) Quaternary ammonium base (% by weight) Polishing speed (㎛ / min) Roughness (Å / 80㎛2) LPD (> 0.1 μm, ea) Example 1 DGA 0.2 × 0.9 1.9 41 Example 2 DGA 0.2 TMAH 0.3 1.2 1.6 18 Example 3 AEEA 0.2 × 1.1 1.8 38 Example 4 AEEA 0.2 TMAH 0.3 1.5 1.5 23 Comparative Example 1 × × 0.6 3.7 105 Comparative Example 2 × TMAH 0.3 0.7 2.4 84 Comparative Example 3 × TMEAH 0.3 0.9 1.6 120

DGA: Diethylene Glycolamine

AEEA: aminoethylethanolamine

TMAH: Tetramethylammonium Hydroxide

TMEAH: trimethyl (ethoxy) ammonium hydroxide

When the amine is added from the results of Table 1, it can be seen that the polishing rate is greatly improved, especially when used with a quaternary ammonium base group, the flatness and LPD quality are also improved.

[Comparative Examples 4 and 5]

The primary particle size, secondary particle size, and viscosity are shown in Table 2 below, silica concentration was 6% by weight, and the slurry was diluted 10-fold with ultrapure water at a pH of 10.7, and the polishing was carried out in the same manner as in the above example. The results are shown in Table 2.

Particle size (nm) Viscosity (cP) Polishing speed (㎛ / min) Roughness (Å / 80㎛ ² ) LPD (> 0.1㎛, ea) Comparative Example 4 60 30 0.8 2.3 34 Comparative Example 5 80 55 1.0 2.1 27

From the results of Table 2, it can be seen that the composition of the present invention is improved in terms of excellent polishing quality, in particular, polishing rate, compared to the polishing quality of the commercially available secondary polishing slurry.

The slurry composition of the present invention improves the polishing quality in the final polishing process of the semiconductor wafer, while increasing the polishing rate, which is the ability to improve productivity compared to the conventional slurry, by increasing the polishing rate by 30% or more to provide a high-quality silicon wafer mirror polishing slurry. I can make it.

Claims (4)

2-10% by weight of colloidal silica having a particle diameter of 60-80 nm, 0.5-1.5% by weight of ammonia, 0.2-1.0% by weight of a water-soluble polymer thickener of alkyl cellulose, 0.01-1% by weight of an amine compound, and 0.01-quaternary ammonium base A slurry composition for secondary polishing of a semiconductor wafer comprising 0.5 wt% and ultrapure water as the remaining components. The method of claim 1, wherein the amine compound is monoethanolamine (Monoethanolamine), diethylene glycol amine (Diethylene glycolamine), diethanolamine (Diethanolamine), Triethanolamine, (dimethylamino) ethoxyethanol ((Dimethylamino) ethoxyethanol), aminoethylethanolamine or piperidineethanol. The method of claim 1, wherein the quaternary ammonium base is tetramethylammonium hydroxide tetramethylammonium hydroxide, tetraethylammonium hydroxide (tetraethylammonium hydroxide), trimethyl (ethoxy) ammonium hydroxide (Trimethyl (ethoxy) ammonium hydroxide) or N, N-dimethylpiperidine Slurry composition, characterized in that the hydroxide (N, N-Dimethylpiperidine hydroxide). According to claim 1, wherein the water-soluble polymer thickener hydroxypropyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose having a molecular weight of 200,000 to 1.5 million, hydroxyethyl cellulose, Slurry composition characterized in that the viscosity of the slurry is adjusted to 7 ~ 80 cP by using hydroxymethyl cellulose, methyl cellulose alone or a mixture of two or more thereof.