KR100497410B1 - Slurry Composition for Chemical Mechanical Polishing of Oxide with Enhanced Polishing Performance - Google Patents

Abstract

The present invention relates to a slurry composition for polishing an oxide film of a semiconductor device, wherein the slurry composition of the present invention comprises an orifice containing fine metal oxide powder, alkali base, one of primary to tertiary amines, quaternary ammonium base, and polyethylene glycol in ultrapure water. It is characterized in that it is produced by dispersing according to a method that causes shear force, impact force and cavitation in the slurry composition of the present invention, the polishing rate and polishing uniformity is greatly improved to enable the production of high quality mirror silicon wafer, semiconductor In addition to the device, it is applicable to polishing of various industrial products such as photomasks, glass discs and synthetic resins.

Description

Slurry Composition for Chemical Mechanical Polishing of Oxide with Enhanced Polishing Performance}

The present invention relates to a polishing slurry composition used in a chemical mechanical polishing (CMP) process of a semiconductor device wafer, and more particularly, to an oxide film polishing slurry composition having improved polishing speed and polishing uniformity.

Semiconductor devices are entering the era of ULSI, which is represented by 256M and 1G bit DRAM through high performance and high integration, and the line width of 0.18um and 0.12um is applied in the next generation devices as the minimum processing size of device manufacturing is getting smaller. ought.

In the case of such a high-density device, in order to obtain a desired resolution during photolithography, it is necessary to improve the performance of a stepper, increase the numerical aperture of the lens, and shorten the wavelength of light. However, proceeding with these conditions will result in a shallow depth of focus and insufficient resolution at the device surface. In addition to the miniaturization of the wiring structure, in order to construct a high-density integrated circuit, the number of wiring layers is also multiplied. In the case of logic elements, the number of layers increases to 6 to 7 layers and the DRAM to 2 to 3 layers. It is expected to increase. The fact that the number of wiring layers is large means that the surface structure of the material is complicated and the degree of surface irregularities is increased.

The planarization technique is adopted as an important technique to solve the problems caused by the reduction of the depth of focus and the multilayer structure of the wiring structure during the photo process. The reason is that the surface realized by wide area planarization is an ideal state for easy and accurate photographic process and wiring formation.

The planarization of semiconductor device wafers has been proposed by several methods such as reflow, SOG, etch back, ECR, Depo & Etch, but partial planarization is the mainstream. For example, chemical mechanical polishing ("CMP") has been in the spotlight as the most efficient way to realize wide area planarization.

The principle of the CMP technology is to planarize uneven portions of the wafer surface by physically reacting the polishing pad and the wafer while chemically reacting the wafer surface by supplying a slurry with the wafer in contact with the polishing pad surface. .

The slurry used in the semiconductor CMP process is mainly composed of deionized water and a metal oxide, and as a metal oxide, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), which is prepared by a fuming method or a sol-gel method, Ceria (CeO ₂ ), zirconia (ZrO ₂ ), titania (TiO ₂ ), and the like are mainly used. As the additive, basic compounds such as potassium hydroxide, sodium hydroxide, and amine are used when the material to be polished is an insulating layer of SiO ₂ , and sulfuric acid and nitric acid when the material to be polished is a metal such as a wire or a plug. And an oxidizing agent such as fruit water can be used together with an acid such as acetic acid.

Among the various metal oxides, fumed silica is most widely used due to its commercially available and inexpensive and the same material as that of the semiconductor insulating layer (SiO ₂ ), so that there is no fear of contamination. Until now, various methods have been proposed to improve the polishing performance of CMP slurry using fumed silica as an abrasive. For example, as a method for increasing the polishing rate, a method of adding an etchant such as aminoethylethanolamine or the like (see US Patent No. 4,169,337), and co-precipitating a small amount of other component particles such as CeO _{2 in} preparing SiO ₂ After the composition (see US Pat. Nos. 3,262,766 and 3,768,989), and a method of adding inorganic salts such as Ce (OH) ₄ , NH ₄ SO ₄ , Fe (SO ₄ ) and the like to the prepared slurry ( See Mechanism of Glass Polishing (1971) Vol. 152, p. 1729). Further, a slurry composed of silica / amine / inorganic salt / polyhydriccohol (see US Patent No. 4,169,337), a slurry composed of silica quaternary ammonium salt (US Pat. No. 5,139,571), ceria / carboxylic acid Slurry consisting of silica (see US Pat. No. 5,759,917), slurry consisting of tetramethylammonium salt / fruit tree / silica (US Pat. No. 5,938,505), slurry consisting of electron donor compound / TMAH / silica U.S. Patent No. 6,009,604) and the like are known, and these slurries commonly use alkaline bases as stabilizers.

These slurries are actually applied to the semiconductor production process, and are evaluated to have reached a satisfactory level in terms of polishing speed, uniformity, flatness, and selection ratio in terms of polishing performance. However, as the high integration of devices accelerates, the quality requirements for these unit items become more stringent. Therefore, semiconductor manufacturers are required to continuously improve the polishing slurry, and to satisfy multiple quality items simultaneously with a single product. Is still difficult. Furthermore, in response to the trend of smaller chip sizes and miniaturization of circuit structures, various quality characteristics of the polishing pad and slurry are applied to ensure both planarity and uniformity of the wafer surface. A lot of research is going on. In particular, in terms of slurry, each slurry manufacturer is striving to develop high-tech manufacturing technology and high-performance products due to the dependency that the surface characteristics of the wafer and the characteristics of various polishing pads must be matched.

Accordingly, the present invention is to solve the problems of the prior art as described above, in the polishing of the interlayer insulating film to which the CMP technology is applied in the manufacture of semiconductor devices, greatly improves the polishing rate and surface non-uniformity within the wafer (Within Wafer Non-Uniformity) It is an object of the present invention to provide a polishing composition which is significantly improved in the property of lowering), which is applicable to a high device forming technique.

That is, the present invention provides a polishing composition comprising the following components:

(a) fine metal oxide powder;

(b) alkali bases;

(c) one of the primary to tertiary amines;

(d) quaternary ammonium bases;

(e) polyethylene glycol; And

(f) ultrapure water.

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

The metal oxide used as the abrasive in the present invention is one or more selected from the group consisting of silica, alumina, ceria, zirconia, and titania, and any one produced by any of the fume method and the sol-gel method may be used. The use of silica is most preferred in view of economics and wafer contamination prevention. these The primary particle size (TEM measurement result) of the metal oxide is 10 to 70 nm, preferably 20 to 40 nm, and the specific surface area is preferably 100 to 300 m ² / g. If the primary particles are too small, less than 10 nm, the removal rate is low, which is undesirable in terms of throughput. On the contrary, when the primary particles are larger than 70 nm, the removal rate is increased, which is advantageous in terms of productivity, but difficult to disperse and large. It is not preferable because a large amount of particles are present to cause a large amount of μ-scratches. These metal oxides are preferably dispersed such that secondary particles in an aqueous dispersion state have an average size of 100 to 200 nm, and in order to maintain dispersion stability for a long time, the hydroxyl group concentration on the surface of the metal oxide is preferably 0.5 to 4 / nm ² . Do. The content of the metal oxide in the slurry is 0.1 to 50% by weight, preferably 1 to 50% by weight of the total weight of the slurry.

In the present invention, as an additive for adjusting the pH and improving the polishing rate, one type of amine among the alkali base and the primary to tertiary amines is used in an amount such that the pH of the slurry is 10.0 to 11.0. Examples of preferred alkali bases include sodium hydroxide, potassium hydroxide and ammonium hydroxide, and the amount of the alkaline base used is preferably within the range of 0.1 to 1% by weight of the total weight of the slurry. Meanwhile, examples of primary amines usable in the present invention include methyl amine, isopropyl amine, ethanol amine, and tert-butylamine, and examples of secondary amines include diethyl amine, dimethylamine and ethylmethylamine. And tertiary amines include sec-butyldimethylamine, triethylamine and triethanol amine. Among them, methyl amine, isopropyl amine, and diethyl amine are most preferably used, because when the amines have too many carbon atoms, they may be adsorbed on the surface of the insulating film to form a film, thereby reducing the polishing performance. to be. The amine content of the slurry composition of the present invention is approximately 0.01 to 1% by weight.

In the present invention, the quaternary ammonium base is used to improve the polishing rate, and the amount of the quaternary ammonium is adjusted in the range of 0.01 to 1% by weight of the total weight of the slurry so that the final pH of the slurry can be 10.5 to 11.5. Quaternary ammonium bases, in addition to the role of polishing accelerators, serve as a key additive in improving polishing quality, in particular the residual Light Point Defect (LPD) concentration and surface uniformity of the wafer surface. In more detail, the function of the quaternary ammonium base is as follows. The quaternary ammonium bases, including tetramethylammonium hydroxide (TMAH), tetramethylammonium chloride, tetramethylammonium nitrate, tetramethylammonium sulfate, etc., form hydrogen bonds or ionic bonds with Si-OH of siloxanes, which are abrasive removal products. As this reduces the reactivity of the Si-OH, these degreasers grow into colloidal size unstable amorphous particles by re-adsorption on the surface of the abrasive material or by polymerisation condensation between the degreasers or more critically Undesirable reaction paths such as a decrease in polishing rate, the occurrence of micro-scratches, and the retention of particles, which occur when the polymer triggers crosslinking reactions between the abrasive particles and the particles, thereby promoting destabilization of the abrasive particles, , The polishing rate is increased as well as the surface defect μ-scratch The polishing property is reduced to reduce the LPD detected by the equipment.

However, considering the dispersion stability of the abrasive particles, it is known that the strong base quaternary ammonium base weakens the electrical double layer of the abrasive particles to inhibit dispersibility. In the present invention, through the optimization of the dispersion method, the quaternary ammonium base is uniformly distributed among the abrasive particles to chemically react with the abrasive particles so that the alkyl group of the quaternary ammonium base acts as a steric obstacle on the surface of the abrasive particles. As a result, it was confirmed through various evaluations that the dispersibility of the abrasive particles was improved. The dispersion method of the present invention is to accelerate the primary mixed slurry obtained by mixing each of the above components with ultrapure water at high pressure to generate shearing force, impact and cavitation in the orifice. (Reference: Korean Patent Application No. 98-39212, Korean Patent Application No. 99-34608).

In the present invention, polyethylene glycol (PEG) is used to further improve the dispersion stability of the abrasive particles and to improve the surface roughness of the material to be polished. It is preferable that the molecular weight of polyethyleneglycol used for this invention is 15,000-25,000, since the viscosity of a final resin composition will rise non-ideally if it has a molecular weight more than that. The content of polyethylene glycol in the slurry is preferably 0.001 to 0.1% by weight of the total weight of the slurry, if the amount is too small to achieve the desired effect in the present invention, while the amount is excessively inhibited dispersion stability It is not preferable because a problem occurs.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

Example 1

30 g of a 20 wt% KOH solution was added to a 4 liter polyethylene container containing 1682 g of deionized water, 10 g of 25 wt% -TMAH, 8 g of methyl amine, and 0.3 g of PEG were added, followed by stirring at 50 rpm for 10 minutes. While stirring the mixture at 500 rpm, 280 g of silica was added dropwise and further stirred for 40 minutes to complete the first mixing. Subsequently, using the method of accelerating the primary mixed slurry to a high pressure to cause shear force, impact force and cavitation in the orifice (see Korean Patent Application No. 98-39212, Korean Patent Application No. 99-34608) Dispersed. The dispersed slurry was filtered using a 1 micron filter, and then ground for 2 minutes under the following conditions. The polishing rate was measured by changing the thickness of the wafer removed by polishing, and the LPD generation amount on the wafer surface was measured by using Surfscan 6420 of KLA-TENCOR. The evaluation results are shown in Table 1 below.

   ▷ Grinding Machine Model: STRASBAUGH 6EC

   ▷ Polishing pad: IC1400 (Rodel)

   ▷ Polishing target: PTEOS, 6 "Blanket Wafer

   ▷ Polishing condition

Flattening speed Spindle speed Down Force Back pressure Slurry flow rate Temperature Oscillation 60 rpm 40 rpm 8.0 psi 3.0 psi 150ml / min 25 ℃ ± 10mm

Examples 2-3

A slurry was prepared in the same manner as in Example 1 except that diethyl amine and isopropyl amine were used instead of methyl amine, and the polishing performance was evaluated. The evaluation results are shown in Table 1 below.

Comparative Example 1

A slurry was prepared and the polishing performance was evaluated in the same manner as in Example 2, except that PEG was not added. The evaluation results are shown in Table 1 below.

Comparative Example 2

A slurry was prepared in the same manner as in Example 1 except that methyl amine was not added, and the polishing performance was evaluated. The evaluation results are shown in Table 1 below.

Comparative Example 3

A slurry was prepared in the same manner as in Comparative Example 1 except that diethyl amine was not added, and the polishing performance was evaluated. The evaluation results are shown in Table 1 below.

Metal oxide Additive (% by weight) pH Polishing performance Methylamine Diethylamine Isopropylamine PEG  Oxide polishing rate (Å / min) WIWNU (%) LPD> 0.3 μm Example 1 Silica 0.4 × × 0.015 11.2 6,620 4.6 39 Example 2 Silica × 0.4 × 0.015 11.2 6,850 4.3 21 Example 3 Silica × × 0.4 0.015 11.3 6,595 4.9 25 Comparative Example 1 Silica × 0.4 × × 10.5 6,750 5.8 43 Comparative Example 2 Silica × × × 0.015 11.0 5,863 5.1 56 Comparative Example 3 Silica × × × × 10.8 5,740 6.8 79

As described in detail above, the slurry composition of the present invention greatly improves the polishing rate and the polishing uniformity to enable the production of high quality mirror silicon wafers, and the semiconductor In addition to the device, it is applicable to polishing of various industrial products such as photomasks, glass discs and synthetic resins.

Claims (6)

(a) 0.1-50% by weight of fine metal oxide powder; (b) 0.1-1% by weight of alkaline base; (c) 0.01 to 1% by weight of one kind of primary to tertiary amine; (d) 0.01-1 weight percent of quaternary ammonium base; (e) 0.001 to 0.1% by weight of polyethylene glycol having a molecular weight of 15,000 to 25,000; And (f) an oxide film polishing slurry composition comprising ultrapure water as a residual amount. delete According to claim 1, wherein the fine metal oxide powder is one or more selected from the group consisting of silica, alumina, ceria, zirconia and titania, the primary particle size is 10 ~ 70nm and specific surface area is 100 ~ 300m ² / g The composition characterized in that the secondary particle size is 100 ~ 200nm and the hydroxyl concentration of the surface is 0.5 ~ 4 / nm ² . The composition of claim 1 wherein the amine is methyl amine, isopropyl amine, or diethyl amine. The composition of claim 1 wherein the quaternary ammonium base is tetramethylammonium hydroxide. delete