KR100497411B1 - Colloidal silica slurry with uniformed big sized particle for chemical mechanical polishing and method for manufacturing of the same - Google Patents

Abstract

The present invention relates to a colloidal silica slurry useful for oxides or STI-CMP having uniform large particles, and to a method for producing the same. More specifically, CMP having uniform large particles based on colloidal silica used for CMP. It relates to a colloidal silica slurry useful in the process of the present invention and a method for preparing the same.

In the present invention, even when a large particle size of 120 nm or more is produced, the particle size distribution is uniform, and the particle size is large, so that the conventional abrasive slurry can be polished at 12.5 wt% of the abrasive. Even when the content is 10% by weight, the polishing rate is very good because the polishing rate is equal to or higher than the polishing performance of the existing polishing slurry. It shows long-term stability that does not occur due to aggregation and precipitation even after the above process. In addition, fumed silica contains a large amount of environmentally harmful substances such as polymers, surfactants, and amines, but the colloidal silica of the present invention contains little such chemicals, which is useful for environmentally friendly CMP. Silica is an advantage.

Description

Colloidal Silica Slurry with Uniformed big sized particle for Chemical Mechanical Polishing and Method for manufacturing of the same}

The present invention relates to a colloidal silica slurry useful for chemical mechanical polishing (hereinafter abbreviated as 'CMP') having uniform large particles, and a method for preparing the same, and more particularly, to a CMP. The present invention relates to a colloidal silica slurry useful for chemical mechanical polishing having uniform large particles based on colloidal silica, and a method of manufacturing the same.

The CMP method was developed in the late 1980s by IBM in the US as a new polishing process that combines mechanical removal and chemical removal into a single processing method. In the conventional mechanical polishing method, a modified layer is formed. It is a defect on a semiconductor chip, and chemical polishing does not produce a deteriorated layer, but a planarized shape, that is, shape precision, cannot be obtained, and only a smooth surface can be obtained. Polishing the object by combining the advantages of these two processes is the basic concept of CMP.

CMP application process includes: ① Silicon wafer wafer mirror mirror polishing-Silicon wafer manufacturing process ② Oxide CMP process-Polishing of insulating film for planarization purposes ③ Metal (W) CMP process-Polishing rate ( Replacement of tungsten plug process for improving yield ④ Shallow trench isolation (STI) CMP process-Oxide and nitride polishing, nitride selectivity to oxide for narrow isolation (oxide to nitride selectivity), minimizing oxide dishing ⑤ AI CMP process (oxidation and polishing of Al to Al ₂ O ₂ )-Substituting metal etching process using damascene structure, by chemical attack dishing (dishing) about minimize ⑥ AI CMP step (the step of grinding by oxidation of Al to Al ₂ O ₂₎ - metal etch process replaced by the wavy structure ⑦ polysilicon CMP process-frame poly plug (pre poly plug (3P) type A selection step of an oxide on the polysilicon also (poly Si to oxide selectivity) ensuring, after good cleaning: scratches and the like to minimize the effects and the oxide surface (Post Cleaning the material removal process after the polishing of the wafer surface).

InterLayer Dielectric (ILD) CMP and metal CMP must be applied continuously on all surfaces of the device layer and form the global planarization of each layer to obtain three-dimensional shape.

A schematic view of a general CMP process with reference to the accompanying drawings, Figure 1 is a schematic diagram of a general CMP process, Figure 2 relates to a schematic diagram of a general CMP equipment, the wafer (wafer) having a pad (mechanical polishing element) Abrasive table) and slurry (polishing buffer with chemical polishing elements), and the pad is attached to the polishing table for simple rotational movements, and the head part performs both rotational and oscillating movements at a constant pressure. Pressurize. The wafer is mounted on the head part by surface tension or vacuum, and the surface of the head and the pad are brought into contact with each other by the self-load of the head part and the pressing force applied, and the slurry which is the processing liquid between the minute gaps (pores of the pad) between the contact surfaces The flow is mechanically removed by the abrasive particles in the slurry and the surface protrusions of the pad, and chemically by the chemical components in the slurry. In the CMP process, contact is made from the upper part of the device protrusion by the pressing force between the pad and the wafer, and the pressure is concentrated on this part to have a relatively high surface removal rate. Is removed.

The most important part of the chemistry of CMP is the role of abrasives. Despite the low content of abrasives, which is directly related to semiconductor production, the technique of increasing the polishing rate is a reality only possible with chemicals. Silica is widely used for semiconductor abrasives around the world, and mainly divided into fumed silica and colloidal silica. The most important factors as semiconductor abrasives are polishing rate, nicks and uniformity, and at present, the scratches and uniformity have been improved through many research and development, but the technique of increasing the polishing rate directly related to semiconductor production was possible only with chemicals.

Therefore, the overall function of the abrasive is increased, so that the polishing rate is high, the defect rate is low even at a low abrasive content, and even a particle size of 120 to 130 nm shows a very uniform particle size distribution, and it can be used stably for a long time. There is an urgent need to develop an abrasive for a semiconductor wafer.

Therefore, the present invention was devised to solve the above problems, in the present invention, in the manufacture of a semiconductor abrasive, the conventional polishing slurry can be polished at 12.5% by weight of the abrasive, but the polishing slurry of the present invention Even when the content is 10% by weight, the effect of the polishing rate is good since the polishing rate is equal to or higher than the polishing performance of the existing polishing slurry, and even particle size distribution of 120 to 130nm is characterized by the uniform particle size distribution. It is an object of the present invention to provide a colloidal silica slurry useful for chemical mechanical polishing having uniform large particles and a method for producing the same.

It is still another object of the present invention that the colloidal silica slurry contains little environmentally harmful substances because it is excellent in maintaining stability compared to fumed silica even without adding a surfactant, which is a stabilizer to stabilize the suspension slurry. The present invention provides a colloidal silica slurry useful for chemical mechanical polishing having a large uniform particle size, and a method of manufacturing the same.

The present invention for achieving the above object relates to a colloidal silica slurry useful for CMP having uniform large particles, and a method for producing the same, and more particularly, uniform large particles based on colloidal silica used for CMP. It relates to a colloidal silica slurry useful for CMP having a and a method for producing the same.

Generally, a slurry is used for a semiconductor abrasive, and it is mainly classified into fumed silica and colloidal silica according to its manufacturing method. In the present invention relates to a colloidal silica abrasive, first, comparing the two slurries as follows.

Colloidal silica is manufactured by ion-change method of silicic acid solution and has the disadvantage that it is relatively expensive and contains a lot of metal contamination. However, colloidal silica has the advantage of uniform and stable particles. On the contrary, fumed silica has low particle uniformity and Stability is not more than six months.

Hereinafter, a colloidal silica slurry useful for CMP according to the present invention and a method for preparing the same will be described in detail with reference to the accompanying drawings. 3 is a flow chart of the preparation of a colloidal silica slurry having large uniform particles according to the present invention.

V) diluting the sodium silicate by mixing 5 to 10% by weight of sodium silicate and 90 to 95% by weight of deionized water in a sodium silicate dilution tank (dilution of sodium silicate);

Ii) separately diluting hydrochloric acid in a hydrochloric acid dilution tank with 20 to 30% by weight of 35% hydrochloric acid in 70 to 80% by weight of deionized water (dilution of hydrochloric acid);

Iii) regenerating the cation exchange resin with the diluted aqueous hydrochloric acid solution prepared in step ii) and washing with deionized water (cation exchange resin regeneration step);

Iii) preparing an active silicic acid in the form of oligomer by passing the dilute aqueous sodium silicate solution prepared in step iii) through a solution of sodium silicate in a cation exchange resin tower regenerated in step iii), and Removing impurities (silic acid preparation and impurity removal step);

Iii) Silic acid in the form of oligomer is transferred to the reactor at a rate of 50 l / hr to 200 l / hr, and potassium hydroxide is added to 1 to 20% by weight of the silicic acid solution at a temperature of 80 to 200 ° C. for 0.5 to 6 hours. Growing the nuclei of the colloidal silica particles while forming the particles into a particle state (particle nucleation and particle growth steps);

vi) cooling the colloidal silica suspension grown in the particulate state to room temperature and concentrating the colloidal silica using a concentrated membrane in a concentration tank until the concentration of colloidal silica becomes 5 to 40% by weight (colloidal silica suspension concentration step);

vii) storing the stock solution prepared in step vi) in a reservoir (storage step);

Ⅷ) Filtering step (filtering step)

After final packaging, the colloidal silica slurry useful for CMP is prepared by repeating steps iv) to vii) two to four times until the size of the colloidal silica particles is 120 to 130 nm.

In step ii), the preferred amount of hydrochloric acid is 20 to 30% by weight. When the amount of hydrochloric acid is less than 20% by weight, the regeneration of the cation exchange resin is not entirely performed. In this case, the pH of the silicic acid produced while sodium silicate passes through the ion exchange resin is higher than 4, and the silicic acid is in a gel state. If the amount exceeds 30% by weight, the amount of hydrochloric acid remaining in the cation exchange resin is too high, so that the sodium silicate passes through the cation exchange resin column and the pH of the silicic acid is too low (pH 1 or less) due to the remaining hydrochloric acid. Excessive chlorine in the process, namely the particle generation step, prevents the particles from being produced properly and becomes prominent.

In the steps iii) to iii), the diluted hydrochloric acid aqueous solution regenerates the cation resin, and the hydrochloric acid aqueous solution after the regeneration is purified in a water treatment process. The cation resin is regenerated by the ion substitution method between hydrogen ions (H ⁺ ) of hydrochloric acid and sodium ions (Na ⁺ ) of the cation resin. At this time, the ions (H ⁺ , Na ⁺ ) remaining after substitution during the regeneration of the cation resin are washed off in the washing process, and the water after washing is purified in a separate water treatment process. Impurities such as metal compounds contained in the diluted aqueous sodium silicate solution passing through the regenerated cation resin tower are removed by a cation exchange resin.

In step iv), the generation of the oligomeric form of silicic acid and impurities are removed, and the nuclei of colloidal silica particles are formed to have a size of 3 nm or less in the state of silicic acid.

Potassium hydroxide in step v) is a base for colloidal silica particle growth and stabilization through condensation reaction with an activated silicic acid solution in the form of oligomer in which impurities formed in step iv) are removed. The addition amount is 1 to 20% by weight of the activated silicic acid suspension is added. When the amount of potassium hydroxide added is less than 1% by weight, excess activated silicic acid is reacted with respect to the base, thereby inhibiting unreacted colloidal silica particle growth, and when exceeding 20% by weight, activated silicium When the base is added in excess of the acid, it may cause dissolution after colloidal silica particle growth and may impair colloidal silica stability such as aggregation between particles. In addition to the potassium hydroxide, one of ammonia water (NH ₄ OH), sodium hydroxide (NaOH) or sodium silicate may be selected and added. The addition amount is the same as the potassium hydroxide addition amount.

And in step v), the colloidal silica suspension formed in step iv) is introduced into the reactor at a rate of 50 l / hr to 200 l / hr based on 1 ton of the reactor. If the inflow rate of the colloidal silica suspension is less than 50 l / hr, it is a problem in terms of stability due to an increase in the aggregation phenomenon between the silica particles, and if it exceeds 200 l / hr, the overall broadness of the small silica particles and the large particles due to unreacted It has a broad particle distribution.

And the reaction temperature is preferably 80 ℃ to 200 ℃, if the temperature is less than 80 ℃ condensation reactivity of the base and the activated silicic acid is significantly reduced to fall below the particle growth for the purpose of the present invention, 200 ℃ or more In this case, colloidal silica stability due to aggregation between silica particles is inhibited.

In step vi) colloidal silica is preferably concentrated to 5 to 40% by weight so that it can be diluted according to the needs of the consumer.

In the step vii), to grow the colloidal silica particles of the desired size, the steps v) to iii) are repeated 2 to 4 times to grow the size of the colloidal silica particles to 120 to 130 nm. When the size of the silica particles is less than 120 nm, the effect of mechanical polishing on the oxide layer of the wafer, which is the object of the present invention, is insignificant. When the size of the silica particles exceeds 130 nm, the particles are scratched when the oxide layer of the wafer is polished. Problems arise in development and stability of the slurry.

Hereinafter, a method for preparing a colloidal silica slurry useful for CMP of the present invention will be described in detail with reference to Examples.

(Examples 1 to 3)

A dilute solution of sodium silicate was prepared by dissolving 10% by weight of sodium silicate in 90% by weight of deionized water. Separately, 20% by weight of 35% hydrochloric acid solution is diluted in 80% by weight of deionized water, and then the cation exchange resin tower is regenerated with this diluted aqueous hydrochloric acid solution. The dilute solution of sodium silicate prepared above is passed through the regenerated cation exchange resin tower to remove impurities contained in the dilute solution of sodium silicate and to form activated silicic acid in the form of oligomers of 3 nm or less in size. Activated silicic acid of the oligomer form prepared here was transferred to a reactor at a rate of 100 l / hr based on 1 ton and reacted at a temperature of 120 ± 5 ° C. for 3 hours to grow particles of colloidal silica and then colloidal silica Concentrate with a concentrated membrane until the concentration of is 20% by weight. The suspension slurry was transferred to the reactor again, and the reaction and concentration steps were repeated three more times to grow particles to 120-130 nm in size, and finally, three samples of 25% by weight of the sample prepared by filtering were collected.

(Comparative Examples 1 to 3)

Silica particles are prepared at very high temperatures, i.e. by burning silicon tetrachloride (SiCl ₄ ) with water or CO ₂ gas, and the solution is prepared by adding sieving fumed silica preferentially to KOH or NH ₄ OH in purified water. It is made with an alkali of about pH 10 to 11 and then 25% by weight of fumed silica is dispersed, and accordingly a dispersant or dispersion stabilizer is added at 0.1% by weight or less. In addition, fumed silica has polyacrylamides to surround the particle surface to prevent scratches caused by semiconductor polishing because the shape of the particles is not round and the surface is sharp. Add high molecular compound. Three 25 wt% of the prepared samples were collected.

(Experimental conditions)

CMP device: AMAT Mirra-Mesa (USA)

Polishing Pad: IC1400 / Suba IV (Rodel)

Surface plate rotation speed: 87 rpm

Carrier Speed: 93 rpm

Grinding Slurry Feed Speed: 160mL / min

Main air: 200 hpa

Wafer: PE-TEOS (8 ")

Samples taken to meet the test conditions were used diluted 50% by weight in deionized water. As a result of measuring the polishing rate, the defect, the in-plane uniformity (Non-uniformity) by the test conditions, the contents of the following [Table 1].

                                 TABLE 1

division Example Comparative Example One 2 3 One 2 3 Polishing rate 2800 2820 2810 2320 2360 2350 Defect, number 2 One 2 3 2 4 In-plane uniformity (%) 3 3 3 2 2 2

According to the results of [Table 1], Examples 1 to 3 have a higher polishing rate of 2,800 Pa or more due to a slurry having a large particle size of 120 to 150 nm, while Comparative Examples 1 to 3 are usually about 2,320 to 2,360 Pa. It shows the removal rate, and it can be seen that the particle level (scratch, defect) and in-plane uniformity do not show a big difference between colloidal silica and fumed silica. And Figure 4 is a result of photographing Example 1 with a transmission electron microscope (TEM), showing the size of the colloidal silica particles 122.03nm, 122.57nm, 123.84nm.

The present invention relates to a colloidal silica slurry useful for oxides or STI-CMP having uniform large particles, and to a method for producing the same. More specifically, CMP having uniform large particles based on colloidal silica used for CMP. It relates to a colloidal silica slurry useful in the process of the present invention and a method for preparing the same.

In the present invention, even when a large particle size of 120 nm or more is produced, the particle size distribution is uniform, and the particle size is large, so that the conventional abrasive slurry can be polished at 12.5 wt% of the abrasive. Even when the content is 10% by weight, the polishing rate is very good because the polishing rate is equal to or higher than the polishing performance of the existing polishing slurry. It shows long-term stability that does not occur due to aggregation and precipitation even after the above process. In addition, fumed silica contains a large amount of environmentally harmful substances such as polymers, surfactants, and amines, but the colloidal silica of the present invention contains little such chemicals, which is useful for environmentally friendly CMP. Silica is an advantage.

1 is a schematic of a typical CMP process.

2 is a schematic diagram of a typical CMP equipment.

3 is a flow chart of the preparation of a colloidal silica slurry having large uniform particles according to the present invention.

Figure 4 shows a TEM picture of the slurry particles according to the present invention.

Claims (3)

V) diluting the sodium silicate by mixing 5 to 10% by weight of sodium silicate and 90 to 95% by weight of deionized water in a sodium silicate dilution tank (dilution of sodium silicate); Ii) separately diluting hydrochloric acid in a hydrochloric acid dilution tank with 20 to 30% by weight of 35% hydrochloric acid in 70 to 80% by weight of deionized water (dilution of hydrochloric acid); Iii) regenerating the cation exchange resin with the diluted aqueous hydrochloric acid solution prepared in step ii) and washing with deionized water (cation exchange resin regeneration step); Iii) preparing an active silicic acid in the form of oligomer by passing the dilute aqueous sodium silicate solution prepared in step iii) through a solution of sodium silicate in a cation exchange resin tower regenerated in step iii), and Removing impurities (silic acid preparation and impurity removal step); Iii) Silic acid in the form of oligomer is transferred to the reactor at a rate of 50 l / hr to 200 l / hr, and potassium hydroxide is added to 1 to 20% by weight of the silicic acid solution at a temperature of 80 to 200 ° C. for 0.5 to 6 hours. Growing the nuclei of the colloidal silica particles while forming the particles into a particle state (particle nucleation and particle growth steps); vi) cooling the colloidal silica suspension grown in the particulate state to room temperature and concentrating the colloidal silica using a concentrated membrane in a concentration tank until the concentration of colloidal silica becomes 5 to 40% by weight (colloidal silica suspension concentration step); vii) storing the stock solution prepared in step vi) in a reservoir (storage step); viii) filtering (filtering step); Colo useful for chemical mechanical polishing with uniform large particles, characterized in that the steps iii) to vii) are repeated two to four times until the size of the colloidal silica particles is 120 to 130 nm. Method for preparing silica slurry this month. The method of claim 1, wherein the calcium hydroxide in step (iii) is selected from ammonia water (NH ₄ OH), sodium hydroxide (NaOH) or sodium silicate can be added instead of a chemical having a uniform large particles, characterized in that Process for preparing colloidal silica slurry useful for mechanical polishing. By the method of claim 1 through step iii) to iii), Colloidal silica particles useful for chemical mechanical polishing with uniformly large particles, characterized in that the size of the colloidal silica particles is prepared by repeating steps 2 to 4 two times until the size is 120 to 130nm. Silica slurry.