KR20080003485A - Slurry composition and method of mechanical chemical polishing using the same - Google Patents

Abstract

A slurry composition for chemical mechanical polishing is provided to increase the polishing selectivity to a polysilicon layer and silicon oxide layer, thereby improving the polishing efficiency in a process for polishing a silicon oxide layer in the presence of a polysilicon layer as a polishing resist layer. A slurry composition comprises: 0.001-5 wt% of a seria polishing agent; 0.001-0.1 wt% of a polymeric additive; 0.001-0.1 wt% of a pH(potential of hydrogen) modifier; and the balance amount of water, wherein the pH modifier includes an acid in such a manner that the pH of the total composition is maintained at 2-7. The pH modifier includes hydrochloric acid, nitric acid or an organic acid. The polymeric additive includes polyethylene glycol.

Description

Slurry Composition and Method of mechanical chemical polishing using the same

1 and 2 are schematic process cross-sectional views for explaining a chemical mechanical polishing method according to an embodiment of the present invention.

3 to 9 are schematic cross-sectional views illustrating a method of forming a nonvolatile memory device using the chemical mechanical polishing method illustrated in FIGS. 1 and 2.

Explanation of symbols on the main parts of the drawings

100 semiconductor substrate 102 polysilicon film

104: silicon oxide film 106: silicon oxide film pattern

The present invention relates to a slurry composition and a polishing method using the same. More specifically, the present invention relates to a slurry composition having an etch selectivity with respect to a polysilicon film and a silicon oxide film layer, and a polishing method using the same.

The semiconductor device is generally formed by repeatedly performing unit processes such as a deposition process, a patterning process, an etching process, and a polishing process.

Among the above processes, a polishing process is performed to planarize the surface of the thin films deposited on the substrate semiconductor substrate. Usually, the chemical mechanical polishing process is used as the polishing process.

In the chemical mechanical polishing process, a semiconductor substrate to be subjected to a polishing process is mounted, a slurry composition including an abrasive is improved between the semiconductor substrate and the polishing pad, and the semiconductor substrate is rotated and pressed while being in contact with the polishing pad. And a step of flattening the surface of the semiconductor substrate by rotation.

That is, the surface projections of the polishing pad and the polishing pad included in the polishing slurry are mechanically rubbed with the surface of the semiconductor substrate to mechanically polish the surface of the semiconductor substrate, and at the same time, the chemical composition included in the slurry composition and the surface of the semiconductor substrate. Chemical reaction of the semiconductor substrate is a step of chemically removing the surface.

The polishing efficiency of the chemical mechanical polishing process is determined by the chemical mechanical polishing equipment, the composition of the slurry composition, the type of polishing pad, and the like. In particular, the composition of the slurry composition has a significant effect on polishing efficiency.

For the slurry composition of the same composition, the polishing rate of the film may vary according to the properties of the film, and the degree of polishing of the film may be adjusted using the difference in the polishing rate. In particular, the degree of polishing may be adjusted by the difference in polishing rate between oxide films, nitride films, polysilicon films, or metal films widely used in semiconductor devices.

Among such slurry compositions, in particular, slurry compositions having a high polishing rate for polysilicon films and low polishing rates for oxide films have been widely used, and slurry compositions having a high polishing selectivity for the films are well known.

In recent years, however, as semiconductor devices have been highly integrated, there has been a need for a slurry composition having the opposite polishing selectivity.

For example, in the manufacture of a nonvolatile memory device having a U-shaped floating gate, several polishing processes are performed to form the floating gate. In particular, in the process of polishing the oxide film deposited on the polysilicon film for use as the floating gate, it is required to have a high polishing rate for the oxide film and a low polishing rate for the polysilicon film.

However, until now, the development of a slurry composition having a high polishing selectivity with respect to the polysilicon film to the extent that the polysilicon film can be used as the polishing stop film has been insignificant.

One object of the present invention for solving the above problems is to provide a slurry composition having a high polishing selectivity with respect to the polysilicon film.

Another object of the present invention to provide a chemical mechanical polishing method using the slurry composition.

According to an aspect of the present invention for achieving the above object, the slurry composition, 0.001 to 5% by weight of ceria abrasive, 0.001 to 0.1% by weight of polymer additives, 0.001 to 0.1% by weight of hydrogen ion index regulator (pH) and It includes excess water, and the hydrogen ion index regulator comprises an acid (acid) to maintain the hydrogen ion index of the total composition of 2 to 7.

The hydrogen ion index regulator may include hydrochloric acid, nitric acid or organic acid. The polymer additive may include poly ethylene glycol (PEG). The PEG may have a molecular weight of 10,000 to 1,000,000.

According to an aspect of the present invention for achieving the above another object, in the chemical mechanical polishing method, to form a polishing stopper film made of polysilicon on the substrate. A polishing target film made of silicon oxide is formed on the polishing stopper film. 0.001 to 5% by weight of a ceria abrasive for polishing the polishing target film, 0.001 to 0.1% by weight of a polymer additive, 0.001 to 0.1% by weight of a hydrogen ion index modifier (pH), and excess water. The modifier comprises an acid to maintain the hydrogen ion index of the entire composition at 2 to 7 while providing a slurry composition on the polishing pad while contacting the surface of the polishing pad surface with the surface of the polishing target film to perform polishing. The polishing target film is polished until the blocking film is exposed.

An etching selectivity of the polishing stopper layer and the polishing target layer may be 1: 120 or more.

According to the present invention as described above, in the polishing of the silicon oxide film by adding a polymer additive and a hydrogen ion index regulator containing an acid to maintain the hydrogen ion index of the composition 2 to 7 by selecting the high etching of the silicon oxide film and polysilicon film May have rain.

Hereinafter, a slurry composition and a chemical mechanical polishing method using the same according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Slurry  Composition

The slurry composition according to the present invention is a slurry composition used during polishing of a silicon oxide film through a chemical mechanical polishing process.

The slurry composition shows a high polishing rate for the silicon oxide film and at the same time a significantly low polishing rate for the polysilicon film. Therefore, when the polishing process is performed using the slurry composition on a structure having a polysilicon film formed on the bottom and a silicon oxide film formed thereon, the silicon oxide film is effectively polished using the polysilicon film as the polishing stopper film. can do.

The slurry composition of the present invention comprises a ceria abrasive, a polymer additive, water and a hydrogen ion index regulator.

Ceria (CeO ₂ ) abrasive is used as the abrasive used in the slurry composition of the present invention. When the ceria abrasive is used, the polishing rate for the polysilicon film is slow while maintaining a high polishing rate for the silicon oxide film.

In this case, the amount of the ceria abrasive affects the polishing efficiency during the polishing process. In more detail, when the content of the ceria abrasive included in the slurry composition is less than 0.001% by weight, poor polishing dispersion may occur due to a decrease in the chemical mechanical polishing efficiency of the silicon oxide film. On the other hand, when the content of the ceria abrasive exceeds 5% by weight, the removal rate of the polysilicon film used as the etch stop film is increased.

Accordingly, the ceria abrasive is included in about 0.001 to 5% by weight, more preferably in about 0.1 to 3.5% by weight based on the total slurry composition.

The slurry composition of the present invention comprises a polymer additive, the polymer additive comprising a hydrophobic group and a hydrophilic group. The polymer additive includes Poly Ethylene Glycol (PEG).

The polymer additive serves to protect the polysilicon film which is a hydrophobic film during the polishing process using the slurry composition of the present invention.

Here, when the polishing process is performed using the slurry composition composed of only the ceria abrasive, the silicon oxide film is polished efficiently, but the polishing rate with respect to the polysilicon film is also fast. Therefore, it is not suitable for application to the process of polishing a silicon oxide film using a polysilicon film as a polishing stopper film.

The hydrophobic group of the PEG faces the polysilicon film and the hydrophilic group faces the slurry composition. Accordingly, the hydrophobic group of the PEG serves to protect the polysilicon film from the ceria abrasive by adsorbing on the surface of the polysilicon film. That is, the PEG prevents the ceria abrasive particles from directly contacting the polysilicon film by forming a passivation layer on the surface of the polysilicon film, thereby significantly slowing the polishing rate of the polysilicon film. At the same time, since the PEG contains a hydrophilic group, the polishing rate for the silicon oxide film is not lowered. Therefore, the slurry composition of the present invention has a high polishing rate for the silicon oxide film while the polysilicon film has a significantly low polishing rate due to the protective effect by the PEG.

Here, the polishing rate of the polysilicon film may vary depending on the amount and molecular weight of the polymer additive. In more detail, when the content of the polymer additive is less than 0.001% by weight of the slurry composition, the removal rate of the polysilicon film used as the etch stopper during the polishing process of the silicon oxide film is increased. On the other hand, when the content of the polymer additive is more than 0.1% by weight, the problem that the polishing process time of the silicon oxide film is increased. Therefore, the slurry composition preferably contains 0.001 to 0.1% by weight of the polymer additive.

In addition, the polishing selectivity for the polysilicon film is changed according to the molecular weight of the PEG. More specifically, when the molecular weight of the PEG is less than 10,000, the molecular weight is too small to add a relatively large amount of PEG may change the physical properties of the slurry composition. On the other hand, when the molecular weight of the PEG is more than 1,000,000, the silicon oxide film may be over-etched. Thus, the PEG preferably has 10,000 to 1,000,000, more preferably 100,000 to 500,000.

The slurry composition of the present invention includes a hydrophobicity index regulator (pH regulator), and the hydrophobicity index regulator serves to adjust the hydrophobicity index of the entire slurry composition to an appropriate range. In particular, when a ceria abrasive is used as the abrasive, when the slurry composition has acidity, the polishing selectivity between the polysilicon film and the silicon oxide film is excellent.

As the hydrophobic index adjuster, an organic acid series or a basic hydrophobic index modifier such as hydrochloric acid and nitric acid is used. At this time, the hydrogen ion index of the slurry composition of the present invention is adjusted in the range of about 2 to 7.

The slurry composition of the present invention contains extra solvent. The solvent is added for the flowability of the slurry composition, using di-ionized water.

According to an embodiment of the present invention, the slurry composition of the present invention may further include a dispersant for ceria abrasives. The dispersant for the ceria abrasive serves to improve the polishing efficiency of the ceria abrasive. The dispersant for the ceria abrasive includes a polymer material such as poly acrylic acid. The polymer material included in the dispersant for the ceria abrasive serves to adsorb the ceria abrasive particles to disperse the ceria abrasive particles by electrostatic repulsive force and steric hindrance. Thereby, the dispersibility of ceria abrasive grains becomes high and it can prevent the phenomenon which aggregates a slurry composition. In addition, the dispersant for ceria abrasives also serves to reduce the noise during the polishing process by increasing the viscosity of the slurry composition.

The content of the dispersant may be adjusted according to the proportion of the ceria abrasive, but it is generally included in about 0.5 to 3.5% by weight.

When the polysilicon film and the silicon oxide film are polished using the slurry composition having the composition as described above, the polishing selectivity of the polysilicon film and the silicon oxide film is about 1: 120, which is very high.

Hereinafter, the slurry composition of the present invention will be described in more detail through Examples and Comparative Examples.

Slurry  Preparation of the composition

Example  One

A slurry composition was prepared comprising 0.7 wt% ceria abrasive, 0.01 wt% PEG, 0.01 wt% maleic acid, and excess water. At this time, the ceria abrasive was used by mixing HSachi5's HS8005A ceria particles and HS8102GP additive. In addition, PEG with a molecular weight of 500,000 was used.

Example  2

A slurry composition was prepared comprising 0.5 wt% ceria abrasive, 0.02 wt% PEG, 0.001 wt% nitric acid and excess water. At this time, the ceria abrasive was used by mixing HSachi5's HS8005A ceria particles and HS8102GP additive. In addition, PEG with a molecular weight of 500,000 was used.

Comparative example  One

A slurry composition was prepared comprising 0.7 wt% ceria abrasive, 0.05 wt% potassium hydroxide and excess water. At this time, the ceria abrasive was used by mixing HSachi5's HS8005A ceria particles and HS8102GP additive.

Comparative Example 2

A slurry composition was prepared comprising 0.7 wt% ceria abrasive, 0.05 wt% sodium hydroxide and excess water. At this time, the ceria abrasive was used by mixing HSachi5's HS8005A ceria particles and HS8102GP additive.

Comparative Example 3

A slurry composition was prepared comprising 0.7 wt% ceria abrasive, 0.01 wt% PEG, 0.05 wt% potassium hydroxide and excess water. At this time, the ceria abrasive was used by mixing HSachi5's HS8005A ceria particles and HS8102GP additive. In addition, PEG with a molecular weight of 500,000 was used.

Comparative Example 4

A slurry composition was prepared comprising 0.7 wt% ceria abrasive, 0.01 wt% PEG, 0.05 wt% sodium hydroxide and excess water. At this time, the ceria abrasive was used by mixing HSachi5's HS8005A ceria particles and HS8102GP additive. In addition, PEG with a molecular weight of 500,000 was used.

The types and contents of the substances included in the slurry compositions according to Examples 1 and 2 and Comparative Examples 1 to 4 are shown in Table 1 below.

TABLE 1

Ceria (% by weight) PEG (% by weight) Hydrogen ion index regulator (% by weight) Example 1 0.7 0.01 Maleic Acid 0.01 Example 2 0.5 0.02 Nitrate 0.01 Comparative Example 1 0.7 Potassium Hydroxide 0.05 Comparative Example 2 0.7 Sodium Hydroxide 0.05 Comparative Example 3 0.7 0.01 Potassium Hydroxide 0.05 Comparative Example 4 0.7 0.01 Sodium Hydroxide 0.05

Evaluation of Polishing Selection Ratios of Examples and Comparative Examples

In order to evaluate the polishing selectivity depending on the presence or absence of the polymer additive included in the slurry composition, a semiconductor substrate on which polishing target films were deposited was prepared. A polysilicon film is deposited on the semiconductor substrate as a polishing stop film, and a silicon oxide film, which is a polishing target film, is deposited on the polysilicon film. Each film was subjected to a chemical mechanical polishing process using the slurry compositions prepared according to Examples 1 and 2 and Comparative Examples 1 and 3. At this time, the chemical mechanical polishing process was performed using AMAT MIRRA polisher.

When the above chemical mechanical processes were performed on the silicon oxide film and the polysilicon film using the slurry compositions according to Examples 1 and 2 and Comparative Examples 1 and 3, respective polishing selectivities are shown in Table 2 below.

TABLE 2

Silicon Oxide Polishing Rate (Å / min) Polysilicon Film Polishing Speed (Å / min) Polishing selectivity Example 1 3108 21 150: 1 Example 2 2869 19 150: 1 Comparative Example 1 2670 667 4: 1 Comparative Example 2 2710 534 5: 1 Comparative Example 3 2901 145 20: 1 Comparative Example 4 2919 139 21: 1

Referring to Table 2, in the chemical mechanical polishing process using the slurry compositions according to Examples 1 and 2, the polishing rate was about 2850 to 3200 Å / min for the silicon oxide film, and about 19 for the polysilicon film. To a polishing rate as low as 21 kPa / min. The slurry compositions according to Examples 1 and 2 exhibit a polishing selectivity of at least 150: 1.

On the other hand, in the chemical mechanical polishing process using the slurry compositions according to Comparative Examples 1 and 2, a high polishing rate of 2670-2710 Pa / min was shown for the silicon oxide film, but a polishing rate of 667-534 Pa / min was obtained for the polysilicon film. Indicated. The slurry compositions according to Comparative Examples 1 and 2 do not contain PEG, so that the polysilicon film is partially polished while the silicon oxide film is polished, thereby exhibiting a low polishing selectivity of 5: 1.

In addition, in the chemical mechanical polishing process using the slurry compositions according to Comparative Examples 3 and 4, the polishing rate was 2901-2910 Pa / min for the silicon oxide film, but the polishing rate was about 139-145 Pa / min for the polysilicon film. Indicated. The slurry compositions according to Comparative Examples 3 and 4 contain PEG, so that the polysilicon film is protected while the silicon oxide film is polished to have a higher etching selectivity than the slurry compositions according to Comparative Examples 1 and 2. However, the slurry compositions according to Comparative Examples 3 to 4 are basic slurry compositions and exhibit an etching selectivity of 20: 1 lower than that of the slurry compositions according to Examples 1 and 2.

Therefore, the slurry composition includes a PEG polymer additive, and a hydrogen ion index within the range of 2 to 7 may be used to obtain a high etching selectivity of 120: 1 between the silicon oxide film and the polysilicon film.

Polishing method

1 to 2 are cross-sectional views illustrating a chemical mechanical polishing method for selectively polishing a silicon oxide film using a slurry composition according to an embodiment of the present invention.

Referring to FIG. 1, a hydrophobic polysilicon film 102 is formed on a semiconductor substrate 100. The silicon oxide film 104 may be formed directly on the semiconductor substrate 100 or may be formed through another structure such as an electrode, a conductive film, a conductive film pattern, an insulating film, or an insulating film pattern. In addition, the polysilicon film 102 may have a concave-convex structure as shown.

A hydrophilic silicon oxide film 104 is formed on the polysilicon film 102. The silicon oxide film 104 is formed to have a thickness sufficiently filling the lower polysilicon film 102.

2, at least a portion of the silicon oxide film 104 is removed by a polishing process such as a chemical mechanical polishing process until the polysilicon film 102 is exposed.

Specifically, a slurry composition including a ceria abrasive, a polymer additive, water, and a hydrogen ion index regulator is provided on the polishing pad. The silicon oxide film 104 is removed by polishing the silicon oxide film 104 by bringing the polishing pad surface into contact with the silicon oxide film 104. In this case, the polishing process is performed while the polishing pad, the silicon oxide film 104 and the semiconductor substrate 100 on which the polysilicon is formed are rotated. In this case, the rotations may be in the same direction or may be opposite to each other. In addition, the semiconductor substrate 100 is in contact with the polishing pad in a pressed state. Accordingly, the silicon oxide is chemically polished by the slurry composition and mechanically polished by the rotation and pressurization.

Since the description of the slurry composition is as described above, a detailed description thereof will be omitted.

The slurry composition shows a high polishing rate for the silicon oxide film 104 and a significantly low polishing rate for the polysilicon film 102. This is because the silicon oxide film 104 is hydrophilic and the polysilicon film 102 is hydrophobic, and thus shows a high polishing rate with respect to the silicon oxide film 104 by the polymer additive included in the slurry composition. A low polishing rate is shown for the polysilicon film 102.

Therefore, when the structure having the polysilicon film 102 formed on the bottom and the silicon oxide film 104 formed thereon is polished using the slurry composition, the polysilicon film 102 is used as the polishing stopper film. Thus, the silicon oxide film 104 may be selectively polished.

The polishing process may be performed until the top surface of the polysilicon film 102 is exposed. In this case, since the slurry composition has a polishing selectivity of about 1: 120 or more with respect to polysilicon and silicon oxide, the polysilicon film may be polished for a predetermined time after the polysilicon film 102 is exposed. 102 is hardly removed.

During the polishing process, the silicon oxide film pattern 106 is formed as a result of the polishing of the silicon oxide film 104. The silicon oxide layer pattern 106 may be removed by a dry etching process or a wet etching process in a subsequent process.

The polishing method may be applied to a manufacturing process of various semiconductor devices such as device isolation layers, gate structures, wiring structures, pad structures, contacts, and capacitors.

Method of manufacturing nonvolatile memory device

3 through 9 are cross-sectional views illustrating a method of manufacturing a nonvolatile memory device using the chemical mechanical polishing method illustrated in FIGS. 1 and 2.

Referring to FIG. 3, a pad oxide film 202 is formed on a semiconductor substrate 200. The pad oxide film 202 is provided to prevent direct contact between the mask film 204 and the semiconductor substrate 200 to be formed later, and may be formed by thermal oxidation.

A mask film 204 is formed on the pad oxide film 202. The mask layer 204 may be formed using silicon nitride.

Referring to FIG. 4, a photoresist pattern (not shown) is formed on the mask layer 204, and the mask layer 204 and the pad oxide layer 202 are patterned using the photoresist pattern as an etching mask. The mask pattern 208 and the pad oxide film pattern 206 are formed. After the mask pattern 208 and the pad oxide layer pattern 206 are formed, the photoresist pattern is removed by an ashing or strip process.

By using the mask pattern 208 and the pad oxide layer pattern 206 as an etching mask, the pad oxide layer 202 and the semiconductor substrate 200 exposed by the mask pattern 208 are sequentially etched to form the trench 210. To form.

An isolation layer (not shown) is formed on the mask pattern 208 to completely fill the trench 210. The device isolation layer may be formed using silicon oxide having excellent gap fill characteristics. The device isolation layer may be formed using, for example, silicon oxide such as BPSG, PSG, BSG, USG, SOG, TEOS, PE-TEOS, HDP-CVD oxide, or the like.

Subsequently, the upper part of the device isolation layer is polished until the upper surface of the mask pattern 208 is exposed to form the preliminary device isolation layer pattern 212.

Referring to FIG. 5, the exposed mask pattern 208 is removed. According to an exemplary embodiment, the mask pattern 208 may be removed using a material having a polishing selectivity with respect to the preliminary isolation layer pattern 212. For example, when the mask pattern 208 includes a silicon nitride film and the preliminary isolation layer pattern 212 includes silicon oxide, the mask pattern 208 may be removed by a wet etching process using a phosphate diluent. .

Next, the pad oxide film pattern 206 is removed. The pad oxide layer pattern 206 may be removed by a wet etching process. As a result, an opening 215 for forming a floating gate is formed between the preliminary isolation layer patterns 212.

When the pad oxide layer pattern 206 is removed by a wet etching process, a portion of the sidewall of the preliminary device isolation layer pattern 212 may be etched.

Referring to FIG. 6, a tunnel oxide layer 216 is formed on the semiconductor substrate 200 exposed between the preliminary isolation layer patterns 212. The tunnel oxide layer 216 may be formed of silicon oxide. In addition, the tunnel oxide film 216 may be formed by a process such as a thermal oxidation process or a chemical vapor deposition process.

Subsequently, a polysilicon film 218 is formed along the surfaces of the tunnel oxide film 216 and the preliminary isolation layer pattern 212. The polysilicon film is converted into a floating gate electrode through a subsequent process.

The polysilicon film 218 is formed to a thickness such that the inside of the opening is not completely filled. The polysilicon film 218 may be a polysilicon film doped with impurities.

A silicon oxide film 220 is formed on the polysilicon film 218 to completely fill the openings. The silicon oxide film 220 includes a BPSG, PSG, BSG, USG, SOG, TEOS, PE-TEOS, and HDP-CVD oxide.

Referring to FIG. 7, the silicon oxide film 220 is partially removed using a polishing process such as a chemical mechanical polishing process so that the top surface of the polysilicon film 218 is exposed. That is, the silicon oxide film 220 formed on the polysilicon film 218 is removed using the polysilicon film 218 as the polishing stopper film.

When polishing the polysilicon film 218 and the silicon oxide film 220, the slurry composition used in the polishing process has a high polishing rate with respect to the silicon oxide film 220, while with respect to the polysilicon film 218. It is required to have a low polishing rate. Since the polysilicon included in the polysilicon film 218 is hydrophobic, and the silicon oxide included in the silicon oxide film 220 is hydrophilic, a polishing process using a slurry composition having a high polishing selectivity relative to the hydrophobic film is performed.

Specifically, the slurry composition includes a ceria abrasive, a polymer additive, water, and a hydrogen ion index regulator. Since the description of the slurry composition is as described above, a detailed description thereof will be omitted.

Referring to FIG. 8, a portion of the exposed polysilicon layer 218 is removed until the upper surface of the preliminary isolation layer pattern 212 is exposed to form a node-separated preliminary floating gate electrode 226.

Next, although not shown, a second photoresist pattern (not shown) is formed on the preliminary floating gate electrode 226 and the silicon oxide layer 220. The second photoresist pattern is formed to mask a region where the floating gate electrode 226 is to be formed.

Referring to FIG. 9, an isolated U-shaped floating gate electrode 228 is formed by etching the preliminary floating gate electrode 226 using the second photoresist pattern as an etching mask.

After forming the floating gate electrode 228, the second photoresist pattern is removed by performing an ashing and strip process.

The silicon oxide film pattern remaining inside the floating gate electrode 228 is removed. In addition, a portion of the preliminary isolation layer pattern 212 that contacts the floating gate electrode 228 and the sidewall is removed. By the above process, the device isolation layer pattern 230 having a height lower than that of the preliminary device isolation layer is completed.

By removing portions of the silicon oxide layer pattern and the preliminary isolation layer, the upper, inner and outer side surfaces and the rear surface of the floating gate electrode 228 are exposed.

The dielectric layer 232 is continuously formed on the exposed top surfaces of the floating gate electrode 228 and the device isolation layer pattern 230. The dielectric film 232 may be formed to have a stacked shape of an oxide film, a nitride film, and an oxide film.

The floating gate electrode 228 has a pattern shape in which the floating gate electrode 228 is isolated in a U-shape, and is exposed to the front and rear and inner and outer sides of the floating gate electrode 228 on which the dielectric film 232 is formed. The deposition area of is increased. This can sufficiently increase the coupling ratio in the cells of the nonvolatile memory device.

Subsequently, a second conductive layer (not shown) is formed on the dielectric layer 232. The second conductive layer may be formed in a multilayer structure by depositing a polysilicon layer doped with impurities and then depositing a metal or metal silicide layer.

Subsequently, a photolithography process is performed on the second conductive layer, the dielectric layer 232, and the floating gate electrode 228 to include a nonvolatile structure including a control gate electrode, a dielectric layer pattern, a floating gate electrode 228, and a tunnel oxide layer pattern. The gate structure of the memory device is completed.

As described above, according to a preferred embodiment of the present invention, by performing a chemical mechanical polishing process using a slurry composition which is acidic and contains a polymer additive such as PEG, the polishing selectivity of the polysilicon film and the silicon oxide film is increased. You can. Therefore, the polysilicon film can be effectively applied to a polishing process using the polishing stop film and the silicon oxide film as the polishing target film.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (6)

Ceria abrasive from 0.001 to 5% by weight; 0.001 to 0.1 weight percent polymer additive; Hydrogen ion index regulator (pH) 0.001 to 0.1 wt%; And Contains excess water, The hydrogen ion index regulator is a slurry composition, characterized in that it comprises an acid (acid) to maintain the hydrogen ion index of the entire composition at 2 to 7. The slurry composition of claim 1, wherein the hydrogen ion index regulator comprises hydrochloric acid, nitric acid or organic acid. The slurry composition of claim 1, wherein the polymer additive comprises poly ethylene glycol (PEG). The slurry composition of claim 3, wherein the PEG has a molecular weight of 10,000 to 1,000,000. Forming a polishing stopper film made of polysilicon on the substrate; Forming a polishing target film made of silicon oxide on the polishing stopper film; And 0.001 to 5% by weight of a ceria abrasive for polishing the polishing target film, 0.001 to 0.1% by weight of a polymer additive, 0.001 to 0.1% by weight of a hydrogen ion index modifier (pH), and excess water. The modifier comprises an acid to maintain the hydrogen ion index of the entire composition at 2 to 7 while providing a slurry composition on the polishing pad while contacting the surface of the polishing pad surface with the surface of the polishing target film to perform polishing. Polishing the polishing target film until the stopper film is exposed. The chemical mechanical polishing method of claim 5, wherein an etching selectivity ratio of the polishing stopper film and the polishing target film is 1: 120 or more.

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