CN1243856A - Chemical Mechanical Polishing Composition for Semiconductor Process - Google Patents

Abstract

A chemical mechanical polishing composition for polishing metal film in semiconductor process comprises 1-25 wt% of polishing particles and 0.1-20 wt% of buffer agent as polishing promoter, wherein the buffer agent comprises a compound containing peroxodisulfate or iron (III) salt and a compound containing carboxyl or amido.

Description

Chemical Mechanical Polishing Composition for Semiconductor Process

The invention relates to a chemical mechanical polishing composition. The polishing composition of the present invention has high stability and can be effectively applied to polishing the surface of semiconductor wafers.

In the semiconductor industry, the grinding of the surface of the semiconductor wafer is a widely used technology to improve the flatness of the semiconductor wafer and the dielectric layer, so as to facilitate the manufacture of metal circuits. Generally speaking, the grinding method for manufacturing metal circuits is to place a semiconductor wafer on a rotating grinding plane equipped with a grinding head, and apply a grinding slurry containing grinding particles and an oxidizing agent on the surface of the wafer to improve grinding performance.

US Patent No. 5,225,034 discloses a chemical mechanical polishing slurry comprising AgNO ₃ , solid abrasive material, and an oxidizing agent selected from H ₂ O ₂ , HOCl, KOCl, KMgO ₄ or CH ₃ COOOH. This grinding slurry is used to grind the copper layer on the semiconductor wafer to make the copper wire on the wafer.

U.S. Patent No. 5,209,816 discloses a method for polishing an Al or Ti-containing metal layer using a chemical mechanical polishing slurry. The polishing slurry contains about 0.1-20% by volume of H ₃ PO ₄ and About 1-30% by volume _{of H2O2} .

US Patent No. 4,959,113 relates to a method of polishing metal surfaces using an aqueous abrasive composition. The aqueous abrasive composition comprises water, abrasives (such as CeO ₂ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ , SiO ₂ , SiC, SnO ₂ and TiC), and a salt comprising the periodic table of elements A metal cation of Group IIA, IIIA, IVA or IVB and an anion of chloride, bromide, iodide, nitrate, sulfate, phosphate or peroxyacid. This US patent also teaches the use of hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid to adjust its aqueous abrasive composition to pH=1-6.

US Patent No. 5,391,258 discloses an abrasive composition for polishing a compound containing silicon, silica or silicate, which includes hydrogen peroxide and potassium hydrogen phthalate in addition to abrasive particles.

U.S. Patent No. 5,114,437 relates to a polishing composition for polishing aluminum substrates, which comprises an alumina polishing agent with an average particle size of 0.2 to 5 μm and a polishing agent selected from the group consisting of chromium(III) nitrate, lanthanum nitrate, nitric acid Polishing accelerator for cerium(III) ammonium or neodymium nitrate.

U.S. Patent No. 5,084,071 relates to a method of polishing electronic component substrates using a chemical mechanical polishing slurry containing less than 1% by weight of alumina, abrasive particles (eg, SiO ₂ , CeO ₂ , SiC, Si ₃ N ₄ or Fe ₂ O ₃ ), a transition metal chelate salt (for example, ferric ammonium EDTA) as a grinding efficiency promoter, and a solvent for the salt.

US Patent No. 5,480,476 explores the influence of Ce ⁴⁺ and Zr ⁴⁺ cations on the polishing rate of SiO ₂ type abrasives.

US Patent No. 5,366,542 discloses a polishing composition comprising alumina abrasive grains and a chelating agent selected from polyaminocarboxylic acids (such as EDTA) or their sodium or potassium salts. The polishing composition may further comprise boehmite or aluminum salts.

U.S. Patent No. 5,430,370 discloses a slurry for chemical mechanical polishing of, for example, tungsten or tungsten nitride thin films, which comprises potassium ferricyanide oxidant, abrasives and water for thin films, wherein the slurry has a ratio of 2 to 4 pH.

U.S. Patent No. 5,516,346 discloses a slurry for chemical mechanical polishing of a titanium film comprising potassium fluoride and an abrasive (such as silicon oxide) at a concentration sufficient to complex with the titanium film, wherein the slurry has an pH.

WO96/16436 discloses a chemical mechanical polishing slurry comprising abrasive particles having a median particle size of less than 0.400 microns, an iron salt oxidizing agent, and an aqueous surfactant suspension of propylene glycol and methylparaben.

U.S. Patent No. 5,476,606 discloses a slurry for chemical mechanical polishing of a bare metal layer, which comprises an oxidizing agent oxidizing a metal complex such as ferric nitrate, fused alumina particles containing at least 50% γ-phase, and, for example, poly Nonionic surfactant additive of alkylsiloxane or polyoxyalkylene ether.

The polishing slurries taught by the above-mentioned prior art cannot avoid contamination of potassium ions or transition metals, or because of the use of polymer surfactants, in addition to being prone to foaming during polishing, the local polishing of the wafer surface is uneven and the roughness is increased. , and because of the poor water solubility of polymer compounds, it is very easy to cause a higher possibility of pollution.

In addition, although U.S. Patent No. 5,476,606 teaches the use of low-molecular-weight hydroxycarboxylic acids to suppress the grinding rate of oxides, thereby increasing the grinding selectivity of metal/oxides, however, hydroxycarboxylic acids cannot increase the zeta-potential of abrasive particles (i.e., zeta potential), therefore, it tends to cause instability of the slurry after addition.

To sum up, in the semiconductor manufacturing technology, there is still a search for a chemical mechanical polishing composition with higher quality to overcome the above-mentioned shortcomings faced by the polishing composition in the prior art.

The object of the present invention is to provide a chemical mechanical polishing composition for grinding metal thin films in the semiconductor manufacturing process, which comprises 1-25% by weight of abrasive particles; and 0.1-20% by weight of a buffer as a grinding accelerator, Wherein the buffering agent includes a compound containing a persulfate group or a salt containing iron (III) and a compound containing a carboxyl group or an amide group.

The present invention provides a chemical mechanical polishing composition for polishing metal thin films in semiconductor manufacturing process, which comprises 1-25% by weight, preferably 3-10% by weight of abrasive particles; and 0.1-20% by weight, preferably 6-15% by weight of the buffering agent as a grinding accelerator, wherein the buffering agent includes a compound containing persulfate group or a salt containing iron (III) and a compound containing carboxyl group or amide group. The chemical mechanical polishing composition of the present invention may further comprise 1-10% by weight, preferably 4-6% by weight of an oxidizing agent.

According to the present invention, the abrasive particles used in the abrasive composition can be commercially available, such as SiO ₂ , Al ₂ O ₃ , ZrO 2 , CeO _{2 ,} SiC, Fe ₂ O ₃ , TiO ₂ , Si ₃ N ₄ , or its mixture. These abrasive particles have the advantages of high purity, high specific surface area, and narrow particle size distribution, so they are suitable for use in chemical mechanical polishing compositions as abrasive particles.

The oxidant that can be used in the present invention is generally commercially available, such as H ₂ O ₂ , KIO ₃ , KBrO ₃ , K ₂ Cr ₂ O ₇ , K ₂ Mn ₂ O ₇ , HOCl, CH ₃ COOOH, or a mixture thereof.

According to the present invention, examples of persulfate group-containing compounds as buffer components include H ₂ S ₂ O ₈ , K ₂ S ₂ O ₈ , (NH ₄ ) ₂ S ₂ O ₈ , Na ₂ S ₂ O ₈ , or mixtures, and examples of iron(III)-containing salts as buffer components include potassium ferricyanide, ammonium iron(III) sulfate, iron(III) nitrate, or mixtures thereof.

The carboxyl compound that can be used in the buffering agent of the present invention is selected from:

其中，R₁为氢、C₁-C₆烷基或C₁-C₆羟烷基；及R₂为氢、铵离子或碱。金属离子(较佳为钾离子)。(1) Monocarboxy compounds of the following formula:

Wherein, R ₁ is hydrogen, C ₁ -C ₆ alkyl or C ₁ -C ₆ hydroxyalkyl; and R ₂ is hydrogen, ammonium ion or base. Metal ions (preferably potassium ions).

Examples of such monocarboxylic compounds include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, glycolic acid, lactic acid, and salts thereof.

其中，R₄为一单键、C₁-C₆烷基或C₁-C₆羟烷基；且R₂及R₃为氢、铵离子或碱金属离子(较佳为钾离子)。(2) Dicarboxy compounds of the following formula:

Wherein, R ₄ is a single bond, C ₁ -C ₆ alkyl or C ₁ -C ₆ hydroxyalkyl; and R ₂ and R ₃ are hydrogen, ammonium ion or alkali metal ion (preferably potassium ion).

Examples of such dicarboxylic compounds include: oxalic acid (oxalic acid), malonic acid, succinic acid (succinic acid), glutaric acid, hydroxysuccinic acid (malic acid), tartaric acid, galactaric acid and salts thereof kind.

(3) Tricarboxylic compounds, such as citric acid and its salts.

(4) Amino acid compounds such as glycine, sarcosine, dimethylglycine, alanine and salts thereof.

Examples of amide-containing compounds useful as buffer components in the present invention include formamide, acetamide, propionamide, N-methylformamide, N-methylacetamide, urea, methylurea, ethylurea, Dimethylurea and diethylurea.

The buffer additives used as grinding accelerators in the grinding compositions of the present invention provide the following advantages:

(1) Since the change of the pH value of the grinding slurry will affect the ζ-potential of the grinding particles, it is very important to maintain a stable pH value for the grinding slurry. The buffering agent used in the present invention can provide the pH value of the grinding slurry between 1.5 and 8.5, thus having the function of stabilizing the pH value of the grinding slurry.

(2) The buffer used in the present invention has excellent water solubility, so it is easy to remove without remaining on the wafer.

(3) The buffering agent used in the present invention has larger molecules, which will not penetrate into the wafer and cause contamination of the wafer.

(4) The buffering agent used in the present invention is a common chemical, which is less dangerous, so it can significantly reduce the danger to semiconductor process workers and will not pollute the environment.

(5) The individual components of the buffering agent of the present invention are compounds with lower corrosivity. However, when these compounds with lower corrosivity are used in combination according to the present invention, unexpected extremely strong corrosivity will be produced. Therefore, It can effectively improve the scraping rate of the metal film.

The abrasive composition of the present invention may contain, for example, water as a vehicle. During preparation, water may be used to slurry the abrasive composition, preferably conventional deionized water.

The abrasive composition of the present invention can be prepared by general conventional methods. For example, the abrasive particles can be added into water first, and continuously stirred with a high-shear mixer until the abrasive particles are completely suspended in the water to form a slurry. After that, continue to add water to make the abrasive particles in the slurry reach the desired solid content. According to the present invention, the solids content of the slurry is 1-25% by weight, preferably 3-10% by weight. Additives as described above are then introduced into the resulting high-purity slurry, and then, for example, ammonia water is added to control the pH of the slurry within the desired range. For example, when the metal film to be ground is a W film, the pH value can be controlled between 1.5-2.5, preferably between 1.8-2.3; when the metal film to be ground is an Al film, the pH value Control between 3.0-4.5, preferably between 3.8-4.2; and when the metal film to be polished is a Cu film, control the pH value between 5.5-9.0, preferably between 6.0-7.0. Finally, the slurry is filtered to obtain the abrasive composition of the present invention. The preparation process of the abrasive composition of the present invention can be carried out at any appropriate temperature, preferably at a temperature of 20-40°C.

The following examples will further illustrate the present invention, but are not intended to limit the scope of the present invention. Any modifications and changes that can be easily achieved by those skilled in the art are included in the scope of the present invention. Example 1

The silicon dioxide produced by Degussa is used in the present embodiment, which has the following properties:

(1) The pH value of the 5% aqueous suspension is between 3.6-4.3;

(2) The specific surface area is 40-130m ² /g; and

(3) The specific gravity is ≤0.7g/ml.

At room temperature, 5 kg of the above silicon dioxide was added to 20 kg of deionized water, and the mixture was continuously stirred with a high shear force mixer until the silicon dioxide was completely suspended in the water and became a slurry. Then add 20 kg of deionized water to dilute the slurry so that the solids content of the slurry is slightly more than 11%. Then 1.5 kg of oxalic acid (oxalic acid) and 3 kg of ammonium iron(III) sulfate were added to the slurry, which quickly dissolved in the slurry. After continuous stirring for 3 hours, the pH of the slurry was adjusted to about 2.0 with NH ₄ OH. The slurry was filtered to produce a chemical mechanical abrasive composition of the present invention having a solids content of about 10%. The grinding test results of the obtained grinding composition are listed in Table 1 below. Example 2

The same preparation steps as in Example 1 were repeated, but oxalic acid was replaced with 1.5 kg of formic acid. The grinding test results of the obtained grinding composition are listed in Table 1 below. Example 3

The same preparation steps as in Example 1 were repeated, except that 5 kg of alumina (manufactured by Sumitomo Chemical Co., model AKP-G008) was used instead of silicon dioxide, and 1.5 kg of citric acid was used instead of oxalic acid. The grinding test results of the obtained grinding composition are listed in Table 1 below. Example 4

The same preparation steps as in Example 3 were repeated, but 1.5 kg of hydroxyacetic acid was used instead of citric acid. The grinding test results of the obtained grinding composition are listed in Table 1 below. Comparative example 1

The same system as in Example 1 was repeated, but iron ammonium sulfate (III) was not added. The grinding test results of the obtained grinding composition are listed in Table 1 below. Comparative example 2

The same preparation steps as in Example 3 were repeated, but iron ammonium sulfate (III) was not added. The grinding test results of the obtained grinding composition are listed in Table 1 below. grinding test

A. Instrument: PIEC/Westch472

B. Conditions: Pressure: 5psi

 Temperature: 25°C

  Spindle speed: 45rpm

  Platen speed: 42rpm

  Pedestal Type: Rodel IC 1400

Slurry flow rate: 150ml/min

C. Chip:

(1) W film: purchased from Silicon Valley Microelectronics, Inc., a film of 0.8 microns ± 5% is deposited on a 6-inch silicon wafer by CVD technology

(2) Ti film: purchased from Silicon Valley Microelectronics, Inc., a film of 0.5 microns ± 5% is deposited on a 6-inch silicon wafer by CVD technology

(3) TiN film: purchased from Silicon Valley Microelectronics, Inc., a film of 0.5 microns ±% is deposited on a 6-inch silicon wafer by CVD technology

(4) Oxide film: It is silicon dioxide thermally generated on silicon substrate entrusted to the National Nano Component Laboratory.

D. Slurry: Take the slurry obtained in the above-mentioned Examples 1-4 and Comparative Example 1-2, add the same volume of aqueous solution containing 2% by weight of H ₂ O ₂ , and carry out the test after uniform stirring for 15 minutes. Grinding test process:

Before and after grinding, it is necessary to measure the thickness of the film with a film thickness tester. The sheet resistance of the metal film is measured with a four-point probe, and then the thickness of the film is converted by the following formula:

T×R=Resistivity Wherein, T is the film thickness (A), and R is the sheet resistance (Ω/cm ² ), for various metal thin films, the resistivity (Ω/cm) is a constant.

The present invention adopts the RS75 type machine of KLA-Tencor Company to measure the film thickness of metal layer.

The film thickness of the oxide can be measured directly by optical principles. The present invention uses the SM300 type machine of KLA-Tencor Company to measure the film thickness of thermal oxide. The grinding rate is measured as follows:

First measure the film thickness T ₁ of the metal layer with the above-mentioned RS75 machine, use the above-mentioned slurry in the above example, grind for 1 minute according to the above-mentioned operating conditions, and then use the Evergreen Model 10X machine from Solid State Equipment Corporation to clean the machine table After cleaning the wafer, blow dry the wafer. Then measure the film thickness T ₂ of the metal layer with an RS75 machine. T ₁ -T ₂ is the polishing rate of the metal layer.

In addition, the film thickness T ₃ of the thermal oxide was measured by SM300 machine. After grinding for 1 minute with the same slurry and the same operating conditions, the film thickness was measured as T ₄ after cleaning. T ₃ -T ₄ is the polishing rate of thermal oxide.

The test data obtained are listed in Table 1 below.

Table 1 Example removal rate W(/min) Ti(/min) TiN(/min) SiO ₂ (/min) Example 1 4145 2976 983 237 Example 2 4315 2921 950 201 Example 3 5008 2337 3523 102 Example 4 5273 1368 3899 210 Comparative example 1 572 247 687 167 Comparative example 2 1161 1198 1695 233 Example 5

The same preparation steps as in Example 3 were repeated, except that 3 kg of formic acid was used instead of citric acid, and 2 kg of (NH ₄ ) ₂ S ₂ O ₈ was used instead of ammonium iron(III) sulfate, and the pH value was adjusted to 4.0 with ammonia water. The grinding test results of the obtained grinding composition are listed in Table 2 below. Example 6

The same preparation steps as in Example 5 were repeated, except that formic acid was replaced with 3 kg of glycine, and the pH value was adjusted to 4.0 with ammonia water. The grinding test results of the obtained grinding composition are listed in Table 2 below. Example 7

The same preparation steps as in Example 5 were repeated, except that 3 kg of formamide was used instead of formic acid, and the pH value was adjusted to 4.0 with ammonia water. The grinding test results of the obtained grinding composition are listed in Table 2 below. Comparative example 3

The same preparation steps as in Example 5 were repeated, except that (NH ₄ ) ₂ S ₂ O ₈ was not added. The grinding test results of the obtained grinding composition are listed in Table 2 below. grinding test

A. Instrument: IPEC/Westech472

B. Condition: Pressure: 5psi

  Temperature: 25C

  Spindle speed: 45rpm

    Platen speed: 42rpm

Pedestal Type: Rodel Politex

Slurry flow rate: 150ml/min

C. Wafer:

(1) Al thin film: purchased from Silicon Valley Microelectronics, Inc., a thin film of 0.85 microns ± 5% is deposited on a 6-inch silicon wafer by CVD technology, and the purity is Al: 98.5%, Si: 1%, Cu: 0.5%

(2) Ti film: purchased from Silicon Valley Microelectronics, Inc., a film of 0.5 microns ± 5% is deposited on a 6-inch silicon wafer by CVD technology

(3) TiN film: purchased from Silicon Valley Microelectronics, Inc., a film of 0.5 microns ± 5% is deposited on a 6-inch silicon wafer by CVD technology

(4) Oxide film: It is entrusted to the National Nano Components Laboratory to thermally generate silicon dioxide on a silicon substrate.

D. Slurry: Take the slurry obtained in the above-mentioned Examples 5-7 and Comparative Example 3, mix it with an aqueous solution containing 5% by weight of H ₂ O ₂ in the same volume, and test it after uniform stirring for 15 minutes

The grinding test procedure is as described above, and the obtained test data are listed in Table 2 below.

Table 2 Example removal rate Al(/min) Ti(/min) TiN(/min) SiO ₂ (/min) Example 5 3944 1704 3318 129 Example 6 4682 1223 3380 117 Example 7 3552 2279 4454 112 Comparative example 3 1705 673 3237 192 Example 8

The same preparation steps as in Example 5 were repeated, except that the pH value was adjusted to 6.5 with aqueous ammonia. The grinding test results of the obtained grinding composition are listed in Table 3 below. Example 9

The same preparation steps as in Example 6 were repeated, but the pH value was adjusted to 6.5 with ammonia water. The grinding test results of the obtained grinding composition are listed in Table 3 below. Example 10

The same preparation steps as in Example 7 were repeated, but 1.5 kg of acetamide was used instead of formic acid. The grinding test results of the obtained grinding composition are listed in Table 3 below. Comparative example 4

The same preparation steps as in comparison 3 were repeated, but the pH value was adjusted to 6.5 with ammonia water. The grinding test results of the obtained grinding composition are listed in Table 3 below. grinding test

A. Instrument: IPEC/Westech472

B. Conditions: Pressure: 5psi

 Temperature: 25°C

  Spindle speed: 45rpm

  Platen speed: 42rpm

  Pedestal type: Rodel 1400

  Slurry flow rate: 150ml/min

C. Wafer:

(1) Cu film: purchased from Silicon Valley Microelectronics, Inc., a film of 0.85 microns ± 5% is deposited on a 6-inch silicon wafer by CVD technology

(2) Ti film: purchased from Silicon Valley Microelectronics, Inc., a film of 0.5 microns ± 5% is deposited on a 6-inch silicon wafer by CVD technology

(3) TiN film: purchased from Silicon Valley Microelectronics, Inc., a film of 0.5 microns ± 5% is deposited on a 6-inch silicon wafer by CVD technology

(4) Oxide film: It is entrusted to the National Nano Components Laboratory to thermally generate silicon dioxide on a silicon substrate.

D. Slurry: Take the slurry obtained in the above-mentioned Examples 8-11 and Comparative Example 4, add the same volume to an aqueous solution containing 5% by weight H ₂ O ₂ , and test after uniform stirring for 15 minutes

The grinding test procedure is as described above, and the obtained test data are listed in Table 3 below.

table 3 Example removal rate Cu(/min) Ti(/min) TiN(/min) SiO ₂ (/min) Example 8 7430 1804 3322 194 Example 9 7217 1665 4340 203 Example 10 4001 1471 3677 211 Comparative example 4 7337 598 1829 189

It can be seen from the above examples that the polishing composition of the present invention can effectively improve the polishing efficiency of metal thin films, especially Ti and TiN thin films, and improve the polishing selectivity of Cu/Ti and Cu/TiN.

Claims (10)

1. A chemical mechanical polishing composition for grinding metal thin films in semiconductor manufacturing processes, which comprises 1-25% by weight of abrasive particles: and 0.1-20% by weight of a buffer as a polishing accelerator, wherein the buffer Including compounds containing persulfate groups or salts containing iron (III) and compounds containing carboxyl groups or amido groups. 2. The composition according to claim 1, comprising 3-10% by weight of the grinding particles; and 6-15% by weight of the buffer as a grinding accelerator. 3. The composition according to claim 1 or 2, wherein the persulfate group-containing compound is selected from the group consisting of H ₂ S ₂ O ₈ , K ₂ S ₂ O ₈ , (NH ₄ ) ₂ S ₂ O ₈ , Na ₂ The group consisting of S ₂ O ₈ and its mixtures. 4. The composition according to claim 1 or 2, wherein the iron(III)-containing salt is selected from the group consisting of potassium ferricyanide, ammonium iron(III) sulfate, iron(III) nitrate and mixtures thereof group. 5. The composition according to claim 1 or 2, wherein the carboxyl-containing compound is selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, hydroxyacetic acid, lactic acid, oxalic acid, propanoic acid, acid, succinic acid, glutaric acid, hydroxysuccinic acid, tartaric acid, galactaric acid and citric acid and their salts, and mixtures of these acids and/or their salts. 6. The composition according to claim 1 or 2, wherein the amido-containing compound is selected from the group consisting of formamide, acetamide, propionamide, N-methylformamide, N-methylacetamide, urea, formamide The group consisting of urea, ethyl urea, dimethyl urea and diethyl urea. 7. The composition according to claim 1 or 2, further comprising 1-10% by weight of an oxidizing agent. 8. The composition according to claim 6, comprising 4-6% by weight of said oxidizing agent. 9. The composition according to claim 1 or 2, wherein the abrasive is selected from the group consisting of SiO ₂ , Al ₂ O ₃ , ZrO ₂ , CeO ₂ , SiC, Fe ₂ O ₃ , TiO ₂ , Si ₃ N ₄ or a group consisting of mixtures thereof. 10. The composition according to claim 6, wherein the oxidizing agent is selected from the group consisting of H ₂ O ₂ , KIO ₃ , KBrO ₃ , K ₂ Cr ₂ O ₇ , K ₂ Mn ₂ O ₇ , KMnO ₄ , HOCl, CH ₃ The group consisting of COOOH and its mixtures.