JP2001226666A - Abrasive grain and polishing liquid, method of polishing thereof, and method of producing semiconductor apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce scratches occurring in polishing of a thin film since flattening of the thin film formed on a wafer is indispensable so as to attain a high integration of semiconductor element. SOLUTION: The surface of a material to be polished is chemically and mechanically flattened by using a polishing solution obtained by dispersing complex particles composed of an inorganic substance and a nonelectrolytic organic substance having >=500 molecular weight as abrasive grains into a solvent and adding a polishing promoter to the dispersion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical mechanical polishing method. The present invention relates to a device manufacturing method.

[0002]

2. Description of the Related Art Along with the high integration of semiconductor devices, the device structure is becoming three-dimensional due to multi-layer wiring and three-dimensional capacitor cells in a memory LSI. However, since the three-dimensional technology of a structure in which thin films are stacked on multiple layers results in a step inside the semiconductor element, the step may cause a disconnection of a wiring pattern or an exposure failure due to a short focal depth margin in a photolithography process. generate.

[0003] In order to solve the above-mentioned problems in the process, it is essential to flatten the surface of a thin film having a step formed on a semiconductor substrate. For this purpose, a semiconductor thin film having a step on the order of microns is required to have a so-called chemical mechanical polishing method disclosed in Japanese Patent Application Laid-Open No. (Chemical Mecha
It is necessary to use a method called nical polishing (CMP for short).

In order to perform the above-mentioned chemical mechanical polishing, it is necessary to use a polishing liquid containing abrasive grains (fine particles), and the techniques disclosed therein will be described below.

(1) Japanese Patent Application Laid-Open No. 9-296161 or Japanese Patent Application Laid-Open No. 10-44047 discloses polishing liquids. As abrasive grains dispersed in these polishing liquids,
SiO ₂ , Al ₂ O ₃ , CeO _{2 and the} like are used.

(2) Japanese Patent Application Laid-Open No. 7-86216 discloses that an organic polymer is used as abrasive grains.

(3) Further, Japanese Patent Application Laid-Open No. 10-168431 discloses a composite polishing liquid in which polyions are adsorbed to polishing abrasive grains such as Al ₂ O ₃ . The polyions that are highly attracted to the surface of the abrasive particles exhibit Langmuir-type adsorption behavior, and the polymer adheres smoothly to the surface of the abrasive particles until coating with a monolayer is achieved. It is described that it acts as follows.

[0008]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-open No. Hei 9-2
In the case where an oxide film or the like formed on a semiconductor substrate is chemically and mechanically polished using a polishing liquid described in JP-A-96161 or JP-A-10-44047, the number of agglomerated abrasive grains in the polishing liquid is large. Therefore, a scratch (scratch) is easily generated on the polished surface. As a result, there is a problem that the formed scratches cause an electrical short-circuit of the semiconductor device, thereby lowering the yield of the semiconductor device.

In addition, when the abrasive grains described in JP-A-7-86216 are used, the abrasive grains themselves are soft,
In addition, there is a disadvantage that the polishing rate is low. Therefore, C
Since the throughput of the process requiring MP technology decreases,
It must be said that it is extremely difficult to apply the abrasive grains to an actual mass production process.

When the polishing liquid described in Japanese Patent Application Laid-Open No. 10-168431 is used, the abrasive grains to which poly ions have been adsorbed enter the recesses and act to protect the recesses. Will polish the projections.
Therefore, the surface of the object to be polished is polished by the non-adsorbed abrasive grains of poly ions, and the abrasive grains cause scratches on the surface. Further, even if the abrasive grains to which a part of the poly ions are adsorbed are involved in polishing, the effect of reducing scratches is insufficient because the poly ion adsorption layer is a monomolecular layer.

An object of the present invention is not only to contribute to a reduction in the number of scratches formed on the surface of the object to be polished, but also to secure a sufficient polishing rate even when applied to an actual mass production process. Another object of the present invention is to provide a polishing abrasive grain and a polishing liquid having excellent flattening performance with respect to the surface of an object to be polished, a polishing method therefor, and a method for manufacturing a semiconductor device using the same.

[0012]

The inventors of the present invention have conducted intensive studies on the object to be polished, polishing abrasive grains, a polishing solution, a polishing method, and the like. As a result, the formation of scratches on the surface of the object to be polished is small, A polishing abrasive, a polishing liquid, and a polishing method excellent in flattening performance have been found.

Specifically, the abrasive grains of the present invention include an inorganic substance and an organic substance, and the organic substance is a non-electrolyte.

Further, the inorganic substance is a particle and an organic layer is formed on the surface of the particle, or the organic substance is a particle and an inorganic layer is formed on the surface of the particle.

Further, the abrasive grains of the present invention include an inorganic substance and an organic substance, and the inorganic substance and the organic substance are at least chemically bonded.

The organic material layer has a molecular weight of 5
It was made of a polymer having at least 00.

In the present invention, a polishing slurry comprising an inorganic substance and an organic substance which is a non-electrolyte is dispersed in a solvent, and a polishing accelerator is added to the solvent to form a polishing liquid. I did it.

Further, according to the present invention, at least on the surface of an object to be polished, a polishing liquid containing an abrasive and an organic substance which is a non-electrolyte dispersed in water and a polishing accelerator added thereto is supplied. A polishing method for chemically and mechanically planarizing the surface of the object to be polished.

The present invention further includes a film forming step of forming a thin film above the semiconductor substrate, a polishing step of polishing the thin film, and a cleaning step of cleaning the semiconductor substrate. Dispersing abrasive grains consisting of and an organic substance that is a non-electrolyte in water, and supplying a polishing liquid with a polishing accelerator added to at least the surface of the thin film,
A method of manufacturing a semiconductor device wherein the surface of the thin film is made to be flattened chemically and mechanically, wherein the thin film is formed above a semiconductor substrate having a step.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a view conceptually showing a cross-sectional structure of abrasive grains for explaining a first embodiment. First, a method for forming the above abrasive grains will be described.

A commonly used stirrer, thermometer, N
₂ Flask with gas inlet tube and cooling tube (volume 1
0 liter), 5 kg of a 20% aqueous dispersion of SiO ₂ particles having an average particle size of 0.1 μm, and 2,2 ′ as a polymerization initiator
-2 g of azobis (2-aminodipropane) dihydrochloride, 60 g of methoxypolyethylene glycol acrylate as a monomer, 60 g of methyl methacrylate, and 20 g of γ-methacryloxypropyltrimethoxysilane,
Sufficiently the inside of the reaction system of the flask was N ₂ substitution.

Next, the whole flask is heated to 80 ° C., stirred for 3 hours, and cooled to room temperature.

Subsequently, the solvent in the flask was adjusted to pH 11 using a 30% aqueous NH ₃ solution, and an organic layer was formed on the surface of the inorganic particles by graft polymerization or the like.

After the above-described steps, the two-layer structure shown in FIG. 1 is used, in which the core material 1 is made of SiO ₂ , and the outer shell material 2 formed outside the core material is an organic polymer. A polishing liquid in which grains are dispersed is completed. The polishing solution has an abrasive concentration of 13.5%.

The inorganic particles described in this embodiment are:
It is not limited to iO ₂ , but also includes Al ₂ O ₃ , C
eO ₂ , SiC, ZrO ₂ , diamond, MnO ₂ ,
The particles are selected from Mn ₂ O _{3 and the} like, and may have a spherical or pulverized shape.

The polymerization initiator used in this example is 2,2'-azobis (2-aminodipropane)
An azo compound having a polar group such as dihydrochloride or 4,4′-azobis (4-cyanopentanoic acid) may be used. Furthermore, after treating the powder surface with an isocyanate compound such as 2,4-tolylene diisocyanate, an azo compound having a polar group or a peroxide may be added.

As the monomer used in this embodiment, a vinyl monomer is used. For example, (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n- Amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, isohexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) Acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, Enoxyethyl (meth) acrylate, methoxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminoethyl (Meth) acrylate quaternary compound, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl phthalic acid,
(Meth) acrylate monomers such as glycidyl (meth) acrylate, ethylene glycol di (meth) acrylate, dithylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, Di (meth) acrylate monomers such as polypropylene glycol di (meth) acrylate and 2,2-bis [4- (methacryloxydiethoxy) phenyl] propane; trimethylolpropane tri (meth) acrylate; trimethylol methane tri ( Tri (meth) acrylate monomers such as meth) acrylate, tetra (meth) acrylate monomers such as tetramethylolmethanetetra (meth) acrylate, dimethyl (meth) acrylamide, N, N-
Dimethylaminopropyl (meth) acrylamide, (meth) acryloylmorpholine, N-vinylpyrrolidone,
(Meth) acrylamide monomers such as 2-acrylamide-2-methylpropanesulfonic acid, styrene monomers such as styrene, alkyl-substituted styrene and divinylbenzene, γ- (meth) acryloylalkyl trialkoxysilane, γ- Silicone monomers such as (meth) acryloylalkyl dialkoxysilane, trialkoxyvinylsilane, dialkoxyalkylvinylsilane, etc., ethylene monomers such as ethylene, isobutylene, methacrylonitrile, maleic acid, maleic diester, fumaric acid, Unsaturated dicarboxylic acids such as fumaric acid diester, itaconic acid, itaconic acid diester, citraconic acid, citraconic acid diester, diester monomers, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimet Include polymerizable metal alkoxide such Shishiran, but not limited thereto.

The organic layer may be a copolymer selected from at least one kind of monomer described above.

If necessary, a surfactant such as a dispersant may be added to the above polishing liquid.

Next, in order to confirm the performance of the polishing liquid of this embodiment, the polishing liquid obtained through the above-described steps was used to perform chemical mechanical polishing of the object to be polished under the following polishing conditions. Was done. Then, the number of scratches on the surface of the polished body after polishing was measured.

(1) Polishing conditions Polishing object: Silicon wafer (8 inches) with a thickness of about 0.5 mm formed on the surface with an oxide layer of a thickness of about 1.2 μm Polishing apparatus: Self-made apparatus Polishing cloth: Rodel IC1400 Polishing liquid supply amount: 200 ml / min. Polishing time: 3 minutes. (2) Evaluation of the number of scratches After polishing of the object to be polished, defects on the polished surface are detected by using a well-known visual inspection device. The location was observed in detail using a well-known electron microscope (SEM), and the number of scratches formed on the surface was measured.

Table 1 shows the occurrence of scratches when the polishing rate of the object to be polished was changed. As a comparative example, a polishing liquid generally used in a polishing liquid, for example, a commercial product containing about 10% of silica abrasive grains and adjusted to pH 11 by adding aqueous ammonia to the polishing liquid, was used in the same manner as in this example. The results (comparative example) performed under the conditions are also shown in Table 1.

Table 1 Relationship between polishing conditions and number of scratches generated Example 1 Number of scratches (pieces / cm ² ) Polishing rate (nm / min) No. 1 0.1 230 No. 2 0.3 250 No. 3 0.2 240 No. 4 0.2 240 No. 5 0.1 235 Comparative Example 1 0.8 250 Comparative Example 2 0.8 235明 ら か As is clear from the above results, when the surface of the silicon wafer is polished using the polishing liquid of this example, the number of scratches formed on the surface is reduced as compared with the conventional method. The number of scratches can be further reduced by lowering the polishing rate.

Next, a second embodiment will be described.

First, the use of a flask (volume: 10 liters) equipped with a stirrer, thermometer, dropping funnel and cooling tube is the same as in the case of the first embodiment. In this flask, polymethyl methacrylate particles having an average particle diameter of 0.1 μm were dispersed in 5 liters of an ethanol solution of tetraethoxysilane, and ethanol was further added to prepare a diluted solution.

Next, the entire flask was heated to 60 to 65 ° C., and 30% NH ₃ as a hydrolysis catalyst was stirred while stirring.
By gradually dropping the aqueous solution, an inorganic layer is formed on the surface of the particles made of the organic polymer, and has a two-layer structure as shown in FIG. 1, wherein the core substance 1 is an organic polymer,
A dispersion of abrasive grains whose outer shell material 2 was SiO 2 was prepared.

Further, water is added dropwise with stirring, and the heating temperature is raised to replace the ethanol in the reaction system with water. Then, by adjusting the pH to 11 using a 30% NH ₃ aqueous solution, the abrasive grain concentration is 13.
5% polishing liquid was obtained.

As the inorganic layer, for example, SiO ₂ , A
Those synthesized by a sol-gel method such as l ₂ O ₃ , CeO ₂ , and ZrO ₂ are used.

As the organic polymer particles used in this embodiment, water-insoluble particles are used. For example, organic polymer particles composed of a polymer synthesized from at least one of the vinyl monomers shown in the first embodiment are used, but are not limited thereto. is not.

The hydrolysis catalyst may be an acid or an alkali. For example, hydrochloric acid or an aqueous ammonia solution, which can be easily removed, is preferable.

If necessary, a surfactant such as a dispersant may be added to the polishing liquid.

Using the polishing liquid thus obtained,
The object to be polished was subjected to chemical mechanical polishing under the polishing conditions used in the first example, and the number of scratches formed on the polished surface was measured.

As a result, as shown in the first embodiment,
It has been found that the number of scratches formed on the surface of the object to be polished is reduced as compared with the conventional method.

Next, a third embodiment will be described.

The stirrer, the thermometer, and the stirrer described in the first embodiment
In a flask (volume of 10 liters) equipped with a dropping funnel and a cooling tube, an ethanol solution of tetraethoxysilane 5 was added.
200 g of polyvinylpyrrolidone was dissolved in 1 liter, and ethanol was added thereto to prepare a diluted solution.

Next, the entire flask was heated to 60 to 65 ° C., and a 30% NH ₃ aqueous solution was gradually added dropwise with stirring, so that the organic and inorganic hybrid particles as shown in FIG. Thus, a dispersion of abrasive grains was prepared.

Further, while stirring the mixture, water was added dropwise, the heating temperature was raised, ethanol in the reaction system was replaced with water, and the pH was adjusted to 11 using a 30% NH ₃ aqueous solution. A polishing liquid having a concentration of 13.5% was obtained.

As the inorganic component, for example, SiO ₂ , Al
Those synthesized by a sol-gel method such as ₂ O ₃ , CeO ₂ , and ZrO ₂ are used.

As the organic component, an organic polymer composed of a polymer synthesized from at least one of the vinyl monomers shown in the first embodiment or poly (2-ethyl) is used. Any polymer may be used as long as it is a polymer soluble in water or an organic solvent of a polymer such as oxazolidine, polyethylene oxide, and polyalkylene oxide, and is not limited thereto.

The hydrolysis catalyst may be an acid or an alkali. For example, hydrochloric acid or an aqueous ammonia solution, which can be easily removed, is preferred.

If necessary, a surfactant such as a dispersant may be added to the polishing liquid.

Using the polishing liquid thus obtained,
An experiment similar to that described in the first embodiment was performed.
As a result, as in the case of the first embodiment, it was found that the number of scratches formed on the surface of the object to be polished was reduced as compared with the conventional method.

Next, a fourth embodiment will be described.

[0055] Similar to the case described in the first embodiment, a stirrer, a thermometer, a dropping funnel, N ₂ inlet, into equipped with a cooling tube flask (volume 10 L), ethanol tetraethoxysilane 200 g of vinylpyrrolidone and 2,2'-azobis (2
-Aminodipropane) dihydrochloride (2 g) was dissolved, and ethanol was added to obtain a diluted solution.

Next, after the inside of the reaction system is sufficiently substituted with N ₂ ,
This is heated to 60-65 ° C and stirred. And
By gradually dropping a 30% aqueous NH ₃ solution while generating an organic polymer, a dispersion of abrasive grains composed of hybrid particles of an organic substance and an inorganic substance as shown in FIG. 2 was prepared.

Further, water was added dropwise while stirring the mixture, the heating temperature was increased, the solvent in the ethanol in the reaction system was replaced with water, and the pH was adjusted to 11 with a 30% aqueous NH ₃ solution, whereby the abrasive particle concentration was reduced. A polishing liquid of 13.5% was obtained.

As the inorganic component, for example, SiO ₂ , Al
Those synthesized by a sol-gel method such as ₂ O ₃ , CeO ₂ , and ZrO ₂ are used.

As the organic component, at least one of the vinyl monomers and the polymerization initiator shown in the first embodiment is used.

The hydrolysis catalyst may be an acid or an alkali, but for example, hydrochloric acid or an aqueous ammonia solution which is easy to remove is preferred.

[0061] If necessary, a surfactant such as a dispersant may be added to the polishing liquid.

Using the polishing liquid thus obtained,
As in the first embodiment, an experiment of chemical mechanical polishing of the object to be polished was attempted. As a result, as in the case of the first embodiment, it was found that the number of scratches formed on the surface of the object to be polished was reduced as compared with the conventional method.
In the first to fourth embodiments described above, the polishing abrasive grains and the polishing liquid have been described, but the embodiments are not limited thereto.

In the above-described embodiment, the molecular weight of the organic polymer was set to 500 or more. However, the polishing abrasive grains and the polishing liquid of the above-described embodiment were prepared by using an organic low molecule having a molecular weight of 500 or less. Even when the same chemical mechanical polishing as described above was performed, the number of scratches formed on the surface of the object to be polished was not improved as compared with the conventional method. In addition, even if a polishing liquid in which organic abrasive grains and inorganic abrasive grains described in this example were simply mixed was used, no improvement effect was obtained as compared with the conventional method.

Further, in the first and second embodiments, the polishing abrasive grains in which the thickness of the outer shell of the substance existing on the outside is about 10% of the particle radius of the core substance has been described. It is not limited to this.

Next, a method of manufacturing a semiconductor device according to a fifth embodiment will be described.

FIG. 3 is a view for explaining an example of a manufacturing process of a semiconductor device, in which a wiring layer is formed on a lower wiring layer.

Specifically, after the oxide film 5 is formed on the lower wiring layer by using, for example, a well-known sputtering method, the oxide film 5 is formed by using well-known photolithography and dry etching. Then, a contact hole 6 is formed.

Next, a tungsten film 7 is formed using a well-known method, for example, a CVD method, and the contact hole 6 is buried. After the formation of the tungsten film 7, the tungsten film 7 is etched using a well-known dry etching method so that the tungsten film 7 remains only inside the contact hole 6. By this step, a tungsten buried layer 8 is formed.

Next, an aluminum film 9 is formed on the tungsten buried layer 8 by, for example, a sputtering method, and an aluminum wiring 10 patterned by a photolithography method and a dry etching method is formed. Form.

Next, oxide film 5 is formed on aluminum wiring 10 by using the same method as that described above. At this time, since the aluminum wiring 10 is patterned, the surface of the oxide film 5 formed thereon has irregularities due to the influence of the step of the pattern.

Therefore, the polishing liquid is chemically and mechanically polished using the polishing liquid described in the first to fourth embodiments until the uneven portion is sufficiently flattened. Then, a new wiring is formed on the flattened oxide film 5.

Incidentally, it was confirmed that the number of scratches on the flattened surface was much smaller than that of the conventional method as in the case of the first embodiment.

As described above, by applying the chemical mechanical polishing method to the surface of the object to be polished, it is possible to always form, for example, wiring on a flat surface without any trouble such as disconnection. As a result, it is possible to realize the manufacture of a highly integrated semiconductor element having a multi-layered wiring or a device having a three-dimensional structure.

[0074]

According to the present invention, the occurrence of scratches on the surface can be reduced by subjecting the surface of the formed film to chemical mechanical polishing in the middle of the manufacturing process. Contributes to the improvement of manufacturing yield and cost reduction.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of abrasive grains for explaining first and second embodiments.

FIG. 2 is a sectional view of abrasive grains for explaining a third and a fourth embodiment.

FIG. 3 is a view illustrating a manufacturing process of a semiconductor device for describing a fifth embodiment;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Core material, 2 ... Outer shell material, 3 ... Organic polymer, 4 ... Inorganic molecule, 5 ... Oxide film (interlayer insulating film), 6 ... Contact hole, 7 ... Tungsten film, 8 ... Tungsten buried layer, 9 ... Aluminum film, 10 ... aluminum wiring

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B24D 3/00 330 B24D 3/00 330D 350 350 C09K 13/00 C09K 13/00 H01L 21/304 622 H01L 21 / 304 622B 21/306 21/306 MF term (reference) 3C047 GG15 3C058 AA07 AC04 CA01 CB01 CB05 DA02 DA12 3C063 AA10 BB14 BB15 BB30 CC30 EE10 5F043 BB27 BB30 DD16 DD30 FF07 GG10

Claims (12)

[Claims] 1. A polishing grain comprising an inorganic substance and an organic substance, wherein the organic substance is a non-electrolyte. 2. The abrasive grain according to claim 1, wherein the inorganic substance is particles, and an organic layer is formed on the surface of the particles. 3. The abrasive grain according to claim 1, wherein the organic substance is particles, and an inorganic layer is formed on the surface of the particles. 4. A polishing abrasive grain comprising an inorganic substance and an organic substance, wherein the inorganic substance and the organic substance are at least chemically bonded. 5. The abrasive grain according to claim 1, wherein the organic layer is a polymer having a molecular weight of 500 or more. 6. A polishing liquid characterized by comprising abrasive grains comprising an inorganic substance and an organic substance which is a non-electrolyte dispersed in a solvent, and a polishing accelerator added to the solvent. 7. The polishing liquid according to claim 6, wherein said solvent is water. 8. A polishing liquid comprising an abrasive and an inorganic non-electrolyte dispersed in water and a polishing accelerator added thereto is supplied to at least the surface of the object to be polished. A polishing method characterized by flattening the surface of a body chemically and mechanically. 9. A polishing slurry comprising an inorganic substance and an organic substance which is a non-electrolyte is dispersed in water, and a polishing liquid to which a polishing accelerator is added is brought into contact with at least the surface of the object to be polished. A polishing method characterized in that the surface of a polishing body is flattened chemically and mechanically. 10. A semiconductor device comprising: a film forming step of forming a thin film above a semiconductor substrate; a polishing step of polishing the thin film; and a cleaning step of cleaning the semiconductor substrate.
Abrasive grains composed of an inorganic substance and an organic substance that is a non-electrolyte are dispersed in water, and a polishing liquid to which a polishing accelerator is added is supplied to at least the surface of the thin film, and the surface of the thin film is chemically and mechanically A method for manufacturing a semiconductor device, comprising flattening. 11. A semiconductor device comprising: a film forming step of forming a thin film above a semiconductor substrate; a polishing step of polishing the thin film; and a cleaning step of cleaning the semiconductor substrate.
Abrasive grains composed of an inorganic substance and an organic substance that is a non-electrolyte are dispersed in water, and a polishing liquid to which a polishing accelerator is added is supplied to at least the surface of the thin film, and the surface of the thin film is chemically and mechanically A method for manufacturing a semiconductor device, comprising repeating the film forming step after flattening. 12. The method for manufacturing a semiconductor device according to claim 10, wherein said thin film is formed above a semiconductor substrate having a step.