WO2007020939A1

WO2007020939A1 - Polishing slurry

Info

Publication number: WO2007020939A1
Application number: PCT/JP2006/316096
Authority: WO
Inventors: Takashi Miyoshi; Yasuhiro Takaya; Ken Kokubo; Kenji Matsubayashi; Takumi Oshima
Original assignee: Vitamin C60 Bioresearch Corporation
Priority date: 2005-08-16
Filing date: 2006-08-16
Publication date: 2007-02-22
Also published as: JPWO2007020939A1

Abstract

A polishing slurry to be used for polishing conductor or metal is characterized in that the polishing slurry contains water, fullerene or fullerene derivative, and the particle diameter of the fullerene or the fullerene devivative is 100nm or smaller. A planarity of 2nm or less in 20μm square is achieved by having the particle diameter of the fullerene or the fullerene derivative 100nm or less.

Description

Specification

Polishing slurry

Technical field

The present invention relates to a polishing slurry used for chemical mechanical polishing (CMP).

Background art

[0002] In recent years, there has been a demand for information electronic devices that are more compact and highly functional. Along with this, further miniaturization and high integration of LSI (Large Scale Integrated Circuit) are required. As a highly integrated LSI technology for LSIs, multilayer wiring technology using copper as a wiring material is known. When forming a multilayer wiring, it is necessary to flatten the surface of each wiring layer constituting the multilayer wiring. CMP is applied as a planarization process for each layer. In addition, CMP is indispensable in the damascene process in which copper is buried in a groove for wiring formed in advance by sputtering, and then the copper on the surface is removed to form a copper wiring. In this way, CMP is one of the important elemental technologies for further miniaturization and high integration of LSI.

[0003] In a conventional CMP for polishing a copper wiring, a polishing slurry containing silica-based particles and alumina-based particles as polishing particles is used. For example, Patent Document 1 discloses a slurry for CMP containing a silica abrasive capable of polishing a copper-based metal film.

Patent Document 1: JP 2004-071673 A

Disclosure of the invention

Problems to be solved by the invention

[0004] Polishing slurries used in conventional CMP use silica-based particles or alumina-based particles as polishing abrasive grains, so those having a large particle size can reach several hundred nm and have large variations in particle size. there were. Furthermore, since silica-based particles or alumina-based particles are likely to aggregate, it has been difficult to maintain uniform dispersibility of the abrasive cannons in the polishing slurry. Therefore, the flatness when copper wiring is polished using conventional CMP polishing slurry is about 500 nm in 30 mm square, and 7 to 8 layers is the limit when applied to the polishing power of a multilayer wiring structure. Met. In order to achieve higher integration of LSIs, it is necessary to polish the copper wiring more evenly. The conventional polishing slurry for CMP meets this requirement. It is becoming difficult to

[0005] The present invention has been made in view of these problems, and an object of the present invention is to provide a polishing slurry that can further improve the flatness of the surface when a metal or semiconductor is polished by CMP. Is in the provision of.

Means for solving the problem

[0006] One embodiment of the present invention is a polishing slurry used for polishing a semiconductor or metal, which contains water and fullerene or a fullerene derivative, and the particle size of the fullerene or the fullerene derivative is less than lOOnm. It is characterized by that.

[0007] A fullerene single molecule is a very small sphere having a particle size of 0.7 lnm. Fullerene molecules are as hard as diamonds. For this reason, by polishing the semiconductor or metal using fullerene as the polishing slurry for CMP, it is possible to obtain flatness that was difficult to achieve with conventional CMP. However, in order to improve the flatness, the particle size of the abrasive particles in the polishing slurry is important. When the particle size of the fullerene or fullerene derivative exceeds lOOnm, scratches are generated on the substrate because the particle size of the abrasive grains is too large. In addition, when the particle size of fullerene or fullerene derivative is greater than or equal to lOOnm, the absolute value of the variation in particle size becomes large, which causes undulation in the substrate and makes flatness difficult. However, by setting the particle size of fullerene or fullerene derivative to less than lOOnm, it is possible to achieve flatness of 2 nm or less in 20 m square. As a result, the flatness of the substrate surface is dramatically improved, and it becomes possible to manufacture LSIs having a wiring structure with ten or more layers.

Here, the “particle size of fullerene or fullerene derivative” means the size of the fullerene or fullerene derivative in water, and the fullerene or fullerene derivative in water is a single molecule, cluster or aggregate. Either form may be sufficient.

[0009] Another aspect of the present invention is a polishing slurry used for polishing a semiconductor or metal, containing water and fullerene or a fullerene derivative, wherein the fullerene or fullerene derivative is dissolved in water. Features. Here, “fullerene or fullerene derivative is dissolved in water” means a state in which water containing fullerene or a fullerene derivative is not suspended and is transparent. [0010] According to this embodiment, fullerene or a fullerene derivative is dissolved in water and is present in water as a single molecule or a cluster of several fullerene molecules associated. For this reason, the polishing slurry of the polishing slurry is extremely fine and the particle size is kept uniform at the molecular level, so that flatness that is difficult to achieve with conventional CMP can be obtained.

[0011] In order to make the particle size of the fullerene derivative in water less than lOOnm or to make the fullerene derivative water-soluble, the fullerene derivative preferably has a hydroxyl group.

[0012] In the above-described embodiment, an oxidizing agent, a preservative, and a chelating agent may be further contained.

A polishing slurry further containing an oxidizing agent, a preservative, and a chelating agent is suitable for polishing a metal. The oxidizing agent forms a fragile oxide film on the metal surface. The preservative suppresses the corrosion of the oxidizing agent. The chelating agent serves to dissolve the oxide film formed by the oxidizing agent into the slurry as complex ions. In such an aqueous solution, fullerene nanoparticles that rotate under constant pressure with a polishing pad act as polishing particles and play a role in smoothly removing fragile oxide films without scratching or roughness. . The invention's effect

[0013] According to the present invention, a semiconductor or metal can be polished more flatly.

Brief Description of Drawings

FIG. 1 is a schematic view showing a configuration of a general CMP apparatus used in the present embodiment.

[Fig. 2] FT-IR spectrum of water-soluble C (OH) 9O.

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[Fig. 3] FT-IR ^ vector diagram of water-insoluble C (ΟΗ) · 5Η の of reaction raw material.

60 12 2

[Fig. 4] TGA measurement chart of water-soluble C (OH) 9Η.

60 36 2

FIG. 5 is a graph showing the relationship between polishing time and surface roughness.

FIG. 6 is an example of an AFM observation image of the substrate surface obtained by a polishing experiment using the polishing slurry of this example.

FIG. 7 is an example of an AFM observation image of the substrate surface obtained by a polishing experiment using the polishing slurry of this example.

[Fig. 8] FT-IR spectrum of water-soluble C (ΟΗ) · 9Η.

60 40 2

[Fig. 9] TGA measurement chart of water-soluble C (ΟΗ) · 9Η.

60 40 2

Explanation of symbols [0015] 10 polishing surface plate, 12 polishing pad, 20 pressure head, 30 substrate, 40 polishing slurry supply means, 50 polishing slurry.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like.

FIG. 1 is a schematic diagram showing a configuration of a general CMP apparatus used in the present embodiment.

The CMP apparatus 1 includes a polishing surface plate 10, a polishing pad 12, a pressure head 20, and polishing slurry supply means 40. The polishing surface plate 10 has a mechanism that can rotate at a predetermined rotation speed. A polishing pad 12 is affixed to the polishing surface plate 10. The polishing pad 12 is not particularly limited, and for example, non-woven fabric, foamed polyurethane, porous fluorocarbon resin, etc. can be used. The pressure head 20 has a mechanism that can rotate at a predetermined rotation speed and a mechanism that pressurizes the polishing platen 10 with a predetermined pressure. A substrate 30 that also has metal or Z and semiconductor power is attached to the pressure head 20 with the surface to be polished facing the polishing surface plate 10. The polishing slurry supply means 40 includes piping, a pump (not shown), and the like, and can continuously supply the polishing slurry 50 onto the polishing pad 12 during polishing.

[0018] The polishing slurry according to the embodiment of the present invention is a polishing slurry containing water and fullerene or a fullerene derivative, and has a particle size force of less than SlOOnm. In the present invention, fullerene is not limited as long as it satisfies the purpose, but may be, for example, C60, C70 or higher, and a mixture thereof. Among these fullerenes, C60 is preferable. By setting the particle size of fullerene or fullerene derivative to less than lOOnm, the surface of the semiconductor or metal can be polished more flatly. If the particle size of the fullerene or fullerene derivative is less than 100 nm, the fullerene or fullerene derivative may be in the form of a single molecule, a cluster or an aggregate in the aqueous solution of the polishing slurry. By setting the particle size of the fullerene or fullerene derivative to less than lOOnm, flatness of 2 nm or less in a 20 μm square can be realized. This dramatically improves the flatness of the substrate surface and enables the manufacture of LSIs with a dozen levels of wiring structures.

In order to further improve the flatness of the surface of the semiconductor or metal, it is preferable that the fullerene or fullerene derivative is dissolved in water. Fullerene or fullerene induction The polishing slurry in which the body is dissolved in water is transparent, and the particle size of fullerene or fullerene derivative is naturally less than lOOnm. Since the fullerene or fullerene derivative is dissolved in water, it becomes difficult for abrasive particles to remain on the surface of the semiconductor or metal, and the polishing slurry can be easily removed after the polishing process.

[0020] In order to reduce the particle size of the fullerene derivative in water to less than lOOnm or to make the fullerene derivative water-soluble, the fullerene derivative preferably has a hydroxyl group. Further, it is expected that the fullerene derivative can further improve water solubility without increasing the number of hydroxyl groups by further having a hydrophilic group such as an amino group. it can. The functional group of the fullerene derivative is not limited to the above-described hydroxyl group and amino group as long as it improves water solubility. For example, a carboxyl group, a sulfo group, a morphono group, and a salt thereof can be used as the functional group of the fullerene derivative.

[0021] The means for dissolving fullerene in water is not limited to the use of fullerene derivatives in which substituents such as hydroxyl groups are introduced into fullerene, but inclusion bodies of fullerene, cyclodextrin, PVP and the like (hereinafter referred to as fullerene inclusion). Body)). By using a fullerene inclusion, it is possible to dissolve fullerene without changing the structure of fullerene itself. Alternatively, after fullerene is dissolved in a polar organic solvent, the fullerene may be dispersed in water by adding it to a large amount of water and stirring.

[0022] When the metal is polished, it is preferable to further contain an oxidizing agent, a preservative, and a chelating agent.

[0023] The oxidizing agent oxidizes the surface of the metal to be polished. The oxidizing agent is not particularly limited, and examples thereof include aqueous hydrogen peroxide, sodium hydroxide, and potassium hydroxide.

[0024] The preservative suppresses the corrosion of the oxidizing agent. Preservatives are not particularly limited, but BTA

(Benzotriazole) and its ammonium compound, quinaldic acid and the like.

[0025] The chelating agent dissolves the acid film formed by the oxidizing agent into the slurry as complex ions. The chelating agent is not particularly limited, and examples thereof include compounds such as malonic acid, citrate, phosphoric acid, nitric acid, malic acid, and ammonium compounds thereof.

[0026] The type and amount of the oxidizing agent, preservative, and chelating agent are determined depending on the metal material to be polished. It can be changed as appropriate according to the quality. An example of a polishing slurry that can be applied to copper polishing is shown below.

[0027] Polyhydroxide fullerene: 0.1 to 0.5 wt%

Hydrogen peroxide solution (oxidant): 0.5-30wt%

Quenic acid ammonium (chelating agent): 0.5-: LOwt%

Ammonium phosphate (chelating agent): 0.5-: LOwt%

BTA (preservative): 0.12 ~ 0.5%

[0028] Since the pH of the polishing slurry affects the polishing rate, the pH of the polishing slurry may be adjusted with a pH adjusting agent such as hydroxide or ammonia.

[0029] (Example 1)

A polishing slurry was prepared using full water and highly water-soluble polyhydroxylene fullerene, which was estimated to have an average of 36 hydroxyl groups modified on fullerene C60, and the resulting copper film was deposited on a silicon wafer. ! A polishing experiment using CMP was conducted.

[0030] (Synthesis of water-soluble fullerene hydroxide)

Water-insoluble hydroxylated fullerene synthesized by the method reported by LY Chiang et al. (J. Am. Chem. Soc, 1992, 114, 10154) (average estimated structure C (OH) · 5Η Ο) 0. 100g In

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Then, 10 mL of 30% aqueous hydrogen peroxide solution was added, and the suspension was stirred at 60 ° C. for 4 days. After confirming that the solution was completely uniform and yellow and transparent, the reaction was stopped, and 50 mL of 2-propanol, jetyl ether, and hexane were sequentially added to precipitate a solid.

[0031] The resulting precipitate is precipitated using a centrifuge, separated by decantation, further washed twice with 50 mL of ether, and then vacuum-dried for 18 hours to dissolve the water-soluble reaction product. As a light ocher powder, 0.097 g of fullerene hydroxide was obtained.

[0032] Fig. 2 shows the FT-IR ^ vector of the powder thus obtained. With large broad absorption around 3400 cm ^_1 based on O-H Shin contraction of hydroxyl, C-C and C-0 stretch in based 1620, 1370, showed a broad absorption around 1080cm- ^1. These absorption patterns are very similar to the spectrum of the water-insoluble hydroxide-fullerene (Fig. 3) reported by LY Chiang et al. (J. Am. Chem. Soc, 1992, 114, 10154), and the relative intensity ratio of each absorption is slightly different. It was suggested that there is. The small absorption around ^1720cm_1 suggests the presence of a ketone group due to the pinacol rearrangement reaction of the hydroxyl group (LY Chiang et al., J. Am. Chem. Soc, 1993, 115, 5453). Since the absorption based on carbon C = 0 stretching is large, the existence ratio is judged to be small.

[0033] When this water-soluble hydroxy-fullerene was subjected to thermal analysis using a thermogravimetric analyzer TGA in a nitrogen atmosphere at a heating rate of 5 ° C Zmin, it was about 9% from room temperature to around 150 ° C. As weight loss was observed, it was estimated that approximately 9% of water was strongly adsorbed by the hydroxyl group (Fig. 4).

Further, as a result of elemental analysis, this water-soluble fullerene hydroxide was in good agreement as having a C (OH) · 9 糸 O yarn considering the water content described above. The above thread-forming element

60 36 2

Analysis ί or C:. 48 20%, Η : 3. a 64 ^_0/0, the experimental value ί or C:. 48 06%, H : 3. 61 ^_0/0, water content 10.8% It was estimated.

[0035] The solubility of this water-soluble fullerene hydroxide in water was 17.5 mg / mL (l. 8 wt%). Compared to the above, it has been shown that it has high solubility.

[0036] (Preparation of polishing slurry)

0.02 g of fullerene hydroxide prepared as described above was dissolved in 20 ml of ultrapure water, and then stirred by ultrasonic vibration. The obtained fullerene aqueous solution was uniformly dispersed with ultrasonic waves to prepare a 0.1 wt% polyhydroxyl-fullerene aqueous solution. Next, the fullerene aqueous solution was passed through an lOOnm filter. As a result, a light yellow uniform filtrate exactly the same as the aqueous solution before filtration was obtained. From this, it was estimated that the fullerene particles in the fullerene aqueous solution were less than lOOnm.

[0037] Subsequently, hydrogen peroxide water (lwt%), ammonium citrate (0.5wt%), ammonium phosphate (0. 5 wt%) and BTA (0.12 wt%). At this time, no change was observed in the color of the solution. As a result, the aggregation of fullerene particles did not occur, and the dispersion stability of polyhydroxyl-fullerene was confirmed.

[0038] (Polishing experiment) Using the CMP polishing slurry prepared as described above and the CMP apparatus shown in FIG. 1, a copper CMP polishing experiment was conducted. As a polishing target, a substrate in which a copper film was electrodeposited on a silicon wafer was used.

FIG. 5 shows the relationship between the polishing time and the surface roughness. The roughness before polishing in the 5 μm square is more than lOnm in RMS, and a large swell of about 40 nm is seen from the cross-sectional curve. However, as the polishing time increases, the roughness improves exponentially, and the surface finish is good with an RMS force of S2 nm or less (RMS is 0.339 nm in the cross-section curve) in about 6 minutes. In addition, the large waviness of the substrate surface seen before polishing has been removed, and an extremely flat surface is obtained. The polishing conditions are as follows.

Pressure of pressure head: 0.25MPa

Number of rotations of polishing surface plate 10 and pressure head 20: 127 rpm

FIG. 6 and FIG. 7 are examples of AFM observation images of the substrate surface obtained by a polishing experiment using the polishing slurry of this example. Figure 6 shows an AFM image when the measurement area is 20 m square. The RMS at this time was 1.644 nm. Figure 7 shows an AFM image when the measurement area is 5 m square. The RMS at this time was 0.722 nm, and an ultra-smooth surface with a roughness of 1 nm or less was obtained.

[0041] The present invention is not limited to the above-described embodiments, and modifications such as various design changes can be made based on the knowledge of those skilled in the art, and such modifications can be added. The embodiments may be included in the scope of the present invention.

For example, in each of the embodiments described above, the number of force hydroxyl groups in which the average number of hydroxyl groups of the fullerene hydroxide is 36 is not limited thereto. For example, a fullerene hydroxide having an average number of hydroxyl groups of 40 can be prepared by the following procedure, and can be used as polishing particles of polishing slurry.

[0043] (Synthesis of water-soluble fullerene hydroxide)

Follow the same procedure as in Example 1 but stir the water-insoluble solution of water-insoluble hydroxide-fullerene in hydrogen peroxide solution at 60 ° C for 4 days to confirm that the solution became completely uniform yellow and transparent. After further reaction for 10 days, the color of the solution gradually faded and became pale yellow and transparent. Further, by the same operation, 0.13 g of a milky white powder of water-soluble hydroxylated fullerene was obtained. [0044] An FT-IR measurement of the powder thus obtained confirmed that the spectrum was almost the same as that of hydroxy-fullerene having an average number of hydroxyl groups of 36 (Fig. 8).

[0045] When this water-soluble hydroxy-fullerene was subjected to thermal analysis using a thermogravimetric analyzer TGA in a nitrogen atmosphere at a heating rate of 5 ° C Zmin, it was about 10% from room temperature to around 150 ° C. As weight loss was observed, it was estimated that approximately 10% of the water was strongly adsorbed by the hydroxyl groups (Figure 9).

As a result of elemental analysis, the water-soluble hydroxy-fullerene 3 was in good agreement as having a yarn composition of C (OH) · 9ΗO in consideration of the water content described above. The above thread-forming element

60 40 2

Analysis ί or ^{_{C:. 46 11 0/0}} , Η: 3. 74 0/0 Deari, Found [Seriously:. 46 26%, Η: 3. a 68 ^_0/0, water content 10. Estimated 4%.

[0047] When the solubility of this water-soluble fullerene hydroxide 3 in water was examined, 58.9 mg / mL (5.

9 wt%), which is much higher than that of water-soluble solutions using clathrate compounds reported so far.

Industrial applicability

[0048] According to the present invention, a semiconductor or metal can be polished more flatly. More specifically, the polishing slurry of the present invention is useful as a chemical mechanical polishing polishing particle for flattening the surface of a semiconductor or metal, and has great industrial applicability.

Claims

The scope of the claims

[1] A polishing slurry used for polishing semiconductors or metals,

Containing water and fullerene or fullerene derivative,

A polishing slurry, wherein a particle size of the fullerene or the fullerene derivative is less than lOOnm.

[2] A polishing slurry used for polishing semiconductors or metals,

Containing water and fullerene or fullerene derivative,

A polishing slurry, wherein the fullerene or the fullerene derivative is dissolved in the water.

[3] The polishing slurry according to claim 1 or 2, wherein the fullerene derivative has a hydroxyl group.

4. The polishing slurry according to any one of claims 1 to ³ , further comprising an oxidizing agent, a preservative, and a chelating agent.

5. The polishing slurry according to claim 4, wherein the oxidizing agent is a substance selected from the group consisting of hydrogen peroxide, sodium hydroxide, and potassium hydroxide.

6. The polishing slurry according to claim 4 or 5, wherein the preservative is a compound selected from the group consisting of compounds such as BTA, an ammonium compound of BTA, and quinaldine acidity.

[7] The claim, wherein the chelating agent is a substance selected from the group consisting of malonic acid, citrate, phosphoric acid, nitric acid, malic acid, and their ammonium compounds. 4. The polishing slurry according to any one of 4 to 6, wherein:

[8] The polishing slurry according to any one of claims 1 to 7, which is used for polishing copper.