JP2010245148A - Chemical mechanical polishing method, semiconductor device using the same, and kit for preparing aqueous dispersion for chemical mechanical polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chemical mechanical polishing method for evenly polishing a processing object with a wiring layer containing tungsten at a high speed. <P>SOLUTION: The chemical mechanical polishing method includes: a first polishing process for chemically and mechanically polishing only a tungsten film by using a first aqueous dispersion for chemical mechanical polishing; a second polishing process for chemically and mechanically polishing the tungsten film, barrier metal film; and silicon oxide film simultaneously by using a second aqueous dispersion for chemical mechanical polishing. The first and second aqueous dispersions for chemical mechanical polishing contain at least (A) cationic water-soluble polymer, (B) an iron (III) compound, and (C) colloidal silica. A content ratio (M<SB>A1</SB>/M<SB>A2</SB>) of a content (M<SB>A1</SB>) [mass%] of the component (A) in the first aqueous dispersion for chemical mechanical polishing to a content (M<SB>A2</SB>) [mass%] of the component (A) in the second aqueous dispersion for chemical mechanical polishing is 0.004-0.3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a chemical mechanical polishing method, a semiconductor device using the chemical mechanical polishing method, and a chemical mechanical polishing aqueous dispersion preparation kit.

  In recent years, with the increase in definition of semiconductor devices, the miniaturization of wirings formed in the semiconductor devices has progressed. Along with this, a technique of planarizing the wiring layer by chemical mechanical polishing (hereinafter also referred to as “CMP”) is used. For example, a conductive metal such as aluminum, copper, or tungsten is deposited in a fine groove or hole provided in an insulating film such as silicon oxide on a semiconductor substrate by a method such as sputtering or plating, and then laminated excessively. A damascene process is generally used in which the metal film is removed by CMP, and the metal is left only in the fine grooves and holes (see, for example, Patent Document 1).

  In particular, tungsten having excellent embeddability is used for via holes that electrically connect the wirings in the vertical and vertical directions. As an aqueous dispersion for chemical mechanical polishing for polishing tungsten film, a technique relating to a polishing composition containing an oxidizing agent such as hydrogen peroxide, an iron catalyst such as iron nitrate, and abrasive grains such as silica has been proposed ( For example, see Patent Document 2). The chemical mechanical polishing aqueous dispersion used for polishing such a tungsten film is required to have a higher polishing rate and a high level of flatness of the surface to be polished. In order to achieve these properties in a well-balanced manner, a technique for adding a water-soluble polymer to a polishing composition has been studied (see, for example, Patent Document 3 and Patent Document 4).

  However, a technology that can achieve both a high polishing rate and a high planarization characteristic for a surface to be polished such as a semiconductor wafer provided with a wiring layer containing tungsten has not been developed yet.

Special table 2002-518845 gazette JP 2005-518091 A JP 2007-19093 A JP 2008-503875 A

  An object of the present invention is to provide a chemical mechanical polishing method for polishing a target object provided with a wiring layer containing tungsten at high speed and flatly.

  Another object of the present invention is to provide a chemical mechanical polishing aqueous dispersion preparation kit capable of ensuring long-term storage stability of the chemical mechanical polishing aqueous dispersion used in the chemical mechanical polishing method.

The chemical mechanical polishing method according to the present invention comprises:
A first polishing step of chemically mechanically polishing a tungsten film deposited on the barrier metal film using the first chemical mechanical polishing aqueous dispersion;
A second polishing step of simultaneously chemical mechanical polishing the tungsten film, the barrier metal film, and the silicon oxide film using the second chemical mechanical polishing aqueous dispersion;
A chemical mechanical polishing method comprising:
The first chemical mechanical polishing aqueous dispersion and the second chemical mechanical polishing aqueous dispersion include at least (A) a cationic water-soluble polymer, (B) an iron (III) compound, and (C). Colloidal silica, and
The content (M _A1 ) [mass%] of the component (A) in the first chemical mechanical polishing aqueous dispersion and the component (A) in the second chemical mechanical polishing aqueous dispersion. The content ratio (M _A1 / M _A2 ) with the content (M _A2 ) [mass%] is 0.004 to 0.3.

In the chemical mechanical polishing method according to the present invention, the M _A1 is 0.001% by mass to 0.01% by mass, and the M _A2 is 0.05% by mass to 0.2% by mass. Can do.

  In the chemical mechanical polishing method according to the present invention, the cationic water-soluble polymer (A) may be polyethyleneimine.

  In the chemical mechanical polishing method according to the present invention, the number average molecular weight of the cationic water-soluble polymer (A) may be 200 to 1,000,000.

  In the chemical mechanical polishing method according to the present invention, the (B) iron (III) compound may be at least one selected from ferric nitrate and ferric sulfate.

In the chemical mechanical polishing method according to the present invention, the first chemical mechanical polishing aqueous said dispersion the content of the component (B) (M _B1) and the second chemical mechanical polishing aqueous aforementioned dispersion The content (M _B2 ) of the component (B) can be 0.01% by mass to 20% by mass.

In the chemical mechanical polishing method according to the present invention, the content (M _C1 ) of the component (C) in the first chemical mechanical polishing aqueous dispersion and the second chemical mechanical polishing aqueous dispersion described above. The content (M _C2 ) of the component (C) can be 1% by mass to 20% by mass.

  In the chemical mechanical polishing method according to the present invention, the average particle diameter calculated from the specific surface area measured using the BET method of the (C) colloidal silica may be 10 nm to 60 nm.

  In the chemical mechanical polishing method according to the present invention, the first polishing step and the second polishing step can be continuously performed on the same polishing table.

  The chemical mechanical polishing method according to the present invention may further include a cleaning step of removing iron adsorbed on the object to be processed after the second polishing step.

The chemical mechanical polishing aqueous dispersion preparation kit according to the present invention comprises:
A chemical mechanical polishing aqueous dispersion preparation kit for preparing a chemical mechanical polishing aqueous dispersion for use in the above chemical mechanical polishing method,
A first composition containing at least (A) a cationic water-soluble polymer and an acidic compound, and having a pH of 1 to 3;
A second composition comprising at least (B) an iron (III) compound and water;
A third composition containing at least (C) colloidal silica and water;
Is a kit configuration.

  A semiconductor device according to the present invention is manufactured using the chemical mechanical polishing method described above.

  According to the above chemical mechanical polishing method, not only the tungsten film having unevenness can be polished at high speed and flatness, but also the surface to be polished in which the tungsten film and the silicon oxide film coexist can be polished at high speed and flatness. Can be polished.

It is sectional drawing which shows typically the chemical mechanical polishing method which concerns on this embodiment. It is sectional drawing which shows typically the chemical mechanical polishing method which concerns on this embodiment. It is sectional drawing which shows typically the chemical mechanical polishing method which concerns on this embodiment. It is a perspective view which shows a chemical mechanical polishing apparatus typically.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

1. Chemical mechanical polishing method The chemical mechanical polishing method according to the present embodiment includes a first polishing step of chemically mechanically polishing a tungsten film deposited on a barrier metal film using a first chemical mechanical polishing aqueous dispersion. And a second polishing step of simultaneously chemical mechanical polishing the tungsten film, the barrier metal film, and the silicon oxide film using the second chemical mechanical polishing aqueous dispersion, and a chemical mechanical polishing method comprising: The first chemical mechanical polishing aqueous dispersion and the second chemical mechanical polishing aqueous dispersion include at least (A) a cationic water-soluble polymer, (B) an iron (III) compound, and (C). And (2) content (M _A1 ) [mass%] of the component (A) in the first chemical mechanical polishing aqueous dispersion, and the second chemical mechanical polishing aqueous dispersion. Content of component (A) in _{(M A2)} content ratio of _{[mass%] (M A1 / M A2} ) is characterized in that it is a 0.004 to 0.3.

  1 to 3 are sectional views schematically showing a chemical mechanical polishing method according to an embodiment of the present invention. Examples of the object to be processed by the chemical mechanical polishing method according to the present embodiment include a semiconductor wafer provided with a wiring layer containing tungsten. Specifically, an object to be processed includes a silicon oxide film having trenches (grooves) or via holes, and a tungsten film provided on the silicon oxide film via a barrier metal film. For example, FIG. The object 100 shown in FIG. The object 100 can be manufactured as follows, for example.

  (1) First, the base 10 is prepared. The substrate 10 may be composed of, for example, a silicon substrate and a silicon oxide film formed thereon. Furthermore, a functional device such as a transistor may be formed on the substrate 10.

  (2) Next, a silicon oxide film 12 to be an interlayer insulating film is formed on the substrate 10 by using a CVD method or a thermal oxidation method.

  (3) Next, the silicon oxide film 12 is patterned. For example, the via hole 14 is formed on the silicon oxide film 12 by applying a photolithography method.

  (4) Next, a barrier metal film is thinly formed on the surface of the silicon oxide film 12 and the inner wall surface of the via hole 14 by a sputtering method. Since the electrical contact between tungsten and silicon is not very good, good electrical contact can be realized by interposing the barrier metal film 16. Examples of the barrier metal film 16 include Ti and / or TiN.

  (5) Next, the to-be-processed object 100 is obtained by depositing the tungsten film 18 using the CVD method.

1.1 First Polishing Step The first polishing step is a surplus deposited on the barrier metal film 16 other than the portion embedded in the via hole 14 (or trench) or the like of the object 100 as shown in FIG. This is a step of removing the tungsten film 18 by polishing. In the first polishing process, it is desired to remove the upper tungsten film 18 in a short time while eliminating the unevenness of the tungsten film 18 (resolving the level difference). Therefore, the first polishing step of the chemical mechanical polishing method according to the present embodiment aims to polish at a high speed while eliminating the level difference of the tungsten film 18 having unevenness.

  In the first polishing step of the chemical mechanical polishing method according to the present embodiment, the polishing rate of the tungsten film 18 is preferably 300 nm / min or more, more preferably 360 nm / min or more. It is preferable that the polishing rate of the tungsten film is 300 nm / min or more because the excess tungsten film 18 can be removed in a short time, and the throughput of the polishing process is improved. In the first polishing process, one of the purposes is to eliminate the step of the tungsten film 18, but it is sufficient that the step can be eliminated to such an extent that erosion can be suppressed to 30 nm or less. If the erosion is 30 nm or less, good flatness with less erosion can be obtained by combining with the second polishing step described later. On the other hand, when not combined with a second polishing step described later, erosion generated after the first polishing step cannot be eliminated, and a polished surface having good flatness cannot be obtained.

1.2 Second Polishing Step The second polishing step removes the excess tungsten film 18 deposited on the barrier metal film 16 other than the portion embedded in the via hole 14 (or trench) or the like in the first polishing step. Thereafter, as shown in FIG. 3, the tungsten film 18, the barrier metal film 16, and the silicon oxide film 12 embedded in the via hole 14 (or trench) or the like are simultaneously polished. In the second polishing step, not only the polishing rate for the tungsten film 18, the barrier metal film 16, and the silicon oxide film 12 is high, but also an object is to flatten a step such as erosion generated in the first polishing step.

  In the second polishing step, the polishing rate of the tungsten film is preferably 30 to 200 nm / min, and more preferably 40 to 150 nm / min. The polishing rate of the silicon oxide film is preferably 40 to 300 nm / min, and more preferably 60 to 200 nm / min. When the polishing rate is in the above range, it is preferable that the planarization can be performed quickly and the throughput of the polishing process is good.

Further, the polishing rate (RR _W ) of the tungsten film 18 and the polishing rate (RR _O ) of the silicon oxide film 12 are appropriately set within the above ranges depending on the size of the irregularities such as erosion generated after the first polishing step. It is preferable to adjust. Ratio of RR _W and RR _O is preferably _RR W _{/ RR} O = _0.4~0.9, more preferably _RR W _{/ RR} O = _0.5~0.8. When the polishing rate ratio is within the above range, it becomes suitable for flattening unevenness such as erosion generated in the first polishing step. If the polishing rate ratio exceeds the above range, the tungsten film is excessively polished, and as a result, the mechanical strength of the silicon oxide film is lost and wear increases, and erosion may increase. If the polishing rate ratio is less than the above range, the polishing rate of the tungsten film 18 may be extremely reduced, and prototyping may occur where the entire embedding is raised. On the other hand, when not combined with the first polishing step, the polishing time of the excess tungsten film 18 is increased and the throughput is deteriorated, which is not preferable. Furthermore, since the uncut portion of the excess tungsten film 18 other than the buried portion wiring increases, it is not preferable.

  In addition, it is preferable to perform a 2nd grinding | polishing process continuously on the same grinding | polishing table as the above-mentioned 1st grinding | polishing process. By continuously performing the process using the same polishing table, it is possible to continuously move to the second polishing step without removing the object to be processed from the polishing apparatus after the first polishing is completed, thereby improving the throughput.

1.3 Cleaning Step After the second polishing step, it is preferable to further perform a cleaning step for removing iron adsorbed on the object to be processed (for example, a wafer to be polished). By performing such a cleaning process, iron contamination of the object to be processed can be prevented. In the cleaning step, a commercially available cleaning agent that does not damage the surface of the object to be processed can be appropriately selected and used.

1.4 Chemical Mechanical Polishing Device In the first polishing step and the second polishing step, for example, a chemical mechanical polishing device 200 as shown in FIG. 4 can be used. FIG. 4 is a perspective view schematically showing the chemical mechanical polishing apparatus 200. The slurry 44 is supplied from the slurry supply nozzle 42 and the carrier head 52 holding the semiconductor substrate 50 is brought into contact with the turntable 48 to which the polishing cloth 46 is attached while rotating. In FIG. 4, the water supply nozzle 54 and the dresser 56 are also shown.

Polishing load of the carrier head 52 may be selected within the range of 10~1,000gf / cm ^2, preferably 30~500gf / cm ^2. Moreover, the rotation speed of the turntable 48 and the carrier head 52 can be suitably selected within the range of 10 to 400 rpm, and preferably 30 to 150 rpm. Flow rate of the slurry 44 supplied from the slurry supply nozzle 42 may be selected within the range of 10~1,000cm ³ / min, preferably 50~400cm ³ / min.

  As a commercially available chemical mechanical polishing apparatus, for example, “EPO-112”, “EPO-222” manufactured by Ebara Manufacturing Co., Ltd .; “LGP-510”, “LGP-552” manufactured by Lapmaster SFT, Applied Materials Manufactured, model “Mirra” and the like.

1.5 Chemical mechanical polishing aqueous dispersion used in each polishing step First chemical mechanical polishing aqueous dispersion used in the first polishing step and second chemical mechanical polishing water used in the second polishing step The system dispersion is also referred to as at least (A) a cationic water-soluble polymer (hereinafter also referred to as “component (A)”) and (B) an iron (III) compound (hereinafter referred to as “component (B)”). ) And (C) colloidal silica (hereinafter also referred to as “component (C)”).

  It is preferable to use the same component as the component (A), the component (B), and the component (C) contained in the first chemical mechanical polishing aqueous dispersion and the second chemical mechanical polishing aqueous dispersion. By using the same component, it is possible to continue to the second polishing step without performing line cleaning of the chemical mechanical polishing apparatus after the completion of the first polishing step. Can be shortened.

  Hereinafter, each component contained in the first or second chemical mechanical polishing aqueous dispersion will be described.

1.5.1 (A) Cationic water-soluble polymer The (A) cationic water-soluble polymer in the first chemical mechanical polishing aqueous dispersion is easily adsorbed on the surface of the tungsten film having irregularities. A protective film can be formed to control the polishing of the tungsten film. That is, by using an appropriate amount of the (A) cationic water-soluble polymer, it is possible to progress the polishing of the convex portion while protecting the concave portion of the tungsten film, thereby eliminating the initial step.

  The cationic water-soluble polymer (A) in the second chemical mechanical polishing aqueous dispersion is easily adsorbed on the surface of the tungsten film embedded in the trench or via hole to form a protective film. It is possible to control the polishing. That is, by using an appropriate amount of the (A) cationic water-soluble polymer, the silicon oxide film can be polished while protecting the tungsten film.

  Examples of the (A) cationic water-soluble polymer include polyalkyleneimine, polyvinylpyrrolidone, polyvinylamine, polyvinylpyridine, polyallylamine, polyvinylpiperazine, and polylysine. Among these (A) cationic water-soluble polymers, polyalkyleneimine is preferable, and polyethyleneimine is more preferable. In the first chemical mechanical polishing aqueous dispersion, the above-exemplified (A) cationic water-soluble polymer can be used singly or in combination of two or more.

  (A) The number average molecular weight of the cationic water-soluble polymer is preferably 200 to 1,000,000, and more preferably 10,000 to 100,000. (A) When the number average molecular weight of the cationic water-soluble polymer is less than 200, polishing of the tungsten film may not be controlled. On the other hand, if the number average molecular weight of the (A) cationic water-soluble polymer exceeds 1,000,000, the stability of the chemical mechanical polishing aqueous dispersion may be deteriorated.

  The number average molecular weight is a value in pullulan conversion, and gel permeation chromatography (column standard “Shodex Asahipak GF-710HQ + GF-510HQ + GF-310HQ” (manufactured by Showa Denko KK), eluent “0.2M monoethanolamine”) Can be measured.

In the chemical mechanical polishing method according to this embodiment, the content (M _A1 ) [mass%] of the component (A) in the first chemical mechanical polishing aqueous dispersion, and the second chemical mechanical polishing aqueous system. The content ratio (M _A1 / M _A2 ) to the content (M _A2 ) [mass%] of the component (A) in the dispersion is 0.004 to 0.3, preferably 0.05 to 0.1. Is in range.

If the value of M _A1 / M _A2 is within the above range, not only the excess tungsten film can be polished at a high speed in the first polishing step, but also erosion can be reduced. Furthermore, in the second polishing step, unevenness such as erosion generated in the first polishing step can be flattened.

Furthermore, the content (M _A1 ) of the component (A) in the first chemical mechanical polishing aqueous dispersion is preferably 0.001 to 0.01% by mass, more preferably 0.003 to 0.008. % By mass. When the content of the component (A) is less than the above range, protection of the concave portion of the tungsten film becomes insufficient, and the step-resolving property is deteriorated. In addition, if the above range is exceeded, the protection of the convex portion of the tungsten film becomes excessive, and the step-resolving property is lowered, and problems such as an increase in the remaining uncut portion of the tungsten film at portions other than the buried portion occur.

Further, the content (M _A2 ) of the component (A) in the second chemical mechanical polishing aqueous dispersion is preferably 0.05 to 0.2% by mass, more preferably 0.06 to 0.1. % By mass. It is preferable that the content of the component (A) is in the above range because unevenness such as erosion generated in the first polishing step can be flattened. When the content of the component (A) exceeds the above range, the polishing rate of the tungsten film may be extremely reduced, and protolysis may occur in which the entire embedded portion is raised. On the other hand, if the thickness is less than the above range, the tungsten wiring is excessively polished. As a result, the mechanical strength of the silicon oxide film is lost, the wear of the silicon oxide film proceeds, and erosion may increase.

1.5.2 (B) Iron (III) Compound The (B) iron (III) compound contained in the first and second chemical mechanical polishing aqueous dispersions effectively oxidizes the surface of the tungsten film. It creates a fragile modified layer and has the effect of promoting polishing of the tungsten film.

  (B) The iron (III) compound is not particularly limited as long as it exhibits the above-described effects, and may be either an organic acid iron salt or an inorganic acid iron salt. Examples of the iron (III) compound include iron nitrate (III) (hereinafter also referred to as “ferric nitrate”), iron sulfate (III) (hereinafter also referred to as “ferric sulfate”), and ammonium iron sulfate. (III), iron (III) perchlorate, iron (III) chloride, iron (III) citrate, iron iron (III) citrate, iron iron (III) oxalate and the like. Among these, at least one selected from ferric nitrate and ferric sulfate is preferable, and ferric nitrate is more preferable. Ferric nitrate is particularly effective in oxidizing the surface of the tungsten film to create a fragile modified layer, and suppresses surface defects such as polishing residues, dishing, and corrosion while maintaining a good polishing rate. be able to. (B) As the iron (III) compound, those exemplified above may be used alone or in combination of two or more.

The content (M _B1 ) of the (B) iron (III) compound in the first chemical mechanical polishing aqueous dispersion is preferably 0.01 with respect to the total mass of the first chemical mechanical polishing aqueous dispersion. It is -20 mass%, More preferably, it is 0.1-20 mass%. (B) If the content of the iron (III) compound is less than the above range, the effect of oxidizing the surface of the tungsten film is poor, and the polishing rate of the tungsten film is reduced, which is not preferable. On the other hand, if the content of the (B) iron (III) compound exceeds the above range, the polishing rate of the tungsten film becomes too high, which may cause dishing or erosion.

The content (M _B2 ) of the (B) iron (III) compound in the second chemical mechanical polishing aqueous dispersion is preferably 0.01 with respect to the total mass of the second chemical mechanical polishing aqueous dispersion. It is -20 mass%, More preferably, it is 0.1-20 mass%. (B) If the content of the iron (III) compound is less than the above range, the effect of oxidizing the surface of the tungsten film is poor, the polishing rate of the tungsten film is extremely reduced, and a protolith that raises the entire buried portion is generated. There is a case. On the other hand, if the content of the (B) iron (III) compound exceeds the above range, the tungsten wiring is excessively polished, resulting in the loss of the mechanical strength of the silicon oxide film, the wear of the silicon oxide film, and the erosion. May become larger.

1.5.3 (C) Colloidal silica (C) Colloidal silica contained in the first and second chemical mechanical polishing aqueous dispersions is used as an abrasive for mechanically polishing a tungsten film and a silicon oxide film. Has an effect. (C) As colloidal silica, what was manufactured by the well-known method can be used.

  (C) The average particle diameter calculated from the specific surface area measured using the BET method of colloidal silica is preferably 10 nm to 60 nm, and more preferably 15 nm to 45 nm. (C) When the average particle diameter of colloidal silica is in the above range, the surface to be polished on which the tungsten film and the silicon oxide film coexist can be polished at high speed while suppressing erosion or the like. (C) When the average particle size of colloidal silica is less than the above range, the polishing rate for the silicon oxide film becomes insufficient, and erosion or the like can be suppressed for the surface to be polished on which the tungsten film and the silicon oxide film coexist. Disappear. On the other hand, even if the average particle diameter of (C) colloidal silica exceeds the above range, erosion or the like may not be suppressed with respect to the polished surface where the tungsten film and the silicon oxide film coexist.

  (C) The average particle diameter of colloidal silica can be calculated from the specific surface area measured using the BET method, for example, with a flow type specific surface area automatic measuring device “micrometrics FlowSorb II 2300” (manufactured by Shimadzu Corporation). Hereinafter, a method for calculating the average particle diameter from the specific surface area of colloidal silica will be described.

Assuming that the shape of the colloidal silica is a true sphere, the diameter of the colloidal silica is d (nm), and the specific gravity is ρ (g / cm ³ ), the surface area A of the n colloidal silicas is A = nπd ^2. . Colloidal silica of n mass N becomes N = ρnπd ^3/6. Since the specific surface area is represented by the surface area of all the constituent particles per unit quantity of the powder, the specific surface area S of n colloidal silicas is S = A / N = 6 / ρd. By substituting the specific gravity ρ = 2.2 of colloidal silica into this equation and converting the unit, the following equation (1) can be derived.

Average particle diameter (nm) = 2727 / S (m ² / g) (1)

  In addition, all the average particle diameters of the colloidal silica in this specification are calculated based on Formula (1).

The content (M _C1 ) of (C) colloidal silica in the first chemical mechanical polishing aqueous dispersion is preferably 1 to 20% by mass with respect to the total mass of the first chemical mechanical polishing aqueous dispersion. Yes, more preferably 3 to 10% by mass. (C) If content of colloidal silica is less than the said range, the polishing rate with respect to a tungsten film may become inadequate. On the other hand, when the content of (C) colloidal silica exceeds the above range, colloidal silica tends to aggregate, and thus a stable chemical mechanical polishing aqueous dispersion may not be obtained.

The content (M _C2 ) of (C) colloidal silica in the second chemical mechanical polishing aqueous dispersion is preferably 1 to 20% by mass with respect to the total mass of the second chemical mechanical polishing aqueous dispersion. Yes, more preferably 3 to 10% by mass. (C) If content of colloidal silica is less than the said range, the polishing rate with respect to a tungsten film and a silicon oxide film may become inadequate. On the other hand, when the content of (C) colloidal silica exceeds the above range, colloidal silica tends to aggregate, and thus a stable chemical mechanical polishing aqueous dispersion may not be obtained.

1.5.4 Oxidizing Agent The first and second chemical mechanical polishing aqueous dispersions may further contain an oxidizing agent other than the (B) iron (III) compound described above. (B) Examples of oxidizing agents other than iron (III) compounds include ammonium persulfate, potassium persulfate, hydrogen peroxide, diammonium cerium nitrate, ferrous sulfate, ferrous nitrate, ozone, potassium periodate, Examples include peracetic acid, hypochlorous acid, and salts thereof. Among the oxidants exemplified above, ammonium persulfate, potassium persulfate, and hydrogen peroxide are preferable in view of oxidizing power, compatibility with the protective film, ease of handling, and the like. The exemplified oxidizing agents can be used singly or in combination of two or more.

  (B) The oxidizing agent other than the iron (III) compound is preferably 0.05 to 5% by mass, more preferably 0.08, based on the total mass of the first or second chemical mechanical polishing aqueous dispersion. ˜3 mass%. (B) When the oxidizing agent other than the iron (III) compound is less than the above range, the polishing rate for the tungsten film may be insufficient. On the other hand, if the oxidizing agent other than the (B) iron (III) compound exceeds the above range, corrosion or dishing of the tungsten film may occur.

2. Chemical Mechanical Polishing Aqueous Dispersion Preparation Kit The chemical mechanical polishing aqueous dispersion preparation kit (hereinafter also simply referred to as “kit”) according to this embodiment is a chemical mechanical polishing used in the above chemical mechanical polishing method. A chemical mechanical polishing aqueous dispersion preparation kit for preparing an aqueous dispersion for water,
A first composition containing at least (A) a cationic water-soluble polymer and an acidic compound, and having a pH of 1 to 3;
A second composition comprising at least (B) an iron (III) compound and water;
A third composition containing at least (C) colloidal silica and water;
Is a kit configuration.

  According to said kit, since the 1st-3rd composition can be stored as a separate kit structure, it can suppress especially aggregation of (C) colloidal silica contained in a 3rd composition. . Thereby, since the chemical mechanical polishing aqueous dispersion can be obtained by mixing the kit containing the first to third compositions at each use, the chemical mechanical polishing aqueous dispersion always having a certain quality can be obtained. Can be provided. Hereinafter, each kit configuration will be described in detail.

2.1 First Composition The kit according to this embodiment comprises a first composition containing at least (A) a cationic water-soluble polymer and an acidic compound and having a pH of 1 to 3. Kit configuration. In order to mix and neutralize a 1st composition with a 3rd composition, pH is adjusted to 1-3 acidity.

  (A) About a cationic water-soluble polymer, what was described in "1.5.1 (A) Cationic water-soluble polymer" can be used.

  The acidic compound is a pH adjuster for adjusting the pH of the first composition to an acidity of 1 to 3. Examples of acidic compounds include organic acids and inorganic acids. The organic acid is preferably a compound having two or more carboxyl groups in the molecule, and examples thereof include maleic acid, malonic acid, and citric acid. Examples of inorganic acids include nitric acid, sulfuric acid, hydrochloric acid and the like. Among these acidic compounds, it is preferable to use maleic acid and malonic acid. As the acidic compound used in the first composition, those exemplified above may be used alone or in combination of two or more.

  Examples of the dispersion medium include water, a mixed medium of water and alcohol, a mixed medium containing water and an organic solvent compatible with water, and the like. Among these, water, a mixed medium of water and alcohol are preferably used, and water is more preferably used.

  The pH of the first composition is 1 to 3, preferably 1 to 2.5, and more preferably 1 to 2. The first composition is for preparing an aqueous dispersion for chemical mechanical polishing for polishing a wiring layer containing tungsten by mixing with a second composition and a third composition which will be described later. is there. When the pH of the first composition is greater than 3, the third composition described later cannot be sufficiently neutralized and is optimal as an aqueous dispersion for chemical mechanical polishing for polishing a wiring layer containing tungsten. It becomes difficult to adjust to pH 1-3.

2.2 2nd composition The kit which concerns on this embodiment makes the kit composition the 2nd composition containing at least (B) iron (III) compound and water. From the viewpoint of ensuring storage stability, the second composition preferably does not contain components contained in the first composition or the third composition described later.

  (B) About an iron (III) compound, what was described in "1.5.2 (B) Iron (III) compound" can be used.

  Examples of the dispersion medium include water, a mixed medium of water and alcohol, a mixed medium containing water and an organic solvent compatible with water, and the like. Among these, water, a mixed medium of water and alcohol are preferably used, and water is more preferably used.

2.3 Third Composition The kit according to this embodiment has a third composition containing at least (C) colloidal silica and water as a kit configuration.

  (C) About colloidal silica, what was described in "1.5.3 (C) colloidal silica" can be used.

  Examples of the dispersion medium include water, a mixed medium of water and alcohol, a mixed medium containing water and an organic solvent compatible with water, and the like. Among these, water, a mixed medium of water and alcohol are preferably used, and water is more preferably used.

  The pH of the third composition is preferably adjusted to 8 to 11, more preferably 8 to 10. The reason why it is preferable to adjust the pH of the third composition to 8 to 11 is as follows.

  In general, colloidal silica has a siloxane structure, and negatively charged silica particles are dispersed in water to form a colloidal shape. The negative charge depends on the pH value and increases with higher pH values. By having a negative charge, sodium ions and potassium ions in the aqueous solution are surrounded around the very vicinity of the silica particles, and an electric double layer is formed. The electric potential of the outermost surface of this electric double layer is called a zeta potential. When the zeta potential of the colloidal silica in the slurry is small, the repulsive force between the particles becomes small and aggregation tends to occur. Therefore, by adjusting the pH value to a weak alkalinity of 8 to 11, the zeta potential can be set to a certain value or more, and aggregation of colloidal silica can be suppressed.

  When the pH of the third composition is smaller than the above range, the (C) colloidal silica tends to aggregate. On the other hand, when the pH of the third composition is larger than the above range, the (C) colloidal silica may be partially dissolved by long-term storage, and desired polishing characteristics may not be obtained.

  Examples of the pH adjuster of the third composition include basic compounds such as organic bases and inorganic bases. Examples of the organic base include tetramethylammonium hydroxide and triethylamine. Examples of the inorganic base include ammonia, potassium hydroxide, sodium hydroxide and the like. Among these basic compounds, it is preferable to use ammonia or potassium hydroxide. As the basic compound used in the third composition, those exemplified above may be used alone or in combination of two or more.

2.4 Preparation method of chemical mechanical polishing aqueous dispersion The concentration of each component in the first composition, the second composition, and the third composition is finally prepared by mixing them. There is no particular limitation as long as it becomes the above-described first or second chemical mechanical polishing aqueous dispersion.

  In the mixing method of the first to third compositions, two or more compositions containing one or more of each component at a high concentration are prepared, and they are diluted and mixed to a desired concentration at the time of use. Then, it may be used for chemical mechanical polishing.

  For example, (A) a first composition having a concentration five times that of a cationic water-soluble polymer contained in a chemical mechanical polishing aqueous dispersion used during polishing, and (B) an iron (III) compound A second composition having a concentration 10 times as high as that of (C) and a third composition having a concentration 5 times that of colloidal silica are prepared. In such a case, if the weight ratio of the first composition: the second composition: the third composition: water is blended so as to be 2: 1: 2: 5, the desired chemical mechanical polishing aqueous dispersion is obtained. Can be obtained.

  Examples of the method for mixing and supplying the first to third compositions include the following aspects (a) to (c).

  (A) First to third compositions are mixed in advance to prepare a chemical mechanical polishing aqueous dispersion. The obtained chemical mechanical polishing aqueous dispersion is supplied onto the turntable from the slurry supply nozzle.

  (B) Either one of the first composition and the second composition and the third composition are mixed in advance, and each composition is separately supplied onto the turntable from the slurry supply nozzle. Mix them on the turntable.

  (C) The first to third compositions are separately supplied from the slurry supply nozzle onto the turntable, and are mixed on the turntable.

  Here, “mixing the composition in advance” refers to a mixing method other than the method of separately supplying the composition on the turntable and mixing while polishing on the turntable. For example, mixing in the line.

3. Examples Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples.

3.1 Preparation of aqueous colloidal silica dispersion No. 3 water glass (silica concentration: 24% by mass) was diluted with water to obtain a diluted sodium silicate aqueous solution having a silica concentration of 3.0% by mass. This diluted sodium silicate aqueous solution was passed through a hydrogen-type cation exchange resin layer to obtain an active silicic acid aqueous solution of pH 3.1 from which most of the sodium ions were removed. Thereafter, 10% by weight aqueous potassium hydroxide solution was immediately added with stirring to adjust the pH to 7.2, followed by further heating and boiling for 3 hours. To the resulting aqueous solution, 10 times the amount of the active silicic acid aqueous solution whose pH was previously adjusted to 7.2 was added little by little to grow colloidal silica.

  Next, the dispersion aqueous solution containing the colloidal silica was concentrated under reduced pressure to obtain an aqueous colloidal silica dispersion having a silica concentration of 32.0 mass% and a pH of 9.8. The obtained colloidal silica aqueous dispersion was again passed through the hydrogen-type cation exchange resin layer to remove most of sodium, and then a 10% by mass potassium hydroxide aqueous solution was added, and the silica particle concentration: 28.0% by mass. %, PH: 10.0 to obtain colloidal silica aqueous dispersion A.

  The average particle size calculated from the specific surface area measured using the BET method was 18 nm. In the surface area measurement of the colloidal silica by the BET method, the value obtained by measuring the colloidal silica recovered by concentrating and drying the colloidal silica aqueous dispersion A was used.

  Further, it contains colloidal silica having an average particle diameter of 45 nm calculated from the specific surface area measured using the BET method by the same method as above while controlling the heat aging time, the type and amount of the basic compound, etc. A colloidal silica aqueous dispersion B having a silica particle concentration of 28.0% by mass and a pH of 10.0 was obtained.

3.2 Preparation of Chemical Mechanical Polishing Aqueous Dispersion Preparation Kit 3.2.1 Preparation of First Composition (a) 81.3 parts by weight of ion-exchanged water is placed in a polyethylene bottle, and maleic acid is added thereto. 2 parts by mass were added and stirred to dissolve. Next, (A) 16.7 parts by mass of a 30% by mass aqueous solution of polyethyleneimine (trade name “Epomin P-1000”, number average molecular weight 16,000) as a cationic water-soluble polymer is added and mixed. A composition (a) was obtained.

3.2.2 Preparation of second composition (b) In a polyethylene bottle, a 38 mass% iron (III) nitrate aqueous solution (trade name "FN376") so that the concentration of ferric nitrate is 30 mass%. , Manufactured by Tama Chemical Co., Ltd.), and the remaining ion-exchanged water was added and stirred to obtain a second composition (b).

3.2.3 Preparation of third compositions (c1) and (c2) 89.3 of the colloidal silica aqueous dispersion A prepared in “3.1 Preparation of aqueous colloidal silica dispersion” in a polyethylene bottle. The third composition (c1) was obtained by adding 10.7 parts by mass of ion exchange water and further adding 1 part by mass of ion exchange water.

  Similarly, 89.3 parts by mass of colloidal silica water dispersion B prepared in “3.1 Preparation of aqueous colloidal silica dispersion” is added to a polyethylene bottle, and 10.7 parts by mass of ion exchange water is further added. As a result, a third composition (c2) was obtained.

3.3 Preparation of Chemical Mechanical Polishing Aqueous Dispersion About 50 parts by mass of ion-exchanged water and 0.14 parts by mass of the first composition (a) were added and stirred. Next, 16.7 parts by mass of the second composition (b) and 32.0 parts by mass of the third composition (c1) were added thereto and stirred for 15 minutes. Finally, after adding maleic acid and ion-exchanged water so that the total amount of all components is 100 parts by mass and a predetermined pH, the chemical machine is used in the first polishing step by filtering with a filter having a pore size of 5 μm. A polishing aqueous dispersion S1-1 was obtained.

  In the chemical mechanical polishing aqueous dispersions S1-2 to S1-10 used in the first polishing step, the mixing ratio of the first to third compositions is appropriately changed so that the components (A) to (C) are represented. It obtained similarly to the preparation method of said chemical mechanical polishing aqueous dispersion S1-1 except having set so that it might become the kind and content of Tables 1-2.

  About 43 parts by mass of ion-exchanged water and 1.6 parts by mass of the first composition (a) were added and stirred. Next, 6.7 parts by mass of the second composition (b) and 48.0 parts by mass of the third composition (c1) were added thereto and stirred for 15 minutes. Finally, after adding maleic acid and ion-exchanged water so that the total amount of all components is 100 parts by mass and a predetermined pH, the chemical machine is used in the second polishing step by filtering through a filter having a pore size of 5 μm. A polishing aqueous dispersion S2-1 was obtained.

  In the chemical mechanical polishing aqueous dispersions S2-2 to S2-10 used in the second polishing step, the mixing ratio of the first to third compositions is appropriately changed so that the components (A) to (C) are represented. 1 It was obtained in the same manner as the method for preparing the chemical mechanical polishing aqueous dispersion S2-1 except that the types and contents described in Table 2 were set.

3.4 Evaluation Method A polishing pad made of a porous polyurethane (made by Nitta Haas, product number “IC1000”) is mounted on a chemical mechanical polishing apparatus (model “EPO112” manufactured by Ebara Corporation), and the following polishing rate measuring substrate The first polishing step was performed under the following polishing conditions while supplying any one of the chemical mechanical polishing aqueous dispersions S1-1 to S1-10. Next, the second polishing step is performed under the following polishing conditions while supplying any one of the chemical mechanical polishing aqueous dispersions S2-1 to S2-10 for the polishing rate measuring substrate after the first polishing step. The polishing rate and selectivity were evaluated by the following methods. The results are shown in Tables 1 and 2.

(1) Polishing Rate Measurement Substrate Patterned substrate (manufactured by SEMATECH INTERNIONAL, 8-inch wafer with a 400 nm PETEOS film formed on a 400 nm deep “SEMATECH
854 "pattern, a 25 nm Ti / TiN film was stacked, and then a 600 nm tungsten film was further stacked. A schematic cross-sectional view of the patterned substrate is shown in FIG.

(2) Polishing conditions and head rotation speed: 80 rpm
・ Head load: 250 hPa
・ Table rotation speed: 85rpm
-Feed rate of chemical mechanical polishing aqueous dispersion: 120 mL / min

(3) Polishing time The time required for the first polishing step is the time until the tungsten film other than the portion embedded in the concave portion on the patterned substrate is removed, and the Ti / TiN film or the PETEOS film below it is exposed. It was time. Whether or not the tungsten film was removed was determined by reading the current change in the table torque of the polishing machine.

  The second polishing step was performed for 40 seconds on the patterned substrate after the first polishing step. Note that the time set in the second polishing step is not particularly limited and can be appropriately adjusted depending on the purpose of securing desired flatness and the polishing amount of the PETEOS film.

  The time required for all steps is preferably 160 seconds or shorter, and more preferably 140 seconds or shorter.

(4) Evaluation method of polishing rate The polishing rate of the tungsten film and the PETEOS film in the second polishing step was calculated by the following method, and the ratio of the polishing rate was calculated.

  As for the polishing rate of the PETEOS film, a tungsten wiring width (line, L) / insulating layer width (space, S) using an optical interference film thickness measuring device (Nanometrics Japan, model “Nano Spec 6100”). ) Measured the film thickness after polishing in the pattern portions of 100 μm / 100 μm, respectively, and calculated the polishing rate from the film thickness decreased by chemical mechanical polishing and the polishing time.

  Regarding the polishing rate of the tungsten film, the tungsten wiring width (line, L) / insulating layer width (space, measured by using a high resolution profiler (model “HRP240ETCH” manufactured by KLA Tencor) from the thickness of the PETEOS film). The polishing rate was calculated from the film thickness before and after the chemical mechanical polishing process and the polishing time for the calculated tungsten wiring film thickness by subtracting the dishing amount (angstrom) in the pattern portions of S) of 100 μm / 100 μm.

  In addition, it can be determined that the selectivity (tungsten film polishing rate / PETEOS film polishing rate) is 0.5 to 0.9. On the other hand, if it is less than 0.4 or greater than 0.9, the balance of the selection ratio is impaired, and it can be determined that it is defective.

(5) Erosion Evaluation Method Using a high-resolution profiler (model “HRP240ETCH”, manufactured by KLA Tencor) for the polished surface of the patterned substrate after the first polishing step and the second polishing step, the tungsten wiring width (line, L) / Erosion amount (nm) in a pattern portion having a tungsten wiring interval (space, S) of 1.5 μm / 0.5 μm, respectively, was measured. The results are also shown in Tables 1 and 2. Note that the erosion amount is displayed as a negative value when it is convex above the reference surface (upper surface of the insulating film). The erosion amount is preferably −5 to 20 nm, and more preferably −2 to 15 nm.

3.5 Evaluation Results When the two-step polishing method described in Examples 1 to 5 was performed, the erosion in the first polishing step can be suppressed to 30 nm or less for any of the examples, and the second polishing step The erosion in can be further reduced. Moreover, since the total polishing time was 160 seconds or less in any of the examples, it could be evaluated that the polishing was performed at a high speed. As described above, when the two-step polishing method described in Examples 1 to 5 was performed, the patterned substrate could be polished at high speed and smoothly while suppressing the occurrence of erosion.

In the chemical mechanical polishing method of Comparative Example 1, the same chemical mechanical polishing aqueous dispersion is used in the first polishing step and the second polishing step, and M _A1 / M _A2 exceeds 0.3. If it did so, the protective effect with respect to a tungsten film became inadequate in the 2nd grinding | polishing process, and the elimination property of the initial level | step difference fell.

The chemical mechanical polishing method of Comparative Example 2 uses the same chemical mechanical polishing aqueous dispersion in the first polishing step and the second polishing step, and M _A1 / M _A2 exceeds 0.3. As a result, the protective action of the projections on the tungsten surface becomes excessive in the first polishing step, and thus a great polishing time is required and polishing cannot be performed at high speed.

In the chemical mechanical polishing method of Comparative Example 3, M _A1 / M _A2 is less than 0.004. Therefore, a sufficient protective film cannot be formed in the concave portion on the tungsten surface in the first polishing step, and the resolvability of the initial step is lowered. In addition, the tungsten film was excessively protected in the second polishing step, so that the tungsten wiring could hardly be cut and protolution occurred.

In the chemical mechanical polishing method of Comparative Example 4, M _A1 / M _A2 exceeds 0.3. For this reason, in the first polishing step, the protective action of the convex portion on the tungsten surface becomes excessive, the resolvability of the initial step is lowered, and a great amount of polishing time is required. Further, in the second polishing step, the protective effect of the tungsten film was insufficient and erosion was deteriorated.

In the chemical mechanical polishing method of Comparative Example 5, M _A1 / M _A2 is less than 0.004. The second chemical mechanical polishing aqueous dispersion S2-10 has (B) content of iron (III) compound (M _B ) [mass%] less than the above range, and (C) content of colloidal silica ( M _C ) [% by mass] exceeds the above range. For this reason, the second chemical mechanical polishing aqueous dispersion S2-10 aggregated and settled and could not be evaluated.

DESCRIPTION OF SYMBOLS 10 ... Base | substrate, 12 ... Silicon oxide film, 14 ... Via hole, 16 ... Barrier metal film, 18 ... Tungsten film, 42 ... Slurry supply nozzle, 44 ... Slurry, 46 ... Polishing cloth, 48 ... Turntable, 50 ... Semiconductor substrate 52 ... Carrier head, 54 ... Water supply nozzle, 56 ... Dresser, 100 ... Object to be treated, 200 ... Chemical mechanical polishing apparatus

Claims (12)

A first polishing step of chemically mechanically polishing a tungsten film deposited on the barrier metal film using the first chemical mechanical polishing aqueous dispersion;
A second polishing step of simultaneously chemical mechanical polishing the tungsten film, the barrier metal film, and the silicon oxide film using the second chemical mechanical polishing aqueous dispersion;
A chemical mechanical polishing method comprising:
The first chemical mechanical polishing aqueous dispersion and the second chemical mechanical polishing aqueous dispersion include at least (A) a cationic water-soluble polymer, (B) an iron (III) compound, and (C). Colloidal silica, and
The content (M _A1 ) [mass%] of the component (A) in the first chemical mechanical polishing aqueous dispersion and the component (A) in the second chemical mechanical polishing aqueous dispersion. The chemical mechanical polishing method, wherein the content ratio (M _A1 / M _A2 ) to the content (M _A2 ) [mass%] is 0.004 to 0.3. In claim 1,
The M _A1 is 0.001% by mass to 0.01% by mass, and
The M _A2 is a chemical mechanical polishing method, which is 0.05% by mass to 0.2% by mass. In claim 1 or claim 2,
The chemical mechanical polishing method, wherein the cationic water-soluble polymer (A) is polyethyleneimine. In any one of Claims 1 to 3,
(A) The chemical mechanical polishing method wherein the number average molecular weight of the cationic water-soluble polymer is 200 to 1,000,000. In any one of Claims 1 thru | or 4,
The chemical mechanical polishing method, wherein the (B) iron (III) compound is at least one selected from ferric nitrate and ferric sulfate. In any one of Claims 1 thru | or 5,
The content of the component (B) (M _B1) and the content of the component (B) of the second chemical mechanical polishing aqueous dispersion in said first chemical mechanical polishing aqueous dispersion (M _B2 ) Is a chemical mechanical polishing method in which all are 0.01% by mass to 20% by mass. In any one of Claims 1 thru | or 6,
The content (M _C1 ) of the component (C) in the first chemical mechanical polishing aqueous dispersion and the content (M _C2 ) of the component (C) in the second chemical mechanical polishing aqueous dispersion. ) Is a chemical mechanical polishing method in which all are 1% by mass to 20% by mass. In any one of Claims 1 thru | or 7,
The chemical mechanical polishing method, wherein the average particle diameter calculated from the specific surface area of the (C) colloidal silica measured using the BET method is 10 nm to 60 nm. In any one of Claims 1 thru | or 8,
A chemical mechanical polishing method, wherein the first polishing step and the second polishing step are continuously performed on the same polishing table. In any one of Claims 1 thru | or 9,
Furthermore, the chemical mechanical polishing method including a cleaning step of removing iron adsorbed on the object to be processed after the second polishing step. A chemical mechanical polishing aqueous dispersion preparation kit for preparing a chemical mechanical polishing aqueous dispersion for use in the chemical mechanical polishing method according to any one of claims 1 to 10,
A first composition containing at least (A) a cationic water-soluble polymer and an acidic compound, and having a pH of 1 to 3;
A second composition comprising at least (B) an iron (III) compound and water;
A third composition containing at least (C) colloidal silica and water;
A kit for preparing a chemical mechanical polishing aqueous dispersion.   A semiconductor device manufactured using the chemical mechanical polishing method according to claim 1.

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