JP2010258416A - Chemical mechanical polishing aqueous dispersion, and chemical mechanical polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chemical mechanical polishing aqueous dispersion and a chemical mechanical polishing method for rapidly and flatly polishing a semiconductor wafer containing tungsten. <P>SOLUTION: The chemical mechanical polishing aqueous dispersion for polishing a workpiece provided with a wiring layer containing tungsten contains: (A) a cationic water-soluble polymer; (B) an iron (III) compound; and (C) colloidal silica. The content (M<SB>A</SB>) [mass%] of the (A) component and the content (M<SB>C</SB>) [mass%] of the (C) component have the relationship M<SB>A</SB>/M<SB>C</SB>=0.0001-0.003, and pH is 1-3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an aqueous dispersion for chemical mechanical polishing and a chemical mechanical polishing method.

  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 a chemical mechanical polishing aqueous dispersion used for polishing a tungsten film, there is 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. It has been proposed (see, for example, 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 tungsten film polishing aqueous dispersion that can balance both of these characteristics in a well-balanced manner has not yet been obtained.

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

  An object of the present invention is to provide a chemical mechanical polishing aqueous dispersion and a chemical mechanical polishing method for polishing a semiconductor wafer containing tungsten at high speed and flatly.

The chemical mechanical polishing aqueous dispersion according to the present invention is a chemical mechanical polishing aqueous dispersion for polishing a target object provided with a wiring layer containing tungsten,
(A) a cationic water-soluble polymer;
(B) an iron (III) compound;
(C) colloidal silica;
Containing
The content (M _A ) [mass%] of the component (A) and the content (M _C ) [mass%] of the component (C) have a relationship of M _A / M _C = 0.0001 to 0.003. Have
The pH value is 1 or more and 3 or less.

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

In the chemical mechanical polishing aqueous dispersion according to the invention, the content (MA) [mass%] of the cationic water-soluble polymer ( _A ) is 0.0005 mass% or more and 0.02 mass% or less. be able to.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the number average molecular weight of the cationic water-soluble polymer (A) may be 200 or more and 1,000,000 or less.

  In the chemical mechanical polishing aqueous dispersion according to the present invention, the (B) iron (III) compound may be ferric nitrate.

In the chemical mechanical polishing aqueous dispersion according to the present invention, the content (M _B ) [mass%] of the (B) iron (III) compound may be 0.01 mass% or more and 40 mass% or less. .

In the chemical mechanical polishing aqueous dispersion according to the present invention, the content (M _C ) [mass%] of the (C) colloidal silica may be 1 mass% or more and 40 mass% or less.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the object to be processed may include an insulating film having a via hole and a tungsten film provided on the insulating film via a barrier metal film. .

  The chemical mechanical polishing method according to the present invention is to polish an object to be processed provided with a wiring layer containing tungsten using the chemical mechanical polishing aqueous dispersion.

  According to the chemical mechanical polishing aqueous dispersion, not only can the tungsten film be polished at high speed and flatness, but also the surface to be polished in which the tungsten film and the insulating film coexist can be polished at high speed and flatness while suppressing erosion. 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 the perspective view which showed the chemical mechanical polishing apparatus typically.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

1. Chemical mechanical polishing aqueous dispersion A chemical mechanical polishing aqueous dispersion according to an embodiment of the present invention is a chemical mechanical polishing aqueous dispersion for polishing a target object provided with a wiring layer containing tungsten. (A) a cationic water-soluble polymer, (B) an iron (III) compound, and (C) colloidal silica, and the content (M _A ) [mass%] of the component (A) The content (M _C ) [mass%] of the component (C) has a relationship of M _A / M _C = 0.0001 to 0.003, and the pH value is 1 or more and 3 or less.

  The chemical mechanical polishing aqueous dispersion according to the present embodiment is an object to be processed such as a semiconductor wafer provided with a wiring layer containing tungsten. Specifically, an object to be processed includes a silicon oxide film having a via hole and a tungsten film provided over the silicon oxide film with a barrier metal film interposed therebetween. By using the chemical mechanical polishing aqueous dispersion according to the present embodiment, not only can the tungsten film be polished at high speed and flatness, but also the surface to be polished on which the tungsten film and an insulating film such as a silicon oxide film coexist. Can be polished at high speed and flat while suppressing erosion.

  Each component constituting the chemical mechanical polishing aqueous dispersion according to the present embodiment will be described below.

1.1. (A) Cationic water-soluble polymer The chemical mechanical polishing aqueous dispersion according to the present embodiment contains a cationic water-soluble polymer. It is believed that the cationic water-soluble polymer is easily adsorbed on the tungsten surface to form a protective film. As a result, it can be considered that the polishing rate of tungsten is suppressed because tungsten can be prevented from being oxidized and weakened.

  Examples of the cationic water-soluble polymer include polyalkyleneimine, polyvinylpyrrolidone, polyvinylamine, polyvinylpyridine, polyallylamine, polyvinylpiperazine, polylysine and the like, preferably polyalkyleneimine, more preferably polyethyleneimine. It is. In the chemical mechanical polishing aqueous dispersion according to the present embodiment, the above cationic water-soluble polymers can be used singly or in combination of two or more.

  The content of the cationic water-soluble polymer is preferably 0.0005% by mass or more and 0.02% by mass or less, more preferably 0.001% by mass with respect to the total mass of the chemical mechanical polishing aqueous dispersion. It is 0.01 mass% or less. When the content of the cationic water-soluble polymer is within the above range, the tungsten polishing rate can be suitably suppressed by effectively forming a protective film on the tungsten surface, and the tungsten portion is excessively polished. Therefore, it is considered that dishing and erosion can be suppressed. Furthermore, when the content of the cationic water-soluble polymer is within the above range, the polishing rate of tungsten can be suitably maintained, and chemical mechanical polishing can be completed in an appropriate polishing time. As a result, the process cost can be suppressed, which is considered more practical.

  The number average molecular weight of the cationic water-soluble polymer is preferably 200 or more and 1,000,000 or less, and more preferably 10,000 or more and 100,000 or less. When the number average molecular weight of the cationic water-soluble polymer is in the above range, the polishing rate for tungsten can be suitably suppressed. Furthermore, when the number average molecular weight of the cationic water-soluble polymer is within the above range, the stability of the chemical mechanical polishing aqueous dispersion according to the present embodiment is further improved.

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

1.2. (B) Iron (III) Compound The chemical mechanical polishing aqueous dispersion according to the present embodiment contains an iron (III) compound. The iron (III) compound oxidizes the surface of tungsten and creates a fragile modified layer on the surface of tungsten, thereby promoting the polishing of tungsten.

  The iron (III) compound may be either an organic acid iron salt or an inorganic acid iron salt as long as it has the effects described above. Examples of the iron (III) compound include iron nitrate (III) (hereinafter also referred to as “ferric nitrate”), ammonium iron (III) sulfate, iron (III) perchlorate, iron (III) chloride, and iron sulfate. (III), iron (III) citrate, iron (III) ammonium citrate, iron iron (III) oxalate, and the like. Of these iron (III) compounds, ferric nitrate is particularly preferable. By using ferric nitrate, an oxide is formed on the tungsten surface, and it becomes easy to scrape the oxide with colloidal silica, which will be described later, while maintaining a good polishing rate while suppressing residue, dishing and corrosion. However, a polished surface having flatness can be obtained. The chemical mechanical polishing aqueous dispersion according to the present embodiment can be used singly or in combination of two or more of the above iron (III) compounds.

  The content of the iron (III) compound is preferably 0.01% by mass or more and 40% by mass or less, more preferably 0.05% by mass or more and 20% by mass with respect to the total mass of the chemical mechanical polishing aqueous dispersion. % Or less. If the content of the iron (III) compound is within the above range, the surface of tungsten can be effectively oxidized, so that the polishing rate of tungsten can be further increased and dishing and erosion can be effectively suppressed. It is done.

1.3. (C) Colloidal silica The chemical mechanical polishing aqueous dispersion according to the present embodiment contains colloidal silica. Colloidal silica has the effect of mechanically polishing the tungsten film and the silicon oxide film. As the colloidal silica, one produced by a known method as described in, for example, JP-A No. 2003-109921 can be used.

  The average particle size of the colloidal silica is preferably 10 nm or more and 70 nm or less, more preferably 10 nm or more and 50 nm or less. When the average particle size of the colloidal silica is within the above range, erosion can be suppressed and the pattern wafer can be polished at high speed.

  In addition, the said colloidal silica may mix and use 2 or more types of colloidal silica from which an average particle diameter differs in arbitrary ratios. By using two or more types of colloidal silica in combination, the colloidal silica has a wider particle size distribution. In colloidal silica having such a wide particle size distribution, the colloidal silica having a relatively small particle size acts like a roller on the colloidal silica having a relatively large particle size. The fluidity of the polishing aqueous dispersion can be improved. As a result, it is considered that the chemical mechanical polishing aqueous dispersion can be efficiently supplied between the polishing pad and the object to be polished, and the polishing rate can be improved.

  The average particle diameter of the colloidal silica is a value calculated from the specific surface area measured using the BET method. For the measurement of the specific surface area, for example, a flow type specific surface area automatic measuring device “micrometrics FlowSorb II 2300 (manufactured by Shimadzu Corporation)” or the like can be used. Below, the method of calculating an average particle diameter from the specific surface area of colloidal silica is demonstrated.

Assuming that the shape of the colloidal silica is a true spherical particle, the diameter of the particle is d (nm) and the specific gravity is ρ (g / cm ³ ). The surface area A of n particles is A = nπd ² . N particles mass N becomes N = ρnπd ^3/6. The specific surface area S (m ² / g) is represented by the surface area of all the constituent particles per unit mass of the powder. Then, the specific surface area S of n particles 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 (1)

  The content of colloidal silica is preferably 1% by mass or more and 40% by mass or less, more preferably 1% by mass or more and 30% by mass or less, and particularly preferably based on the total mass of the chemical mechanical polishing aqueous dispersion. Is 1 mass% or more and 20 mass% or less. When the colloidal silica content is within the above range, a sufficient polishing rate for the tungsten film and the silicon oxide film can be obtained, and aggregation of the colloidal silica can be prevented, and an aqueous dispersion for chemical mechanical polishing excellent in stability can be obtained. Tend.

1.4. Other Additives The chemical mechanical polishing aqueous dispersion according to the present embodiment can further contain an oxidizing agent other than the iron (III) compound. Examples of oxidizing agents other than iron (III) compounds include ammonium persulfate, potassium persulfate, hydrogen peroxide, ferrous sulfate, ferrous nitrate, diammonium cerium nitrate, ozone and potassium periodate, peracetic acid, Hypochlorous acid and its salt are mentioned. These oxidizing agents can be used alone or in combination of two or more. Of these oxidizing agents, ammonium persulfate, potassium persulfate, and hydrogen peroxide are particularly preferable in view of oxidizing power, compatibility with the protective film, and ease of handling.

  The content of the oxidizing agent is preferably 0.05% by mass or more and 5% by mass or less, more preferably 0.08% by mass or more and 3% by mass or less, with respect to the total mass of the chemical mechanical polishing aqueous dispersion. is there.

1.5. Content Ratio In the chemical mechanical polishing aqueous dispersion according to the present embodiment, the content (M _A ) [mass%] of the cationic water-soluble polymer (M) and the content (M) of the colloidal silica (M _C ) [% by mass] is characterized by having a relationship of M _A / M _C = 0.0001 to 0.003. The value of M _A / M _C is preferably 0.0002 to 0.0024, more preferably 0.0003 to 0.0022. When the value of M A _/ M _C is within the above range, it is possible to adjust the ratio of the polishing rate of the polishing rate and the insulating film to the tungsten film so as to be substantially 1, and the tungsten film and the insulating film The occurrence of erosion can be suppressed when the surface to be polished that coexists is polished. When the value of M A _/ M _C is less than the above range, the polishing rate of the tungsten film becomes larger than the polishing rate of the insulating film, polishing the surface so as to coexist with the tungsten film and the insulating film It is impossible to suppress the occurrence of erosion. On the other hand, when the value of M A _/ M _C exceeds the above range, the polishing rate for the tungsten film decreases, undesirably increases the processing time of the pattern wafer.

1.6. pH
The pH of the chemical mechanical polishing aqueous dispersion according to the present embodiment is in the range of 1 to 3, preferably in the range of 1 to 2. When the pH is in the above range, it is possible to obtain a good surface to be polished with respect to the surface to be polished such that the tungsten film and the insulating film coexist. When the pH exceeds 3, the polishing rate for the tungsten film and the silicon oxide film is remarkably reduced. Further, the colloidal silica particles may be settled and separated, and the storage stability as a chemical mechanical polishing aqueous dispersion may be deteriorated. On the other hand, if the pH is less than 1, the polishing rate with respect to the tungsten film increases, and thus erosion may not be suppressed.

  The pH described above may be selected from inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid; organic acids such as maleic acid, malonic acid, tartaric acid and oxalic acid; strong alkalis such as potassium hydroxide, ammonia and tetramethylammonium hydroxide. And can be adjusted within the above range.

  The pH described above can be appropriately adjusted with a catalyst such as iron nitrate so that the chemical mechanical polishing aqueous dispersion is strongly acidic within the recommended pH range. And the polishing surface with higher flatness can be obtained by adjusting the addition amount of an additive according to a grinding | polishing target object.

2. Chemical Mechanical Polishing Method The chemical mechanical polishing method according to the present embodiment uses a chemical machine to treat an object including an insulating film having a via hole and a tungsten film provided on the insulating film via a barrier metal film. A polishing method comprising: a first polishing treatment step of polishing only the tungsten film using the chemical mechanical polishing aqueous dispersion; and the tungsten film using the chemical mechanical polishing aqueous dispersion. And a second polishing process step of polishing the barrier metal film and the insulating film simultaneously.

  Hereinafter, the chemical mechanical polishing method according to the present embodiment will be described in detail with reference to the drawings.

2.1. FIG. 1 shows an example of an object 100 to be applied to the chemical mechanical polishing method according to the present embodiment.

  (1) First, as shown in FIG. 1, a base 10 is prepared. The base 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. Next, a silicon oxide film 12 that is an insulating film is formed on the substrate 10 by using a CVD method or a thermal oxidation method.

  (2) Next, the silicon oxide film 12 is patterned. Using this as a mask, a via hole 14 is formed on the silicon oxide film 12 by applying a photolithography method.

  (3) Next, the barrier metal film 16 is formed on the surface of the silicon oxide film 12 and the inner wall surface of the via hole 14 by applying sputtering. Since electrical contact between tungsten and silicon is not very good, good electrical contact is realized by interposing a barrier metal film. Examples of the barrier metal film 16 include titanium and / or titanium nitride.

  (4) Next, the tungsten film 18 is formed by applying the CVD method.

  The to-be-processed object 100 is formed of the above process.

2.2. Chemical mechanical polishing method 2.2.1. First Polishing Process Step The first polishing process step polishes the barrier metal film 16 and the tungsten film 18 until the silicon oxide film 12 is exposed, using the chemical mechanical polishing aqueous dispersion described above, as shown in FIG. It is a process. Since the chemical mechanical polishing aqueous dispersion described above has an excellent polishing action not only on the tungsten film but also on the barrier metal film, the barrier metal film 16 and the tungsten film 18 can be polished and removed in the same processing step. it can.

2.2.2. Second Polishing Process Step The second polishing process step is a step of simultaneously polishing the barrier metal film 16, the tungsten film 18, and the silicon oxide film 12 by using the chemical mechanical polishing aqueous dispersion as shown in FIG. It is. The chemical mechanical polishing aqueous dispersion described above has a non-selective polishing property with respect to the tungsten film and the silicon oxide film, so that a finished surface with extremely excellent flatness can be obtained by the second polishing process.

  Here, the chemical mechanical polishing aqueous dispersion used in the second polishing treatment step is the concentration of (B) the iron (III) compound contained in the chemical mechanical polishing aqueous dispersion used in the first polishing treatment step. The composition range may be appropriately changed and used. By adjusting the concentration of the (B) iron (III) compound so that the ratio between the polishing rate for the tungsten film and the polishing rate for the silicon oxide film is approximately 1, a finished surface with better flatness can be obtained. Can do.

2.2.3. Chemical Mechanical Polishing Device In the first polishing processing step and the second polishing processing 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.

  The polishing load of the carrier head 52 can be selected within the range of 10 to 980 hPa, and preferably 30 to 490 hPa. 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. The flow rate of the slurry 44 supplied from the slurry supply nozzle 42 can be selected within the range of 10 to 1,000 mL / min, and preferably 50 to 400 mL / 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 Product type, “Mirra”, “Reflexion” and the like.

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

3.1. Preparation of aqueous dispersion for chemical mechanical polishing 3.1.1. Preparation of Colloidal Silica Water Dispersion No. 3 water glass (silica concentration 24 mass%) was diluted with water to obtain a diluted sodium silicate aqueous solution having a silica concentration of 3.0 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. This colloidal silica aqueous dispersion was passed again through the hydrogen-type cation exchange resin layer to remove most of the sodium, and then added with a 10% by mass potassium hydroxide aqueous solution to obtain a silica particle concentration of 28.0% by mass, A colloidal silica aqueous dispersion having a pH of 10.0 was obtained.

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

  Furthermore, the average particle size calculated from the specific surface area measured using the BET method was 15 nm, 25 nm, 45 nm, respectively, by the same method as above while controlling the heat aging time, the type and amount of the basic compound, etc. A 60 nm colloidal silica aqueous dispersion was obtained.

3.1.2. Preparation of Chemical Mechanical Polishing Aqueous Dispersion A colloidal silica aqueous dispersion having an average particle diameter of 18 nm containing 50 parts by mass of ion-exchanged water and 4.5 parts by mass in terms of silica is placed in a polyethylene bottle. Polyethyleneimine (number average molecular weight: 16,000) aqueous solution was added in an amount corresponding to 0.0005 parts by mass in terms of polymer amount. Next, 4 parts by mass of ferric nitrate was added and stirred for 15 minutes. Finally, after adding nitric acid and ion-exchanged water so that the total amount of all components is 100 parts by mass and a predetermined pH, the aqueous dispersion A for chemical mechanical polishing is obtained by filtering with a filter having a pore size of 5 μm. It was.

  (A) Cationic water-soluble polymer, (B) Iron (III) compound, (C) The above chemical mechanical polishing aqueous system except that the colloidal silica is changed to the components and contents shown in Tables 1 to 3 Chemical mechanical polishing aqueous dispersions B to U were produced in the same manner as the dispersion A preparation method. The number average molecular weight of the polyallylamine used in the chemical mechanical polishing aqueous dispersion I was 60,000. The chemical mechanical polishing aqueous dispersion G uses two types of colloidal silica having different average particle diameters. The average particle diameter calculated from the specific surface area measured using the BET method after mixing is 22 0.5 nm.

3.2. Evaluation Method Basics of an aqueous dispersion for chemical mechanical polishing by calculating a ratio between a polishing rate of a tungsten film measured by polishing a film formed on an unpatterned blanket wafer and a polishing rate of a PETEOS film The mechanical polishing characteristics can be confirmed.

  However, it is known that in a CMP of a patterned wafer in which a metal film is deposited on an insulating film in which a groove to be a wiring pattern is formed, a portion that is locally excessively polished is generated. This is because the surface of the pattern wafer before CMP is uneven on the surface of the metal film reflecting the groove that becomes the wiring pattern, and when CMP is performed, locally high pressure is applied according to the pattern density. This is because the polishing rate is increased.

  Therefore, in order to confirm the polishing characteristics in the actual CMP process, it is necessary to polish a pattern wafer simulating a semiconductor substrate and evaluate its polishing rate and erosion. For this reason, it evaluated using the following pattern wafer.

  A porous polyurethane polishing pad (Nitta Haas, product number “IC1000”) is attached to a chemical mechanical polishing apparatus (Ebara Manufacturing Co., Ltd., model “EPO112”), and any of chemical mechanical polishing aqueous dispersions A to U While supplying the above, chemical mechanical polishing treatment was performed on the following polishing rate measurement substrate under the following polishing conditions, and the polishing rate and selectivity were evaluated by the following method. The results are shown in Tables 1 to 3.

(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 carrier head rotation speed: 80 rpm
・ Carrier head load: 250 hPa
・ Turntable rotation speed: 85rpm
-Feed rate of chemical mechanical polishing aqueous dispersion: 120 mL / min

(3) Evaluation Method of Erosion Amount and Polishing Time The time required for polishing the substrate with the above pattern until the PETEOS film was exposed and the PETEOS film was removed to 50 nm was determined as the polishing time. Further, the polished surface of the substrate with a pattern after the polishing process is made using a high resolution profiler (manufactured by KLA Tencor, model “HRP240ETCH”), and the tungsten wiring width (line, L) / tungsten wiring interval (space, S) is The amount of erosion (nm) in each 1.5 μm / 0.5 μm pattern portion was measured. The results are shown in Tables 1 to 3. 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 30 nm, and more preferably −2 to 20 nm.

  Moreover, it can be judged that the polishing time of the pattern wafer is preferably 200 seconds or less, and more preferably 150 seconds or less.

(4) Polishing rate evaluation method The patterned substrate subjected to the above evaluation is further polished for 30 seconds, and the polishing rate of the tungsten film and the polishing rate of the PETEOS film are calculated by the following methods. The ratio 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 (manufactured by Nanometrics Japan, model “Nano Spec 6100”). ) Measured the film thickness after the polishing treatment 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.

  As for the tungsten polishing rate, the tungsten wiring width (line, L) / insulating layer width (space, S) measured from the film thickness of the PETEOS film using a high resolution profiler (KLA Tencor, model “HRP240ETCH”). ) Was subtracted from the dishing amount (angstrom) in the pattern portion of 100 μm / 100 μm, and 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.

  In addition, it can be judged that the selectivity (the polishing rate of the tungsten film / the polishing rate of the silicon oxide film) is 0.7 to 1.3. On the other hand, if it is less than 0.7 or greater than 1.3, the balance of the selection ratio is impaired, and it can be determined that it is defective.

3.3. Evaluation Results When the chemical mechanical polishing aqueous dispersions of Examples 1 to 13 were used, erosion was also generated on the polished surface where the tungsten film and the PETEOS film coexisted in the patterned polishing substrate. It was possible to polish smoothly at high speed while suppressing.

The chemical mechanical polishing aqueous dispersion of Comparative Example 1 has a polyethyleneimine content of 0.0005% by mass as in Example 1, but the content ratio (M _A / M _C ) is less than 0.0001. It has become. Therefore, the ratio between the polishing rate of the tungsten film and the polishing rate of the PETEOS film was 3.04, and the erosion was clearly deteriorated.

Chemical mechanical polishing aqueous dispersion of Comparative Example 2, the value of the content ratio _(M A / M _C) is greater than 0.003. Therefore, although the ratio between the polishing rate of the tungsten film and the polishing rate of the PETEOS film is 0.83, it is not possible to suppress an increase in the pattern wafer polishing time.

  The chemical mechanical polishing aqueous dispersion of Comparative Example 3 does not contain (A) a cationic water-soluble polymer. Therefore, the polishing rate of the tungsten film could not be suppressed, and the ratio between the polishing rate of the tungsten film and the polishing rate of the PETEOS film was increased to 4.92. Moreover, deterioration of erosion was recognized.

The chemical mechanical polishing aqueous dispersion of Comparative Example 4 has a content ratio (M _A / M _C ) of less than 0.0001 and a pH of less than 1. Therefore, the polishing rate of the tungsten film could not be suppressed, and the ratio between the polishing rate of the tungsten film and the polishing rate of the PETEOS film was as large as 2.05. Moreover, deterioration of erosion was recognized.

  The chemical mechanical polishing aqueous dispersion of Comparative Example 5 has a pH exceeding 3. Therefore, the polishing rate with respect to the tungsten film and the PETEOS film is remarkably reduced, and a good surface to be polished cannot be obtained and evaluation cannot be performed.

  The chemical mechanical polishing aqueous dispersion of Comparative Example 6 does not contain an iron (III) compound. For this reason, the polishing rate for the tungsten film is remarkably reduced, and the polishing cannot be performed.

  The chemical mechanical polishing aqueous dispersion of Comparative Example 7 uses hydrogen peroxide exhibiting an oxidizing action instead of the iron (III) compound. For this reason, the polishing rate for the tungsten film is remarkably reduced, and the polishing cannot be performed.

  The chemical mechanical polishing aqueous dispersion of Comparative Example 8 uses ferrous nitrate, which is an iron (II) compound, instead of the iron (III) compound. For this reason, the polishing rate for the tungsten film is remarkably reduced, and the polishing cannot be performed.

As described above, the chemical mechanical polishing aqueous dispersion according to the present invention contains (A) a cationic water-soluble polymer, (B) an iron (III) compound, and (C) colloidal silica. ) The ratio (M _A / M _C ) of the content M _A of the component and the content M _{C of the} component (C) is specified in the range of 0.0001 to 0.003, and the pH is specified in the range of 1 to 3. As a result, it was shown that not only the tungsten film can be polished at high speed and flat, but also the surface to be polished in which the tungsten film and the insulating film coexist can be polished at high speed and flat while suppressing erosion. .

  The chemical mechanical polishing aqueous dispersion according to the present invention includes Cu, Al, W, Ti, TiN, Ta, TaN, V, Mo, Ru, Zr, Mn, Ni, Fe, Ag, Mg, Mn, and Si. It is expected to be effective for a laminated structure containing these elements or a structure in which no barrier metal is substantially present.

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 (9)

An aqueous dispersion for chemical mechanical polishing for polishing an object to be processed provided with a wiring layer containing tungsten,
(A) a cationic water-soluble polymer;
(B) an iron (III) compound;
(C) colloidal silica;
Containing
The content (M _A ) [mass%] of the component (A) and the content (M _C ) [mass%] of the component (C) have a relationship of M _A / M _C = 0.0001 to 0.003. Have
An aqueous dispersion for chemical mechanical polishing having a pH value of 1 or more and 3 or less. In claim 1,
The (A) cationic water-soluble polymer is an aqueous dispersion for chemical mechanical polishing, which is polyethyleneimine. In claim 1 or claim 2,
The content (M _A ) [mass%] of the cationic water-soluble polymer (A) is an aqueous dispersion for chemical mechanical polishing that is 0.0005 mass% or more and 0.02 mass% or less. In any one of Claims 1 to 3,
The number average molecular weight of said (A) cationic water-soluble polymer is 200-1,000,000, The chemical mechanical polishing aqueous dispersion. In any one of Claims 1 thru | or 4,
The aqueous dispersion for chemical mechanical polishing, wherein the (B) iron (III) compound is ferric nitrate. In any one of Claims 1 thru | or 5,
The chemical mechanical polishing aqueous dispersion, wherein the content (M _B ) [% by mass] of the (B) iron (III) compound is 0.01% by mass to 40% by mass. In any one of Claims 1 thru | or 6,
The content (M _C ) [mass%] of the (C) colloidal silica is an aqueous dispersion for chemical mechanical polishing that is 1 mass% or more and 40 mass% or less. In any one of Claims 1 thru | or 7,
The object to be processed is a chemical mechanical polishing aqueous dispersion including an insulating film having a via hole and a tungsten film provided on the insulating film via a barrier metal film.   A chemical mechanical polishing method for polishing a target object provided with a wiring layer containing tungsten, using the chemical mechanical polishing aqueous dispersion according to claim 1.

Images