JP2008112969A - Polishing liquid, and polishing method using the polishing liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing liquid for metals which makes polishing possible without lowering a polishing load and a polishing speed by lowering polishing frictional force by paying attention to the dielectric constant of the polishing liquid, and to provide a polishing method using it. <P>SOLUTION: The polishing liquid for metals comprises water, an oxidant, an oxidized metal resolvent, a protective film forming agent and a solvent whose dielectric constant is lower than that of the water, and 3 to 30 mass% of the solvent whose dielectric constant is lower than that of the water is contained in the polishing liquid for metals. Further, the polishing liquid for metals contains polishing particles and the polishing method for polishing a surface to be polished by relatively moving a polishing cloth and a substrate while supplying the polishing liquid for metals are provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a metal polishing liquid in a wiring process of a semiconductor device and a polishing method using the polishing liquid.

  In recent years, new microfabrication techniques have been developed along with higher integration and higher performance of semiconductor integrated circuits (LSIs). The chemical mechanical polishing (CMP) method is one of them, and is a technique frequently used in the LSI manufacturing process, particularly in the multilayer wiring formation process, planarization of the interlayer insulating film, metal plug formation, embedded wiring formation (for example, (See Patent Document 1).

Recently, in order to improve the performance of LSIs, the use of copper alloys as wiring materials has been attempted.
However, it is difficult to finely process the copper alloy by the dry etching method frequently used in the formation of the conventional aluminum alloy wiring. Therefore, a so-called damascene method is mainly employed in which a copper alloy thin film is deposited and embedded on an insulating film in which grooves have been formed in advance, and the copper alloy thin film other than the grooves is removed by CMP to form embedded wiring. (For example, refer to Patent Document 2).

For example, tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds are formed as a barrier layer to prevent copper diffusion into the interlayer insulating film in the lower layer of the wiring such as copper or copper alloy.
Therefore, it is necessary to remove the exposed barrier layer by CMP except for the wiring portion in which copper or a copper alloy is embedded.

  However, since these barrier layer conductor films have higher hardness than copper or copper alloy, a combination of polishing materials for copper or copper alloy cannot often provide a sufficient CMP rate. If the barrier layer is also continuously polished with such a polishing liquid, dishing of the copper or copper alloy portion occurs. Therefore, a two-step polishing method comprising a first step of polishing copper or a copper alloy and a second step of polishing the barrier layer conductor has been studied.

  A general method of metal CMP is to apply a polishing pad on a circular polishing platen (platen), immerse the polishing pad surface with a metal polishing liquid, and press the surface on which the metal film of the substrate is formed. The polishing platen is rotated in a state where a predetermined pressure (polishing pressure or polishing load) is applied from the back surface, and the metal film on the convex portion is removed by mechanical friction between the polishing liquid and the convex portion of the metal film.

  The metal polishing liquid used for CMP of Cu or Cu alloy is generally composed of an oxidizing agent and solid abrasive grains, and a metal oxide dissolving agent and a protective film forming agent are further added as necessary. First, it is considered that the basic mechanism is to oxidize the surface of a metal film with an oxidizing agent and scrape the oxidized layer with solid abrasive grains.

  Since the oxide layer on the metal surface of the recess does not touch the polishing pad so much and the effect of scraping off by the solid abrasive grains does not reach, the metal layer of the projection is removed with the progress of CMP and the substrate surface is flattened (for example, (Refer nonpatent literature 1.).

  As a method for increasing the polishing rate by CMP, it is effective to add a metal oxide solubilizer. It is interpreted that if the metal oxide particles scraped off by the solid abrasive grains are dissolved in the polishing liquid (hereinafter referred to as etching), the effect of scraping off by the abrasive grains is increased.

  Although the polishing rate by CMP is improved by adding a metal oxide solubilizer, on the other hand, when the oxide layer on the metal film surface in the recess is also etched to expose the metal film surface, the metal film surface is further oxidized by the oxidant, and this is repeated. As a result, the etching of the metal film in the recesses proceeds. For this reason, a phenomenon occurs in which the central portion of the surface of the metal wiring embedded after polishing is depressed like a dish (hereinafter referred to as dishing), and the planarization effect is impaired.

  In order to prevent this, a protective film forming agent is further added. The protective film forming agent forms a protective film on the surface of the metal film and prevents dissolution of the oxide layer in the polishing liquid. This protective film can be easily scraped off by abrasive grains, and it is desirable not to decrease the polishing rate by CMP.

  In order to suppress corrosion during dishing or polishing of copper or copper alloy, and to form a highly reliable LSI wiring, it contains BTA as a protective film forming agent and a metal oxide dissolving agent composed of aminoacetic acid or amide sulfuric acid such as glycine A method using a CMP polishing liquid is proposed (for example, see Patent Document 3).

  In metal embedding formation such as copper or copper alloy damascene wiring formation, plug wiring formation such as tungsten, etc., if the polishing rate of the silicon dioxide film which is an interlayer insulating film formed other than the embedded portion is high, the interlayer insulating film Erosion that reduces the thickness of each wiring occurs. As a result, resistance variation occurs due to an increase in wiring resistance, pattern density, and the like, so that a characteristic in which the polishing rate of the silicon dioxide film is sufficiently small with respect to the metal film to be polished is required.

  On the other hand, the wiring delay accompanying the miniaturization of wiring has been a problem in increasing the performance of LSI. In order to solve this problem, it is indispensable to reduce the resistance between the wirings, and the replacement of the interlayer insulating material with a low dielectric constant (Low-k) material is progressing.

On the other hand, a technique in which a small amount of an organic solvent is generally added as a solubilizing agent for a polishing liquid of a protective film forming agent having low solubility in water (see, for example, Patent Document 4). However, in these techniques, the purpose is to obtain a highly concentrated polishing liquid, and the organic solvent has a protective film forming agent solubility of, for example, 25 g / g so that the protective film forming agent does not precipitate even when concentrated. L or more. Moreover, only a small amount of an organic solvent capable of dissolving the protective film forming agent added in a small amount was added.
U.S. Pat. No. 4,944,836 Japanese Patent Laid-Open No. 02-278822 Journal of Electrochemical Society, Vol.138, No.11 (1991), 3460-3464 Japanese Patent Laid-Open No. 08-83780 JP 2004-146840 A

  Generally, the lower the relative dielectric constant (k value) of the insulating film, the lower the mechanical strength and the adhesion between different materials, and the peeling between the insulating film and different layers due to the friction applied to the wafer during the CMP process. The occurrence of chipping, fragmentation, cracking, etc. has led to a decrease in yield.

In order to reduce such peeling and the like, reduction of the polishing load has been demanded.
However, when the polishing load is lowered, there is a problem that the polishing rate is lowered and the throughput is lowered. For example, in the above first step of polishing copper or copper alloy, if the polishing load is lowered to reduce the frictional force that causes peeling of the low dielectric constant insulating film or internal destruction of the layer, the polishing rate is lowered. Not desirable.

Based on the idea that by reducing the dissociation rate of an anionic polymer compound, the present inventors can reduce friction and polish a polishing object including a low dielectric constant material layer without reducing the polishing rate. As a result of intensive studies, it has been found that the above problem can be solved by containing a predetermined amount of a solvent having a dielectric constant lower than that of water.
In view of the above problems, the present invention reduces the polishing friction force by focusing on the dielectric constant of the polishing liquid, and enables polishing of a polishing target including a low dielectric constant material layer without reducing the polishing load and the polishing rate. A metal polishing liquid and a polishing method using the same are provided.

The present invention is (1) a metal polishing slurry comprising water, an oxidant, a metal oxide solubilizer, a protective film forming agent and a solvent having a dielectric constant lower than that of water, wherein the solvent having a dielectric constant lower than that of water is used for a metal. The present invention relates to a polishing slurry for metals contained in 3 to 30% by mass in the polishing fluid.
The present invention also relates to (2) the metal polishing liquid according to (1) above, wherein the pH of the metal polishing liquid is 2 or more and 4 or less.
Further, the present invention provides the metal according to (1) or (2), wherein (3) the protective film forming agent uses at least one of a nitrogen-containing compound and an anionic polymer compound having a weight average molecular weight of 500 or more. The present invention relates to a polishing liquid.
The present invention also relates to (4) an anionic polymer compound in which the anionic group of the anionic polymer compound is at least one of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a phenolic hydroxyl group, and a salt thereof. The present invention relates to the metal polishing slurry (3) containing at least one selected from the above.

In the present invention, (5) any one of (1) to (4), wherein the solvent is at least one selected from alcohol, glycol, ether, lactone, carbonate, ester, ketone, amide, and aldehyde. This relates to a metal polishing slurry.
In addition, the present invention provides (6) any one of the above (1) to (5), wherein the metal oxide solubilizer is at least one acid selected from inorganic acids, organic acids, aminoacetic acid, amidosulfuric acid or a salt thereof. This relates to a metal polishing slurry.
Moreover, this invention is (7) Said (1)-(6) whose oxidizing agent is at least 1 sort (s) chosen from hydrogen peroxide, ammonium persulfate, nitric acid, potassium periodate, hypochlorous acid, and ozone water. This relates to a polishing slurry for metal.
The present invention also relates to (8) the metal polishing slurry according to any one of (1) to (7), further comprising abrasive particles.
The present invention also relates to (9) the metal polishing slurry according to (8), wherein the abrasive particles are at least one selected from silica, alumina, ceria, titania, zirconia, and germania.

The present invention also relates to (10) the metal polishing slurry according to any one of (1) to (9), wherein the metal to be polished is a conductive substance or a barrier conductor layer.
The present invention also relates to (11) the metal polishing slurry according to (10) above, wherein the polishing rate ratio between the conductive material and the barrier conductor layer is 20 or more: 1.

  The present invention also includes (12) an interlayer insulating film having a concave portion and a convex surface, a barrier conductor layer that covers the interlayer insulating film along the surface, and a conductive material layer that fills the concave portion and covers the barrier conductor layer. A first polishing step of polishing a conductive material layer of the substrate having the convex portion to expose the barrier conductor layer of the convex portion, and polishing at least the barrier conductive layer and the conductive material layer of the concave portion to form an interlayer between the convex portions The polishing liquid for metal according to any one of (1) to (11), which is used in at least the first polishing step among the polishing steps including the second polishing step for exposing the insulating film.

Moreover, this invention is used in the polishing step (13), wherein the conductive material to be polished contains at least one selected from the group consisting of copper, copper alloys, copper oxides, and copper alloy oxides. It is related with the metal polishing liquid in any one of 10)-(12).
In the present invention, (14) the barrier conductor layer is a barrier layer for preventing the conductive material from diffusing into the interlayer insulating film, and includes tantalum, tantalum nitride, tantalum alloy, other tantalum compounds, titanium, and titanium nitride. , Titanium alloy, other titanium compound, tungsten, tungsten nitride, tungsten alloy, metal polishing slurry according to any one of (10) to (13) used in a polishing step containing at least one selected from the group consisting of other tungsten compounds About.
The present invention also relates to (15) the metal polishing slurry according to any one of (12) to (14), wherein the interlayer insulating film is a silicon-based film or an organic polymer film.

Furthermore, the present invention provides (16) any one of the above (1) to (15) between the surface to be polished and the polishing cloth in a state where the substrate having the surface to be polished is pressed onto the polishing cloth of the polishing surface plate. The present invention relates to a polishing method characterized by polishing a surface to be polished by relatively moving a polishing cloth and a substrate while supplying a metal polishing liquid.
The present invention also relates to (17) the polishing method according to (16), wherein the metal to be polished is a conductive substance or a barrier conductor layer.

The present invention also includes (18) an interlayer insulating film having a concave portion and a convex surface, a barrier conductor layer covering the interlayer insulating film along the surface, and a conductive material layer filling the concave portion and covering the barrier conductive layer. A first polishing step of polishing a conductive material layer of the substrate having the convex portion to expose the barrier conductor layer of the convex portion, and polishing at least the barrier conductive layer and the conductive material layer of the concave portion to form an interlayer between the convex portions The present invention relates to a polishing method using the metal polishing liquid according to any one of the above (1) to (15) in at least a first polishing step among polishing steps including a second polishing step for exposing an insulating film.
The present invention also relates to (19) the polishing method according to the above (17) or (18), wherein the polishing rate ratio between the conductive material and the barrier conductor layer is 20 or more: 1.
In the present invention, (20) the electroconductive substance to be polished contains at least one selected from the group consisting of copper, copper alloys, copper oxides, and copper alloy oxides. ).
In the present invention, (21) the barrier conductor layer is a barrier layer for preventing the conductive material from diffusing into the interlayer insulating film, and includes tantalum, tantalum nitride, tantalum alloy, other tantalum compounds, titanium, and titanium nitride. , A titanium alloy, another titanium compound, tungsten, tungsten nitride, a tungsten alloy, or the other tungsten compound. The polishing method according to any one of (18) to (20), including at least one selected from other tungsten compounds.
The present invention also relates to (22) the polishing method according to any one of (18) to (21), wherein the interlayer insulating film is a silicon-based film or an organic polymer film.

  ADVANTAGE OF THE INVENTION According to this invention, the grinding | polishing liquid for metal which polishes the grinding | polishing object containing a low dielectric constant material layer by reducing polishing frictional force, without reducing a polishing rate, and the grinding | polishing method using the same can be provided. .

  Hereinafter, the best mode for carrying out the invention will be described in detail.

  The metal polishing liquid according to the present invention is characterized by water, an oxidizing agent, a metal oxide solubilizer, a protective film forming agent selected from at least one of a nitrogen-containing compound and an anionic polymer compound, and a solvent having a lower dielectric constant than water. It is a metal polishing liquid containing this, Comprising: 3-30 mass% of said solvents are contained in the metal polishing liquid. Here, the solvent refers to a liquid that can dissolve substances contained in the polishing liquid and does not react with these substances and can be mixed with water.

  The pH of the metal polishing liquid according to the present invention is preferably 2 or more and 4 or less in that the polishing rate by CMP is large and the etching rate can be effectively suppressed. If the pH is less than 2, the etching rate is high, and it is difficult to suppress etching with the protective film forming agent. On the other hand, if the pH exceeds 4, the polishing rate by CMP is slow and it is difficult to become a practical polishing liquid. The range of pH 2 or more and 3.8 or less is more preferable, and 2.5 to 3.5 is particularly preferable.

The pH can be adjusted by the amount of acid added.
It can also be adjusted by adding alkali components such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH). These can also be used as metal oxide solubilizers.

  The pH of the polishing liquid of the present invention was measured with a pH meter (for example, model number PHL-40 manufactured by Electrochemical Instruments). Two-point calibration was performed using a standard buffer solution (phthalate pH buffer solution pH: 4.01 (25 ° C.), neutral phosphate pH buffer solution pH 6.86 (25 ° C.)), and then the electrode was polished. The value after being stabilized after 2 minutes or more was measured.

  The protective film forming agent used in the present invention is preferably at least one of an anionic polymer compound and a nitrogen-containing compound.

  Examples of the nitrogen-containing compound include a compound having an imidazole skeleton, a compound having a triazole skeleton, a compound having a pyrimidine skeleton, a compound having a guanidine skeleton, a compound having a thiazole skeleton, and a compound having a pyrazole skeleton. A heterocyclic compound is more preferable, and a compound selected from the following group is desirable. That is, benzimidazol-2-thiol, triazinedithiol, triazinetrithiol, 2- [2- (benzothiazolyl)] thiopropionic acid, 2- [2- (benzothiazolyl)] thiobutyric acid, 2-mercaptobenzothiazole, 1 , 2,3-triazole, 1,2,4-triazole, 3-amino-1H-1,2,4-triazole, benzotriazole, 1-hydroxybenzotriazole, 1-dihydroxypropylbenzotriazole, 2,3-di Carboxypropylbenzotriazole, 4-hydroxybenzotriazole, 4-carboxyl-1H-benzotriazole, 4-carboxyl-1H-benzotriazole methyl ester, 4-carboxyl-1H-benzotriazole butyl ester, 4-carbo Sil-1H-benzotriazole octyl ester, 5-hexylbenzotriazole, [1,2,3-benzotriazolyl-1-methyl] [1,2,4-triazolyl-1-methyl] [2-ethylhexyl] amine Azoles such as tolyltriazole, naphthotriazole, and bis [(1-benzotriazolyl) methyl] phosphonic acid. The combined use of the anionic polymer compound and the nitrogen-containing cyclic compound is suitable for both suppression of the etching rate and high polishing rate.

  The anionic polymer compound used in the present invention is preferably selected from water-soluble polymers having an anionic functional group and salts thereof. The anionic group is preferably at least one of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a phenolic hydroxyl group, more preferably a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group. Particularly preferred is an acid group. These can be used even if the anionic functional group is contained alone or in combination of two or more in the water-soluble polymer.

  Moreover, even if the water-soluble polymer in which anionic functional groups differ is contained individually by 1 type or 2 types or more, it can be used. Water-soluble polymers that satisfy these requirements are polystyrene sulfonic acid, polyacrylamide methylpropane sulfonic acid, polymalic acid, polycarboxylic acid, polyacrylic acid, polymethacrylic acid, polyitaconic acid, polymaleic acid, polyfumaric acid, polyaspartic acid, polyglutamic acid. , Polylysine, polyphosphoric acid, metaphosphoric acid and salts thereof. However, when the substrate to be applied is a silicon substrate for a semiconductor integrated circuit or the like, contamination with an alkali metal, an alkaline earth metal, a halide, or the like is not desirable, so an acid or an ammonium salt thereof is desirable.

  In the present invention, the amount of the anionic polymer compound added is 0.01 to 3.0% by mass with respect to the total amount of the metal oxidizing agent, the metal oxide solubilizer, the protective film forming agent for the metal surface, and water. Preferably it is 0.1 mass%-2.0 mass%. If this addition amount is less than 0.01% by mass, the combined effect with the protective film forming agent does not appear in etching suppression, and if it exceeds 3% by mass, the polishing rate by CMP decreases.

  In the present invention, the weight average molecular weight of the anionic polymer compound contained in the polishing liquid is preferably 500 or more. More preferably, it is 5,000 or more and 500,000 or less, and particularly preferably 50,000 to 300,000. The weight average molecular weight can be measured by gel permeation chromatography using a standard polystyrene calibration curve. If the molecular weight is too low, the effect of the protective film forming agent is reduced and the polishing rate becomes too high, and an appropriate polishing rate cannot be obtained. On the other hand, if the molecular weight is too high, the effect of the water-soluble polymer compound is not preferable. And the polishing rate becomes too small, which is not preferable.

According to the present invention, the dielectric constant of the polishing liquid is decreased by using the components of the polishing liquid as water, an oxidizing agent, a metal oxide solubilizer, a protective film forming agent for the metal surface, and a solvent having a lower dielectric constant than water. The dissociation rate of the anionic group of the anionic polymer compound in the polishing liquid can be reduced.
As a result, the reaction layer formed on the copper surface becomes brittle, and it is presumed that the friction applied during wafer polishing can be kept low while maintaining an appropriate polishing rate.

  In the present invention, the solvent having a lower dielectric constant than the dielectric constant of water contained in the polishing liquid (78.3 at 25 ° C.) is not particularly limited, but a solvent that can be mixed with water is preferable.

For example, alcohols such as methanol, ethanol, propanol, n-butanol, n-pentanol, n-hexanol, isopropyl alcohol, phenol,
Glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 3-methyl-3-methoxybutanol,
Ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, tripropylene glycol monomethyl ether and ethylene glycol monoethyl ether, propylene glycol monoethyl ether, diethylene glycol monoethyl ether, di Propylene glycol monoethyl ether, triethylene glycol monoethyl ether, tripropylene glycol monoethyl ether, ethylene glycol monopropyl ether, propylene glycol monopropyl ether, diethylene glycol monopropyl ether, dipropylene glycol monopropyl ether, trie Lenglycol monopropyl ether, tripropylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, triethylene glycol monobutyl ether, tripropylene glycol monobutyl ether, ethylene glycol dimethyl ether, propylene Glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, triethylene glycol dimethyl ether, tripropylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol diethyl ether, diethylene glycol diethyl Ether, dipropylene glycol diethyl ether, triethylene glycol diethyl ether, tripropylene glycol diethyl ether, ethylene glycol dipropyl ether, propylene glycol dipropyl ether, diethylene glycol dipropyl ether, dipropylene glycol dipropyl ether, triethylene glycol dipropyl ether , Tripropylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dibutyl ether, diethylene glycol dibutyl ether, dipropylene glycol dibutyl ether, triethylene glycol dibutyl ether, tripropylene glycol dibutyl ether, tetrahydrofuran, dimethoxyethane, polyethylene oxa Id, ethylene glycol monomethyl acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, ethers such as 1,2-dioxane, 1,3-dioxane, 1,4-dioxane,
Lactones such as butyrolactone and propyrolactone,
Carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate,
Esters such as ethyl acetate and ethyl lactate,
Ketones such as acetone and methyl ethyl ketone;
Amides such as dimethylformamide and acetamide,
Aldehydes such as formaldehyde and acetaldehyde,
Other examples include n-methylpyrrolidone and sulfolane.

  Among these, at least one selected from alcohol, glycol, ether, lactone, carbonate, ester, ketone, amide, and aldehyde is preferable. Among them, alcohols, glycols, ethers and carbonates are preferable.

  As the dielectric constant, literature values (for example, can be cited from “Chemical Handbook” edited by the Chemical Society of Japan) can be used, but Agilent Technologies, Inc. manufactured by Agilent Technologies, using model number 16452A liquid electrode. It can be measured with a model number E4980A LCR meter (measurement voltage AC1V, measurement frequency 100 kHz).

  The dielectric constant of the solvent should be lower than that of water (78.3 at 25 ° C.), but the dielectric constant at 25 ° C. is preferably 60 or less, more preferably 40 or less, and 30 It is particularly preferred that

  The solvent having a dielectric constant lower than that of water is contained in the metal polishing liquid in an amount of 3 to 30% by mass, preferably from 5 to 30% by mass from the viewpoint of suppressing dissociation of the polymer in the polishing liquid and reducing friction during polishing. More preferably, it is 10-30 mass%, Most preferably, it is 15-30 mass%. From the viewpoint of maintaining a practical polishing rate, the solvent content is preferably 30% by mass or less.

  The dissociation rate of the anionic polymer compound in the polishing liquid is preferably 95% or less, more preferably 90% or less, and more preferably 85% or less in terms of more efficiently reducing the frictional force. Particularly preferred is 80% or less.

  The metal oxide solubilizer used in the metal polishing liquid according to the present invention is preferably water-soluble, malonic acid, citric acid, malic acid, glycolic acid, glutamic acid, glyconic acid, oxalic acid, tartaric acid, picolinic acid, nicotinic acid, Mandelic acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, hydrochloric acid, formic acid, lactic acid, phthalic acid, fumaric acid, maleic acid and aminoacetic acid, amidosulfuric acid and their salts are selected from copper, copper alloys and copper or copper alloy oxides Further, it is suitable for a laminated film including at least one metal layer. These are preferable in that a balance with the protective film forming agent is easily obtained. In particular, malic acid, tartaric acid, citric acid, phosphoric acid, and sulfuric acid are preferable in that the etching rate can be effectively suppressed while maintaining a practical CMP rate.

Alkali components such as ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide (TMAH) can also be used. These can be used alone or in combination of two or more.
These metal oxide solubilizers can also be used as pH adjusters.

In the present invention, examples of the metal oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), nitric acid, potassium periodate, ammonium persulfate, hypochlorous acid, ozone water, etc. Among them, hydrogen peroxide is particularly preferable. preferable. These can be used alone or in combination of two or more. When the substrate is a silicon substrate including an integrated circuit element, contamination with an alkali metal, an alkaline earth metal, or the like is not desirable. Therefore, an oxidizing agent that does not include a nonvolatile component is desirable. However, hydrogen peroxide is most suitable because ozone water has a severe compositional change over time.

In the present invention, solid abrasive grains can be added to the polishing liquid. The type of solid abrasive is preferably colloidal silica or colloidal alumina.
The addition amount of the solid abrasive is preferably 0.001% by mass to 10% by mass and more preferably 0.001% by mass to 1.0% by mass with respect to the total weight of the polishing liquid. If this addition amount is less than 0.001% by mass, the physical scraping action is small, so the polishing rate by CMP is small. If it exceeds 10% by mass, the polishing rate by CMP is saturated, and even if it is added more than that, no increase is observed. .

  The primary particle size of the abrasive particles is preferably 200 nm or less, more preferably 5 to 200 nm, particularly preferably 5 to 150 nm, and most preferably 5 to 100 nm. When the primary particle diameter exceeds 200 nm, the flatness tends to deteriorate.

  When the abrasive particles are associated, the secondary particle diameter is preferably 200 nm or less, more preferably 10 to 200 nm, particularly preferably 10 to 150 nm, and 10 to 100 nm. Is very preferred. When the secondary particle diameter exceeds 200 nm, the flatness tends to deteriorate. Also, when selecting a secondary particle size of less than 10 nm, care must be taken because the mechanical reaction layer removal capability of the abrasive particles is insufficient and the CMP rate may be reduced.

In the present invention, the primary particle size of the abrasive particles can be measured using a transmission electron microscope (for example, S4700 manufactured by Hitachi, Ltd.).
The secondary particles can be measured using a light diffraction / scattering particle size distribution analyzer (for example, COULTER N4SD manufactured by COULTER Electronics).

  The polishing method of the present invention includes a polishing platen in a state where a substrate having a film to be polished is pressed against the polishing cloth while supplying the metal polishing liquid between the surface to be polished and the polishing cloth of the polishing platen. This is a polishing method for polishing a film to be polished by relatively moving a substrate.

As a polishing apparatus, for example, a general polishing apparatus having a surface plate on which a motor capable of changing the number of rotations can be attached and a polishing cloth (pad) can be attached and a holder for holding a substrate is used. it can. Although there is no restriction | limiting in particular as abrasive cloth, A general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. can be used. The polishing conditions are not particularly limited, but it is preferable to set the rotation speed of the surface plate to a low rotation of 200 min ⁻¹ or less so that the substrate does not jump out.

  The polishing pressure of the substrate having the film to be polished onto the polishing cloth is preferably 4 to 100 kPa, and more preferably 6 to 50 kPa from the viewpoint of the uniformity of the polishing rate in the wafer surface and the flatness of the pattern. During polishing, it is preferable to continuously supply the metal polishing liquid to the polishing cloth with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of polishing cloth is always covered with polishing liquid. The substrate after polishing is preferably washed in running water and then dried after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like.

  Conductive material of a substrate having an interlayer insulating film having a concave portion and a convex surface, a barrier conductor layer covering the interlayer insulating film along the surface, and a conductive material layer filling the concave portion and covering the barrier conductive layer A first polishing step for polishing the layer to expose the barrier conductor layer of the convex portion, and a second polishing for polishing at least the barrier conductor layer and the conductive material layer of the concave portion to expose the interlayer insulating film of the convex portion Among the polishing steps including the steps, it is preferable that the metal polishing slurry of the present invention is used at least in the first polishing step.

  The metal to be polished, which is an object to be polished by the metal polishing liquid, is preferably a conductive substance or a barrier conductor layer. At this time, the polishing rate ratio between the conductive substance and the barrier conductor layer is preferably 20 or more and 1 and more preferably 50 or more and 1.

  The conductive material to be polished is preferably at least one selected from the group consisting of copper, copper alloys, copper oxides, and copper alloy oxides. The barrier conductor layer is a barrier layer that prevents the conductive material from diffusing into the interlayer insulating film, and includes tantalum, tantalum nitride, tantalum alloy, other tantalum compounds, titanium, titanium nitride, titanium alloy, and other titanium. Examples thereof include at least one selected from a compound, tungsten, tungsten nitride, a tungsten alloy, and other tungsten compounds.

The interlayer insulating film is an insulating film that reduces the parasitic capacitance between elements and wirings as compared with conventional SiO ₂ , and is an inorganic film such as SiOF, Si—H containing SiO ₂ , carbon containing SiO ₂ (SiOC), methyl Examples include at least one selected from organic-inorganic hybrid films such as group-containing SiO ₂ or organic polymer films such as fluororesin-based polymers, polyimide-based polymers, polyallyl ether-based polymers, and parelin-based polymers. On the other hand, these insulating films are inferior in mechanical strength to conventional SiO ₂ . By making these porous, the dielectric constant of the insulating film can be further reduced. However, since it is known that the mechanical strength further decreases with this, it is preferable to select appropriately (for example, see IEDM Tech. Digest, (1999), pages 619 to 622).

Hereinafter, the present invention will be described by way of examples. The present invention is not limited to these examples.
(Metal polishing liquid preparation method)
The metal polishing liquids used in Examples 1 to 9, 12 and Comparative Examples 1 and 3 were benzotriazole 0.6% by mass as a nitrogen-containing cyclic compound in the protective film forming agent, polycarboxylic acid, based on the weight of the polishing liquid. As a oxidant, 0.3% by mass of polyacrylic acid, 30% by mass of hydrogen peroxide (special grade, 30% aqueous solution) as an oxidant, 0.3% by mass of a metal oxide solubilizer shown in Table 1, a solvent shown in Table 1 Was prepared by containing 0 to 32 mass% of pure water in the balance. The pH of the polishing liquid was adjusted by the amount of ammonia added.

Using these metal polishing liquids, the substrate to be polished was polished under the following polishing conditions.
Moreover, these metal polishing liquids were impregnated with metal pieces to be polished, and the reaction layer formed on the metal surface was subjected to FT-IR measurement to evaluate the degree of dissociation of anionic groups of the anionic polymer compound.

The metal polishing liquid used in Examples 10 to 11 and Comparative Example 2 was 0.3 mass% of benzotriazole as a nitrogen-containing cyclic compound and 0% of polyacrylic acid as a polycarboxylic acid, based on the weight of the polishing liquid. 4% by mass, 0.8% by mass of colloidal silica abrasive grains having a median diameter of 60 nm, and 0.3% by mass of malic acid and ammonia as metal oxide solubilizers, hydrogen peroxide (special grade, 30% aqueous solution) 20 The solvent shown in Table 1 was prepared containing 0 to 20% by mass of the solvent shown in Table 1 and the remaining pure water. The pH of the polishing liquid was adjusted with the amount of ammonia added.
Using these metal polishing liquids, the substrate to be polished was polished under the following polishing conditions.

表中、イソプレングリコール及び３−メチル−３−メトキシグリコール以外の添加溶媒の誘電率は文献値を使用し、イソプレングリコール及び３−メチル−３−メトキシグリコールの誘電率は以下の測定条件にて測定を行った。
測定器 ：アジレントテクノロジー社製 Ｅ４９８０Ａ ＬＣＲメータ
電 極 ：アジレントテクノロジー社製 １６４５２Ａ 液体用フィクスチャー
測定電圧 ：ＡＣ １Ｖ
測定周波数：１００ｋＨｚ

In the table, literature values are used for the dielectric constants of added solvents other than isoprene glycol and 3-methyl-3-methoxyglycol, and the dielectric constants of isoprene glycol and 3-methyl-3-methoxyglycol are measured under the following measurement conditions. Went.
Measuring instrument: E4980A LCR meter manufactured by Agilent Technologies
Electrode: 1645A liquid fixture manufactured by Agilent Technologies
Measurement voltage: AC 1V
Measurement frequency: 100 kHz

(Liquid property evaluation)
Measurement temperature: 25 ± 5 ° C
pH: Measured with Model No. PHL-40 manufactured by Electrochemical Instruments.
(CMP polishing conditions)
Polishing device: Mirra (Applied Materials)
Polishing fluid flow rate: 200 mL / min Substrate: Silicon substrate polishing pad with a 1 μm-thick copper film: Foam polyurethane resin with closed cells (model number IC1000 manufactured by Rodel)
Polishing pressure: 13.7 kPa
Relative speed between substrate and polishing surface plate: 80 m / min

(Cleaning after CMP)
After the CMP treatment, the substrate was washed with a PVA brush and ultrasonic water and then dried with a spin dryer.
(Abrasive product evaluation items)
CMP rate: The film thickness difference of each film before and after CMP was calculated from the electrical resistance value.
Grinding friction force: The motor operating current value for driving the Mirra polishing platen is output as an analog signal (voltage (V)) and read with a model number NR-250 manufactured by Keyence Corporation. Compared.

  The presence or absence of polishing scratches was confirmed by visual inspection of the substrate after CMP, optical microscope observation, and electron microscope observation. As a result, no significant polishing scratches were observed in all examples and comparative examples.

(Evaluation of the degree of carboxylic acid dissociation of polycarboxylic acid)
Measurement temperature: 25 ± 5 ° C
Measurement method: 50 mL of the above metal polishing liquid was impregnated with a metal piece (2 × 5 cm) to be polished for 30 seconds, rinsed with water for 5 seconds, and then subjected to FT-IR of the metal surface reaction layer using model number FTS135 manufactured by Bio-Rad. It was measured. And the peak area of dissociated carboxyl groups having a peak at 1600 cm ^-1, dissociation evaluation of carboxylic acids by comparing the peak area of undissociated carboxyl groups with a peak at 1700 cm ^-1 was performed.

  Table 2 shows the Cu polishing rate in Examples 1 to 12 and Comparative Examples 1 to 3, the evaluation results of the frictional force during polishing, and the degree of carboxylic acid dissociation of the polycarboxylic acid.

Hereinafter, the results shown in Table 2 will be described in detail.
In Example 1, the same metal oxide solubilizer as in Comparative Example 1 was added, but 8% by mass of isopropyl alcohol was further added. The metal oxide solubilizer is mainly phosphoric acid. Example 1 shows almost the same carboxylic acid dissociation rate as Comparative Example 1, but the frictional force during polishing is slightly reduced to 0.50. On the other hand, the Cu polishing rate is 250 nm / min, which is not significantly different from Comparative Example 1.

  In Example 2, the same metal oxide solubilizer as in Comparative Example 1 was added, but 16% by mass of isopropyl alcohol was further added. The metal oxide solubilizer is mainly phosphoric acid. In Example 2, the dissociation rate of the carboxylic acid was 90%, unlike Comparative Example 1, and the dissociation of the anion group was suppressed, and the frictional force during polishing was also reduced to 0.45. On the other hand, the Cu polishing rate is 300 nm / min and has a polishing rate equivalent to that of Comparative Example 1.

  In Example 3, the same metal oxide solubilizer as in Comparative Example 1 was added, but 24 mass% of isopropyl alcohol was further added. The metal oxide solubilizer is mainly phosphoric acid. In Example 3, the dissociation rate of the carboxylic acid is 60%, and the dissociation of the anion group is suppressed from that of Example 2, and the frictional force during polishing is also reduced to 0.43. On the other hand, the Cu polishing rate is 320 nm / min and has a polishing rate equivalent to that of Comparative Example 1.

  In Example 4, the same metal oxide solubilizer as in Comparative Example 1 was added, but 32% by mass of isopropyl alcohol was further added. The metal oxide solubilizer is mainly phosphoric acid. In Example 4, the frictional force at the time of polishing was 40% of the carboxylic acid dissociation rate compared to Comparative Example 1, and the dissociation of the anionic group was suppressed from that of Example 3, and the frictional force at the time of polishing was also reduced to 0.41. . On the other hand, the Cu polishing rate is 360 nm / min, which is equivalent to that of Comparative Example 1.

  In Example 5, the same metal oxide solubilizer as in Comparative Example 1 was added, but 20% by mass of methanol was further added. The metal oxide solubilizer is mainly phosphoric acid. Example 5 shows that the frictional force during polishing is 0.46, which is lower than that of Comparative Example 1, while the polishing rate is 280 nm / min, which is equivalent to that of Comparative Example 1.

  In Example 6, the same metal oxide solubilizer as in Comparative Example 1 was added, but 20% by mass of ethanol was further added. The metal oxide solubilizer is mainly phosphoric acid. Example 6 shows that the frictional force during polishing is 0.42, which is lower than that of Comparative Example 1, while the polishing rate is 290 nm / min, indicating a Cu polishing rate equivalent to that of Comparative Example 1.

  In Example 7, the same metal oxide solubilizer as in Comparative Example 1 was added, but 20% by mass of isoprene glycol was further added. The metal oxide solubilizer is mainly phosphoric acid. Example 7 shows that the frictional force during polishing is 0.38, which is lower than that of Comparative Example 1, while the polishing rate is 250 nm / min, indicating a Cu polishing rate equivalent to that of Comparative Example 1.

In Example 8, the same metal oxide solubilizer as in Comparative Example 1 was added, but 20% by mass of 3-methyl 3-methoxyglycol was further added. The metal oxide solubilizer is mainly phosphoric acid. Example 8 shows that the frictional force during polishing is 0.37, which is lower than that of Comparative Example 1, while the polishing rate is 290 nm / min, indicating a Cu polishing rate equivalent to that of Comparative Example 1.
In Example 9, the same metal oxide solubilizer as in Comparative Example 1 was added, but 20 mass% of 1,4-dioxane was further added. The metal oxide solubilizer is mainly phosphoric acid. Example 9 shows that the frictional force during polishing is 0.36, which is lower than that of Comparative Example 1, while the polishing rate is 271 nm / min, indicating a Cu polishing rate equivalent to Comparative Example 1.

  In Example 10, the same metal oxide solubilizer as in Comparative Example 2 was added, but 10% by mass of isopropyl alcohol was further added. The metal oxide solubilizer is mainly malic acid. Example 10 shows that the frictional force during polishing is 0.56, which is slightly lower than that of Comparative Example 2, while the polishing rate shows the same result.

  In Example 11, the same metal oxide solubilizer as in Comparative Example 2 was added, but 20% by mass of isopropyl alcohol was further added. The metal oxide solubilizer is mainly malic acid. In Example 11, the frictional force during polishing was 0.56, which was slightly lower than that of Comparative Example 2, while the polishing rate was slightly lower.

  In Example 12, the same metal oxide solubilizer as in Comparative Example 3 was added, but 20% by mass of isopropyl alcohol was further added. The metal oxide solubilizer is mainly sulfuric acid. In Example 12, the frictional force at the time of polishing was 0.44, which was slightly lower than that of Comparative Example 3, while the polishing rate was 310 nm / min, which was the same as that of Comparative Example 3.

  FIG. 1 shows polishing liquids for metals of Examples 1 to 4 and Comparative Example 1 (the metal oxide dissolving agent is mainly phosphoric acid, the oxidizing agent is hydrogen peroxide, the protective film forming agent is benzotriazole, an anionic polymer) The graph which plotted the relationship of the isopropyl alcohol addition rate and the carboxylic acid dissociation rate of polycarboxylic acid of the metal polishing liquid whose compound is polycarboxylic acid is shown.

It is the graph which plotted the relationship between the isopropyl alcohol addition rate in Examples 1-4 of this invention, and the carboxylic acid dissociation rate of polycarboxylic acid in the comparative example 1. FIG.

Claims (22)

  A metal polishing liquid comprising water, an oxidizing agent, a metal oxide solubilizer, a protective film forming agent, and a solvent having a lower dielectric constant than water, wherein the solvent having a lower dielectric constant than water is 3 to 30 in the metal polishing liquid. Polishing liquid for metals contained by mass%.   The metal polishing liquid according to claim 1, wherein the pH of the metal polishing liquid is 2 or more and 4 or less.   The metal polishing slurry according to claim 1 or 2, wherein the protective film forming agent uses at least one of a nitrogen-containing compound and an anionic polymer compound having a weight average molecular weight of 500 or more.   Claim wherein the anionic group of the anionic polymer compound contains at least one selected from an anionic polymer compound and a salt thereof which is at least one of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group and a phenolic hydroxyl group. Item 4. The metal polishing slurry according to Item 3.   The metal polishing slurry according to any one of claims 1 to 4, wherein the solvent is at least one selected from alcohol, glycol, ether, lactone, carbonate, ester, ketone, amide, and aldehyde.   The metal polishing slurry according to any one of claims 1 to 5, wherein the metal oxide solubilizer is at least one acid selected from inorganic acids, organic acids, aminoacetic acid, and amidosulfuric acid or a salt thereof.   The metal polishing slurry according to any one of claims 1 to 6, wherein the oxidizing agent is at least one selected from hydrogen peroxide, ammonium persulfate, nitric acid, potassium periodate, hypochlorous acid, and ozone water.   The metal polishing slurry according to any one of claims 1 to 7, further comprising abrasive particles.   The metal polishing slurry according to claim 8, wherein the abrasive particles are at least one selected from silica, alumina, ceria, titania, zirconia, and germania.   The metal polishing liquid according to any one of claims 1 to 9, wherein the metal to be polished is a conductive substance or a barrier conductor layer.   The metal polishing slurry according to claim 10, wherein the polishing rate ratio between the conductive material and the barrier conductor layer is 20 or more: 1.   Conductive material of a substrate having an interlayer insulating film having a concave portion and a convex surface, a barrier conductor layer covering the interlayer insulating film along the surface, and a conductive material layer filling the concave portion and covering the barrier conductive layer A first polishing step for polishing the layer to expose the barrier conductor layer of the convex portion, and a second polishing for polishing at least the barrier conductor layer and the conductive material layer of the concave portion to expose the interlayer insulating film of the convex portion The metal-polishing liquid according to claim 1, wherein the metal-polishing liquid is used in at least the first polishing step among the polishing steps including the steps.   The metal according to any one of claims 10 to 12, wherein the conductive material to be polished is used in a polishing step including at least one selected from the group consisting of copper, copper alloy, copper oxide, and copper alloy oxide. Polishing liquid.   The barrier conductor layer is a barrier layer that prevents the conductive material from diffusing into the interlayer insulating film. Tantalum, tantalum nitride, tantalum alloy, other tantalum compounds, titanium, titanium nitride, titanium alloys, other titanium compounds, The metal-polishing liquid according to any one of claims 10 to 13, which is used in a polishing step containing at least one selected from tungsten, tungsten nitride, a tungsten alloy, and other tungsten compounds.   The metal polishing slurry according to any one of claims 12 to 14, which is used in a polishing step in which the interlayer insulating film is a silicon-based film or an organic polymer film.   A polishing cloth while supplying the metal-polishing liquid according to claim 1 between the surface to be polished and the polishing cloth in a state where the substrate having the surface to be polished is pressed onto the polishing cloth of the polishing surface plate. A polishing method characterized in that the surface to be polished is polished by relatively moving the substrate and the substrate.   The polishing method according to claim 16, wherein the metal to be polished is a conductive substance or a barrier conductor layer.   Conductive material of a substrate having an interlayer insulating film having a concave portion and a convex surface, a barrier conductor layer covering the interlayer insulating film along the surface, and a conductive material layer filling the concave portion and covering the barrier conductive layer A first polishing step for polishing the layer to expose the barrier conductor layer of the convex portion, and a second polishing for polishing at least the barrier conductor layer and the conductive material layer of the concave portion to expose the interlayer insulating film of the convex portion A polishing method using the metal polishing slurry according to any one of claims 1 to 15 in at least a first polishing step among polishing steps including a step.   The polishing method according to claim 17 or 18, wherein a polishing rate ratio between the conductive material and the barrier conductor layer is 20 or more: 1.   The polishing method according to claim 17, wherein the conductive substance to be polished contains at least one selected from the group consisting of copper, copper alloys, copper oxides, and copper alloy oxides.   The barrier conductor layer is a barrier layer that prevents the conductive material from diffusing into the interlayer insulating film. Tantalum, tantalum nitride, tantalum alloy, other tantalum compounds, titanium, titanium nitride, titanium alloys, other titanium compounds, The polishing method according to any one of claims 18 to 20, comprising at least one selected from tungsten, tungsten nitride, a tungsten alloy, and other tungsten compounds.   The polishing method according to any one of claims 18 to 21, wherein the interlayer insulating film is a silicon-based film or an organic polymer film.

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