JP4684121B2 - Chemical mechanical polishing abrasive and substrate polishing method - Google Patents

Description

  The present invention relates to an abrasive for chemical mechanical polishing particularly suitable for polishing a wiring formation process of a semiconductor device, and a method for polishing a substrate using the same.

  In recent years, new microfabrication techniques have been developed along with higher integration and higher performance of semiconductor integrated circuits (hereinafter referred to as LSIs). The chemical mechanical polishing (hereinafter referred to as 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, and buried wiring formation. . This technique is disclosed in, for example, US Pat. No. 4,944,836.

  Recently, in order to improve the performance of LSIs, the use of copper or copper alloys as wiring materials has been attempted. However, it is difficult to finely process copper or a copper alloy by a dry etching method frequently used in forming a conventional aluminum alloy wiring. Therefore, a so-called damascene method is mainly used in which a copper or copper alloy thin film is deposited and embedded on an insulating film in which a groove is formed in advance, and a copper or copper alloy thin film other than the groove is removed by CMP to form a buried wiring. Has been adopted. This technique is disclosed in Patent Document 1, for example.

  A general method of metal CMP such as copper or copper alloy is to apply a polishing pad on a circular polishing platen (platen), immerse the polishing pad surface with an abrasive and press the surface on which the metal film of the substrate is formed Then, the polishing platen is turned with a predetermined pressure (hereinafter referred to as polishing pressure) applied from the back surface, and the metal film on the convex portion is removed by mechanical friction between the abrasive and the convex portion of the metal film. is there.

  The polishing agent used for CMP is generally composed of an oxidizing agent and abrasive grains, and a metal oxide dissolving agent and a protective film forming agent are further added as necessary. It is considered that the basic mechanism of CMP by this CMP abrasive is to first oxidize the metal film surface with an oxidizing agent and scrape the oxidized layer with 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 abrasive grains does not reach, the metal layer of the projection is removed and the substrate surface is flattened with the progress of CMP. This detail is disclosed in Non-Patent Document 1.

  In order to increase the polishing rate by CMP, it is considered effective to add a metal oxide dissolving agent. It can be interpreted that this is because if the metal oxide particles scraped by the abrasive grains are dissolved in the abrasive (hereinafter referred to as etching), the effect of scraping by the abrasive grains increases. However, when the metal oxide solubilizer is added, the oxide layer on the surface of the metal film in the recess is also etched (dissolved), and when the metal film surface is exposed, the metal film surface is further oxidized by the oxidant. If this is repeated, etching of the metal film in the recesses proceeds. For this reason, the phenomenon that the central portion of the surface of the metal wiring embedded after polishing is depressed like a dish (hereinafter referred to as “dicing”) occurs, and the planarization effect is impaired.

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

  In order to suppress corrosion during dishing or polishing of copper or copper alloy and to form highly reliable LSI wiring, aminoacetic acid or amide sulfuric acid such as glycine is used as a metal oxide dissolving agent, and benzoic acid is used as a protective film forming agent. An abrasive for CMP using triazole (hereinafter referred to as BTA) has been proposed. This technique is described in Patent Document 2, for example.

  In metal buried formation such as damascene wiring formation of copper or copper alloy or plug wiring such as tungsten, the polishing rate of the silicon dioxide film, which is an interlayer insulating film formed other than the embedded portion, is close to the polishing rate of the metal film. As a result, a phenomenon called thinning occurs in which the thickness of the wiring is reduced along with the interlayer insulating film. As a result, resistance variation occurs due to an increase in wiring resistance, pattern density, or the like. For this reason, the polishing agent for CMP is required to have a characteristic that the polishing rate of the silicon dioxide film is sufficiently small with respect to the metal film to be polished. Therefore, in order to suppress the polishing rate of silicon dioxide by anions generated by acid dissociation, a method of increasing the pH of the polishing agent to be higher than pKa-0.5 has been proposed. This technique is described in Patent Document 3, for example.

  On the other hand, tantalum, a tantalum alloy, tantalum nitride, other tantalum compounds, and the like are formed as a barrier layer to prevent copper diffusion into the interlayer insulating film in a lower layer such as copper or copper alloy of the wiring. 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 the conductors constituting these barrier layers have higher hardness than copper or copper alloys, a combination of polishing materials for copper or copper alloys cannot often provide a sufficient polishing rate. 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.

In the second step, CMP of the barrier layer, it is necessary to prevent the copper or copper alloy embedded wiring portion from being diced, and the pH of the polishing agent is decreased in order to suppress the polishing rate and etching rate of copper or copper alloy. That was considered a negative effect.
JP-A-2-278822 Journal of Electrochemical Society, Vol. 138, Issue 11 (1991), pages 3460-3464 JP-A-8-83780 Japanese Patent No. 2819196

  Tantalum, tantalum alloys, and tantalum compounds (such as tantalum nitride) used as the barrier layer are chemically stable and difficult to etch, and have high hardness, so mechanical polishing is not as easy as copper and copper alloys. For this reason, when the hardness of the abrasive grains is increased, polishing flaws may occur in copper or a copper alloy, which may cause electrical characteristics defects. Further, when the particle concentration of the abrasive grains is increased, there is a problem that the polishing rate of the silicon dioxide film increases and thinning occurs.

  The present invention suppresses the occurrence of dicing, thinning and polishing flaws in copper or copper alloy wiring, realizes high-speed polishing of the barrier layer at a low abrasive concentration, and forms a highly reliable embedded pattern of a metal film. An object of the present invention is to provide a CMP polishing agent and a method for polishing a substrate using the same.

  As a result of intensive studies to achieve this object, the present inventors have found that polishing of tantalum, tantalum alloy and tantalum compound, which are conductors used as a barrier layer, has a low pH of the polishing agent and a concentration of the oxidizing agent. When it was low, it was found that it proceeded easily, leading to the present invention. In the present invention, an oxidizing agent for these conductors, a protective film forming agent for the metal surface, an abrasive containing acid and water, the pH is 3 or less, and the concentration of the oxidizing agent is 0.01 to 3 A first chemical mechanical polishing abrasive that is weight percent is provided. The first abrasive may further contain abrasive grains.

  Increasing the hardness of the abrasive grains when polishing the barrier layer may cause polishing flaws in the copper alloy and cause electrical characteristics defects. Increasing the abrasive grain concentration increases the polishing rate of the silicon dioxide film. There has been a problem that it becomes large and thinning may occur.

  The present inventors have found that polishing of tantalum, a tantalum alloy, tantalum nitride, and other tantalum compounds used as a barrier layer easily proceeds in a low pH region and a low oxidizing agent concentration region. In addition, when such an abrasive for CMP is used, the oxidant concentration is a sufficiently low region, so that wiring dicing due to an increase in the etching rate of copper and copper alloy, which is generally a problem in a low pH region, is also a problem. I knew it would n’t be.

  Further, the inventors of the present invention have found that when polishing the tantalum, tantalum alloy or tantalum compound used as the barrier layer conductor, if the abrasive grain size is too large, the polishing rate of the barrier layer decreases, and the polishing rate of silicon dioxide It was found that the polishing rate of silicon dioxide increases if the standard deviation of the particle size distribution is too small even if the abrasive grain size is small. This phenomenon is remarkable when polishing tantalum, a tantalum alloy, or a tantalum compound with an abrasive having a low pH and a low oxidizing agent concentration.

  When such an abrasive is used, since the oxidant concentration is a sufficiently low region, wiring dicing due to an increase in the etching rate of copper or copper alloy, which is generally a problem in a low pH region, does not become a problem. It was found that the erosion was small due to the low abrasive concentration.

  Therefore, in the present invention, a conductor containing an oxidizing agent, a protective film forming agent for a metal surface, an abrasive containing acid and water, including abrasive grains, the average grain size of the abrasive grains is 50 nm or less, An abrasive with a standard deviation value of distribution greater than 5 nm is provided.

  In addition, as for this abrasive | polishing agent of this invention, it is desirable that pH is 3 or less and the density | concentration of an oxidizing agent is 0.01 to 3 weight%. By making the polishing agent at a low pH and a low oxidizing agent concentration, it is possible to suppress the occurrence of dishing, thinning and polishing scratches in the copper or copper alloy wiring, and to realize a high polishing rate of the barrier layer at a low abrasive concentration. it can.

  The CMP abrasive | polishing agent of this invention can contain a water-soluble polymer further, and it is preferable that the density | concentration of the oxidizing agent in that case is 0.01 to 1.5 weight%. The water-soluble polymer is preferably at least one selected from the group consisting of polyacrylic acid or a salt thereof, polymethacrylic acid or a salt thereof, polyamic acid and a salt thereof, polyacrylamide, polyvinyl alcohol, and polyvinylpyrrolidone.

  The acid is preferably an organic acid, and more preferably at least one selected from malonic acid, malic acid, tartaric acid, glycolic acid and citric acid.

  The conductor oxidizing agent is preferably at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water.

  The protective film forming agent is preferably at least one selected from benzotriazole (BTA) and derivatives thereof (hereinafter referred to as BTAs).

  The abrasive is preferably at least one selected from silica, alumina, ceria, titania, zirconia, germania, and silicon carbide, and colloidal silica or colloidal alumina having an average particle size of 50 nm or less is suitable for the present invention. The average particle size of the abrasive grains is particularly preferably 30 nm or less, and the standard deviation of the particle size distribution is particularly preferably 10 nm or more. The abrasive concentration is preferably 0.05 to 10% by weight, more preferably 0.1 to 5% by weight, and particularly preferably 0.2 to 3% by weight. The colloidal silica is preferably one produced by hydrolysis of silicon alkoxide, but one produced using sodium silicate as a raw material can also be used.

The polishing slurry for CMP of the present invention has a polishing rate ratio (Ta / Cu, TaN / Cu) of tantalum or tantalum nitride and copper (including a copper alloy) greater than 1, and tantalum or tantalum nitride and a silicon dioxide film. And the polishing rate ratio (Ta / SiO ₂ , TaN / SiO ₂ ) is preferably larger than 10.

  Conductors (including semiconductors) suitable for polishing using the CMP polishing slurry of the present invention include copper, copper alloys, copper oxides, and tantalums that constitute their barrier layers (layers for preventing the diffusion of copper atoms), Examples include tantalum alloys and tantalum compounds (such as tantalum nitride). Therefore, in the present invention, a polishing method for polishing a barrier layer containing tantalum, a tantalum alloy and a tantalum compound (such as tantalum nitride) using the CMP polishing slurry of the present invention, and the CMP polishing slurry of the present invention are used. Thus, there is provided a polishing method for polishing a surface including a wiring layer (copper, copper alloy and / or oxide thereof) and a barrier layer (a layer for preventing diffusion of copper atoms).

The abrasive | polishing agent of this invention is suitable when the board | substrate which formed and filled the barrier layer and the metal film containing a copper or copper alloy on the board | substrate which has the recessed part of a silicon dioxide on the surface is suitable for grinding | polishing object. For example, as shown in FIG. 1, a silicon dioxide film 11 is formed on the surface of a silicon wafer 10 ( FIG. 1A ) as shown in FIG. 1 (FIG. 1B), and a resist having a predetermined pattern is formed on this surface. A layer 12 is formed (FIG. 1C), a recess 13 is formed in the silicon dioxide film 11 by dry etching to remove the resist layer 12 ( FIG. 1D ), and the surface of the silicon dioxide film 11 and the silicon wafer. The barrier layer 14 is formed by depositing a barrier metal such as tantalum by vapor deposition or CVD so as to cover the exposed portion 10 (FIG. 1E), and a metal such as copper is vapor deposited and plated on the surface thereof. Alternatively, it is obtained by forming a film by CVD to form the wiring layer 15 (FIG. 1 (f)).

  When this substrate was subjected to CMP using a polishing agent for copper and a copper alloy having a sufficiently large polishing rate ratio of wiring layer (copper and / or copper alloy) / barrier layer, a convex portion of the substrate (that is, silicon dioxide 11 was provided). A desired conductor pattern is obtained in which the barrier layer 14 is exposed on the surface and the wiring layer (copper or copper alloy film) 15 is left in the recess (FIG. 1G).

  When this substrate is further polished using a CMP abrasive capable of polishing both the barrier layer 14 and the wiring layer 15, a semiconductor substrate with the silicon dioxide 11 exposed on the surface is obtained as shown in FIG. can get.

  The first polishing slurry for CMP of the present invention is a polishing agent containing a conductor oxidizing agent, a protective film forming agent for a metal surface, an acid and water, having a pH of 3 or less, and an oxidizing agent concentration. It is adjusted to be 0.01 to 3% by weight. If necessary, a water-soluble polymer and abrasive grains may be added.

  When the pH of the polishing slurry for CMP is higher than 3, the polishing rate of tantalum, tantalum alloy and / or tantalum compound is low. 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 hydride.

  In addition, the polishing rate of tantalum, a tantalum alloy and / or a tantalum compound becomes maximum when the concentration of the oxidant in the conductor is around 0.15% by weight. A primary oxide layer that is easily mechanically polished is formed on the surface of the conductor film such as tantalum, tantalum alloy, and tantalum compound by the oxidizing agent, and a high polishing rate can be obtained.

  In general, when the pH is smaller than 3, the etching rate of the copper or copper alloy film is high, and it is difficult to suppress the etching with the protective film forming agent. However, in the present invention, since the concentration of the oxidizing agent is sufficiently low, the etching suppression by the protective film forming agent is possible. If the concentration of the oxidant exceeds 3% by weight, the etching rate of copper or copper alloy increases, and not only does dishing easily occur, but also conductors such as tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds. Since a secondary oxide layer that is harder to polish than the primary oxide layer is formed on the film surface, the polishing rate decreases. When the concentration of the oxidizing agent is less than 0.01% by weight, the oxide layer is not sufficiently formed, so that the polishing rate becomes low, and the tantalum film may be peeled off.

  The first CMP polishing slurry of the present invention may further contain abrasive grains, and the average particle size may be 100 nm or less so that the dispersion stability is high and the number of polishing scratches is small. It is desirably 50 nm or less.

  The second polishing slurry for CMP of the present invention is a polishing slurry for CMP containing a conductor oxidizing agent, a protective film-forming agent for metal surfaces, an acid and water, and further has an average particle size of 50 nm or less, and Abrasive grains having a standard deviation of the particle size distribution larger than 5 nm are included. This second abrasive is also preferably adjusted so that the pH is 3 or less and the concentration of the conductor oxidizing agent is 0.01 to 3% by weight. A water-soluble polymer may be added as necessary. Abrasive grains having an average grain size of 30 nm or less and a standard deviation of the grain size distribution of more than 10 nm are particularly suitable for the present invention. When the average particle size is larger than 50 nm, the polishing rate of the barrier layer film is small and the polishing rate of the silicon dioxide film is high. Even when the average particle size is 50 nm or less, if the standard deviation of the particle size distribution is less than 5 nm, the polishing rate of the silicon dioxide film tends to increase.

  In the first or second CMP polishing slurry of the present invention, the concentration of the conductor oxidizing agent is preferably 0.01 to 1.5% by weight when it contains a water-soluble polymer. Since the water-soluble polymer is adsorbed on the surface of tantalum, tantalum alloy, tantalum compound, or its oxide film, the oxidant concentration range in which a high polishing rate can be obtained becomes small. Further, since the water-soluble polymer is particularly easily adsorbed on the surface of a nitride compound film such as a tantalum nitride film or titanium nitride, it is considered that the polishing rate of the nitride compound film such as a tantalum nitride film or titanium nitride is reduced. On the other hand, the water-soluble polymer has the effect of forming a metal surface protective film and improves planarization characteristics such as dishing and thinning.

Examples of the conductor oxidizing agent in the present invention include hydrogen peroxide (H ₂ O ₂ ), nitric acid, potassium periodate, hypochlorous acid, ozone water, etc. Among them, hydrogen peroxide is particularly preferable. When the substrate is a silicon substrate including an integrated circuit element, contamination by alkali metal, alkaline earth metal, halide, or the like is not desirable, and thus 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. However, if the substrate to be applied is a glass substrate that does not include a semiconductor element, an oxidant that includes a nonvolatile component may be used.

  Examples of the acid used in the present invention include formic acid or organic acids (acetic acid, propionic acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n -Heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, Maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, etc.), and salts such as ammonium salts, sulfuric acid, nitric acid, ammonia, ammonium salts such as ammonium persulfate, ammonium nitrate, ammonium chloride, chromic acid, etc. A mixture thereof can be used. Among these, malonic acid, malic acid, tartaric acid, glycolic acid, and citric acid are preferable in that a practical CMP polishing rate can be obtained.

  The protective film forming agent in the present invention is benzotriazole (BTA), a BTA derivative (for example, tolyltriazole obtained by substituting one hydrogen atom of a benzene ring of BTA with a methyl group, benzoate substituted with a carboxyl group or the like. Triazole 4-carboxylic acid, its methyl, ethyl, propyl, butyl and octyl esters), naphthotriazole, naphthotriazole derivatives or mixtures containing these.

  Examples of the water-soluble polymer used in the present invention include polyacrylic acid, polyacrylic acid ammonium salt, polyacrylic acid sodium salt, polymethacrylic acid, polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, and polyacrylamide. Examples thereof include a polymer having a monomer having a group as a basic structural unit or a salt thereof, and a polymer having a monomer having a vinyl group such as polyvinyl alcohol and polyvinylpyrrolidone as a basic structural unit. 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. Therefore, an acid or an ammonium salt thereof is desirable. This is not the case when the substrate is a glass substrate or the like. By adding these water-soluble polymers, the dishing characteristics can be improved due to the effect of inhibiting etching by the protective film forming agent.

In the present invention, the polishing rate ratio (Ta / Cu, TaN / Cu) of tantalum or tantalum nitride and copper (including a copper alloy) is larger than 1, and the polishing rate of tantalum or tantalum nitride and silicon dioxide. An abrasive for CMP having a ratio (Ta / SiO ₂ , TaN / SiO ₂ ) greater than 10 is provided.

As described above, in the present invention, tantalum used as a barrier layer is obtained by reducing the pH of the polishing slurry for CMP to less than 3 (low oxidizing agent concentration is around 0.15% by weight). The polishing rate of tantalum alloy, tantalum alloy, tantalum nitride, and other tantalum compounds is maximized. If the pH is less than 3, the etching rate of copper and copper alloy film increases, but the protective layer is formed because the oxidant concentration is sufficiently low. If abrasive grains such as colloidal silica and colloidal alumina having an average particle diameter of 50 nm that reduce the polishing rate of silicon dioxide are possible, it is possible to suppress tantalum or tantalum nitride and copper (including copper alloys). The polishing rate ratio (Ta / Cu, TaN / Cu) is larger than 1, and the polishing rate ratio between tantalum or tantalum nitride and silicon dioxide (Ta / S) O _2, TaN / SiO ₂₎ to may be greater than 10.

  As abrasive grains of the abrasive for CMP of the present invention, any of inorganic abrasive grains such as silica, alumina, ceria, titania, zirconia, germania and silicon carbide, and organic abrasive grains such as polystyrene, polyacryl and polyvinyl chloride may be used. However, colloidal silica and colloidal alumina having good dispersion stability in an abrasive, a small number of polishing scratches (scratches) generated by CMP, and an average particle diameter of 50 nm or less are preferable. The average particle size is more preferably 30 nm or less, and particularly preferably 20 nm or less, in which the polishing rate of the barrier layer becomes larger and the polishing rate of silicon dioxide becomes smaller. As the colloidal silica, for example, one produced by hydrolysis of silicon alkoxide or ion exchange of sodium silicate can be used, and as the colloidal alumina, for example, one produced by hydrolysis of aluminum nitrate can be used.

  The addition amount of the abrasive grains in the first or second CMP polishing agent is preferably 0.01% by weight to 10% by weight with respect to the total weight, and is in the range of 0.05% by weight to 5% by weight. More preferably. If the blending amount is less than 0.01% by weight, there is no significant difference from the polishing rate when no abrasive grains are contained, and if it exceeds 10% by weight, no improvement in the polishing rate by CMP is observed even when more than 10% by weight is added.

  The CMP polishing slurry of the present invention is particularly suitable for polishing conductors (including semiconductors) such as copper, copper alloys, copper oxides, and their barrier layers (eg, tantalum, tantalum alloys, tantalum compounds (such as tantalum nitride)). is there.

  The blending amount of the acid in the abrasive of the present invention is preferably 0.0001 to 0.05 mol with respect to 100 g of the total amount of the conductor oxidizing agent, acid, protective film forming agent, water-soluble polymer and water, More preferably, it is 0.001 to 0.01 mol. When this compounding quantity exceeds 0.05 mol, there exists a tendency for the etching of copper or a copper alloy to increase.

  The blending amount of the protective film forming agent in the abrasive of the present invention is 0.0001 to 0.01 mol with respect to 100 g of the total amount of the conductor oxidizing agent, acid, protective film forming agent, water-soluble polymer and water. Is more preferable, and 0.0005 to 0.005 mol is more preferable. If this amount is less than 0.0001 mol, the etching of copper or copper alloy tends to increase, and even if it exceeds 0.01 mol, the effect remains unchanged.

  In the present invention, a water-soluble polymer can also be added, and the amount of the water-soluble polymer is 0. It is preferable to set it as 001-0.5 weight%, and it is more preferable to set it as 0.01-0.2 weight%. If the blending amount is less than 0.001% by weight, the combined effect with the protective film forming agent tends not to appear in etching suppression, and if it exceeds 0.5% by weight, the polishing rate by CMP tends to decrease.

In the polishing method for a substrate using the CMP polishing slurry of the present invention, the CMP polishing slurry is supplied to the polishing pad on the polishing surface plate, and is brought into contact with the surface to be polished to move the surface to be polished and the polishing pad relative to each other. A polishing method for polishing. As an apparatus for polishing, there is a general polishing apparatus having a polishing surface plate with a holder for holding a semiconductor substrate having a surface to be polished and a polishing pad attached (a motor etc. capable of changing the number of rotations is attached). Can be used. As the polishing pad, a general nonwoven fabric, foamed polyurethane, porous fluororesin, or the like can be used, and there is no particular limitation. The polishing conditions are not limited, but the rotation speed of the polishing surface plate is preferably a low rotation of 200 rpm or less so that the substrate does not jump out. The pressure applied to the polishing pad of the semiconductor substrate having the surface to be polished (film to be polished) is preferably 9.8 to 98.1 KPa (100 to 1000 gf / cm ² ). In order to satisfy the flatness of the pattern, it is more preferably 9.8 to 49.0 KPa (100 to 500 gf / cm ² ). During polishing, a polishing slurry for CMP is continuously supplied to the polishing pad by a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of a polishing pad is always covered with the abrasive | polishing agent. The semiconductor 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.

Hereinafter, the present invention will be described specifically by way of examples. The present invention is not limited by these examples.
(1) Preparation of Chemical Mechanical Polishing Abrasive As shown in Table 1, 0.4% by weight of acid, abrasive grains (however, Reference Example 1 was not added, Examples 2 to 8 and Reference Example 9 were 1 part by weight) Examples 10 to 11 and Reference Examples 12 to 13 are 1% by weight), 0.05 part by weight of a water-soluble polymer (however, only Examples 4, 6, and 7), and protective film forming agent (BTA) 0. 2% by weight of water ( Reference Example 1 , Examples 2 to 8, Reference Example 9 is 98.85 parts by weight, Examples 10 to 11 and Reference Examples 12 to 13 are 97.9% by weight) and dissolved. Further, a product obtained by adding hydrogen peroxide water (reagent special grade, 30% aqueous solution) as an oxidant for the conductor was used as an abrasive for CMP. In addition, the colloidal silica with an average particle diameter of 20-60 nm produced by the hydrolysis in the ammonia solution of tetraethoxysilane was added to the abrasive grain. The pKa of malic acid and glycolic acid used is 3.2, respectively.

(However, Example 1 in the table is Reference Example 1, Example 9 is Reference Example 9, Example 12 is Reference Example 12, and Example 13 is Reference Example 13.)

(2) Polishing CMP was performed using the obtained polishing slurry for CMP. The polishing conditions are as follows.
substrate:
Silicon substrate with a 200 nm thick tantalum film Silicon substrate with a 100 nm thick tantalum nitride film Silicon substrate with a 1 μm thick silicon dioxide film Silicon substrate polishing pad with a 1 μm thick copper film: Independent Foamed polyurethane resin with bubbles Polishing pressure: 250 gf / cm ²
Relative speed between substrate and polishing surface plate: 18m / min

(3) Polished Product Evaluation Items The following items were evaluated for the polished products subjected to CMP.
Polishing rate by CMP:
The film thickness difference before and after CMP of the film was calculated from the electric resistance value.
Etching rate:
The copper layer thickness difference before and after immersion in the chemical mechanical polishing abrasive stirred at 25 ° C. and 100 rpm was calculated from the electrical resistance value.
Dishing amount:
A groove having a depth of 0.5 μm is formed in silicon dioxide, a tantalum nitride film having a thickness of 50 nm is formed as a barrier layer by a known sputtering method, and a copper film is similarly formed by a sputtering method, followed by a known heat treatment. Two-step polishing is performed using the embedded silicon substrate as a substrate, and the surface shape of the stripe pattern portion in which the wiring metal portion width of 100 μm and the insulating film portion width of 100 μm are alternately arranged by a stylus type step meter The amount of film reduction in the wiring metal part was determined. As the first-stage polishing agent for copper, polishing was performed using a polishing agent for copper and copper alloy having a sufficiently high polishing rate ratio of copper to tantalum nitride. After the first stage polishing, a substrate sample is prepared so that the amount of dishing measured with the barrier layer exposed on the insulating film portion is 50 nm, and the chemical mechanical polishing abrasive is used until the barrier layer disappears in the insulating film portion. Was polished in two steps.
Thinning amount:
The surface shape of the stripe pattern part having a total width of 2.5 mm in which the wiring metal part width of 45 μm and the insulating film part width of 5 μm are alternately formed on the substrate for evaluating the amount of dicing is measured with a stylus-type step gauge. The amount of film reduction of the insulating film portion near the center of the pattern with respect to the insulating film field portion around the pattern was determined. After the first stage polishing, a substrate sample was prepared so that the thinning amount measured with the barrier layer exposed on the insulating film portion was 20 nm, and the chemical mechanical polishing abrasive until the barrier layer disappeared in the insulating film portion. Was polished in two steps.

(4) Evaluation Results Table 2 shows the polishing rate by CMP in each example. In addition, Table 3 shows the amount of dishing and the amount of thinning.

(However, Example 1 in the table is Reference Example 1, Example 9 is Reference Example 9, Example 12 is Reference Example 12, and Example 13 is Reference Example 13.)

(However, Example 1 in the table is Reference Example 1, Example 9 is Reference Example 9, Example 12 is Reference Example 12, and Example 13 is Reference Example 13.)

In all of Examples 1 to 13, good dishing and thinning characteristics were obtained. In particular, Reference Example 1 and Examples 2 to 6 having an oxidizing agent concentration of 0.01 to 3% by weight and a pH of 3 or less are particularly preferable because the polishing rate of tantalum and tantalum nitride is large, and the amount of dishing and thinning is small. . In Examples 10 and 11, the polishing rate of the tantalum and tantalum nitride films, which are the barrier layer conductors, is high, and the polishing rate of the silicon dioxide film is relatively low. Therefore, good dishing and thinning characteristics can be obtained.

  In particular, Examples 4 and 6 in which a water-soluble polymer is used and the concentration of the oxidizing agent is in the range of 0.01 to 1.5 wt. Compared to the weight%), the amount of dishing and the amount of thinning are small and good. In the case of using a water-soluble polymer, the concentration of the oxidizing agent is preferably 0.01 to 1.5% by weight, and if the amount added is larger than that, the polishing rate of tantalum or tantalum nitride tends to decrease. Therefore, the amount of thinning increases.

Further, Example 2 in which the concentration of the oxidizing agent is 3% by weight or less and the pH is 3 or less has a slower etching rate of copper as compared with Example 8 in which the concentration of the oxidizing agent exceeds 3% by weight. Compared with Reference Example 9 having a pH of more than 3, the polishing rate of tantalum or tantalum nitride is high, and the amount of dishing and thinning is small, which is preferable.

In Examples 10 and 11, the polishing rate of the barrier layer film (particularly the tantalum film) is higher and the polishing rate of the silicon dioxide film is lower than that of Reference Example 12 in which the grain size of the abrasive grains is large. Is excellent. In Examples 10 and 11, the polishing rate of the barrier layer film (particularly the tantalum film) is equivalent to that of Reference Example 13 having a small standard deviation of the particle size distribution. Excellent thinning characteristics.

  As described above, according to the present invention, tantalum, tantalum alloy, tantalum compound, etc. used as a barrier layer can be efficiently polished, and copper or copper alloy wiring can be diced, thinned, and polished. It is possible to suppress and form a highly reliable embedded pattern of a metal film.

FIG. 1 is an explanatory view showing a substrate polishing step in the embodiment.

Claims (17)

A polishing agent for chemical mechanical polishing having a pH of 3 or less for polishing at least one kind of barrier layer selected from the group consisting of at least tantalum, a tantalum alloy, and a tantalum compound,
Abrasive grain, conductor oxidant, protective film forming agent for metal surface, acid, and water, the average grain size of the abrasive grains is 50 nm or less, and the standard deviation of the grain size distribution of the abrasive grains Chemical mechanical polishing abrasive with a value greater than 5 nm. The chemical mechanical polishing abrasive according to claim 1, wherein the conductor has an oxidizing agent concentration of 0.01 to 3 wt%.   The abrasive for chemical mechanical polishing according to claim 1 or 2, wherein the abrasive is at least one selected from silica, alumina, ceria, titania, zirconia and germania.   The abrasive for chemical mechanical polishing according to claim 3, wherein the abrasive grains are colloidal silica or colloidal alumina.   The compounding quantity of the said abrasive grain is 0.1 to 5 weight%, The chemical mechanical polishing abrasive | polishing agent in any one of Claims 1-4.   The abrasive for chemical mechanical polishing according to any one of claims 1 to 5, further comprising a water-soluble polymer.   The water-soluble polymer is at least one selected from the group consisting of polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyamic acid, polyamidate, polyacrylamide, polyvinyl alcohol and polyvinylpyrrolidone. The abrasive for chemical mechanical polishing according to claim 6.   The chemical mechanical polishing abrasive according to claim 6 or 7, wherein the conductor has an oxidizing agent concentration of 0.01 to 1.5 wt%.   The chemical mechanical polishing abrasive according to any one of claims 1 to 8, wherein the acid is an organic acid.   The chemical mechanical polishing abrasive according to claim 9, wherein the acid is at least one selected from malonic acid, malic acid, tartaric acid, glycolic acid and citric acid.   The chemical mechanical polishing abrasive according to any one of claims 1 to 10, wherein the protective film forming agent is at least one selected from benzotriazole or a derivative thereof.   The chemical mechanical polishing polishing according to any one of claims 1 to 11, wherein the conductor oxidizing agent is at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water. Agent.   The abrasive | polishing agent for chemical mechanical polishing in any one of Claims 1-12 in which the said conductor contains at least any one of copper, a copper alloy, a copper oxide, and a copper alloy oxide.   The abrasive for chemical mechanical polishing according to any one of claims 1 to 12, wherein the conductor is a barrier layer for preventing diffusion of copper atoms. The polishing rate ratio (Ta / Cu) between tantalum and copper or copper alloy is greater than 1, the polishing rate ratio between tantalum nitride and copper or copper alloy (TaN / Cu) is greater than 1, and tantalum and silicon dioxide The chemical mechanical polishing according to claim 1, wherein the polishing rate ratio (Ta / SiO ₂ ) is greater than 10 and the polishing rate ratio between tantalum nitride and silicon dioxide (TaN / SiO ₂ ) is greater than 10. Abrasive.   A method for polishing a substrate, comprising polishing a barrier layer containing tantalum, a tantalum alloy, and a tantalum compound using the chemical mechanical polishing abrasive according to claim 1.   A method for polishing a substrate, comprising polishing a surface including a wiring layer and a barrier layer using the chemical mechanical polishing abrasive according to claim 1.

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