JP2011014552A - Method of polishing substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of polishing substrate that exhibits both high polishing speed and planarity of a polished surface in polishing of a metal layer 30 of the substrate provided with the metal layer 30 on an interlayer insulating film 10 through a barrier layer 20.SOLUTION: The metal layer 30 is polished by using a first polishing liquid so as not to expose the barrier layer 20. The first polishing liquid is prepared by mixing, at a predetermined ratio, a first liquid containing an metal oxide dissolving agent, a metal anticorrosive, a metal oxide dissolution control agent and water, and a second liquid containing a metal oxidant. Then the metal layer 30 is polished by using a second polishing liquid which is prepared by mixing the first liquid and the second liquid so that the ratio of the second liquid is larger than that of the first polishing liquid, thereby a portion at an upper section of a protruding section 12 of the interlayer insulating film 10, of the barrier layer 30 is exposed.

Description

  The present invention relates to a substrate polishing method suitable for a wiring process of a semiconductor device.

  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 below.)

  In recent years, attempts have been made to use copper alloys as wiring materials in order to improve the performance of LSIs. 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 copper alloy thin film is deposited on the insulating film in which the groove and the ridge are formed in advance, and the copper alloy is embedded in the groove, and then the copper alloy thin film (copper alloy thin film other than the groove) deposited on the ridge is formed. A so-called damascene method in which buried wiring is formed by removal by CMP is mainly employed (see, for example, Patent Document 2 below).

  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 with a predetermined pressure (polishing pressure or polishing load) applied from the back surface, and the raised portion of the metal film is removed by mechanical friction between the polishing liquid and the raised portion of the metal film.

The metal polishing liquid used in CMP (hereinafter simply referred to as “polishing liquid”) generally contains a metal oxidizer and solid abrasive grains, and a metal oxide solubilizer, a metal anticorrosive, and the like are added as necessary. Is done. It is considered that the basic mechanism is to first oxidize the surface of the metal film by oxidation and scrape the oxidized layer with solid abrasive grains. Here, since the oxide layer on the metal surface of the groove portion of the insulating film does not touch the polishing pad so much and does not have the effect of scraping with the solid abrasive grains, the metal layer on the raised portion is mainly removed with the progress of CMP, and the substrate surface Is flattened (for example, see Non-Patent Document 1 below).
U.S. Pat. No. 4,944,836 JP-A-2-278822 Journal of Electrochemical Society, Vol.138, No.11 (1991), 3460-3464

  In the case of forming a buried wiring by CMP, it is effective to add a metal oxide dissolving agent as a method for increasing the polishing rate by CMP. It is interpreted that when the metal oxide particles scraped by the abrasive grains dissolve in the polishing liquid (hereinafter referred to as “etching”), the effect of scraping by the abrasive grains increases.

  However, when the polishing rate by CMP is improved by adding a metal oxide solubilizer, if the metal layer surface is exposed by etching the surface of the metal layer embedded in the groove, the metal oxide surface is further increased by the metal oxide agent. When this is repeated and this is repeated, etching also proceeds to the metal layer embedded in the groove. 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 flattening effect of the surface to be polished is impaired. On the other hand, if the amount of the metal oxide solubilizer is reduced so that dishing does not occur, a practically sufficient polishing rate cannot be obtained.

  The polishing speed can also be improved by increasing the rotational speed of either or both of the polishing surface plate and the polishing head on which the wafer is mounted, or by increasing the polishing load on the wafer. I can't get it.

  The present invention has been made in view of such a situation, and when polishing the metal layer of a substrate in which a metal layer is provided on an interlayer insulating film via a barrier layer, a high polishing rate and a surface to be polished are provided. An object of the present invention is to provide a method for polishing a substrate that can achieve both the flatness of the substrate.

In order to solve the above-described problems, the present invention follows an interlayer insulating film having a step portion defined by a raised portion and a groove portion adjacent to each other on one side, and a surface having the step portion of the interlayer insulating film. A method for polishing a substrate comprising: a barrier layer provided on the substrate; and a metal layer provided so as to cover the barrier layer,
A first liquid containing a metal oxide solubilizer, a metal anticorrosive, a metal oxide solubilizer, and water and a second liquid containing a metal oxidizer are mixed at a predetermined ratio. And a first step of polishing the metal layer using the first polishing liquid so that the barrier layer is not exposed,
The first liquid and the second liquid are mixed so that the ratio of the second liquid is larger than that of the first polishing liquid to obtain a second polishing liquid, and the second polishing liquid is used. A second step of polishing the metal layer after the first step and exposing a portion of the barrier layer located above the raised portion of the interlayer insulating film;
A polishing method characterized by comprising:

  According to this polishing method, as a polishing liquid in two chemical mechanical polishing (CMP) steps, a first liquid containing a metal oxide solubilizer, a metal anticorrosive, a metal oxide solubilizer, and a metal oxidizer are used. By using what was prepared by changing the mixing ratio with the second liquid contained, it is possible to control the polishing rate improvement effect and dishing suppression effect in each polishing step, and as a result, high polishing as a whole. It becomes possible to achieve both the speed and the flatness of the polished surface of the substrate finally obtained.

  Moreover, the 1st and 2nd polishing liquid used for the grinding | polishing method of this invention is obtained by mixing the common raw material liquid called a 1st liquid and a 2nd liquid as above-mentioned. Therefore, the polishing method of the present invention is useful from the viewpoint of simplifying the polishing liquid preparation process and reducing raw material costs.

  In the polishing method of the present invention, the content of the metal oxidant in the first polishing liquid is preferably 0.5 to 15% by weight based on the total weight of the first polishing liquid. On the other hand, the content ratio of the metal oxidizing agent in the second polishing liquid is preferably 10 to 20% by weight based on the total weight of the second polishing liquid.

  Moreover, it is preferable that the content rate of the metal oxide dissolving agent in a 1st polishing liquid is 0.001 to 10 weight% on the basis of the total weight of a 1st polishing liquid. On the other hand, the content ratio of the metal oxide dissolving agent in the second polishing liquid is preferably 0.001 to 10% by weight based on the total weight of the second polishing liquid.

  Moreover, it is preferable that the metal oxidizing agent used in the present invention is at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water.

  Moreover, it is preferable that a metal layer contains at least 1 sort (s) chosen from copper, a copper alloy, the oxide of copper, and the oxide of a copper alloy.

In preparing the substrate to be used in the polishing method of the present invention, the metal layer can be formed by depositing a metal on the barrier layer by a sputtering method, a plating method or the like. The metal layer may have a step portion corresponding to the step portion of the interlayer insulating film. More specifically, the metal is buried in the groove portion by depositing the metal above the groove portion of the interlayer insulating film. On the other hand, the metal is also deposited above the raised portion of the interlayer insulating film. Therefore, the surface to be polished of the metal layer is substantially composed of metal deposited above the raised portion of the interlayer insulating film, and the portion above the groove of the interlayer insulating layer of the metal layer has a shape recessed from the surface to be polished. . In the case of polishing such a substrate, in the first step, the metal layer may be polished so that the step before and after the polishing in the step portion of the metal layer satisfies the condition represented by the following formula (1). preferable. The “step” here means the depth from the surface to be polished in the step portion. Further, when the metal layer has a plurality of step portions, S ₁ and S ₂ each mean an average value of the steps for the plurality of step portions. Further, the step S ₁ before polishing in the step portion of the metal layer may be referred to as “initial step”, and the step S ₂ after polishing may be referred to as “residual step”.
0 ≦ S ₂ / S ₁ ≦ 0.2 (1)
[Equation (1), S ₁ is to be polished in the step portion of the metal layer step (unit: nm) indicates, S ₂ is the step (unit: nm) after polishing in the step portion of the metal layer showing a. ]

  In each of the first step and the second step, the polishing cloth is applied to the surface to be polished of the metal layer while supplying the first polishing liquid or the second polishing liquid to the polishing cloth of the polishing platen. In the pressed state, it is preferable to polish the metal layer by relatively moving the polishing platen and the substrate.

  According to the polishing method of the present invention, at the time of polishing a metal layer of a substrate provided with a metal layer on an interlayer insulating film via a barrier layer, both a high polishing rate and flatness of a surface to be polished are achieved. Is possible.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  FIG. 1 is a process sectional view schematically showing a preferred embodiment of the polishing method of the present invention. First, in the step (a), a substrate 100 to be used for polishing is prepared. The substrate 100 is provided so as to follow the interlayer insulating film 10 having a stepped portion 13 defined by the ridges 11 and the grooves 12 adjacent to each other on the surface 14 side, and the surface 14 having the stepped portion 13 of the interlayer insulating film 10. And a metal layer 30 provided so as to cover the barrier layer 20. In the wiring formation process of the semiconductor device, the interlayer insulating film 10, the barrier layer 20, and the metal layer 30 are usually formed on a base such as a silicon substrate. In FIG. It is omitted.

  Examples of the interlayer insulating film 10 include a silicon-based film and an organic polymer film. Silicon-based coatings include silicon dioxide, fluorosilicate glass, organosilicate glass obtained by using trimethylsilane or dimethoxydimethylsilane as a starting material, silica-based coatings such as silicon oxynitride, silsesquioxane hydride, and silicon. Examples thereof include carbide and silicon nitride. Examples of the organic polymer film include a wholly aromatic constant dielectric constant interlayer insulating film. For the formation of the interlayer insulating film 10, a CVD method, a spin coating method, a dip coating method, a spray method, or the like can be applied. Further, a photolithographic method or the like can be applied to the formation of the step portion 13 in the interlayer insulating film 10.

  The barrier layer 20 has a function of preventing metal diffusion from the metal layer 30 into the interlayer insulating film 10 and improving adhesion between the interlayer insulating film 10 and the metal layer 30. The constituent material of the barrier layer 20 is selected from tantalum, tantalum nitride, tantalum alloys and other tantalum compounds, titanium, titanium nitride, titanium alloys and other titanium compounds, and tungsten, tungsten nitride, tungsten alloys and other tungsten compounds. It is preferable that it is at least one kind. Although FIG. 1 shows an example in which the barrier layer 20 has a single layer structure, the barrier layer 20 may have a laminated structure of two or more layers.

  The metal layer 30 is composed mainly of a metal such as copper, copper alloy, copper oxide, copper alloy oxide, tungsten, tungsten alloy, silver, or gold. Among these, the polishing method of the present invention is suitable when the constituent material of the metal layer 30 is at least one selected from copper, a copper alloy, a copper oxide, and a copper alloy oxide.

The metal layer 30 can be formed by depositing the above-mentioned metal on the barrier layer 20 by sputtering or plating. The metal layer 30 thus formed is a step portion of the interlayer insulating film 10. 13 may be provided. That is, the metal is buried in the trench 11 by depositing the metal above the trench 11 of the interlayer insulating film 10, while the metal is deposited also on the raised portion 12 of the interlayer insulating film 10. Therefore, the portion 33 above the raised portion 12 of the interlayer insulating film 10 of the metal layer 30 substantially constitutes the surface to be polished, and the portion 32 above the groove 11 of the interlayer insulating layer 10 of the metal layer 30 is The shape is recessed from the surface to be polished. An arrow S _{1 in} FIG. 1 indicates a step (initial step) in the step portion 31.

  The substrate 100 having the above-described configuration is subjected to two stages of polishing steps (b) and (c) (first step and second step) as described later. In the first step and the second step, a first liquid containing a metal oxide solubilizer, a metal anticorrosive, a metal oxide solubilizer and water, and a second liquid containing a metal oxidizer. Two types of polishing liquids are prepared using the common raw material liquid, and are used for polishing the metal layer 30.

  As the metal oxide solubilizer contained in the first liquid, one or more acids and ammonium salts are suitable. The metal oxide solubilizer is not particularly limited as long as it is water-soluble, but malonic acid, citric acid, malic acid, glycolic acid, glutamic acid, glyconic acid, oxalic acid, tartaric acid, picolinic acid, nicotinic acid, mandelic acid, picolinic acid Acetic acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, hydrochloric acid, formic acid, succinic acid, adipic acid, glutaric acid, benzoic acid, quinaldic acid, butyric acid, valeric acid, lactic acid, phthalic acid, fumaric acid, maleic acid, aminoacetic acid, salicylic acid , Glyceric acid, pimelic acid and the like. Moreover, the ammonium salt of these acids, these organic acid ester, etc. are mentioned. It is also effective to use two or more acids or ammonium salts in combination in that the etching rate can be effectively suppressed while maintaining a practical CMP rate.

  As the metal anticorrosive, a compound having a triazole skeleton, a pyrimidine skeleton, an imidazole skeleton, a guanidine skeleton, a thiazole skeleton or a pyrazole skeleton is suitable. Two or more kinds of metal anticorrosives are used in combination in that the content of the metal anticorrosive in the polishing liquid is lowered, and polishing friction can be effectively suppressed while maintaining a balance between a practical CMP rate and an etching rate. It is also effective.

  Among the metal anticorrosives, compounds having a triazole skeleton include 2-mercaptobenzothiazol, 1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-1 , 2,4-triazole, benzotriazole, 1-hydroxybenzotriazole, 1-dihydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole, 4-hydroxybenzotri Azol, 4-carboxyl (-1H-) benzotriazole, 4-carboxyl (-1H-) benzotriazole methyl ester, 4-carboxyl (-1H-) benzotriazole butyl ester, 4-carboxyl (-1H -) Benzotriazol octyl ester, 5-hexylbenzotriazole, [1,2,3-benzotriazolyl 1-methyl] [1,2,4-triazolyl-1-methyl] [2-ethylhexyl] amine, tolyltriazole, naphthotriazole, bis [(1-benzotriazolyl) methyl] phosphonic acid, 3-amino Examples thereof include triazole and 5-methylbenzotriazole. Among these, in terms of the balance between the CMP rate and the etching rate, 1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-1,2,4-triazole, 4-Amino-4H-1,2,4-triazole, benzotriazole, 1-hydroxybenzotriazole, and 5-methylbenzotriazole are more preferable. These metal anticorrosives can be used alone or in combination of two or more.

  Examples of the compound having an imidazole skeleton include 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-propylimidazole, 2-butylimidazole, 4-methylimidazole, 2,4-dimethylimidazole, and 2-ethyl. Examples thereof include -4-methylimidazole, 2-undecylimidazole, 2-aminoimidazole and the like. These metal anticorrosives can be used alone or in combination of two or more.

  Examples of the compound having a pyrimidine skeleton include pyrimidine, 1,2,4-triazolo [1,5-a] pyrimidine, 1,3,4,6,7,8-hexahydro-2H-pyrimido [1,2, -A] pyrimidine, 1,3-diphenyl-pyrimidine-2,4,6-trione, 1,4,5,6-tetrahydropyrimidine, 2,4,5,6-tetraaminopyrimidine sulfate, 2,4 , 5-trihydroxypyrimidine, 2,4,6-triaminopyrimidine, 2,4,6-trichloropyrimidine, 2,4,6-trimethoxypyrimidine, 2,4,6-triphenylpyrimidine, 2,4- Diamino-6-hydroxylpyrimidine, 2,4-diaminopyrimidine, 2-acetamidopyrimidine, 2-aminopyrimidine, 2-methyl-5,7-dipheni Ru- (1,2,4) triazolo (1,5-a) pyrimidine, 2-methylsulfanyl-5,7-diphenyl- (1,2,4) triazolo (1,5-a) pyrimidine, 2- Methylsulfanyl-5,7-diphenyl-4,7-dihydro- (1,2,4) triazolo (1,5-A) pyrimidine, 4-aminopyrazolo [3,4, -d] pyrimidine, etc. In particular, 4-aminopyrazolo [3,4, -d] pyrimidine, 1,2,4-triazolo [1,5-a] pyrimidine, 2-methyl-5,7-diphenyl in terms of the balance between CMP rate and etching rate. -(1,2,4) triazolo (1,5-a) pyrimidine and 2-methylsulfanyl-5,7-diphenyl- (1,2,4) triazolo (1,5-a) pyrimidine are preferred. These may be used alone or in combination of two or more.

  Examples of the compound having a guanidine skeleton include 1,3-diphenylguanidine and 1-methyl-3-nitroguanidine. These metal anticorrosives can be used alone or in combination of two or more.

  Examples of the metal oxide dissolution regulator include polysaccharides such as alginic acid, pectic acid, carboxymethyl cellulose, agar, cardran, and pullulan; polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polymethacrylic acid. Acid ammonium salt, polymethacrylic acid sodium salt, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, ammonium polyacrylate, polyacrylic Examples thereof include polycarboxylic acids such as sodium acid salt, polyamic acid, ammonium polyamic acid salt, polyamic acid sodium salt and polyglyoxylic acid and salts thereof. Furthermore, examples of the salt of polycarboxylic acid include alkali metal salts, alkaline earth metal salts, halides and the like. When the substrate 100 is a silicon substrate for a semiconductor integrated circuit or the like, contamination with alkali metal, alkaline earth metal, halide, or the like is not desirable, so it is desirable to use polycarboxylic acid and its ammonium salt. On the other hand, this is not the case when the substrate 100 is a glass substrate or the like. Among the above metal oxide dissolution preparation agents, pectic acid, agar, polymalic acid, polymethacrylic acid, polyacrylic acid ammonium salt, polyacrylamide, esters thereof and ammonium salts thereof are preferable from the viewpoint of polishing rate and etching rate. .

  Moreover, as water contained in a 1st liquid, distilled water, ion-exchange water, or a pure water is suitable.

  On the other hand, examples of the metal oxidizing agent contained in the second liquid include hydrogen peroxide, ammonium persulfate, ferric nitrate, nitric acid, potassium periodate, hypochlorous acid, and ozone water. Is preferred. A metal oxidizing agent can be used individually by 1 type or in combination of 2 or more types. Note that when the substrate 100 is a silicon substrate including an integrated circuit element, contamination with alkali metal, alkaline earth metal, halide, or the like is not desirable, and therefore, it is preferable to use a metal oxidant that does not include a nonvolatile component. . However, hydrogen peroxide is most suitable because ozone water has a large compositional change over time. Note that in the case where the substrate 100 is a glass substrate that does not include a semiconductor element, a metal oxidant including a nonvolatile component may be used.

  Further, the second liquid may further contain water.

  In step (b), which is a previous polishing step, the metal layer 30 is polished using a first polishing liquid obtained by mixing the first liquid and the second liquid at a predetermined ratio. As a polishing method, for example, while supplying the first polishing liquid onto the polishing cloth of the polishing surface plate, the polishing surface plate and the substrate are relatively moved while the polishing surface of the metal layer 30 is pressed against the polishing cloth. Thus, a method of polishing the film to be polished is preferable. As a polishing apparatus, a general polishing apparatus having a surface plate (with a motor or the like capable of changing the number of rotations) attached with a holder (head) for holding a semiconductor substrate and a polishing cloth (pad) can be used. . As an abrasive cloth, a general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. can be used, and there is no restriction | limiting in particular. The polishing conditions are not limited, but the rotation speed of the 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 cloth of the semiconductor substrate having the film to be polished is preferably 1 to 100 kPa, and 5 to 50 kPa from the viewpoint of the uniformity of the polishing rate within the wafer surface and the flatness of the surface to be polished. More preferred. During polishing, the first polishing liquid is continuously supplied to the polishing cloth with a pump or the like. The supply amount is not limited, but it is preferable that the surface of the polishing cloth is always covered with the first 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 spin drying or the like.

  The mixing method of the first liquid and the second liquid is not particularly limited as long as these liquids are mixed before polishing and used as the first polishing liquid. For example, the first liquid and the second liquid may be mixed in advance, and the mixed liquid may be supplied to the polishing surface plate, or the first liquid and the second liquid may be separately supplied in the piping. Two liquids may be mixed.

  The content ratio of the metal oxide solubilizer in the first polishing liquid is preferably 0.001 to 10% by weight, preferably 0.01 to 1% by weight, based on the total weight of the first polishing liquid. It is more preferable that the content be 0.01 to 0.5% by weight. When this content is less than 0.001% by weight, the polishing rate tends to decrease. Moreover, when this content rate exceeds 10 weight%, there exists a tendency for an etching rate to become large and to corrode metal wiring easily. In addition, although the etching rate can be suppressed by increasing the content of the metal anticorrosive, in this case, polishing friction tends to increase.

  In addition, the content of the metal anticorrosive in the first polishing liquid is preferably 0.001 to 2.0% by weight based on the total weight of the first polishing liquid, and 0.01 to 0.00. It is more preferable to set it as 5 weight%, and it is especially preferable to set it as 0.02-0.2 weight%. If the content is less than 0.001% by weight, it tends to be difficult to suppress etching, and if it exceeds 2% by weight, a practically sufficient polishing rate tends not to be obtained.

  In addition, the content ratio of the metal oxide dissolution regulator in the first polishing liquid is preferably 0.001 to 10% by weight, based on the total weight of the first polishing liquid, and 0.01 to 5% by weight. % Is more preferable, and 0.1 to 2% by weight is particularly preferable. When this content ratio is less than 0.001% by weight, dishing of the metal wiring is deteriorated and the accumulation of the object to be polished on the polishing cloth tends to increase. On the other hand, if the content exceeds 10% by weight, the etching rate increases, and it is difficult to achieve both the polishing rate and the flatness of the surface to be polished.

  Further, the content of the metal oxidant in the first polishing liquid is preferably 0.5 to 15% by weight, based on the total weight of the first polishing liquid, and is 1.0 to 15% by weight. More preferably, it is 3.0 to 13% by weight. When the content of the metal oxidizer is less than 0.5% by weight or exceeds 15% by weight, the polishing rate tends to decrease.

  The pH of the first polishing liquid is preferably 2 to 5, more preferably 2.5 to 4.5, and particularly preferably 3.0 to 4.3. If the pH is less than 2, problems such as metal corrosion and surface roughness are likely to occur, and the content of the anticorrosive agent is increased to reduce it, so that the polishing friction also increases and wiring defects are likely to occur. On the other hand, if the pH is higher than 5, the corrosion rate of the metal is small and the content of the anticorrosive agent can be reduced, but it is difficult to obtain a sufficient polishing rate. In the present invention, the pH of the polishing liquid was measured using a pH meter (for example, Model pH 81 manufactured by Yokogawa Electric Corporation). More specifically, two-point calibration was performed using a standard buffer (phthalate pH buffer solution pH: 4.21 (25 ° C.), neutral phosphate pH buffer solution pH 6.86 (25 ° C.)). Thereafter, the electrode was placed in the polishing liquid, and the value after 2 minutes or more had stabilized was measured.

  In addition to the materials described above, the first polishing liquid further contains a solid abrasive such as alumina, silica, and ceria, a surfactant, a dye such as Victoria Pure Blue, and a colorant such as a pigment such as phthalocyanine green. Also good.

  The abrasive grains may be any of inorganic abrasive grains such as silica, alumina, zirconia, ceria, titania, silicon carbide, and organic abrasive grains such as polystyrene, polyacryl, polyvinyl chloride, etc., but dispersion stability in the polishing liquid Colloidal silica and colloidal alumina having an average particle size of 100 nm or less are preferred, colloidal silica and colloidal alumina having an average particle size of 80 nm or less are more preferred, and the average number of polishing scratches (scratches) generated by CMP is small. Most preferred is colloidal silica having a particle size of 60 nm or less. Colloidal silica is known for its production by hydrolysis of silicon alkoxide or ion exchange of sodium silicate, and colloidal alumina is known for its production by hydrolysis of aluminum nitrate. In the present invention, the particle size of the abrasive grains was measured with a light diffraction / scattering particle size distribution meter (for example, COULTER N4SD manufactured by COULTER Electronics). The degree of particle aggregation was measured with a transmission electron microscope (for example, H-7100FA manufactured by Hitachi, Ltd.). Coulter measurement conditions were as follows: measurement temperature 20 ° C., solvent refractive index 1.333 (water), particle refractive index Unknown (setting), solvent viscosity 1.005 cp (water), Run Time 200 sec, laser incident angle 90 °, intensity (scattering). Intensity, corresponding to turbidity) was measured by diluting with water when it was higher than 4E + 05 so that it was in the range of 5E + 04 to 4E + 05.

  The content ratio of the abrasive grains in the first polishing liquid is preferably 0.01 to 10.0% by weight, more preferably 0.05 to 2.0% by weight, based on the total weight of the first polishing liquid. 0.1 to 1.0% by weight is most preferable. When the content ratio of the abrasive grains is 0.01% by weight, the effect due to the addition of the abrasive grains tends not to be obtained. When the content ratio is 10.0% by weight or more, no further improvement in the effect corresponding to the content ratio is observed. There is a tendency.

Step (b) is a step of polishing the metal layer 30 using the first polishing liquid so that the barrier layer 20 is not exposed. In the substrate 200 after polishing in the step (b), a stepped portion is formed. Although the step (residual step) S _{2 at} 31 is smaller than the initial step S ₁ , the metal layer 30 still exists above the raised portion 12 of the interlayer insulating film 10. In the polishing in the step (b), the metal layer is preferably polished so that the initial step S ₁ and the remaining step S ₂ in the step portion 31 of the metal layer 30 satisfy the condition represented by the following formula (1).
0 ≦ S ₂ / S ₁ ≦ 0.2 (1)
[Equation (1), S ₁ is to be polished in the step portion of the metal layer step (unit: nm) indicates, S ₂ is the step (unit: nm) after polishing in the step portion of the metal layer showing a. ]

  Subsequently, in the step (c), the first liquid and the second liquid are polished using a second polishing liquid in which the ratio of the second liquid is larger than that of the first polishing liquid. I do. Note that the polishing method, polishing apparatus, polishing cloth, polishing conditions, and mixing method of the first liquid and the second liquid in the step (c) are the same as those in the step (b). A duplicate description is omitted.

  The second polishing liquid is obtained by mixing so that the ratio of the second liquid is larger than that of the first polishing liquid. Therefore, in the second polishing liquid, the content ratio of the metal oxide solubilizer derived from the first liquid is smaller than that in the first polishing liquid, and the metal oxidizing agent derived from the second liquid is reduced. The proportion increases. Furthermore, the content ratio of each component in the second polishing liquid preferably satisfies the conditions described later.

  The content of the metal oxide solubilizer in the second polishing liquid is preferably 0.001 to 10% by weight, and preferably 0.01 to 1% by weight, based on the total weight of the second polishing liquid. It is more preferable that the content be 0.01 to 0.5% by weight. When this content is less than 0.001% by weight, the polishing rate tends to decrease. Moreover, when this content rate exceeds 10 weight%, there exists a tendency for an etching rate to become large and to corrode metal wiring easily. In addition, although the etching rate can be suppressed by increasing the content of the metal anticorrosive, in this case, polishing friction tends to increase.

  Moreover, it is preferable that the content rate of the metal anticorrosive agent in a 2nd polishing liquid shall be 0.001-2.0 weight% on the basis of the total weight of a 2nd polishing liquid, 0.01-0. More preferably, the content is 5% by weight, and particularly preferably 0.02 to 0.15% by weight. If the content is less than 0.001% by weight, it tends to be difficult to suppress etching, and if it exceeds 2% by weight, a practically sufficient polishing rate tends not to be obtained.

  The content ratio of the metal oxide dissolution modifier in the second polishing liquid is preferably 0.001 to 10% by weight, based on the total weight of the second polishing liquid, and 0.01 to 5% by weight. % Is more preferable, and 0.1 to 2% by weight is particularly preferable. When the content is less than 0.001% by weight, the dishing of the metal wiring is deteriorated, the flatness of the surface to be polished is lowered, and further, the accumulation of the object to be polished on the polishing cloth tends to increase. On the other hand, if the content exceeds 10% by weight, the etching rate increases, and it is difficult to achieve both the polishing rate and the flatness of the surface to be polished.

  The content ratio of the metal oxidant in the second polishing liquid is preferably 0.5 to 15% by weight, based on the total weight of the second polishing liquid, and is 1.0 to 15% by weight. More preferably, it is 3.0 to 13% by weight. When the content of the metal oxidizer is less than 0.5% by weight or exceeds 15% by weight, the polishing rate tends to decrease.

  The pH of the second polishing liquid is preferably 2 to 5, more preferably 2.5 to 4.5, and particularly preferably 3.0 to 4.3. If the pH is less than 2, problems such as metal corrosion and surface roughness are likely to occur, and the content of the anticorrosive agent is increased to reduce it, so that the polishing friction also increases and wiring defects are likely to occur. On the other hand, if the pH is higher than 5, the corrosion rate of the metal is small and the content of the anticorrosive can be reduced, but it is difficult to obtain a sufficient polishing rate.

  In addition, the second polishing liquid may further contain solid abrasive grains, a surfactant, a colorant, and the like, like the first polishing liquid.

  In the step (c), following the step (b), the metal layer 30 is polished using the second polishing liquid, and a portion of the barrier layer 20 located above the raised portion 12 of the interlayer insulating film 10 is exposed. In the substrate 300 after polishing in the step (c), the metal layer 30 is embedded in the groove portion 11 of the interlayer insulating film 10, and the barrier over the interlayer insulating film 10 is provided above the raised portion 12. The layer 20 is exposed.

  According to the polishing method of the present embodiment, the first liquid containing a metal oxide dissolving agent, a metal anticorrosive, a metal oxide dissolution adjusting agent, and water as the polishing liquid in the two CMP steps (b) and (c). And the effect of improving the polishing rate and suppressing the dishing in each of the steps (b) and (c) by controlling the mixing ratio with the second liquid containing the metal oxidant. As a result, the polished surface of the substrate 300 obtained after the step (c) can be sufficiently flattened while maintaining the overall polishing rate at a sufficiently high level.

  Further, as described above, the first polishing liquid used in the step (b) and the second polishing liquid used in the step (c) are mixed with a common raw material liquid such as the first liquid and the second liquid. The polishing method is useful from the viewpoint of simplifying the polishing liquid preparation process and reducing raw material costs.

  The present invention is not limited to the above embodiment. In the above embodiment, an example in which the steps (b) and (c) are continuously performed is shown. However, if necessary, the surface to be polished may be cleaned between the step (b) and the step (c). A drying step or the like may be provided. Further, between the step (b) and the step (c), the polishing platen and the polishing cloth may be replaced, the processing load may be changed, and the apparatus for these operations may be stopped.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Examples 1 to 4, Comparative Examples 1 and 2]
(Preparation of polishing liquid)
First, 1.2% by weight of polyacrylic acid, 0.40% by weight of colloidal silica abrasive grains having an average particle size of 35 nm, 0.20% by weight of malic acid as a metal oxide solubilizer, and 0.20% by weight of succinic acid The above components are mixed so that benzotriazole is 0.20% by weight as a metal anticorrosive and pure water is the balance (that is, the total is 100% by weight), and the pH of the mixed solution is adjusted with ammonia. The liquid A (corresponding to the first liquid according to the present invention) was obtained. Moreover, hydrogen peroxide water (special grade reagent, 30% aqueous solution) was prepared as the second liquid according to the present invention. Next, in each of Examples 1 to 3 and Comparative Examples 1 and 2, A liquid and B liquid were mixed at a ratio shown in Table 1 to prepare two types of polishing liquids.

(substrate)
The following substrates 1 and 2 were prepared as substrates for polishing.
Substrate 1 (8-inch blanket silicon substrate without pattern): silicon substrate / interlayer insulating film (silicon dioxide, average film thickness 300 nm) / barrier layer (tantalum nitride, average film thickness 25 nm) / metal layer (copper, average film thickness 1. 5μm)
Substrate 2 (8-inch silicon substrate with a pattern): silicon substrate with a groove having a depth of 0.5 μm / interlayer insulating film (silicon dioxide, average film thickness 300 nm) / barrier layer (tantalum nitride, average film thickness 25 nm) / Metal layer (copper, average film thickness 850 nm).

The substrate 2 (8-inch silicon substrate with a pattern) was produced as follows. First, silicon dioxide (average film thickness: 500 nm) was formed as an interlayer insulating film on a silicon substrate by a CVD method. A step portion in which a groove portion (corresponding to a wiring metal portion) having a width of 100 μm and a depth of 500 nm and a raised portion (corresponding to an interlayer insulating portion) having a width of 100 μm were alternately formed by photolithography. Next, a tantalum nitride film (average film thickness: 25 nm) was formed as a barrier layer along the shape of the stepped portion on the surface of the interlayer insulating film by sputtering. Further, a copper film (average film thickness: 850 nm) was formed as a metal layer by plating so as to fill all the grooves on the tantalum nitride film.

(Evaluation of polishing speed and surface to be polished)
For each of the substrates 1 and 2, the polishing process I using the first polishing liquid and the polishing process II using the second polishing liquid were performed. In the polishing steps I and II, while supplying the polishing liquid I or the polishing liquid II to the polishing cloth of the polishing surface plate, the polishing surface plate and the substrate are relatively moved while the polishing cloth is pressed against the surface to be polished of the metal layer. The metal layer was polished by moving periodically. The polishing conditions in the polishing steps I and II are shown below. Further, in the polishing steps I and II, the polishing rate is obtained from the film thickness of the metal layer before and after polishing converted from the electrical resistance value and the polishing time, and the remaining step of the substrate 2 is obtained using a stylus type step gauge. It was.

  In the polishing step I, polishing is performed until the average Cu remaining film thickness of the raised portions 12 reaches 180 to 200 nm. In the polishing step II, polishing is performed until the tantalum nitride on the raised portions 12 of the interlayer insulating film is exposed on the entire surface of the wafer. Went. In Example 4, the polishing steps I and II were continuously polished without performing the film thickness measurement and the step difference measurement after the polishing step I.

(Polishing conditions)
Polishing pad: IC1010 (Rodel)
Polishing pressure:
Polishing step I: 14.0 kPa
Polishing process II: 7.0 kPa
Polishing platen rotation speed: 93rpm
Rotation speed of head with wafer mounted: 87rpm
Polishing liquid supply amount: 200 ml / min

  In Examples 1 to 3, where the polishing liquid II has a larger mixing ratio of the B liquid / A liquid than the polishing liquid I, the polishing process I shows a good polishing rate, while the substrate after the polishing process II. The surface to be polished exhibited good flatness. In Example 4 in which the polishing steps I and II were continuously polished, good flatness was similarly exhibited. On the other hand, in Comparative Example 1 in which the polishing liquids I and II have the same composition, the polishing rate was low in the polishing step I, and the polishing time of the pattern substrate was long. Further, in the case of Comparative Example 2 in which the polishing liquid II has a smaller mixing ratio of B liquid / A liquid than the polishing liquid I, the polishing speed in the polishing step I is reduced and the polishing time of the pattern substrate is increased. In the polishing step II, the flatness deteriorated.

It is process sectional drawing which shows typically suitable one Embodiment of the grinding | polishing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Interlayer insulation film, 11 ... Groove part, 12 ... Raised part, 13 ... Step part, 14 ... Surface, 20 ... Barrier layer, 30 ... Metal layer, 31 ... Step part, 32 ... Groove part, 33 ... Raised part, 100, 200, 300 ... substrate.

Claims (9)

An interlayer insulating film having a step portion defined by a raised portion and a groove portion adjacent to each other on one surface side, a barrier layer provided following the surface of the interlayer insulating film having the step portion, and the barrier layer A metal layer provided to cover the substrate, and a method for polishing a substrate,
A first liquid containing a metal oxide solubilizer, a metal anticorrosive, a metal oxide solubilizer, and water and a second liquid containing a metal oxidizer are mixed at a predetermined ratio. And first polishing the metal layer using the first polishing liquid so that the barrier layer is not exposed,
The second liquid is obtained by mixing the first liquid and the second liquid so that the ratio of the second liquid is larger than that of the first polishing liquid. Polishing the metal layer after the first step using a liquid to expose a portion of the barrier layer located above the raised portion of the interlayer insulating film;
A polishing method comprising:   The content ratio of the metal oxidant in the first polishing liquid is 0.5 to 15% by weight based on the total weight of the first polishing liquid. Polishing method.   The content ratio of the metal oxidizer in the second polishing liquid is 10 to 20% by weight based on the total weight of the second polishing liquid. Polishing method.   The content ratio of the metal oxide solubilizer in the first polishing liquid is 0.001 to 10% by weight based on the total weight of the first polishing liquid. 4. The polishing method according to any one of 3 above.   The content ratio of the metal oxide solubilizer in the second polishing liquid is 0.001 to 10% by weight based on the total weight of the second polishing liquid. 5. The polishing method according to any one of 4 above.   The said metal oxidizing agent is at least 1 sort (s) chosen from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water, The any one of Claims 1-5 characterized by the above-mentioned. Polishing method.   The polishing method according to claim 1, wherein the metal layer contains at least one selected from copper, a copper alloy, a copper oxide, and a copper alloy oxide. The metal layer before the first step has a step portion corresponding to the step portion of the interlayer insulating film, and in the first step, a step before and after polishing in the step portion of the metal layer is formed. The polishing method according to claim 1, wherein the metal layer is polished so as to satisfy a condition represented by the following formula (1).
0 ≦ S ₂ / S ₁ ≦ 0.2 (1)
[Equation (1), S ₁ is to be polished in the step portion of the metal layer step (unit: nm) indicates, S ₂ is after polishing in the step portion of the metal layer step (unit: nm) Indicates. ]   In each of the first step and the second step, the polishing is performed on the surface to be polished of the metal layer while supplying the first polishing liquid or the second polishing liquid to the polishing cloth of the polishing surface plate. The polishing method according to any one of claims 1 to 9, wherein the metal layer is polished by relatively moving the polishing platen and the substrate while pressing a cloth.

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