JP2007150263A - Copper film, polishing material for copper film compound material and polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing material which exhibits high polishing speed of CMP and permits CMP treatment wherein the roughness of metal surface is low and a level difference is small between a metal film and an insulating resin film. <P>SOLUTION: The polishing material for metal is used to polish a surface to be polished having at least an organic insulating material and a copper or a copper alloy. In this case, it contains abrasive grains and an oxidant, its pH is 1.5-3.5, and a neutralization titration value is 0.05 mol/kg or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polishing material for a copper film and an insulating material film, and a polishing method, and more particularly to a polishing material used in a chemical mechanical polishing (hereinafter referred to as CMP) process suitable for forming a copper wiring of a high performance wiring board. The present invention relates to a polishing method using stencil.

  In order to improve the performance of LSIs, the use of copper alloy wiring as a wiring material is progressing instead of conventional aluminum alloy wiring. Since copper alloy wiring is difficult to be finely processed by the dry etching method frequently used in the formation of conventional aluminum alloy wiring, a copper alloy thin film is deposited and embedded on an insulating film in which grooves have been formed in advance. A so-called damascene method is mainly employed in which a copper alloy thin film other than the above is removed by CMP to form a buried wiring (Patent Document 1). A general method of metal CMP for polishing a metal film such as copper or copper alloy is to apply a polishing pad on a circular polishing platen (platen), immerse the polishing pad surface with a metal film polishing material, and The surface on which the metal film is formed is pressed, and the polishing platen is rotated with a predetermined pressure (hereinafter referred to as polishing pressure) applied from the back surface, and the convex portion is caused by mechanical friction between the abrasive and the convex portion of the metal film. The metal film is removed.

  The metal film abrasive used in the CMP process is generally composed of an oxidizing agent and abrasive grains. It is considered that the basic mechanism is to oxidize the surface of the metal film with an oxidizing agent and scrape the oxidized layer with abrasive grains. Since the oxide layer on the surface of the metal film in the concave portion does not touch the polishing pad so much and the effect of scraping off by the abrasive grains does not reach, the oxide layer in the convex portion is removed and the substrate surface is flattened as the CMP process proceeds. Further, if necessary, a metal oxide solubilizer such as an acid and a protective film forming agent for the metal film surface are added. Adding a metal oxide solubilizer can improve the polishing rate, and adding a protective film forming agent for the metal film surface also forms a protective film on the concave metal film surface, so a practical polishing rate can be achieved. Flatness can be ensured while maintaining (Patent Document 2).

In recent years, following the manufacture of LSI, the application of a CMP method capable of forming wiring with high accuracy is also being studied for high-performance and fine wiring boards such as packages. While the thickness of the metal film such as copper or copper alloy used in the manufacture of LSI is about 1 μm, the thickness of the metal film used for high performance and fine wiring plates is as thick as about 10 μm. When a conventional LSI polishing material having a speed of about 0.5 μm / min is used (Patent Document 3), there is a problem that the CMP process takes time and the productivity deteriorates.
JP-A-2-278822 JP-A-8-83780 JP 2003-124160 A

  The present invention makes it possible to polish copper and copper alloy films at a high polishing rate of 2 μm / min or more, and in a short time even in the manufacture of products that require polishing of thick copper films such as high-performance wiring boards. Therefore, the present invention provides an abrasive and a polishing method that can be polished and can ensure sufficient productivity.

  The present invention is (1) an abrasive containing water, abrasive grains, an oxidizing agent, an inorganic acid and an amino acid and having a pH of 1.5 or more and 3.5 or less, and the pH of the abrasive is increased to 4. The present invention relates to an abrasive for a copper film and an insulating material film, characterized in that the amount of potassium hydroxide required for the treatment is 0.05 mol or more per kg of the abrasive.

  The present invention also relates to (2) the abrasive for copper film and insulating material film according to (1), wherein the abrasive grains are colloidal silica having an average particle diameter of 100 nm or less.

  Moreover, this invention is (3) The copper film as described in said (1) characterized by the said oxidizing agent being at least 1 sort (s) of oxidizing agent chosen from hydrogen peroxide, persulfuric acid, or persulfate. The present invention relates to an insulating material film abrasive.

  The present invention also relates to (4) the abrasive for copper film and insulating material film according to (1), wherein the inorganic acid is sulfuric acid, phosphoric acid or a mixture thereof.

  In addition, the present invention provides: (5) The polishing material for copper film and insulating material film according to (1), wherein the amino acid has a first-stage acid dissociation index of 2 to 3 at 25 ° C. About.

  The present invention also relates to (6) a polishing agent for a copper film and an insulating material film according to any one of (1) to (5) above, which contains a protective film forming agent for the copper surface. .

  The present invention is also directed to (7) the copper film according to (6), wherein the protective film forming agent is at least one protective film forming agent selected from benzotriazole and derivatives thereof. The present invention relates to an insulating material film abrasive.

  Moreover, this invention relates to the abrasive | polishing material for copper films as described in any one of said (1)-(7) characterized by containing water-soluble polymer (8).

  In addition, the present invention provides (9) a substrate on which a copper film and an insulating material film are formed using the copper film and the insulating material film abrasive according to any one of (1) to (8). The present invention relates to a polishing method comprising polishing a film to be polished.

  As the abrasive of the present invention, a buffer solution having a pH of 1.5 to 3.5 can be obtained. For this reason, even if copper and a copper alloy, which are objects to be polished, are dissolved in the polishing material, pH fluctuation hardly occurs, and a high polishing rate can be maintained. The polishing material and polishing method of the present invention can suppress the surface roughness on the metal film with a high polishing rate, and can improve productivity and increase the product yield. Applicable to process.

  The abrasive for copper film and insulating material film of the present invention is an abrasive containing water, abrasive grains, oxidant, inorganic acid and amino acid, and having a pH of 1.5 or more and 3.5 or less. The amount of potassium hydroxide required to increase the pH of the material to 4 is 0.05 mol or more per kg of the abrasive.

  The pH of the polishing material for copper film and insulating material film of the present invention is pH 1.5 or more and 3.5 or less, pH 2 or more and pH 3 in that the polishing rate by CMP of the copper film is large and the copper film is not corroded. The following is preferred. If the pH is less than 1.5, the surface roughness of the copper film becomes large. If the pH exceeds 3.5, the polishing rate by CMP becomes slow and cannot be a practical abrasive. In the present invention, the pH of the abrasive is adjusted to the above range by appropriately selecting the blending amounts of inorganic acid and amino acid. Inorganic acids are generally strong acids, and when added in large amounts, the pH drops and it is difficult to adjust the pH to the desired range, but it is easy to adjust the pH to the desired range by adding amino acids. can do.

  In the abrasive for copper film and insulating material film of the present invention, the amount of potassium hydroxide required to increase the pH of the abrasive to 4 is 0.05 mol or more per kg of abrasive. If the amount of potassium hydroxide is less than 0.05 mol, the polishing rate will decrease. The method of setting the amount of potassium hydroxide to 0.05 mol or more per 1 kg of the abrasive is performed by appropriately selecting the blending amount of the inorganic acid to be added.

  During the CMP process, the copper film that is the object to be polished is polished and dissolved as copper ions in the polishing material. If the amount of the inorganic acid is small, hydrogen ions are consumed by dissolution of the copper film, the pH of the abrasive is increased, and the polishing rate is decreased. On the other hand, if the amount of the inorganic acid is sufficient, the abrasive has a pH buffering action, so even if a large amount of copper ions are dissolved, the increase in pH is suppressed, and stable polishing without decreasing the polishing rate. Is possible. The amount of inorganic acid in the polishing material required for that purpose increases the pH of the polishing material to 4 when polishing an 8-inch disk-shaped substrate, although it depends on the polishing rate and the polishing material flow rate during polishing. The amount of potassium hydroxide required for this is an amount corresponding to 0.05 mol or more per kg of the abrasive.

  The abrasive grains in the present invention may be any of inorganic abrasive grains such as silica, alumina, zirconia, ceria, titania and silicon carbide, and organic abrasive grains such as polystyrene, polyacryl and polyvinyl chloride, but dispersed in the abrasive. Colloidal silica and colloidal alumina having an average particle size of 100 nm or less are preferred, and colloidal silica having an average particle size of 100 nm or less is more preferred, since the stability is good and the number of polishing scratches (scratches) generated by CMP is small. 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.

  The blending amount of the abrasive grains in the present invention is preferably 0.1% by mass to 10% by mass, and more preferably 1% by mass to 5% by mass with respect to the total weight of the abrasive. When the blending amount of the abrasive grains is less than 0.1% by mass, the polishing rate tends to decrease because the physical grinding action is small, and when it exceeds 10% by mass, the polishing rate is saturated and beyond. Even when added, the polishing rate tends not to increase.

Examples of the oxidizing agent in the present invention include hydrogen peroxide (H ₂ O ₂ ), persulfates such as persulfuric acid, ammonium persulfate, and potassium persulfate, periodic acid, potassium periodate, and the like. Hydrogen oxide, persulfuric acid and persulfate are preferable, and hydrogen peroxide is more preferable.

  The blending amount of the oxidizing agent in the present invention is preferably 0.1 mol / kg to 5 mol / kg, and more preferably 0.5 mol / kg to 4 mol / kg with respect to the total weight of the abrasive. When the blending amount of the oxidizing agent is less than 0.1 mol / kg, the polishing rate tends to decrease, and when it exceeds 5 mol / kg, the polishing rate tends to decrease.

  Examples of the inorganic acid in the present invention include nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, phosphoric acid, etc. Among these, sulfuric acid or phosphoric acid or a mixture of sulfuric acid and phosphoric acid is a polishing rate by CMP. Is preferable in that the surface roughness of the copper and copper alloy films can be reduced.

  The blending amount of the inorganic acid in the present invention is such that the amount of potassium hydroxide required to increase the pH of the abrasive to 4 is 0.05 mol or more per 1 kg of the abrasive.

  Examples of amino acids in the present invention include glycine, alanine, valine, leucine, isoleucine, serine, threonine, cysteine, cystine, methionine, aspartic acid, glutamic acid, lysine, arginine, phenylalanine, tyrosine, histidine, tryptophan, proline, oxyproline and the like. Can be mentioned. Among these, the amino acid whose first-stage acid dissociation index (pK1) at 25 ° C. is 2 or more and 3 or less is easy to adjust the pH of the abrasive for the copper film and the insulating material film to 1.5 or more and 4 or less. This is preferable. Specifically, alanine, arginine, isoleucine, glycine, glutamic acid, tryptophan, threonine, valine, methionine, lysine, leucine, serine, tyrosine, phenylalanine and the like are preferable, and glycine is particularly preferable. The acid dissociation index (pKa) in the present invention is a logarithmic value of the reciprocal of the acid dissociation constant. For example, the “Chemical Handbook Basic Edition” revised 4th edition (issued on September 30, 1993), Maruzen Co., Ltd., II There are detailed descriptions on pages 317 to 321.

  The abrasive of the present invention preferably contains a protective film forming agent for the copper surface. The protective film forming agent is not particularly limited. For example, benzotriazole (BTA), BTA derivative, for example, one hydrogen atom of the benzene ring of BTA is substituted with a methyl group (tolyltriazole) or a carboxyl group is substituted. And the like (methyl, ethyl, propyl, butyl and octyl esters of benzotriazole-4-carboxylic acid and benzotriazole-4-carboxylic acid), triazole, quinaldic acid, anthonylic acid, salicylaldoxime and the like. Among these, BTA or a derivative thereof or a mixture thereof is preferable.

  The blending amount of the protective film forming agent in the present invention is preferably 0.05% by mass to 1% by mass, and preferably 0.1% by mass to 0.5% by mass with respect to the total weight of the abrasive. More preferred. When the blending amount of the protective film forming agent is less than 0.05% by mass, the surface roughness of the polishing surface tends to increase, and when it exceeds 1% by mass, the polishing rate tends to decrease.

  The abrasive of the present invention preferably contains a water-soluble polymer. The water-soluble polymer is not particularly limited, and examples thereof 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 and a salt thereof, a polymer having a monomer having a vinyl group such as polyvinyl alcohol and polyvinylpyrrolidone as a basic structural unit. Among these, polyacrylic acid or a salt thereof, and polymethacrylic acid or a salt thereof are preferable. These water-soluble polymers preferably have a weight average molecular weight of 500 or more. The addition of these water-soluble polymers tends to improve the polishing rate and flatness (step between the copper film / rim film dendrite).

  The blending amount of the water-soluble polymer in the present invention is preferably 0.01% by mass to 2.0% by mass, and 0.1% by mass to 1.0% by mass with respect to the total weight of the abrasive. It is more preferable. If the blending amount of the water-soluble polymer is less than 0.01% by mass, the effect of improving the polishing rate is hardly recognized, and if it exceeds 2.0% by mass, the dispersion stability of the abrasive tends to be lowered.

  The abrasive of the present invention is one in which abrasive grains are dispersed in water in a slurry form. The amount of water added is the remainder relative to the total amount of the various components described above.

  The polishing method of the present invention is characterized in that a substrate on which a film to be polished including a copper film and an insulating material film is formed is polished using the polishing material of the present invention. The target films to be polished are a copper film and an insulating material film, and each of these films may be a single layer or a stacked layer. The copper film is copper or a copper alloy. The copper film is formed by a known method such as sputtering or plating.

  As the substrate, a substrate related to semiconductor device manufacture, for example, a substrate in which an insulating layer is formed on a semiconductor substrate such as a semiconductor substrate in which a circuit element and a wiring pattern are formed, a semiconductor substrate in a stage in which a circuit element is formed, etc. Etc.

  Polishing of the film to be polished is performed by chemical mechanical polishing. Specifically, the polishing material of the present invention is supplied in a state where the substrate on which the surface to be polished is formed is pressed onto the polishing cloth (pad) of the polishing surface plate. The surface to be polished is polished by relatively moving the polishing platen and the substrate. In addition, there are a method in which a metal or resin brush is brought into contact with the surface to be polished, and a method in which an abrasive is sprayed at a predetermined pressure.

  As an apparatus for polishing, for example, when polishing with a polishing cloth, a general apparatus having a holder that can hold a substrate to be polished and a surface plate that is connected to a motor that can change the number of rotations and to which the polishing cloth is attached. A polishing apparatus can be used. For example, a polishing apparatus manufactured by Ebara Corporation: model number EPO111 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 pressing pressure of the substrate having the surface to be polished on the polishing cloth (polishing pressure) is preferably 1 to 100 kPa, and in order to satisfy the uniformity of the polishing surface within the CMP rate and the flatness of the pattern, 5 to More preferably, it is 50 kPa.

  During polishing, the abrasive 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 pad is always covered with an abrasive.

  The substrate after polishing is preferably washed in running water and then dried after removing water droplets adhering to the substrate using spin drying or the like. In order to perform CMP with the surface state of the polishing cloth always the same, it is preferable to perform a conditioning process of the polishing cloth before polishing. For example, the polishing cloth is conditioned with a liquid containing at least water using a dresser with diamond particles. Subsequently, it is preferable to perform a CMP polishing process according to the present invention, and further add a substrate cleaning process.

  Hereinafter, the present invention will be described by way of examples. The present invention is not limited by these examples.

Example 1
(Method for producing abrasive for copper and copper alloy)
A solution of 646.9 g of water in 0.05 mol of sulfuric acid (5.1 g of 96% sulfuric acid), 25 g of glycine, 3 g of benzotriazole and 20 g of colloidal silica having an average particle size of 70 nm was dissolved in hydrogen peroxide (special grade, 30 % Aqueous solution) 300 g was added to produce a copper film and an insulating material film abrasive (A).

  Colloidal silica was prepared by hydrolysis of tetraethoxysilane in an ammonia solution according to a conventional method.

  The pH of the abrasive (A) was 2.6. The amount of potassium hydroxide required to increase the pH of the abrasive (A) to 4 was 0.09 mol / kg per kg of the abrasive (A).

  While dripping the above-mentioned abrasive (A) onto a pad attached to a surface plate, the following substrate was used, CMP treatment was performed under the following polishing conditions, and the following evaluation was performed.

(Evaluation board)
Substrate 1: A blanket substrate having a diameter (φ) of 8 inches in which a copper film having a thickness of 18 μm is formed on a glass epoxy substrate.

  Substrate 2: A striped pattern having a depth of 5 μm and a groove width of 100 μm is formed on a glass epoxy substrate using a photosensitive permanent resist, and then a copper plating seed layer having a thickness of 0.2 μm is formed by sputtering. Subsequently, a pattern forming substrate having a diameter (φ) of 8 inches, in which a copper film having a thickness of 10 μm is formed by plating.

(Polishing conditions)
Polishing device: Surface plate size 600mmφ, Rotary type Polishing pad: Polyurethane resin with closed cells Polishing pressure: 35kPa
Relative speed between substrate and polishing surface plate: 70 m / min
Abrasive flow rate: 200ml / min
(Evaluation items and evaluation methods)
Copper polishing rate by CMP: The film thickness difference between before and after the CMP treatment of the substrate 1 was calculated from the sheet resistance change, and calculated from the polishing time.

  Surface roughness (arithmetic mean roughness Ra): The surface roughness of the copper film after the CMP treatment of the substrate 1 was measured with an AFM (atomic force microscope).

  Step difference between copper film / rim film dendrite: The step difference between the copper film / edge film dendrite after the CMP process of the substrate 2 was evaluated with a stylus type step meter.

  As a result of the evaluation, the polishing rate of the copper film was 2.2 μm / min, the surface roughness Ra was 2.7 nm, and the step between the copper film / rim film dendritic film was 0.35 μm.

(Example 2)
0.02 mol of phosphoric acid (2.3 g of phosphoric acid at a concentration of 85%) was further added, and the operation was performed in the same manner as in Example 1 except that the amount of water added was 644.6 g. An abrasive (B) was produced.

  The pH of the abrasive (B) was 2.5. The amount of potassium hydroxide required to increase the pH of the abrasive (B) to 4 was 0.11 mol / kg per kg of the abrasive (B).

  CMP was performed in the same manner as in Example 1 using the abrasive (B), and evaluation was performed. As a result of the evaluation, the polishing rate of the copper film was 2.7 μm / min, the surface roughness was 1.3 nm in Ra, and the step difference between the copper film / rim film dendritic film was 0.28 μm. And the step between the copper film / rim film dendritic membrane was improved.

(Example 3)
A polishing material (C) for a copper film and an insulating material film was prepared in the same manner as in Example 2 except that 5 g of polyacrylic acid having a weight average molecular weight of 20,000 was further added and the amount of water added was 639.6 g. did.

  The pH of the abrasive (C) was 2.5. The amount of potassium hydroxide required to increase the pH of the abrasive (C) to 4 was 0.12 mol / kg per kg of the abrasive (C).

  CMP was performed in the same manner as in Example 1 using the abrasive (C), and evaluation was performed. As a result of the evaluation, the polishing rate of the copper film was 2.9 μm / min, the surface roughness was 1.1 nm in terms of Ra, and the step difference between the copper film / rim film dendritic film was 0.19 μm. And the step between the copper film / rim film dendritic membrane was improved.

(Comparative Example 1)
A polishing material (D) for a copper film and an insulating material film was produced in the same manner as in Example 1 except that glycine was not added and the amount of water added was 664.6 g.

  The pH of the abrasive (D) was 1.2. Further, the amount of potassium hydroxide required to increase the pH of the abrasive (D) to 4 was 0.09 mol / kg per 1 kg of the abrasive (D).

  CMP was performed in the same manner as in Example 1 using the abrasive (D), and evaluation was performed. As a result of the evaluation, the polishing rate of the copper film was 2.1 μm / min, the surface roughness was 35.6 nm in Ra, and the step between the copper film / rim film dendritic film was 1.2 μm. Although not, the surface roughness and the step between the copper film / rim film dendrite decreased.

(Comparative Example 2)
A polishing material (E) for copper film and insulating material film was produced in the same manner as in Example 1 except that the addition amount of sulfuric acid was 0.01 mol (1.02 g of sulfuric acid having a concentration of 96%).

  The pH of the abrasive (E) was 3.3. The amount of potassium hydroxide required to increase the pH of the abrasive (E) to 4 was 0.018 mol / kg per kg of the abrasive (E).

  CMP was performed in the same manner as in Example 1 using the abrasive (E), and evaluation was performed. As a result of the evaluation, the polishing rate of the copper film was 0.8 μm / min, the surface roughness was 2.1 nm in Ra, and the step difference between the copper film / rim film dendritic film was 0.3 μm, and the polishing rate was greatly reduced. .

Claims (9)

  A polishing material containing water, abrasive grains, an oxidizing agent, an inorganic acid and an amino acid and having a pH of 1.5 or more and 3.5 or less, which is required for increasing the pH of the polishing material to 4. A polishing material for a copper film and an insulating material film, wherein the amount of is 0.05 mol or more per 1 kg of the polishing material.   The abrasive for copper film and insulating material film according to claim 1, wherein the abrasive grains are colloidal silica having an average particle diameter of 100 nm or less.   2. The polishing material for a copper film and an insulating material film according to claim 1, wherein the oxidizing agent is at least one oxidizing agent selected from hydrogen peroxide, persulfuric acid or persulfate.   2. The abrasive for copper film and insulating material film according to claim 1, wherein the inorganic acid is sulfuric acid, phosphoric acid or a mixture thereof.   The abrasive for copper film and insulating material film according to claim 1, wherein the first-stage acid dissociation index of said amino acid at 25 ° C is 2 or more and 3 or less.   It contains the protective film formation agent with respect to a copper surface, The abrasive | polishing material for copper films and insulation material films as described in any one of Claims 1-5 characterized by the above-mentioned.   7. The abrasive for copper film and insulating material film according to claim 6, wherein the protective film forming agent is at least one protective film forming agent selected from benzotriazole and derivatives thereof.   The water-soluble polymer is contained, The abrasive | polishing material for copper films and insulation material films | membranes as described in any one of Claims 1-7 characterized by the above-mentioned.   A substrate on which a film to be polished including a copper film and an insulating material film is formed is polished using the copper film and the insulating material film abrasive according to any one of claims 1 to 8. Polishing method.