JP2007146158A - Polishing material for composite film and polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing material and a polishing method for composite films comprising a magnetic metal membrane and an insulating material film and able to carry out a CMP treatment without generating defects such as scratches and the like on the magnetic metal membrane. <P>SOLUTION: The polishing material for composite films comprises water, abrasive grains, a monovalent organic acid and an anticorrosive agent and has 1.5-4 pH. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an abrasive for a composite material film and a polishing method, and more particularly, to a composite material film used in a chemical mechanical polishing (CMP) process suitable for manufacturing a thin film magnetic head for a hard disk drive (HDD). The present invention relates to a polishing material for polishing and a polishing method using the same.

  The recording capacity of HDD is increasing year by year. This increase in recording capacity is achieved by miniaturizing the recording area of the magnetic media to be recorded. In order to miniaturize the recording area of the magnetic medium, it is necessary to reduce the size of the recording element portion and the reproducing element portion of the magnetic head that performs recording and reproduction. In addition, in order to improve the decrease in reproduction output sensitivity due to the miniaturization of the recording area, the structure of the magnetic head is changed from an inductive head that combines recording and reproduction using electromagnetic induction to a reproducing head that uses the magnetoresistive effect and electromagnetic induction. Has shifted to a composite type thin film magnetic head (MR head) composed of a recording head using a magnetic head.

  The MR head is manufactured by sequentially forming a reproducing head on a ceramic substrate such as AlTiC (AlTiC) and a recording head thereon. The reproducing head includes a lower shield film made of a magnetic metal such as permalloy, a magnetoresistive effect element made of a laminated film of metals, and an upper shield film made of magnetic metal such as permalloy, and is formed by a thin film process. In manufacturing the MR head, CMP is applied for the purpose of eliminating the surface roughness of the base material and the purpose of eliminating the level difference generated in the processing process. The application of CMP is disclosed in Patent Document 1 and Patent Document 2, for example.

  The lower shield layer is formed by forming an insulating material film on a substrate, forming a magnetic metal film as a magnetic shield layer on the substrate in a predetermined shape, and then forming an insulating material film made of a metal oxide such as alumina. Then, the insulating material film and the magnetic metal film are polished by CMP so that the magnetic metal film is exposed. A method for forming the lower shield layer is disclosed in Patent Document 3, for example.

  However, in these conventional CMP processes, while maintaining a practical polishing rate, the magnetic metal film is polished smoothly without causing defects such as scratches and without causing a step between the magnetic metal film and the insulating material film. It was difficult. Defects such as scratches affect the sensitivity characteristics of the magnetoresistive effect element formed on the top, and the step between the magnetic metal film and the insulating material film causes a short circuit when forming the upper element. There was a problem that would decrease.

For this reason, the CMP process is divided into two stages, a first-stage rough polishing process that performs high-speed polishing and a second-stage final polishing process that performs low-speed polishing that does not cause defects on the polished surface. A method for achieving both reductions is effective.
JP-A-5-81613 JP-A-7-272211 JP 2000-109816 A

  The present invention relates to an abrasive for composite material film and a polishing method capable of smooth polishing with a small step between the magnetic metal film and the insulating material film without causing defects such as scratches and corrosion on the polished surface of the composite material film. In particular, the present invention provides a composite film abrasive and a polishing method that are useful in a final polishing process that enables an improvement in product yield.

  The present invention relates to (1) an abrasive for composite film, comprising water, abrasive grains, a monovalent organic acid, and an anticorrosive, and having a pH of 1.5 or more and 4 or less.

  The present invention also relates to (2) the abrasive for composite film according to (1), wherein the abrasive grains are alumina having a size of 10 nm to 1000 nm.

  The present invention also relates to (3) the abrasive for composite film according to (1), wherein the monovalent organic acid is hydroxymonocarboxylic acid.

  The present invention also relates to (4) the abrasive for composite film according to (3), wherein the hydroxymonocarboxylic acid is at least one selected from glycolic acid or lactic acid.

  The present invention also relates to (5) the composite film abrasive according to (1), wherein the anticorrosive agent is at least one selected from benzotriazole or a derivative thereof.

  The present invention also relates to (6) the composite material film abrasive according to (1), wherein the composite material film includes a magnetic metal film and an insulating material film.

  In addition, the present invention relates to (7) the abrasive for composite film according to any one of (1) to (6), which contains a nonionic water-soluble polymer.

  Moreover, this invention grind | polishes the composite material film containing a magnetic metal film and an insulating material film using the abrasive for composite material films as described in any one of (8) said (1)-(7). The present invention relates to a polishing method characterized in that at least a part of a magnetic metal film and an insulating material film is removed by the step of.

  The abrasive for composite material film and the polishing method of the present invention do not cause defects such as corrosion and scratches on the polished surface of the composite material film, and smooth polishing with a small step between the magnetic metal film and the insulating material film is possible. Therefore, it is particularly effective in the finish polishing process, and the product yield can be improved.

  The abrasive for composite film of the present invention contains water, abrasive grains, monovalent organic acid and anticorrosive, and has a pH of 1.5 or more and 4 or less.

  The abrasive grains in the present invention may be any of inorganic abrasive grains such as silica, alumina, zirconia, ceria, titania, and silicon carbide. Among these, alumina is preferable, and fine particle manufacturing technology has been established. Further, α-alumina or γ-alumina from which fine particles are easily available is more preferable. As a method for producing α-alumina or γ-alumina, a method by calcining aluminum hydroxide or a method by calcining boehmite purified by hydrolysis of aluminum alkoxide is known. These abrasive grains may be used alone or in combination of a plurality of kinds. For example, α-alumina or γ-alumina is mixed with hydrous alumina such as boehmite, silica, zirconia or the like. Also good. The average particle size of the abrasive grains is preferably 10 nm or more and 1000 nm or less, more preferably 30 nm or more and 300 nm or less, and the shape of the abrasive grains is preferably spherical in that scratches on the polished surface are easily reduced.

  The blending amount of the abrasive grains in the present invention is preferably 0.3% by mass or more and 10% by mass or less, and more preferably 0.3% by mass or more and 5% by mass or less with respect to the total weight of the abrasive. When the blending amount of the abrasive grains is less than 0.3% by mass, the polishing rate tends to be small because the physical grinding action is small, and when it exceeds 10% by mass, the polishing rate is saturated and more. Even when added, the polishing rate tends not to increase.

  The monovalent organic acid in the present invention is an organic compound having one carboxyl group in the molecule, and examples thereof include organic acids such as formic acid, acetic acid, propionic acid, butyric acid, glycolic acid, lactic acid, oxybutyric acid, and glyceric acid. Among these, hydroxy monocarboxylic acid is preferable in that polishing rate by CMP is large, aggregation and settling of abrasive grains can be suppressed, and defects on the polished surface such as scratches can be easily reduced, and glycolic acid or lactic acid is preferable. More preferred. Such monovalent organic acids may be used singly or in combination, for example, a mixture of glycolic acid and lactic acid, a mixture of glycolic acid or lactic acid and other monovalent organic acids. There may be. In the present invention, it is characterized by using a monovalent organic acid, and compared with the case where a divalent or higher organic acid is used, the dispersion stability of the abrasive grains is excellent, and the aggregation / sedimentation of the abrasive grains is less likely to occur. Polishing surface defects such as scratches can be reduced. This is because abrasive grains are generally positively charged on the acidic side at pH 4 or lower, and when a polyvalent anion is present, the charge is neutralized and aggregates and settles easily, whereas the phenomenon of salting out tends to occur. This is considered to be because this phenomenon is much less likely to occur with a valent anion.

  The blending amount of the organic acid in the present invention is preferably 0.1% by mass or more and 5.0% by mass or less, and 0.2% by mass or more and 3.0% by mass or less with respect to the total weight of the abrasive. Is more preferable.

  The anticorrosive agent in the present invention is, for example, benzotriazole (BTA), BTA derivative, for example, one in which one hydrogen atom of the benzene ring of BTA is substituted with a methyl group (tolyltriazole) or one substituted with a carboxyl group (benzotriazole) -4-carboxylic acid and benzotriazole-4-carboxylic acid methyl, ethyl, propyl, butyl and octyl esters), triazole, quinaldic acid, anthonylic acid, salicylaldoxime and the like. Among these, BTA or a derivative thereof or a mixture thereof is preferable. Such anticorrosives may be used alone or in combination of two or more. The present invention is characterized by the use of an anticorrosive agent, whereby a smooth polished surface free from defects such as corrosion and having a small step between the magnetic metal film and the insulating material film can be obtained.

  The blending amount of the anticorrosive agent in the present invention is preferably 0.05% by mass or more and 1% by mass or less, more preferably 0.1% by mass or more and 0.5% by mass or less, based on the total weight of the abrasive. preferable. When the amount of the anticorrosive 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 be slow.

  The abrasive of the present invention is one in which abrasive grains are dispersed in water in a slurry form. The blending amount of water is the remainder with respect to the total amount of various components other than water.

  The pH of the abrasive for composite film of the present invention is 1.5 or more and 4 or less, preferably 2 or more and 3 or less. By setting the pH within the above range, the surface roughness of the polishing surface can be reduced, and a constant polishing rate can be ensured. If the pH is less than 1.5, the surface roughness of the polishing surface becomes large. If the pH exceeds 4, the polishing rate by CMP becomes slow, and efficient polishing cannot be performed. Examples of the method of adjusting the pH of the abrasive to the above range include a method of adjusting the amount of the monovalent organic acid added, a method of using an alkaline component such as ammonia, sodium hydroxide, tetramethylammonium hydroxide, and the like. It is done.

  The abrasive of the present invention preferably contains a nonionic water-soluble polymer. Nonionic water-soluble polymers include, for example, polymers having vinyl group monomers such as polyvinyl alcohol and polyvinylpyrrolidone as basic structural units, celluloses such as methylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyethylene oxide, Examples include polyethylene oxide-polypropylene oxide copolymer. The nonionic water-soluble polymer preferably has a weight average molecular weight of 2,000 or more and 100,000 or less. In the present invention, by adding a nonionic water-soluble polymer, the surface roughness of the polished surface can be reduced and the cleaning performance after polishing can be improved.

  The blending amount of the nonionic water-soluble polymer in the present invention is preferably 0.01% by mass or more and 2.0% by mass or less, and 0.05% by mass or more and 0.0% by mass or less based on the total weight of the abrasive. More preferably, it is 5 mass% or less. When the blending amount of the nonionic water-soluble polymer is less than 0.01% by mass, the effect of reducing the surface roughness of the polished surface and the effect of improving the cleanability after polishing tend not to be recognized. If it exceeds 2.0 mass%, the polishing rate by CMP tends to decrease.

  The abrasive material of the present invention thus obtained is useful as an abrasive material for a composite material film including a magnetic metal film and an insulating material film, and is particularly suitable for being used for polishing in an element formation process of a composite magnetic head. Yes. The material to be polished is a composite material film including a magnetic metal film and an insulating material film, and each of these films may be a single layer or a stacked layer. Examples of magnetic metal films include Fe-Ni alloys (Permalloy), Co-Fe-Ni alloys, Fe-Al alloys, Fe-Al-Si alloys, Fe-Si-Co alloys, Fe-Al -Ge-based alloys, Fe-Ga-Ge-based alloys, Fe-Si-Ge-based alloys, Fe-Co-Si-Al-based alloys and other ferromagnetic metal materials, or Fe-Ga-Si-based alloys, and the above Fe -In order to further improve the corrosion resistance and wear resistance of the Ga-Si alloy, Fe, Ga, Co, (including those in which part of Fe is replaced with Co), and Si are used as the basic composition. Examples include alloys added with at least one of Ti, Cr, Mn, Zr, Nb, Mo, Ta, W, Ru, Os, Rh, Ir, Re, Ni, Pb, Pt, Hf, and V. Among these, Fe-Ni alloys are used for prizes. Examples of the insulating material film include metal oxides such as alumina, silica, and titania. Among these, alumina is awarded. In the abrasive for composite material film of the present invention, the polishing rate for the magnetic metal film and the polishing rate for the insulating material film are the same or close to each other. Therefore, there is a step between the magnetic metal film and the insulating material film on the polishing surface. A small and smooth polished surface can be obtained.

  The polishing method of the present invention comprises a step of polishing a composite material film including a magnetic metal film and an insulating material film using the composite material film polishing material of the present invention, and a part of the magnetic metal film and the insulating material film. It is characterized by removing. Such a polishing method of the present invention can be applied to flattening the lower shield layer of the reproducing head in the MR head. For the lower shield layer, for example, a composite material film made of NiFe (magnetic metal film) and alumina (insulating material film) forming a magnetic circuit is used so that the magnetic metal film whose surface is covered with the insulating material film is exposed. Further, the insulating material film and the magnetic metal film of the composite material film are polished by CMP. By polishing using the polishing material of the present invention, a polished surface with a small step between the exposed insulating material film and the magnetic metal film can be obtained, and the surface can be flat and small in surface roughness.

  A specific polishing method is that a substrate having a surface to be polished is pressed against a polishing cloth (pad) of a polishing surface plate, and the polishing surface plate and the substrate are moved relative to each other while the polishing material is supplied. A method of polishing the surface is mentioned. In addition, a method of bringing a metal or resin brush into contact and a method of spraying an abrasive with a predetermined pressure can be mentioned.

  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. 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. Further, it is preferable that the polishing cloth is grooved so that the abrasive is accumulated.

  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.

  In order to move the polishing cloth and the film to be polished relatively with the polishing film on the substrate pressed against the polishing cloth, specifically, at least one of the substrate and the polishing surface plate may be moved. In addition to rotating the polishing surface plate, polishing may be performed by rotating or swinging the holder. Further, a polishing method in which the polishing platen is rotated on a planetary surface, a polishing method in which a belt-like polishing cloth is moved linearly in one direction in the longitudinal direction, and the like can be given. The holder may be in any state of being fixed, rotating and swinging. These polishing methods can be appropriately selected depending on the surface to be polished and the polishing apparatus as long as the polishing cloth and the film to be polished are moved relatively.

  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 a spin dryer 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.

  Polishing is terminated when the pattern of the magnetic metal film is exposed. In order to ensure better flatness at the end of polishing, overpolishing (for example, the time until a desired pattern is obtained is 100 seconds. In this case, polishing for an additional 50 seconds in addition to the polishing for 100 seconds may be referred to as over-polishing 50%), and may be polished to a depth including a part of the magnetic metal film. The polishing surface of the composite material film obtained by the polishing method using the polishing material of the present invention has a small step between the insulating material film and the magnetic metal film, and the preferable step is 100 nm or less. Further, the surface roughness of the polished surface is small, and the preferable surface roughness is Ra (arithmetic average roughness) of 0.3 nm or less.

  The abrasive for composite material film of the present invention is used not only for polishing the composite material film of MR head as described above, but also for polishing the composite material film in the process of forming a metal wiring layer in a semiconductor device. Can do.

  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 magnetic metal film and insulating material film composite material)
A γ-alumina powder having a purity of 99.9% by weight was suspended in pure water and subjected to ultrasonic dispersion. Next, coarse particles were removed by classification to prepare an α-alumina suspension having an average particle size of 0.15 μm and a concentration of 10% by weight. 10 parts by mass of this α-alumina suspension, 1 part by mass of glycolic acid, 0.2 part by mass of benzotriazole and 88.8 parts by mass of water were added and dissolved to prepare an abrasive (A). The pH of the abrasive (A) was 2.4.

  While dropping the abrasive (A) onto a pad attached to a surface plate, CMP treatment was performed under the evaluation substrate and polishing conditions shown below, and the following evaluation was performed.

(Evaluation board)
Substrate 1: A blanket substrate in which an alumina film having a thickness of 3 μm is formed on an Altic substrate.

  Substrate 2: A blanket substrate in which permalloy (80% Ni-20Fe) having a thickness of 2 μm is formed on an Altic substrate.

  Substrate 3: A substrate in which an alumina film having a thickness of 3 μm is formed on a 100 μm × 100 μm, 2 μm thick permalloy film pattern, 2 parts by mass of α-alumina having an average particle size of 0.5 μm, and 1 mass of aluminum nitrate nonahydrate. A patterned substrate which is polished for 10 minutes with a roughing abrasive consisting of 90 parts by mass of water and polished to a thickness of 1 μm for the permalloy film and 1.05 μm for the alumina film. The step between the permalloy film and the alumina film of the substrate 3 is 50 nm, and the surface roughness Ra (arithmetic average roughness) is 1 nm.

(Polishing conditions)
Polishing device: Surface plate size 380 mmφ, rotary type Polishing pad: Polyurethane resin with closed cells Polishing pressure: 20 kPa
Relative speed between substrate and polishing surface plate: 36 m / min
Abrasive flow rate: 50 ml / min
Polishing time: 3 minutes (Evaluation items and evaluation method)
Alumina film polishing rate by CMP: The film thickness difference between before and after the CMP process of the substrate 1 was obtained with an optical film thickness measuring device and calculated from the polishing time.

  Permalloy film polishing rate by CMP: The film thickness difference of the substrate 2 before and after the CMP process was calculated from the change in sheet resistance, and calculated from the polishing time.

  Step height between alumina film and permalloy film: The step difference between the alumina film and the permalloy film after the CMP treatment of the substrate 3 was evaluated with a stylus type step gauge.

  Surface roughness Ra (arithmetic mean roughness): The surface roughness of the permalloy film after polishing of the substrate 3 was measured with an AFM (atomic force microscope).

  As a result of the evaluation, the polishing rate of the alumina film was 30 nm / min, the polishing rate of the permalloy film was 30 nm / min, the step difference between the alumina film / permalloy film was 50 nm, and the surface roughness was 0.18 nm in Ra.

Example 2
An abrasive (B) was produced in the same manner as in Example 1 except that 1 part by weight of glycolic acid was changed to 1 part by weight of lactic acid. The pH of the abrasive (B) was 2.5. Using the abrasive (B), a CMP treatment was performed in the same manner as in Example 1 for evaluation. As a result of the evaluation, the polishing rate of the alumina film was 30 nm / min, the polishing rate of the permalloy film was 25 nm / min, the step difference between the alumina film / permalloy film was 30 nm, the surface roughness was Ra of 0.15 nm, and the permalloy film Although the polishing rate was slightly reduced, the same result as in Example 1 was obtained.

Example 3
Further, an abrasive (C) was produced in the same manner as in Example 1 except that 0.1 part by mass of polyvinylpyrrolidone having a weight average molecular weight of 30,000 was added. The pH of the abrasive (C) was 2.4. 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 alumina film was 25 nm / min, the polishing rate of the permalloy film was 25 nm / min, the step difference between the alumina film / permalloy film was 50 nm, the surface roughness was 0.11 nm in Ra, and polyvinylpyrrolidone was The surface roughness was improved by the addition.

Comparative Example 1
An abrasive (D) was produced in the same manner as in Example 1 except that glycolic acid was not added. The pH of the abrasive (D) was 6.2. Using the abrasive (D), CMP treatment was performed in the same manner as in Example 1 for evaluation. As a result of the evaluation, the polishing rate of the alumina film was 10 nm / min, the polishing rate of the permalloy film was 10 nm / min, the step difference between the alumina film / permalloy film was 50 nm, and the surface roughness was 0.85 nm in Ra. As compared with the above, the polishing rate of the alumina film and the polishing rate of the permalloy film were decreased, and the surface roughness was deteriorated.

Comparative Example 2
An abrasive (E) was produced in the same manner as in Example 1 except that benzotriazole was not added. The pH of the abrasive (E) was 2.4. 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 alumina film was 30 nm / min, the polishing rate of the permalloy film was 90 nm / min, the step amount between the alumina film / permalloy film was 150 nm, and the surface roughness was 0.45 nm in Ra. In comparison with the above, the polishing rate of the permalloy film was greatly reduced, the level difference between the alumina film and the permalloy film was increased, and the surface roughness was also deteriorated.

Claims (8)

  A polishing material for composite film, comprising water, abrasive grains, a monovalent organic acid, and an anticorrosive agent, and having a pH of 1.5 or more and 4 or less.   The abrasive for composite film according to claim 1, wherein the abrasive is alumina having an average particle size of 10 nm or more and 1000 nm or less.   The abrasive for composite film according to claim 1, wherein the monovalent organic acid is hydroxymonocarboxylic acid.   4. The abrasive for composite film according to claim 3, wherein the hydroxy monocarboxylic acid is at least one selected from glycolic acid or lactic acid.   2. The abrasive for composite material film according to claim 1, wherein the anticorrosive is at least one selected from benzotriazole or a derivative thereof.   The composite material film abrasive according to claim 1, wherein the composite material film includes a magnetic metal film and an insulating material film.   The abrasive for composite material films according to any one of claims 1 to 6, comprising a nonionic water-soluble polymer.   By using the composite material film abrasive according to any one of claims 1 to 7 to polish the composite material film including the magnetic metal film and the insulating material film, the magnetic metal film and the insulating material film A polishing method comprising removing at least a part.