JP2000135673A - Polishing end point detecting method and polishing end point detecting device of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more actually detect a polishing end point in fidelity to a polishing state of a wafer by deciding time when physical quantity based on the iron ion concentration in abrasive slurry reaches physical quantity of an iron ion in an abrasive slurry waste liquid as a polishing end point. SOLUTION: A hydrogen peroxide aqueous solution 23 is supplied to a pipe 19d by a pump 18d to be mixed with an abrasive slurry waste liquid, a reagent and a buffer by a mixing part 21c to be formed as a specimen liquid. When this passes through into a cell 26 of a detecting apparatus, a visible beam is applied to calculate the iron ion concentration in the waste liquid from an analytical curve. A calculated value is transmitted to a RAM connected to a CPU of a CMP polishing device by an electric signal to be compared with a value of the iron ion concentration in the best polising time abrasive slurry waste liquid previously inputted to a ROM. When values of both coincide with each other, a polishing finish command is outputted from the CPU to finish CMP polishing of a semiconductor wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permalloy containing iron, for example, Ni-based metal, on a surface of a substrate such as silicon, alumina-titanium carbide (AlTiC) alloy, glass or the like.
Fe, Mn-Fe, Co-Fe, Ni-Rh-Fe, C
An o-Zr-Fe, Co-Fe-B-based permalloy magnetic layer is formed, and wiring of Cu, Ag, Au, or the like is provided as necessary.
Further, the wafer provided with an insulating layer of aluminum oxide or the like is attached to a chuck, pressed against a platen on which a polishing cloth is stuck, and the platen and the wafer are rotated while the abrasive slurry is supplied to the platen to polish the insulating layer. A method for detecting the end point of the chemical mechanical polishing (CMP) until the permalloy layer is exposed, or a method in which a wafer is vacuum-adsorbed to a chuck table and a polishing cloth is applied from the upper surface side of the wafer. Pressing the attached platen, supplying abrasive slurry to the platen or supplying abrasive slurry to the upper surface of the wafer, rotating the platen and wafer to polish the insulating layer until the permalloy layer is exposed Chemical mechanical polishing (CM
The present invention relates to a method for detecting a polishing end point when performing P) and a polishing end point detecting device used for the method.

[0002]

2. Description of the Related Art For example, as shown in FIG. 2, a magnetic head base is formed by forming a permalloy layer 3 on a substrate 2 and further forming an aluminum insulating layer on a wafer 1 (FIG. 2a) by chemical mechanical processing. Polishing is performed until the permalloy layer is exposed by polishing (FIG. 2D). At this time, the permalloy layer may be a plurality of layers of 2 to 10 layers.

[0003] In the polishing of these wafers, the appearance of automatic polishing without human intervention has been demanded from the market, and various CMP automatic polishing apparatuses for automatically detecting the polishing end point have been proposed.
As a method of detecting the end point of polishing, a method of measuring the thickness of a wafer being polished with a thickness gauge and determining the end point from the polishing amount (Japanese Patent Application Laid-Open No. 62-257742,
JP-A-9-193003, JP-A-10-106984
No. JP-A-10-98016). Methods for determining the end point from changes in the load current, voltage, and resistance of the platen during polishing and the motor of the chuck mechanism (JP-A-61-188702, JP-A-6-252112, JP-A-8-99625, JP-A-9-70753, JP-A-10-44035, JP-A-10-128658 and JP-A-10-128658
0-177977 etc.).

A method of determining the polishing end point from a change in the motor torque of the platen and chuck mechanism during polishing (JP-A-5-138529, JP-A-6-216095, JP-A-8-16095)
No. 139060, No. 8-197417, No. 9-360
No. 73, No. 9-262743, No. 10-256209
No.). A method of irradiating laser light on a wafer being polished and determining a polishing end point from its reflectance (Japanese Patent Laid-Open No. 57-138575)
No. 61-214970, JP-A-4-255218
Nos. 5-309559, 7-328916, 9-7985, 10-160420, etc.). In addition, phosphorus (P) which is an index in the abrasive slurry,
A method of determining the polishing end point by adding tracer particles and measuring the amounts of these indices on a polishing cloth (Japanese Patent Laid-Open No. 2-241)
No. 017, No. 8-69987), a method of observing the wafer surface using a differential interference microscope and determining the polishing end point (Japanese Patent Application Laid-Open Nos. 5-234971, 5-226203) and the like have been proposed.

The measurement of the thickness of the wafer is performed by measuring the thickness of a part of the wafer, and it takes a long time to measure the thickness distribution of the entire wafer. Since the method of determining from the current, voltage, resistance or torque does not directly observe the polished surface of the wafer, the reliability of the flattening accuracy is low similarly to the above.
In the above-mentioned method using laser light, the laser light is directly irradiated on the wafer, and the end point is determined by the amount of the reflected light.
It is necessary to irradiate light, and it is necessary to provide a space through which laser light can pass on the platen of the automatic polishing apparatus, which complicates the polishing apparatus. It is not clear how the addition of the index indicates the effect on the polishing of the wafer and the effect on the post-processing after the CMP polishing, and it is difficult to adopt it.

[0006]

The present inventors have paid attention to the iron contained in the permalloy layer, and iron mixed into the abrasive slurry waste liquid together with the insulating material as polishing dust becomes trivalent ions. And a physical quantity (Io) based on the iron ion concentration in the abrasive slurry at the time when a wafer showing the best polished state is obtained, such as colorimetry, light transmission, ionic current, and magnetic current , Magnetic field resistance, ion conductivity, etc., and the physical quantity (Ie) of iron ions in the abrasive slurry waste liquid during polishing, and the point in time at which the value of Ie reaches Io is determined as the polishing end point. It has been found that the polishing end point detection that is more faithful to the polishing state of the wafer can be determined more practically than the method.

[0007]

According to a first aspect of the present invention, a permalloy layer containing iron is formed on a substrate, and the insulating layer of the wafer on which the insulating layer is formed is chemically and mechanically polished. In CMP polishing for exposing the permalloy layer, the physical quantity of trivalent iron ions in the abrasive slurry waste liquid is measured, and the physical quantity (Ie) is input in advance, and the polishing is performed at the polishing end point where the best CMP polishing is performed. When the value of the physical quantity (Io) of trivalent iron ions in the agent slurry waste liquid reaches the value of the CM of the wafer,
An object of the present invention is to provide a method for detecting a polishing end point, wherein the polishing end point is a P polishing end point.

A second aspect of the present invention is to provide a polishing slurry in which the physical quantity of iron ions in the polishing slurry is such that a coloring agent and a hydrogen peroxide solution are added to the polishing slurry in the presence of iron ions, and the coloring slurry is formed. Abrasive slurry from reflectance or absorbance of-is performed by calculating the iron ion content in the waste liquid,
A polishing end point detecting method according to claim 1 is provided. Claim 3 of the present invention is that the reagent which develops color in the presence of iron ions is N, N-dialkyl-p-phenylenediamine (provided that the alkyl group has 1 to 2 carbon atoms). 2. A method for detecting a polishing end point according to item 2.

According to a fourth aspect of the present invention, in the abrasive slurry waste liquid, an aqueous buffer solution is further added in addition to the reagent and the hydrogen peroxide solution.
And a method for detecting a polishing end point described in (1). According to a fifth aspect of the present invention, the physical quantity of the iron ion is determined by the abrasive slurry.
The method for detecting the end point of polishing according to claim 4, wherein the calibration is performed by using a peak of absorbance at a wavelength of 500 to 570 nanometers (nm) measured at a pH of the waste liquid of 5 to 7. is there.

According to a sixth aspect of the present invention, there is provided an abrasive slurry used for CMP polishing, wherein (a) the average particle diameter is 0.05 to 1 μm.
(b) inorganic salts selected from water-soluble inorganic aluminum salts and nickel salts 0.1 to 3% by weight
2. The method according to claim 1, wherein the slurry is an aqueous abrasive slurry containing 0.1 to 3% by weight of a water-soluble chelating agent (c). is there. Claim 7 of the present invention is that the water-soluble inorganic salt (b) in the abrasive slurry is selected from nitrates, hydrochlorides, sulfates, phosphates and thiosulfates of aluminum or nickel. Item 6 provides a polishing end point detection method according to Item 6.

According to an eighth aspect of the present invention, the abrasive grains (a) in the abrasive slurry are aluminum oxide, cerium oxide, single crystal diamond, polycrystalline diamond, silicon oxide, silicon carbide, chromium oxide, boehmite. And a method of detecting a polishing end point according to claim 6, wherein the method is a particle selected from glass powder. According to a ninth aspect of the present invention, a permalloy layer containing iron is formed on a substrate, and the insulating layer of the wafer on which the insulating layer is formed is chemically and mechanically polished to expose a flat permalloy layer. CMP
A polishing end point detection device installed in polishing,

A mechanism for continuously analyzing the slurry slurry waste liquid discharged from the polishing apparatus and measuring the physical quantity of trivalent iron ions in the slurry slurry waste liquid, and a measured value (Ie) of the physical quantity; A mechanism for comparing the previously input best CMP amount with the physical quantity (Io) of trivalent iron ions in the polishing slurry slurry waste liquid at the polishing end point, and the measured value (Ie)
Is the physical quantity (I) of trivalent iron ions in the polishing slurry waste liquid at the polishing end point where the best CMP polishing has been performed in advance.
An object of the present invention is to provide a polishing end point detecting device having a mechanism for issuing a signal when the value reaches o) and a mechanism for instructing the end of CMP polishing of a wafer based on the signal.

[0013]

[Function] In addition to the abrasive slurry component, permalloy of polishing dust and debris of the insulating layer are added to the abrasive slurry waste liquid in accordance with the degree of polishing progress, and the waste liquid composition ratio changes every moment. I do. Therefore, the content (Io) of the specific substance in the polishing slurry waste liquid at the time of the best polishing is determined in advance by experiments, and the content (Ie) of the substance in the polishing slurry waste liquid during polishing is tracked (monitored). -), And when the content (Ie) of the specific substance coincides with the content (Io), the polishing end point was determined, so that the Permalloy area and the insulating material area ratio of the polished surface of the wafer were always constant. Then, polishing is completed. In particular, colorimetric analysis is an excellent detection method because even a very small amount of iron ions color the chromogenic reagent.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Wafer to be polished: The wafer to be polished according to the present invention is made of a permalloy containing iron on a surface of a substrate made of silicon, alumina / titanium carbide alloy, glass or the like.
i-Fe, Mn-Fe, Co-Fe, Ni-Rh-F
e, a wafer on which a Co-Zr-Fe, Co-Fe-B-based permalloy magnetic layer is formed, wiring of Cu, Ag, Au or the like is provided as necessary, and an insulating layer of aluminum oxide or the like is further provided.

Polishing apparatus: As the polishing apparatus 10, for example, the wafer 1 is vacuumed on a chuck table 14 shown in FIG.
The platen 15 on which the polishing cloth 15a is adhered is pressed from the upper surface side of the wafer, and the platen and the wafer are rotated while the slurry 13 is supplied to the platen or the slurry is supplied to the upper surface of the wafer. CMP for polishing
The apparatus 1 or the wafer 1 shown in FIGS. 4, 5 and 6 is mounted on a chuck 11 and pressed against a platen 12 to which a polishing cloth 12a is attached, and while supplying an abrasive slurry 13 to the platen, the platen and the semiconductor wafer A mechanical mechanical polishing (CMP) apparatus for polishing a wafer by rotating a wafer, or a CMP apparatus using a polishing tape instead of a platen.

Abrasive slurry: The components of the abrasive slurry used for CMP polishing vary depending on the composition, structure, and polishing amount of the object to be polished. For example, (a) the average particle size is 0.05 to 1
0.1 to 10% by weight of abrasive grains having a particle diameter of 0.1 μm, and (b) an inorganic salt selected from water-soluble inorganic aluminum salts and nickel salts.
Aqueous abrasive slurries containing 0.1% to 3% by weight and (c) a water-soluble chelating agent can be used. As abrasive grains, aluminum oxide, cerium oxide, single crystal diamond, polycrystalline diamond, silicon oxide, silicon carbide,
Chromium oxide and glass powder, and these abrasive grains have an average particle diameter of 0.1 to 1.0 μm, preferably 0.3 to 1.0 μm.
0.5 μm particles.

The content of the abrasive grains of the component (a) in the abrasive slurry varies depending on the type and use of the abrasive grains.
It is from 0.05 to 10% by weight, preferably from 0.1 to 3% by weight. If it is less than 0.05% by weight, a practical polishing rate cannot be obtained. Even if it exceeds 10% by weight, further improvement of the effect cannot be expected,
Many uses are economically disadvantageous. The water-soluble aluminum or nickel inorganic salt of the component (b) acts to improve the polishing rate. Examples of the component (b) include aluminum or nickel nitrate, hydrochloride, sulfate, phosphate, and thiosulfate. Specifically, aluminum nitrate, nickel nitrate, aluminum sulfate and the like. The water-soluble inorganic salt of the component (b) is an abrasive slurry.
Medium, it is used in an amount of 0.1 to 3% by weight. The water-soluble chelating agent (c) is added to the slurry for the purpose of improving the polishing rate and improving the flatness of the obtained wafer. Examples of such water-soluble chelating agents include ethylenediaminetetraacetic acid (EDTA), disodium salt of ethylenediaminetetraacetic acid (EDTA-2), aminosulfonic acid-N, N-2 acetate alkali metal salt, 2,2- Examples thereof include an alkali metal salt of dimethylpropanebisoxamide, diethylenetriaminepentaacetic acid, and a sodium salt thereof. The chelating agent of the component (c) is an abrasive slurry.
Medium, it is used in an amount of 0.1 to 3% by weight.

The abrasive slurry includes an aqueous medium, an abrasive oil,
A rust inhibitor, a dispersing aid, a preservative, an antifoaming agent, a pH adjuster and the like are compounded. As a dispersion medium, water alone or water as a main component (70 to 99% by weight in the dispersion medium), and a water-soluble organic solvent such as alcohol or glycol as a subcomponent (1 to 30% by weight). Compounded ones can be used. Water is 0.1μ
Water as large as possible and free of macroparticles obtained by filtration through a m-cartridge filter is preferred. As alcohol,
Methyl alcohol, ethyl alcohol and isopropyl alcohol include glycols such as ethylene glycol, tetramethylene glycol and diethylene glycol.
Propylene glycol, polyethylene glycol,
And the like.

The content of the aqueous dispersion medium in the abrasive slurry is 70 to 99% by weight, preferably 90 to 99% by weight. If it is less than 70% by weight, the viscosity of the slurry becomes high, and the supply of the abrasive slurry onto the substrate and the storage stability of the slurry are poor. Examples of the polishing oil having the function of a polishing improver and a dispersant for abrasive grains include various surfactants, ethylene glycol, propylene glycol, and polyethylene glycol.
And polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, pronic nonionic surfactants (addition products of ethylene oxide and propylene oxide) and the like.

Examples of the surfactant include an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, a combination of an anionic surfactant and a nonionic surfactant, and an anionic surfactant. Use of a surfactant and an amphoteric surfactant Combination of a cationic surfactant and a nonionic surfactant, and use of a combination of a cationic surfactant and an amphoteric surfactant. The type of the surfactant greatly contributes to the dispersibility of the abrasive grains and the polishing rate. Examples of anionic surfactants include metal soaps such as sodium palmitate, sodium stearate, calcium oleate, aluminum stearate, and sodium / potassium palmitate; alkyl polyoxyethylene ether carboxylate, alkyl phenyl poly Oxyethylene-
Tercarboxylate, sulfated fatty acid alkyl ester, monoacylglycerol sulfate, secondary alkane sulfonate, N-acyl-N-methyltauric acid, sodium dodecylbenzenesulfonate, alkyl ethereal phosphate, alkylpolyphosphate Oxyethylene salt, alkylphenyl phosphate polyoxyethylene salt, sodium naphthalene sulfonate
And perfluoroalkyl phosphates, sulfonic acid-modified silicone oils and the like.

Among these, metal soaps, sulfone-type anionic surfactants having a HLB of 5 or more, phosphate ester-type anionic surfactants, fluorine-based or chlorine-based anionic surfactants, and combinations of two or more thereof Is preferred. The anionic surfactant is used in the slurry in an amount of from 0.05 to
2% by weight is used. If it is less than 0.05% by weight, the dispersibility of the particles is poor, and the particles tend to settle. Even if it exceeds 2% by weight, it is not expected to further improve the effects of the dispersibility and the polishing rate, and it is preferable that the effect is small in terms of wastewater treatment.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, pronic nonionic surfactant (addition reaction product of ethylene oxide and propylene oxide), fatty acid polyoxy Examples include ethylene esters, fatty acid polyoxyethylene sorbitan esters, polyoxyethylene castor oil, fatty acid sucrose esters, polyoxyethylene / oxypropylene alkyl ethers, and the like. Specific examples include polyethylene glycol dilaurate, tridecyl polyoxyethylene ether, nonylphenyl polyoxyethylene ether, and polyethylene glycol monostearate. Preferably, compounds having an HLB of 10 or more are preferred. The nonionic surfactant is used in an amount of 0.1 to 10% by weight.

Examples of the amphoteric surfactant include N-alkylsulfobetaine-modified silicone oil, N-alkylnitrilotriacetic acid, N-alkyldimethylbetaine, α-trimethylammonio fatty acid, N-alkylβ-aminopropionic acid, and N-alkyl. β-iminodipropionate,
N-alkyloxymethyl-N, N-diethylbetaine, 2-alkylimidazoline derivatives, N-alkylsulfobetaine and the like. When the anionic surfactant and the nonionic surfactant or the amphoteric surfactant are used in combination, 0.1 to 5 parts by weight of the nonionic surfactant or the amphoteric surfactant is added to 1 part by weight of the anionic surfactant. Parts. The combined use improves the storage stability of the slurry.

The content of the nonionic surfactant or amphoteric surfactant in the abrasive slurry is 0.1 to 10%.
%, Preferably 0.1 to 5% by weight. If the amount is less than 0.1% by weight, the storage stability of the abrasive slurry is not improved. If it exceeds 10% by weight, no further improvement in dispersibility can be expected. Examples of the dispersing aid include sodium hexametaphosphate, oleic acid, and monobasic calcium phosphate. pH
Potassium hydroxide, sodium hydroxide,
Examples include morpholine and aqueous ammonia. Examples of the rust preventive include nitrogen-containing organic compounds such as alkanolamine / alkanolamine boric acid condensate, monoethanolamine, diethanolamine, triethanolamine, alkanolamine borate, and benzisothiazolines. As antifoaming agents, liquid paraffin, dimethyl silicone oil, monostearic acid, di-glyceride mixture,
And sorbitan monopalmitiate.

Measurement of iron ion physical quantity: abrasive slurry
The measurement of the physical quantity of iron ions in the waste liquid may be any of colorimetry, laser light, visible light, ultraviolet light reflectance, X-ray fluorescence analysis, conductivity titration, etc., but the measuring equipment is inexpensive and It is preferable to use a colorimetric analysis method that requires only a small amount of the sample solution and can measure a continuously flowing sample solution. In the colorimetric method, a reagent that develops a color in the presence of iron ions is added to the discharged slurry slurry containing iron ions, and if necessary, an oxidizing agent and a buffer are added to form a color. And the height of the absorption peak at a specific wavelength of the compound in which the reagent has developed color due to the iron ion is measured. From the value of the height of the absorption peak, the iron ion content is determined using a calibration curve. Calculate the amount. In other words, iron ions act as a catalyst, and the higher the concentration, the faster the color-forming reaction proceeds, and the higher the spectral density of the color-forming solution.Therefore, a calibration curve of the iron ion concentration and the absorbance of the color-forming solution is created in advance. The correlation is digitized and input to the CPU.

Reagents that develop color in the presence of iron ions include N, N-dimethyl-p-phenylenediamine, N, N
N-diethyl-p-phenylenediamine, o-phenanthroline, thiocyan potassium, sodium thiocyanate and the like can be mentioned. Among them, N, N with good sensitivity to iron ions
-Dimethyl-p-phenylenediamine, N, N-diethyl-p-phenylenediamine are preferred. This N, N-
The color development of dimethyl-p-phenylenediamine is pH 5.
It is preferably 0 or more, preferably 5.5 to 7, and a buffer is added to the waste liquid. Examples of the buffer include a mixed aqueous solution of acetic acid and sodium acetate, a mixed aqueous solution of phosphoric acid and ammonium phosphate, and a mixed aqueous solution of sulfuric acid and ammonium sulfate.
Since the aqueous solution of N, N-dimethyl-p-phenylenediamine itself is easily oxidized by air, the pH is adjusted to an acidic range by adding an acid such as sulfuric acid or hydrochloric acid in advance, or the pH is adjusted to an acidic range by adding a buffer. It is preferable to keep it. Since the color development of N, N-dimethyl-p-phenylenediamine is due to oxidation, an oxidizing agent is added to perform the color development in a short time. As the oxidizing agent, aqueous hydrogen peroxide is inexpensive and easy to handle. The color development of N, N-dimethyl-p-phenylenediamine is represented by the following formula.

[0027]

Embedded image

Since two derivatives are generated by oxidation of the reagent, absorption peaks of visible light include an absorption peak near 514 nm and an absorption peak near 550 nm (see FIG. 1). As the polishing time elapses, the amount of iron acting as a catalyst increases, the reaction proceeds, the purple color of the waste liquid becomes deeper, and the height of the absorption peak increases as shown in FIGS. The colorimetric sample becomes darker as the oxidation reaction progresses from cloudy to pale pink, pale reddish purple, and deep purple.

FIG. 7 shows that in the presence of different concentrations of iron ions,
The reagent changes with time at pH 7.2 5
The correlation of the absorbance at a wavelength of 14 nm is shown. Therefore, when performing colorimetric analysis of the waste liquid and the mixture (specimen) of these reagents, buffer, and hydrogen peroxide, the peak height at time t, which is the sum of the preparation time of the specimen and the time required for the colorimetric analysis, is set. The arithmetic circuit of the CPU is programmed to read the iron ion concentration by fitting to a calibration curve showing the correlation between the iron ion concentration and the absorption height. In addition, the iron ion concentration I in the waste liquid in the optimal polishing state I
Enter the value of o into the ROM.

The input of the absorbance (Ie) at the end point of the optimum polishing may be directly inputted when the abrasive slurry used contains no iron ions (0.0000 ppm). When iron ions are contained in the new abrasive slurry to be used, the value of Ie may be directly input. However, preferably, the absorbance Ie1 of the new abrasive slurry and the absorbance Ie2 at the end point of the optimal polishing are measured. , Ie = Ie2-I
Input to the CPU as e1. FIG. 4 shows a polishing apparatus with the detector device mounted.

The abrasive slurry waste liquid 16 is collected by a centrifugal force of rotation of a platen or a chuck table in a gutter 17 provided at one end of the outer periphery thereof, supplied to a pipe 19a by a pump 18a, and supplied to a pipe 19b by a pump 18b. The supplied aqueous solution of the buffer 20 is mixed in the mixing section 21a to adjust the pH of the waste liquid to 5 or more, preferably 5.5 to 7.0, and then the aqueous solution 22 of the reagent is supplied to the pipe 1 by the pump 18c.
9c, and mixed with the waste liquid containing the buffer in the mixing section 21b.
The sample liquid 24 is supplied to the tube 19d at d, and mixed by the mixing unit 21c to form a sample liquid 24, which is heated to 40 to 80 degrees Celsius by the heaters 25 and 25, and then passes through the cell 26 of the detector. Is irradiated with visible light,
The concentration of iron ion in the waste liquid (I
e) is calculated from the calibration curve, and the calculated value is expressed as a CM in an electric signal.
The result is transmitted to the RAM connected to the CPU of the P polishing apparatus, and is compared with the value of the iron ion concentration (Io) in the abrasive slurry waste liquid at the time of the best polishing previously input to the ROM. A polishing end command is output from the CPU, and the CMP polishing of the semiconductor wafer is ended.

The colorimetric analysis utilizing the color development by oxidation of N, N-dimethyl-p-phenylenediamine is based on trivalent Co ion, Bi ion, M
It can also be used to detect the concentration of o and Mn ions, and can be calibrated at the same absorption wavelength peak.
Although the MP polishing end point can be detected, the coloring speed is slightly inferior to that of iron ions. The colorimetric analysis may be performed from the beginning of the polishing of the wafer, or may be started 30 to 5 seconds before the end of the polishing. However, when the above-mentioned abrasive slurry containing iron ions is used, and when the absolute value of Ie = Ie2-Ie1 is input, it is preferable to perform the colorimetric analysis from the beginning of the wafer polishing.

As an example of permalloy, there is a Ni-Fe system, and it is conceivable to perform colorimetric analysis of Ni ions by the dimethyl oxime method, but the sensitivity is N, N-dimethyl-p-.
It is less than 1/1000 of the colorimetric analysis method utilizing color development by oxidation of phenylenediamine.
When a chelating agent is contained therein, the measurement will vary, which is not practical. In this colorimetric analysis, as shown in FIG. 6, a colored part is irradiated with visible light from a visible light emitting tube 27 while a reagent is dropped on a platen, and the amount of reflected light is detected as a physical quantity (Ie) by a spectrometer 28. It is also possible. It is also possible to irradiate the platen 12 with fluorescent X-rays instead of visible light from the X-ray emission tube 27, and determine the polishing end point from the iron-based spectrum of the reflected fluorescent X-rays.

[0034]

The present invention will be described in more detail with reference to the following examples. Preparation of abrasive: 0.5 parts by weight of aluminum nitrate and 0.5 parts by weight of diethylenetriaminepentaacetic acid Na salt were added to water which passed through a 0.1 μm cartridge filter.
Dissolved in 5 parts by weight. 93.5 parts by weight of the above filtrate, 2.5 parts by weight of aluminum oxide particles having an average particle size of 0.5 μm, lauryl alcohol polyoxyethylene ether
1.0 part by weight and 2.0 parts by weight of polyethylene glycol (molecular weight: 200) were mixed with a homogenizer,
An abrasive slurry was prepared. After 5 days, the crystals which did not dissolve in water were removed from the aqueous solution by filtration. Filtrate 9
3.5 parts by weight, 2.5 parts by weight of aluminum oxide particles having an average particle size of 0.5 μm, 1.0 part by weight of lauryl alcohol polyoxyethylene ether and 2.0 parts of polyethylene glycol (molecular weight: 300) 2.0 The parts by weight were mixed with a homogenizer to prepare an abrasive slurry (Fe ion concentration: 0.0000 ppm).

Measurement of iron ion concentration at the time of best polishing: Ni (81.9) was placed on an aluminum / titanium carbide substrate.
Wt%)-Fe (18.1 wt%) Permalloy 300
A magnetic disk wafer on which a 0 nm layer is further provided with an aluminum oxide insulating layer by a sputtering method is mounted on a chuck mechanism so that the substrate surface is adsorbed, while a platen polishing cloth provided on the lower surface of the chuck mechanism The surface of the insulating layer of the semiconductor wafer is pressed against the surface while the abrasive slurry is dropped (pressure 400 g / c).
m2), the step between the permalloy and the insulating layer when polished for 3 minutes at a platen rotation speed of 45 rpm and a chuck mechanism rotation speed of 45 rpm is as small as 68 Å,
In addition, the respective surface roughness (R) of the permalloy layer and the insulating layer
a) was also as small as about 6 angstroms and was the best.

At this time, 1 cc of abrasive slurry waste liquid,
Buffer aqueous solution (acetic acid 0.2 mol and sodium acetate 0.2
Aqueous solution made by dissolving pure moles to 1 liter) 1c
c / min, colorimetric analysis using 1 wt% N, N-dimethyl-p-phenylenediamine aqueous solution 1 cc / min and 1 wt% hydrogen peroxide aqueous solution 1 cc / min (absorption wavelength 514 n
The trivalent iron ion concentration in the abrasive slurry waste liquid according to m) was 0.60 ppm. Also, the concentration of Ni metal in the abrasive slurry waste liquid analyzed by another method was 5.1 ppm.
Met.

Detection of polishing end point: Abrasive slurry being polished is supplied to a pipe 18a at a rate of 1 cc / min by a pump into a gutter 17 provided outside a platen 15 of the polishing apparatus 1 shown in FIG. Buffer aqueous solution, N, N-dimethyl-p-
An aqueous phenylenediamine solution and an aqueous hydrogen peroxide solution were also supplied to the tube at 1 cc / min, and colorimetric analysis of the trivalent iron ion concentration (Ie) in the abrasive slurry waste liquid was performed.
Trivalent iron ion concentration (I
In o), the absorbance at a wavelength of 514 nm corresponding to 0.60 ppm was input.

The time when the value of Ie coincided with Io was defined as the polishing end point. The surface roughness of the permalloy alloy of the polished wafer was measured with a surface roughness meter (trade name: ET30HK, manufactured by Komatsu Ltd.), measuring length 0.25 mm, stylus 0.5 μmR,
When measured with a load of 3 mg and a speed of 20 μm / sec, all were about 6 angstroms (Ra).
The surface of the permalloy alloy was measured by a surface defect analyzer using laser light, and the number of scratches having a width of 1 to 3 μm and a length of 20 μm or less was measured. As a result, no micro scratch was detected. .

[0039]

The method of detecting the end point of CMP of a wafer according to the present invention is equivalent to performing an analysis based on the composition of the permalloy layer of the polished wafer.
The polishing end point can be detected more precisely.

[Brief description of the drawings]

FIG. 1 is a correlation diagram between light wavelength obtained by colorimetry and absorbance.

FIG. 2 is a cross-sectional view showing a change over time in polishing of a wafer.

FIG. 3 is a sectional view showing an example of a CMP polishing apparatus.

FIG. 4 is a sectional view showing an example in which a polishing end point detector is attached to a CMP polishing apparatus.

FIG. 5 is a top view of the CMP polishing apparatus.

FIG. 6 is a top view of a CMP polishing apparatus provided with another detection mechanism.

FIG. 7 shows time and 514 under different iron ion concentrations.
It is a figure which shows the correlation of the light absorbency of nm wavelength.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wafer 3 Permalloy layer 4 Insulating layer 10 CMP polishing apparatus 13 Abrasive slurry 16 Abrasive slurry waste liquid 24 Sample liquid 26 Cell of detector

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Norio Hayashi 1000 Kamoshitacho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Chemical Corporation Yokohama Research Laboratory F-term (reference) 3C058 AA07 AC02 BA09 BB01 BB09 CB01 CB04 CB10 DA02 DA12 DA17

Claims (9)

[Claims] 1. A CM in which a permalloy layer containing iron is formed on a substrate, and the insulating layer of the wafer on which the insulating layer is formed is chemically and mechanically polished to expose a flat permalloy layer.
In P polishing, the physical quantity of trivalent iron ions in the abrasive slurry waste liquid was measured, and the physical quantity (Ie) was previously input. A polishing end point detecting method, wherein a point at which a value of a physical quantity (Io) of iron ions having a valence reaches a CMP polishing end point of a wafer is set. 2. The physical quantity of iron ions in the abrasive slurry is determined by adding a reagent and a hydrogen peroxide solution to the abrasive slurry in the presence of iron ions to obtain a reflectance or absorbance of the colored abrasive slurry. The polishing end point detecting method according to claim 1, wherein the method is performed by calculating the iron ion content in the abrasive slurry waste liquid from the following formula. 3. The polishing endpoint detection method according to claim 2, wherein the reagent is N, N-dialkyl-p-phenylenediamine (provided that the alkyl group has 1 to 2 carbon atoms). 4. The abrasive slurry waste liquid further comprises an aqueous buffer solution in addition to a reagent and a hydrogen peroxide solution that develop color in the presence of iron ions.
3. The polishing end point detection method described in 1. above. 5. The method according to claim 1, wherein a physical quantity of the iron ion is measured by a peak of an absorbance at a wavelength of 500 to 570 nanometers (nm) measured at a pH of the slurry slurry waste liquid of 5 to 7. The polishing end point detecting method according to claim 4. 6. An abrasive slurry used for CMP polishing.
However, (a) abrasive grains having an average particle size of 0.05 to 1 μm 0.1 to 0.1 μm
Aqueous polishing containing 10% by weight, (b) 0.1 to 3% by weight of an inorganic salt selected from a water-soluble inorganic aluminum salt and a nickel salt, and (c) 0.1 to 3% by weight of a water-soluble chelating agent. 2. An agent slurry.
3. The polishing end point detection method described in 1. above. 7. A water-soluble inorganic salt (b) in an abrasive slurry.
The polishing endpoint detection method according to claim 6, wherein is selected from nitrates, hydrochlorides, sulfates, phosphates, and thiosulfates of aluminum or nickel. 8. The abrasive grains (a) in the abrasive slurry are selected from aluminum oxide, cerium oxide, single crystal diamond, polycrystalline diamond, silicon oxide, silicon carbide, chromium oxide, boehmite and glass powder. The polishing end point detecting method according to claim 6, characterized in that the polishing end points are particles. 9. A CM in which a permalloy layer containing iron is formed on a substrate, and the insulating layer of the wafer on which the insulating layer is formed is chemically and mechanically polished to expose a flat permalloy layer.
A polishing end point detecting device installed in P polishing, a mechanism for continuously analyzing an abrasive slurry waste liquid discharged from the polishing device, and measuring a physical quantity of trivalent iron ions in the abrasive slurry waste liquid; The measured value (Ie) of the physical quantity and the best CM previously input
Abrasive slurry at polishing end point after P polishing-3 in waste liquid
A mechanism for comparing the physical quantity (Io) of the trivalent iron ions with the measured value (Ie); An apparatus for detecting a polishing end point, comprising: a mechanism for issuing a signal when the value of a physical quantity (Io) is reached; and a mechanism for instructing termination of CMP polishing of a wafer based on the signal.