JP2002203819A - Cmp abrasive and method for polishing substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CMP abrasive capable of accurately determining the polishing end point of a polished surface of a substrate and a method for polishing the substrate capable of accurately determining the polishing end point of the polished surface of the substrate, which provides high planarity. SOLUTION: This CMP abrasive of cerium oxide comprises slurry where the torque of rotation axis of a polishing surface plate at polishing end is 1.2-2 times at polishing start and the torque becomes greatest 10-30 seconds before the polishing end. In this method for polishing the substrate, the substrate on which a polished film has been formed is pressed onto a polishing cloth of the polishing surface plate and is pressurized, and while supplying the CMP abrasive between the polishing film and the polishing cloth, the polished film is polished by rotating the substrate and the polishing surface plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMP polishing agent used in a flattening process of a substrate surface, which is a semiconductor device manufacturing technology, in particular, a flattening process of an interlayer insulating film, a forming process of shallow trench isolation, and the like. The present invention relates to a method for polishing a substrate using these CMP abrasives.

[0002]

2. Description of the Related Art At present, ultra-large-scale integrated circuits tend to increase the packing density, and various microfabrication techniques have been studied and developed. Already, design rules are on the order of sub-half microns. One of the technologies that have been developed to satisfy such strict requirements for miniaturization is a CMP (Chemical Mechanical Polishing) technology. This technology completely flattens the layer to be exposed in the semiconductor device manufacturing process, reducing the burden of the exposure technology,
Since the yield can be stabilized, the technique is indispensable when performing, for example, planarization of an interlayer insulating film, isolation of a shallow trench, and the like.

Conventionally, in a semiconductor device manufacturing process, an inorganic insulating film layer such as a silicon oxide insulating film formed by a method such as plasma-CVD (Chemical Vapor Deposition) or low-pressure-CVD is used to flatten. Fumed silica-based abrasives have been generally studied as CMP abrasives. The fumed silica-based abrasive is produced by subjecting silica particles to particle growth by a method such as thermal decomposition to tetrachlorosilicic acid and adjusting the pH. However, such a polishing agent does not have a sufficient polishing rate for the inorganic insulating film, and there has been a technical problem of a low polishing rate for practical use.

In the conventional CMP technique for flattening an interlayer insulating film, the polishing rate largely depends on the pattern of a film to be polished on a substrate, and the polishing rate of a convex portion differs greatly depending on the pattern density difference or size difference. Since the polishing of the concave portion also proceeds, there has been a technical problem that a high level of planarization cannot be realized over the entire wafer surface.

In the CMP technique for flattening an interlayer film, it is necessary to finish polishing in the middle of the interlayer film, and a process management method for controlling a polishing amount by a polishing time is generally performed. However, there has been a problem that not only the change in the pattern step shape but also the state of the polishing cloth significantly changes the polishing rate, making process management difficult.

In the generation of the design rule of 0.5 μm or more, LOCOS (local silicon oxidation) has been used for element isolation in an integrated circuit. After that, when the processing dimensions are further reduced, the technology for narrowing the element separation width is required,
Trench isolation is being used. In the shallow trench isolation, CMP is used to remove an excess silicon oxide film formed on the substrate, and a stopper film having a low polishing rate is formed below the silicon oxide film to stop polishing.
Silicon nitride or the like is used for the stopper film, and it is desirable that the polishing rate ratio between the silicon oxide film and the stopper film is large.

The conventional fumed silica-based abrasive has a polishing rate ratio of the silicon oxide film and the stopper film as small as about 3 and does not have characteristics that can be practically used for shallow trench isolation. As a means for determining whether or not polishing has been completed, there is a method of measuring the torque of the polishing platen.
This method utilizes the fact that the torque changes depending on the polishing amount and the polishing film, but has a problem that accuracy is not good.

On the other hand, cerium oxide abrasives have been used as abrasives for glass surfaces such as photomasks and lenses. Cerium oxide particles have a lower hardness than silica particles and alumina particles and are therefore less likely to scratch the polished surface, and thus are useful for finish mirror polishing. However, since a cerium oxide abrasive for polishing a glass surface uses a dispersant containing a sodium salt, it cannot be directly used as an abrasive for semiconductors.

[0009]

SUMMARY OF THE INVENTION The invention according to claims 1 to 3 provides a CMP polishing agent which can be highly flattened and which can accurately determine the end point of polishing of a polished surface of a substrate. . A fourth aspect of the present invention provides a substrate polishing method capable of accurately determining an end point of polishing of a polished surface of a substrate.

[0010]

According to the present invention, the torque of the polishing platen rotating shaft at the end of polishing is 1.2 to 2 times that at the start of polishing, and the torque is increased 10 to 30 seconds before the end of polishing. It relates to a cerium oxide CMP polishing slurry consisting of a slurry which is maximized.

[0011] The present invention also relates to the above-mentioned CMP polishing slurry comprising a cerium oxide slurry containing cerium oxide particles, a dispersant and water and an additive liquid containing a polymer additive and water. Further, the present invention provides the above CMP wherein the dispersant and the polymer additive are at least one compound selected from a water-soluble organic polymer, a water-soluble anionic surfactant, and a water-soluble nonionic surfactant. For abrasives.

Further, in the present invention, the substrate on which a film to be polished is formed is pressed against a polishing cloth of a polishing platen and pressurized.
The present invention relates to a substrate polishing method for polishing a film to be polished by rotating a substrate and a polishing plate while supplying an abrasive between a polishing film and a polishing cloth.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The cerium oxide CMP abrasive of the present invention has a polishing platen rotating shaft torque at the end of polishing 1.2 to 2 times that at the start of polishing and 10 to 30 seconds at the end of polishing. Previously consisted of a slurry that maximized torque. The torque of the polishing platen rotating shaft can be obtained by measuring a motor current for driving the polishing platen at the time of polishing with the CMP polishing slurry of the present invention, or by measuring a distortion amount of the polishing platen rotating shaft. During polishing, friction occurs between the polishing particles and the film to be polished, and the torque increases. When the polishing proceeds and the film to be polished becomes a flat surface without irregularities, the torque decreases.

In the present invention, the torque has a maximum value of 10 to 10.
The end point of polishing can be easily determined by measuring the torque after 30 seconds as the polishing end point, and high flatness can be achieved. Here, when the torque does not show the maximum value (for example, it increases monotonically and eventually becomes saturated), the end point of polishing cannot be easily determined, so that the workability, the yield, and the high flatness are poor. I can't achieve it. Further, when the torque of the polishing platen rotating shaft at the end of polishing is out of the range of 1.2 to 2 times that at the start of polishing, the process margin is too small, resulting in poor workability, and high flatness cannot be achieved. In some cases, polishing scratches occur.

[0015] The torque characteristics of the cerium oxide CMP abrasive within the above-mentioned range include the cerium oxide particles (particle size and particle size distribution), the type and amount of the added agent, and the pH of the cerium oxide CMP abrasive. And by adjusting the solid content concentration and the like.

The cerium oxide in the present invention is a carbonate,
It is obtained by oxidizing cerium compounds of nitrates, sulfates and oxalates. A cerium oxide abrasive used for polishing a silicon oxide film formed by a TEOS-CVD method or the like can be polished at a high speed as the primary particle diameter is large and the crystal distortion is small, that is, the crystallinity is good. Polishing scratches tend to occur. Therefore, the cerium oxide particles used in the present invention are not limited to a method for producing the cerium oxide particles.
It is preferably not more than nm. Further, since it is used for polishing a semiconductor chip, the content of alkali metals and halogens is preferably suppressed to 10 ppm or less in cerium oxide particles.

In the present invention, as a method for producing cerium oxide powder, calcination or an oxidation method using hydrogen peroxide or the like can be used. The firing temperature is preferably from 350 to 900C.
Since the cerium oxide particles produced by the above method are agglomerated, it is preferable to mechanically pulverize the particles. As the pulverization method, a dry pulverization method using a jet mill or the like or a wet pulverization method using a planetary bead mill or the like is preferable. The jet mill is described in, for example, Chemical Industry Transactions, Vol. 6, No. 5, (1980), pp. 527-532.

In the present invention, for example, the CMP abrasive is
It is obtained by dispersing a composition comprising cerium oxide particles having the above characteristics, a dispersant and water, and further adding a polymer additive. Here, the concentration of the cerium oxide particles is not limited, but is preferably 0.5% because of easy handling of the dispersion.
The range of -20% by weight is preferred. Also, as a dispersant,
Since it is used for polishing semiconductor elements, the content of alkali metals such as sodium ions and potassium ions and halogens and sulfur is preferably suppressed to 10 ppm or less,
For example, a polymer dispersant containing ammonium acrylate as a copolymer component is preferable. In addition, as a polymer additive, a polymer additive containing ammonium acrylate and at least one selected from a water-soluble anionic surfactant, a water-soluble nonionic surfactant, and a water-soluble amine are used. Is preferred.

Examples of the water-soluble anionic dispersant include triethanolamine lauryl sulfate, ammonium lauryl sulfate, polyoxyethylene alkyl ether triethanolamine sulfate, special polycarboxylic acid type polymer dispersants, and the like. Examples of the nonionic dispersant include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octyl phenyl ether, polyoxyethylene Ethylene nonyl phenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivative, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan Nopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbate tetraoleate, polyethylene glycol monolaurate, polyethylene glycol mono Examples include stearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, polyvinylpyrrolidone, and alkyl alkanolamide.

The amount of the dispersant added is determined based on the dispersibility of the particles in the slurry and the prevention of sedimentation.
The range is preferably from 0.01 part by weight to 2.0 parts by weight.

The amount of the polymer additive is preferably in the range of 1 to 1000 parts by weight based on 100 parts by weight of the cerium oxide particles. The weight average molecular weight of the dispersant and the polymer additive is preferably from 100 to 50,000,
1,000 to 10,000 is more preferred.

The molecular weight of the dispersant and the polymer additive is 100
If the molecular weight of the dispersant and the polymer additive exceeds 50,000, the viscosity becomes high when the silicon oxide film or the silicon nitride film is polished. This is because the storage stability of the CMP abrasive decreases. The weight average molecular weight is a value measured by gel permeation chromatography and converted to standard polystyrene.

As a method for dispersing these cerium oxide particles in water, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like can be used in addition to a usual dispersion treatment using a stirrer.

The average particle size of the cerium oxide particles in the thus prepared CMP abrasive is 0.01 μm to 1.0 μm.
It is preferred that If the average particle size of the cerium oxide particles is less than 0.01 μm, the polishing rate is too low,
If the thickness exceeds 1.0 μm, the film to be polished is easily damaged.

When a cerium oxide slurry composed of cerium oxide particles, a dispersant, and water and an additive solution composed of a polymer additive and water are stored as a separate CMP abrasive, the cerium oxide particles do not agglomerate. Is increased, and the generation of polishing scratches can be prevented, and the polishing rate can be stabilized. When polishing a substrate with the above-mentioned CMP abrasive, the additive liquid is supplied separately to the polishing platen and the cerium oxide slurry, and mixed on the polishing platen, or mixed with the cerium oxide slurry immediately before polishing. The method of supplying on a surface plate is taken.

As a method of forming an inorganic insulating film using the CMP polishing slurry of the present invention, low pressure CVD, plasma CVD, etc.
And the like. In forming a silicon oxide film by low-pressure CVD, monosilane: SiH _{4 is} used as a Si source, and oxygen: O ₂ is used as an oxygen source. This SiH ₄ —O ₂ -based oxidation reaction
It is obtained by performing at a low temperature of 00 ° C. or less. In some cases, heat treatment is performed at a temperature of 1000 ° C. or lower after CVD. When doping phosphorus: P for planarizing the surface by high temperature reflow, SiH ₄ —O ₂ −
It is preferable to use a PH ₃ based reaction gas.

The plasma CVD method has an advantage that a chemical reaction requiring a high temperature can be performed at a low temperature under normal thermal equilibrium. There are two types of plasma generation methods, capacitive coupling type and inductive coupling type.
One is. As a reaction gas, Si is used as a Si source.
H _4, SiH ₄ -N ₂ O-based gas and TEOS-O ₂ based gas using tetraethoxysilane (TEOS) to Si source using N ₂ O as oxygen source (TEOS-plasma CVD method)
Is mentioned. The substrate temperature is preferably in the range of 250 ° C. to 400 ° C., and the reaction pressure is preferably in the range of 67 to 400 Pa.

As described above, the silicon oxide film of the present invention may be doped with an element such as phosphorus and boron. Similarly, in forming a silicon nitride film by low-pressure CVD, dichlorosilane: SiH ₂ Cl ₂ is used as a Si source, and ammonia: NH ₃ is used as a nitrogen source. This is obtained by performing the SiH ₂ Cl ₂ —NH ₃ based oxidation reaction at a high temperature of 900 ° C.
In the plasma CVD method, a SiH ₄ —NH ₃ gas using SiH ₄ as a Si source and NH ₃ as a nitrogen source is used as a reaction gas. The substrate temperature is preferably from 300C to 400C.

As a substrate, a silicon oxide film layer or a silicon nitride film layer is formed on a semiconductor substrate such as a semiconductor substrate in which circuit elements and wiring patterns are formed, and a semiconductor substrate in which circuit elements are formed. Substrate can be used. By polishing the silicon oxide film layer or the silicon nitride film layer formed on such a semiconductor substrate with the above-mentioned CMP polishing agent, the unevenness on the surface of the silicon oxide film layer is eliminated,
A smooth surface can be provided over the entire surface of the semiconductor substrate. It can also be used for shallow trench isolation.

For use in shallow trench isolation, it is preferable that the ratio of the polishing rate of the silicon oxide film to the polishing rate of the silicon nitride film, that is, the polishing rate of the silicon oxide film / the polishing rate of the silicon nitride film is 10 or more. If this ratio is less than 10, the difference between the polishing rate of the silicon oxide film and the polishing rate of the silicon nitride film is small, and it tends to be difficult to stop polishing at a predetermined position when performing shallow trench isolation. When this ratio is 10 or more, the polishing rate of the silicon nitride film is further reduced, and the polishing can be easily stopped, which is more suitable for shallow trench isolation. Further, in order to use it for shallow trench isolation, it is preferable that scratches are less generated during polishing.

Here, as a polishing apparatus, a general polishing apparatus having a holder holding a semiconductor substrate and a polishing pad (a pad) and having a surface plate provided with a motor whose rotation speed can be changed is attached. Can be used. As the polishing cloth, general nonwoven fabric, foamed polyurethane, porous fluororesin and the like can be used, and there is no particular limitation. Further, it is preferable that the polishing cloth is subjected to a groove processing for accumulating a CMP abrasive. The polishing conditions are not limited, but the rotation speed of the surface plate is preferably 200 rpm or less so that the semiconductor substrate does not pop out, and the pressure applied to the semiconductor substrate is 1 kg / cm ² or less so that no scratch occurs after polishing. preferable. During polishing, the slurry is continuously supplied to the polishing cloth by a pump or the like. Although the supply amount is not limited, it is preferable that the surface of the polishing pad is always covered with the slurry.

After the polishing is completed, the semiconductor substrate is preferably washed well in running water, and then dried using a spin drier or the like to remove water droplets adhering to the semiconductor substrate. After forming the shallow trench flattened in this manner, an aluminum wiring is formed on the silicon oxide insulating film layer, and a silicon oxide insulating film is formed again between the wirings and on the wiring by the above-described method. By polishing using the above-mentioned CMP polishing agent, irregularities on the surface of the insulating film are eliminated, and a smooth surface is formed over the entire surface of the semiconductor substrate. By repeating this process a predetermined number of times, a semiconductor having a desired number of layers is manufactured.

The CMP polishing slurry of the present invention can be used not only for a silicon oxide film formed on a semiconductor substrate, but also for a silicon oxide film formed on a wiring board having predetermined wiring, an inorganic insulating film such as glass and silicon nitride, and a polycrystalline silicon oxide. Silicon, Al, Cu, Ti, TiN,
Weight a, a film mainly containing TaN, etc., optical glass such as a photomask, a lens, a prism, etc., an inorganic conductive film such as ITO, an optical integrated circuit composed of glass and a crystalline material.
Optical switching elements / optical waveguides, end faces of optical fibers,
Optical single crystal such as scintillator, solid laser single crystal, sapphire substrate for blue laser LED, SiC, GaP, G
semiconductor single crystal such as aAS, glass substrate for magnetic disk,
The magnetic head and the like can be polished.

[0034]

Example 1 (Preparation of cerium oxide particles) 2 kg of cerium carbonate hydrate was placed in a platinum container and calcined at 800 ° C. for 2 hours in the air to obtain about 1 kg of a yellowish white powder. The powder was subjected to phase identification by X-ray diffraction to confirm that it was cerium oxide. The particle diameter of the calcined powder was 30 to 100 μm. When the surface of the fired powder particles was observed with a scanning electron microscope, grain boundaries of cerium oxide were observed. When the primary particle diameter of the cerium oxide surrounded by the grain boundaries was measured, the median of the volume distribution was 190 nm and the maximum was 500 nm. 1 kg of cerium oxide powder was dry-ground using a jet mill. Observation of the pulverized particles with a scanning electron microscope revealed that, in addition to small particles having the same size as the primary particle size, 1
Large residual particles of about 3 μm and residual particles of 0.5 to 1 μm were mixed.

(Preparation of Cerium Oxide Slurry) 1 kg of the cerium oxide particles prepared above, 23 g of an aqueous solution of ammonium polyacrylate (40% by weight), and 8977 g of deionized water
Was mixed and subjected to ultrasonic dispersion for 10 minutes while stirring.
The resulting slurry is filtered through a 1 micron filter,
Further 5% by weight slurry was obtained by adding deionized water. The slurry pH was 8.3. As a result of diluting the slurry particles to an appropriate concentration in order to measure them with a laser diffraction type particle size distribution meter, the median value of the particle diameter was 190 nm.

(Polishing of interlayer insulating film) Si having a diameter of 200 mm
Line / Space width is 0.05-5mm and height is 100 on the substrate
After forming a 0 nm Al wiring Line portion, TE
A pattern wafer having a 2000 nm-thick silicon oxide film formed by OS-plasma CVD is manufactured. The above-mentioned pattern wafer is set on a holder to which a suction pad for attaching a substrate to be held is attached, and the holder is placed with the insulating film surface down on a platen having a diameter of 600 mm to which a polishing pad made of porous urethane resin is attached. , And a processing load of 30,000 Pa (30
0 gf / cm ² ). A mixture of the above-mentioned cerium oxide abrasive (solid content: 1% by weight) and a polymer additive polyammonium polyacrylate (solids content: 2.4% by weight) (the former / latter weight ratio was 1) / 4) dropwise at a rate of 200 ml / min, the platen and the wafer at 50min ^-1 2.
After rotating for 5 minutes, the insulating film was polished. The polished wafer was thoroughly washed with pure water and then dried.

In the same manner, the pattern wafer was polished with a polishing time of 3 minutes and 3.5 minutes. A line / space width 0.1 mm located at the center of the Si substrate, a step Sc of the Line portion having a line / space width of 0.1 mm, a film thickness Tc of the Space portion, and a line / space width of 0.5 mm located 50 mm in the radial direction from the center of the Si substrate.
Step Sm of 1 mm Line portion and Space portion and film thickness Tm of Space portion, located 90 mm in radial direction from the center of Si substrate
Line / Space Step of Se of 0.1mm width Line part and Space part
And the film thickness Te of the Space portion were measured. The step was measured using a stylus-type step meter, and the film thickness was measured using a light interference type film thickness meter.

When the polishing time is 2.5 minutes, steps Sc, S
m, Se are 40, 30, 40 nm, and film thicknesses Tc, Tm, Te
Were 1450, 1500 and 1500. When the polishing time is 3 minutes, the steps Sc, Sm, Se are 20, 15,
30 nm, film thicknesses Tc, Tm and Te are 1400, 1430,
1440. Further, when the polishing time is 3.5 minutes, the steps Sc, Sm, and Se are 40, 30, and 50 nm, the film thickness Tc,
Tm and Te were 1380, 1430 and 1420.
Since the flatness was the best when the polishing time was 3 minutes, the polishing time of 3 minutes was taken as the polishing end point. Assuming that the torque of the polishing table rotating shaft at the start of polishing is 1, the torque at the end of polishing after 3 minutes is 1.5. Further, the torque showed a maximum value of 1.6 ten seconds before the end of polishing. The torque took the maximum value 10
Since the end point of the polishing is reached after a lapse of seconds, it was possible to determine the polishing end point by reading the change in the torque.

(Polishing of shallow trench isolation insulating film)
A silicon nitride film is formed to a thickness of 150 nm on a Si substrate having a diameter of 200 mm by a plasma CVD method and has a line / space width of 0.05 to 5 mm.
After forming a groove with a depth of 500 nm by TEOS, TEOS
-Fabricate a pattern wafer on which a silicon oxide film is formed to a thickness of 600 nm by a plasma CVD method. The above-mentioned pattern wafer is set on a holder to which a suction pad for attaching a substrate to be held is attached, and the holder is placed with the insulating film surface down on a platen having a diameter of 600 mm to which a polishing pad made of porous urethane resin is attached. , And a processing load of 30,000 Pa (300 gf / c
m ² ).

A mixture of the above-mentioned cerium oxide abrasive (solid content: 1% by weight) and ammonium polyacrylate (solid content: 2.4% by weight) as a polymer additive (former:
The platen and the wafer were rotated at 50 min ^-1 for 3 minutes while the latter was dropped at a weight ratio of 1/4) at a rate of 200 ml / min, and the insulating film was polished. The polished wafer was thoroughly washed with pure water and then dried.

Similarly, the pattern wafer was polished by setting the polishing time to 3 minutes, 3.5 minutes, and 4 minutes. Line / Space 0.1mm width Line part and Spac located at the center of Si substrate
Step Sc of e portion and film thickness Tc of Space portion, Line / Space located at 50 mm in the radial direction from the center of the Si substrate, Line portion having Line / Space width of 0.1 mm, and step Sm of Space portion and film thickness Tm of Space portion, The step Se between the Line portion and the Space portion, each of which has a Line / Space width of 0.1 mm and the line portion located 90 mm in the radial direction from the center of the Si substrate, and the thickness Te of the Space portion were measured. The step was measured using a stylus-type step meter, and the film thickness was measured using a light interference type film thickness meter.

When the polishing time is 3 minutes, steps Sc, Sm, S
e is 30, 25, 25 nm, and the film thicknesses Tc, Tm, and Te are 45
0, 460 and 435. The polishing time is 3.5
Minute, steps Sc, Sm, Se are 40, 40, 60 nm,
The thicknesses Tc, Tm, and Te were 510, 500, and 480. Further, when the polishing time is 4 minutes, the steps Sc, Sm, S
e is 40, 30, and 35 nm, and film thicknesses Tc, Tm, and Te are 42
0, 435 and 400. Since the flatness was the best when the polishing time was 3.5 minutes, the polishing time was set to 3.5 minutes as the polishing end point. Reduce the torque of the polishing table rotating shaft at the start of polishing to 1
Then, the torque at the end of the polishing after 3 minutes was 1.75. The torque was set to a maximum value of 1.30 seconds before the end of polishing.
8 was shown. Since the polishing end point is reached 30 seconds after the torque reaches the maximum value, it was possible to determine the polishing end point by reading the change in the torque.

Comparative Example 1 (Preparation of Cerium Oxide Particles) 2 kg of cerium carbonate hydrate was placed in a platinum container and calcined at 800 ° C. for 2 hours in the air to obtain about 1 kg of yellowish white powder. When this powder was subjected to phase identification by an X-ray diffraction method, it was confirmed that the powder was cerium oxide. The particle diameter of the calcined powder was 30 to 100 μm. When the surface of the fired powder particles was observed with a scanning electron microscope, grain boundaries of cerium oxide were observed. When the primary particle diameter of the cerium oxide surrounded by the grain boundaries was measured, the median of the volume distribution was 190 nm and the maximum was 500 nm. 1 kg of cerium oxide powder was dry-ground using a jet mill. Observation of the pulverized particles with a scanning electron microscope revealed that, in addition to small particles having the same size as the primary particle size, 1
Large crushed particles having a size of ３3 μm and remaining particles having a size of 0.5 to 1 μm were mixed.

(Preparation of Cerium Oxide Slurry) 1 kg of the cerium oxide particles prepared above, 23 g of an aqueous solution of ammonium polyacrylate (40% by weight), and 8977 g of deionized water
Was mixed and subjected to ultrasonic dispersion for 10 minutes while stirring.
The resulting slurry is filtered through a 1 micron filter,
Further 5% by weight slurry was obtained by adding deionized water. The slurry pH was 8.3. As a result of diluting the slurry particles to an appropriate concentration in order to measure them with a laser diffraction type particle size distribution meter, the median value of the particle diameter was 190 nm.

(Polishing of interlayer insulating film) Si having a diameter of 200 mm
Line / Space width is 0.05-5mm and height is 100 on the substrate
After forming a 0 nm Al line part, TEOS
-Producing a pattern wafer on which a silicon oxide film is formed to a thickness of 2000 nm by a plasma CVD method. The above-mentioned pattern wafer is set on a holder to which a suction pad for attaching a substrate to be held is attached, and the holder is placed with the insulating film surface down on a platen having a diameter of 600 mm to which a polishing pad made of porous urethane resin is attached. , And a processing load of 30,000 Pa (300 gf
/ cm ² ).

While dropping the above-mentioned cerium oxide abrasive (solid content: 1% by weight) at a rate of 200 ml / min on a surface plate,
The platen and the wafer were rotated at 50 min ^-1 for 1.5 minutes to polish the insulating film. No polymer additives were added. The polished wafer was thoroughly washed with pure water and then dried.

Similarly, the pattern wafer was polished by setting the polishing time to 2 minutes and 2.5 minutes. A line / space width 0.1 mm located at the center of the Si substrate, a step Sc of the Line portion having a line / space width of 0.1 mm, a film thickness Tc of the Space portion, and a line / space width of 0.5 mm located 50 mm in the radial direction from the center of the Si substrate.
Step Sm of 1 mm Line portion and Space portion and film thickness Tm of Space portion, located 90 mm in radial direction from the center of Si substrate
Line / Space Step S between 0.1mm width Line and Space
e and the film thickness Te of the Space portion were measured. The step was measured using a stylus-type step meter, and the film thickness was measured using a light interference type film thickness meter.

When the polishing time is 1.5 minutes, the steps Sc, S
m, Se are 100, 70, 90 nm, and film thicknesses Tc, Tm, T
e became 1750, 1850, and 1700. When the polishing time is 2 minutes, the steps Sc, Sm, Se are 70, 6
0, 55 nm, film thicknesses Tc, Tm, Te are 1550, 178
0, 1630. Further, when the polishing time was 2.5 minutes, the steps Sc, Sm and Se were 85, 50 and 70 nm, and the film thicknesses Tc, Tm and Te were 1160, 1350 and 1120. Since the flatness was the best when the polishing time was 2.5 minutes, the polishing end point was 2.5 minutes when the polishing time was 2.5 minutes, but the flatness was poor as compared with the examples. Assuming that the torque of the polishing platen rotating shaft at the start of polishing is 1, the torque at the end of polishing 2.5 minutes later was 1.7. In addition, the maximum value of the torque is about 1.7 and is continuous for several tens of seconds. Therefore, it is difficult to determine the maximum value, and the end point of polishing cannot be read from the change in the torque.

Comparative Example 2 (Polishing of Interlayer Insulating Film) Line on a 200 mm Si substrate
After forming a line portion of Al wiring having a / Space width of 0.05 to 5 mm and a height of 1000 nm, a patterned wafer is formed on which a 2000 nm silicon oxide film is formed by TEOS-plasma CVD. The above-mentioned pattern wafer is set on a holder to which a suction pad for attaching a substrate to be held is attached, and the holder is placed with the insulating film surface down on a platen having a diameter of 600 mm to which a polishing pad made of porous urethane resin is attached. Further, the processing load was set to 30,000 Pa (300 gf / cm ² ). 200 ml / min of commercial silica slurry on platen
The platen and the wafer were rotated at 50 min ^-1 for 2 minutes while dropping at a speed of 2 to polish the insulating film. PH of commercial slurry
Is 10.3 and contains 12.5% by weight of SiO ₂ particles. The polished wafer was thoroughly washed with pure water and then dried.

Similarly, the pattern wafer was polished with a polishing time of 2.5 minutes and 3 minutes. A line / space width 0.1 mm located at the center of the Si substrate, a step Sc of the Line portion having a line / space width of 0.1 mm, a film thickness Tc of the Space portion, and a line / space width of 0.5 mm located 50 mm in the radial direction from the center of the Si substrate.
Step Sm of 1 mm Line portion and Space portion and film thickness Tm of Space portion, located 90 mm in radial direction from the center of Si substrate
Line / Space Step S between 0.1mm width Line and Space
The thickness Tc of c and Space portions was measured. The step was measured using a stylus-type step meter, and the film thickness was measured using a light interference type film thickness meter.

When the polishing time is 2 minutes, the steps Sc, Sm, S
e is 115, 150, 100 nm, film thicknesses Tc, Tm, Te
Were 1900, 1850, and 1740. When the polishing time is 2.5 minutes, the steps Sc, Sm, Se are 100,
105, 90 nm, film thicknesses Tc, Tm, Te are 1300, 1
280 and 1400. Further, when the polishing time was 3 minutes, the steps Sc, Sm and Se were 75, 80 and 70 nm, and the film thicknesses Tc, Tm and Te were 1020, 1100 and 1010. Since the flatness was the best when the polishing time was 3 minutes, the polishing end point was 3 minutes when the polishing time was 3 minutes, but the flatness was poor as compared with the examples. The torque monotonously decreased as the polishing progressed, and the end point of the polishing could not be read from the change in the torque.

[0052]

According to the first to third aspects of the present invention, the CMP polishing slurry can be highly planarized and can accurately determine the end point of polishing of the polished surface of the substrate. According to a fourth aspect of the present invention, there is provided a method for polishing a substrate, which can accurately determine an end point of polishing of a polished surface of a substrate.

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Claims (4)

[Claims] The torque of the polishing platen rotating shaft at the end of polishing is 1.2 to 2 times that at the start of polishing, and the torque of 10 to 10 times at the end of polishing.
Cerium oxide CMP polishing slurry consisting of a slurry that maximizes torque 30 seconds before. 2. The CMP polishing slurry according to claim 1, comprising a cerium oxide slurry containing cerium oxide particles, a dispersant and water, and an additive liquid containing a polymer additive and water. 3. The dispersant and the polymer additive are at least one compound selected from a water-soluble organic polymer, a water-soluble anionic surfactant, and a water-soluble nonionic surfactant. 4. The CMP polishing slurry according to 2 or 3. 4. A substrate on which a film to be polished is formed is pressed against a polishing cloth of a polishing platen and pressurized, and the CMP abrasive according to claim 1, 2, 3 or 4 is supplied between the polishing film and the polishing cloth. A substrate polishing method for polishing a film to be polished by rotating a substrate and a polishing platen.