JP2003007660A - Cmp abrasive and sustrate-polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CMP abrasive which enables polishing of a silicon oxide film to a high planarity and a high speed, without flaws, has a high stability, facilitates process control and is suited for planarizing a shallow trench isolating insulation film, and a substrate polishing method which is available for polishing the silicon oxide film to high planarity and a high speed, without flaws, and suited for planarizing the shallow trench isolating insulation film. SOLUTION: The CMP abrasive for semiconductor insulation films contains cerium oxide grains, a dispersant, polyvinyl pyrrolidone and water. The substrate polishing method comprises pressing a substrate, having a film to be polished to a polishing cloth of a polishing turn and grinding the film with the CMP abrasive fed between the film to be polished and with the polishing cloth, while the substrate is moved relative to the turntable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMP abrasive used in a flattening process of a substrate surface, which is a semiconductor element manufacturing technique, and particularly a shallow trench isolation forming process, and a substrate using the CMP abrasive. It relates to a polishing method.

[0002]

2. Description of the Related Art In the present ultra-large-scale integrated circuits, various microfabrication techniques have been researched and developed because the packaging density tends to be increased. The design rule is already on the order of sub-half micron. CM is one of the technologies that have been developed to satisfy such strict requirements for miniaturization.
There is P (Chemical Mechanical Polishing) technology. This technique can completely flatten the layer to be exposed in the manufacturing process of the semiconductor device, reduce the burden of the exposure technique, and stabilize the yield. Therefore, for example, flattening of the interlayer insulating film and the BPSG film, This is an indispensable technique when performing shallow isolation and trench isolation.

Conventionally, in a manufacturing process of a semiconductor device, a plasma-CVD (Chemical Vapor Dep) is used.
position, chemical vapor deposition method), low pressure-CVD, etc. As a CMP polishing material for planarizing an inorganic insulating film layer such as a silicon oxide insulating film, a fumed silica-based polishing material is generally studied. It has been. The fumed silica-based abrasive is manufactured by subjecting silica particles to particle growth by a method such as thermal decomposition of tetrachlorosilicic acid and adjusting the pH. However, such an abrasive does not have a sufficient polishing rate for the inorganic insulating film, and has a technical problem of low polishing rate for practical use.

In the generation of design rule 0.5 μm or more, LOCOS (silicon local oxidation) has been used for element isolation in an integrated circuit. After that, as the processing size becomes finer, a technique for narrowing the element isolation width is required, and shallow trench isolation is being used. In shallow trench isolation, C is used to remove the extra oxide film formed on the substrate.
MP is used, and a stopper film having a low polishing rate is formed below the silicon oxide film in order to stop the 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.

On the other hand, cerium oxide abrasives are used as glass surface abrasives for photomasks and lenses. Cerium oxide particles have lower hardness than silica particles and alumina particles and are less likely to scratch the polished surface, and are therefore useful for finish mirror polishing. Further, cerium oxide has a chemically active property as known as a strong oxidant. Taking advantage of this advantage, it is useful to apply to a chemical mechanical polishing material capable of high speed polishing. However, the cerium oxide-based abrasives currently used are capable of high-speed polishing,
Many scratches are made on the surface of the insulating film.

[0006]

According to the present invention, the silicon oxide film can be polished with high flatness and high speed, and the insulating film for shallow trench isolation is flattened without polishing scratches. The present invention provides a CMP abrasive that is suitable for use as a material. The invention according to claim 5 provides a method for polishing a substrate, which is capable of polishing a silicon oxide film with high flatness and at high speed, and which is suitable for flattening a shallow trench isolation insulating film without polishing scratches. It is a thing.

[0007]

The present invention relates to the following. (1) CMP for a semiconductor insulating film containing cerium oxide particles having a D50 volume% particle system of 100 to 300 nm and a D99 volume% particle system of 400 to 700 nm measured by a laser diffraction method, a dispersant, polyvinylpyrrolidone, and water Abrasive material. (2) The CMP abrasive according to (1), wherein the amount of polyvinylpyrrolidone added is 1 to 400 parts by weight with respect to 100 parts by weight of the cerium oxide particles. (3) The weight average molecular weight of polyvinylpyrrolidone is 1
The CMP abrasive according to (1) or (2), wherein the CMP abrasive is 10,000 to 1,200,000. (4) The CMP polishing slurry according to any one of (1) to (3), which has a pH of 6.5 to 10. (5) The CMP according to any one of (1) to (4), wherein the substrate on which the film to be polished is formed is pressed against a polishing cloth of a polishing platen.
A method of polishing a substrate, which comprises polishing a film to be polished by relatively moving a substrate and a polishing platen while supplying an abrasive between a polishing film and a polishing cloth.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The cerium oxide particles in the present invention are obtained by oxidizing a cerium compound of carbonate, nitrate, sulfate or oxalate. Oxidation can be performed, for example, by firing (350 to 900 ° C.) or using hydrogen peroxide or the like. Since the cerium oxide particles obtained by oxidation are usually agglomerated, it is preferable to mechanically grind them.
As a pulverization method, a dry pulverization method such as a jet mill or a wet pulverization method such as a planetary bead mill is preferable. The jet mill is, for example, a collection of chemical industry papers, Vol. 6, No. 5 (1980).
Pp. 527-532.

The crystallite diameter of the cerium oxide particles is preferably 5 to 300 nm from the viewpoint of high speed polishing and reducing scratches. Further, since it is used for polishing semiconductor chips, it is preferable to keep the content of alkali metals and halogens in the cerium oxide particles to 10 ppm or less.

The concentration of cerium oxide particles in the CMP abrasive of the present invention is preferably in the range of 0.5 to 20% by weight for easy handling.

Examples of the dispersant of the present invention include a polymer dispersant containing ammonium acrylate as a copolymerization component, a water-soluble anionic dispersant, a water-soluble nonionic dispersant, and a water-soluble cationic dispersant. Agents, water-soluble amphoteric dispersants and the like. These can be used alone or in combination of two or more.

Examples of the polymer dispersant containing ammonium acrylate as the copolymerization component include ammonium polyacrylate, ammonium salts of copolymers of alkyl acrylate and acrylic acid, and the like. Examples of the ionic dispersant include lauryl sulfate triethanolamine, ammonium lauryl sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and special polycarboxylic acid type polymer dispersant,
As the water-soluble nonionic dispersant, for example, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octylphenyl ether, Polyoxyethylene nonylphenyl ether, polyoxyalkylene alkyl ether,
Polyoxyethylene derivative, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sulbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan Trioleate, polyoxyethylene sorbite tetraoleate, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, alkyl alkanol Examples of water-soluble cationic dispersants include polyvinylpyrrolidone and co-amide. Examples of the water-soluble amphoteric dispersant include natyl amine acetate and stearyl amine acetate. Etc.

The amount of these dispersants added is preferably in the range of 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the cerium oxide particles from the viewpoints of dispersibility, prevention of sedimentation, polishing scratches and the like.

The weight average molecular weight of the dispersant (value measured by gel permeation chromatograph and converted to standard polystyrene, the same applies below) is preferably 100 to 50,000, more preferably 1,000 to 10,000. When the weight average molecular weight of the dispersant is less than 100, the polishing rate tends to be insufficient when polishing the silicon oxide film or the silicon nitride film, and the weight average molecular weight of the dispersant is 5 or less.
If it exceeds 50,000, the viscosity tends to be high, and the storage stability of the CMP abrasive tends to decrease.

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

The particle diameter of D50 volume% of cerium oxide dispersed in the slurry was 10 as measured by a laser diffraction method.
0 to 300 nm is preferable, and the particle size of D99 volume% is 4
00-700 nm is preferable. If the particle diameter of D50 volume% of cerium oxide is less than 100 nm, or the particle diameter of D99 volume% is less than 400 nm, it tends to be difficult to polish the surface to be polished such as a SiO ₂ insulating film at high speed. D50 volume% particle size exceeds 300 nm or D
If the particle size of 99% by volume exceeds 700 nm, SiO2
Scratches are easily generated on the surface to be polished such as the insulating film.

The particle size of cerium oxide was measured by using a laser diffraction type particle size distribution meter (refractive index: 1.93, absorption 0). As a measuring device, for example, MALVERN
MASTERSIZER (trade name) manufactured by the company can be used.

The particle size of D50 volume% is the median value of the volume particle size distribution, and means the particle size when the volume ratio of the particles is added up from 50% to 50%. . That is, when particles having a volume ratio of Vi% are present in the range of the particle diameter of a certain section Δ, assuming that the average particle diameter of the section Δ is di, the particles having the particle diameter di are Vi volume%. The abundance ratio Vi (volume%) of particles is integrated from the smaller particle diameter di, and di when Vi = 50% is taken as the particle diameter of D50 volume%. Also, V
The particle diameter of D99 volume% is defined as di when i = 99%.

The CMP abrasive of the present invention contains polyvinylpyrrolidone. The amount of polyvinylpyrrolidone added is
The range of 1 to 400 parts by weight is preferable with respect to 100 parts by weight of cerium oxide, the range of 1 to 100 parts by weight is more preferable, and the range of 1 to 10 parts by weight is particularly preferable. If it is less than 1 part by weight, the high flattening property tends to be insufficient,
If it exceeds 400 parts by weight, the polishing rate tends to be low and the throughput tends to be low.

The weight average molecular weight of polyvinylpyrrolidone is preferably 10,000 to 1,200,000.
If it is less than 10,000, the flattening property tends to be insufficient, and if it exceeds 2,000,000, the cerium oxide particles tend to aggregate.

The CMP abrasive of the present invention may be prepared by mixing cerium oxide particles, a dispersant, polyvinylpyrrolidone and water almost at once, and may be used. Since there is no change, a cerium oxide slurry composed of cerium oxide particles, a dispersant and water and an additive composed of polyvinylpyrrolidone and water are prepared separately, and these are mixed before use to prepare a CMP abrasive. You can also do it.

When polishing a substrate with a CMP abrasive, the additive liquid is separately supplied to the cerium oxide slurry and mixed on the polishing platen, or mixed with the cerium oxide slurry immediately before polishing. It is possible to use a method in which the cerium oxide slurry is mixed in advance with the cerium oxide slurry before the polishing and then is supplied onto the polishing platen. From the viewpoint of high flatness and high speed polishing, the pH of the CMP abrasive is preferably 6.5 to 10.

As a method for producing an inorganic insulating film which can be polished by the CMP abrasive of the present invention, a low pressure CVD method and a plasma C method are used.
VD method etc. are mentioned.

The formation of the silicon oxide film by the low pressure CVD method is
Monosilane: SiH ₄ as i source, oxygen as oxygen source:
O ₂ is used. This SiH ₄ —O ₂ system oxidation reaction
It is obtained by carrying out at a low temperature of ℃ or less. In some cases, heat treatment is performed at a temperature of 1000 ° C. or lower after CVD. When phosphorus: P is doped to achieve surface flattening by high temperature reflow, SiH ₄ —O ₂ —P
It is preferable to use an H ₃ -based reaction gas.

The plasma CVD method has an advantage that a chemical reaction which requires a high temperature under a normal thermal equilibrium can be performed at a low temperature.
There are two plasma generation methods, a capacitive coupling type and an inductive coupling type. As the reaction gas, Si as the 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 (TOES- plasma CVD
Law). The substrate temperature is preferably 250 ° C. to 400 ° C., and the reaction pressure is preferably 67 to 400 Pa. Thus, the silicon oxide film of the present invention may be doped with elements such as phosphorus and boron.

Similarly, in forming a silicon nitride film by the low pressure CVD method, dichlorosilane: SiH ₂ Cl ₂ ,
Ammonia: NH ₃ is used as a nitrogen source. This SiH
The ₂ Cl ₂ -NH ₃ based oxidation reaction can be obtained by performed at a high temperature of 900 ° C.. In the plasma CVD method, SiH ₄ as a Si source and NH ₃ as a nitrogen source are used as reaction gases.
SiH ₄ —NH ₃ based gas using is used. The substrate temperature is preferably 300 ° C to 400 ° C.

CMP of the present invention for shallow trench isolation
To use an abrasive, the film to be polished (silicon oxide film)
It is preferable to have a film thickness that is 1.0 to 1.2 times, and more preferably 1.0 to 1.1 times, the thickness of the underlying unevenness of the film to be polished. When the film thickness exceeds 1.2 times the unevenness of the underlying layer, the polishing time becomes extremely long and the throughput tends to decrease.

From the standpoint of easy control of polishing stop, it is preferable that the ratio of the polishing rate of the silicon oxide film to the polishing rate of silicon nitride and the polishing rate of silicon oxide / polishing rate of silicon nitride are 10 or more. When this ratio is less than 10, the difference between the polishing rate of silicon oxide and the polishing rate of silicon nitride is small, and it tends to be difficult to stop polishing at a predetermined position during shallow trench separation.

As the polishing apparatus, a general polishing apparatus having a holder for holding a semiconductor substrate and a surface plate to which a polishing cloth (pad) is attached (a motor or the like whose rotation speed is changeable is attached) can be used. . As the polishing cloth, general non-woven fabric, foamed polyurethane, other porous fluororesin, etc. can be used without any particular limitation. Further, it is preferable that the polishing cloth is grooved so that the CMP polishing material is accumulated. The polishing conditions are not limited, but the rotation speed of the surface plate is preferably a low rotation of 200 min ⁻¹ or less so that the semiconductor substrate does not pop out, and the pressure applied to the semiconductor substrate is 9.8 × so that scratches do not occur after polishing. It is preferably 10 ⁴ Pa or less. During polishing, slurry is continuously supplied to the polishing cloth with a pump or the like. Although the supply amount is not limited, it is preferable that the surface of the polishing cloth is always covered with the slurry.

It is preferable that the semiconductor substrate after the polishing is thoroughly washed in running water, and then water droplets adhering to the semiconductor substrate are removed by using a spin dryer or the like and then dried.

The CMP abrasive material of the present invention is not limited to a silicon oxide film formed on a substrate such as a semiconductor substrate, but also a silicon oxide film formed on a substrate such as a wiring board having predetermined wiring, glass, or silicon nitride. Inorganic insulation film such as polysilicon, Al, C
A film mainly containing u, Ti, TiN, W, Ta, TAN, etc., optical glass such as photomask / lens / prism, inorganic conductive film such as ITO, optical integrated circuit / light composed of glass and crystalline material Switching element / optical waveguide,
End face of optical fiber, optical single crystal such as scintillator,
It is possible to polish a solid-state laser single crystal, a blue laser LED sapphire substrate, a semiconductor single crystal such as SiC, GaP, or GaAs, a magnetic disk glass substrate, and a magnetic head.

[0032]

EXAMPLES The present invention will be described below with reference to examples.

Example 1 (1) Preparation of Cerium Oxide Particles 4 kg of cerium carbonate hydrate was placed in a platinum container and heated to 800 ° C.
Approximately 2 kg of yellowish white powder was obtained by firing in air for 2 hours. When this powder was subjected to phase identification by X-ray diffraction, it was confirmed to be cerium oxide. The particle size of the calcined powder was 30 to 100 μm. When the surface of the calcined powder particles was observed with a scanning electron microscope, grain boundaries of cerium oxide were observed. When the cerium oxide primary particle diameter surrounded by the grain boundaries was measured, the median volume distribution was 190 nm and the maximum value was 500 nm. Cerium oxide powder 2kg
Was dry-milled using a jet mill. When the crushed particles were observed with a scanning electron microscope, in addition to small particles having the same size as the primary particle size, large crushed residual particles of 1 to 3 μm and crushed residual particles of 0.5 to 1 μm were mixed. The polycrystalline particles were not aggregates of single crystal particles.

(2) Preparation of Abrasive Material 1 kg of the cerium oxide particles obtained in (1) above, 23 g of an aqueous solution of ammonium polyacrylate (40% by weight) and 8977 g of deionized water were mixed and ultrasonically dispersed with stirring. Was applied for 10 minutes. The resulting slurry was filtered through a 3 micron filter and then through a 0.5 micron filter, and further deionized water was added to the slurry to obtain 5% by weight.
A slurry was obtained. The slurry pH was 8.3. When the slurry was diluted to an appropriate concentration and measured with a laser diffraction particle size distribution analyzer, the particle diameter of D50 volume% was 190 nm,
The particle size of D99 volume% was 500 to 600 nm.

The above cerium oxide slurry (solid content: 5
Weight%) 600 g and a weight average molecular weight of 25 as an additive,
000 polyvinylpyrrolidone aqueous solution (2% by weight) 22
5 g and 2175 g of deionized water were mixed to prepare a cerium oxide abrasive (solid content: 1% by weight) to which a surfactant was added. The pH of the polishing agent was 8.2. Further, in order to measure the particles in the abrasive with a laser diffraction type particle size distribution meter, the particles were diluted to an appropriate concentration and the result was D50% by volume.
Has a particle size of 190 nm and D99 volume% has a particle size of 500
Was ~ 600 nm.

(Polishing of Insulating Film for Isolating Shallow Trench)
200 mm diameter with a 10 nm silicon oxide film on the surface
A silicon nitride film having a thickness of 90 nm is formed on the i substrate by a low pressure CVD method. A resist is formed on this substrate, exposed through a mask, and then developed to form a 60 × 60 μm resist-free portion. Next, the silicon nitride film, the silicon oxide film, and the silicon in the resist-free portion of the substrate were etched by reactive ion etching to form a trench, and then the resist was removed. The unevenness of the pattern wafer thus formed (trench depth) was 380 nm.

On this patterned wafer, a silicon oxide film was formed by TEOS-plasma CVD method to a thickness of 460 nm, which is 1.2 times as large as the uneven step. The pattern wafer is set on a holder to which a suction pad for wafer attachment is attached, and the holder is placed with the insulating film surface facing down on a surface plate having a diameter of 600 mm to which a polishing pad made of porous urethane resin is attached. The processing load was set to 30 kPa. 20% of the above cerium oxide abrasive (solid content: 1% by weight) on the surface plate
While dripping at a rate of 0 ml / min, the surface plate and the wafer were respectively rotated at 35 min ⁻¹ and 34 min ⁻¹ for 4 minutes to polish the silicon oxide film.

The polished wafer was thoroughly washed with pure water and then dried. The film thickness of the trench portion and other portions was measured using an interference type film thickness measuring device. The silicon oxide film thickness in the trench portion was 360 nm, the silicon oxide film in the portion other than the trench was completely polished and the film was lost, and the underlying silicon nitride film thickness was 89 nm. Therefore, polishing progresses to the surface of the nitride film, which is a predetermined position, and the surface of the oxide film in the trench is higher than the lower end of the nitride film. Further, when the wafer surface was observed using an optical microscope, no clear scratch was found.

Comparative Example (1) Preparation of Abrasive 1 g of cerium oxide particles obtained in the above Example (1) and ammonium polyacrylate aqueous solution (40% by weight) 2
3 g and 8977 g of deionized water were mixed and ultrasonically dispersed for 10 minutes while stirring. The obtained slurry was filtered with a 1-micron filter, and deionized water was further added to obtain a 5 wt% slurry. The slurry pH was 8.3. When the slurry was diluted to an appropriate concentration and measured with a laser diffraction type particle size distribution analyzer, the particle diameter of D50 volume% was 190 nm and the particle diameter of D99 volume% was 1000 nm.
Was 1100 nm.

The above cerium oxide slurry (solid content: 5
Weight%) 600 g and a weight average molecular weight of 25 as an additive,
000 polyvinylpyrrolidone aqueous solution (2% by weight) 22
5 g and 2175 g of deionized water were mixed to prepare a cerium oxide abrasive (solid content: 1% by weight) to which a surfactant was added. The pH of the polishing agent was 8.2. Further, in order to measure the particles in the abrasive with a laser diffraction type particle size distribution meter, the particles were diluted to an appropriate concentration, and the result was D50% by volume.
Has a particle size of 190 nm and D99 volume% has a particle size of 100
It was 0-1100 nm.

(Polishing of Insulating Film for Isolating Shallow Trench)
200 mm diameter with a 10 nm silicon oxide film on the surface
A silicon nitride film having a thickness of 90 nm is formed on the i substrate by a low pressure CVD method. A resist is formed on this substrate, exposed through a mask, and then developed to form a 60 × 60 μm resist-free portion. Next, the silicon nitride film, the silicon oxide film, and the silicon in the resist-free portion of the substrate were etched by reactive ion etching to form a trench, and then the resist was removed. The unevenness of the pattern wafer thus formed (trench depth) was 380 nm.

On this patterned wafer, a silicon oxide film was formed by TEOS-plasma CVD method to a thickness of 460 nm, which is 1.2 times the unevenness. The pattern wafer is set on a holder to which a suction pad for wafer attachment is attached, and the holder is placed with the insulating film surface facing down on a surface plate having a diameter of 600 mm to which a polishing pad made of porous urethane resin is attached. The processing load was set to 30 kPa. 20% of the above cerium oxide abrasive (solid content: 1% by weight) on the surface plate
While dripping at a rate of 0 ml / min, the surface plate and the wafer were respectively rotated at 35 min ⁻¹ and 34 min ⁻¹ for 4 minutes to polish the silicon oxide film.

The polished wafer was thoroughly washed with pure water and then dried. The film thickness of the trench portion and other portions was measured using an interference type film thickness measuring device. The silicon oxide film thickness in the trench portion was 340 nm, the silicon oxide film in the portion other than the trench was completely polished and the film was lost, and the underlying silicon nitride film thickness was 87 nm. Therefore, polishing progresses to the surface of the nitride film, which is a predetermined position, and the surface of the oxide film in the trench is higher than the lower end of the nitride film. When the surface of the wafer was observed using an optical microscope, 37 scratches of 0.2 μm or more were observed per wafer.

[0044]

EFFECTS OF THE INVENTION The CMP abrasives according to claims 1 to 4 can polish a silicon oxide film without scratches, can perform high flatness and high speed, have high stability, and can easily perform process control. This is suitable for flattening the insulating film for shallow trench isolation. The method of polishing a substrate according to claim 5,
The silicon oxide film can be polished with high flatness and high speed without scratches, has high stability, and can be easily process-controlled, and is suitable for flattening the insulating film for shallow trench isolation. .

Claims (5)

[Claims] 1. Cerium oxide particles having a D50 volume% particle diameter of 100 to 300 nm and a D99 volume% particle diameter of 400 to 700 nm measured by a laser diffraction method,
A CMP abrasive for a semiconductor insulating film containing a dispersant, polyvinylpyrrolidone and water. 2. The CMP abrasive according to claim 1, wherein the amount of polyvinylpyrrolidone added is 1 to 400 parts by weight based on 100 parts by weight of the cerium oxide particles. 3. The weight average molecular weight of polyvinylpyrrolidone is 10,000 to 1,200,000.
Alternatively, the CMP abrasive according to item 2. 4. The method according to claim 1, wherein the pH is 6.5 to 10.
The CMP abrasive according to any one of 1. 5. The C according to claim 1, wherein the substrate having a film to be polished is pressed against a polishing cloth of a polishing platen.
A substrate polishing method for polishing a film to be polished by relatively moving a substrate and a polishing platen while supplying an MP abrasive between a polishing film and a polishing cloth.