JP2000109805A - Polishing agent for cmp and polishing of substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polishing agent for CMP, which can be easily disposed of when it becomes a waste, can polish the surface of a substrate such as a silicon oxide film at a high rate without scratching, and can show a ratio of the rate of polishing a silicon oxide film to that of polishing a silicon nitride film of 10 or greater, and to provide a method for polishing a substrate therewith. SOLUTION: There are provided a polishing agent for CMP, comprising cerium oxide particles, a dispersant, a biodegradable additive and water, or comprising a cerium oxide slurry containing cerium oxide particles, a dispersant, and water and an additive solution containing a biodegradable additive and water, wherein the biodegradable additive is an acrolein polymer or a derivative thereof; and a method for polishing a substrate, comprising pressing a substrate on which a film to be polished has been formed against the polishing cloth of a polishing surface plate and moving the substrate and the surface plate to polish the film to be polished while feeding the polishing agent for CMP into a space between the film to be polished and the polishing cloth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method used in a semiconductor device manufacturing technique, and is used in a step of flattening a substrate surface, particularly in a step of flattening an interlayer insulating film, a step of forming a shallow trench isolation, and the like. (Chemical Mechanical Polishing) polishing agent and a method for polishing a substrate using the CMP polishing agent.

[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 technology. This technology can completely flatten a layer to be exposed in a semiconductor device manufacturing process, reduce the burden of the exposure technology, and stabilize the yield. For example, flattening of an interlayer insulating film, shallow trench This is an essential technology for separation and the like.

Conventionally, in a manufacturing process of a semiconductor device, a plasma CVD (Chemical Vapor Depth) is used.
A colloidal silica-based polishing agent is generally considered as a CMP polishing agent for planarizing an inorganic insulating film layer such as a silicon oxide insulating film formed by a method such as oxidation, chemical vapor deposition, or low-pressure CVD. I was Colloidal silica-based abrasives are produced by subjecting silica particles to grain growth by a method such as thermal decomposition of tetrachlorosilicic acid and adjusting the pH.

[0004]

However, such a polishing agent does not have a sufficient polishing rate for the inorganic insulating film, and there is a technical problem of a low polishing rate for practical use. In the generation of the design rule of 0.5 μm or more, LOCOS (local oxidation of silicon) has been used for element isolation in an integrated circuit. After that, when the processing size is further reduced, a technique for narrowing the element isolation width is required, and the shallow 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 colloidal silica-based polishing agent has a small polishing rate ratio of about 3 between the silicon oxide film and the stopper film, and does not have practically usable characteristics for shallow trench isolation.

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.

[0006] Recently, the treatment of industrial waste is becoming a social problem. CMP abrasives are difficult to recycle, and used CMP abrasives are discarded as industrial waste. C
Abrasive particles contained in the MP abrasive waste liquid cannot be subjected to sewage treatment, and must be separated from waste water. When additives other than the abrasive particles are added to the CMP abrasive, it is desirable to separate the additives from the wastewater, but at present, there is little simple separation technology.

According to the present invention, a waste liquid treatment is easy, and a surface to be polished such as a silicon oxide film can be polished at a high speed without any damage.
Provided are a CMP polishing agent having a value of 0 or more and a method for polishing a substrate using the CMP polishing agent.

[0008]

The CMP polishing slurry of the present invention contains cerium oxide particles, a dispersant, a biodegradable additive, and water. The additive having biodegradability is preferably at least one selected from acrolein-based copolymers and derivatives thereof. The CMP polishing slurry of the present invention can be prepared from a cerium oxide slurry containing cerium oxide particles, a dispersant, and water, and a biodegradable additive and an additive solution containing water. Other components can be contained in the CMP polishing slurry. The ratio of the polishing rate of the silicon oxide film to the polishing rate of the silicon nitride film (the polishing rate of the silicon oxide film / the polishing rate of the silicon nitride film) is preferably 10 or more. The substrate polishing method of 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, and while supplying the CMP abrasive between the polishing film and the polishing cloth, The method is characterized in that a film to be polished is polished by relatively moving a polishing platen.

[0009]

DETAILED DESCRIPTION OF THE INVENTION Generally, cerium oxide 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 perform high-speed polishing as the primary particle diameter is larger and the crystal distortion is smaller, that is, the crystallinity is better. 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 0 nm or less. 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 the 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 ° C. to 900 ° C. 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 (198
0) pages 527-532.

[0011] The CMP polishing slurry of the present invention is, for example,
It can be obtained by dispersing a composition comprising cerium oxide particles having the above characteristics, a dispersant, and water, and further adding a biodegradable additive. Here, the concentration of the cerium oxide particles is not limited, but is preferably in the range of 0.5% by weight or more and 20% by weight or less from the viewpoint of easy handling of the dispersion. In addition, since it is used as a dispersant for polishing semiconductor chips, the content of alkali metals such as sodium ions and potassium ions, halogens, and sulfur is preferably suppressed to 10 ppm or less. For example, ammonium acrylate as a copolymerization component A polymer dispersant containing is preferred. Also selected from a polymer dispersant containing ammonium acrylate as a copolymer component and a water-soluble anionic dispersant, a water-soluble nonionic dispersant, a water-soluble cationic dispersant, and a water-soluble amphoteric dispersant. Two or more dispersants, including at least one, may be used.

Examples of the water-soluble anionic dispersant include triethanolamine lauryl sulfate, ammonium lauryl sulfate, polyoxyethylene alkyl ether triethanolamine sulfate, and a special polycarboxylic acid type polymer dispersant. Nonionic dispersants include, for example, 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 sorbite tetraoleate, polyethylene glycol monolaurate, polyethylene glycol mono Stearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, alkyl alkanolamide, and the like.Examples of the water-soluble cationic dispersant include coconut Amine acetate, stearylamine acetate, and the like, and examples of the water-soluble amphoteric dispersant include lauryl betaine, Allyl betaine, lauryl dimethylamine oxide, 2-alkyl -N- carboxymethyl -N- hydroxyethyl imidazolinium betaine. The dispersant may be biodegradable.

The amount of the dispersant added is based on 100 parts by weight of the cerium oxide particles based on the relationship between the dispersibility of the particles in the slurry and the prevention of sedimentation and the relationship between the polishing scratches and the amount of the dispersant added.
The range is preferably from 0.01 part by weight to 2.0 parts by weight. The molecular weight of the dispersant is preferably from 100 to 50,000, more preferably from 1,000 to 10,000. When the molecular weight of the dispersant is less than 100, a sufficient polishing rate cannot be obtained when polishing the silicon oxide film or the silicon nitride film, and when the molecular weight of the dispersant exceeds 50,000, the viscosity becomes high. This is because the storage stability of the CMP abrasive drops. As a method for dispersing the cerium oxide particles in water, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like can be used in addition to the dispersion treatment using a normal stirrer. The average particle size of the cerium oxide particles in the CMP polishing slurry thus produced is 0.01 μm to 1.
It is preferably 0 μm. If the average particle size of the cerium oxide particles is less than 0.01 μm, the polishing rate becomes too low, and if it exceeds 1.0 μm, the film to be polished is easily damaged.

The biodegradable additives include:
(B) acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, crotonic acid, isocrotonic acid, 4-pentenoic acid, 4-pentenoic acid, allylmalon Acid, glutaconic acid, citraconic acid, mesaconic acid, 2
-Acrolein-based polymer obtained by graft copolymerization of unsaturated mono- and dicarboxylic acids selected from -methylcrotonic acid and 2-methylisocrotonic acid, and a graft copolymer of unsaturated mono- and dicarboxylic acids, and derivatives thereof. preferable. Acrolein is more preferable as a structural unit of the acrolein-based polymer, and acrylic acid, methacrylic acid, fumaric acid, and maleic acid are more preferable as unsaturated mono- and dicarboxylic acids to be graft-copolymerized. The amount of the additive having biodegradability is set to 0.1 to 100 parts by weight of the cerium oxide particles from the relationship between the dispersibility of the particles in the CMP abrasive and the prevention of sedimentation, and the relationship between the polishing scratches and the additive amount. The range is preferably from 01 parts by weight to 1000 parts by weight. The molecular weight of the biodegradable additive is 100 to 500,0.
00 is preferable, and 1,000 to 50,000 is preferable. When the molecular weight of the additive is less than 100, a sufficient polishing rate cannot be obtained when polishing the silicon oxide film or the silicon nitride film, and when the molecular weight of the additive exceeds 500,000, the viscosity becomes high. This is because the storage stability of the CMP abrasive drops.

When a cerium oxide slurry composed of cerium oxide particles, a dispersant, and water and an additive solution composed of a biodegradable additive and water are stored as a separate CMP abrasive, the cerium oxide particles do not agglomerate. It is preferable because storage stability is increased, polishing scratches are prevented from being generated, and the polishing rate is stabilized. When polishing a substrate with the above-mentioned CMP polishing agent, 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 to polish. The method of supplying on a surface plate is taken.

As the CMP abrasive of the present invention, the above-mentioned CMP abrasive may be used as it is, but additives such as N, N-diethylethanolamine, N, N-dimethylethanolamine and aminoethylethanolamine are added. And CM
P abrasive can be used.

As a method for 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 is obtained by performing the SiH ₄ —O ₂ -based oxidation reaction at a low temperature of 400 ° 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
It is preferred to use ₂ -PH ₃ system 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. The plasma generation method includes two types, a capacitive coupling type and an inductive coupling type. As a reaction gas, SiH ₄ is used as a Si source, and N 2 is used as an oxygen source.
₂ O The SiH ₄ -N ₂ O-based gas and TEOS-O ₂ based gas of tetraethoxysilane (TEOS) was used in the Si source used (TEOS-plasma CVD method). The substrate temperature is 250 ° C to 400 ° C, and the reaction pressure is 67 to 400.
The range of Pa is preferable. As described above, the silicon oxide film of the present invention may be doped with an element such as phosphorus and boron. Similarly, silicon nitride film formation by low pressure CVD
Dichlorosilane: SiH ₂ Cl ₂ is used as an i source, and ammonia: NH ₃ is used as a nitrogen source. This SiH ₂ Cl ₂
It can be obtained by performing an -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. Substrate temperature is 3
00 ° C to 400 ° C is preferred.

A substrate in which 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 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,
Irregularities on the surface of the silicon oxide film layer can be eliminated, and a smooth surface can be obtained over the entire surface of the semiconductor substrate. In addition, shallow
It can also be used for trench isolation. For use in shallow trench isolation, it is necessary that the ratio of the polishing rate of the silicon oxide film to the polishing rate of the silicon nitride film and the polishing rate of the silicon oxide film / the polishing rate of the silicon nitride film be 10 or more. If the 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 becomes impossible 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. In addition, in order to use it for shallow trench isolation, it is necessary that the generation of scratches during polishing be small. Here, as a polishing apparatus, a holder for holding a semiconductor substrate and a polishing cloth (pad) were attached (a motor or the like capable of changing the number of rotations was attached).
A general polishing apparatus having a surface plate 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 platen is preferably low rotation of 200 rpm or less so that the semiconductor substrate does not jump out, and the pressure applied to the semiconductor substrate is 1 kg / cm ² or less so that scratches do not occur after polishing. Is preferred.
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.

It is preferable that the semiconductor substrate after polishing is thoroughly washed in running water, and then water drops adhering to the semiconductor substrate are removed using a spin drier or the like and then dried. After forming the shallow trench thus flattened, 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 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, Optical glasses such as masks, lenses, prisms, etc .; inorganic conductive films such as ITO; optical integrated circuits, optical switching elements, optical waveguides composed of glass and crystalline materials, end faces of optical fibers, optical single crystals such as scintillators, solids A laser single crystal, a sapphire substrate for a blue laser LED, a semiconductor single crystal such as SiC, GaP, and GaAs, a glass substrate for a magnetic disk, and a magnetic head can be polished.

[0021]

Next, the present invention will be described by way of examples. (Production of cerium oxide particles) 2 kg of cerium carbonate hydrate
Was placed in a platinum container, and calcined at 700 ° C. for 2 hours in the air to obtain about 1 kg of a 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. Cerium oxide powder was mixed with deionized water so as to have a concentration of 10% by weight, and pulverized at 1400 rpm for 120 minutes using a horizontal wet-type ultrafine particle pulverizer. The obtained polishing liquid was dried at 110 ° C. for 3 hours to obtain cerium oxide particles. The cerium oxide particles have a particle size of 10 nm to 60 n based on observation with a transmission electron microscope.
m and the result of the specific surface area measurement by the BET method was 39.5 m ² / g.

(Preparation of Cerium Oxide Slurry) Cerium oxide particles (125 g) prepared by the above-mentioned method, acrylic acid and methyl acrylate were copolymerized at a 3: 1 molecular weight of 10.0.
3 g of an aqueous ammonium polyacrylate solution (40% by weight) and 2372 g of deionized water were mixed and ultrasonically dispersed while stirring. Ultrasonic frequency is 40kHz
The dispersion was performed in a dispersion time of 10 minutes. The obtained slurry was filtered through a 0.8-micron filter, and further, deionized water was added to obtain a 2% by weight cerium oxide slurry (A-1). The pH of the cerium oxide slurry (A-1) was 8.5. Cerium oxide slurry (A-
When the particle size distribution of 1) was examined using a laser diffraction type particle size distribution meter, it was found that the average particle size was as small as 0.20 μm. Further, 95.0% of the particles had a size of 1.0 μm or less.

(Preparation of additive solution) 990 g of deionized water was added to 10 g of an ammonium salt of an acrolein copolymer having a molecular weight of 10,000 obtained by graft copolymerizing acrolein and acrylic acid at a ratio of 3: 1. An additive solution containing a polymer ammonium salt was obtained.

(Polishing of insulating film layer) A silicon oxide film formed by a TEOS-plasma CVD method on a holder on which a suction pad for attaching a substrate is attached on a surface plate on which a polishing pad made of porous urethane resin is attached. 125m diameter formed
m of silicon wafer was set with the insulating film face down, and weighted so that the polishing load was 300 g / cm ² .
The above-mentioned cerium oxide slurry (solid content: 2% by weight) and the additive liquid were sent onto the platen at a rate of 25 ml / min, and the nozzle was adjusted and dropped so that one liquid was obtained immediately before the platen. The platen was rotated at 40 rpm for 2 minutes to polish the insulating film. After polishing, the wafer was removed from the holder, washed well with running water, and further washed with an ultrasonic cleaner for 20 minutes. After washing, water droplets were removed with a spin drier and 12
It was dried in a dryer at 0 ° C. for 10 minutes. The change in film thickness before and after polishing was measured using an optical interference type film thickness measuring device, and the polishing rate was calculated. Similarly, instead of a silicon oxide film formed by the TEOS-plasma CVD method, a silicon nitride film formed by a low-pressure CVD method was polished under the same conditions, a change in film thickness before and after polishing was measured, and a polishing rate was calculated. From the results of the film thickness measurement, it was found that the silicon oxide film manufactured by the TEOS-plasma CVD method and the silicon nitride film manufactured by the low-pressure CVD method had a uniform thickness over the entire surface of the wafer.
Further, no damage was observed on the surface of the insulating film by visual observation under a light source of a mercury lamp.

(Evaluation of biodegradability) The biodegradability of the additive was evaluated according to JIS K 6950. 200 ml of activated sludge suspension and 0.8 ml of inorganic salt solution (K ₂ HPO) were placed in a glass culture bottle (300 ml) equipped with a burette.
_{4: 0.46%, Na 2 HPO} 4 · 12H 2 O: 1.1
_{6%, MgSO 4 · 7H 2} O: 0.05%, FeCl 3
_{· 6H 2 O: 0.01%,} CaCl 2 · 2H 2 O: 0.
005%, NH ₄ Cl: 0.1%), sample liquid about 1 m
and using a BOD measuring device equipped with a thermostat,
A decomposition test was performed at 25 ° C. The BOD (biochemical oxygen consumption) was measured over time for about 28 days. A value obtained by subtracting a blank test value to correct a change in the BOD value due to a change in the atmospheric pressure was defined as a true BOD value. The degree of biodegradation is (true BO
D value) ÷ (theoretical oxygen consumption) × 100.

Examples and Comparative Examples As shown in Table 1, a cerium oxide slurry and an additive solution were prepared to prepare a CMP abrasive, and the insulating film layer was polished. Table 1 shows the results. As is clear from Table 1, the additives contained in the CMP polishing slurry according to the present invention have good biodegradability and the waste liquid treatment is easy. Also, the CM of the present invention
By using the P polishing agent and the substrate polishing method, the substrate can be polished without being damaged, and the ratio of the silicon oxide film polishing rate / silicon nitride film polishing rate is 10 or more.
It can be seen that an MP polishing agent and a method for polishing a substrate using these CMP polishing agents can be obtained.

[0027]

[Table 1]

[0028]

According to the first aspect of the present invention, the CMP polishing slurry can be easily treated with waste liquid, and is suitably used in a polishing method used in semiconductor device manufacturing technology. The CMP polishing agent according to the second aspect has the effect according to the first aspect, and further enables high-speed polishing without damaging the surface to be polished such as a silicon oxide insulating film.
The CMP abrasive according to the third aspect is excellent in that storage stability is further improved. The CMP polishing agent according to claim 4 is suitable for shallow trench isolation in that the ratio of the polishing rate of the silicon oxide insulating film to the polishing rate of the silicon nitride insulating film is set to 10 or more. The method for polishing a substrate according to claim 5 is excellent in polishing a surface to be polished of a substrate without being damaged, and is suitably used for a polishing method used in a semiconductor device manufacturing technique.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/304 622 H01L 21/304 622D (72) Inventor Masato Yoshida 48 Wadai, Tsukuba, Ibaraki Prefecture Hitachi Chemical F-term in Tsukuba Development Laboratory Co., Ltd. (reference) 3C058 AA07 AA09 AA11 AA12 AB01 AB04 AC04 CA01 CB02 CB03 CB06 CB10 DA02 DA12

Claims (5)

[Claims] 1. A CMP polishing slurry containing cerium oxide particles, a dispersant, a biodegradable additive, and water. 2. The CMP polishing slurry according to claim 1, wherein the biodegradable additive is at least one selected from an acrolein-based copolymer and a derivative thereof. 3. A CMP comprising a cerium oxide slurry containing cerium oxide particles, a dispersant and water, an additive having biodegradability, and an additive liquid containing water.
Abrasive. 4. The ratio of the polishing rate of the silicon oxide film to the polishing rate of the silicon nitride film (the polishing rate of the silicon oxide film / the polishing rate of the silicon nitride film) is 1
The CMP abrasive according to any one of claims 1 to 3, which is 0 or more. 5. 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 polishing slurry according to claim 1 is supplied between the polishing film and the polishing cloth. And a polishing table for polishing a film to be polished by relatively moving a polishing platen.