JP2006191134A - Abrasive powder and polishing method of substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide abrasive powder for planarizing a plane to be polished of an oxidation insulating film efficiently at a high speed while facilitating process management, and applicable to shallow trench isolation because of a high polishing speed ratio to a silicon nitride film. <P>SOLUTION: The abrasive powder contains cerium oxide particles, water, and a polyacrylic acid ammonium salt wherein the pH and viscosity (mPa s) of the abrasive powder fall within a region surrounded by four points, i.e. point A(5.5, 1.0), point B(5.5, 2.5), point C(9.0, 2.5) and point D(8.5, 1.0), in an (x, y) coordinate system where x coordinate represents pH and y coordinate represents viscosity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing agent and a polishing method used in a semiconductor element manufacturing technique, and a polishing agent used in a substrate surface flattening step, in particular, an interlayer insulating film flattening step, a shallow trench element isolation forming step, and the like. And a method of polishing a substrate using these abrasives.

  In the current ULSI semiconductor device manufacturing process, processing technology for high density and miniaturization has been researched and developed. CMP (Chemical Mechanical Polishing) technology, which is one of them, is an indispensable technology for planarizing interlayer insulating films, forming shallow trench elements, forming plugs and buried metal wiring, etc. in the manufacturing process of semiconductor devices. It has become to.

  Conventionally, a fumed silica-based polishing agent as a chemical mechanical polishing agent for planarizing an inorganic insulating film layer such as a silicon oxide insulating film formed by a method such as plasma-CVD or low-pressure CVD in a manufacturing process of a semiconductor element Is generally considered. The fumed silica-based abrasive is produced by growing silica particles by a method such as thermal decomposition of tetrachlorosilicic acid and adjusting pH. However, such an abrasive has a technical problem that the polishing rate is low and the flatness of the pattern is poor.

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

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

  On the other hand, LOCOS (Silicon Local Oxidation) has been used for element isolation in integrated circuits in generations with design rules of 0.5 μm or more. Trench isolation technology is being adopted. In shallow trench isolation, CMP is an indispensable technique for removing an excess silicon oxide film embedded on a substrate. Since the silicon nitride film is mainly formed as a mask and a stopper other than the portion where the silicon oxide film is embedded in the element isolation, the polishing rate ratio between the silicon oxide film and the silicon nitride film (the silicon oxide film It is desirable that the polishing rate / the polishing rate of the silicon nitride film be high. However, the conventional silica-based polishing agent has a polishing rate ratio of only about 2 to 3, and has a problem that a process margin cannot be obtained sufficiently.

  A polishing agent containing cerium oxide or the like that can obtain a high polishing rate of a silicon oxide film as compared with a silica-based polishing agent is also used. However, since the polishing rate is too high, the process management is difficult, and the dependency of the polishing rate on the pattern of the film to be polished on the substrate is large. In addition, since it is generally used at a relatively low particle concentration, there is a problem that the convex portion is less likely to be scraped as the pattern of the film to be polished on the substrate becomes finer. Further, a polishing agent containing cerium oxide can obtain a polishing rate ratio of a silicon oxide film to a silicon nitride film that is about twice that of a silica-based polishing agent, but it is still not practically sufficient.

  The present invention provides a polishing agent and a polishing method that can efficiently planarize a silicon oxide film at a high level and easily perform process management in a CMP technique for planarizing an interlayer insulating film. In addition, in the slurry containing cerium oxide particles generally used at a lower particle concentration than the silica-based slurry, the problem that the convex portion of the fine pattern such as shallow trench isolation is difficult to be removed is solved. The present invention is also applicable to shallow trench isolation polishing that requires a high polishing rate ratio between the film and the silicon nitride film.

  The CMP polishing slurry of the present invention is a polishing slurry containing cerium oxide particles, water, and an anionic surfactant as an additive. The pH and viscosity (mPa · s) are represented by points A (5.5, 1.0), B (5.5, 5.5) in the (x, y) coordinate system in which the pH is the x coordinate and the viscosity is the y coordinate. 2.5), C point (9.0, 2.5), and D point (8.5, 1.0) are within the range of the area surrounded by 4 points, and AA point (6.0) , 1.0), BB point (6.0, 1.4), CC point (8.4, 1.4), DD point (7.5, 1.0). More preferably, it is within. As a result, planarization of the silicon oxide film can be performed efficiently, at a high level, and process management can be easily performed. Further, since the ratio of the silicon oxide film polishing rate to the silicon nitride film polishing rate is increased, the present invention can be applied to shallow trench isolation.

  The primary particle diameter of the cerium oxide particles in the abrasive (the diameter of the crystallites constituting the cerium oxide particles, which can be measured by observation with an electron microscope) is 5 to 600 nm, and the median particle diameter is 100 to 100 nm. It is preferably 2000 nm, the primary particle diameter is 30 to 500 nm, and the median particle diameter is more preferably 150 to 1500 nm. As the anionic surfactant, an organic polymer anionic surfactant, particularly, an ammonium acrylate salt is preferably used as a copolymerization component.

  Further, according to the present invention, in a substrate having a convex portion formed with a constant width and having a film to be polished on the surface, a polishing rate R5 when the width of the convex portion is 5 mm and a polishing rate when the width of the convex portion is 1 mm. The ratio R3 / R1 of R1 is in the range of 1 ≧ R5 / R1> 0.65, and the ratio R3 / the polishing rate R3 when the width of the convex portion is 3 mm and the polishing rate R1 when the width of the convex portion is 1 mm. An abrasive in which R1 is in the range of 1 ≧ R3 / R1> 0.8 is provided.

The substrate polishing method of the present invention is to polish a predetermined substrate with the above-described abrasive, and a semiconductor chip on which at least a silicon oxide film is formed is used as the predetermined substrate. In the substrate polishing method of the present invention, the polishing surface plate and the substrate are relatively moved while the substrate having the film to be polished is pressed against the polishing cloth while supplying the abrasive onto the polishing cloth of the polishing surface plate. by in the step of polishing the film is preferably pressed against the pressure of the polishing cloth substrate having a film to be polished is 100~1000gf / cm ^2, more preferably 200~500gf / cm ^2.

  With the abrasive and the polishing method of the present invention, the planarization of the silicon oxide film can be performed efficiently, at a high level, and process management can be easily performed. In addition, a polishing rate ratio between a silicon oxide film and a silicon nitride film, such as shallow trench isolation, is required, and it can be applied to polishing.

  By polishing with cerium oxide particles, water, and an abrasive containing an anionic surfactant as an additive, the surfactant covers the surface of the film to be polished on the substrate, and the surface of the film to be polished becomes the surface of the film to be polished. Is hindered and polishing does not proceed. However, by increasing the polishing load, the surfactant that covers the surface of the film to be polished is eliminated due to mechanical stress, so that polishing proceeds. By adjusting the surfactant concentration and the polishing load based on the polishing load dependency of the polishing rate due to such an action, a convex portion having a large effective polishing load is selectively selected according to the pattern shape of the film to be polished. The characteristic to polish can be realized. As a result, the planarization of the interlayer insulating film can be realized with high efficiency and high level. In addition, since the polishing rate after flattening becomes equal to the polishing rate of a blanket film without a pattern, by adjusting the amount of addition of the surfactant and the polishing load so that the polishing rate becomes sufficiently small, the process according to time Management is also easy.

  In order to achieve global flatness with little pattern dependency, the amount of surfactant added and the pH are adjusted so that the polishing rate of the pattern recesses is sufficiently smaller than the polishing rate of the projections. There is a need to. The viscosity of the abrasive is preferably in the range of 1.0 to 2.5 mPa · s, more preferably 1.0 to 1.4 mPa · s. As the viscosity of the polishing agent increases, the pattern dependency of the film to be polished tends to increase, for example, the polishing rate of wide convex portions having a width of 1 mm or more is smaller than the polishing rate of convex portions having a width of 1 mm or less. In the present invention, the viscosity of the abrasive is calculated from the kinematic viscosity measured with an Ubbelohde viscometer and the specific gravity measured with a float type hydrometer.

  Above pH 5.5, the surface potential of the silicon oxide film increases negatively. In addition, in the region of pH 5.5 or higher, surfactants such as ammonium polyacrylate are dissociated. By using an anionic surfactant as an additive as the surfactant, an appropriate load dependency can be obtained on the polishing rate due to the surface potential of the film to be polished and the electrical repulsion of the surfactant. The lower the pH of the polishing agent, the weaker the electric repulsion between the silicon oxide film surface and the anionic surfactant, and the load dependency of the polishing rate is seen with a smaller amount of added surfactant. Since the viscosity increases with the addition amount of the surfactant, the surfactant is added in order to realize the flattening characteristics with less pattern dependency by setting the viscosity within the range of 1.0 to 1.4 mPa · s. It is preferable that pH of the abrasive | polishing agent after having been in the range of 5.5-9, and 6-8.5 are more preferable. When the pH is 10 or more, the repulsion between the surface of the silicon oxide film and the surfactant increases, and no load dependency of the polishing rate is observed even when a large amount is added. As a result, since the pattern convex portions cannot be selectively polished, it is impossible to realize the flattening characteristic of selectively polishing the convex portions. In addition, when the pH is 9 or more, the amount of the surfactant added to realize the load dependency of the polishing rate capable of selectively polishing the convex portion is large, resulting in an increase in viscosity. Global flatness with little pattern dependency cannot be realized. On the other hand, at a pH of 5.5 or less, the cerium oxide particles are likely to aggregate, so that there is no stability and a sufficient polishing rate cannot be obtained. In the present invention, the pH of the abrasive is measured with a pH meter (for example, HM-11 manufactured by Toa Radio Co., Ltd.).

  Since the polishing agent of the present invention has a large polishing rate ratio between the silicon oxide film and the silicon nitride film, it can also be applied to polishing for shallow trench isolation. The cause is as follows. In the range of pH 5.5 to 8.5, the surface potential of the silicon nitride film is plus to zero, and the difference from the surface potential with the silicon oxide film is large. Due to the difference in electrical repulsion from the anionic surfactant, the surface of the silicon nitride film is more easily covered with the surfactant, and the polishing rate is reduced with a small amount of added surfactant. As a result, the polishing rate ratio between the silicon oxide film and the silicon nitride film is increased, and application to shallow trench isolation becomes possible. When the pH is 8.5 or more, the surface potential of the silicon nitride film becomes negative, and the difference in surface potential from the silicon oxide film becomes small, so that the polishing rate ratio is reduced. In particular, when the pH is 10 or more, the polishing rate ratio becomes smaller than that of the cerium oxide slurry to which no surfactant is added, and the effect of adding the surfactant is lost. In addition, a slurry containing cerium oxide particles generally used at a lower particle concentration than a silica-based slurry has a problem that a convex portion of a fine pattern such as shallow / trench separation is difficult to be removed. The problem is solved by covering the surface of the film to be polished so that the cerium oxide particles effectively act on the fine convex portions.

In a polishing method for polishing a film to be polished by relatively moving the polishing platen and the substrate while pressing the substrate having the film to be polished against the polishing cloth while supplying an abrasive onto the polishing cloth of the polishing table The pressing force of the substrate having the film to be polished on the polishing cloth is selectively polished by the convex portion with respect to the pattern concave portion according to the load-dependent characteristics of the polishing rate determined mainly by the addition amount and pH of the surfactant. Need to be set to a range. Pushing pressure on the polishing cloth is preferably 100~1000gf / cm ^2, more preferably 200~500gf / cm ^2. In order to satisfy the uniformity of the polishing rate within the wafer surface and the flatness of the pattern, it is more preferably 200 to 500 gf / cm ² . If the pressure applied to the polishing cloth is greater than 1000 gf / cm ² , polishing scratches are likely to occur, and if it is less than 100 gf / cm ² , a sufficient polishing rate cannot be obtained.

  In general, cerium oxide is obtained by firing a cerium compound such as carbonate, sulfate, or oxalate. A silicon oxide insulating film formed by a TEOS-CVD method or the like can be polished at a higher speed as the primary particle diameter of cerium oxide is larger and the crystal distortion is smaller, that is, the better the crystallinity is, but polishing scratches are more likely to occur. Tend. Therefore, the production method of the cerium oxide particles used in the present invention is not limited, but the median cerium oxide primary particle diameter is preferably 5 to 600 nm, and more preferably 30 to 500 nm. Moreover, since it uses for semiconductor chip grinding | polishing, it is preferable to suppress the content rate of an alkali metal and halogens to 1 ppm or less. In the present invention, the primary particle diameter is measured by observation with a scanning electron microscope (for example, S-900 type manufactured by Hitachi, Ltd.). The abrasive | polishing agent of this invention is a highly purified thing, Na, K, Si, Mg, Ca, Zr, Ti, Ni, Cr, and Fe are 1 ppm or less respectively, and Al is 10 ppm or less. In the present invention, the method for producing cerium oxide particles is not limited, but a firing method can be used. However, low temperature firing that does not increase the crystallinity as much as possible is preferable in order to produce particles free from abrasive scratches. The calcined cerium oxide can be pulverized by dry pulverization, wet pulverization or the like to obtain a predetermined particle size distribution.

  The cerium oxide slurry in the present invention is obtained by dispersing an aqueous solution containing cerium oxide particles produced by the above method, or a composition comprising cerium oxide particles recovered from this aqueous solution, water and, if necessary, a dispersant. It is done. Here, although there is no restriction | limiting in the density | concentration of a cerium oxide particle, The range of 0.5 to 10 weight% is preferable from the ease of handling of suspension. The dispersant does not contain metal ions, and includes acrylic acid polymer and its ammonium salt, methacrylic acid polymer and its ammonium salt, water-soluble organic polymers such as polyvinyl alcohol, ammonium lauryl sulfate, and polyoxyethylene. Water-soluble anionic surfactants such as ammonium lauryl ether sulfate, water-soluble nonionic surfactants such as polyoxyethylene lauryl ether and polyethylene glycol monostearate, and water-soluble amines such as monoethanolamine and diethanolamine It is done. Polyacrylic acid ammonium salts, particularly polyacrylic acid ammonium salts having a weight average molecular weight of 2000 to 20000 are preferred. The amount of these dispersants added is preferably in the range of 0.01 to 5 parts by weight with respect to 100 parts by weight of the cerium oxide particles in view of the dispersibility of the particles in the slurry and the anti-settling property. In order to achieve this, it is preferable to place the particles in the disperser simultaneously with the particles during the dispersion treatment.

  As a method for dispersing these cerium oxide particles in water, a homogenizer, an ultrasonic disperser, a ball mill, or the like can be used in addition to a dispersion treatment using a normal stirrer. In particular, in order to disperse the cerium oxide particles as fine particles having a size of 1 μm or less, it is preferable to use a wet disperser such as a ball mill, a vibration ball mill, a planetary ball mill, or a medium stirring mill. When it is desired to increase the alkalinity of the slurry, an alkaline substance that does not contain metal ions such as aqueous ammonia can be added during or after the dispersion treatment.

  The cerium oxide abrasive of the present invention may use the above slurry as it is, but additives such as N, N-diethylethanolamine, N, N-dimethylethanolamine, aminoethylethanolamine are added. Thus, an abrasive can be obtained.

  As the surfactant, at least one surfactant selected from water-soluble anionic surfactants such as a polymer dispersant containing an ammonium salt as a copolymerization component is used. Water-soluble anionic surfactants include those that do not contain metal ions, methacrylic acid polymers and their ammonium salts, water-soluble organic polymers such as polyvinyl alcohol, ammonium lauryl sulfate, ammonium polyoxyethylene lauryl ether sulfate, etc. Can be used. In addition, a water-soluble nonionic surfactant, a water-soluble anionic surfactant, a water-soluble cationic surfactant and the like may be used in combination. The amount of these surfactants added is preferably in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the cerium oxide slurry. The molecular weight of the surfactant is preferably 100 to 50000, more preferably 2000 to 20000. As a method for adding the surfactant, it is preferable to mix the cerium oxide slurry immediately before polishing. When a structure that mixes well in the slurry supply pipe of the polishing apparatus is applied, the supply speed of the cerium oxide slurry and the surfactant aqueous solution should be individually adjusted and mixed so as to have a predetermined concentration in the pipe. Is also possible. When stored for a long time after the addition of a surfactant, the particle size distribution of the cerium oxide slurry may change, but there is no significant effect on the polishing characteristics such as polishing rate and polishing scratches. There is no limit to the method.

  The average particle size of the particles in the abrasive thus prepared is preferably 100 to 2000 nm, and more preferably 150 to 1500 nm. This is because if the average particle size of the cerium oxide particles is less than 100 nm, the polishing rate becomes too low, and if it exceeds 2000 nm, the film to be polished is likely to be damaged. In the present invention, the particle size of the particles in the abrasive is measured with a laser diffraction particle size distribution analyzer (for example, MASTER SIZER manufactured by MALVERN).

Examples of a method for manufacturing an inorganic insulating film in which the cerium oxide abrasive of the present invention is used include a constant pressure CVD method and a plasma CVD method. Formation of the silicon oxide insulating film by the constant pressure CVD method uses monosilane: SiH ₄ as the Si source and oxygen: O ₂ as the oxygen source. It can be obtained by performing this SiH ₄ —O ₂ -based oxidation reaction at a low temperature of about 400 ° C. or less. When doping phosphorus: P in order to achieve surface flattening by high-temperature reflow, it is preferable to use a SiH ₄ —O ₂ —PH ₃ -based reactive 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 plasma generation methods, capacitive coupling type and inductive coupling type. The reaction as a gas, SiH ₄ as an Si source, an oxygen source as _{N 2} O was used was _SiH 4 -N ₂ O-based gas and _{TEOS-O 2} based gas using tetraethoxysilane (TEOS) in an Si source (TEOS- Plasma CVD method). The substrate temperature is preferably 250 to 400 ° C., and the reaction pressure is preferably 67 to 400 Pa. Thus, elements such as phosphorus and boron may be doped in the silicon oxide insulating film of the present invention. Similarly, silicon nitride film formation by low pressure CVD uses dichlorosilane: SiH ₂ Cl ₂ as a Si source and ammonia: NH ₃ as a nitrogen source. It can be obtained by performing this SiH ₂ Cl ₂ —NH ₃ oxidation reaction at a high temperature of 900 ° C. Examples of the plasma CVD method include SiH ₄ —NH ₃ gas using SiH ₄ as a Si source and NH ₃ as a nitrogen source. The substrate temperature is preferably 300 to 400 ° C.

As the predetermined substrate, a semiconductor substrate, that is, a semiconductor substrate at a stage where a circuit element and a wiring pattern are formed, a semiconductor substrate such as a semiconductor substrate at a stage where a circuit element is formed, a silicon oxide film or a silicon oxide film and a silicon nitride film. The formed substrate can be used. By polishing the silicon oxide film layer formed on such a semiconductor substrate with the cerium oxide abrasive, unevenness on the surface of the silicon oxide film layer is eliminated, so that the entire surface of the semiconductor substrate is smooth. In the case of shallow trench isolation, only the silicon oxide film embedded in the element isolation portion is left by polishing the underlying silicon nitride layer while eliminating the unevenness of the silicon oxide film layer. At this time, if the polishing rate ratio with the silicon nitride serving as a stopper is large, the polishing process margin becomes large. In addition, in order to use for shallow trench isolation, it is also necessary to reduce the generation of scratches during polishing. Here, as a polishing apparatus, a general polishing apparatus having a surface plate with a holder for holding a semiconductor substrate and a polishing cloth (pad) attached (a motor etc. capable of changing the number of rotations) is used. it can. As an abrasive cloth, a general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. can be used, and there is no restriction | limiting in particular. Further, it is preferable that the polishing cloth is subjected to groove processing so that an abrasive is collected. The polishing conditions are not limited, but the rotation speed of the surface plate is preferably a low rotation of 100 rpm or less so that the semiconductor does not jump out. The pressure applied to the polishing cloth of the semiconductor substrate having the film to be polished is preferably 100 to 1000 gf / cm ^{2. In} order to satisfy the uniformity of the polishing rate within the wafer surface and the flatness of the pattern, the pressure is 200 to 500 gf. / Cm ² is more preferable. During polishing, an abrasive is continuously supplied to the polishing cloth with a pump or the like. Although there is no restriction | limiting in this supply amount, It is preferable that the surface of polishing cloth is always covered with the abrasive | polishing agent.

  The semiconductor substrate after the polishing is preferably washed in running water, and then dried after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like. In this manner, after forming shallow trench isolation on the Si substrate, a silicon oxide insulating film layer and an aluminum wiring are formed thereon, and the silicon oxide film formed thereon is planarized. A second-layer aluminum wiring is formed on the planarized silicon oxide film layer, and a silicon oxide film is formed again between the wirings and on the wiring by the above method, followed by polishing with the cerium oxide abrasive. By doing so, unevenness on the surface of the insulating film is 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 desired number of semiconductor layers are manufactured.

  The cerium oxide abrasive of the present invention is not limited to a silicon oxide film or a silicon nitride film formed on a semiconductor substrate, but an inorganic insulating film such as a silicon oxide film, glass, or silicon nitride formed on a wiring board having a predetermined wiring. Optical glass such as photomasks, lenses and prisms, inorganic conductive films such as ITO, optical integrated circuits composed of glass and crystalline materials, optical switching elements, optical waveguides, end faces of optical fibers, scintillators, etc. It is used for polishing optical single crystals, solid laser single crystals, LED sapphire substrates for blue lasers, semiconductor single crystals such as SiC, GaP, and GaAS, glass substrates for magnetic disks, magnetic heads, and the like.

Example 1
(Production of cerium oxide particles)
About 1 kg of yellowish white powder was obtained by putting 2 kg of cerium carbonate hydrate into a platinum container and firing in air at 800 ° C. for 2 hours. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. The fired powder particle size 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 (crystallite diameter) of cerium oxide surrounded by the grain boundaries was measured, the median value of the volume distribution was 190 nm and the maximum value was 500 nm. 1 kg of cerium oxide powder was pulverized. Observation of the pulverized particles with a scanning electron microscope revealed that in addition to small particles having a size equivalent to the primary particle size, large pulverized residual particles of 1 to 3 μm and residual pulverized 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 polyacrylic acid ammonium salt solution (40% by weight), and 8977 g of deionized water were mixed and subjected to ultrasonic dispersion for 10 minutes while stirring. The resulting slurry was filtered and further deionized water was added to add 5 wt. % Slurry was obtained. The slurry pH was 8.3. A mixture of 600 g of the above cerium oxide slurry (solid content: 5 wt%), 135 g of a polyacrylic acid (100%) ammonium salt aqueous solution (40 wt%) having a pH of 6.5 and a molecular weight of 5000 as a surfactant and 2265 g of deionized water. Thus, a cerium oxide abrasive (solid content: 1% by weight) to which a surfactant was added was prepared. The abrasive pH was 7.0, and the viscosity calculated from the measured values of the Ubbelohde viscometer and the specific gravity meter was 1.19 mPa · s. Further, in order to measure the particles in the abrasive with a laser diffraction particle size distribution meter, the particles were measured by diluting to an appropriate concentration. As a result, the median particle diameter was 260 nm.

(Polishing the insulating film layer)
An Al wiring Line portion having a Line / Space width of 0.05 to 5 mm and a height of 1000 nm is formed on a Si substrate having a diameter of 200 mm, and then a patterned wafer having a silicon oxide film of 2000 nm formed thereon by TEOS-plasma CVD is manufactured. To do. Set the pattern wafer on the holder to which the suction pad for mounting the substrate to be held is pasted, place the holder with the insulating film side down on the surface plate to which the polishing pad made of porous urethane resin is pasted, and further process The load was set to 300 gf / cm ₂ . While the above cerium oxide abrasive (solid content: 1% by weight) was dropped on the surface plate at a speed of 200 cc / min, the surface plate and the wafer were rotated at 50 rpm for 2 minutes to polish the insulating film. The polished wafer was thoroughly washed with pure water and then dried. Similarly, the pattern wafer was polished at a polishing time of 3, 4, 5, and 6 minutes. Using an optical interference type film thickness measuring device, the film thickness difference before and after polishing was measured, and the polishing rate was calculated. Polishing speed ratios R5 / R1 and R3 / of the polishing rate R1 of the Line portion with a Line / Space width of 1 mm, the polishing rate R3 of the Line portion with a Line / Space width of 3 mm, and the polishing rate R5 of the Line portion with a Line / Space width of 5 mm. The value of R1 increased with the polishing time during the polishing time of 2 to 4 minutes, and was almost constant at the polishing time of 4 to 6 minutes. When the polishing time is 4 minutes when the pattern width dependency of the polishing rate is constant, the polishing rate R1 of the Line portion with a Line / Space width of 1 mm is 344 nm / min (polishing amount 1377 nm), and the Line portion with a Line / Space width of 3 mm is used. The polishing rate R3 is 335 nm / min (polishing amount 1338 nm), the polishing rate R5 of the Line portion having a Line / Space width of 5 mm is 315 nm / min (polishing amount 1259 nm), and the polishing rate ratios R5 / R1 and R3 / R1 are respectively 0.91 and 0.97. In addition, the polishing amount of the Line portion of each Line / Space width when the polishing time was 5 minutes and 6 minutes was almost the same as that in the case of 4 minutes, and it was found that polishing was hardly progressing after 4 minutes.

Example 2
(Production of cerium oxide particles)
About 1 kg of yellowish white powder was obtained by putting 2 kg of cerium carbonate hydrate in a platinum container and firing in air at 700 ° C. for 2 hours. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. The fired powder particle size 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 cerium oxide surrounded by the grain boundaries was measured, the median value of the volume distribution was 30 nm, and the maximum value was 80 nm. 1 kg of cerium oxide powder was pulverized. When the pulverized particles were observed with a scanning electron microscope, a large pulverized residual particle of 2 to 4 microns and a pulverized residual particle of 0.5 to 1.2 μm were mixed in addition to a small particle having the same size as the primary particle size. It was.

(Preparation of cerium oxide slurry)
1 kg of the cerium oxide particles prepared above, 23 g of an aqueous polyacrylic acid ammonium salt solution (40% by weight), and 8977 g of deionized water were mixed and subjected to ultrasonic dispersion for 10 minutes while stirring. The obtained slurry was filtered, and further deionized water was added thereto to add 5 wt. % Abrasive was obtained. The slurry pH was 8.3. 600 g of the above cerium oxide slurry (solid content: 5 wt%), 210 g of a polyacrylic acid (100%) ammonium salt aqueous solution (40 wt%) having a pH of 6.5 and a molecular weight of 15,000 as a surfactant and 2190 g of deionized water The mixture was mixed to prepare a cerium oxide abrasive (solid content: 1% by weight) to which a surfactant was added. The abrasive pH was 6.8, and the viscosity calculated from the measured values of the Ubbelohde viscometer and the specific gravity meter was 1.50 mPa · s. Further, in order to measure the particles in the abrasive with a laser diffraction particle size distribution meter, the particles were measured at a suitable concentration, and as a result, the median particle diameter was 350 nm.

(Polishing the insulating film layer)
An Al wiring Line portion having a Line / Space width of 0.05 to 5 mm and a height of 1000 nm is formed on a Si substrate having a diameter of 200 mm, and then a patterned wafer having a silicon oxide film of 2000 nm formed thereon by TEOS-plasma CVD is manufactured. To do. Set the pattern wafer on the holder to which the suction pad for mounting the substrate to be held is pasted, place the holder with the insulating film side down on the surface plate to which the polishing pad made of porous urethane resin is pasted, and further process the load was set to 300g / cm ^2. While the cerium oxide slurry (solid content: 1% by weight) was dropped onto the surface plate at a speed of 200 cc / min, the surface plate and the wafer were rotated at 50 rpm for 2 minutes to polish the insulating film. The polished wafer was thoroughly washed with pure water and then dried. Similarly, the pattern wafer was polished at a polishing time of 3, 4, 5, and 6 minutes. Using an optical interference type film thickness measuring device, the film thickness difference before and after polishing was measured, and the polishing rate was calculated. Polishing speed ratios R5 / R1 and R3 / of the polishing rate R1 of the Line portion with a Line / Space width of 1 mm, the polishing rate R3 of the Line portion with a Line / Space width of 3 mm, and the polishing rate R5 of the Line portion with a Line / Space width of 5 mm. The value of R1 increased with the polishing time during the polishing time of 2 to 4 minutes, and was almost constant at the polishing time of 4 to 6 minutes. When the polishing time is 4 minutes when the pattern width dependency of the polishing rate is constant, the polishing rate R1 of the Line portion with the Line / Space width of 1 mm is 307 nm / min (polishing amount 1229 nm), and the Line portion with the Line / Space width of 3 mm is The polishing rate R3 is 257 nm / min (polishing amount 1027 nm), the polishing rate R5 of the Line portion having a Line / Space width of 5 mm is 200 nm / min (polishing amount 801 nm), and the polishing rate ratios R5 / R1 and R3 / R1 are respectively 0.65 and 0.84. In addition, the polishing amount of the Line portion of each Line / Space width when the polishing time was 5 minutes and 6 minutes was almost the same as that in the case of 4 minutes, and it was found that polishing was hardly progressing after 4 minutes.

Claims (9)

  A polishing agent comprising cerium oxide particles, water, and ammonium polyacrylate, wherein the pH and viscosity (mPa · s) of the polishing agent are an (x, y) coordinate system in which the pH is the x coordinate and the viscosity is the y coordinate. , Point A (5.5, 1.0), point B (5.5, 2.5), point C (9.0, 2.5), point D (8.5, 1.0) An abrasive characterized by being in the range of a region surrounded by four points.   The abrasive according to claim 1, wherein the primary particle diameter of the cerium oxide particles is 5 to 600 nm, and the median particle diameter is 100 to 2000 nm.   The polishing agent according to claim 1 or 2, wherein the polyacrylic acid ammonium salt has a molecular weight of 100 to 50,000.   The abrasive | polishing agent of Claim 3 whose molecular weight of polyacrylic acid ammonium salt is 2000-20000.   The abrasive according to claim 4, wherein the ammonium polyacrylate has a molecular weight of 5,000 to 15,000.   The abrasive | polishing agent in any one of Claims 1-5 which is an abrasive | polishing agent obtained by mixing the cerium oxide slurry containing a cerium oxide particle, water, and a dispersing agent, and the addition liquid containing polyacrylic acid ammonium salt. .   A method for polishing a substrate, comprising polishing a predetermined substrate with the abrasive according to claim 1.   The method for polishing a substrate according to claim 7, wherein the predetermined substrate is a semiconductor chip on which at least a silicon oxide film is formed. In the step of polishing the film to be polished by relatively moving the polishing platen and the substrate while pressing the substrate having the film to be polished against the polishing cloth while supplying the polishing agent on the polishing cloth of the polishing surface plate, polishing method of substrate according to claim 7 or claim 8 pushing pressure on the polishing cloth substrate is 100~1000gf / cm ² with a film to be polished.