WO2005029563A1 - Polishing composition for silicon wafer and polishing method - Google Patents

Abstract

A polishing composition for polishing the surface or peripheral portion of a silicon wafer or such surface or peripheral portion covered with an oxide film or a nitride film is disclosed which enables high-speed polishing and prevents spots caused by etching in a non-processed portion. Also disclosed is a polishing method using such a polishing composition. A polishing composition is characterized by containing water, silicon oxide particles, and a surfactant and being adjusting to have a pH of 8.7-12.0 using an alkaline compound. This polishing compound not only enables high-speed polishing but also prevents etching of non-processed portions. In particular, this polishing compound prevents spots which would be formed around the suction jig for holding a wafer locally in portions where the polishing compound is in contact with the jig or surrounding portions.

Description

 Specification

 Silicon wafer polishing composition and polishing method

 Technical field

 The present invention relates to a polishing composition for polishing a surface or an outer peripheral portion of a silicon wafer or a surface or an outer peripheral portion of a silicon wafer whose surface is coated with an oxide film or a nitride film, and the polishing composition. The present invention relates to a polishing method for polishing a surface or an outer peripheral portion of a silicon wafer to be polished using a polishing composition.

 Background art

 [0002] In a mirror polishing method for a silicon wafer, a polishing composition containing a polishing cannonball and a chemical etching agent is used. In recent years, with the increasing integration of electronic circuits and the size of the wafer itself, it has become essential to highly flatten the surfaces of silicon wafers and semiconductor device substrates. Furthermore, in order to improve the production efficiency, not only the processing speed is V, but also the polishing force is applied, and the etching is not caused on the parts (non-forced parts)! /, And! /, A polishing composition is desired. When the etching at the non-rolled area is severe, it can be visually confirmed on the silicon wafer and is called "stain". In particular, it occurs locally where the abrasive is in contact around the suction jig for holding the wafer. It has been pointed out that stains are one of the causes of a decrease in product yield, which is caused by force that significantly impairs the appearance of mirror-finished wafers.

 [0003] Hitherto, as a polishing composition for polishing a silicon wafer, there have been proposed a large number of compositions containing so-called colloidal silica, which is a suspension of silicon oxide or a hydrate thereof in a colloidal state. Have been. For example, Patent Document 1 proposes silica sol and silica gel as abrasives.

On the other hand, very many proposals have also been made regarding the liquid composition. Patent Document 2 discloses that the polishing rate is increased by setting the pH of the suspension within the range of 10.5-12.5. Patent Document 3 discloses that amines are added to a polishing composition. Patent Document 4 discloses a polishing composition comprising water, colloidal silica, a chelating agent or a water-soluble polymer having a molecular weight of 5000 or more, and an alkaline conjugate. Patent Literature 5 discloses a polishing composition comprising water, colloidal silica, a water-soluble polymer having a molecular weight of 100,000 or more, and a water-soluble salt.

[0004] These disclosed methods increase the dispersibility of an abrasive by adding various additives to slurry @ colloidal silica in which fine silica particles are dispersed in an alkaline mother liquor, A force that stabilizes the force or increases the processing speed. Polishing performance required at present, that is, a high-speed and stable polishing speed, good cleanability after processing, and a flat polished surface However, it does not satisfy all the conditions that no etching occurs on the non-dried part.

 There have also been some proposals for the use of surfactants. Patent Document 6 discloses a non-ionic surfactant having an HLB value of 13 or more and less than 20, Patent Document 7 discloses a nonionic surfactant having an ester group-containing HLB value of 12 or less, and Patent Document 8 discloses an anionic surfactant. The use force of the alkali is not described in any of the colloidal silicas.Although the addition of an alkaline ligating compound other than the alkali stabilizer is not performed, stains due to etching are not generated. The polishing rate becomes extremely low.

[0005] Patent Document 9 discloses that a weak acid and a strong base, a strong acid and a weak base, or a weak acid and a weak acid are used by using a weak acid and Z or a weak base having a logarithm of the reciprocal of the acid dissociation constant of 8.0 to 12.0. colloidal Darushirika composition a buffer solution having a buffering action _P H by adding those of any combination of bases is disclosed. The use of a buffer solution provides a stable polishing composition with a small change in pH due to a change in external conditions and a small change even in repeated use. There was a need for further improvements that do not satisfy the conditions that etching does not occur.

 [0006] Patent Document 10 describes a composition which is a buffer solution composition and is free from stains by adding alcohols. However, this is still not a satisfactory polishing composition to our knowledge.

 Patent Document 1: US Patent No. 3170273

 Patent Document 2: U.S. Pat.No. 3,328,141

 Patent document 3: U.S. Pat.No. 4,169,337

Patent Document 4: JP-A-63-272460 Patent Document 5: JP-A-2-158684

 Patent Document 6: JP-A-4-291722

 Patent Document 7: JP-A-2000-114212

 Patent Document 8: JP-A-4-291723

 Patent Document 9: JP-A-11 302634

 Patent Document 10: JP-A-2000-80350

 Disclosure of the invention

 Problems to be solved by the invention

 [0008] Accordingly, an object of the present invention is to obtain a flat polished surface having a high-speed and stable polishing rate and good cleanability after processing in view of the problems of the conventional polishing composition. It is an object of the present invention to provide a polishing composition which can be used and does not cause etching on non-processed portions. Means for solving the problem

 Under vigorous circumstances, the present inventors have conducted intensive studies, and as a result, have found that a polishing composition having a specific composition can solve the above-mentioned problems, and have completed the present invention. The first invention of the present invention is directed to a silicon wafer containing water, silicon oxide particles and a surfactant, and adjusted to a pH of 8.7 to 12.0 by an alkaline conjugate. It is a polishing composition for polishing.

 A second invention of the present invention is a polishing composition for silicon wafers, further comprising a silicone defoamer in the first invention.

 [0010] The silicon oxide particles are preferably a colloid solution having an average primary particle diameter of 10 to 200 nm and a concentration of 125 wt%. Further, there are two types of silicon oxide particles: (a) particles having an average primary particle diameter of 40 to 60 nm, and (b) particles having an average primary particle diameter of 60 to 100 nm, and their weight ratio (a: b) is 1: 0.05— The ratio is more preferably 1: 0.3.

The surfactant is an anionic surfactant or a nonionic surfactant, and the concentration of the surfactant is preferably 0.001 to 10 mmol ZKg. Preferably, the ionic surfactant is a sulfonate or a fatty acid salt, and the nonionic surfactant is preferably polyethylene glycol. The alkaline compound is preferably at least one selected from the group consisting of alkali metal, ammonia, quaternary ammonium, and amines. And the cations forming the buffer solution are at least one selected from potassium ions, sodium ions, and tetramethylammonium ions. It is further preferred that at least one of carbonate ions and bicarbonate ions is used.

[0011] A third invention of the present invention is a polishing composition for silicon wafers, further comprising a water-soluble polymer in the first invention or the second invention.

 The concentration of the water-soluble polymer is preferably 0.001 to 1 mmol ZKg, and the molecular weight is preferably 5000 or less. Further, the water-soluble polymer is preferably at least one selected from cellulose derivatives, polyvinyl alcohol and polyethylene glycol.

A fourth invention of the present invention is a method for polishing a surface or an outer peripheral portion of a silicon wafer to be polished by using the polishing composition for a silicon wafer according to the first to third inventions. I will.

 According to a fifth aspect of the present invention, the polishing composition for a silicon wafer according to the first to third aspects is placed on a surface plate on which a polishing cloth is spread, and while pressing and rotating the object. This is a method of polishing the flat surface of the object to be polished while supplying.

 According to a sixth aspect of the present invention, an outer peripheral portion of an object to be polished is brought into contact with the polishing member by using a polishing apparatus having a polishing member having a polishing cloth adhered to a surface thereof. A method for polishing an outer peripheral portion of an object to be polished while supplying the polishing composition for a silicon wafer according to the first to third inventions to an outer peripheral portion while rotating one or both of them.

 BEST MODE FOR CARRYING OUT THE INVENTION

<Polishing composition>

The present invention relates to a polishing composition for a silicon wafer, comprising water, silicon oxide particles and a surfactant, and adjusted to a pH of 8.7 to 12.0 with an alkaline compound. It is. The silicon wafer referred to here is Bare Ueno, an epitaxy Refers to wafers, wafers with oxide films, wafers with nitride films, SOI wafers, and wafers for semiconductor processing for CMP processing.

 [0014] <Silicon silicon particles>

 The silicon oxide particles are divided into two parts, a gas-phase silicon oxide and a liquid-phase silicon oxide, from the manufacturing method. Slurries in which fumed silica is dispersed in an aqueous medium have been widely used for semiconductor polishing as gas phase silicon dioxide, but these particles have a broad particle size distribution and are further aggregated to form secondary particles. A typical polydisperse system. The liquid-phase silicon oxide has a high purity colloidal silica obtained by a common colloidal silica made from water glass and a hydrolysis method of an organic silicon compound. The colloidal solution of silicon dioxide particles used in the present invention is this general colloidal silica and high-purity colloidal silica. In particular, general colloidal silica using water glass as a raw material is inexpensive and is suitably used because the polishing rate is high.

 The silicon oxide particles contained in the colloid solution used in the present invention are substantially monodispersed silicon oxide fine particles having an average primary particle diameter of 10 to 20 Onm, preferably 40 to 100 nm. Is used. Here, the average primary particle diameter is a value obtained by converting a specific surface area measured by a nitrogen adsorption BET method into a diameter of a spherical particle. BET method for colloidal silica Particle size (specific surface area) is described in THE CHEMISTRY OF SILICA Solubility,

Polymerizatoin, Colloid and Surface Properties, and Biochemistry (P344-354, RALPH K. ILER, A Wiley-Interscience Publication JOHN WILEY & SONS P)! The calculation formula is particle diameter (nm) = 2720Z specific surface area (m ² Zg).

[0016] The use of particles having an average primary particle diameter of less than 10 nm of the silicon oxide particles reduces the stability of the polishing composition, in which the colloid solution easily aggregates when the electrolyte concentration of the buffer component is increased, Further, the cleaning property of particles adhered to the polished silicon wafer surface is reduced. Use of particles having an average primary particle diameter of 200 nm or more is not preferable because it is close to the wiring width in device polishing. In particular, when used repeatedly for polishing a plurality of wafers, particles having a force of 200 nm or more that require filtration and removal of polishing debris and pad debris cannot be separated from the debris. Also, in other applications, coarse particles settle, making it difficult to ensure the stability of the product over time, and it is disadvantageous in terms of price.

[0017] From such a meaning, it is a substantially single particle size that does not include fine particles or coarse particles. It is preferred to use monodisperse particles. In the present invention, the substantial monodisperse means the number average diameter (Dn) and the volume average diameter measured by a general colloid particle diameter measurement method such as electron microscopy, centrifugal sedimentation, and laser light scattering. (Dv) or the ratio of the weight average diameter (Dw) (DvZ Dn) or (DwZDn) is defined as being in the range of 1.00-1.50. Examples of monodisperse colloidal silica include “Silica Doll” manufactured by Nippon Dani Gaku Kogyo Co., Ltd., “TCSOL703” manufactured by Tama Chemical Industry Co., Ltd., and “Ultra High Purity Colloidal Silica PL-7” manufactured by Fuso Dani Gaku Kogyo Co., Ltd. is there. Dispersions that are not substantially monodisperse are described as polydisperse. Polydisperse colloidal silica is more preferred because the polishing rate can be increased. Examples of polydisperse colloidal silica include “Syton”, “Mazin” and “Ascend” of DuPontAirProducts NanoMaterials LLC.

 [0018] The silicon oxide particles are particularly preferably colloidal silica having a particle force of two types, large and small. This is obtained by mixing silicon oxide particles having a small average primary particle diameter and silicon oxide particles having a large average primary particle diameter. In particular, the applicant of the present invention filed earlier (Japanese Patent Application No. 2003-127626) clearly shows that silicon oxide particles have an average primary particle diameter of (a) 40 to 60 nm and (b) 60 to 100 nm. Colloidal silica, which is two types of particles that can be distinguished and has a weight ratio of 1: 0.05-1: 0.3, is most preferable in consideration of economy.

 [0019] It is important that the concentration of silicon oxide be 125% by weight during actual polishing, and a more preferable range is 3 to 15% by weight for surface polishing of a silicon wafer. Then it is 11-15% by weight. If the concentration of silicon oxide at the time of polishing is less than 1% by weight, the polishing speed becomes low, which is not practical. If the silicon oxide concentration during polishing increases, the polishing speed itself increases, but if it exceeds about 25% by weight, contamination of the wafer increases, and the cleanability deteriorates.

 In general, it is convenient to prepare a high-concentration composition having a silicon oxide concentration of 25 to 65% and dilute it with water or a mixture of water and an organic solvent. It is. The high-concentration composition lacks any of the essential components other than silicon oxide, and is added at the time of dilution.

 [0021] <Surfactant>

In the present invention, it is necessary that one of the components contains a surfactant. interface As the surfactant, any of a cationic surfactant, an anionic surfactant, a nonionic surfactant and an amphoteric surfactant can be used. Polymeric surfactants Although glycols can be used, anionic surfactants or nonionic surfactants are preferred. The ionic surfactant can be a sulfonate or a fatty acid salt, an alkyl ether carboxylate, an alkyl ether sulfate or the like, but is preferably a sulfonic acid salt or a fatty acid salt. As the sulfonic acid salt, linear alkylbenzene sulfonic acid and its salt, alpha olefin sulfonic acid and its salt are preferred, and dodecylbenzene sulfonic acid salt is most preferred. The fatty acid salt is preferably one or more selected from lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid. It is convenient to use water-soluble salts such as, for example, sodium stearate. As the non-one type surfactant, polyoxyalkylene glycols, fatty acid esters, alkylamine ethylene oxide adducts, glycols or polymer surfactants can be used. Among them, polyoxyethylene alkyl ether and polyethylene blend alcohol are preferred, but polyethylene glycol is most preferred.

 [0022] The concentration of the surfactant is preferably 0.01 to 10 mmol / Kg. Less than 0.01 mmol ZKg has no effect of preventing etching. Even if more than 10 mmol ZKg is added, the effect does not change and is unnecessary. As a method of using the fatty acid, it is convenient to use a water-soluble salt such as an alkali metal salt of the fatty acid, for example, sodium stearate. The entire amount of the fatty acid blended in the composition is in a dissolved state, and it is not necessary to dissolve a part of the fatty acid in the order of ppm, and the remainder may be in the form of an associated micelle.

 <Alkaline compound>

 In the present invention, it is important that the pH of the polishing composition is adjusted to the range of 8.7 to 12.0 by the alkaline compound. More preferably, the pH is in the range of 9.5-10.7. When the pH is 8.7 or less, the polishing rate is remarkably reduced and is out of the practical range. When the pH is more than 12.0, the contamination on the wafer increases, and the cleaning property is deteriorated.

As the alkaline compound, one or more of alkali metal, ammonia, quaternary ammonium and amines are preferred. be able to.

 [0024] Also, the pH should not easily change due to possible changes in external conditions such as friction, heat, contact with outside air, or mixing with other components. In the present invention, it is preferable that the polishing composition solution itself be a liquid having a small variation in pH with respect to a change in external conditions, a V, a strong buffering action, and a liquid! ,.

 Examples of the ions forming the buffer solution of the present invention include anions, such as strong acids such as hydrochloric acid, nitric acid, hydrofluoric acid, and sulfuric acid, and weak acids such as boric acid, carbonic acid, phosphoric acid, and water-soluble organic acids. Or a mixture thereof. Particularly preferred are carbonate ions or bicarbonate ions. Examples of the cations include alkali metal ions such as sodium and potassium, ammonium ions such as ammonium, choline, and tetramethylammonium, and hydroxyl ions such as amine ions such as ethylenediamine and piperazine. It shows alkalinity in pairs, and may be a mixture thereof. Particularly, potassium ion, tetramethylammonium, or a mixture thereof is preferable. The buffer solution described in the present invention refers to a solution formed by a combination of the above-mentioned ions, added as an acid, an alkali, or a salt, in which a state of dissociation as an ion and a state of an undissociated state coexist. It is characterized by little change in pH even when an acid or base is mixed.

[0025] <Silicon defoamer>

 Surfactants, particularly anionic surfactants, are liable to cause the negative phenomenon of foaming depending on how they are used. To control this, an antifoaming agent, which is usually used in combination with an antifoaming agent, is extremely effective. Silicone antifoaming agents include oil type, modified oil type, solution type, powder type and emulsion type.The modified oil type and emulsion type can be well dispersed in a colloid solution, but the emulsion type is the most effective. But high sustainability.販 As a commercial product, for example, there is Shin-Etsu Silicone KM grade manufactured by Shin-Etsu Dangaku Kogyo Co., Ltd. The amount of defoamer used must be determined as appropriate according to the amount of surfactant. Lppm in products-lOOOOppm is appropriate.

[0026] <Water-soluble polymer>

In the present invention, the effect can be enhanced by blending a water-soluble polymer. As mentioned above, water-soluble polymers with a molecular weight of 5,000 or more and water-soluble polymers with a molecular weight of 100,000 or more are said to function to reduce metal contamination and improve flatness of wafers. When molecules are used, there is a disadvantage that only a small amount can be blended so as not to increase the viscosity of the polishing slurry too much. It is preferable to use a water-soluble polymer having an average molecular weight of 5,000 or less, preferably 500 to 3,000, in an amount of 0.001 to 1 mmol ZKg. Examples of the water-soluble polymer include polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, maleic acid-butyl copolymer, xanthan gum, and cellulose derivatives. -Alcohol, polyethylene glycol power It is preferable to use at least one selected from the group. As the cellulose derivative, hydroxymethyl cellulose, which can be used such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and carboxymethylcellulose, is preferred. Polyethylene glycol having a molecular weight of 5000 or less is more preferred.

 [0027] In order to improve the physical properties of the polishing composition of the present invention, a surfactant, an antifoaming agent, a bactericide, a wetting agent, a water-miscible organic solvent, an antifreezing agent, an antifreezing agent, and the like other than those described above are used in combination. can do.

 [0028] <Adjustment method>

 The method for preparing the polishing composition of the present invention will be described. The above-mentioned alkali conjugate is added to a colloidal solution comprising water and silicon oxide particles and having a silicon oxide particle concentration of 15 to 65% by weight. When a buffer solution is used as the alkaline conjugate, a buffer solution composed of the aforementioned ionic species can be prepared and added in advance.

 Subsequently, a solution or a mixture thereof containing water and salts and containing 0.01 to 10 millimol ZKg of a surfactant is prepared, and the solution is diluted with the solution to obtain a polishing composition. Instead of water, a mixture of water and an organic solvent can be used.

[0029] <Polishing method>

Using the polishing composition of the present invention, the surface or outer peripheral portion of a silicon wafer to be polished can be polished. The surface is polished by placing a silicon wafer to be polished on a polishing machine that has a rotatable platen with a polishing cloth attached to both upper and lower surfaces or one surface. A method in which polishing is performed while pressing and rotating the platen and / or the workpiece while supplying the polishing composition while rotating both or one of the platen and the workpiece is applicable. As the polishing cloth, a commonly used one such as a synthetic resin foam, synthetic leather or non-woven fabric can be used. Various polishing apparatuses, such as a single rotation type, an orbital motion type, and a linear motion type, have been proposed for planar polishing, and any of these devices can be used. The outer peripheral portion is polished by pressing the outer peripheral portion of a workpiece such as a wafer against a polishing member having a drum-shaped polishing member having a polishing cloth adhered to the surface or a polishing tool having an arc-shaped work surface. A method of polishing the outer peripheral portion of the workpiece while supplying the above-mentioned polishing composition while rotating the member and Z or the workpiece is applicable. For polishing the outer peripheral portion, a polishing apparatus described in JP-A-07-314304, JP-A-2000-317788, and JP-A-2002-36079 can be used as appropriate. Particularly, recently, a method of simultaneously polishing the vertical end surface and the inclined surface of the outer peripheral portion has been proposed and is preferable. Further, a method in which the outer peripheral portion is polished to the upper and lower flat surfaces is also preferable. Without limitation, any device conventionally used can be used.

Example

 Next, the polishing composition of the present invention and a polishing method using the polishing composition of the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not particularly limited thereto. The colloidal silica used in the examples is “Silica Doll 30” (average particle diameter 15 nm), “Silica Doll 40” (average particle diameter 20 nm), “Silica Doll 30G” (average particle diameter 40 nm), and “Silidol 40G”. —80 ”(average particle size 80 nm) (both manufactured by Nippon Dani Gaku Kogyo Co., Ltd., trade name).

A commercially available 20% aqueous solution was used as hydroxylamine tetramethymer ammonium (hereinafter abbreviated as TMAH). Potassium hydrogen carbonate and potassium hydroxide used special grade reagents. Cetyltrimethylammonium-dimethyl chloride, sodium laurate, sodium stearate, sodium dodecylbenzenesulfonate and polyethylene glycol having a molecular weight of 1,000 were used by preparing reagents in an aqueous solution, and other surfactants were commercially available. Hydroxyethylcellulose having a molecular weight of 300,000 was used by preparing a 1% aqueous solution of the reagent. Defoamers include Shin-Etsu Silicone Silicone Emulsion, Shin-Etsu Silicone Co., Ltd. KM73A (active ingredient 22.5%) was used.

[0031] The polishing composition is mixed with the above-mentioned colloidal silica under stirring with an aqueous solution obtained by dissolving potassium hydrogen carbonate and sodium hydroxide in a TMAH aqueous solution or a diluted TMAH aqueous solution.

In V, a surfactant aqueous solution and a water-soluble polymer aqueous solution were added and mixed. This polishing composition was diluted immediately before the polishing test so as to have the composition shown in Table 1.

[Examples 1-3 and Comparative Example 1]

 An example of surface polishing of a silicon wafer will be described. Using the polishing composition adjusted to have the composition shown in Table 1, mirror polishing was performed under the following polishing conditions.

 Polishing machine: Speed Fam Co., Ltd., SH-24 single-side processing machine

 Wafer holding method: vacuum suction method

 Carrier chuck vacuum degree: 50mmHg

 Platen rotation speed: 70RPM

 Pressure plate rotation speed: 50RPM

 Polishing cloth: SUBA400 (Made by Dale Yutta)

Surface pressure: 400 g / cm ² Polishing composition flow rate: 60MlZ min

 Polishing time: 3 minutes

 Workpiece: 6 inch silicon wafer with oxide film 1200nm

 Cleaning after processing: 30 seconds with deionized water

 The pH of the polishing composition was measured using a pH meter. In the evaluation of the polished surface, the condition of the stain was visually observed under a condensing lamp. The polishing rate was calculated from the weight difference between the silicon wafers before and after polishing and converted to μmZ.

[0033] The results are shown in Table 1.

 Examples 1 to 3 show examples of the use of two types of a-on surfactants and a non-on (polymer) surfactant, but in each case, no stain was observed. In Comparative Example 1, spots were observed as ring-shaped cloudy portions on the wafer suction fixing chuck portion on the back surface.

 In Example 1, a slight bubbling of the abrasive composition was observed. The foam disappeared immediately due to the effect of the addition of a trace amount of the defoaming agent.

[0034] [Table 1] Example Comparative example

 1 2 3 1

 Particle size (nm) 15 20 20 15

 Concentration (wt%) 5 5 5 5 Alcohol agent TMAH 0.5 0.11 0.5 (wt%) KOH 0.2

KHC0 ₃ 0.13

 Surfactant DBS 0.1

 (Mmol / kg) STA 0.1

 PEG 0.1

 Defoamer (ppm) 30

 H 11.6 11.3 10.2 11.6 Polishing rate (m / min) 0.19 0.20 0.19 0.20 Stain evaluation None None None Chuck

 Many

[0035] DBS: Sodium dodecylbenzenesulfonate

 STA: sodium stearate

 PEG: polyethylene glycol (molecular weight 1000)

[Example 4-1 7 and Comparative Example 2]

 An example of polishing an outer peripheral end face of a silicon wafer will be described. Using the polishing composition adjusted to have the composition shown in Table 2, mirror polishing was performed under the following polishing conditions.

 Polishing equipment: Speed Fam Co., Ltd., EP-IV type end face processing machine

 Wafer holding method: vacuum suction method

 Carrier chuck vacuum degree: 20mmHg

 Wafer tilt angle: 45 degrees

 Drum rotation speed: 800RPM

 Wafer rotation speed: 70 seconds ZREV

 Wafer rotation speed: 4 times Z sheets

 Polishing cloth: DRP—II (Speed Fam)

 Load: 2.5Kg

 Polishing composition flow rate: 250mlZ min

Workpiece: 8 inch Silicon Ueno, The pH of the polishing composition was measured using a pH meter. In the evaluation of the polished surface, the condition of the stain was visually observed under a condensing lamp. The polishing rate was calculated from the difference in weight between the silicon wafers before and after polishing and was converted to mgZ.

[0037] The results are shown in Table 2.

 Examples 417 show examples of the use of two types of a-on surfactants and a non-on (polymer) surfactant, but in all cases, no stain was observed. In Comparative Example 2, spots were observed as ring-shaped cloudy portions on the wafer suction fixing chuck portion on the back surface.

 In Examples 4 and 7, slight bubbling of the abrasive composition was observed, but the foam disappeared immediately due to the effect of the addition of a small amount of the antifoaming agent.

[Table 2]

[0039] POEAS: polyoxyethylene alkyl sulfate sodium salt

 OLA: Oleic acid amide

 PEG: polyethylene glycol (molecular weight 1000)

 HEC: hydroxyethyl cellulose (molecular weight 300000)

 [0040] [Reference Example 1-2]

A reference example of polishing the outer peripheral end face of a silicon wafer using the polishing composition liquid of Example 5 and Example 7 in circulation is shown. Using the polishing composition adjusted to have the composition shown in Table 2, the polishing conditions were the same as in Example 417. A polishing experiment was performed, and the pH and polishing rate of the polishing composition were measured each time.

 Table 3 shows the results.

 The pH of Reference Example 2 showed little change up to the tenth sheet compared to Reference Example 1, and the polishing rate was stable and high. In Reference Example 1, after the fourth sheet, insufficient polishing became remarkable, and it was strong enough to withstand cyclic use.

 [Table 3]

Industrial applicability

 As described above, the present invention provides a polishing composition and a polishing composition for polishing a surface or an outer peripheral portion of a silicon wafer or a surface or an outer peripheral portion of a silicon wafer whose surface is coated with an oxide film or a nitride film. The present invention relates to a polishing method for polishing a surface or an outer peripheral portion of a silicon wafer which is an object to be polished using the polishing composition, and the polishing composition for a silicon wafer of the present invention has a high processing speed. In addition, there is an effect that etching is not caused on a non-processed portion, and a stain generated locally at a portion where an abrasive is in contact with a peripheral portion of a suction jig for holding a wafer is exhibited.

Claims

The scope of the claims

 [I] A polishing composition for silicon wafers, comprising water, silicon oxide particles and a surfactant, and adjusted to a pH of 8.7 to 12.0 with an alkaline conjugate.

 [2] The polishing composition according to claim 1, further comprising a silicone antifoaming agent.

 [3] The polishing composition according to claim 1, wherein the silicon oxide particles are a colloid solution having an average primary particle diameter of 10 to 200 nm and a concentration of 125% by weight.

[4] There are two types of silicon oxide particles: (a) particles having an average primary particle diameter of 40-60 nm and (b) particles having an average primary particle diameter of 60-100 nm, and their weight ratio (a: b) is 1: 0.05. — The polishing composition according to claim 3, wherein the ratio is 1: 0.3.

[5] The polishing composition according to claim 1, wherein the surfactant is an anionic surfactant or a nonionic surfactant, and the concentration of the surfactant is 0.001 to 10 mmol ZKg. object.

 6. The polishing composition according to claim 5, wherein the ionic surfactant is a sulfonate or a fatty acid salt.

 [7] The polishing composition according to claim 5, wherein the non-ionic surfactant is polyethylene glycol.

 [8] The polishing composition according to any one of claims 1 and 2, wherein the alkaline compound is at least one selected from the group consisting of an alkali metal, ammonia, a quaternary ammonium and an amine. object.

 [9] The alkaline conjugate is composed of ionic species that form a buffer solution between pH 9.5 and 10.7, and the cations that form the buffer solution are potassium ions, sodium ions, and tetramethylammonium. 3. The polishing composition according to claim 1, wherein the polishing composition is at least one member selected from the group consisting of platinum ions, and the anion is at least one of carbonate ions and hydrogen carbonate ions. 4.

[10] The polishing composition according to any one of claims 1 to 9, further comprising a water-soluble polymer.

11. The polishing composition according to claim 10, wherein the concentration of the water-soluble polymer is 0.001 to 1 mmol ZKg.

12. The polishing composition according to claim 10, wherein the water-soluble polymer has a molecular weight of 5,000 or less.

13. The polishing composition according to claim 10, wherein the water-soluble polymer is at least one selected from the group consisting of cellulose derivatives, polybutyl alcohol, and polyethylene glycol.

[14] A method for polishing a surface or an outer peripheral portion of a silicon wafer to be polished using the polishing composition according to claim 1.

[15] A method of placing an object to be polished on a surface plate on which a polishing cloth is spread, and polishing a flat surface of the object to be polished while supplying the polishing composition according to claim 1 while rotating while pressing.

[16] Using a polishing apparatus having a polishing member having a polishing cloth adhered to the surface thereof, the outer peripheral portion of the object to be polished is brought into contact with the polishing member, and either or both of the polishing member and the object to be polished are rotated. 14. A method for polishing an outer peripheral portion of an object to be polished, while supplying the polishing composition according to claim 1 to the outer peripheral portion.