JP2013021292A - Polishing composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition which can be used suitably for polishing an object to be polished having a hydrophobic silicon-containing portion composed of polysilicon, for example, and a hydrophilic silicon-containing portion composed of silicon oxide or silicon nitride, for example.SOLUTION: The polishing composition contains abrasive grains having a silanol group, and a water-soluble polymer. When the polishing composition is left, as it is, for one day under an environment of 25°C temperature, 5000 or more molecules of water-soluble polymer are adsorbed to the abrasive grains per surface area of 1 μm. The examples of the water-soluble polymer include nonionic compounds having a polyoxyalkylene chain, more specifically, polyethyleneglycol, polypropyleneglycol, polyoxyethylene alkylene diglycerylether, polyoxyethylene alkyl ether, and polyoxyethylene sorbitan fatty acid ether.

Description

  The present invention relates to a polishing composition suitable for polishing an object to be polished having a hydrophobic silicon-containing portion and a hydrophilic silicon-containing portion. The present invention also relates to a polishing method and a substrate manufacturing method using the polishing composition.

  Conventionally, in chemical mechanical polishing for forming a metal wiring such as copper of a semiconductor device, a defect called a fang (or seam) has occurred after polishing, and the occurrence of such a defect is prevented. For this purpose, polishing compositions as disclosed in Patent Documents 1 to 5 have been developed.

  On the other hand, plugs (contact plugs) and pads (contact pads) of semiconductor devices are formed from polysilicon (polycrystalline silicon) through chemical mechanical polishing. In forming such plugs and pads, it is generally necessary to simultaneously polish a portion made of silicon oxide or silicon nitride provided in the periphery of the portion made of polysilicon. In this case, a defect called edge over erosion (hereinafter referred to as EOE) may occur after polishing in addition to the fang similar to that at the time of forming the metal wiring. The occurrence of the fang and EOE is considered to be caused by the fact that the polysilicon portion is hydrophobic while the silicon oxide portion or the silicon nitride portion is hydrophilic. Here, the fang means that local erosion occurs at the boundary between the polysilicon portion and the silicon oxide portion or the silicon nitride portion, and is particularly seen on both sides of the relatively wide polysilicon portion. is there. On the other hand, EOE means that local erosion occurs on both sides of a region where polysilicon portions having relatively narrow widths are lined up without much interval. At the same time, in addition to fang and EOE, there is also a problem that the level of the upper surface of the polysilicon portion is lowered due to unnecessary polishing and removal of the polysilicon portion, resulting in dish-shaped dents, that is, dishing. It is difficult to prevent the occurrence of defects such as fang, EOE, dishing and the like when forming plugs and pads made of polysilicon, even if the polishing compositions of Patent Documents 1 to 5 are used.

International Publication No. 2009/005143 JP 2010-41029 A JP 2009-256184 A JP 2006-86462 A International Publication No. 2008/004579

  Accordingly, an object of the present invention is to provide a polishing composition that can be suitably used in applications for polishing a polishing object having a hydrophobic silicon-containing portion and a hydrophilic silicon-containing portion, and for polishing the same. An object of the present invention is to provide a polishing method and a substrate manufacturing method using the composition.

In order to achieve the above object, a first aspect of the present invention provides a polishing composition containing abrasive grains having a silanol group and a water-soluble polymer. When the polishing composition is allowed to stand for one day in an environment at a temperature of 25 ° C., 5000 or more water-soluble polymer molecules are adsorbed per 1 μm ² of the surface area of the abrasive grains.

  The water-soluble polymer is a nonionic compound having a polyoxyalkylene chain, more specifically, polyethylene glycol, polypropylene glycol, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene sorbitan fatty acid ester, Polyoxyethylene glycol fatty acid ester, polyoxyethylene hexitan fatty acid ester, or polyoxyethylene polypropylene alkyl ether is preferable.

The abrasive is preferably silica with an organic acid immobilized thereon.
The polishing composition is used, for example, in an application for polishing an object to be polished having a hydrophobic silicon-containing portion and a hydrophilic silicon-containing portion. The hydrophobic silicon-containing portion is made of, for example, polysilicon.

According to a second aspect of the present invention, there is provided a method for polishing a polishing object having a hydrophobic silicon-containing portion and a hydrophilic silicon-containing portion using the polishing composition of the first aspect.
In the third aspect of the present invention, the polishing composition of the first aspect is used to polish a polishing object having a hydrophobic silicon-containing portion and a hydrophilic silicon-containing portion, whereby a substrate is obtained. A method of manufacturing is provided.

  According to the present invention, a polishing composition that can be suitably used for polishing an object to be polished having a hydrophobic silicon-containing portion and a hydrophilic silicon-containing portion, and the polishing composition are used. A polishing method and a substrate manufacturing method are provided.

Hereinafter, an embodiment of the present invention will be described.
The polishing composition of this embodiment is prepared by mixing abrasive grains and a water-soluble polymer with water. Accordingly, the polishing composition contains abrasive grains and a water-soluble polymer.

  This polishing composition is used, for example, in an application for polishing a polishing object having a hydrophobic silicon-containing portion and a hydrophilic silicon-containing portion, and more specifically, in an application for manufacturing a substrate by polishing the polishing object. Is done. The hydrophobic silicon-containing portion is made of, for example, polysilicon. The hydrophilic silicon-containing portion is made of, for example, silicon oxide or silicon nitride. When such an object to be polished is polished using the polishing composition of the present embodiment, the properties of the abrasive grains are changed by adsorbing a predetermined amount or more of the water-soluble polymer on the surface of the abrasive grains. As a result, the occurrence of fang, EOE and dishing can be suppressed.

  Since the polishing composition of this embodiment is not intended for use in applications for polishing metals in this way, components such as oxidizing agents and metal anticorrosive agents that are usually contained in metal polishing compositions It does not contain.

  The abrasive grains contained in the polishing composition have a silanol group. A typical example of abrasive grains having a silanol group is silica particles, preferably colloidal silica. It is also possible to use those obtained by imparting silanol groups to abrasive grains other than silica particles by surface modification.

  The abrasive grains may be surface-modified. Since ordinary colloidal silica has a zeta potential value close to zero under acidic conditions, silica particles are not electrically repelled with each other under acidic conditions and are likely to agglomerate. On the other hand, abrasive grains whose surfaces are modified so that the zeta potential has a relatively large negative value even under acidic conditions are strongly repelled from each other and dispersed well even under acidic conditions, resulting in storage of the polishing composition. Stability will be improved. Such surface-modified abrasive grains can be obtained, for example, by mixing a metal such as aluminum, titanium or zirconium or an oxide thereof with the abrasive grains and doping the surface of the abrasive grains.

  Alternatively, the surface-modified abrasive grains in the polishing composition may be silica with an organic acid immobilized thereon. Of these, colloidal silica having an organic acid immobilized thereon can be preferably used. The organic acid is immobilized on the colloidal silica by chemically bonding a functional group of the organic acid to the surface of the colloidal silica. If the colloidal silica and the organic acid are simply allowed to coexist, the organic acid is not fixed to the colloidal silica. If sulfonic acid, which is a kind of organic acid, is immobilized on colloidal silica, for example, a method described in “Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups”, Chem. Commun. 246-247 (2003). It can be carried out. Specifically, a silane coupling agent having a thiol group such as 3-mercaptopropyltrimethoxysilane is coupled to colloidal silica, and then the sulfonic acid is immobilized on the surface by oxidizing the thiol group with hydrogen peroxide. The colloidal silica thus obtained can be obtained. Alternatively, if the carboxylic acid is immobilized on colloidal silica, for example, “Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel”, Chemistry Letters, 3, 228- 229 (2000). Specifically, colloidal silica having a carboxylic acid immobilized on the surface can be obtained by irradiating light after coupling a silane coupling agent containing a photoreactive 2-nitrobenzyl ester to colloidal silica. .

  The content of abrasive grains in the polishing composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 1% by mass or more. As the abrasive content increases, the removal rate of the hydrophobic silicon-containing portion and the hydrophilic silicon-containing portion by the polishing composition is advantageously improved.

  The content of abrasive grains in the polishing composition is also preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less. As the content of the abrasive grains decreases, the material cost of the polishing composition can be reduced, and in addition, aggregation of the abrasive grains hardly occurs. Moreover, it is easy to obtain a polished surface with few scratches by polishing an object to be polished using the polishing composition.

  The average primary particle diameter of the abrasive grains is preferably 5 nm or more, more preferably 7 nm or more, and further preferably 10 nm or more. As the average primary particle diameter of the abrasive grains increases, there is an advantage that the removal rate of the hydrophobic silicon-containing portion and the hydrophilic silicon-containing portion by the polishing composition is improved. In addition, the value of the average primary particle diameter of an abrasive grain can be calculated based on the specific surface area of the abrasive grain measured by BET method, for example.

  The average primary particle diameter of the abrasive grains is also preferably 100 nm or less, more preferably 90 nm or less, and still more preferably 80 nm or less. As the average primary particle diameter of the abrasive grains decreases, it is easy to obtain a polished surface with few scratches by polishing the object to be polished using the polishing composition.

  The average secondary particle diameter of the abrasive grains is preferably 150 nm or less, more preferably 120 nm or less, and still more preferably 100 nm or less. The value of the average secondary particle diameter of the abrasive grains can be measured by, for example, a laser light scattering method.

  The average degree of association of the abrasive grains obtained by dividing the value of the average secondary particle diameter of the abrasive grains by the value of the average primary particle diameter is preferably 1.2 or more, more preferably 1.5 or more. . As the average degree of association of the abrasive grains increases, the removal rate of the hydrophobic silicon-containing part and the hydrophilic silicon-containing part by the polishing composition is advantageously improved.

  The average degree of association of the abrasive grains is also preferably 4 or less, more preferably 3 or less, and still more preferably 2 or less. As the average degree of association of the abrasive grains decreases, it is easy to obtain a polished surface with few scratches by polishing the object to be polished using the polishing composition.

The water-soluble polymer contained in the polishing composition adsorbs 5,000 or more molecules per 1 μm ² of the surface area of the abrasive grains when the polishing composition is allowed to stand for one day in an environment of a temperature of 25 ° C. The water-soluble polymer selected from the above types is used. A nonionic compound having a polyoxyalkylene chain can be suitably used because an oxygen atom in the polyoxyalkylene chain hydrogen bonds with a silanol group of the abrasive grains. Specific examples of nonionic compounds having a polyoxyalkylene chain include polyethylene glycol, polypropylene glycol, polyoxyethylene (hereinafter referred to as POE) alkylene diglycerether, POE alkyl ether, POE sorbitan fatty acid ester, POE alkyl phenyl ether, POE. Examples include glycol fatty acid esters, POE hexitan fatty acid esters, POE polypropylene alkyl ethers, and polyoxypropylene / polyoxyethylene block / random copolymers.

  The content of the water-soluble polymer in the polishing composition is preferably 10 ppm by mass or more, more preferably 50 ppm by mass or more, and still more preferably 100 ppm by mass or more. As the content of the water-soluble polymer increases, the water-soluble polymer can be effectively adsorbed on the surface of the abrasive grains, and as a result, the occurrence of fang, EOE and dishing can be further suppressed.

  The content of the water-soluble polymer in the polishing composition is also preferably 100000 ppm by mass or less, more preferably 50000 ppm by mass or less, and still more preferably 10,000 ppm by mass or less. As the content of the water-soluble polymer decreases, the aggregation of abrasive grains in the polishing composition is less likely to occur. As a result, there is an advantage that the storage stability of the polishing composition is improved.

  It is preferable that pH of polishing composition is 12 or less, More preferably, it is 11 or less, More preferably, it is 10 or less. As the pH of the polishing composition decreases, etching of the hydrophobic silicon-containing portion by the polishing composition is less likely to occur, and as a result, the occurrence of dishing can be further suppressed.

  The pH adjuster used as necessary to adjust the pH of the polishing composition to a desired value may be either acid or alkali, and may be any of inorganic and organic compounds. .

According to this embodiment, the following operations and effects can be obtained.
-The polishing composition of this embodiment contains the water-soluble polymer which can adsorb | suck more than predetermined amount on the surface of the abrasive grain which has a silanol group on specific conditions. A change in the properties of the abrasive grains occurs when a predetermined amount or more of the water-soluble polymer is adsorbed on the surface of the abrasive grains. This suppresses the occurrence of fang, EOE and dishing when a polishing object having a hydrophobic silicon-containing portion and a hydrophilic silicon-containing portion is polished using the polishing composition of the present embodiment. It is thought that it can be done. Therefore, the polishing composition of the present embodiment can be suitably used in applications for polishing such a polishing object.

  When the polishing composition has an acidic pH (for example, pH 6 or less) and colloidal silica to which an organic acid is immobilized is used as abrasive grains contained in the polishing composition, the fang, EOE and dishing Occurrence can be further suppressed. The reason is that the zeta potential of colloidal silica immobilized with an organic acid shows a negative value in the acidic pH region, whereas the zeta potential of hydrophobic silicon-containing parts such as polysilicon of the object to be polished is also acidic. This is because a negative value is exhibited in the pH region. That is, in the acidic pH region, the abrasive grains in the polishing composition are electrically repelled with respect to the hydrophobic silicon-containing portion of the object to be polished, and as a result, excessive polishing of the hydrophobic silicon-containing portion by the abrasive grains is performed. Fang, EOE and dishing due to

  When the polishing composition has an acidic pH (for example, pH 6 or lower) and colloidal silica having an organic acid immobilized thereon is used as abrasive grains contained in the polishing composition, polishing with the polishing composition The polishing rate of the hydrophilic silicon-containing part of the object is improved. The reason is that the zeta potential of colloidal silica immobilized with organic acid shows a negative value in the acidic pH region, whereas the zeta potential of hydrophilic silicon-containing parts such as silicon oxide and silicon nitride of the object to be polished. This is because it shows a positive value in an acidic pH region. In other words, in the acidic pH region, the abrasive grains in the polishing composition do not electrically repel the hydrophilic silicon-containing portion of the object to be polished, and as a result, the hydrophilic silicon-containing portion machined by the abrasive grains. Polishing is promoted.

  -When the colloidal silica which fix | immobilized the organic acid is used as an abrasive grain contained in polishing composition, the polishing composition which has the dispersion stability excellent over the long term is obtained. The reason is that colloidal silica in which an organic acid is immobilized tends to have a larger absolute value of zeta potential in the polishing composition than ordinary colloidal silica in which no organic acid is immobilized. . As the absolute value of the zeta potential in the polishing composition increases, electrostatic repulsion between the silica particles increases, so that colloidal silica aggregation due to attractive force due to van der Waals force hardly occurs. For example, in an acidic pH range, the zeta potential of colloidal silica immobilized with an organic acid generally shows a negative value of −15 mV or less, whereas the zeta potential of ordinary colloidal silica shows a value close to zero.

The embodiment may be modified as follows.
-The polishing composition of the said embodiment may contain 2 or more types of water-soluble polymers. In this case, some water-soluble polymers do not necessarily have a property of adsorbing to the surface of the abrasive grains.

-Polishing composition of the said embodiment may further contain well-known additives like a preservative as needed.
The polishing composition of the above embodiment may be a one-component type or a multi-component type including a two-component type.

-The polishing composition of the said embodiment may be prepared by diluting the undiluted | stock solution of polishing composition with water.
Next, examples and comparative examples of the present invention will be described.

  The polishing composition of Comparative Example 1 was prepared by diluting colloidal silica sol with water and adding an organic acid as a pH adjuster to adjust the pH value to 3. The colloidal silica sol was diluted with water, a water-soluble polymer was added thereto, an organic acid was added, and the pH value was adjusted to 3, whereby the polishing compositions of Examples 1 to 6 and Comparative Examples 2 to 5 were used. A product was prepared. Details of the water-soluble polymer in each polishing composition are as shown in Table 1.

  Although not shown in Table 1, the polishing compositions of Examples 1 to 6 and Comparative Examples 1 to 5 are all colloidal silica having an immobilized sulfonic acid (average primary particle size 35 nm, average secondary). The particle size is 70 nm and the average degree of association 2) is 5% by mass.

The results of evaluating the dispersion stability of each of the polishing compositions of Examples 1 to 6 and Comparative Examples 1 to 5 are shown in the “Dispersion stability” column of Table 2. In the same column, “x” indicates that gelation was observed in the polishing composition immediately after preparation, and “Δ” indicates that high temperature acceleration condition of 60 ° C. was observed although gelation was not observed immediately after preparation. Indicates that gelation was observed after storage for 1 week, and “◯” indicates that gelation was not observed after storage for 1 week at 60 ° C. under high temperature acceleration conditions.

About each polishing composition of Examples 1-6 and Comparative Examples 1-5, the number of molecules of the water-soluble polymer adsorbed per unit surface area of colloidal silica was measured as follows. That is, each polishing composition was allowed to stand for 1 day in an environment of a temperature of 25 ° C., and then centrifuged at a rotational speed of 20000 rpm for 2 hours to collect a supernatant. The total amount of organic carbon in the collected supernatant was measured using an organic carbon measuring device of a combustion catalytic oxidation method. Separately, a composition having a composition obtained by removing colloidal silica from each polishing composition was prepared and allowed to stand in an environment at a temperature of 25 ° C. for one day. Was used to measure the total amount of organic carbon in the composition. And the total adsorption amount of the water-soluble polymer with respect to the colloidal silica in polishing composition was computed by reducing the total amount of organic carbon in the supernatant liquid of corresponding polishing composition from this. The number of molecules of the water-soluble polymer adsorbed per unit surface area of the colloidal silica could be calculated based on the surface area of the colloidal silica and the molecular weight of the water-soluble polymer from the amount of adsorption calculated in this way. The results are shown in the column “Number of adsorbed molecules per 1 μm ^{2 of} colloidal silica” in Table 2.

  Using the polishing compositions of Examples 1 to 6 and Comparative Examples 1 to 5, a poly-Si / HDP pattern wafer having a diameter of 200 mm having a portion made of polysilicon and a portion made of high-density plasma CVD silicon oxide Polishing was performed under the conditions shown in Table 3. The polishing of the patterned wafer was finished after further continuing for 15 seconds after the upper surface of the polysilicon portion was exposed.

  About each pattern wafer after grinding | polishing, the progress amount of the fang and the progress amount of dishing were measured using the atomic force microscope in the area | region in which the polysilicon part of a 100 micrometer width is formed at 100 micrometer space | interval. The results are shown in the “Fang progress” column and the “Dishing progress” column in the “100 μm / 100 μm region” column of Table 2.

  Similarly, for each patterned wafer after polishing, the amount of progress of EOE and the amount of dishing were measured using an atomic force microscope in a region where 0.25 μm wide polysilicon portions were formed at intervals of 0.25 μm. . The results are shown in the “EOE progress amount” column and the “Dishing progress amount” column in the “0.25 μm / 0.25 μm region” column of Table 2.

As shown in Table 2, when using the polishing composition of Examples 1 to 6 in which the number of molecules of the water-soluble polymer adsorbed per 1 μm ² of the surface area of colloidal silica is 5000 or more, Compared with the case where the polishing composition of Comparative Example 1 containing no water-soluble polymer was used, a decrease was observed in all of the fang progress, EOE progress, and dishing progress. On the other hand, in the case where the polishing composition of Comparative Examples 2 to 5 in which the number of molecules of the water-soluble polymer adsorbed per 1 μm ² of the surface area of colloidal silica is less than 5000, all of the Comparative Example 1 Compared to the case where the polishing composition was used, a decrease was not observed in at least one of the fang progress amount, the EOE progress amount, and the dishing progress amount.

Claims (8)

A polishing composition comprising an abrasive having a silanol group and a water-soluble polymer,
When the polishing composition is allowed to stand for one day in an environment of a temperature of 25 ° C., 5000 or more water-soluble polymer molecules are adsorbed per 1 μm ² of the surface area of the abrasive grains. Polishing composition.   The polishing composition according to claim 1, wherein the water-soluble polymer is a nonionic compound having a polyoxyalkylene chain.   The polishing compound according to claim 2, wherein the nonionic compound having a polyoxyalkylene chain is polyethylene glycol, polypropylene glycol, polyoxyethylene alkylene glyceryl ether, polyoxyethylene alkyl ether, or polyoxyethylene sorbitan fatty acid ester. Composition.   The polishing composition according to any one of claims 1 to 3, which is used for polishing a polishing object having a hydrophobic silicon-containing portion and a hydrophilic silicon-containing portion.   The polishing composition according to claim 4, wherein the hydrophobic silicon-containing portion is made of polysilicon.   The polishing composition according to any one of claims 1 to 5, wherein the abrasive grains are colloidal silica in which an organic acid is immobilized.   A polishing method comprising polishing a polishing object having a hydrophobic silicon-containing portion and a hydrophilic silicon-containing portion using the polishing composition according to any one of claims 1 to 6. .   It has the process of grind | polishing the grinding | polishing target object which has a hydrophobic silicon-containing part and a hydrophilic silicon-containing part using the polishing composition as described in any one of Claims 1-6 characterized by the above-mentioned. Substrate manufacturing method.