TW202210596A - Polishing composition, method for machining wafer, and silicon wafer - Google Patents

Abstract

The present invention is a polishing composition characterized by including abrasive grains and at least one material from among water-soluble polymers and surfactants, the ratio of the concentration (ppmw) of abrasive grains relative to the concentration (ppmw) of total organic carbon in the polishing composition being 30 or less. This makes it possible to provide: a polishing composition with which it is possible to provide a wafer in which manifestation of crystal defects and polishing defects is inhibited; a method for machining a wafer with which it is possible to provide a wafer in which manifestation of crystal defects and polishing defects is inhibited; and a silicon wafer in which manifestation of crystal defects and polishing defects can be inhibited, even when the silicon wafer is etched.

Description

Polishing composition, wafer processing method, and silicon wafer

The present invention relates to a polishing composition, a wafer processing method, and a silicon wafer.

With the continuous miniaturization of semiconductor devices, the requirements for cleanliness and surface quality of silicon wafers as their substrates are also increasing.

One of the reasons for impairing surface quality is the presence of defects. Defects are roughly classified into crystal defects and polishing defects.

Crystal defects refer to defects introduced during crystal pulling, and examples thereof include oxygen precipitation defects, metal precipitation defects, voids, and the like.

On the other hand, the polishing defect occurs when foreign matter or the like is mixed in during polishing, and damage is introduced into the surface.

Since both crystal defects and polishing defects are deteriorated, for example, when a process such as wet etching without a planarization mechanism such as polishing is performed, the etching rate of the deteriorated portion is different from that of the surrounding area. Therefore, protrusions or pits are formed, and the greater the etching amount, the greater the amount of appearance. big.

Therefore, it is particularly desirable to reduce the amount of etching in the post-grinding rinse step as much as possible.

However, reducing the amount of etching in the rinsing step creates additional problems.

The purpose of post-polishing rinsing is to remove and send away the components contained in the polishing composition such as abrasive grains, water-soluble polymers, and surfactants. However, when the etching amount is reduced, there is a high possibility that these components cannot be removed and remain.

Therefore, it is necessary to develop a polishing method that does not leave the components of the polishing composition even if the etching amount is reduced. [Prior Art Literature] [Patent Literature]

[Patent Document 1] International Publication No. WO2007/046420

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a composition for polishing a wafer that can suppress the development of crystal defects and polishing defects, and a wafer processing method that can provide a wafer that suppresses the development of crystal defects and polishing defects. , and silicon wafers that suppress the appearance of crystal defects and polishing defects even if they are etched.

In order to achieve the above object, the present invention provides a kind of grinding composition, which is characterized by comprising: abrasive grains; and At least one of water-soluble polymers and surfactants, The ratio of the concentration (ppmw) of the abrasive grains to the concentration (ppmw) of the total organic carbon in the polishing composition is 30 or less.

By polishing a wafer using the polishing composition of the present invention, the adsorption of abrasive grains on the wafer can be suppressed. In this way, the amount of abrasive particles adsorbed on the wafer being polished can be reduced, thereby reducing the amount of abrasive particles remaining on the surface of the wafer after polishing. After polishing, the water-soluble polymer and/or surfactant remaining on the wafer can be easily removed by decomposing with an oxidizing agent, etc., so even if the etching amount is small, the wafer remaining after polishing can be sufficiently removed Components of the polishing composition on the surface. As a result, crystal defects and polishing defects can be prevented from appearing by etching. That is, according to the polishing composition of the present invention, it is possible to provide a high-quality wafer in which the amount of residual abrasive grains is small and the occurrence of crystal defects and polishing defects is suppressed.

In addition, the present invention provides a method for processing a wafer, which is characterized by comprising the following steps: grinding both sides or one side of the wafer by using the polishing composition of the present invention; by including at least one of O ₃ and H ₂ O ₂ A kind of chemical solution is used to decompose the organic matter on the wafer after grinding; and the wafer after grinding is etched by a chemical solution containing at least one of NH ₃ and HF, and the above-mentioned etching step is performed so that the total etching amount is 5nm or less.

Since the wafer processing method of the present invention uses the polishing composition of the present invention, crystal defects and polishing defects caused by etching can be suppressed from appearing, and the polishing composition remaining on the wafer surface after polishing can be sufficiently removed. ingredients. That is, according to the wafer processing method of the present invention, it is possible to provide a high-quality wafer with a small amount of residual abrasive grains and suppressed occurrence of crystal defects and polishing defects.

For example, the above-mentioned polishing step may be performed so that the amount of abrasive particles attached to the wafer surface after the polishing is 5 particles/μm ² or less.

By supplying the wafer with an amount of abrasive grains deposited on the surface of 5 particles/μm ² or less to the step of decomposing organic substances and the step of etching, it is possible to reliably remove the polishing composition remaining on the wafer surface after polishing. Element.

In addition, the present invention provides a silicon wafer, which is a silicon wafer polished with a polishing composition, characterized in that the amount of abrasive grains deposited on the polished surface is 5 particles/μm ² or less.

In the silicon wafer of the present invention, since the amount of abrasive grains deposited on the surface after polishing is 5 pieces/μm ² or less, the abrasive grains can be sufficiently removed even if the etching amount is small. As a result, crystal defects and polishing defects can be prevented from appearing by etching. That is, according to the silicon wafer of the present invention, it is possible to provide a high-quality wafer with a small amount of residual abrasive grains and suppressed occurrence of crystal defects and polishing defects.

As described above, the polishing composition of the present invention can provide a high-quality wafer that has a small amount of residual abrasive grains and suppresses the appearance of crystal defects and polishing defects. The surface quality of the wafer in which crystal defects and polishing defects are suppressed is high and can be effectively used as a wafer in response to the miniaturization requirements of semiconductor devices.

In addition, the wafer processing method of the present invention can provide a high-quality wafer with a small amount of residual abrasive grains and suppressed occurrence of crystal defects and polishing defects. The surface quality of the wafer obtained by this method is high, so it can be effectively used as a substrate of a semiconductor device.

In addition, the silicon wafer of the present invention can provide a high-quality silicon wafer with a small amount of residual abrasive grains and suppressing the appearance of crystal defects and polishing defects. If the silicon wafer of the present invention is used, a wafer with high surface quality can be produced, and then the wafer with high surface quality can be used as a substrate to produce a semiconductor device that responds to miniaturization requirements.

As described above, there is a need to develop a polishing composition that can provide a wafer that suppresses the development of crystal defects and polishing defects.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies with the aim of finding rinse conditions in which crystal defects and polishing defects do not appear, and to find conditions of a polishing composition that can be removed by such rinse conditions.

First, the inventors reviewed the rinsing conditions and compared the appearance of crystal defects and polishing defects, and found that the etching amount of the rinsing has a great influence.

The rinsing includes, for example: rinsing of a mixed solution of NH ₃ and H ₂ O ₂ , rinsing of natural oxide film stripping by HF, rinsing of O ₃ or a mixed solution of H ₂ O ₂ and HF, and mixing of HCl and H ₂ O ₂ The washing of the solution, etc., but the washing of the mixed solution of NH ₃ and H ₂ O ₂ , the washing of stripping the natural oxide film by HF, and the washing of the mixed solution of O ₃ or H ₂ O ₂ and HF are accompanied by etching.

It can be understood that the degree of appearance of crystal defects and polishing defects varies depending on the amount of these etchings, and it is understood that in order to suppress the appearance of crystal defects and polishing defects, it is important to suppress the amount of etching per side to a total of 5 nm or less. .

In addition, it was found that by suppressing the total etching amount of each side in the etching step to 5 nm or less, the productivity of the etching apparatus can be improved, and the usage amount of the chemical solution can also be suppressed.

However, since the total etching amount in the etching step is suppressed to 5 nm or less, another problem arises.

Since the total etching amount was suppressed to 5 nm or less, crystal defects and polishing defects were reduced, but the remaining abrasive grains increased conversely, and the number of defects detected by a particle counter increased.

This phenomenon is considered to be because the amount of etching is reduced compared to the conventional one, so the abrasive grains adhering to the wafer after polishing are not peeled off and remain on the surface.

Therefore, if the residual abrasive grains of the wafer after polishing can be reduced, it is considered that the residual abrasive grains of the wafer after etching can also be reduced.

Based on the above knowledge, the inventors of the present invention further repeated intensive examinations, and as a result found that the polishing composition contains at least one of a water-soluble polymer and a surfactant in addition to the abrasive grains, and the abrasive grains in the polishing composition are The ratio of the concentration to the concentration of Total Organic Carbon (TOC: Total Organic Carbon) is 30 or less, which can reduce the amount of abrasive particles adsorbed on the wafer being polished, thereby reducing the residual abrasive particles on the wafer surface after polishing. , and complete the present invention.

That is, the present invention is a polishing composition characterized by comprising: abrasive grains; and At least one of water-soluble polymers and surfactants, The ratio of the concentration (ppmw) of the abrasive grains to the concentration (ppmw) of the total organic carbon in the polishing composition is 30 or less.

In addition, the present invention relates to a wafer processing method, which is characterized by comprising the following steps: grinding both sides or one side of the wafer by using the polishing composition of the present invention; by including at least one of O ₃ and H ₂ O ₂ A kind of chemical solution is used to decompose the organic matter on the wafer after grinding; and the wafer after grinding is etched by a chemical solution containing at least one of NH ₃ and HF, and the above-mentioned etching step is performed so that the total etching amount is 5nm or less.

In addition, the present invention relates to a silicon wafer polished using the polishing composition, characterized in that the amount of abrasive grains deposited on the polished surface is 5 particles/μm ² or less.

Furthermore, Claim 1 of Patent Document 1 describes the invention of a cerium oxide slurry containing cerium oxide particles, a dispersant, and water, and a cerium oxide slurry having a cerium oxide weight/dispersant weight ratio of 20 to 80. The slurry described in Patent Document 1 contains cerium oxide as an abrasive. In addition, for example, paragraph 0032 and claim 4 of Patent Document 1 describe poly(meth)acrylates, polyacrylic acid-polyacrylic acid alkylammonium salt copolymers, and the like as examples of the dispersing agent. In addition, claim 8 of Patent Document 1 describes a method of polishing a substrate using the slurry. Moreover, according to the paragraph 0102 of Patent Document 1, according to such a cerium oxide slurry and a polishing method, the polishing damage can be reduced and the polishing rate can be further increased.

However, Patent Document 1 does not pay attention to the total organic carbon concentration in the cerium oxide slurry at all, and therefore does not pay attention at all to the concentration (ppmw) of the abrasive grains in the cerium oxide slurry to the concentration (ppmw) of the total organic carbon. The ratio is 30 or less.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to these descriptions.

(polishing composition) The polishing composition of the present invention is characterized by comprising: abrasive grains; and at least one of a water-soluble polymer and a surfactant, and the concentration (ppmw) of the abrasive grains in the polishing composition is relative to the total organic carbon The ratio of the concentration (ppmw) is 30 or less.

In this way, the polishing composition of the present invention can suppress the adsorption of abrasive grains on the wafer. Thereby, the amount of abrasive grains adhering to the wafer being polished can be reduced, thereby reducing the amount of abrasive grains remaining on the surface of the wafer after polishing.

The reasons for presenting the present results are considered as follows.

The silicon wafer being polished has high activity because there is no natural oxide film on the surface, so it is in an environment where abrasive particles, water-soluble polymers and surfactants are easily adsorbed on the surface.

In such an environment, since the ratio of the water-soluble polymer or surfactant to the abrasive grains is increased, the adsorption rate of the water-soluble polymer or surfactant on the wafer surface can be increased. There is physical room for the adsorption of abrasive particles in the round surface, so the residual abrasive particles are reduced.

At this time, there is a possibility that the water-soluble polymer or surfactant may remain _on the surface after grinding, but the water _- soluble polymer or surfactant may be decomposed by oxidizing agents such as _O3 or H2O2, and the results are comparable Abrasive particles are easier to remove, so they can be removed without etching.

Therefore, when polishing a wafer using the polishing composition of the present invention, even if the etching amount is small, the components of the polishing composition can be sufficiently removed from the wafer surface after polishing. As a result, crystal defects and polishing defects can be prevented from appearing by etching. That is, according to the polishing composition of the present invention, it is possible to provide a high-quality wafer in which the amount of residual abrasive grains is small and the occurrence of crystal defects and polishing defects is suppressed.

In addition, the extent to which at least one of the water-soluble polymer and the surfactant can be adsorbed and coated on the wafer surface is considered to be most related to the length of the carbon-carbon bonds in these components.

The organic content of the water-soluble polymer and the surfactant can be appropriately evaluated by TOC (total organic carbon). In addition, TOC (total organic carbon) is a value obtained by subtracting IC (inorganic carbon) from TC (total carbon). Therefore, the concentration of total organic carbon (TOC) can be ideally used as an indicator of the carbon-carbon bond length of water-soluble polymers and surfactants.

In addition, if the concentration ratio of abrasive grains to TOC can be properly controlled, the residual abrasive grains of the wafer after polishing can be reduced.

As a result of the examination of the present inventors, it was found that it is important to set the ratio of the abrasive grain concentration (ppmw) to the TOC concentration (ppmw) in the polishing composition to 30 or less.

More specifically, it was found that by setting the ratio of the abrasive grain concentration to the total organic carbon concentration in the polishing composition to 30 or less, the amount of abrasive grains adsorbed on the wafer surface during polishing can be sufficiently suppressed, As a result, the amount of abrasive particles remaining on the wafer surface after polishing can be reduced.

On the other hand, when the ratio exceeds 30, the amount of abrasive particles adsorbed on the wafer surface during polishing is excessive, and in order to sufficiently remove the remaining abrasive particles after polishing, it is necessary to ensure a large amount of etching in the subsequent etching step. When the etching amount is increased, the appearance of crystal defects and grinding defects is more likely to occur.

The lower limit of the ratio of the abrasive grain concentration to the total organic carbon concentration in the polishing composition is not particularly limited, but may be, for example, 1 or more. The ratio of the abrasive grain concentration to the total organic carbon concentration in the polishing composition is preferably 1 or more and 30 or less. Within this range, sufficient grinding of the abrasive grains can be achieved, and at the same time, the amount of residual abrasive grains after grinding can be further reduced. The above ratio is more preferably 3 or more and 10 or less.

The concentration of total organic carbon (TOC) in the polishing composition can be measured, for example, by TOC-L series manufactured by Shimadzu Corporation. The concentration of the abrasive grains in the polishing composition can be measured, for example, with a Densitometer DA-100 manufactured by Kyoto Electronics Industry Co., Ltd.

The ratio of the abrasive grain concentration to the total organic carbon concentration in the polishing composition can be adjusted by mutually adjusting the amount of abrasive grains, the amount of water-soluble polymer, and the amount of surfactant contained in the composition.

Hereinafter, the polishing composition of the present invention will be described in more detail.

＜Abrasive Grain＞ Examples of abrasive grains include silicon dioxide, aluminum oxide, cerium oxide, chromium oxide, titanium dioxide, zirconium oxide, magnesium oxide, manganese dioxide, zinc oxide, silicon nitride, boron nitride, and silicon carbide. , boron carbide, diamond, fullerene, etc., but in order to suppress surface defects, silicon dioxide is preferred.

Silica includes colloidal silica, fumed silica, water glass silica, etc. due to different manufacturing methods, but in order to prevent scratches, colloidal silica is preferred.

From the viewpoint of reducing defects, the primary particle size of the colloidal silica is preferably 1000 nm or less, more preferably 300 nm or less, and more preferably 100 nm or less. In addition, from the viewpoint of increasing the polishing rate, it is preferably 1 nm or more, and more preferably 10 nm or more.

From the viewpoint of preventing aggregation, the concentration of colloidal silica is preferably 10 wt % or less, and more preferably 1 wt % or less. In addition, from the viewpoint of increasing the polishing rate, it is preferably 0.0001 wt % or more, and more preferably 0.001 wt % or more.

＜Water-soluble polymer＞ As the water-soluble polymer, for example, cellulose derivatives can be preferably used, and hydroxyethyl cellulose, propyl ethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, and the like can be used. These cellulose derivatives can also be referred to as water-soluble semi-synthetic polymers.

In addition, from the viewpoint of reducing defects, there is a tendency to use a synthetic polymer different from the above-mentioned semi-synthetic polymer as the water-soluble polymer. For example, polymers such as polyvinyl alcohol and polyvinylpyrrolidone can be preferably used. .

＜Surfactant＞ As the surfactant, a cationic surfactant, an anionic surfactant, or a nonionic surfactant can be used, but a nonionic surfactant is particularly preferred.

Among the nonionic surfactants, polyoxyethylene-polyoxypropylene block copolymers or random copolymers, polyoxyethylene alkyl ethers, polyoxyethylene phenyl ethers, and the like can be mentioned as preferable examples.

＜Other ingredients＞ In addition to the abrasive grains, the water-soluble polymer and the surfactant, the polishing composition of the present invention may further include, for example, a dispersant, a pH adjuster, and the like.

As the dispersing medium, water, especially pure water, is preferably used.

When using colloidal silica as abrasive particles, in order to improve the dispersion stability of colloidal silica, the pH adjuster should be alkaline. As the basic compound, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, lithium hydroxide, tetramethylammonium hydroxide, ammonia, amines, and the like can be preferably used.

(Wafer Processing Method) The wafer processing method of the present invention is characterized by comprising the following steps: polishing both sides or one side of the wafer using the polishing composition of the present invention; by including O ₃ and H ₂ O ₂ at least one chemical solution to decompose the organic matter on the wafer after grinding; and etching the polished wafer by a chemical solution containing at least one of NH ₃ and HF, and performing the above etching step to make the total The etching amount is 5 nm or less.

By using the polishing composition of the present invention, as described above, the amount of abrasive particles adsorbed on the wafer surface during polishing can be sufficiently suppressed, and as a result, residual abrasive particles on the wafer surface after the polishing step can be reduced. quantity. In addition, the water-soluble polymer and/or surfactant remaining on the wafer surface after the polishing step is decomposed by a chemical solution containing at least one of O ₃ and H ₂ O ₂ in the subsequent step of decomposing organic substances. Etching the wafers in which the organic substances on the surface are decomposed in this way is etched by a chemical solution containing at least one of NH ₃ and HF, so that the total etching amount is 5 nm or less, which can suppress the appearance of crystal defects and polishing defects caused by etching, and at the same time The components of the polishing composition remaining on the wafer surface after polishing are sufficiently removed.

That is, according to the wafer processing method of the present invention, it is possible to provide a high-quality wafer with a small amount of residual abrasive grains and suppressed occurrence of crystal defects and polishing defects.

Next, each step of the wafer processing method of the present invention will be sequentially described in detail.

＜Steps of grinding＞ In the polishing step, both sides or one side of the wafer is polished using the polishing composition of the present invention.

Wafers for grinding are silicon wafers, for example. The silicon wafer may be, for example, a slice obtained by slicing a silicon ingot and plane grinding the slice.

The grinding step can be a one-stage step or a multi-stage step. From the viewpoint of surface quality, it is desirable to perform at least two stages of grinding.

The polishing is preferably performed by keeping the wafer pressed against the polishing cloth and continuously supplying the polishing composition to the polished surface of the wafer. The cloth is rotated side by side.

Grinding can be two-sided or one-sided. In the case of double-side polishing, for example, a polishing cloth is arranged above and below the wafer, and both sides are simultaneously polished. In addition, in the case of one-side polishing, the polishing cloth is arranged on only one side of the wafer.

From the viewpoint of surface quality, the polishing cloth is preferably made of resin, and it is suitable to use urethane resin because of its good abrasion resistance.

It is possible to use a urethane resin impregnated in fibers such as non-woven fabrics as a polishing cloth, or to heat the urethane resin to form a foamed urethane resin and use the foamed urethane resin as a polishing cloth, Alternatively, the urethane resin can also be coated on a substrate such as a PET film to form a chamois by hydrolysis, and the chamois can be used as a polishing cloth.

From the viewpoint of the polishing rate, the hardness of the polishing cloth is preferably 30 or more in Shore A hardness, and more preferably 50 or more. In addition, from the viewpoint of surface quality, the hardness of the polishing cloth is preferably 95 or less, and more preferably 90 or less.

In order for the polishing composition to function effectively, the polishing cloth preferably has a textured structure such as grooves.

For example, the polishing step may be performed so that the amount of abrasive particles attached to the wafer surface after polishing is 5 particles/μm ² or less.

By supplying the wafer with an amount of abrasive particles attached to the surface of 5 particles/μm ² or less to the step of decomposing organic substances and the step of etching, which are described below, the polishing remaining on the surface of the wafer after polishing can be reliably removed. Use the ingredients of the composition.

The amount of abrasive particles attached to the wafer surface can be measured by, for example, a scanning electron microscope (SEM). According to the polishing step of the wafer processing method of the present invention, the amount of abrasive particles attached to the surface can be, for example, 0.1 particles/μm ² or more and 5 particles/μm ² or less, and preferably 1 particle/μm ² or more and 3 particles/μm 2 . μm ² or less.

<Step of Decomposing Organic Matter> The step of decomposing organic matter is to decompose the organic matter on the wafer after polishing with a chemical solution containing at least one of O ₃ and H ₂ O ₂ .

O ₃ and/or H ₂ O ₂ are used as oxidizing agents, and can decompose the organic matter on the polished wafer, that is, the organic matter generated from water-soluble polymers and/or surfactants. Products resulting from the decomposition of organics can be removed from the wafer without etching.

The chemical solution used in the step of decomposing organic matter may contain components other than O ₃ and H ₂ O ₂ . Specific examples will be described later.

<Step of Etching> The step of etching is to etch the polished wafer with a chemical solution containing at least one of NH ₃ and HF. At this time, etching is performed so that the total etching amount is 5 nm or less.

The total etching amount here is the total etching amount of the side for etching when etching one side of the wafer, and the total etching amount of each side for etching when etching both sides of the wafer. That is, the total etching amount is the total etching amount for each side of the wafer.

By performing the etching so that the total etching amount is 5 nm or less, the appearance of crystal defects and polishing defects caused by etching can be sufficiently suppressed.

The lower limit of the total etching amount is not particularly limited, but may be, for example, 3 nm. The total etching amount is preferably 0.1 nm or more and 5 nm or less, and more preferably 1 nm or more and 5 nm or less.

The total etching amount of the etching step can be confirmed by the following procedure. First, a reference SOI (Silicon On Insulator) wafer was prepared, and the SOI film thickness was measured with a spectral ellipsometry UNECS-3000 manufactured by ULVAC to obtain the SOI film thickness before etching. Next, the reference SOI wafer is etched under the same conditions as those of the etching step of the confirmation object. Next, the SOI film thickness after etching was measured with the same spectral ellipsometry to obtain the SOI film thickness after etching. Next, the difference in SOI film thickness before and after etching was used as the total etching amount of the etching step to be confirmed.

In addition, the total etching amount of the etching step can be adjusted by, for example, the etchant concentration of the chemical solution containing at least one of NH ₃ and HF, the etching time, and the temperature of the chemical solution.

For example, the medicinal solution can be warmed as needed. The amount of etching can be increased by heating.

The chemical solution used in the etching step may contain components other than NH ₃ and HF. Specific examples will be described later.

In addition, the above-mentioned step of decomposing the organic matter and the step of etching may be performed separately or simultaneously. The step of decomposing organic matter and the step of etching may also be combined as a rinse step.

<Other steps> The wafer processing method of the present invention may further include, for example, an evaluation step after the etching step. For example, in the evaluation step, surface defect evaluation may be performed. As the surface defect evaluation apparatus, for example, Surfscan series manufactured by KLA Corporation can be used.

＜Medicine＞ For the step of decomposing organic matter and the step of etching, one chemical solution or a plurality of chemical solutions can be used separately.

In addition, when the step of decomposing the organic matter and the step of etching are performed simultaneously, a mixed solution containing at least one of O ₃ and H ₂ O ₂ and at least one of NH ₃ and HF can be used.

For example, the rinsing step may use: a mixed solution containing NH ₃ and H ₂ O ₂ ; a mixed solution containing HF and O ₃ ; and a mixed solution containing HF, O ₃ and H ₂ O ₂ as the chemical solution.

When the step of decomposing the organic matter is performed separately from the step of etching, as the chemical solution for decomposing the organic matter, for example, a mixed solution containing HCl and H ₂ O ₂ ; a solution containing H ₂ O ₂ ; and a solution containing O ₃ solution.

When the step of etching is performed separately from the step of decomposing organic substances, examples of the chemical solution used in the step of etching include a mixed solution containing HF and HNO ₃ , a solution containing NH ₃ , and a solution containing HF.

These chemical solutions may also contain water, especially pure water, as a solvent.

(Silicon Wafer) The silicon wafer of the present invention is a silicon wafer polished using the polishing composition, and is characterized in that the amount of abrasive grains deposited on the polished surface is 5 particles/μm ² or less.

The silicon wafer of the present invention can be produced by, for example, the grinding step of the wafer processing method of the present invention described previously.

By supplying such a silicon wafer to the step of decomposing organic substances and the step of etching described above, in addition to reliably removing the components of the polishing composition remaining on the wafer surface after polishing, crystal defects can also be prevented. And polishing defects appear due to etching. That is, according to the silicon wafer of the present invention, it is possible to provide a silicon wafer in which crystal defects and polishing defects are suppressed from appearing. [Example]

Hereinafter, the present invention will be specifically described using Examples and Comparative Examples, but the present invention is not limited to these Examples and Comparative Examples.

(Comparative Example 1) In Comparative Example 1, wafer processing was performed by the following procedure.

[Prepare] First, a silicon wafer with a diameter of 300 mm and a thickness of 775 μm is prepared as a wafer to be processed.

[Steps of Grinding] In Comparative Example 1, the polishing composition of Comparative Example 1 in which the concentration of abrasive grains was 10,000 ppmw and the TOC concentration was 100 ppmw was prepared by the following procedure.

Prepare colloidal silica as abrasive grains. In addition, polyvinyl alcohol (PVA) as a water-soluble polymer and polyoxyethylene-polyoxypropylene block copolymer (EOPO) as a surfactant were prepared.

Next, colloidal silica, polyvinyl alcohol, and polyoxyethylene-polyoxypropylene block copolymer were put into pure water at a weight ratio of 10,000:90:10 to prepare a polishing composition of Comparative Example 1.

Next, one side of the wafer to be processed in Comparative Example 1 was polished using the polishing composition of Comparative Example 1. The SEM image of the polished wafer surface obtained in the polishing step of Comparative Example 1 is shown on the left side of FIG. 1 .

[Step of Decomposing Organic Matter] Next, a chemical solution containing ozone (O ₃ ) is supplied to the surface of the polished wafer, and then the chemical solution is washed away with pure water.

[Step of Etching] Next, a mixed solution of NH ₃ /H ₂ O ₂ /H ₂ O is supplied to the polished wafer surface. The NH ₃ /H ₂ O ₂ /H ₂ O mixed solution used was 28 wt % NH ₃ and 30 wt % H ₂ O ₂ , and by using NH ₃ : H ₂ O ₂ : H ₂ O =1:1:10 ratio mixing to modulate. The temperature at the time of supply was 50°C. The time of contact with the mixed solution of NH ₃ /H ₂ O ₂ /H ₂ O was 5 minutes. Thereby, the total etching amount of the mixed solution of NH ₃ /H ₂ O ₂ /H ₂ O was 3 nm.

Next, the HF aqueous solution is supplied to the surface of the wafer. The HF concentration of the HF aqueous solution used was 1 wt %, and the temperature at the time of supply was 25°C. The time of exposure to the aqueous HF solution was 5 minutes. Thereby, the total etching amount of HF is 1 nm.

(Example 1) In Example 1, except that the abrasive grain concentration of the polishing composition in the polishing step is 3000 ppmw and the TOC concentration is 100 ppmw, and the NH ₃ /H ₂ O ₂ /H ₂ O in the etching step A wafer similar to that processed in Comparative Example 1 was processed by the same procedure as in Comparative Example 1 except that the total etching amount of the mixed solution was 9 nm and the total etching amount of HF was 1 nm.

In Example 1, colloidal silica, polyvinyl alcohol and polyoxyethylene-polyoxypropylene block copolymer were put into pure water in a weight ratio of 3000:90:10 to obtain the polishing composition of Example 1 .

In addition, in Example 1, the mixed liquid of NH ₃ /H ₂ O ₂ /H ₂ O supplied in the etching step was the same mixed liquid as the mixed liquid used in Comparative Example 1, and the temperature at the time of supply was is 50°C. The contact time with the NH ₃ /H ₂ O ₂ /H ₂ O mixture was 15 minutes.

In addition, in Example 1, the concentration of the HF aqueous solution supplied in the etching step was 1 wt %, and the temperature at the time of supply was 25°C. The time of exposure to the aqueous HF solution was 5 minutes.

(Example 2) In Example 2, except that the total etching amount of the mixed solution of NH ₃ /H ₂ O ₂ /H ₂ O in the etching step was 3 nm and the total etching amount of HF was 1 nm, the same The same procedure as in Example 1 was used to process the same wafers as those processed in Comparative Example 1.

In Example 2, the etching step was performed under the same conditions as in Comparative Example 1.

The SEM image of the wafer surface after polishing using the polishing composition of Example 2 is shown on the right side of FIG. 1 .

(Example 3) In Example 3, the same procedure as in Example 2 was used to process the same wafer as in Comparative Example 1, except that the abrasive grain concentration of the polishing composition in the polishing step was 1000 ppmw and the TOC concentration was 100 ppmw wafer.

In Example 3, colloidal silica, polyvinyl alcohol and polyoxyethylene-polyoxypropylene block copolymer were put into pure water in a weight ratio of 1000:90:10 to obtain the grinding composition of Example 3 .

(Example 4) In Example 4, the same procedure as in Example 2 was used to process the same wafer as in Comparative Example 1, except that the abrasive grain concentration of the polishing composition in the polishing step was 370 ppmw and the TOC concentration was 50 ppmw wafer.

In Example 4, colloidal silica, polyvinyl alcohol and polyoxyethylene-polyoxypropylene block copolymer were put into pure water at a weight ratio of 370:45:5 to obtain the polishing composition of Example 4 .

(Example 5) In Example 5, the same procedure as in Example 2 was used to process the same wafer as in Comparative Example 1, except that the abrasive grain concentration of the polishing composition in the polishing step was 1000 ppmw and the TOC concentration was 167 ppmw wafer.

In Example 5, colloidal silica, polyvinyl alcohol and polyoxyethylene-polyoxypropylene block copolymer were put into pure water in a weight ratio of 1000:150:17 to obtain the grinding composition of Example 5 .

In Table 1 below, the abrasive grain concentration, TOC concentration (total organic carbon concentration), the ratio of abrasive grain concentration to TOC concentration, and the etching amount of the polishing composition of each Example and Comparative Example are shown.

[Table 1] Grinding composition Etching steps Abrasive particle concentration TOC concentration Abrasive particle concentration/TOC concentration NH ₃ /H ₂ O ₂ etching amount HF etching amount Comparative Example 1 10000ppmw 100ppmw 100 3 1 Example 1 3000ppmw 100ppmw 30 9 1 Example 2 3000ppmw 100ppmw 30 3 1 Example 3 1000ppmw 100ppmw 10 3 1 Example 4 370ppmw 50ppmw 7.4 3 1 Example 5 1000ppmw 167ppmw 6 3 1

[Evaluation] About each wafer after the etching process of an Example and a comparative example, evaluation was implemented by the Surfscan series SP3 made by KLA Corporation, and the LLS defect was evaluated. The results are shown in Table 2 and FIG. 2 below.

[Table 2] LLS defects (pcs/wafer) Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 100 51 27 25 31 twenty three

From the results shown in Table 2 and FIG. 2 and the information shown in Table 1, it can be understood that the ratio of the abrasive particle concentration (ppmw) to the total organic carbon concentration (ppmw) in the polishing composition is 30 or less. Examples 1 to 5 of the polishing composition of 5 can achieve a defect level better than that of Comparative Example 1 using the polishing composition of Comparative Example 1 whose ratio exceeds 30.

In addition, in the two SEM images shown in FIG. 1 , the white part is seen to be abrasive grains. From the comparison of the two SEM images shown in FIG. 1, it can also be understood that the amount of abrasive particles remaining on the surface of the wafer obtained after the grinding step in Example 2 is 0.42 pcs/μm ² , which is higher than that in Comparative Example 1. 8.5pcs/μm ² of residual abrasive particles is much less. The amount of residual abrasive grains in Examples 1, 3 to 5 was also the same as that in Example 2. That is, it can be understood that by using the polishing compositions of Examples 1 to 5 in which the ratio of the abrasive particle concentration (ppmw) to the total organic carbon concentration (ppmw) in the polishing composition is 30 or less, compared to using the polishing compositions When the above-mentioned ratio exceeds 30, the polishing composition of Comparative Example 1 can reduce the amount of abrasive grains remaining on the wafer after polishing. It is considered that this action produces the difference in the number of defects shown in Table 2 and FIG. 2 .

In addition, from the comparison between Example 1 and Examples 2 to 5, it can be understood that the polishing composition of the present invention is used and the total etching amount in the etching step is 5 nm, compared to Example 1 in which the total etching amount is larger than 5 nm. The following Examples 2 to 5 can achieve better defect levels.

In addition, this invention is not limited to the said embodiment. The above-mentioned embodiments are only examples, and those having substantially the same structure as the technical idea described in the scope of the patent application of the present invention and achieving the same effect are included in the technical scope of the present invention.

without

FIG. 1 is an SEM image of the wafer surface after the polishing step prepared in Comparative Example 1 and Example 2, respectively. [ FIG. 2 ] is a graph showing the number of LLS defects on the wafer surface after the etching step produced in each of the Examples and Comparative Examples.

Claims (4)

A composition for grinding, comprising: abrasive grains; and At least one of water-soluble polymers and surfactants, The ratio of the concentration (ppmw) of the abrasive grains to the concentration (ppmw) of the total organic carbon in the polishing composition is 30 or less. A wafer processing method, comprising the following steps: using the polishing composition as claimed in claim ₁ to polish _both sides or one side of the wafer _; Decomposing the organic matter on the polished wafer; and etching the polished wafer with a chemical solution containing at least one of NH ₃ and HF, and performing the etching step so that the total etching amount is 5 nm or less. The wafer processing method according to claim 2, wherein the grinding step is performed so that the adhered amount of abrasive grains on the wafer surface after grinding is 5 particles/μm ² or less. A silicon wafer is a silicon wafer polished using a polishing composition, characterized in that the amount of abrasive particles attached to the polished surface is 5 particles/μm ² or less.

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