Abrasive, polishing method, and method for manufacturing semiconductor components

Abstract

Provided is a polishing agent, a polishing method, and a method for manufacturing a semiconductor component that exhibit a good polishing speed in CMP of a surface to be polished, said surface including boron-doped silicon.　The polishing agent according to the present invention is for polishing a surface to be polished, said surface including boron-doped silicon, the polishing agent including abrasive grain, an oxidant, and water, the oxidant including at least one type that is selected from a peroxide oxidant, a metal ion oxidant, and a halogen oxo acid ion oxidant.

Description

[Technical Field]

[0001] The present invention relates to an abrasive used in the manufacturing process of semiconductor devices, and more specifically to an abrasive suitable for polishing a surface to be polished containing boron-doped silicon, a polishing method, and a method for manufacturing semiconductor components. [Background technology]

[0002] In recent years, with the increasing integration and functionality of semiconductor integrated circuits, the development of microfabrication technologies for miniaturization and high density of semiconductor elements has been progressing. Conventionally, in the manufacturing of semiconductor integrated circuit equipment (hereinafter also referred to as "semiconductor devices"), chemical mechanical polishing (hereinafter referred to as "CMP") has been used to planarize interlayer insulating films and embedded wiring in order to prevent problems such as surface irregularities (steps) exceeding the depth of focus of lithography and failing to obtain sufficient resolution. In CMP, the optimal abrasive is prepared as appropriate for each material to be polished. For example, Patent Document 1 describes that when polishing silicon nitride as a hard mask, silicon nitride can be polished at high speed by using an abrasive containing a liquid medium, abrasive grains containing a hydroxide of a tetravalent metal element, and a polyoxyalkylene compound containing a carboxyl group, wherein the weight-average molecular weight of the polyoxyalkylene compound is 3500 or more. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-19893 [Overview of the project] [Problems that the invention aims to solve]

[0004] In recent years, boron-doped silicon has sometimes been used as a hard mask. However, boron-doped silicon is difficult to process, and it has been difficult to achieve sufficient polishing speed using conventional hard mask polishing compounds in CMP (Chemical Polishing). The present invention has been made in view of the above, and aims to provide an abrasive, a polishing method, and a method for manufacturing semiconductor components that have a good polishing speed in CMP of a surface to be polished containing boron-doped silicon. [Means for solving the problem]

[0005] This disclosure provides an abrasive, a polishing method, and a method for manufacturing semiconductor components having the following configurations [1] to

[15] . [1] A polishing agent for polishing a surface containing boron-doped silicon, comprising abrasive grains, an oxidizing agent, and water, wherein the oxidizing agent comprises at least one selected from a peroxide oxidizing agent, a metal ion oxidizing agent, and a halogen oxoate ion oxidizing agent. [2] An abrasive having an oxidation-reduction potential of 0.55V or higher at 23°C relative to a standard hydrogen electrode [1]. [3] An abrasive having a concentration of the oxidizing agent of any of the [1] to [2] above, wherein the concentration of the oxidizing agent is 0.5% to 20% by mass relative to the total mass of the abrasive. [4] An abrasive according to any of the [1] to [3], wherein the concentration of the oxidizing agent is 1.6% to 20% by mass relative to the total mass of the abrasive. [5] An abrasive containing any of the [1] to [4] oxidizing agents, wherein the oxidizing agent contains a metal ion oxidizing agent. [6] The abrasive comprising any of [1] to [5], wherein the oxidizing agent is a metal ion oxidizing agent having a standard oxidation-reduction potential of 0.7 V or higher. [7] The abrasive comprising any of the metal ion oxidizing agents [1] to [6], wherein the metal ion oxidizing agent contains cerium(IV) nitrate ions. [8] The abrasive containing permanganate ions [1] to [7], wherein the metal ion oxidizing agent is any of the following: [9] An abrasive containing an acidic compound other than the oxidizing agent, any of [1] to [8].

[10] Any of the abrasives [1] to [9] having a pH of less than 7 at 23°C.

[11] Abrasives of any of the following [1] to

[10] , wherein the abrasive grains contain silica particles.

[12] Abrasives containing ceria particles, any of [1] to

[11] .

[13] Abrasives of any of the following [1] to

[12] , wherein the boron concentration in the boron-doped silicon is 0.5 at% to 90 at% in terms of atomic composition percentage.

[14] A polishing method in which polishing is performed by bringing a polishing pad into contact with the surface to be polished of a semiconductor substrate while supplying an abrasive, and polishing by the relative movement of the two, wherein the abrasive is one of the abrasives [1] to

[13] , and the surface to be polished contains boron-doped silicon. A method for manufacturing semiconductor components, comprising obtaining semiconductor components by framing a semiconductor substrate having a polished surface polished by the polishing method described in

[15]

[14] . [Effects of the Invention]

[0006] According to the present invention, it is possible to provide an abrasive, a polishing method, and a method for manufacturing semiconductor components that have a good polishing speed in CMP of a surface to be polished containing boron-doped silicon. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows the relationship between the oxidation-reduction potential of the abrasive at 23°C and the polishing rate of the boron-doped silicon substrate. [Figure 2] This is a schematic diagram showing an example of a polishing apparatus. [Modes for carrying out the invention]

[0008] The embodiments of the present invention will be described below. The present invention is not limited to the embodiments described below, and other embodiments may also fall within the scope of the present invention as long as they are consistent with the spirit of the present invention.

[0009] A.Term definition In this specification, the "surface to be polished" refers to the surface of an object to be polished, for example, it means the surface. In this specification, the surface at an intermediate stage that appears on a semiconductor substrate during the process of manufacturing a semiconductor device is also included in the "surface to be polished". In this specification, the "redox potential" is a measured value obtained as the potential difference from a reference electrode, and it is a value that depends on the measurement conditions. In this specification, the "standard redox potential" is a theoretical value obtained as the potential difference at 25°C from a standard hydrogen electrode with a partial pressure of 1 atm and a concentration of 1 mol for any substance, and it is a value specific to the substance. In this specification, "~" indicating a numerical range includes the numerical values described before and after it as the lower limit value and the upper limit value.

[0010] B. Polishing Agent The polishing agent according to the present invention (hereinafter also referred to as "the present polishing agent") is a polishing agent for polishing a surface to be polished containing boron-doped silicon, and includes abrasive grains, an oxidizing agent, and water, and is characterized in that the oxidizing agent includes at least one selected from a peroxide oxidizing agent, a metal ion oxidizing agent, and a halogen oxoacid ion oxidizing agent.

[0011] "Boron-doped silicon" is silicon doped with boron. When this polishing agent is used for CMP of a surface to be polished containing boron-doped silicon, a high polishing rate can be achieved. Regarding the mechanism by which this polishing agent exhibits the above effects, there are still some unclear parts. However, it is presumed that the above specific oxidizing agent reacts with boron in the boron-doped silicon, and the boron in the boron-doped silicon becomes boric acid and dissolves in the polishing agent.

[0012] In addition, the boron concentration in boron-doped silicon may be, for example, 0.5 at% or more, 10 at% or more, or 30 at% or more in atomic composition percentage. If the boron concentration in boron-doped silicon is 0.5 at% or more, better hardness of the boron-doped silicon can be obtained. Also, the boron concentration in boron-doped silicon may be 90 at% or less, 80 at% or less, or 70 at% or less. As described above, boron in boron-doped silicon is presumed to be removed particularly by reaction with an oxidizing agent. Therefore, if the boron concentration in boron-doped silicon is 90 at% or less, the contribution of chemical polishing by the oxidizing agent does not become excessive, and the contribution of mechanical polishing becomes a certain level or more. In chemical polishing, regardless of the uneven shape of the polished surface, the contact portion between the reactive species contained in the polishing agent and the polished surface is polished. However, in mechanical polishing, a higher pressure is applied to the convex portions of the polished surface than to the concave portions, so the convex portions are preferentially polished. Therefore, when the contribution of mechanical polishing is a certain level or more, a polished surface with high flatness can be obtained.

[0013] This polishing agent contains at least abrasive grains, water, and the specific oxidizing agent described above, and may further contain other components within the range in which the effects of the present invention are exhibited. Hereinafter, the characteristics of this polishing agent will be described in detail respectively.

[0014] B-1. Abrasive Grains In this polishing agent, the abrasive grains can be appropriately selected and used from those used as abrasive grains for CMP. One type of abrasive grain may be used alone, or two or more types may be used in combination. Examples of abrasive particles include at least one selected from the group consisting of silica particles, alumina particles, zirconia particles, cerium compound particles (e.g., ceria particles, cerium hydroxide particles, etc.), titania particles, germania particles, and composite particles thereof. Examples of silica particles include colloidal silica and fumed silica. Colloidal alumina can also be used as alumina particles. A composite particle is one in which particles with a smaller particle size (which may be of a different type than the particle) are attached to the surface of the particle. Among the abrasive particles mentioned above, silica particles or ceria particles are preferred because they offer superior polishing speed compared to boron-doped silicon.

[0015] When silica particles are used as abrasive grains, their high hardness results in an even better polishing speed for boron-doped silicon. Therefore, the proportion of silica particles in the abrasive grains is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass, relative to the total mass of the abrasive grains. On the other hand, when ceria particles are used as abrasive grains, their relatively low hardness suppresses the occurrence of defects on the polished surface. Therefore, the proportion of ceria particles in the abrasive grains is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass, relative to the total mass of the abrasive grains. Furthermore, if the abrasive grains contain silica particles or ceria particles, the silica or ceria content relative to the total mass of the abrasive grains is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass. If the silica or ceria content relative to the total mass of the abrasive grains is 70% by mass or more, there are fewer impurities, and it is easier to obtain a high polishing speed for boron-doped silicon.

[0016] Ceria particles can be appropriately selected from known types, for example, ceria particles produced by the methods described in Japanese Patent Publication No. 11-12561, Japanese Patent Publication No. 2001-35818, and Japanese Patent Publication No. 2010-505735. Specifically, examples include ceria particles obtained by adding alkali to an aqueous solution of cerium(IV) ammonium nitrate to produce a cerium hydroxide gel, which is then filtered, washed, and calcined; ceria particles obtained by crushing and calcining high-purity cerium carbonate, followed by further crushing and classification; and ceria particles obtained by chemically oxidizing cerium(III) salt in liquid. Ceria particles may contain impurities other than ceria, but the ceria content in a single ceria particle is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% or more, and most preferably 100% by mass (impurity-free). If the ceria content in the ceria particles is 80% by mass or more, a high polishing speed for boron-doped silicon is easily obtained.

[0017] Median particle size D of abrasive grains 50 From the viewpoint of suppressing the occurrence of polishing scratches such as scratches on the polished surface, a particle size of 0.01 μm or larger is preferred, and 0.015 μm or larger is more preferred. On the other hand, from the viewpoint of suppressing the aggregation of abrasive grains and improving the storage stability of the abrasive, a particle size of 0.5 μm or smaller is preferred, 0.3 μm or smaller is more preferred, and 0.25 μm or smaller is even more preferred. Note that "Median particle size D 50 "Median particle size D" refers to the particle size at which the frequency of accumulation from either the smaller or larger particle size side in the particle size distribution measured by a particle size distribution analyzer such as a laser diffraction / scattering type is 50%. 50 Because abrasive grains exist in the liquid as aggregated particles (secondary particles) formed by the aggregation of primary particles, the median particle size D of the secondary particles 50 It means...

[0018] From the viewpoint of increasing the polishing speed and enhancing the contribution of mechanical polishing in CMP to improve the flatness of the polished surface, the concentration of abrasive grains is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more, relative to the total mass of the abrasive. On the other hand, from the viewpoint of suppressing the viscosity of the abrasive and improving handling, the concentration is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 2% by mass or less, relative to the total mass of the abrasive.

[0019] B-2.Water This abrasive contains water as a medium for dispersing the abrasive particles and oxidizing agent. While there are no particular limitations on the type of water, it is preferable to use pure water, ultrapure water, or deionized water to prevent the inclusion of impurities and to consider the impact on pH, etc.

[0020] B-3. ​​Oxidizing agents The oxidizing agent contained in this abrasive includes at least one selected from peroxide oxidizing agents, metal ion oxidizing agents, and halogen oxoate ion oxidizing agents. These oxidizing agents are suitable as oxidizing agents for this abrasive because they efficiently react with boron on the surface to be polished in aqueous solution, generating reactive species specifically oxy radicals, metal ions with high oxidation states, and halogen oxoate ions.

[0021] Examples of peroxide oxidizing agents include hydrogen peroxide, persulfate ions (peroxodisulfate ions), or their salts (typically salts with ammonium, potassium, or sodium ions). Examples of halogen oxoate ion oxidizing agents include hypochlorite ions, chlorite ions, hypobromite ions, iodate ions, periodate ions, or salts thereof (typically salts with ammonium, potassium ions, or sodium ions). Examples of metal ion oxidizing agents include oxidizing agents containing metal cations such as silver(II) ions, cobalt(III) ions, cerium(IV) ions, iron(III) ions, and copper(II) ions, with transition metal ions being preferred as the metal ions. Examples of anions that bind to the metal ions include sulfate ions, nitrate ions, and chloride ions. Other examples of metal ion oxidizing agents include complex ions, metal oxoacid ions, or salts thereof (typically salts with ammonium, potassium ions, or sodium ions). Examples of complex ions include cerium(IV) nitrate ions, cerium(IV) sulfate ions, and hexacyanoferrate(III) ions. Examples of metal oxoacid ions include permanganate ions, vanadate ions, chromate ions, dichromate ions, and tungstate ions. The oxidizing agent contained in this abrasive may exist in the atmosphere as a hydrate. The oxidizing agent contained in this abrasive has sufficient water solubility to dissolve in the water in the abrasive. Specifically, the solubility of the oxidizing agent in water at 25°C is preferably 1 g / L or more, more preferably 10 g / L, and even more preferably 50 g / L or more.

[0022] From the viewpoint of increasing the polishing speed of boron-doped silicon, it is preferable to use a metal ion oxidizing agent among those mentioned above. In the case of metal ion oxidizing agents, it is preferable to have a high standard oxidation-reduction potential from the viewpoint of increasing the polishing speed of boron-doped silicon. Specifically, the standard oxidation-reduction potential is preferably 0.7V or higher, more preferably 0.8V or higher, even more preferably 1.5V or higher, and still more preferably 1.6V or higher. As for specific metal ion oxidizing agents, from the viewpoint of increasing the polishing speed of boron-doped silicon, oxidizing agents containing permanganate ions or cerium(IV) nitrate ions are preferably used. When the oxidizing agent contains permanganate ions, a good polishing rate can be obtained even at relatively high pH levels, such as when the pH of the polishing agent exceeds 2. On the other hand, when an oxidizing agent containing cerium(IV) nitrate ions is used as the metal ion oxidizing agent, the polishing rate of boron-doped silicon is even better. There are no particular restrictions on the upper limit of the standard oxidation-reduction potential of the metal ion oxidizing agent, but it is generally 2V or less.

[0023] Furthermore, the inventors have found that the polishing speed of this abrasive is further improved when it contains a certain amount or more of an oxidizing agent. This is presumed to be because a higher concentration of the oxidizing agent leads to a higher concentration of the active oxidizing agent, which reacts efficiently with the boron on the polished surface, thus accelerating the oxidation reaction. Specifically, the concentration of the oxidizing agent is preferably 0.5% by mass or more, more preferably 1.6% by mass or more, more preferably 2.2% by mass or more, and even more preferably 3% by mass or more, based on the total mass of the abrasive. On the other hand, from the viewpoint of increasing the contribution of mechanical polishing in CMP and improving the flatness of the polished surface, the concentration of the oxidizing agent is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less, relative to the total mass of the abrasive. Two or more of these oxidizing agents may be used in combination, in which case the total concentration should be within the above range. The concentration of the oxidizing agent is calculated based on the mass of the oxidizing agent in its atmospheric form. For example, if the oxidizing agent is a substance that exists stably as a hydrate in the atmosphere, its concentration in the abrasive is calculated from the mass of the hydrate.

[0024] B-4. Oxidation-reduction potential The inventors have found that by setting the oxidation-reduction potential of this abrasive to a certain value or higher, an even better polishing rate for boron-doped silicon can be obtained. This is presumed to be because the oxidation rate increases. Specifically, the oxidation-reduction potential of this abrasive at 23°C with reference to a standard hydrogen electrode is preferably 0.55V or higher, more preferably 0.65V or higher, more preferably 0.8V or higher, more preferably 0.9V or higher, more preferably 1V or higher, and more preferably 1.5V or higher. On the other hand, from the viewpoint of increasing the contribution of mechanical polishing in CMP and improving the flatness of the polished surface, a value of 2V or lower at 23°C is preferable. As will be explained in more detail in the examples, even if the oxidizing agent contained in the abrasive itself has a high standard oxidation-reduction potential, the overall oxidation-reduction potential of the abrasive does not necessarily show a high value. Furthermore, the oxidation-reduction potential of an abrasive is affected not only by the standard oxidation-reduction potential of the oxidizing agent, but also by the type and concentration of abrasive grains, and the type and concentration of other components such as pH adjusters. Therefore, by appropriately adjusting these factors, it is possible to set the oxidation-reduction potential of this abrasive to the target value.

[0025] B-5. Other ingredients This abrasive may contain other components to the extent that it achieves the effects of the present invention. Examples of other components include pH adjusters, polymers, anti-flocculation agents, dispersants, lubricants, viscosity modifiers, viscosity modifiers, preservatives, and other additives that can be used in known abrasives.

[0026] B-5-1. pH adjuster This abrasive may contain a pH adjuster to adjust the pH and oxidation-reduction potential of the abrasive to predetermined values. The pH adjuster can be appropriately selected from acidic compounds (excluding those corresponding to the oxidizing agent contained in this abrasive), basic compounds, amphoteric compounds such as amino acids, and salts thereof. Examples of acidic compounds include inorganic acids, organic acids, or salts thereof. Examples of inorganic acids include nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid, and ammonium salts, sodium salts, potassium salts, etc., of these may also be used. Examples of organic acids include compounds having a carboxyl group, a sulfo group, or a phospho group as an acidic group, and ammonium salts, sodium salts, potassium salts, etc., of these. Examples of basic compounds include ammonia and potassium hydroxide; quaternary ammonium hydroxides such as tetramethylammonium hydroxide and tetraethylammonium hydroxide; and organic amines such as monoethanolamine and ethylenediamine. pH adjusters can be used individually or in combination of two or more types. The concentration of the pH adjuster is not particularly limited as long as it is within the range that achieves the effects of the present invention, but as an example, it can be 0.0001% to 5% by mass relative to the total mass of the abrasive.

[0027] B-6. pH The pH of this abrasive is preferably less than 7 at 23°C. A pH of less than 7 improves the polishing speed of the surface to be polished, including boron-doped silicon. One method for adjusting the pH of this abrasive to less than 7 is to use the pH adjusting agent mentioned above. Among pH adjusting agents, it is preferable to use an acidic compound. The lower limit of the pH of this abrasive is generally 0 or higher, and from the viewpoint of improving handling, it is preferable that the pH of this abrasive at 23°C exceeds 2.

[0028] The method for preparing this abrasive can be appropriately selected from among methods in which abrasive particles, an oxidizing agent, and each component used as needed are uniformly dispersed or dissolved in water, which serves as the medium. For example, the abrasive may be prepared by preparing a dispersion of abrasive particles and an aqueous solution of the oxidizing agent separately, and then mixing them. This method offers excellent storage stability and ease of transport for the dispersion and aqueous solution. The mixing may also be performed within the polishing apparatus.

[0029] C. Polishing method The polishing method according to the present invention is a polishing method in which a polishing pad is brought into contact with the surface to be polished of a semiconductor substrate while supplying an abrasive, and polishing is performed by the relative movement of the two, wherein the abrasive according to the present invention is used as the abrasive, and the polishing method is used to polish a surface to be polished that contains boron-doped silicon.

[0030] A known polishing apparatus can be used for this polishing method. Figure 2 is a schematic diagram showing an example of a polishing apparatus. The polishing apparatus 20 shown in the example of Figure 2 comprises a polishing head 22 that holds a semiconductor substrate 21 having a surface to be polished containing boron-doped silicon, a polishing platen 23, a polishing pad 24 attached to the surface of the polishing platen 23, and a polishing agent supply pipe 26 that supplies polishing agent 25 to the polishing pad 24. The apparatus is configured to perform polishing by supplying polishing agent 25 from the polishing agent supply pipe 26, bringing the surface to be polished of the semiconductor substrate 21 held by the polishing head 22 into contact with the polishing pad 24, and rotating the polishing head 22 and the polishing platen 23 relative to each other.

[0031] The polishing head 22 may perform linear motion as well as rotational motion. Furthermore, the polishing platen 23 and polishing pad 24 may be approximately the same size as or smaller than the semiconductor substrate 21. In this case, it is preferable to move the polishing head 22 and the polishing platen 23 relative to each other so that the entire surface of the semiconductor substrate 21 can be polished. Moreover, the polishing platen 23 and polishing pad 24 do not necessarily have to perform rotational motion; for example, they may move in one direction using a belt system.

[0032] There are no particular restrictions on the polishing conditions of such a polishing apparatus 20, but the polishing pressure can be increased and the polishing speed improved by applying a load to the polishing head 22 and pressing it against the polishing pad 24. The polishing pressure is preferably around 0.5 to 50 kPa, and more preferably around 3 to 40 kPa from the viewpoint of uniformity, flatness, and prevention of polishing defects such as scratches on the polished surface of the semiconductor substrate 21 at the polishing speed. The rotation speed of the polishing platen 23 and the polishing head 22 is preferably around 50 to 500 rpm. In addition, the amount of polishing agent 25 supplied is appropriately adjusted depending on the composition of the polishing agent and the polishing conditions described above. If necessary, the pad conditioner may be brought into contact with the surface of the polishing pad 24 to condition the surface of the polishing pad 24 while polishing. This polishing method allows for high-speed polishing of surfaces containing boron-doped silicon.

[0033] D. Manufacturing method of semiconductor components The method for manufacturing semiconductor components according to the present invention involves obtaining semiconductor components by framing a semiconductor substrate having a polished surface polished by the polishing method according to the present invention.

[0034] The method for manufacturing a semiconductor component according to this disclosure includes a fragmentation step of fragmenting a semiconductor substrate having a polished surface polished by at least the polishing method described above. The fragmentation step may include, for example, a step of dicing the semiconductor substrate (e.g., a semiconductor wafer) by known methods such as blade dicing, laser dicing, or plasma dicing to obtain a semiconductor component which is a semiconductor chip. The method for manufacturing this semiconductor component may further include a bonding step of bonding another member to the polished surface of the semiconductor chip. This step yields a semiconductor component that is a bonded body. Other components include a second semiconductor chip and a redistribution layer. The second semiconductor chip may be a semiconductor chip obtained by the manufacturing method of this disclosure, or it may be a semiconductor chip obtained by another method. The bonding step may be, for example, a step of directly bonding the other component by placing it directly on the surface to be polished, such as by fusion bonding or surface activation bonding, or a step of bonding the surface to be polished and the other component via an adhesive layer. Examples of adhesive layers include solder, a metal layer such as copper, a glass layer, and a resin layer such as polyimide or epoxy. The disclosure can further provide an electronic device comprising at least one semiconductor component having a polished surface polished by the polishing method of the disclosure. [Examples]

[0035] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Examples 2-8 and 12-18 are examples, and Examples 1 and 9-11 are comparative examples.

[0036] <Preparation of abrasives> (Example 1) A polishing agent was prepared by adding silica particles as abrasive grains and potassium hydroxide as a pH adjuster to deionized water and mixing while stirring. The concentration of silica particles was 0.25% by mass relative to the total mass of the polishing agent. Median particle size D of the silica particles 50 It was 0.02 μm. (Example 2) A polishing agent was prepared by adding silica particles as abrasive grains and hydrogen peroxide as an oxidizing agent to deionized water and mixing while stirring. The concentration of silica particles was 0.25% by mass relative to the total mass of the polishing agent. Median particle size D of the silica particles 50 The particle size was 0.02 μm. The concentration of hydrogen peroxide was 5.0% by mass relative to the total mass of the abrasive. (Examples 3-8) The abrasives for each example were prepared in the same manner as in Example 2, except that the concentration of silica particles and the type and concentration of the oxidizing agent were as shown in Table 1. (Examples 9-11) The abrasive grains were ceria particles, the types of pH adjusters were as shown in Table 1, and the abrasives for each example were adjusted in the same manner as in Example 1 except that the concentration of the pH adjuster was changed. The median particle size D of the ceria particles 50 was 0.09 μm. (Examples 12 to 16) The abrasive grains were ceria particles, and the types and concentrations of the oxidizing agents were as shown in Table 1. The abrasives for each example were adjusted in the same manner as in Example 2. The median particle size D of the ceria particles 50 was 0.09 μm. (Example 17) Ceria particles as abrasive grains, hydrogen peroxide as an oxidizing agent, and nitric acid as a pH adjuster were added to deionized water and mixed while stirring to prepare an abrasive. The concentration of the ceria particles was 0.25% by mass based on the total mass of the abrasive. The median particle size D of the ceria particles 50 was 0.09 μm. The concentration of hydrogen peroxide was 0.15% by mass based on the total mass of the abrasive. (Example 18) The oxidizing agent was ammonium persulfate, its concentration was 1.0% by mass based on the total mass of the abrasive, and the abrasive was adjusted in the same manner as in Example 17 except that the concentration of nitric acid was changed.

[0037] In the abrasives of Example 1 and Examples 9 to 11 and Examples 17 to 18 containing a pH adjuster, the concentration of the pH adjuster was in the range of 0.001% by mass to 0.5% by mass based on the total mass of the abrasive. Also, in the abrasives of Examples 1 to 8, the content of silica based on the total mass of the abrasive grains was 95% by mass or more, and in Examples 9 to 18, the content of ceria based on the total mass of the abrasive grains was 95% by mass or more.

[0038] <Measurement method> For the abrasives of each of the above examples, each characteristic was evaluated by the following method. (pH) The pH was measured at 23°C using a pH meter (manufactured by Horiba Advanced Technology Co., Ltd., F-73 desktop pH meter, pH electrode: 9615S-10D).

[0039] (Redox potential) The oxidation-reduction potential (ORP) was measured at 23°C using an ORP meter (Horiba Advanced Technology Co., Ltd., F-73 benchtop pH meter, ORP electrode: 9301-10D). However, an Ag / AgCl electrode was used as the reference electrode, and a 3.33 mol / L KCl aqueous solution was used as the internal solution of the reference electrode. From the measured oxidation-reduction potential E, the oxidation-reduction potential E relative to the standard hydrogen electrode was calculated using the following formula. N.H.E. The result was calculated. [Formula 1] E N.H.E. =E+0.206-0.0007(t-25) (V)

[0040] (polishing speed) Polishing speed was evaluated using a fully automatic CMP system FREX300X (manufactured by Ebara Corporation). A two-layer polishing pad (top pad: DuPont, Ikonic 4250H) was used, and a diamond pad conditioner (Saesol, OH-AH8031) was used for conditioning the polishing pad. Polishing conditions were set to a polishing pressure of 5 psi, a polishing platen rotation speed of 100 rpm, and a polishing head rotation speed of 102 rpm. The abrasive supply rate was set to 250 ml / min. As the material to be polished, a boron-doped silicon film with a boron concentration of 50 at% atomic composition was used, deposited on a silicon substrate. The film thickness of the boron-doped silicon film was measured using a KLA-Tencor ASET-F5x film thickness gauge. The polishing speed was calculated by determining the difference between the film thickness of the boron-doped silicon film before polishing and the film thickness after polishing. Polishing time was set to 15 to 30 seconds. The average polishing speed (Å / min) obtained from the polishing speeds at 49 points in the plane of the boron-doped silicon film was used as the evaluation index for the polishing speed.

[0041] Table 1 shows the standard oxidation-reduction potential of the oxidizing agents for Examples 1-18, along with the pH, oxidation-reduction potential, and polishing rate of the polishing agents obtained from the above measurements.

[0042] [Table 1]

[0043] As shown in Table 1, abrasives containing oxidizing agents showed a higher polishing rate than abrasives without oxidizing agents. In particular, for Examples 10 and 11, although these abrasives did not contain oxidizing agents, they contained nitric acid and had a low pH, exhibiting a similar oxidation-reduction potential to some abrasives containing oxidizing agents, but their polishing rates were lower than those of abrasives containing oxidizing agents.

[0044] Figure 1 shows the relationship between the oxidation-reduction potential of the abrasives and the polishing rate obtained from the above measurements for abrasives Examples 2-7, which contain silica particles and an oxidizing agent, with an oxidizing agent concentration of 5.0% by mass. From Figure 1, it was shown that for abrasives containing abrasive grains, water, and an oxidizing agent, the higher the oxidation-reduction potential of the abrasive, the greater the tendency for the polishing rate to increase. Furthermore, the relative standard redox potentials of the oxidizing agents themselves are not necessarily reflected in the polishing speed. For example, the polishing agent in Example 3, which contains ammonium persulfate, the highest standard electrode potential among the oxidizing agents in Examples 2-7, showed the second lowest polishing speed among Examples 2-7. In other words, with this polishing agent, the redox potential of the entire polishing agent, rather than the standard redox potential of the oxidizing agent itself, influenced the polishing speed of boron-doped silicon, and a higher redox potential in the polishing agent tended to further improve the polishing speed.

[0045] In abrasives containing ceria particles and cerium(IV) ammonium nitrate as an oxidizing agent, Examples 12-14, where the concentrations of cerium(IV) ammonium nitrate were 5.0% by mass, 3.0% by mass, and 0.8% by mass relative to the total mass of the abrasive, did not show significant differences in the oxidation-reduction potential of the abrasive with respect to the difference in oxidizing agent concentration. On the other hand, regarding the polishing speed, Examples 12 and 13, with higher oxidizing agent concentrations, showed significantly higher values ​​than Example 14, with a lower oxidizing agent concentration. In other words, with this abrasive, there was a tendency for the polishing speed of boron-doped silicon to improve significantly when the oxidizing agent concentration was set above a certain value.

[0046] Examples 17 and 18 had lower concentrations of the oxidizing agent than Examples 15 and 16, which contained the same type of oxidizing agent. This abrasive tends to exhibit a higher polishing rate for boron-doped silicon with higher concentrations of the oxidizing agent. Therefore, it is presumed that if Examples 17 and 18 did not contain nitric acid, their polishing rates would be lower than those of Examples 15 and 16, respectively. However, Examples 17 and 18 contained nitric acid, which was not present in Examples 15 and 16, and showed higher redox potentials than Examples 15 and 16, respectively, while exhibiting polishing rates similar to those of Examples 15 and 16, respectively. In other words, this also confirms that the redox potential of the abrasive is an important factor in improving the polishing rate of boron-doped silicon in this abrasive. [Industrial applicability]

[0047] According to the present invention, for example, a high polishing speed can be achieved in CMP of a surface to be polished containing boron-doped silicon. Therefore, the polishing agent of the present invention is suitable for polishing hard masks containing boron-doped silicon in semiconductor device manufacturing.

[0048] This application claims priority based on Japanese Patent Application No. 2022-162113, filed on 7 October 2022, and incorporates all of its disclosures herein. [Explanation of Symbols]

[0049] 20... Polishing device, 21... Semiconductor substrate, 22... Polishing head, 23... Polishing platen, 24... Polishing pad, 25... Polishing compound, 26... Polishing compound supply piping.

Claims

1. A polishing agent for polishing a surface to be polished, containing boron-doped silicon, It contains abrasive particles, an oxidizing agent, and water. The oxidizing agent comprises at least one selected from peroxide oxidizing agents, metal ion oxidizing agents, and halogen oxoate ion oxidizing agents. The concentration of the oxidizing agent is 1.6% to 20% by mass relative to the total mass of the abrasive. Abrasive.

2. The abrasive according to claim 1, wherein the oxidation-reduction potential at 23°C, based on a standard hydrogen electrode, is 0.55 V or higher.

3. The abrasive according to claim 1, wherein the oxidizing agent includes a metal ion oxidizing agent.

4. The polishing agent according to claim 3, wherein the oxidizing agent comprises a metal ion oxidizing agent having a standard oxidation-reduction potential of 0.7 V or higher.

5. The abrasive according to claim 3, wherein the metal ion oxidizing agent contains cerium(IV) nitrate ions.

6. The abrasive according to claim 3, wherein the metal ion oxidizing agent contains permanganate ions.

7. The abrasive according to claim 1, comprising an acidic compound other than the oxidizing agent.

8. The abrasive according to claim 1, wherein the pH at 23°C is less than 7.

9. The abrasive according to claim 1, wherein the abrasive grains include silica particles.

10. The abrasive according to claim 1, wherein the abrasive grains include ceria particles.

11. The abrasive according to claim 1, wherein the boron concentration in the boron-doped silicon is 0.5 at% to 90 at% in terms of atomic composition percentage.

12. A polishing method comprising supplying an abrasive while bringing a polishing pad into contact with the surface to be polished of a semiconductor substrate and performing polishing by the relative movement of the two, wherein the abrasive is one of the abrasives described in any one of claims 1 to 11, and the surface to be polished contains boron-doped silicon.

13. A method for manufacturing a semiconductor component, comprising obtaining a semiconductor component by framing a semiconductor substrate having a polished surface polished by the polishing method described in Claim 12.

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