Polishing liquid and polishing method using polishing liquid

Abstract

To provide a polishing liquid capable of further reducing surface roughness and restraining over-polishing such as dishing and erosion in association with enhancement of integration and multi-layering of circuits and implement higher flatness while improving cleanability after polishing.SOLUTION: A polishing liquid contains silica particles, a complexing agent, a film-forming agent, and one or more kinds of polyol compounds selected from the group consisting of glycerin or polyglycerin having an average polymerization degree of 1 to 20 calculated from the hydroxyl value, and polyoxyalkylene polyol ethers in which 0 to 100 alkylene oxides are added to one hydroxyl group in the molecular structure of glycerin or polyglycerin, and is used to polish metal films formed on wafers.SELECTED DRAWING: None

Description

[Technical field]

[0001] In particular, the present invention relates to a polishing liquid used in the manufacture of semiconductor devices and a polishing method using this polishing liquid. [Background technology]

[0002] In recent years, semiconductor elements have become increasingly miniaturized, with circuits on the wafer surface becoming more highly integrated and circuit wiring becoming more multi-layered, making flattening the wafer surface even more important in these manufacturing processes, and polishing by CMP (Chemical Mechanical Polishing) is widely used for this purpose. This polishing method contains chemicals and abrasive grains, and chemically dissolves the material to be polished while physically scraping it to flatten the surface.

[0003] Regarding polishing by CMP, for example, Patent Document 1 proposes a polishing composition containing a cationic water-soluble polymeric compound containing a nitrogen-containing group in order to suppress haze (uneven surface roughness) that may occur during polishing when planarizing the wafer surface, and to achieve a high polishing rate.

[0004] Patent Document 2 proposes a polishing composition that can achieve high circuit integration while maintaining the flatness of the wafer surface, in response to the increasing use of copper, which has low electrical resistance, as a wiring material in the formation of circuit patterns on a wafer surface.

[0005] In forming a circuit pattern, after wiring grooves and holes are formed on the insulating film layer on the surface of the wafer, the wafer is covered with a metal film by sputtering, plating, etc., and then unnecessary metal film portions on the insulating film layer other than the portions filled in the wiring grooves and holes are removed by CMP. In particular, it is necessary to prevent erosion, in which the insulating film in the wiring grooves and holes to be polished and the surrounding areas where wiring is densely packed becomes thinner than areas without wiring grooves or holes, and dishing, in which the center of the wiring groove width where metal is filled becomes slightly depressed.

[0006] Uneven surface roughness and over-polishing such as erosion and dishing can have a significant impact on the integration / multi-layering of wiring circuits as well as on the functions and performance of semiconductor elements, so they are things that should be avoided when planarizing the wafer surface, and various proposals have been made as mentioned above. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2006-352042 A [Patent Document 2] JP 2005-136134 A Summary of the Invention [Problem to be solved by the invention]

[0008] In the current situation where the demand for flattening the wafer surface, such as further reduction in surface roughness and suppression of overpolishing such as erosion and dishing, is extremely high along with the high integration and multi-layering of circuits, the various currently proposed measures are not sufficient. Therefore, the present invention aims to provide a polishing liquid that can meet such demands and achieve higher flatness while improving the cleanability after polishing. [Means for solving the problem]

[0009] The polishing liquid according to the present invention contains silica particles, a complexing agent, a film-forming agent, and one or more polyol compounds selected from the group consisting of glycerin, polyglycerin, and polyoxyalkylene polyol ether in which 0 to 100 alkylene oxides are added to one hydroxyl group in the molecular structure of glycerin or polyglycerin, each having an average degree of polymerization of 1 to 20 calculated from the hydroxyl value, and is used for polishing a metal film formed on a wafer, thereby solving the above-mentioned problems.

[0010] The present invention also provides a polishing liquid in which the content of the film-forming agent in the polishing liquid is less than the content of the film-forming agent in a polishing liquid that contains silica particles, a complexing agent, and a film-forming agent but does not contain a polyol compound.

[0011] The present invention provides a polishing liquid in which the glycerin or polyglycerin constituting the polyol compound of the polishing liquid has a molecular structure with a degree of branching (DB) within the range of 0 to 0.25.

[0012] The present invention takes advantage of the characteristics of the polishing liquid described above to provide a polishing treatment method for polishing a metal film formed on a wafer, using a polishing liquid containing silica particles, a complexing agent, a film-forming agent, and a polyol compound, with the content of the film-forming agent being less than that in the case where the polishing liquid does not contain the polyol compound.

[0013] The present invention provides a polishing method in which the content of the film-forming agent in the polishing liquid is less than the content of the film-forming agent in the polishing liquid containing silica particles, a complexing agent and a film-forming agent but not a polyol compound, and the glycerin or polyglycerin constituting the polyol compound in the polishing liquid has a molecular structure with a branching degree (DB) in the range of 0 to 0.25. Effect of the Invention

[0014] By adding a polyol compound to the polishing liquid, the barrier properties of the film-forming agent are enhanced, the effect of suppressing corrosion of the polished surface is improved, and overpolishing such as dishing and erosion can be suppressed while maintaining a high polishing rate, thereby providing a wafer having high flatness. Furthermore, by further containing a polyol compound, corrosion that may occur at the contact site of different metals is prevented at the same time as the overpolishing.

[0015] Regarding post-cleaning after the polishing process, by incorporating a polyol compound, the content of the film-forming agent in the polishing liquid can be reduced, and further, in the post-cleaning process, the protective film formed by the film-forming agent can be removed without leaving any residue, together with the polishing liquid used and impurities due to the polishing process, thereby improving cleaning properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described. Note that the embodiment is merely an example for understanding the present invention, and the present invention is not limited to the embodiment.

[0017] The polishing liquid of the present invention contains silica particles, a complexing agent, and a film-forming agent, and is characterized in that it contains one or more polyol compounds selected from the group consisting of glycerin, polyglycerin, and polyoxyalkylene polyol ethers in which 0 to 100 alkylene oxides are added to one hydroxyl group in the molecular structure of glycerin or polyglycerin, and each of which has an average degree of polymerization of 1 to 20 as calculated from the hydroxyl value.

[0018] The average degree of polymerization of glycerin and polyglycerin according to the present invention is calculated from the hydroxyl value by terminal analysis using the following formulas (1) and (2). The hydroxyl value in formula (2) is a numerical value that indicates the magnitude of the number of hydroxyl groups contained in glycerin and polyglycerin, and refers to the number of milligrams of potassium hydroxide required to neutralize the acetic acid required to acetylate the free hydroxyl groups contained in 1 g of glycerin and polyglycerin. The number of milligrams of potassium hydroxide is calculated in accordance with "Standard Testing Methods for Analysis of Fats, Oils and Related Materials, 2013 Edition, Established by Japan Oil Chemists' Society," edited by Japan Oil Chemists' Society. Molecular weight=74n+18 (1) Hydroxyl number = 56110(n+2) / molecular weight (2)

[0019] The polishing liquid of the present invention is based on chemical mechanical polishing (hereinafter sometimes referred to as "CMP") and contains a component having a mechanical polishing action by abrasive grains and a component having a chemical polishing action that dissolves or alters the polishing surface by using a chemical, etc. Furthermore, these components do not only act independently during polishing, but are selected and blended so as to mutually enhance their actions.

[0020] <About the semiconductor manufacturing process> First, the semiconductor manufacturing process in which the polishing liquid of the present invention is used will be described. The semiconductor manufacturing process mainly consists of a front-end process of manufacturing wafers (hereinafter sometimes referred to as the "wafer manufacturing process") and a back-end process of assembling and inspecting the manufactured wafers. The front-end wafer manufacturing process mainly consists of a bare wafer processing / cleaning process, a film forming process, a lithography / etching process, an ion implantation process, an interlayer insulating layer forming process, a circuit wiring process, and an inspection process, and is carried out in this order, or in some processes, by returning to the previous process once and repeating it once or multiple times. Among these, the main processes in which CMP is used will be described below.

[0021] The bare wafer processing and cleaning process is a process in which bare wafers are sliced ​​from a single crystal ingot, the surface of the sliced ​​bare wafer is polished and flattened, and the surface is cleaned after polishing to produce a mirror-like wafer. In this process, the circuit elements such as gates, sources, drains, etc. that make up semiconductor elements and circuits made of circuit wiring are created on the wafer surface in the subsequent process, and the circuit wiring is laminated, so flattening the surface is very important, and polishing is performed by CMP (hereinafter sometimes referred to as "CMP polishing process"). In this case, CMP polishing process is mainly performed on bare wafers.

[0022] The film formation process is a process in which an insulating film such as an oxide film or a nitride film is formed on the wafer surface that has been planarized in the bare wafer processing and cleaning process. This process mainly forms an insulating film layer between circuit elements or stacked circuit wiring, a film layer for forming a shallow trench isolation (STI) structure, or a protective layer that physically and chemically protects the circuit elements, circuit wiring, and insulating layer. The film formation process in this process is also used appropriately in processes such as forming a metal film layer, which will be described later.

[0023] Shallow trench isolation (STI) is an element isolation structure that electrically insulates multiple semiconductor elements formed on the wafer surface by creating trenches between them, and is widely used to increase the integration density of semiconductor elements.

[0024] The main methods for generating the above-mentioned film layer include thermal oxidation, CVD (chemical vapor deposition), PVD (physical vapor deposition), and plating. Plating is a method that is often used when forming copper wiring in the circuit wiring process described below, and specifically, a metal is deposited on the wafer surface by applying an electric current to a plating solution using the wafer as the cathode and a copper plate as the anode, forming a thin metal film.

[0025] Copper has a lower electrical resistance than aluminum, which has traditionally been used as a wiring material, and is therefore widely used to achieve and maintain high integration in semiconductor circuits. In recent years, as wiring has become finer, metal wiring materials such as cobalt and ruthenium have also come to be used. After the metal film for wiring is deposited in the circuit wiring process, it is thinned by CMP polishing, and this processing capability is extremely important.

[0026] In order to meet the increasing demands for higher circuit integration and multi-layering, the insulating film layers and protective layers generated in the film formation process and in each process are subjected to CMP polishing to make the film thickness thin and uniform and to smooth out surface irregularities.

[0027] The properties of the insulating film layer and the protective layer described above can greatly affect the performance and function of the semiconductor element, such as the voltage resistance between circuit elements, prevention of leakage current generation or internal resistance between circuit elements, and interlayer insulation accompanying lamination of circuit wiring layers described later, so that the polishing state is controlled and managed very precisely during processing. Among the processing conditions, the polishing speed in particular has a great effect on the mass productivity and production efficiency of semiconductor manufacturing, so that speeding up is being promoted. On the other hand, increasing the polishing speed can cause surface defects such as surface roughness and scratches on the wafer surface during polishing. Therefore, in CMP, in order to achieve both an improvement in the polishing speed and a reduction in surface roughness and surface defects while achieving a uniform thin film and thickness of the insulating film layer or protective layer, the properties and characteristics of CMP are adjusted, such as the selection of abrasive grains and the chemical components to be contained, and the adjustment of the blending amount. The polishing liquid of the present invention will be described later.

[0028] The interlayer insulating layer forming process is a process in which an interlayer insulating layer is formed on each circuit element formed in the ion implantation process by a film forming process such as a CVD method, which provides electrical insulation for the circuit wiring formed in the circuit wiring process described below and between the circuit wiring layers when they are stacked in layers. The interlayer insulating layer is mainly made of an oxide film or a nitride film. Low-dielectric materials are also used as an interlayer insulating layer that supports the wiring material.

[0029] In this process, as in the above-mentioned film formation process, in order to accommodate the increasing integration and multi-layering of circuits, the generated interlayer insulating layer is subjected to a CMP polishing process that takes into consideration the increase in the polishing speed, making the film thickness thin and uniform and flattening the surface.

[0030] In the circuit wiring process, the interlayer insulating layer is subjected to lithography and etching to form wiring grooves for embedding metal circuit wiring material, that is, trench patterns. In the lithography and etching process, a trench pattern is formed by applying a photosensitive material (photoresist) onto the interlayer insulating layer, irradiating / exposing the layer to light through a mask on which a circuit wiring pattern is formed, and then developing and etching the layer along the transferred circuit wiring pattern.

[0031] In this process, it is particularly important to maintain a stable exposure state by suppressing the effects of light reflection, diffusion, etc., during transfer of the trench pattern. That is, in order to ensure a stable exposure state when forming a trench pattern compatible with fine circuit wiring in the circuit wiring process, the CMP polishing process requires a higher degree of flatness without fine irregularities or undulations on the surface of the interlayer insulating layer.

[0032] As already mentioned above, the circuit wiring process is a process in which a trench pattern and contact holes for circuit wiring are formed on the interlayer insulating layer generated in the interlayer insulating layer generation process, and a metal film of a circuit wiring material is deposited in the trench pattern and contact hole to generate a layer on which circuit wiring is formed (hereinafter, sometimes referred to as a "circuit wiring layer"). Furthermore, in this process, interlayer insulating layer generation, trench pattern formation, metal film deposition, and circuit wiring formation are sequentially repeated multiple times on the formed circuit wiring layer, and a three-dimensional circuit wiring layer is generated while stacking the formed circuit wiring layers.

[0033] A contact hole is a hole, such as a via, that is used to electrically connect a circuit element created on a wafer to the circuit wiring. During circuit wiring processing, a metal film is deposited in this hole as described above, and wiring is created that electrically connects the circuit wiring to the circuit element, along with metal electrodes for the source and drain.

[0034] In the circuit wiring process, a CMP polishing process is performed to remove excess metal film that has accumulated on the interlayer insulating layer other than in the trench pattern and contact holes when creating the circuit wiring layer, and to flatten the surface of the circuit wiring layer.

[0035] In the CMP polishing process in the circuit wiring process, since the circuit wiring layer is formed by forming metal circuit wiring on an interlayer insulating layer, the surface is polished against different materials, that is, the oxide or nitride film constituting the interlayer insulating layer and the metal for the circuit wiring. Furthermore, since the surface resistance of these materials differs when polished, the polishing solution in the polishing process in this process is different from that in other processes, taking into consideration the differences in material properties such as hardness and solubility in chemical solutions of these materials, and based on these material properties, adjustments are made to effectively exert the effects of both mechanical polishing and chemical polishing.

[0036] Next, each component contained in the polishing liquid of the present invention will be described below.

[0037] <About Silica Particles> The silica particles contained in the polishing liquid of the present invention function as abrasive grains that mechanically polish the wafer surface to flatten it. In addition, the silica particles contribute to the mechanical action in the polishing by CMP, and the type and content of the particles to be used can be set while taking into consideration the chemical action of other components described later.

[0038] Regarding silica particles, examples of silica include amorphous silica, crystalline silica, fused silica, spherical silica, synthetic silica, hollow silica, fumed silica, colloidal silica, etc. Among these, abrasive grains containing colloidal silica and fumed silica are particularly preferred, and abrasive grains containing colloidal silica are more preferred. In addition, the silica particles may be surface-modified.

[0039] The content of silica particles in the polishing liquid of the present invention is preferably 0.1 to 10 mass % based on the total amount of the polishing liquid, taking into consideration both high polishing speed and high flatness of the wafer surface.

[0040] <About complexing agents> The complexing agent contained in the polishing liquid of the present invention coordinates with metal ions to form a complex, and has the effect of dissolving metal ions in water or capturing and inactivating metal. As a result, the metal fine particles generated when polishing the metal film on the wafer surface are dissolved in this complexing agent, and a high polishing rate can be maintained while suppressing clogging of the polishing pad. Furthermore, since the fine particles of the scraped metal are dissolved, deposition in the polishing liquid is suppressed, and over-polishing such as scratches on the wafer surface, erosion, and dishing of metal wiring caused by these scraped fine powders during polishing is effectively prevented.

[0041] The complexing agent contained in the polishing liquid of the present invention includes organic acids, organic acid salts, organic acid esters, etc. Examples of organic acids include carboxylic acids (acetic acid, propionic acid, benzoic acid, lactic acid, malonic acid, succinic acid, citric acid, malic acid, diglycolic acid, isophthalic acid, methylsuccinic acid, oxalic acid, tartaric acid, picolinic acid, phthalic acid, adipic acid, glutaric acid), sulfonic acids, and amino acids. Examples of amino acids include glycine, alanine, leucine, aspartic acid, etc. Examples of organic acid salts include ammonium salts, etc. Examples of organic acid esters include aminoacetic acid, etc. Among these, amino acids are particularly preferred, and glycine is more preferred. The complexing agent may be contained alone or in combination of two or more.

[0042] The content of the complexing agent in the polishing liquid of the present invention can be 0.01 to 20 mass % based on the total amount of the polishing liquid, from the viewpoint of maintaining and improving processing efficiency in terms of polishing rate, etc., and preventing overpolishing and erosion.

[0043] <About film-forming agents> The film-forming agent contained in the polishing liquid of the present invention has the effect of preventing the surface to be polished from being excessively corroded by forming a complex with the metal. When removing excess metal film on the wafer surface by polishing, the chemical polishing action of the polishing liquid may corrode the metal film in the required area by etching, oxidation, etc. When contained in the polishing liquid, this film-forming agent forms a complex with the metal during the polishing process, forming a protective film on the surface of the metal film that suppresses corrosion.

[0044] Regarding this protective film, for example, in the circuit wiring process, a metal film formed on the surface of an interlayer insulating layer of a wafer is polished together with the protective film formed thereon while being flattened by the mechanical polishing action of this polishing liquid. At that time, the part where the excess metal film exists has undulations and thickness compared to other parts, and is polished by coming into contact with the abrasive grains or polishing pad first, so that the protective film of the metal film deposited in the recesses of a trench pattern, etc. is polished sequentially while remaining, preventing corrosion of the metal film in the recesses.

[0045] That is, the film-forming agent forms a protective film on the metal film during polishing, so that overpolishing such as dishing and erosion that may occur in the circuit wiring can be suppressed while maintaining a high polishing rate, and high-level planarization can be promoted. In addition, by containing a polyol compound together with this film-forming agent, the barrier properties of the protective film can be further improved, and it is possible to effectively prevent bimetallic corrosion (galvanic corrosion) that may occur in the circuit wiring together with the above-mentioned overpolishing. This point will be described in detail later.

[0046] The film-forming agent contained in the polishing liquid of the present invention includes compounds having a triazole skeleton, compounds having an imidazole skeleton, compounds having a pyrimidine skeleton, compounds having a guanidine skeleton, compounds having a thiazole skeleton, compounds having a pyrazole skeleton, etc., and the compounds having a triazole skeleton include 1,2,4-triazole, 1,2,3-triazole, benzotriazole, 5-methylbenzotriazole, etc., and the compounds having an imidazole skeleton include imidazole, benzimidazole, etc., and nitrogen-containing cyclic compounds having amino, imino, and mercapto are included. Among these, the triazole skeleton is particularly preferred.

[0047] The content of the film-forming agent in the polishing liquid of the present invention can be 0.001 to 2 mass % based on the total amount of the polishing liquid, from the viewpoint of maintaining and improving processing efficiency in terms of polishing speed, etc., and preventing overpolishing and corrosion.

[0048] <About polyol compounds> The polyol compound contained in the polishing liquid of the present invention contributes to the wettability of the polished surface, and when contained together with the film-forming agent, has the function of suppressing the corrosive action that may occur during polishing, and is a compound that makes it possible to promote high flatness while maintaining a higher polishing rate. In addition, this component is highly water-soluble and acts favorably in cleaning after polishing.

[0049] This component has a high affinity with water and has the effect of promoting the wettability of the polished surface that becomes wet with the polishing liquid during polishing processing, so when it is contained together with a film-forming agent, it functions as a protective film and enhances the barrier properties of the protective film formed on the polished surface by this film-forming agent. Therefore, even if only the film-forming agent is added to the polishing liquid, over-polishing such as dishing and erosion that may occur during polishing processing can be suppressed, but by also containing this component, it is possible to obtain a similar excellent suppression effect even if the content of the film-forming agent is reduced compared to the content of the film-forming agent in the polishing liquid containing silica particles, a complexing agent, and a film-forming agent, that is, the content of the film-forming agent in the polishing liquid not containing a polyol compound.

[0050] Furthermore, by containing this component, corrosion at contact sites between dissimilar metals present on the wafer, so-called galvanic corrosion, is also suppressed.

[0051] Regarding galvanic corrosion, for example, in a circuit wiring process, a metal for circuit wiring is first deposited in recesses such as trench patterns to prevent the metal from diffusing onto the wafer after the circuit is formed, and then a layer is deposited and laminated on top of the metal for diffusion prevention. The layer on which the metal for diffusion prevention is deposited functions as a barrier layer to prevent the diffusion of the metal for circuit wiring.

[0052] In the circuit wiring formed in this manner, since the metal for the circuit wiring and the metal for the barrier layer are different materials and there are portions where the dissimilar metals are in contact with each other, it is necessary to take measures to prevent galvanic corrosion, which mainly occurs when the metal for the circuit wiring is polished.

[0053] In response to this situation, the present component enhances the barrier properties of the protective film formed by the film-forming agent, thereby suppressing the occurrence of galvanic corrosion that may occur with overpolishing. Furthermore, even if the amount of the film-forming agent is small, the inclusion of the present component can exert a similar inhibitory effect.

[0054] The content of the polyol compound contained in the polishing liquid of the present invention can be 0.01 to 5 mass % based on the total amount of the polishing liquid in order to increase processing efficiency in terms of polishing speed, etc., to suppress overpolishing, erosion and corrosion, and to improve the post-cleaning properties described below.

[0055] The content of the polyol compound is preferably greater than the content of the film-forming agent, which enhances the action of this component and the synergistic effect with the film-forming agent, thereby achieving a higher degree of flatness on the wafer surface and more effective post-cleaning properties.

[0056] Regarding the post-cleaning, this component also has a good effect on the cleaning process after forming the circuit wiring on the wafer. If unnecessary impurities such as the polishing solution used, metal particles from the removed excess metal film, and particles from the removed protective film remain on the wafer after the polishing process, they will greatly affect the function and performance of the semiconductor device, such as malfunction and failure. In this cleaning process, post-cleaning is performed so that these impurities do not remain on the wafer.

[0057] The polishing liquid of the present invention contains a polyol compound, so that even if the amount of the film-forming agent is reduced as described above, the barrier properties of the protective film can be obtained similar to that of the case where the compound is not contained. As a result, the content of the film-forming agent is reduced compared to the case where the polyol compound is not contained, and therefore the amount of the film-forming agent to be cleaned is reduced, as well as the amount of the protective film that needs to be removed and the amount of fine particles of the protective film that are generated, and the post-cleaning is simplified, making it possible to improve the cleaning properties of the wafer.

[0058] In addition, the polishing liquid of the present invention contains a polyol compound, and thus has the effect of suppressing the fluctuation of the corrosion potential of the metal between the polishing state during the polishing process and the polishing state during the stop of the polishing process (hereinafter referred to as the "non-polishing state"), and stabilizing the corrosion potential between the two states. Note that the corrosion potential is the potential that occurs when the metal dissolves in the polishing liquid and exhibits a corrosion reaction.

[0059] By including a polyol compound in this polishing liquid, the barrier properties of the protective film formed by the film-forming agent are enhanced while fluctuations in corrosion potential are suppressed, and stable etching is promoted, so that the polishing rate can be adjusted and maintained to ensure good polishing conditions.

[0060] From the viewpoint of maintaining and achieving high polishing properties, corrosion resistance, and cleaning properties at the same time, the degree of branching (DB) of the glycerin or polyglycerin constituting the polyol compound contained in the polishing liquid of the present invention is preferably 0 to 0.25. Here, the degree of branching (DB) will be explained.

[0061] The structural units constituting glycerin and polyglycerin can be broadly classified into a structure in which only one of the primary hydroxyl groups of glycerin is etherified (hereinafter referred to as a "Terminal Structure"), a structure in which one primary hydroxyl group and a secondary hydroxyl group are etherified (hereinafter referred to as a "Linear 1,3 Structure"), a structure in which both primary hydroxyl groups are etherified (hereinafter referred to as a "Linear 1,4 Structure"), and a structure in which all three hydroxyl groups are etherified (hereinafter referred to as a "Dendritic Structure").

[0062] In addition, each of the above structural units is 13 They can be classified based on measurements by C-NMR, and the amount of each structure is 13 It is calculated based on the integral ratio of the peaks assigned to the carbon at a specific position of each structure, namely, the terminal structure, the linear 1,3 structure (L13), the linear 1,4 structure (L14), and the dendritic structure (D), from the results of C-NMR measurement.

[0063] The degree of branching (DB) can be calculated by the formula: degree of branching (DB) = 2D / (2D + L13 + L14), and the degree of branching (DB) is preferably within the range of 0 to 0.25. This reduces the number of structures having branched portions in glycerin and polyglycerin, and the barrier properties and washability of the protective film can be further improved.

[0064] <Other ingredients> The polishing liquid of the present invention may further contain other components as desired, as long as the effects of the polishing liquid are not hindered. In one or more embodiments, the other components include at least one selected from an oxidizing agent, a pH adjuster, a water-soluble polymer, and a surfactant. Each component is described below.

[0065] <About oxidizing agents> The oxidizing agent contained in the polishing liquid of the present invention oxidizes the surface to be polished and mainly acts to improve the polishing rate. For example, when polishing a metal film laminated on the wafer surface, it oxidizes the metal film and functions as a metal dissolving agent. By including this oxidizing agent, the metal film is weakened and high polishing properties of the CMP abrasive grains and polishing pad are maintained. Furthermore, by using it in combination with a complexing agent, the chemical polishing action by etching and the mechanical polishing action of the abrasive grains on the oxidized metal film can be obtained, and the polishing rate can be improved while ensuring higher polishing properties and suppressing overpolishing and corrosion.

[0066] The oxidizing agent contained in the polishing liquid of the present invention includes an oxidizing metal salt and an oxidizing non-metallic compound. The oxidizing metal salt includes sulfate, nitrate, iron salt, aluminum salt, potassium salt, permanganate, etc. The oxidizing non-metallic compound includes hydrogen peroxide, potassium periodate, ammonium persulfate, hypochlorous acid, ozone water, etc. As the oxidizing agent, hydrogen peroxide is preferable in terms of stability after addition. The oxidizing agents can be used alone or in combination of two or more.

[0067] The content of the oxidizing agent in the polishing liquid of the present invention can be 0.01 to 3 mass % based on the total amount of the polishing liquid in order to increase processing efficiency in terms of polishing speed, etc., and to suppress overpolishing, erosion, and corrosion.

[0068] The polishing liquid of the present invention can be adjusted to a desired pH by adding a pH adjuster. In this case, for example, if the pH of the polishing liquid is decreased, that is, if the acidity is increased, the chemical polishing action due to etching of the complexing agent increases, and conversely, if the pH is increased, that is, if the alkalinity is increased, the surface is weakened due to oxidation of the metal, and the mechanical polishing action due to the abrasive grains increases. In addition, in the range of pH 5 to 9, the chemical polishing action and the mechanical polishing action are well balanced. Note that these pH values ​​are set mainly from the viewpoint of manufacturability, such as the polishing speed, processing accuracy for the polishing process, and quality. In this way, by adjusting the function and performance of the polishing liquid by the pH adjuster, it is possible to improve high polishing properties and polishing speed while suppressing overpolishing and corrosion.

[0069] Regarding water-soluble polymers and surfactants, by including them in the polishing liquid, they affect the liquid properties such as viscosity, surface tension, and adsorption / repulsion, and are adsorbed onto the particle interfaces of the abrasive grains and the interlayer insulating film layer, thereby making it possible to appropriately adjust the polishing rate with the polishing liquid while ensuring high polishing properties and suppressing overpolishing and corrosion.

[0070] <About this polishing liquid> In one or more embodiments, the polishing liquid of the present invention may contain water. Examples of water include ion-exchanged water and ultrapure water, and ultrapure water is preferred from the viewpoint of suppressing overpolishing and corrosion while improving the polishing rate and ensuring high cleaning properties. The content of water in the polishing liquid of the present invention may be, for example, the remainder of silica particles, complexing agent, film-forming agent, polyol compound, and other components.

[0071] The polishing liquid of the present invention may be used as a concentrated liquid from the viewpoint of storage stability until use and convenience during management and use. In this case, it can be diluted with water when used and an oxidizing agent can be added as necessary, and each component can be diluted so that its content falls within the above-mentioned range. By doing so, it is possible to improve manufacturability and reduce manufacturing costs.

[0072] <Suitable forms for applying this polishing liquid> In the semiconductor manufacturing process, the polishing liquid of the present invention can be suitably used in the processing step of processing and forming a layer made of one or more metals on a wafer, and is particularly preferably applied to the circuit wiring step of forming metal wiring for forming each semiconductor element and circuit on the wafer.

[0073] In the circuit wiring process, it is necessary to remove excess metal deposited in areas other than the trench pattern and contact holes while suppressing overpolishing, and to flatten the polished surface. In this regard, the polishing solution of the present invention is suitable for use because it can flatten the polished surface by suppressing overpolishing of the metal film due to the action of the polyol compound film-forming agent to enhance the barrier properties, while allowing the chemical polishing action of etching, etc. by the complexing agent to cooperate with the mechanical polishing action of the silica particles.

[0074] At this time, since the interlayer insulating layer also contains the metal for the barrier layer that was deposited as a base before laminating the metal for the circuit wiring, this metal for the barrier layer is also polished in the circuit wiring process. Since this polishing liquid has an effect of suppressing galvanic corrosion on a surface having a metal film, it can prevent corrosion at the contact site between the dissimilar metals, the metal for the circuit wiring and the metal for the barrier layer.

[0075] In the circuit wiring process, a multi-layered three-dimensional structure is generated by stacking circuit wiring layers. If the circuit wiring layers are not flat, for example, due to significant surface undulations, surface roughness, or uneven layer thickness, the multi-layered three-dimensional structure may not have a predetermined thickness or may be distorted or irregular. This may have a significant impact on the function and performance of the semiconductor element due to poor electrical response of the circuit wiring or poor electrical contact between the circuit wiring layers.

[0076] The polishing liquid of the present invention, by taking into account the above-mentioned action of the polyol compound, can provide a highly flat polished surface for a surface composed of different materials, that is, an oxide film or nitride film forming an interlayer insulating layer and a metal for circuit wiring, and can fully prevent the semiconductor element from becoming in the above-mentioned state.Furthermore, since it has high cleaning properties, there are few objects that need to be cleaned, such as fine particles generated after polishing, and no treatment using special cleaning components is required, so it can be used preferably while ensuring high flatness for multilayering, and can improve productivity for cleaning treatment, including cost reduction.

[0077] Here, an example of a polishing method using the polishing liquid of the present invention will be described. In the polishing process, a wafer having a trench pattern, contact holes, and a metal deposited on an interlayer insulating layer is first placed on a polishing machine, and then the surface of the wafer on which the metal is deposited is pressed against a polishing pad attached to a rotating platen of the polishing machine with a predetermined pressure. At this time, the polishing liquid of the present invention is dispensed between the wafer and the polishing pad, and the surface to be polished is polished at a predetermined rotation speed while being pressed in a state of being constantly in contact with the polishing liquid.

[0078] The metal film deposited on the surface to be polished is polished by mechanical polishing by the silica particles of this polishing liquid and chemical etching by the complexing agent, while the protective action of the film-forming agent prevents over-polishing of the metal film and corrosion. At this time, the polishing liquid further contains a polyol compound, which improves the barrier properties of the protective film, and therefore the polishing process can be performed with improved polishing efficiency, for example, by increasing the rotation speed.

[0079] In addition, in the polishing method using this polishing liquid, the content of the film-forming agent is made smaller than that in the case where the polishing liquid does not contain the polyol compound. Therefore, the burden of post-polishing of the wafer after the polishing process is reduced, and the polishing process can be performed with improved processability and cleanability at the same time. In addition, the polyol compound contained together with the film-forming agent is water-soluble, so it also greatly contributes to improving the cleanability.

[0080] Regarding the preparation of the polishing liquid during the polishing process, the polishing liquid of the present invention may be prepared in advance and placed in a predetermined container or the like provided in the polishing machine, or the polishing liquid may be prepared in the polishing machine and then supplied to the polishing pad for use. Also, a concentrated solution of the polishing liquid of the present invention may be supplied to the polishing machine together with dilution water, and mixed in the polishing machine including piping, etc., to prepare the polishing liquid of the present invention and supply it to the polishing pad at the same time. Either preparation method can be used in the polishing process to which the present polishing liquid is applied.

[0081] Wafers to which the present polishing liquid can be applied include silicon wafers, glass substrates for TFT-LCDs, substrates made of compound semiconductors such as GaAs, etc. As described above, the metal material to be laminated on the wafer may be copper (Cu), copper alloys, silver (Ag), silver alloys, cobalt (Co), ruthenium (Ru), aluminum (Al), aluminum alloys, tungsten (W), tungsten alloys, or oxides of these metals, or metals containing small amounts of impurities or additive elements.

[0082] Examples of dissimilar metal materials to the above-mentioned metal materials include titanium, titanium nitride, tantalum, tantalum nitride, copper, tungsten, cobalt, ruthenium, aluminum, aluminum alloys such as aluminum / copper alloys, and various mixtures and combinations of these metals.

[0083] <Example> The polishing liquid of the present invention will be described in detail below with reference to examples. In this example, the wafer used was a silicon wafer, and a copper circuit wiring was formed on the surface of the wafer on a barrier layer of titanium and titanium nitride. The surface of the wafer on which the copper circuit wiring was formed was used as the surface to be polished, and polishing was performed using the polishing liquid of each example described below, and various measurements and evaluations were made of the polishing state at that time. Note that the following examples are merely illustrative examples for understanding the polishing liquid, and the present invention is not limited to these examples.

[0084] <Regarding the polishing liquids of Examples 1 to 7> The polishing liquid in each example was prepared by stirring and mixing the components in Table 1 or the specified content shown below. Example 1 contained 1 mass% colloidal silica as silica particles, 2 mass% glycine as a complexing agent, 0.01 mass% benzotriazole as a film forming agent, 0.5 mass% glycerin (manufactured by Sakamoto Yakuhin Kogyo Co., Ltd. (purified glycerin)) as a polyol compound, 1 mass% hydrogen peroxide as an oxidizing agent, and water as the remainder. The above amounts of components are based on the total mass of the polishing liquid, including values ​​in the comparative examples described below.

[0085] In Examples 2 to 5, only the component as the polyol compound was changed from that in Example 1, and the content was kept at 0.5 mass% as in Example 1. Specifically, in Examples 2 to 5, polyglycerin having a chain-like molecular structure with different molecular weights was used, and in Example 2, polyglycerin having an average degree of polymerization of 4 and an average molecular weight of 310 ("Polyglycerin #310" manufactured by Sakamoto Pharmaceutical Co., Ltd.) was used, in Example 3, polyglycerin having an average degree of polymerization of 10 and an average molecular weight of 750 ("Polyglycerin #750" manufactured by Sakamoto Pharmaceutical Co., Ltd.) was used, and in Examples 4 and 5, polyglycerin having an average degree of polymerization of 15 and an average molecular weight of 1100 (manufactured by Sakamoto Pharmaceutical Co., Ltd.) was used. In addition, in the above Examples 1 to 5, glycerin and polyglycerin with a branching degree (DB) of 0 to 0.25 were used.

[0086] In Example 6, a polyoxyalkylene polyglyceryl ether ("SC-E350" manufactured by Sakamoto Pharmaceutical Co., Ltd.) having an average molecular weight of 350 in which the number of alkylene oxides having 2 carbon atoms added is 4 relative to the hydroxyl groups in the molecular structure of polyglycerin having an average degree of polymerization of 2 calculated from the hydroxyl value, and in Example 7, a polyoxyalkylene polyglyceryl ether ("SC-E750" manufactured by Sakamoto Pharmaceutical Co., Ltd.) having an average molecular weight of 750 in which the number of alkylene oxides having 2 carbon atoms added is 13 relative to the hydroxyl groups of polyglycerin having an average degree of polymerization of 2 calculated from the hydroxyl value, was used. In addition, glycerin in the polyoxyalkylene polyglyceryl ether and polyglycerin with a branching degree (DB) of 0 to 0.25 were used.

[0087] <Regarding the polishing solutions of Comparative Examples 1 to 6> The polishing liquids of Comparative Examples 1 to 6 were prepared by stirring and mixing the components at the predetermined content in the same manner as in Examples 1 to 5. Comparative Example 4 did not contain (0 mass%) benzotriazole (BTA) as a film forming agent, as compared to Examples 1 to 7, and polyglycerin was 0.5 mass% polyglycerin with an average degree of polymerization of 15 and an average molecular weight of 1100, as in Example 4. Comparative Examples 1 to 3 did not contain (0 mass%) polyol compound, as compared to Examples 1 to 7, and only the content of benzotriazole (BTA) was increased; specifically, the content of benzotriazole (BTA) in Comparative Example 1 was 0.01 mass%, in Comparative Example 2 it was 0.03 mass%, and in Comparative Example 3 it was 0.05 mass%.

[0088] A description will be given of the polyhydric alcohol in the polishing liquid used in Comparative Examples 5 and 6. In Comparative Example 5, polyethylene glycol having an average molecular weight of 1000 was used as the polyhydric alcohol, and in Comparative Example 6, polypropylene glycol having an average molecular weight of 1000 was used.

[0089] Details of the components contained in the polishing liquids of Examples 1 to 7 and Comparative Examples 1 to 6, and their contents, etc. are shown in Table 1.

[0090] <Various measurement methods> The dishing depth of the metal layer was measured using an atomic force microscope, specifically, a general-purpose small unit AFM5100N and a cantilever PRC-DF40P (manufactured by Hitachi High-Tech Corporation).

[0091] In addition, the post-cleaning state of the wafer after polishing was also measured. The polished surface of the wafer polished with this polishing liquid was scrubbed, rinsed with pure water, and then dried. The polished surface was then subjected to X-ray photoelectron spectroscopy to measure the N1s spectrum and investigate the peak intensity derived from benzotriazole (BTA). × N1s peak is sharply detected ○ N1s peak is slightly detected

[0092] <Polishing conditions> Regarding the polishing conditions with the polishing liquid in this example, the equipment used was a tabletop automatic polishing machine DiaWrap AceML-160A (manufactured by Maruto Co., Ltd.), and the polishing pad was IC1000 made of polyurethane having a highly uniform fine foam structure. TM and IC1000 with non-woven continuous foam structure TM / SUBA TM A lamination pad XY-perforated (manufactured by Nitta DuPont Co., Ltd.) was used.

[0093] The polishing pressure on the surface of the wafer to be polished was set to 4.10 psi, the head / platen rotation speed of the automatic polishing machine was set to 100 rpm, and the supply rate of the polishing liquid was set to 12 ml / min., and the polishing process was performed.

[0094] The polishing speed during the polishing process was also measured as a polishing condition. The measurement method was based on the relationship between the surface resistance of copper and the film thickness, which had been previously investigated and examined, and was calculated as follows: polishing speed (nm / min.) = (film thickness before polishing - film thickness after polishing) / polishing time.

[0095] <Measurement results / evaluation> The results of measuring the polishing state after polishing using the polishing liquid of the present invention are shown in Table 1. It can be seen from Table 1 that in all of Examples 1 to 7, the dishing depth is very small compared to Comparative Example 1, which does not contain a polyol compound. From these measurement results, it can be confirmed that by including a polyol compound in this polishing liquid, the effect of suppressing overpolishing such as dishing and corrosion is improved, and the polished surface is highly planarized.

[0096] When the above-mentioned inhibitory action was examined from another perspective, it was found that the dishing depth was clearly greater in Comparative Example 4, which contained a film-forming agent and a polyol compound and had the smallest dishing depth, compared to Example 4, which did not contain a film-forming agent (does not contain a film-forming agent). From this result, it can be confirmed that the inhibitory action against overpolishing and corrosion is improved by including a polyol compound together with a film-forming agent.

[0097] In Comparative Examples 2 and 3, polishing was performed using a polishing solution containing no polyol compound and containing only an increased amount of film-forming agent compared to 0.01% by mass in Comparative Example 1. It can be seen that the dishing depth at this time decreases with an increase in the amount of film-forming agent, and the amount is approximately the same as the dishing depth in Examples 1 to 7, which contain a polyol compound and contain a lower amount of film-forming agent than Comparative Examples 2 and 3. From these results, it can be confirmed that, due to the high suppression effect of the above-mentioned polyol compound on overpolishing and corrosion, a highly flat polished wafer surface can be obtained by containing a polyol compound, even if the amount of film-forming agent is less than that in the case of not containing the polyol compound.

[0098] [Table 1]

[0099] Table 1 shows the results of an investigation and confirmation of the state of the polished surface by the post-cleaning process after the polishing process (hereinafter sometimes referred to as the "cleaning state"), particularly with regard to the film-forming agent. It can be seen that, with regard to the cleaning state of the polished surface by the post-cleaning in Examples 1 to 5, only a small peak derived from the film-forming agent BTA was detected. From this, by adding a polyol compound to this polishing liquid, the content of the film-forming agent during the polishing process can be reduced, improving the cleaning properties.

[0100] In addition, in Comparative Examples 2 and 3, which do not contain a polyol compound, the dishing depth is small and the polishing state is good, but in terms of cleaning, the peak intensity derived from the film-forming agent BTA is detected in Table 1. This is presumed to be a situation in which a protective film formed by the film-forming agent remains on the polished surface of a wafer having a metal wiring layer and is not removed by the polishing process. Therefore, even if the content of the film-forming agent is increased to suppress overpolishing and corrosion, the protective film remains, and there is concern that the cleaning ability will be reduced due to the burden of a new cleaning process, such as removal by additional polishing or etching with the addition of a dedicated chemical, or that new overpolishing and corrosion will occur due to the additional polishing process, resulting in a decrease in polishing ability.

[0101] On the other hand, in the case of containing the polyol compound of Examples 1 to 7, the peak intensity derived from BTA was not detected, so that by containing the polyol compound in this polishing liquid, the content of the film-forming agent is reduced as described above, and no protective film remains, so that not only does it affect polishing properties, but also the addition of a new chemical solution is unnecessary, and the post-cleaning property after polishing processing is improved. In addition, the polyol compound contained in this polishing liquid together with the film-forming agent is water-soluble, so it greatly contributes to improving the post-cleaning property after polishing processing. [Industrial Applicability]

[0102] The polishing liquid of the present invention can be used to perform polishing treatment so as to obtain a high degree of flatness while suppressing the occurrence of overpolishing such as dishing and erosion and corrosion when forming circuit wiring on the surface of a wafer. Furthermore, the polishing liquid has good cleaning properties even in post-cleaning after the polishing treatment, and is highly manufacturable, including cost, and can provide semiconductor elements that meet the needs for high integration and multi-layering. Furthermore, the polishing liquid can be suitably used in the semiconductor manufacturing process, particularly in the process of forming a metal layer on a wafer.

Claims

1. The polishing liquid contains silica particles, a complexing agent, a film-forming agent, and one or more polyol compounds selected from the group consisting of glycerin, polyglycerin, and polyoxyalkylene polyol ethers in which 0 to 100 alkylene oxides are added to one hydroxyl group in the molecular structure of glycerin or polyglycerin, the average degree of polymerization being 1 to 20 as calculated from the hydroxyl value, and is used for polishing a metal film formed on a wafer.

2. A polishing liquid characterized in that the content of the film-forming agent in the polishing liquid described in claim 1 is less than the content of the film-forming agent in a polishing liquid containing silica particles, a complexing agent and a film-forming agent but not containing the polyol compound.

3. 3. The polishing liquid according to claim 1, wherein the glycerin or polyglycerin constituting the polyol compound has a molecular structure with a degree of branching (DB) in the range of 0 to 0.

25.

4. A polishing method for polishing a metal film formed on a wafer, comprising using a polishing liquid containing silica particles, a complexing agent, a film-forming agent, and the polyol compound, and setting the content of the film-forming agent to a smaller amount than when the polishing liquid does not contain the polyol compound.

5. A polishing method characterized in that the content of the film-forming agent in the polishing liquid described in claim 4 is less than the content of the film-forming agent in the polishing liquid containing silica particles, a complexing agent and a film-forming agent but not a polyol compound.

6. 6. The polishing method according to claim 4, wherein the glycerin or polyglycerin constituting the polyol compound has a molecular structure with a degree of branching (DB) in the range of 0 to 0.25.

Images