Substrate processing method

Abstract

This substrate processing method involves processing a substrate having, on a surface thereof, a metal layer and a hard mask laminated on the metal layer. The method includes: a step in which the metal layer exposed by the hard mask is patterned through dry etching; a step in which residue produced on the substrate surface by the dry etching is irradiated with ultraviolet light; and a step in which, after the ultraviolet light irradiation, the residue from the substrate is removed by wet treatment involving supplying a residue removal liquid having a pH (hydrogen ion index) of 7-14 to the substrate surface. The residue includes one or more compounds among a metal halide compound, an organometallic substance, and a metal oxide containing the main constituent metal element of the metal layer.

Description

[Technical Field]

[0001] The present invention relates to a substrate processing method. Substrates to be processed include semiconductor wafers, substrates for FPDs (Flat Panel Displays) such as liquid crystal display devices and organic EL (Electroluminescence) display devices, ceramic substrates, substrates for solar cells, etc. The method of the present invention is particularly suitable for substrate processing in which a metal layer formed on the surface is dry-etched. [Background technology]

[0002] The process of forming a multilayer wiring layer on a semiconductor substrate after forming active devices and the like on the semiconductor substrate is called BEOL (Back End of Line: wiring process). The multilayer wiring layer includes an interlayer insulating film, a metal wiring layer, and vias formed in the interlayer insulating film. The vias are formed by forming through-holes (via openings) in the interlayer insulating film and filling the through-holes with metal (via metal). Different wiring layers are connected via the vias.

[0003] A process for forming a multilayer wiring layer is described, for example, in Patent Document 1. Patent Document 1 lists aluminum, ruthenium, cobalt, cobalt-aluminum alloy, tungsten, molybdenum, nickel, rhodium, iridium, zinc, and copper as materials for the conductive film that forms the wiring. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-19006 Summary of the Invention [Problem to be solved by the invention]

[0005] Ruthenium and molybdenum have been attracting attention as metal materials for forming multilayer wiring layers in the structures of miniaturized semiconductor devices in recent years. For example, the semi-damascene process has been proposed as a multilayer wiring formation technology using ruthenium. The semi-damascene process is a technology in which, after a via opening is formed in an interlayer insulating film, a via metal that fills the via opening and an upper layer wiring film are simultaneously deposited. After deposition, the wiring film is patterned into a wiring pattern by direct metal etching. The use of a metal material that can be subjected to direct metal etching makes the semi-damascene process applicable.

[0006] Direct metal etching is a process in which a hard mask is formed on the wiring film and unnecessary portions of the wiring film are removed by dry etching through the hard mask. Residues resulting from dry etching are left on the surface of the semiconductor substrate after dry etching, so a cleaning process (residue removal process) is required to remove these residues. This cleaning process requires cleaning performance that minimizes damage to the hard mask and wiring, while removing the residues as efficiently as possible. Damage to the wiring, i.e., film reduction, leads to increased wiring resistance. Furthermore, residues left between wiring increase the risk of leakage between wiring. Therefore, both of these factors affect the electrical characteristics of the final product.

[0007] Therefore, one embodiment of the present invention provides a substrate processing method for efficiently removing residues remaining after dry etching of a metal layer while suppressing damage to the metal layer. [Means for solving the problem]

[0008] One embodiment of the present invention provides a substrate processing method having the following features.

[0009] 1. A substrate processing method for processing a substrate having a metal layer and a hard mask laminated on the metal layer, the method comprising: patterning the metal layer exposed from the hard mask by dry etching; a step of irradiating with ultraviolet light a residue generated on the surface of the substrate by the dry etching, the residue including one or more of a metal oxide, a metal halide, and an organometallic substance containing an element of a main constituent metal of the metal layer; and removing the residue from the substrate by wet processing after the irradiation of ultraviolet rays, by supplying a residue removal solution having a pH (hydrogen ion exponent) of 7 or more and 14 or less (more preferably 8 or more and 14 or less, and even more preferably 10 or more and 14 or less) to the surface of the substrate.

[0010] According to this method, the metal layer is dry-etched through the hard mask, thereby patterning the hard mask. Therefore, the main constituent metal of the metal layer is a metal material that can be patterned by dry etching. The main constituent metal refers to the metal material excluding trace amounts of additives that may be contained in the metal layer.

[0011] Dry etching is a plasma process in which etching proceeds by attacking exposed portions of a metal layer with activated species in a processing gas. After dry etching, a residue (dry etching residue) containing compounds (metal compounds) of the main constituent metal elements of the metal layer and the constituent elements of the processing gas remains on the substrate. Specifically, the compounds that make up the residue include at least one of metal oxides, metal halides, and organometallic substances.

[0012] Ultraviolet light is irradiated onto the residue. The ultraviolet light breaks the chemical bonds of the compounds contained in the residue, modifying the residue and facilitating its removal by subsequent wet processing. After this preprocessing, wet processing is performed by supplying a residue-removing liquid, thereby removing the residue from the substrate surface. By using a processing liquid with a pH of 7 or more and 14 or less (more preferably 8 or more and 14 or less, and even more preferably 10 or more and 14 or less) as the residue-removing liquid, the residue can be efficiently removed.

[0013] According to experiments conducted by the inventors, residues could not be removed efficiently with an acidic processing solution (an acidic processing solution), whereas residues could be removed efficiently with an alkaline processing solution (a neutral or alkaline processing solution, more preferably an alkaline processing solution). Furthermore, acidic processing solutions corrode oxide films and the like on the substrate, damaging the structure on the substrate. From this perspective as well, it is appropriate to use an alkaline processing solution as a residue removal solution.

[0014] The ultraviolet irradiation performed before supplying the residue removal solution is a non-contact treatment, and while it affects the residue, it does not substantially cause physical damage to other structures on the substrate (metal layers, insulating layers, etc.). Therefore, unlike plasma treatment, etc., it can selectively act on the chemical bonds of the residue, so it has little effect on the properties of the final product manufactured through the substrate treatment.

[0015] 2. A substrate processing method for processing a substrate having a surface on which a hard mask and a metal layer patterned by dry etching through the hard mask are formed, and on which a residue resulting from the dry etching includes one or more of a metal oxide, a metal halide, and an organometallic substance containing an element of a main constituent metal of the metal layer is generated, the method comprising: irradiating the residue with ultraviolet light; and removing the residue from the substrate by wet processing after the irradiation of ultraviolet rays, by supplying a residue removal solution having a pH (hydrogen ion exponent) of 7 or more and 14 or less (more preferably 8 or more and 14 or less, and even more preferably 10 or more and 14 or less) to the surface of the substrate.

[0016] The method of this embodiment is directed to a substrate after a metal layer has been patterned by dry etching, and the method of this embodiment also provides the same functions and effects as the above-described method.

[0017] 3. The substrate processing method according to item 1 or 2, wherein the metal layer contains, as the main constituent metal, at least one selected from a group of metal materials including molybdenum, ruthenium, aluminum, and metal compounds of these metals.

[0018] For example, the substrate processing method of this embodiment can be applied to a wiring formation process for forming a wiring layer (typically a multi-layer wiring layer) on a substrate. Specifically, a metal layer is formed from a wiring metal material, and a hard mask corresponding to the wiring pattern is formed on the metal layer and then dry-etched, whereby the metal layer can be patterned into a wiring pattern.

[0019] For example, materials for forming fine wiring in semiconductor devices are selected taking into consideration resistivity, diffusibility into other material layers, etc. In semi-damascene technology, which is one of the wiring formation technologies used to form multilayer wiring on a semiconductor substrate, the conditions for selecting a wiring metal material are that it has an acceptable resistivity for the wiring film, can be deposited without a diffusion barrier, and can be patterned by dry etching (direct metal etching). Examples of metals that satisfy these conditions include molybdenum, ruthenium, and aluminum, as well as molybdenum-based, ruthenium-based, or aluminum-based metal compounds.

[0020] By applying the substrate processing method of this embodiment, it is possible to reduce the risk of leakage between wirings due to residues, and also to reduce the risk of an increase in resistivity due to a reduction in the wiring film during residue removal processing.

[0021] 4. The substrate processing method according to any one of items 1 to 3, further comprising an atmosphere control step of controlling the atmosphere around the substrate during irradiation with ultraviolet light to a low-oxygen atmosphere having an oxygen concentration lower than the oxygen concentration in the atmosphere.

[0022] When ultraviolet light is irradiated in an atmosphere with a high oxygen concentration, ozone is generated, which may cause oxidation of the metal layer. If metal oxide is formed on the surface of the metal layer and is etched with the residue removal solution, the metal layer will be thinned. Therefore, by irradiating ultraviolet light in a low-oxygen atmosphere, the risk of thinning of the metal layer can be reduced.

[0023] 5. The substrate processing method according to item 4, wherein the atmosphere control step includes an inert gas supply step of supplying an inert gas around the substrate.

[0024] 6. The substrate processing method according to any one of items 1 to 5, wherein the ultraviolet rays have energy equal to or greater than the bond energy of at least one compound selected from the group consisting of metal oxides, metal halides, and organometallic substances contained in the residue.

[0025] This method can modify the residue by severing the chemical bonds of at least one of the metal oxides, metal halides, and organometallic substances in the residue through ultraviolet irradiation, thereby enabling the residue to be efficiently removed by the residue removal solution.

[0026] The residue remaining on the surface of the substrate after dry etching typically contains a metal compound formed by bonding the main constituent metal of the metal layer to be etched with the constituent elements of the processing gas used for dry etching. By using ultraviolet light with a wavelength that can be absorbed by the residue and with energy equal to or greater than the bond energy between the main constituent metal and the constituent elements of the processing gas, the residue can be modified into a substance that is easily removed by a residue removal solution.

[0027] For example, when the main constituent metal is molybdenum and the residue contains a compound in which molybdenum is bonded to one or more elements of carbon, chlorine, oxygen, and fluorine, the ultraviolet light preferably has an energy of 465 kJ / mol or more (preferably, 596 kJ / mol or more). Because the molybdenum compound can absorb the energy of ultraviolet light, the bonds of at least a part of the molybdenum compound can be broken by irradiation with ultraviolet light, thereby modifying the residue.

[0028] 7. The substrate processing method according to any one of items 1 to 6, wherein the ultraviolet light increases the hydrophilicity of the surface of the metal layer.

[0029] This method increases the hydrophilicity of the surface of the metal layer, making it easier for the residue-removing liquid to penetrate. Therefore, even if the metal layer is patterned into a fine structure, the residue-removing liquid can penetrate into the fine structure, allowing the residue to be removed efficiently.

[0030] 8. The main constituent metal is molybdenum, 8. The substrate processing method according to any one of items 1 to 7, wherein the ultraviolet light has a wavelength of 257 nm or less (more preferably 201 nm or less).

[0031] Irradiation with ultraviolet light in the wavelength range of 257 nm or less can provide the energy necessary to sever the bonds in the compound in which molybdenum is bonded to at least one element selected from carbon, chlorine, oxygen, and fluorine, thereby effectively modifying the residue. More preferably, irradiation with ultraviolet light in the wavelength range of 201 nm or less can almost completely sever the chemical bonds in the molybdenum compound in which molybdenum is bonded to carbon, chlorine, oxygen, and fluorine, thereby more effectively modifying the residue.

[0032] 9. The substrate processing method according to any one of items 1 to 8, wherein the residue removal solution does not contain an oxidizing agent and contains one or more selected from ammonium hydroxide, TMAH (tetramethylammonium hydroxide aqueous solution), and a polymer removal solution.

[0033] A polymer removal liquid is a chemical liquid used to remove photoresist residues that have undergone a plasma process. Known polymer removal liquids include liquids containing organic alkaline liquids, liquids containing organic acids, liquids containing inorganic acids, and liquids containing ammonium fluoride-based substances. Of these, those with a pH of 7 or more and 14 or less (more preferably, 8 or more and 14 or less, and even more preferably, 10 or more and 14 or less) can be used. Specifically, a liquid containing an organic alkaline liquid can be used as a residue removal liquid. Examples of liquids containing an organic alkaline liquid include liquids containing at least one of DMF (dimethylformamide), DMSO (dimethyl sulfoxide), hydroxylamine, and choline. Other examples of polymer removal liquids that can be used as residue removal liquids include liquids containing at least one of 1-methyl-2-pyrrolidone, tetrahydrothiophene 1.1-dioxide, isopropanolamine, monoethanolamine, 2-(2-aminoethoxy)ethanol, catechol, N-methylpyrrolidone, aromatic diol, perclene (tetrachloroethylene), and liquids containing phenol. More specifically, examples include at least one of a mixture of 1-methyl-2-pyrrolidone, tetrahydrothiophene 1.1-dioxide, and isopropanolamine, a mixture of dimethyl sulfoxide and monoethanolamine, a mixture of 2-(2-aminoethoxy)ethanol, hydroxylamine, and catechol, a mixture of 2-(2-aminoethoxy)ethanol and N-methylpyrrolidone, a mixture of monoethanolamine, water, and aromatic diol, and a mixture of perclene (tetrachloroethylene) and phenol. Other examples include liquids containing at least one of amines such as triethanolamine and pentamethyldiethylenetriamine, propylene glycol, and dipropylene glycol monomethyl ether.

[0034] 10. The substrate processing method according to any one of items 1 to 9, wherein the hard mask is made of an inorganic material.

[0035] For example, the hard mask may be made of a silicon nitride film. [Brief explanation of the drawings]

[0036] [Figures 1A-1D] 1A to 1D are schematic cross-sectional views sequentially showing a part of a manufacturing process for a semiconductor device to which a substrate processing method according to an embodiment of the present invention can be applied. [Figure 2] FIG. 2 is a cross-sectional view showing the structure of a cross section taken along line II-II in FIG. 1A. [Figure 3A-3C] 3A, 3B and 3C are schematic cross-sectional views for explaining a substrate processing method according to an embodiment of the present invention. [Figure 4] Figure 4 is a micrograph of the sample after dry etching of the molybdenum layer through the hard mask. [Figures 5A-5C] 5A, 5B, and 5C are micrographs showing a state in which a residue removal process is performed by supplying a processing liquid to a processing target surface of a sample without irradiating the surface with ultraviolet light. [Figures 6A-6C] 6A, 6B, and 6C are micrographs showing a state in which a surface to be treated of a sample is irradiated with ultraviolet light and then a treatment liquid is supplied to perform a residue removal treatment. [Figure 7] FIG. 7 is a diagram for explaining another effect of ultraviolet irradiation, showing the effect of increasing hydrophilicity due to ultraviolet irradiation. DETAILED DESCRIPTION OF THE INVENTION

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0038] 1A to 1D are schematic cross-sectional views sequentially showing a part of a manufacturing process of a semiconductor device to which a substrate processing method according to an embodiment of the present invention can be applied. FIG. 2 is a cross-sectional view showing the structure of a cross section taken along line II-II in FIG. 1A. Here, a part of BEOL (Back End of Line: wiring process) in which a multilayer wiring layer 2 is formed on the surface of a silicon substrate 1 as an example of a semiconductor substrate is shown. Also, an example in which one metal wiring layer constituting the multilayer wiring layer 2 is formed by a semi-damascene process will be described. In the following description, the term "substrate 50" refers to the entire structure including the silicon substrate 1 and various films (insulating films, metal films, resist films, etc.) formed on its surface.

[0039] 1A and 2, devices such as transistors (active devices and / or passive devices) are formed on the surface layer of a silicon substrate 1, and a multilayer wiring layer 2 is formed on the main surface on which the devices are formed.

[0040] The multilayer wiring layer 2 includes interlayer insulating films 11 and 12 and a plurality of metal wiring layers 21 and 22. The interlayer insulating films 11 and 12 are typically made of silicon oxide. A metal wiring layer 21 (lower metal wiring layer) is formed above the interlayer insulating film 11. This metal wiring layer 21 may be made of, for example, copper, ruthenium, molybdenum, or the like. Although not shown in detail, the metal wiring layer 21 is typically patterned into a desired wiring pattern. Another interlayer insulating film 12 is formed on the metal wiring layer 21. Another metal wiring layer 22 (upper metal wiring layer) is formed on this interlayer insulating film 12. In this embodiment, this metal wiring layer 22 is formed by a semi-damascene process.

[0041] Specifically, a via opening 12a is formed in the interlayer insulating film 12, penetrating the interlayer insulating film 12 in the film thickness direction to expose the underlying metal wiring layer 21. An upper metal wiring layer 22 is formed on the interlayer insulating film 12. At the stage of FIG. 1A, this metal wiring layer 22 covers the entire surface of the interlayer insulating film 12 and has a via metal portion 22a (see FIG. 2) embedded in the via opening 12a. Here, as an example, the main constituent metal of the metal wiring layer 22 is molybdenum. For example, the molybdenum metal wiring layer 22 can be formed by plasma CVD (chemical vapor deposition).

[0042] A hard mask 5 (film before patterning) is laminated on the metal wiring layer 22, covering its entire surface. The hard mask 5 is typically made of an inorganic insulating material, such as silicon nitride, which is an example of an inorganic insulating material. An amorphous carbon layer 6 (in a state before patterning) is formed on the hard mask 5, covering its entire surface. A photoresist mask 7 is formed on the surface of the amorphous carbon layer 6, for patterning the metal wiring layer 22 into a desired wiring pattern. This photoresist mask 7 has been patterned through an exposure process and a development process. The photoresist mask 7 and the amorphous carbon layer 6 constitute a multilayer resist for patterning the hard mask 5.

[0043] Next, as shown in FIG. 1B, the amorphous carbon layer 6 is etched by dry etching using the photoresist mask 7 as a mask. As a result, the pattern of the photoresist mask 7 is transferred to the amorphous carbon layer 6, and the surface of the hard mask 5 is selectively exposed through the openings (through holes) formed in the amorphous carbon layer 6. When the dry etching is further continued, the hard mask 5 is etched by dry etching using the amorphous carbon layer 6 as a mask. As a result, the pattern of the amorphous carbon layer 6 is transferred to the hard mask 5, and the metal wiring layer 22 is selectively exposed through the openings (through holes) formed in the hard mask 5. After this etching, a cleaning process is performed to remove residue of the photoresist mask 7 remaining after the dry etching. This state is shown in FIG. 1B.

[0044] Next, as shown in FIG. 1C, etching (for example, wet etching) is performed to remove the amorphous carbon layer 6, and then the surface of the substrate 50 is cleaned.

[0045] 1D, the metal wiring layer 22 is etched by dry etching using the hard mask 5 as a mask. As a result, the pattern of the hard mask 5 is transferred to the metal wiring layer 22. As a result, the metal wiring layer 22 is patterned into a desired wiring pattern. This process is so-called direct metal etching, and in this case, a wiring pattern made of molybdenum is formed on the interlayer insulating film 12 by direct metal etching of the metal wiring layer 22 made of molybdenum.

[0046] The wiring pattern may have, for example, a plurality of linear wirings 22W extending in a direction intersecting the plane of the paper in FIG. 1D. The surface of the interlayer insulating film 12 is exposed between adjacent wirings 22W, and these wirings 22W are insulated from each other. An air gap may be formed between adjacent wirings 22W, or an insulating material may be embedded between the adjacent wirings 22W. At least one wiring 22W has a via metal portion 22a (see FIG. 2) embedded in a via opening 12a formed in the interlayer insulating film 12, and is three-dimensionally connected to the underlying metal wiring layer 21 via the via metal portion 22a.

[0047] In this example, the semi-damascene process includes forming a via opening 12a in the interlayer insulating film 12, forming a metal wiring layer 22 that fills the via opening 12a and covers the interlayer insulating film 12, and patterning the metal wiring layer 22 by direct metal etching.

[0048] Direct metal etching of the metal wiring layer 22 through the hard mask 5 is performed by dry etching, more specifically reactive ion etching. Such dry etching involves a plasma process in which a process gas for etching is introduced into a process chamber and the process gas is irradiated with electromagnetic waves such as microwaves to generate plasma. This generates activated species of the process gas, which are then introduced to the metal wiring layer 22, thereby performing anisotropic etching, which etches the metal wiring layer 22 in its thickness direction.

[0049] After this dry etching, compounds (metal compounds) of the metal material constituting the metal wiring layer 22 and the constituent elements of the processing gas remain as residues 10 (see FIG. 3A) on the surface of the substrate 50. In particular, residues 10 remaining between the wirings 22W, specifically residues remaining on the side walls and bottoms of the openings 23 between the wirings 22W, can cause leakage between the wirings, and therefore require residue removal processing.

[0050] The residue removal process must be able to remove the residue 10 while minimizing its impact on other structures on the substrate 50. In particular, a process that corrodes the wiring 22W is undesirable because it may reduce the thickness of the wiring 22W and increase the resistivity of the wiring 22W. Furthermore, a process that corrodes the hard mask 5 is undesirable because it may increase the exposed portions of the wiring 22W, potentially leading to a reduction in the thickness of the wiring 22W. Furthermore, a process that corrodes the interlayer insulating film 12 underlying the metal wiring layer 22 is undesirable because it may increase the risk of leakage between the upper and lower metal wiring layers 21 and 22 and affect the capacitance between them.

[0051] Typically, the process gas used for dry etching is a fluorine-based gas (e.g., CF4, CHF3, SF6) or a chlorine-based gas (e.g., CCl4, BCl3), with H2, O2, N2, or other gases mixed in as needed. Therefore, the residue 10 after dry etching contains one or more of the metal oxide, metal halide, and organometallic substance of the main constituent metal constituting the metal wiring layer 22 to be etched. If the main constituent metal is molybdenum, the residue 10 is likely to be one or more metal compounds such as MoOx, MoClx, MoFx, and MoCx (the x in the chemical formula of each compound is a number representing the composition ratio relative to molybdenum and does not mean that the listed compounds are equal). Here, the main constituent metal refers to the metal excluding trace amounts of additives, etc.

[0052] The present inventors conducted experiments to remove residues 10 from substrate 50 (in the state shown in FIG. 1D ) after dry etching using hydrofluoric acid, ammonium hydroxide, and TMAH (tetramethylammonium hydroxide aqueous solution). However, in experiments using any of the chemical solutions, removal of residues 10 from substrate 50 was insufficient. In addition, in the experiment using hydrofluoric acid, film reductions were observed in wiring 22W, hard mask 5, and underlying interlayer insulating film 12. Details of these experiments will be described later.

[0053] 3A, 3B, and 3C are schematic cross-sectional views for explaining a substrate processing method according to one embodiment of the present invention, and particularly show a residue removal process for a substrate 50 after dry etching for patterning a metal wiring layer 22.

[0054] 3A, residues 10 remain on the surface of the substrate 50 to be processed after dry etching, and in particular, residues 10 often occur in the openings 23 between adjacent wirings 22W. Residues 10 adhere to the sidewalls (i.e., sidewalls of the wirings 22W) and bottom (i.e., the surface of the interlayer insulating film 12) of the openings 23, and are typically present in large amounts near the bottom of the openings 23.

[0055] As shown in FIG. 3B, an ultraviolet irradiation process is performed on such a substrate 50 to be processed. Specifically, ultraviolet rays are irradiated from an ultraviolet irradiation unit onto the surface of the substrate 50 on which wiring is formed (hereinafter referred to as the "surface to be processed"). The ultraviolet irradiation unit may be an ultraviolet lamp unit 31. In this case, it is preferable that the ultraviolet lamp unit 31 is placed sufficiently close to the surface to be processed of the substrate 50 to reduce attenuation of the ultraviolet rays before they reach the residue 10. For example, the distance from the light irradiation surface of the ultraviolet lamp unit 31 to the surface to be processed of the substrate 50 may be about 2 mm. The ultraviolet irradiation unit may be an ultraviolet laser unit that scans the surface to be processed with an ultraviolet laser.

[0056] The ultraviolet light irradiated onto the processing surface of substrate 50 has energy equal to or greater than the bond energy of the metal compounds contained in residue 10, specifically, at least one compound selected from the group consisting of metal oxides, metal halides, and organometallic substances. In other words, the wavelength of the ultraviolet light is selected so as to have such energy. By irradiating such ultraviolet light, it is possible to break at least some of the chemical bonds of the metal compounds that make up residue 10, thereby modifying residue 10.

[0057] For example, if the main constituent metal of the metal wiring layer is molybdenum and the residue 10 is therefore a molybdenum oxide, molybdenum halide, or organic molybdenum-based substance, the ultraviolet light preferably has an energy of 465 kJ / mol or more (preferably 596 kJ / mol or more). The corresponding wavelength range is 257 nm or less (preferably 201 nm or less). For example, the bond energy of MoO3 is 596 kJ / mol, the bond energy of MoC is 481 kJ / mol, and the bond energy of MoF is 465 kJ / mol. Therefore, by irradiating the residue 10 with ultraviolet light having an energy of 465 kJ / mol or more, in other words, a wavelength of 257 nm or less, it is possible to break at least the chemical bonds of MoF, thereby modifying the residue 10. Furthermore, irradiation with ultraviolet light having an energy of 596 kJ / mol or more, in other words, a wavelength of 201 nm or less, can break the chemical bonds of molybdenum oxide, organic molybdenum substances, and molybdenum halides, thereby more effectively modifying the residue 10. The irradiation time of ultraviolet light may be, for example, 30 to 120 seconds.

[0058] Irradiation with ultraviolet light is a non-contact process that does not come into contact with the substrate 50, and can affect and modify the residue 10, while causing substantially no physical damage to other structures on the substrate 50 (such as the metal wiring layer 22, the interlayer insulating film 12, and the hard mask 5). Therefore, unlike plasma processing, etc., it acts selectively on the chemical bonds of the residue 10, and therefore has little effect on the characteristics of the final product (here, a semiconductor device) manufactured through the substrate processing.

[0059] In this embodiment, when irradiating the substrate 50 with ultraviolet light, an atmosphere control step is performed to control the atmosphere around the processing surface of the substrate 50 to a low-oxygen atmosphere. A low-oxygen atmosphere refers to an atmosphere with an oxygen concentration lower than the oxygen concentration in the atmosphere, and more specifically, an atmosphere with an oxygen concentration of 100,000 ppm or less is preferable. The atmosphere control step may be an inert gas supply step in which an inert gas (e.g., nitrogen gas) is supplied to the processing surface of the substrate 50. Specifically, an inert gas nozzle 32 that supplies an inert gas may be provided between the ultraviolet lamp unit 31 and the processing surface of the substrate 50. Alternatively, the ultraviolet light irradiation process may be performed in a sealed chamber 33, and an inert gas may be introduced into the sealed chamber 33 to create an inert gas atmosphere therein.

[0060] When ultraviolet light is irradiated in an atmosphere with a high oxygen concentration, oxygen ionizes to generate ozone, which may oxidize the surface of the metal layer that constitutes the wiring 22W. If metal oxides are generated on the surface of the wiring 22W, this can cause film reduction of the wiring 22W in subsequent wet processing, thereby increasing the risk of increasing the resistivity of the wiring 22W. Therefore, by performing ultraviolet light irradiation processing in a low-oxygen atmosphere, the generation of metal oxides on the surface of the wiring 22W can be suppressed, thereby reducing the risk of increasing the resistivity.

[0061] After modifying the residue 10 by ultraviolet irradiation, as shown in Fig. 3C, a residue removal step is performed to remove the residue 10 by wet processing in which a residue removal liquid is supplied to the substrate 50. The supply of the residue removal liquid to the substrate 50 may be performed by air-discharging the residue removal liquid from a nozzle toward the substrate 50 to be processed, or by an immersion process in which the substrate 50 is immersed in a processing tank in which the residue removal liquid is stored.

[0062] The residue removal solution is preferably an alkaline chemical solution (neutral or alkaline chemical solution, more preferably alkaline chemical solution) with a pH (hydrogen ion exponent) of 7 or more and 14 or less (more preferably 8 or more and 14 or less, and even more preferably 10 or more and 14 or less). If an acidic chemical solution is used, the residue 10 may not be sufficiently removed, and in addition, the wiring 22W, the hard mask 5, the interlayer insulating film 12, etc. may be thinned, which may affect the final device characteristics.

[0063] Furthermore, the residue removal liquid is preferably a treatment liquid that does not contain an oxidizing agent (ozone, hydrogen peroxide, etc.). A treatment liquid that contains an oxidizing agent may generate oxides on the surface of the wiring 22W, and the oxides may dissolve in the residue removal liquid and be etched, which may cause a film loss of the wiring 22W.

[0064] Therefore, a suitable treatment liquid as the residue removal liquid is an alkaline chemical liquid that does not contain an oxidizing agent. More specifically, the residue removal liquid preferably does not contain an oxidizing agent and contains one or more selected from ammonium hydroxide, TMAH (tetramethylammonium hydroxide aqueous solution), and a polymer removal liquid. The residue removal liquid may be supplied to the substrate 50 at a temperature of about room temperature to 80°C.

[0065] Ammonium hydroxide is an aqueous solution of ammonia, and it is preferable to use diluted ammonium hydroxide.

[0066] A polymer removal liquid is a chemical liquid used to remove photoresist residues that have undergone a plasma process, typically photoresist after being used as a mask for dry etching. Known polymer removal liquids include liquids containing organic alkaline liquids, liquids containing organic acids, liquids containing inorganic acids, and liquids containing ammonium fluoride-based substances. Of these, those with a pH of 7 to 14 (preferably 8 to 14, and even more preferably 10 to 14) can be used. Specifically, a liquid containing an organic alkaline liquid can be used as a residue removal liquid. Examples of liquids containing an organic alkaline liquid include liquids containing at least one of DMF (dimethylformamide), DMSO (dimethyl sulfoxide), hydroxylamine, and choline. Other examples of polymer removal liquids that can be used as residue removal liquids include liquids containing at least one of 1-methyl-2-pyrrolidone, tetrahydrothiophene 1.1-dioxide, isopropanolamine, monoethanolamine, 2-(2-aminoethoxy)ethanol, catechol, N-methylpyrrolidone, aromatic diol, perclene (tetrachloroethylene), and liquids containing phenol. More specifically, examples include at least one of a mixture of 1-methyl-2-pyrrolidone, tetrahydrothiophene 1.1-dioxide, and isopropanolamine, a mixture of dimethyl sulfoxide and monoethanolamine, a mixture of 2-(2-aminoethoxy)ethanol, hydroxylamine, and catechol, a mixture of 2-(2-aminoethoxy)ethanol and N-methylpyrrolidone, a mixture of monoethanolamine, water, and aromatic diol, and a mixture of perclene (tetrachloroethylene) and phenol. Other examples include liquids containing at least one of amines such as triethanolamine and pentamethyldiethylenetriamine, propylene glycol, and dipropylene glycol monomethyl ether.

[0067] After the residue 10 is removed by the residue removal liquid, a rinse process is performed in which a rinse liquid (deionized water, etc.) is supplied to the substrate 50 to wash away the chemical liquid, and then a drying process is performed to remove the liquid components from the substrate 50.

[0068] FIG. 4 shows a micrograph of a sample in a state (corresponding to FIG. 3A) in which the molybdenum layer (metal wiring layer 22) has been dry-etched (direct metal etching) through a hard mask 5 made of silicon nitride. Residues have formed between the wirings 22W. In this example, the pitch between adjacent wirings 22W is approximately 32 nm, and the height of the wirings 22W (thickness of the metal wiring layer 22) is approximately 64 nm. The cross section of the wiring 22W is trapezoidal, and the width of the wiring 22W is approximately 21 nm at the bottom edge and approximately 10 nm at the top edge of the trapezoidal cross section.

[0069] 5A, 5B, and 5C show a comparative example in which the residue removal process was carried out by supplying a processing liquid without irradiating the surface of the sample to be processed with ultraviolet light.

[0070] 5A is a micrograph taken after the sample in the state shown in FIG. 4 was immersed in a room-temperature hydrofluoric acid solution diluted with water to a concentration of 0.05 wt % for 2 minutes, then rinsed with water and dried. It can be seen that residue 10 remains between the wiring 22W and that the hard mask 5 has been thinned.

[0071] Figure 5B is a micrograph taken after the sample in the state shown in Figure 4 was immersed in ammonium hydroxide for 2 minutes, then rinsed with water and dried. The ammonium hydroxide used was diluted ammonium hydroxide, which was obtained by diluting commercially available ammonium hydroxide (concentration: approximately 28 wt%) with water by 100 times, at room temperature. Figure 5C is a micrograph taken after the sample in the state shown in Figure 4 was immersed in a TMAH aqueous solution for 2 minutes, then rinsed with water and dried. The TMAH aqueous solution used was diluted with water to a concentration of 0.29 wt% to 5 wt% at room temperature. In both Figures 5B and 5C, no film loss of the hard mask 5 is observed, but residue 10 remains between the wiring 22W, indicating incomplete residue removal.

[0072] 6A, 6B, and 6C show the results of a residue removal process in which a processing liquid was supplied after ultraviolet light was irradiated onto the surface of a sample to be processed, with FIG. 6A being a comparative example and FIGS. 6C and 6B being examples.

[0073] In all examples, the ultraviolet irradiation process was performed in a sealed chamber with an ultraviolet lamp unit positioned 2 mm from the surface of the sample to be treated. Additionally, an inert gas (specifically, nitrogen gas) was supplied into the sealed chamber to create an inert gas atmosphere (i.e., a low-oxygen atmosphere) between the ultraviolet lamp unit and the surface to be treated. The wavelength of the ultraviolet lamp was in the range of 172 nm to 184 nm. The ultraviolet irradiation time was 30 seconds. The temperature of the substrate 50 was room temperature.

[0074] Figure 6A (Comparative Example) is a micrograph taken after the sample in the state shown in Figure 4 was subjected to the above-mentioned UV irradiation treatment, then immersed in a room-temperature hydrofluoric acid solution diluted with water to a concentration of 0.05 wt%, for two minutes, and then rinsed and dried. It can be seen that residue 10 remains between the wiring 22W, and that the hard mask 5 has been thinned. In addition, it can be seen that the underlying interlayer insulating film 12 (silicon oxide film) has also been thinned.

[0075] FIG. 6B (Example) is a micrograph taken after the sample in the state shown in FIG. 4 was subjected to the above-described UV irradiation treatment, then immersed in ammonium hydroxide for 2 minutes, rinsed with water, and dried. The ammonium hydroxide used was diluted ammonium hydroxide, which was obtained by diluting commercially available ammonium hydroxide (concentration: approximately 28 wt%) with water by 100 times. FIG. 6C (Example) is a micrograph taken after the sample in the state shown in FIG. 4 was subjected to the above-described UV irradiation treatment, then immersed in a TMAH aqueous solution for 2 minutes, rinsed with water, and dried. The TMAH aqueous solution used was diluted with water to a concentration of 0.29 wt% to 5 wt% at room temperature. In both cases shown in FIGS. 6B and 6C, no film loss of the hard mask 5 was observed, and the residue 10 between the wirings 22W was sufficiently removed.

[0076] Figure 7 is a diagram illustrating another effect of UV irradiation, showing the effect of increased hydrophilicity due to UV irradiation. Specifically, it shows the results of investigating the contact angle of water (deionized water) on the surface of a molybdenum film. The left side shows the measurement result in the initial state, and the right side shows the measurement result after UV irradiation. The contact angle in the initial state is 10.8 degrees, meaning that the surface is hydrophilic even in the initial state. The contact angle after UV irradiation is 6 degrees, indicating that the contact angle has decreased due to UV irradiation, and hydrophilicity has increased.

[0077] The increased hydrophilicity allows the residue removal liquid, which is an aqueous solution, to become more compatible with the surface of the substrate 50 to be treated (particularly the surface of the wiring 22W), allowing the residue removal liquid to act effectively on the residue 10. In other words, even if the metal wiring layer 20 has a fine wiring pattern, good liquid penetration into the fine pattern can be achieved, and the residue 10 in the fine pattern can be efficiently removed.

[0078] Although the embodiment of the present invention has been described above, the present invention can be embodied in other forms.

[0079] For example, while the above-described embodiment primarily describes a case in which the metal layer is primarily composed of molybdenum, the principles of the present invention can also be applied to cases in which the metal layer is primarily composed of other metal materials. Specifically, the present invention can be applied to the processing of substrates having metal layers made of metal materials that can be patterned by direct metal etching (dry etching). For example, in a semi-damascene process, the conditions for selecting a metal wiring material are that it has an acceptable resistivity for a wiring film, can be deposited without a diffusion barrier, and can be patterned by dry etching (direct metal etching). Examples of metals that satisfy these conditions include molybdenum, ruthenium, and aluminum, as well as molybdenum-, ruthenium-, or aluminum-based metal compounds. The principles of the present invention can also be applied to the processing of substrates having metal layers made of these metal materials, thereby reducing the risk of leakage between wirings due to residues and the risk of increased resistivity due to reduction in the wiring film during residue removal processing.

[0080] Furthermore, although the above embodiment has been mainly described with reference to a semi-damascene process, the present invention can be applied not only to the semi-damascene process in which a via and a wiring film are simultaneously formed, but also to a process involving direct etching of a metal film. Specifically, the present invention may be applied to a residue removal process after direct etching (dry etching) of a wiring film in a wiring formation process in which a via and a wiring film are separately formed.

[0081] Furthermore, the substrate to be processed (underlying substrate) is not limited to a semiconductor substrate, but may be a substrate made of other materials such as a glass substrate or a ceramic substrate.

[0082] In addition, various design modifications can be made within the scope of the claims. [Explanation of symbols]

[0083] 1: Silicon substrate 2:Multilayer wiring layer 5: Hard mask 6: Amorphous carbon layer 7: Photoresist mask 10:Residue 11: Interlayer insulating film 12: Interlayer insulating film 12a: Via opening 20: Metal wiring layer 21: Metal wiring layer 22: Metal wiring layer 22W: Wiring 22a: Via metal part 23: Opening 31: Ultraviolet lamp unit 32: Inert gas nozzle 33: Sealed chamber 50: Circuit board

Claims

1. A substrate processing method for processing a substrate having a metal layer and a hard mask stacked on the metal layer on a surface thereof, comprising: patterning the metal layer exposed from the hard mask by dry etching; a step of irradiating with ultraviolet light a residue generated on the surface of the substrate by the dry etching, the residue including one or more of a metal oxide, a metal halide, and an organometallic substance containing an element of a main constituent metal of the metal layer; after the irradiation with ultraviolet light, removing the residue from the substrate by wet processing in which a residue removal solution having a pH (hydrogen ion exponent) of 7 or more and 14 or less is supplied to the surface of the substrate.

2. A substrate processing method for processing a substrate having a surface on which a hard mask and a metal layer patterned by dry etching through the hard mask are formed, and on which a residue resulting from the dry etching is generated on the surface, the residue including at least one of a metal oxide, a metal halide, and an organometallic substance containing an element of a main constituent metal of the metal layer, comprising: irradiating the residue with ultraviolet light; after the irradiation with ultraviolet light, removing the residue from the substrate by wet processing in which a residue removal solution having a pH (hydrogen ion exponent) of 7 or more and 14 or less is supplied to the surface of the substrate.

3. 3. The substrate processing method according to claim 1, wherein the metal layer contains, as the main constituent metal, at least one selected from a group of metal materials including molybdenum, ruthenium, aluminum, and metal compounds of these metals.

4. 3. The substrate processing method according to claim 1, further comprising an atmosphere control step of controlling the atmosphere around the substrate during the irradiation of the ultraviolet light to a low-oxygen atmosphere having an oxygen concentration lower than that of the air.

5. 5. The substrate processing method according to claim 4, wherein the atmosphere control step includes an inert gas supply step of supplying an inert gas to the surroundings of the substrate.

6. 3. The substrate processing method according to claim 1, wherein the ultraviolet rays have energy equal to or greater than the bond energy of at least one compound selected from the group consisting of metal oxides, metal halides, and organometallic substances contained in the residue.

7. The substrate processing method according to claim 1 , wherein the ultraviolet light increases the hydrophilicity of the surface of the metal layer.

8. the main constituent metal is molybdenum, 3. The substrate processing method according to claim 1, wherein the ultraviolet light has a wavelength of 257 nm or less.

9. 3. The substrate processing method according to claim 1, wherein the residue removal solution does not contain an oxidizing agent and contains at least one selected from the group consisting of ammonium hydroxide, TMAH (tetramethylammonium hydroxide aqueous solution), and a polymer removal solution.

10. 3. The substrate processing method according to claim 1, wherein the hard mask is made of an inorganic material.

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