Substrate processing method

Abstract

This substrate processing method processes a substrate having, on the surface thereof, a metal layer and a hard mask laminated on the metal layer. The method comprises the steps of: patterning the metal layer exposed from the hard mask by dry etching; irradiating the residue generated on the surface of the substrate by the dry etching with ultraviolet light; and removing the residue from the substrate by a wet process in which a residue removal liquid having a pH value (hydrogen ion index) of 7-14 is supplied to the surface of the substrate after the ultraviolet irradiation. The residue contains at least one of a metal oxide, a metal halide, and an organic metal-based material of an element that includes the main constituent metal of the metal layer.

Description

Technical Field

[0001] The present invention relates to a substrate processing method. The substrate to be processed includes a semiconductor wafer, a liquid crystal display device, an organic EL (Electroluminescence) display device, a FPD (Flat Panel Display) substrate, a ceramic substrate, a solar cell substrate, etc. The method of the present invention is particularly suitable for substrate processing for dry etching of a metal layer formed on the surface. Background Art

[0002] The process of forming a multilayer wiring layer on a semiconductor substrate after forming active components 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 a through hole formed in the interlayer insulating film. The through hole is formed by forming a through hole (through hole opening) in the interlayer insulating film and burying a metal (through hole metal) in the through hole. Different wiring layers are connected via through holes.

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

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-19006 Summary of the invention

[0007] [Problems to be solved by the invention]

[0008] In the structure of semiconductor devices that have been miniaturized in recent years, ruthenium and molybdenum have attracted attention as metal materials for constituting multilayer wiring layers. For example, as a multilayer wiring formation technology using ruthenium, a semi-metal damascene process has been proposed. The semi-metal damascene process refers to a technology in which a through-hole metal embedded in the through-hole opening is formed together with the wiring film of the upper layer after a through-hole opening is formed in an interlayer insulating film. After film formation, the wiring film is patterned into a wiring pattern by direct metal etching. The semi-metal damascene process can be applied by using a metal material that can be directly metal-etched.

[0009] Direct metal etching is a process of forming a hard mask on the wiring film and removing the unnecessary parts of the wiring film by dry etching through the hard mask. Since residues caused by dry etching will be generated on the surface of the dry-etched semiconductor substrate, a cleaning process (residue removal process) is required to remove the residues. For this cleaning process, it is required to reduce the damage to the hard mask and the wiring as much as possible and to remove the residue as efficiently as possible. Damage to the wiring, that is, film reduction, will lead to an increase in wiring resistance. In addition, the residues remaining between the wirings increase the risk of leakage between the wirings. Therefore, they will all affect the electrical properties of the final product.

[0010] Therefore, one embodiment of the present invention provides a substrate processing method for efficiently removing residues after dry etching of a metal layer while suppressing damage to the metal layer.

[0011] [Technical means to solve the problem]

[0012] One embodiment of the present invention provides a substrate processing method having the following features.

[0013] 1. A substrate processing method, comprising processing a substrate having a metal layer on its surface and a hard mask stacked on the metal layer, wherein the substrate processing method comprises the following steps:

[0014] performing dry etching to pattern the metal layer exposed from the hard mask;

[0015] irradiating ultraviolet rays to residues generated on the surface of the substrate by the dry etching and containing 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

[0016] After the ultraviolet irradiation, the residue is removed from the substrate by wet treatment, and the wet treatment is to supply a residue removal liquid having a pH value (hydrogen ion index) of greater than 7 and less than 14 (preferably greater than 8 and less than 14, and further preferably greater than 10 and less than 14) to the surface of the substrate.

[0017] 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 to which patterning by dry etching can be applied. The main constituent metal refers to a metal material other than trace additives that may be contained in the metal layer.

[0018] Dry etching is a plasma process that etches by attacking the exposed portion of the metal layer with active species of the process gas. After dry etching, a residue (dry etching residue) containing a compound (metal compound) of an element of the main constituent metal of the metal layer and a constituent element of the process gas remains on the substrate. Specifically, the compound constituting the residue includes at least one of a metal oxide, a metal halide, and an organometallic substance.

[0019] The residue as described above is irradiated with ultraviolet rays. The ultraviolet rays are pre-treatments that cut chemical bonds of compounds contained in the residue and modify the residue, thereby making it easier to remove the residue by subsequent wet treatment. After the pre-treatment, wet treatment is performed by supplying a residue removal liquid, thereby removing the residue outside the surface of the substrate. By using a treatment liquid having a pH value of 7 or more and 14 or less (preferably 8 or more and 14 or less, and more preferably 10 or more and 14 or less) as the residue removal liquid, the residue can be removed efficiently.

[0020] According to the experiment of the inventor, the acidic treatment liquid (acidic treatment liquid) cannot remove the residue efficiently, while the alkaline treatment liquid (neutral or alkaline treatment liquid, preferably alkaline treatment liquid) can remove the residue efficiently. In addition, since the acidic treatment liquid can corrode the oxide film on the substrate and cause damage to the structure on the substrate, from this point of view, it is also suitable to use the alkaline treatment liquid as the residue removal liquid.

[0021] The ultraviolet irradiation performed before supplying the residue removal liquid is a non-contact treatment, and although it will affect the residue, it will not substantially cause physical damage to other structures on the substrate (metal layer, insulating layer, etc.). Therefore, unlike plasma treatment, ultraviolet irradiation can selectively act on the chemical bonds of the residue, so it has little effect on the characteristics of the final product manufactured by substrate treatment.

[0022] 2. A substrate processing method for processing a substrate having a hard mask formed on the surface and a metal layer patterned by dry etching through the hard mask and having residue generated on the surface, wherein the residue is residue generated by the dry etching and contains one or more of a metal oxide, a metal halide, and an organic metal-based substance containing an element of a main constituent metal of the metal layer, and the substrate processing method comprises the following steps:

[0023] irradiating the residue with ultraviolet rays; and

[0024] After the ultraviolet irradiation, the residue is removed from the substrate by wet treatment, and the wet treatment is to supply a residue removal liquid having a pH value (hydrogen ion index) of greater than 7 and less than 14 (preferably greater than 8 and less than 14, and further preferably greater than 10 and less than 14) to the surface of the substrate.

[0025] The method of this embodiment is used to process a substrate after the metal layer is patterned by dry etching. The method of this embodiment also has the same function and effect as the above method.

[0026] 3. The substrate processing method according to item 1 or 2, wherein the metal layer contains at least one selected from the group of metal materials including molybdenum, ruthenium, and aluminum, and metal compounds of these metals as the main constituent metal.

[0027] For example, the substrate processing method of this embodiment can be applied to a wiring formation process of forming a wiring layer (typically a multi-layer wiring layer) on a substrate. Specifically, by forming a metal layer using a wiring metal material, forming a hard mask corresponding to the wiring pattern on the metal layer, and performing dry etching, the metal layer can be patterned into a wiring pattern.

[0028] For example, the material constituting the fine wiring of a semiconductor device is selected in consideration of resistivity or diffusivity into other material layers. In the semi-metal damascene technology, which is one of the wiring formation technologies applied when forming multilayer wiring on a semiconductor substrate, the conditions for selecting the wiring metal material are that the wiring film has a tolerable resistivity, can be deposited without a diffusion barrier, and can be patterned by dry etching (direct metal etching). As metals that meet such conditions, in addition to molybdenum, ruthenium, and aluminum, molybdenum-based, ruthenium-based, or aluminum-based metal compounds can also be exemplified.

[0029] By applying the substrate processing method of this embodiment, the risk of leakage between wirings due to residues can be reduced, and the risk of increase in specific resistance due to reduction in wiring film during residue removal processing can be reduced.

[0030] 4. The substrate processing method according to any one of items 1 to 3 further comprises an environment control process, wherein the environment around the substrate during the ultraviolet irradiation process is controlled to be a low oxygen environment in which the oxygen concentration is lower than the oxygen concentration in the atmosphere.

[0031] If ultraviolet rays are irradiated in an environment with a high oxygen concentration, ozone will be generated, and there is a concern that the metal layer will be oxidized by the ozone. When metal oxides are formed on the surface of the metal layer and the metal oxides are etched by the residue removing solution, the film of the metal layer will be reduced. Therefore, by irradiating ultraviolet rays in a low-oxygen environment, the risk of film reduction of the metal layer can be reduced.

[0032] 5. The substrate processing method according to item 4, wherein the environment control process includes an inert gas supply process, and the inert gas supply process is to supply an inert gas to the periphery of the substrate.

[0033] 6. The substrate processing method according to any one of items 1 to 5, wherein the ultraviolet rays have an energy greater than or equal to the bonding energy of at least one compound of the metal oxide, metal halide, and organometallic substance contained in the residue.

[0034] According to this method, the chemical bonds of at least one compound of metal oxides, metal halides, and organometallic substances in the residue can be cut by ultraviolet irradiation to modify the residue. Thus, the residue can be efficiently removed by the residue removing liquid.

[0035] The residue remaining on the surface of the substrate after dry etching typically includes a metal compound formed by bonding the main constituent metal of the metal layer to be etched and the constituent elements of the process gas used for dry etching. The ultraviolet light has a wavelength that can be absorbed by the residue and has an energy greater than the bonding energy of the main constituent metal and the constituent elements of the process gas, thereby modifying the residue into a substance that is easily removed by the residue removing solution.

[0036] For example, when the main constituent metal is molybdenum and the residue contains a compound formed by bonding molybdenum 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). Since the molybdenum compound can absorb the energy of ultraviolet light, at least a portion of the bonds of the molybdenum compound can be cut by ultraviolet light irradiation, so the residue can be modified.

[0037] 7. The substrate processing method according to any one of items 1 to 6, wherein the ultraviolet rays increase the hydrophilicity of the surface of the metal layer.

[0038] This method increases the hydrophilicity of the surface of the metal layer, so that the residue removing liquid can easily penetrate into it. Therefore, even if the metal layer is patterned into a fine structure, the residue removing liquid can penetrate into the fine structure to efficiently remove the residue.

[0039] 8. The substrate processing method according to any one of items 1 to 7, wherein the main constituent metal is molybdenum,

[0040] The wavelength of the ultraviolet rays is 257 nm or less (more preferably 201 nm or less).

[0041] By irradiating ultraviolet rays in a wavelength range below 257 nm, the energy required to cut the bond of the compound formed by molybdenum and at least one element of carbon, chlorine, oxygen, and fluorine can be provided, and the residue can be effectively modified. More preferably, by irradiating ultraviolet rays in a wavelength range below 201 nm, the chemical bonds of the molybdenum compound formed by molybdenum and carbon, chlorine, oxygen, and fluorine can be roughly cut, so the residue can be further effectively modified.

[0042] 9. The substrate processing method according to any one of items 1 to 8, wherein the residue removing liquid does not contain an oxidizing agent, and comprises one or more selected from ammonium hydroxide, TMAH (tetramethylammonium hydroxide aqueous solution), and a polymer removing liquid.

[0043] The polymer removal liquid refers to a liquid used to remove the residue of the photoresist that has been processed by a plasma process. As the polymer removal liquid, there are known liquids containing organic alkali liquids, liquids containing organic acids, liquids containing inorganic acids, liquids containing ammonium fluoride-based substances, etc. Among these liquids, a liquid having a pH value of 7 or more and 14 or less (preferably 8 or more and 14 or less, and further preferably 10 or more and 14 or less) can be used. Specifically, a liquid containing an organic alkali liquid can be used as a residue removal liquid. As the liquid containing an organic alkali liquid, there can be cited a liquid containing at least any one of DMF (dimethylformamide), DMSO (dimethyl sulfoxide), hydroxylamine, and choline. In addition, as a polymer removing liquid that can be used as a residue removing liquid, there is a liquid containing at least any one of 1-methyl-2-pyrrolidone, tetrahydrothiophene 1.1-dioxide, isopropanolamine, monoethanolamine, 2-(2-aminoethoxy)ethanol, catechol, N-methylpyrrolidone, aromatic diols, perchloroethene (tetrachloroethylene), phenol, etc. More specifically, examples include: a mixed liquid of 1-methyl-2-pyrrolidone, tetrahydrothiophene 1.1-dioxide, and isopropanolamine; a mixed liquid of dimethyl sulfoxide and monoethanolamine; a mixed liquid of 2-(2-aminoethoxy)ethanol, hydroxylamine, and catechol; a mixed liquid of 2-(2-aminoethoxy)ethanol and N-methylpyrrolidone; a mixed liquid of monoethanolamine, water, and aromatic diols; a mixed liquid of perchloroethylene (tetrachloroethylene) and phenol, etc. In addition, a liquid containing at least any one of amines such as triethanolamine and pentamethyldiethylenetriamine, propylene glycol, and dipropylene glycol monomethyl ether may be mentioned.

[0044] 10. The substrate processing method according to any one of items 1 to 9, wherein the hard mask contains an inorganic substance.

[0045] For example, the hard mask may include a silicon nitride film. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] 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.

[0047] Figure 2 It is a cross-sectional view showing the structure of the cross section along the line II-II in FIG. 1A .

[0048] 3A, 3B, and 3C are schematic cross-sectional views for explaining a substrate processing method according to an embodiment of the present invention.

[0049] Figure 4 This is a microscope photograph of a sample in a state where the molybdenum layer is dry-etched through a hard mask.

[0050] 5A , 5B and 5C are microscope photographs showing a state where a residue removal process is performed by supplying a process liquid without irradiating the process target surface of a sample with ultraviolet rays.

[0051] 6A , 6B and 6C are microscope photographs showing a state in which a treatment liquid is supplied to perform a residue removal treatment after ultraviolet irradiation is performed on the treatment target surface of the sample.

[0052] Figure 7 This is a diagram for explaining another effect of ultraviolet irradiation, and shows the effect of increasing hydrophilicity due to ultraviolet irradiation. DETAILED DESCRIPTION

[0053] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0054] 1A to 1D are schematic cross-sectional views sequentially showing a portion 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. Figure 2 1A is a cross-sectional view showing the structure of the cross section along the line II-II of FIG. Here, a part of the 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. In addition, here, an example of forming a metal wiring layer constituting the multilayer wiring layer 2 by a semi-metal damascene process is described. In the following description, the term "substrate 50" refers to the overall structure including the silicon substrate 1 and various films (insulating film, metal film, anti-etching film, etc.) formed on the surface thereof.

[0055] First, referring to FIG. 1A and Figure 2 Elements such as transistors (active elements and / or passive elements) are formed on the surface layer of the silicon substrate 1, and a multilayer wiring layer 2 is formed on the main surface on the side where the elements are formed.

[0056] The multilayer wiring layer 2 includes interlayer insulating films 11, 12, and a plurality of metal wiring layers 21, 22. The interlayer insulating films 11, 12 typically include silicon oxide. A metal wiring layer 21 (lower metal wiring layer) is formed above the interlayer insulating film 11. The metal wiring layer 21 may include, for example, copper, ruthenium, molybdenum, etc. Although detailed illustrations are omitted, 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 the interlayer insulating film 12. In this embodiment, the metal wiring layer 22 is formed by a semi-metallic damascene process.

[0057] Specifically, a through hole opening 12a is formed in the interlayer insulating film 12, which penetrates the interlayer insulating film 12 in the film thickness direction and exposes the lower metal wiring layer 21. An upper metal wiring layer 22 is formed on the interlayer insulating film 12. At the stage of FIG. 1A, the metal wiring layer 22 covers the entire surface of the interlayer insulating film 12 and has a through hole metal portion 22a buried in the through hole opening 12a (see FIG. 1A ). Figure 2 Here, as an example, the main constituent metal of the metal wiring layer 22 is molybdenum. For example, the metal wiring layer 22 of molybdenum can be formed by a plasma CVD (chemical vapor deposition) method.

[0058] A hard mask 5 (film before patterning) is stacked on the metal wiring layer 22 to cover the entire surface thereof. The hard mask 5 typically includes an inorganic insulating material, for example, silicon nitride as an example of an inorganic insulating material. An amorphous carbon layer 6 (state before patterning) is formed on the hard mask 5 to cover the entire surface thereof. A photoresist mask 7 for patterning the metal wiring layer 22 into a desired wiring pattern is formed on the surface of the amorphous carbon layer 6. The photoresist mask 7 is subjected to an exposure process and a development process to become a patterned state. The photoresist mask 7 and the amorphous carbon layer 6 constitute a multilayer resist for patterning the hard mask 5.

[0059] Next, as shown in FIG1B , the amorphous carbon layer 6 is etched by dry etching using the photoresist mask 7 as a mask. Thus, 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 from the opening (through hole) 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. Thus, the pattern of the amorphous carbon layer 6 is transferred to the hard mask 5, and the metal wiring layer 22 is selectively exposed from the opening (through hole) formed in the hard mask 5. After the etching, a cleaning process is performed to remove the residue of the photoresist mask 7 after the dry etching. This state is shown in FIG1B .

[0060] Next, as shown in FIG. 1C , etching (for example, wet etching) is performed to remove the amorphous carbon layer 6 , and further, the surface of the substrate 50 is cleaned.

[0061] Then, as shown in FIG. 1D , the metal wiring layer 22 is etched by dry etching using the hard mask 5 as a mask. Thus, the pattern of the hard mask 5 is transferred to the metal wiring layer 22. Thus, the metal wiring layer 22 is patterned into a desired wiring pattern. This process is so-called direct metal etching, and here, a wiring pattern containing molybdenum is formed on the interlayer insulating film 12 by direct metal etching of the metal wiring layer 22 containing molybdenum.

[0062] The wiring pattern may include, for example, a plurality of linear wirings 22W extending in a direction intersecting the paper surface of 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 buried therein. At least one wiring 22W has a through-hole metal portion 22a (see FIG. 1B ) buried in a through-hole opening 12a formed in the interlayer insulating film 12. Figure 2 ) and is three-dimensionally connected to the underlying metal wiring layer 21 via the through-hole metal portion 22a.

[0063] In this example, the semi-damascene process includes forming a via opening 12 a in the interlayer insulating film 12 , embedding the via opening 12 a , forming a metal wiring layer 22 covering the interlayer insulating film 12 , and patterning the metal wiring layer 22 by direct metal etching.

[0064] The direct metal etching of the metal wiring layer 22 through the hard mask 5 is performed by dry etching, more specifically, by reactive ion etching. This dry etching is accompanied by a plasma process in which a process gas for etching is introduced into a processing chamber, and the process gas is irradiated with electromagnetic waves such as microwaves to plasmatize it. Thus, active species of the process gas are generated, and by introducing the active species of the process gas into the metal wiring layer 22, anisotropic etching can be performed to etch the metal wiring layer 22 in its thickness direction.

[0065] The compound (metal compound) of the metal material constituting the metal wiring layer 22 and the constituent elements of the processing gas remains as residue 10 (see FIG. 3A ) on the surface of the dry-etched substrate 50. In particular, the residue 10 remaining between the wirings 22W, specifically, the residue remaining on the side wall or bottom of the opening 23 between the wirings 22W, may cause leakage between the wirings, and therefore, a residue removal process is required.

[0066] The conditions required for the residue removal process are that the residue 10 can be removed and the influence on other structures on the substrate 50 is small. In particular, the process of etching the wiring 22W is not preferred because there is a risk of film reduction of the wiring 22W and an increase in the specific resistance of the wiring 22W. In addition, the process of etching the hard mask 5 increases the exposed part of the wiring 22W, which may result in a film reduction of the wiring 22W, which is still not preferred. Furthermore, the process of etching the interlayer insulating film 12 as the base of the metal wiring layer 22 is not preferred because it increases the risk of leakage between the upper and lower metal wiring layers 21 and 22, or affects the capacitance between these wiring layers.

[0067] Typically, fluorine-based gas (CF 4 , CHF 3 , SF 6 etc.) or chlorine-based gases (CCl 4 , BCl 3 If necessary, H 2 , O 2 、N 2 Therefore, the residue 10 after dry etching contains one or more of the metal oxide, metal halide, and organometallic substance constituting the main constituent metal of the metal wiring layer 22 to be etched. In the case where the main constituent metal is molybdenum, it is highly likely that one or more of the metal compounds such as MoOx, MoClx, MoFx, and MoCx (x in the chemical formula of each compound is a number indicating the composition ratio relative to molybdenum, and does not mean that the different compounds listed are equal) constitute the residue 10. Here, the main constituent metal refers to the metal other than trace additives.

[0068] The present inventors conducted experiments using hydrofluoric acid, ammonium hydroxide, and TMAH (tetramethylammonium hydroxide aqueous solution) to remove the residue 10 from the substrate 50 (the state of FIG. 1D ) after dry etching. However, the experiments using any of the chemical solutions resulted in insufficient removal of the residue 10 on the substrate 50. In addition, in the experiments using hydrofluoric acid, film reduction of the wiring 22W, the hard mask 5, and the underlying interlayer insulating film 12 was also observed. The details of these experiments will be described later.

[0069] 3A , 3B and 3C are schematic cross-sectional views for explaining a substrate processing method according to an embodiment of the present invention, and particularly illustrate a residue removal process of a substrate 50 after dry etching to pattern the metal wiring layer 22 .

[0070] 3A , the residue 10 after dry etching remains on the surface of the substrate 50 to be processed, and in particular, in many cases, the residue 10 is generated in the opening 23 between adjacent wirings 22W. The residue 10 adheres to the side walls (that is, the side walls of the wiring 22W) and the bottom (that is, the surface of the interlayer insulating film 12) of the opening 23, and typically exists in large quantities near the bottom of the opening 23.

[0071] As shown in FIG3B , the substrate 50 to be processed is subjected to ultraviolet irradiation treatment. Specifically, the surface of the substrate 50 on which the wiring is formed (hereinafter referred to as the "processing target surface") is irradiated with ultraviolet rays from an ultraviolet irradiation unit. The ultraviolet irradiation unit may be an ultraviolet lamp unit 31. In this case, the ultraviolet lamp unit 31 is preferably close enough to the processing target surface of the substrate 50 to reduce the attenuation of ultraviolet rays before reaching the residue 10. For example, the distance from the light irradiation surface of the ultraviolet lamp unit 31 to the processing target surface of the substrate 50 may be set to about 2 mm. The ultraviolet irradiation unit may also be an ultraviolet laser unit that scans the processing target surface with an ultraviolet laser.

[0072] The ultraviolet rays irradiated on the processing target surface of the substrate 50 have an energy greater than the bonding energy of at least one compound of the metal compound, specifically, metal oxide, metal halide, and organometallic substance contained in the residue 10. In other words, the wavelength of the ultraviolet rays is selected so as to have such energy. By irradiating with such ultraviolet rays, the chemical bonds of at least a part of the metal compound constituting the residue 10 can be cut, so that the residue 10 can be modified.

[0073] For example, the main constituent metal of the metal wiring layer is molybdenum. Therefore, when the residue 10 is 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, MoO 3 The bonding energy of Mo is 596 kJ / mol, the bonding energy of MoC is 481 kJ / mol, and the bonding energy of MoF is 465 kJ / mol. Therefore, by irradiating the residue 10 with an energy of 465 kJ / mol or more, in other words, ultraviolet rays with a wavelength of 257 nm or less, at least the chemical bond of MoF can be cut, thereby modifying the residue 10. In addition, by irradiating with an energy of 596 kJ / mol or more, in other words, ultraviolet rays with a wavelength of 201 nm or less, the chemical bonds of molybdenum oxide, organic molybdenum-based substances, and molybdenum halides can be cut, so the residue 10 can be modified more effectively. The irradiation time of ultraviolet rays can be, for example, 30 seconds to 120 seconds.

[0074] Ultraviolet irradiation is a non-contact treatment that does not come into contact with the substrate 50. Although it can affect the residue 10 and modify it, it does not substantially cause physical damage to other structures (metal wiring layer 22, interlayer insulating film 12, hard mask 5, etc.) on the substrate 50. Therefore, unlike plasma treatment, ultraviolet irradiation selectively acts on the chemical bonds of the residue 10, and therefore has little effect on the characteristics of the final product (here, semiconductor device) manufactured by substrate treatment.

[0075] In this embodiment, when the substrate 50 is irradiated with ultraviolet rays, an environmental control process is performed to control the environment around the processing target surface of the substrate 50 to a low oxygen environment. A low oxygen environment refers to an environment in which the oxygen concentration is lower than the oxygen concentration in the atmosphere, and more specifically, it is preferably an environment in which the oxygen concentration is set to 100,000 PPM or less. The environmental control process can also be an inert gas supply process for supplying an inert gas (such as nitrogen) to the processing target surface of the substrate 50. Specifically, an inert gas nozzle 32 can be provided to supply an inert gas between the ultraviolet lamp unit 31 and the processing target surface of the substrate 50. In addition, ultraviolet irradiation treatment can also be performed in a closed chamber 33, and an inert gas is introduced into the closed chamber 33 to make the closed chamber 33 an inert environment.

[0076] If ultraviolet rays are irradiated in an environment with a high oxygen concentration, oxygen will be liberated to generate ozone, and there is a concern that the ozone will cause oxidation of the surface of the metal layer constituting the wiring 22W. Therefore, if metal oxides are generated on the surface of the wiring 22W, the film of the wiring 22W will be reduced in the subsequent wet treatment, and the risk of increasing the specific resistance of the wiring 22W will increase. Therefore, by performing ultraviolet irradiation treatment in a low-oxygen environment, the generation of metal oxides on the surface of the wiring 22W can be suppressed, thereby reducing the risk of increasing the specific resistance.

[0077] After the residue 10 is modified by ultraviolet irradiation, as shown in FIG3C, a residue removal step is performed to remove the residue 10 by wet processing by supplying a residue removing liquid to the substrate 50. The supply of the residue removing liquid to the substrate 50 may be performed by spraying the residue removing liquid from a nozzle into the air toward the substrate 50 to be processed, or by immersion processing by immersing the substrate 50 in a processing layer storing the residue removing liquid.

[0078] The residue removing liquid is preferably an alkaline liquid (neutral or alkaline liquid, more preferably alkaline liquid) having a pH value (hydrogen ion index) of 7 to 14 (more preferably 8 to 14, and further preferably 10 to 14). An acidic liquid may not sufficiently remove the residue 10, and may also reduce the film thickness of the wiring 22W, the hard mask 5, the interlayer insulating film 12, etc., thereby affecting the final device characteristics.

[0079] The residue removing liquid is preferably a treatment liquid that does not contain an oxidant (ozone, hydrogen peroxide solution, etc.). A treatment liquid containing an oxidant may generate oxides on the surface of the wiring 22W, which may dissolve in the residue removing liquid and be etched, thereby possibly causing a reduction in the film of the wiring 22W.

[0080] Therefore, a treatment liquid suitable for the residue removal liquid is an alkaline liquid containing no oxidant. More specifically, the residue removal liquid preferably contains no oxidant and contains one or more selected from ammonium hydroxide, TMAH (tetramethylammonium hydroxide aqueous solution), and polymer removal liquid. The residue removal liquid can be supplied to the substrate 50 at a temperature of about room temperature to about 80°C.

[0081] Ammonium hydroxide is an aqueous solution of ammonia, and preferably, diluted ammonium hydroxide is used.

[0082] The polymer removing liquid refers to a liquid used to remove the residue of the photoresist after the plasma process, typically the photoresist after being used as a mask for dry etching. As the polymer removing liquid, there are known liquids containing organic alkali liquids, liquids containing organic acids, liquids containing inorganic acids, liquids containing ammonium fluoride-based substances, etc. Among these liquids, a liquid having a pH value of 7 or more and 14 or less (preferably 8 or more and 14 or less, and more preferably 10 or more and 14 or less) can be used. Specifically, a liquid containing an organic alkali liquid can be used as a residue removing liquid. As the liquid containing an organic alkali liquid, a liquid containing at least any one of DMF (dimethylformamide), DMSO (dimethyl sulfoxide), hydroxylamine, and choline can be cited. In addition, as a polymer removal liquid that can be used as a residue removal liquid, there is a liquid containing at least any one of 1-methyl-2-pyrrolidone, tetrahydrothiophene 1.1-dioxide, isopropanolamine, monoethanolamine, 2-(2-aminoethoxy)ethanol, catechol, N-methylpyrrolidone, aromatic diols, perchloroethylene (tetrachloroethylene), phenol, etc. More specifically, examples include: a mixed liquid of 1-methyl-2-pyrrolidone, tetrahydrothiophene 1.1-dioxide, and isopropanolamine; a mixed liquid of dimethyl sulfoxide and monoethanolamine; a mixed liquid of 2-(2-aminoethoxy)ethanol, hydroxylamine, and catechol; a mixed liquid of 2-(2-aminoethoxy)ethanol and N-methylpyrrolidone; a mixed liquid of monoethanolamine, water, and aromatic diols; a mixed liquid of perchloroethylene (tetrachloroethylene) and phenol, etc. In addition, a liquid containing at least any one of amines such as triethanolamine and pentamethyldiethylenetriamine, propylene glycol, and dipropylene glycol monomethyl ether may be mentioned.

[0083] After the residue 10 is removed by the residue removing liquid, a cleaning process is performed by supplying a cleaning liquid (deionized water or the like) to the substrate 50 to rinse off the chemical solution, and then a drying process is performed to remove the liquid component from the substrate 50.

[0084] exist Figure 4 A microscope photograph of a sample showing a state (corresponding to FIG. 3A ) in which a molybdenum layer (metal wiring layer 22) is dry-etched (direct metal etching) via a hard mask 5 containing silicon nitride. Residues are generated between wirings 22W. In this example, the spacing between adjacent wirings 22W is about 32 nm, and the height of wiring 22W (thickness of metal wiring layer 22) is about 64 nm. The cross section of wiring 22W is a trapezoid, and the lower side of the trapezoidal cross section is about 21 nm and the upper side is about 10 nm with respect to the width of wiring 22W.

[0085] 5A , 5B and 5C show a comparative example in which a residue removal process is performed by supplying a process liquid without irradiating the process target surface of a sample with ultraviolet rays.

[0086] FIG5A is a diagram of Figure 4 The sample in the state of 22W was immersed in a hydrofluoric acid aqueous solution diluted with water to a concentration of 0.05 wt % at room temperature for 2 minutes, and then washed with water and dried. It can be seen that the residue 10 remains between the wirings 22W and the film reduction of the hard mask 5 occurs.

[0087] FIG5B is Figure 4 The sample was immersed in ammonium hydroxide for 2 minutes, then washed with water and dried. As ammonium hydroxide, commercially available ammonium hydroxide (concentration of about 28 wt%) was diluted with water 100 times at room temperature. Figure 4 The sample in the state of being immersed in the TMAH aqueous solution for 2 minutes, then washed with water and dried, and the microscope photograph was taken. As the TMAH aqueous solution, a solution obtained by diluting it with water to a concentration of 0.29wt% to 5wt% at room temperature. In all the cases shown in Figures 5B and 5C, no reduction in the film of the hard mask 5 was found, but residues 10 remained between the wirings 22W, and the residue removal was incomplete.

[0088] 6A, 6B and 6C show the results of a residue removal treatment in which a treatment liquid is supplied after ultraviolet irradiation is performed on the treatment target surface of a sample. FIG. 6A is a comparative example, and FIG. 6C and FIG. 6B are examples.

[0089] In all cases, the ultraviolet irradiation treatment was carried out in a closed chamber, with the ultraviolet lamp unit arranged at a position close to the processing target surface of the sample by 2 mm. In addition, an inert gas (specifically nitrogen) was supplied into the closed chamber, so that an inert gas environment (i.e., a low oxygen environment) was formed between the ultraviolet lamp unit and the processing target surface. The emission wavelength of the ultraviolet lamp was in the range of 172 nm to 184 nm. The ultraviolet irradiation time was set to 30 seconds. In addition, the temperature of the substrate 50 was set to room temperature.

[0090] FIG. 6A (comparative example) is Figure 4 The sample in the state of was subjected to the above-mentioned ultraviolet irradiation treatment, and then immersed in a hydrofluoric acid aqueous solution at room temperature diluted with water to a concentration of 0.05wt% for 2 minutes, and then washed with water and dried. It can be seen that the residue 10 remains between the wirings 22W, and the film reduction of the hard mask 5 occurs. In addition, it can be seen that the interlayer insulating film 12 (silicon oxide film) of the base also undergoes film reduction.

[0091] FIG. 6B (embodiment) is a Figure 4 The sample was subjected to the ultraviolet irradiation treatment, and then immersed in ammonium hydroxide for 2 minutes, and then washed and dried. As ammonium hydroxide, commercially available ammonium hydroxide (concentration of about 28wt%) was diluted with water 100 times at room temperature. In addition, FIG. 6C (Example) is a microscope photograph of Figure 4 The sample in the state was subjected to the ultraviolet irradiation treatment, and then immersed in the TMAH aqueous solution for 2 minutes, and then washed and dried. The microscope photograph was taken. As the TMAH aqueous solution, a solution was obtained by diluting it with water to a concentration of 0.29wt% to 5wt% at room temperature. In all cases shown in Figures 6B and 6C, no reduction in the film of the hard mask 5 was found, and the residue 10 between the wiring 22W was fully removed.

[0092] Figure 7 It is a diagram used to illustrate another effect produced by ultraviolet irradiation, which shows the effect of increasing hydrophilicity produced by ultraviolet irradiation. Specifically, it shows the results of studying the contact angle of water (deionized water) relative to the surface of the molybdenum film. The left side shows the measurement results in the initial state (Initial), and the right side shows the measurement results after ultraviolet irradiation (After UV). The contact angle in the initial state is 10.8 degrees, and the surface is also hydrophilic in the initial state. In addition, it can be seen that the contact angle after ultraviolet irradiation is 6 degrees. Through ultraviolet irradiation, the contact angle decreases and the hydrophilicity increases.

[0093] Due to the increased hydrophilicity, the residue removing liquid as an aqueous solution becomes easy to have affinity with the processing target surface of the substrate 50 (especially the surface of the wiring 22W), so that the residue removing liquid can effectively act on the residue 10. In other words, even if the metal wiring layer 20 has a fine wiring pattern, good liquid infiltration into the fine pattern can be achieved, so that the residue 10 in the fine pattern can be efficiently removed.

[0094] As mentioned above, although embodiment of this invention is described, this invention can be implemented in other forms.

[0095] For example, in the above-described embodiment, the case where the main constituent metal of the metal layer is molybdenum is mainly described, but the principle of the present invention can also be applied to the case where other metal materials are the main constituent metals of the metal layer. Specifically, the present invention can be applied to the processing of a substrate having a metal layer containing a metal material that can be patterned by direct metal etching (dry etching). For example, in a semi-metal damascene process, having a resistivity that is allowable as a wiring film, being deposited without a diffusion barrier, and being patterned by dry etching (direct metal etching) become conditions for selecting a wiring metal material. As metals that meet such conditions, in addition to molybdenum, ruthenium, and aluminum, molybdenum-based, ruthenium-based, or aluminum-based metal compounds can also be exemplified. The principle of the present invention can also be applied to the processing of a substrate having a metal layer containing these metal materials, thereby reducing the risk of leakage between wirings caused by residues, and reducing the risk of increased specific resistance caused by the reduction of wiring films during residue removal processing.

[0096] In addition, in the above-mentioned embodiment, the semi-metal damascene process is mainly described, but the present invention can be applied not only to the semi-metal damascene process of forming a through hole and a wiring film at the same time, but also to the process accompanied by direct etching of a metal film. Specifically, in the wiring forming process of forming a through hole and a wiring film separately, the present invention can also be applied to the residue removal process after direct etching (dry etching) of the wiring film.

[0097] In addition, the substrate to be processed (base substrate) is not limited to a semiconductor substrate, and may be a substrate of other materials such as a glass substrate and a ceramic substrate.

[0098] Furthermore, various design changes can be made within the scope of the matters described in the claims.

[0099] [Explanation of symbols]

[0100] 1: Silicon substrate

[0101] 2: Multi-layer wiring layer

[0102] 5: Hard mask

[0103] 6: Amorphous carbon layer

[0104] 7: Photoresist mask

[0105] 10: Residue

[0106] 11: Interlayer insulation film

[0107] 12: Interlayer insulation film

[0108] 12a: Through hole opening

[0109] 20: Metal wiring layer

[0110] 21: Metal wiring layer

[0111] 22: Metal wiring layer

[0112] 22W: Wiring

[0113] 22a: Through-hole metal part

[0114] 23: Opening

[0115] 31: UV lamp unit

[0116] 32: Inert gas nozzle

[0117] 33: Sealed chamber

[0118] 50: substrate.

Claims

1. A substrate processing method, comprising processing a substrate having a metal layer on its surface and a hard mask stacked on the metal layer, wherein the substrate processing method comprises the following steps: performing dry etching to pattern the metal layer exposed from the hard mask; irradiating ultraviolet rays to residues generated on the surface of the substrate by the dry etching and containing 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 After the ultraviolet irradiation, the residue is removed from the substrate by wet processing in which a residue removing liquid having a pH value (hydrogen ion index) 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 hard mask formed on the surface and a metal layer patterned by dry etching through the hard mask and having residue generated on the surface, wherein the residue is residue generated by the dry etching and contains one or more of a metal oxide, a metal halide, and an organic metal-based substance containing an element of a main constituent metal of the metal layer, and the substrate processing method comprises the following steps: irradiating the residue with ultraviolet rays; and After the ultraviolet irradiation, the residue is removed from the substrate by wet processing in which a residue removing liquid having a pH value (hydrogen ion index) of 7 or more and 14 or less is supplied to the surface of the substrate.

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

4. The substrate processing method according to claim 1 or 2, further comprising an environment control process, wherein the environment around the substrate during the ultraviolet irradiation process is controlled to be a low-oxygen environment in which the oxygen concentration is lower than the oxygen concentration in the atmosphere. 5 . The substrate processing method according to claim 4 , wherein the environment control step includes an inert gas supplying step of supplying an inert gas to the periphery of the substrate.

6. The substrate processing method according to claim 1 or 2, wherein the ultraviolet rays have energy greater than or equal to the bonding energy of at least one compound of the metal oxide, metal halide, and organometallic substance contained in the residue. 7 . The substrate processing method according to claim 1 , wherein the ultraviolet rays increase the hydrophilicity of the surface of the metal layer.

8. The substrate processing method according to claim 1 or 2, wherein the main constituent metal is molybdenum, The wavelength of the ultraviolet rays is 257 nm or less.

9. The substrate processing method according to claim 1 or 2, wherein the residue removing liquid does not contain an oxidizing agent, and comprises at least one selected from ammonium hydroxide, TMAH (tetramethylammonium hydroxide aqueous solution), and a polymer removing liquid.

10. The substrate processing method according to claim 1 or 2, wherein the hard mask comprises an inorganic substance.

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