Plasma processing method

Abstract

A plasma processing method for etching a metal film using plasma according to one embodiment of the present disclosure comprises: a first step for etching the metal film by plasma generated using a gas containing an oxygen element and a gas containing a halogen element; a second step for nitriding the etched metal film by plasma after the first step; and a third step for etching the nitrided metal film by plasma generated using a gas containing a halogen element after the second step. The second step and the third step are repeated until the depth of the etched metal film reaches a predetermined depth.

Description

Plasma treatment method

[0001] This disclosure relates to a plasma processing method.

[0002] With the miniaturization and three-dimensionalization of functional element products such as semiconductor devices, three-dimensional processing technology for various materials has become crucial in the dry etching process of semiconductor manufacturing, and technology is required to process complex shapes by controlling the shape at the atomic layer level. Miniaturization is also progressing in the wiring process, and with conventionally used Cu (copper) wiring, the reduction in wiring width will lead to an increase in wiring resistance in the future. This is because a barrier metal layer is formed between the interlayer film material and the Cu wiring to prevent electromigration, in which metal atoms in the wiring move due to electric current and lead to disconnection. However, as the wiring width decreases, the proportion of the barrier metal layer in the wiring width increases rapidly, and the increase in wiring resistance progresses at an accelerating rate.

[0003] To address this challenge, the use of Mo (molybdenum) and Ru (ruthenium) as wiring materials is being considered. These metallic materials have relatively high melting points, allowing for thinner barrier metals, and are therefore expected to reduce the resistance of the wiring, including the barrier metal. Furthermore, since wiring patterns can be formed using plasma etching and other methods, these metallic materials are expected to enable the creation of wiring patterns from metal films with relatively large grain boundaries, thus making them promising materials for achieving low-resistance wiring.

[0004] Furthermore, as shown in Non-Patent Document 1, the resistance of metal wiring can be calculated not only from the resistance of the metal material, but also from the sum of the resistance due to electron scattering at the sidewalls of the wiring pattern and the resistance due to electron scattering at the grain boundaries. Therefore, in order to achieve low-resistance wiring, processing techniques that suppress the roughness and surface alteration of the surface and sidewalls of the wiring pattern are important.

[0005] Japanese Patent Publication No. 2019-186322

[0006] RS Smith, 12 others, “An evaluation of Fuchs-Sondheimer and Mayadas-Shatzkes models below 14nm node wide lines”, February 13, 2019, AIP Advances 9, 025015 (2019) Stefan Decoster, 7 others, “Patterning challenges for direct metal etch of ruthenium and molybdenum at 32 nm metal pitch and below”, Journal of Vacuum Science and Technology B 40, 032802 (2022) Miyako Matsui, et al. Raton, 2008).

[0007] First, Non-Patent Documents 2 and 3 disclose a technique for forming wiring patterns using wiring materials such as Mo and Ru by dry etching. Non-Patent Documents 2 and 3 disclose a technique for forming wiring patterns using oxygen gas (O ２The wiring patterns are processed by plasma etching using a mixed gas containing ) and halogen gas. In wiring patterns, the wiring resistance increases when roughness is formed on the surface and sidewalls. Therefore, in order to form low-resistance wiring patterns, it is necessary to process the wiring so that the cross-section is processed to the desired shape, while simultaneously suppressing the formation of roughness on the surface and sidewalls. When processing wiring patterns by dry etching, the mask pattern is transferred to the underlying wiring material, so suppressing the roughness of the mask is a challenge. In addition, in metal wiring, electrons are easily scattered at the grain boundaries, so the wiring resistance depends on the size of the crystal grains, and when the crystal grains are small, the wiring resistance increases, which is a challenge. Furthermore, when processing wiring patterns by plasma etching, etc., the grain boundaries in the metal material are more easily etched than the inside of the crystal grains, so there is a challenge that the roughness of the sidewalls of the wiring pattern increases as etching progresses from the grain boundaries.

[0008] Figures 3A and 3B illustrate the problems in conventional wiring pattern processing. Figure 3A shows a schematic diagram of the cross-sectional shape of the pattern, and Figure 3B shows a top view of the pattern in Figure 3A. For example, when processing a Ru pattern, which is the layer to be etched 102, using a mask pattern 103 as a mask by plasma etching, a problem arises when ions 109 and radicals 110 generated by the plasma irradiate the sidewalls of the Ru pattern, causing roughness to form or the cross-sectional shape to become bowed. The top view of the pattern shown in Figure 3B shows the problem of roughness being formed in the Ru pattern, which is the layer to be etched 102. In particular, since the crystal grain boundaries 105 have disordered crystallinity, they are more easily etched than the inside of the crystal grains, so there is a problem that etching progresses from the crystal grain boundaries 111 and roughness is formed.

[0009] As a method to suppress etching of the sidewalls and reduce in-wafer variation in the etching rate and shape of the Ru pattern, Patent Document 1 discloses an etching method in which plasma treatment using an oxygen (O)-containing gas and plasma treatment using a chlorine-containing gas are alternately repeated. This method involves irradiating the Ru pattern with a precursor gas derived from a metal other than Ru, such as tungsten (W), or from an oxide or nitride, to form a sidewall protective film, and then performing plasma etching with a mixed gas of O and chlorine to process the Ru pattern vertically while suppressing side etching. However, in the method of forming a protective film using a precursor gas, it was necessary to form a substance containing elements other than Ru, especially metallic elements, on the pattern sidewalls, which can contaminate the wiring pattern and result in defects, thus reducing the reliability of the wiring pattern. Furthermore, because the crystallinity of Ru is disordered at the grain boundary 105, the precursor gas cannot be uniformly adsorbed at the atomic layer level, making it impossible to form a uniform protective film.

[0010] According to one aspect of the present disclosure, a plasma treatment method for etching a metal film using plasma comprises: a first step of etching the metal film with plasma generated using a gas containing oxygen and a gas containing halogen; a second step of nitriding the etched metal film with plasma after the first step; and a third step of etching the nitrided metal film with plasma generated using a gas containing halogen, wherein the second and third steps are repeated until the depth of the etched metal film reaches a predetermined depth.

[0011] Here, the second step can be changed to a step of sulfiding the etched metal film with plasma, or a step of chlorinating the etched metal film with plasma. In this case, the "nitrided metal film" in the third step is changed to a sulfided metal film or a chlorinated metal film.

[0012] This reduces the roughness of the Ru pattern, and in particular, suppresses side etching and roughness formation from the grain boundaries. By enabling etching of fine patterns with less roughness into a vertical shape, wiring resistance can be reduced.

[0013] This figure shows an example of the process flow of the plasma processing method of this embodiment (Embodiment 1). This is an explanatory diagram of the sample cross-sectional structure in the process flow (S1-S5) of the plasma processing method of this embodiment, where (a) is a cross-sectional view, (b) is a top view, and (c) is an enlarged view of the vicinity of the crystal grain boundary in the top view. This is an explanatory diagram of the problems in conventional wiring pattern processing, and is a cross-sectional view of the wiring pattern. This is an explanatory diagram of the problems in conventional wiring pattern processing, and is a top view of the wiring pattern in Figure 3A. This figure shows an example of a plasma processing apparatus to which this embodiment is applied. This figure shows another example of the process flow of the plasma processing method of this embodiment (Embodiment 2). This figure shows another example of the process flow of the plasma processing method of this embodiment (Embodiment 3).

[0014] The embodiments of this disclosure will be described in detail below with reference to the drawings. In all drawings, components having the same function will be denoted by the same reference numerals, and repeated explanations will be omitted.

[0015] As a plasma processing method of this disclosure, Example 1 of the plasma etching method will be described below. In Example 1, a selective nitriding treatment is performed on a region including the sidewall surface of a pattern of a wiring material containing Ru (ruthenium) or Mo (molybdenum) in a processing chamber 31. Furthermore, a protective film containing carbon (C) is formed on the region including the sidewall of the pattern, and then the material to be etched, such as Ru or Mo, is etched and removed with a plasma containing oxygen (O) and halogens. Furthermore, after etching, the protective film remaining on the pattern and residues such as reaction products from etching are removed.

[0016] Figure 1 is a diagram showing an example of the process flow of the pattern formation method of this embodiment. Figure 2 is a diagram showing an example of a pattern cross-sectional view to explain the process flow (S1-S5) of the pattern formation method of this embodiment. In Figure 2, (a) is a cross-sectional view in the vertical direction of the pattern to be etched, (b) is a top view of the pattern to be etched in the cross-section A-A shown in (a), and (c) is an enlarged top view of the vicinity of the grain boundary 105.

[0017] In this embodiment, a method for processing an etchable layer 102 containing Mo or Ru with low roughness and vertically, using a mask pattern 103 as a mask, as shown in (a) of the process flow (S1-S5) in Figure 2, will be described based on the process flow in Figure 1. As the etchable layer 102, which is a metallic material, for example, a metal film containing Mo or Ru can be used. In Figure 2, the substrate 101 corresponds to the wafer 100. In this embodiment, as an example, the case in which silicon nitride film (SiN) is used as the material for the mask pattern 103 and Ru is used as the metallic material for the etchable material (metal film) 102 will be described. The material for the mask pattern 103 is silicon oxide film (SiO ２ Materials containing O, nitrogen (N), and C in addition to Si, such as silicon nitride (SiN), silicon carbide (SiC), titanium nitride (TiN), and titanium dioxide (TiO2). ２ Materials containing titanium (Ti), such as aluminum oxide (Al ２ O ３ The same method can be used for materials containing aluminum (Al) or tantalum (Ta), such as tantalum nitride (TaN), and materials containing carbon (C).

[0018] Figure 4 shows the overall configuration of an example of the plasma processing apparatus 30 used in this disclosure. The plasma processing apparatus 30 includes a processing chamber 31, a wafer stage 32, a gas supply unit 33, a nitriding gas 34, a C-containing film formation gas 35, a trimming gas 36, an etching gas 37, a protective film removal gas 38, a bias power supply 39, a high-frequency power supply 40, a high-frequency application unit 41, and an apparatus control unit 43. The apparatus control unit 43 includes functional blocks such as a gas control unit 44, an exhaust system control unit 45, a high-frequency control unit 46, a bias control unit 47, a nitriding process control unit 48, a protective film formation process control unit 49, an etching control unit 50, and a storage unit 51.

[0019] The plasma processing apparatus 30 includes a wafer stage 32, which serves as a sample mounting platform, located within a processing chamber 31, and a gas supply unit 33 equipped with gas cylinders and valves. Based on a control signal 57 from the apparatus control unit 43, nitriding gas 34, carbon-containing film forming gas 35, trimming gas 36, etching gas 37, and protective film removal gas 38 are supplied to the processing chamber 31 according to the processing step. The processing gas supplied to the processing chamber 31 is decomposed into plasma 42 within the processing chamber 31 by high-frequency power 56 applied to the high-frequency application unit 41 from a high-frequency power supply 40 controlled by the apparatus control unit 43. The pressure inside the processing chamber 31 can be kept constant by a variable conductance valve (not shown) and a vacuum pump connected to the processing chamber 31, while a predetermined flow rate of processing gas is flowing. Radicals 110 generated by decomposition into plasma 42 within the processing chamber 31 diffuse within the processing chamber 31 and irradiate the surface of the wafer 100, which serves as a sample, placed on the wafer stage 32. The ions 109 generated in the plasma 42 are accelerated by a bias voltage 55 applied to the wafer stage 32 from a bias power supply 39 controlled by the bias control unit 47, and irradiated onto the surface of the wafer 100.

[0020] First, the wafer 100 is placed on the wafer stage 32 in the processing chamber 31, and the process of etching the etched layer 102 with respect to the pattern formed on the wafer 100 is started (step S1: initial etching process: the first process). Based on the control signal 56 from the device control unit 43, the etching gas 37 is supplied to the processing chamber 31 at a predetermined flow rate. The supplied etching gas 37 becomes plasma 42 by the high-frequency power 56 applied to the high-frequency application unit 41, and generates radicals 110 and ions 109 that etch the etched layer 102. The radicals 110 and ions 109 generated by the plasma 42 reach the surface of the wafer 100, and as shown in (i) of FIG. 2, using the mask pattern 103 as a mask, the etching of the etched layer 102 containing Ru or Mo is started. As the etching gas 37, for example, chlorine gas (Cl ２ ) 、 hydrogen bromide gas (HBr), nitrogen trifluoride gas (NF ３ ) ６ sulfur hexafluoride gas (SF ６ ) ２ ), and a mixed gas of O ２ gas, carbon dioxide (CO ２ ) ２ gas and other O-containing gases can be used. Alternatively, tetrafluoromethane gas (CF ４ ), trifluoromethane gas (CHF ３ ), and other fluorocarbon gases, a mixed gas of hydrofluorocarbon gas and O ２ gas, CO ２ gas and other O-containing gases can be used. The ions generated from the etching gas 37 are accelerated by the bias voltage 55 applied from the bias power supply 41 controlled by the bias control unit 47 to the wafer stage 32 and irradiated onto the surface of the wafer 100. That is, in the first step (S1), the metal film (the etched layer 102 containing Ru or Mo) is etched by the plasma generated using a gas containing an oxygen element and a gas containing a halogen element.

[0021] For example, as the etching gas 37, chlorine gas (Cl ２ ) ２When a plasma 42 is generated using a gas mixture and Ru is etched as the material to be etched, RuO, which has a low boiling point and is volatile, is produced. ４ and ruthenium chloride (RuCl ｘ O ｙ It is thought that etching proceeds as a result of the formation of volatile ruthenium compounds such as ). Figure 2(i) shows a cross-sectional view of the pattern to be etched in the initial etching process (step S1) (a), a top view of the pattern to be etched in the cross-section A-A shown in (a) (b), and an enlarged top view of the vicinity of the grain boundary 105 (c). As etching of the layer to be etched 102 progresses, the grain boundary region is more prone to etching than the grain portion because its crystallinity is disordered, which causes an increase in the roughness of the groove pattern. Therefore, the initial etching (step S1) is terminated and the nitriding treatment (step S2: second process: Figure 2(ii)) is started before etching progresses in the grain boundary 105 portion.

[0022] Based on a control signal 56 from the apparatus control unit 43, nitriding gas 34 is supplied to the processing chamber 31 at a predetermined flow rate. The supplied nitriding gas 34 becomes plasma 42 when high-frequency power 56 is applied to the high-frequency application unit 41, generating radicals and ions containing nitrogen. The nitriding process control unit 48 can control the thickness and quality of the nitrided film 106 by setting and adjusting the flow rate of the nitriding gas 34, the pressure in the processing chamber 31, the high-frequency power 56 applied to the high-frequency application unit 41, the substrate temperature, the plasma irradiation time, etc. The radicals and ions containing nitrogen generated in the plasma 42 nitride the region including the pattern sidewalls of the layer to be etched. As the nitriding gas 34, for example, nitrogen gas (N) ２ A mixed gas containing ) can be used. N ions generated from the nitriding gas 34 are accelerated by a bias voltage 55 applied to the wafer stage 32 from a bias power supply 41 controlled by the bias control unit 47 and irradiated onto the surface of the wafer 100, nitriding the region including the pattern sidewall of the layer to be etched. In other words, in the second step (S2), after the first step (S1), the etched metal film (layer to be etched 102) is nitrided by plasma.

[0023] For example, N ２ A plasma can be generated using a mixed gas of gas and argon (Ar) gas to nitride the Ru pattern sidewall, which is the layer to be etched 102. As the nitriding gas 34, N ２ When gas is supplied to the processing chamber 31, and plasma 42 is generated by high-frequency power 56 applied to the high-frequency application unit 41, and radicals and ions containing N are generated, ２ By generating a plasma with an electron temperature higher than the bond dissociation energy of the gas, the nitriding effect of the film to be etched can be increased. Non-patent document 4 states that N ２ The bond-dissociation energy of the gas has been reported to be 984.84 kJ / mol (10.2 eV). Examples of other gases include, for example, O ２ Since the gas is 498.36 kJ / mol (5.16 eV), N ２ To dissociate the gas, it is effective to generate a plasma with a relatively high electron temperature of about 10 eV, or an electron temperature of 10 eV or higher. Therefore, it is effective to apply a high-frequency power 56 to the high-frequency application unit 41 such that the electron temperature of the plasma 42 becomes about 10 eV, or 10 eV or higher.

[0024] Figure 2(ii) shows a cross-sectional view (a) of the etched pattern in the nitriding process (step S2), a top view (b) of the etched pattern in the cross-section A-A shown in (a), and an enlarged top view (c) of the vicinity of the grain boundary 105. The surface of the etched layer 102, including the sidewalls of the grooves 104, is nitrided by radicals containing N and ions irradiated from the plasma. The grain boundaries 105 on the sidewalls of the etched pattern can also be nitrided. When the etched film is Ru, for example, RuN is formed as the nitrided film 106. In this way, by nitriding the etched sidewalls, the Ru surface is chemically stabilized, which suppresses further etching of the sidewalls during etching of the etched film, and makes it possible to suppress the occurrence of shape abnormalities and roughness.

[0025] Once the nitriding treatment (step S2) is completed, the carbon-containing film formation step (step S3: third step: (iii) in Figure 2) is started. Based on a control signal 56 from the apparatus control unit 43, carbon-containing film formation gas 35 is supplied to the processing chamber 31 at a predetermined flow rate. The supplied carbon-containing film formation gas 35 becomes plasma 42 when high-frequency power 56 is applied to the high-frequency application unit 41, generating carbon-containing radicals and ions. The carbon-containing radicals and ions generated in the plasma 42 form a carbon-containing protective film (carbon-containing film 107) in the region including the pattern sidewalls of the etched layer 102 that was nitrided in step S3. Here, the surface of the sidewalls of the etched layer formed in the nitriding treatment (step S2) may not be uniformly nitrided because the crystallinity is disordered at the grain boundaries. In such cases, in particular, by protecting the sidewalls of the etched layer 102 with a carbon-containing film through the carbon-containing film formation treatment (step S3), it is possible to suppress both chemical etching by radicals and etching by ion irradiation. In other words, in the third step (S3), after the second step (S2), a protective film containing carbon elements (C-containing film 107) is formed on the nitrided metal film (side wall of the nitrided etched layer 102) using plasma generated with a carbon-containing gas.

[0026] The protective film formation process control unit 49 can control the film thickness and quality of the carbon-containing film 107 by setting and adjusting the flow rate of the carbon-containing film formation gas 35, the pressure in the processing chamber 31, the high-frequency power 56 applied to the high-frequency application unit 41, the substrate temperature, the plasma irradiation time, etc. As the carbon-containing film formation gas 35, for example, methane (CH4) ４ ) 、 CF ４、 CHF ３、 Fluoromethane (CH ３ F) 、 Octafluorocyclobutane (C ４ F8), CO ２、 Carbon monoxide (CO), carbonyl sulfide (COS), and other C-containing gases, or the aforementioned gases with Ar gas, helium (He) gas, and O ２ gas 、 CO ２ gas 、CO gas, COS gas, sulfur dioxide (SO ２ ) Gas, N ２ gas 、 Hydrogen (H ２ ) gas, HBr gas, boron trichloride (BCl ３ A mixed gas such as ) can be used. The thickness of the C-containing film 107 can be adjusted by the plasma irradiation time, the gas flow rate of the C-containing film formation gas 35, the substrate temperature, etc. Alternatively, the thickness of the C-containing film 107 can be adjusted by adjusting the reactivity between the generated radicals and ions and the nitride film surface by controlling the high-frequency power 56 applied to the high-frequency application unit 41, or the time for which the high-frequency power 56 is applied, thereby adjusting the degree of plasma dissociation. Furthermore, if the line width is not uniform on the wafer surface, for example, if the C-containing film thickness becomes thinner when the wafer temperature is higher than the standard conditions and thicker when the wafer temperature is lower than the standard conditions, the wafer temperature dependence of the C-containing film thickness can be obtained in advance, and the wafer temperature can be adjusted on the wafer surface during C-containing film formation to suppress variations in line width on the wafer surface.

[0027] Figure 2(iii) shows a cross-sectional view (a) of the etched pattern after the C-containing film formation process (step S3), a top view (b) of the etched pattern in the cross-section A-A shown in (a), and an enlarged top view (c) of the vicinity of the grain boundary 105. On the surface including the sidewall of the nitride film formed in the groove 104 of the etched layer 102, a C-containing film 107 is formed by C-containing radicals and ions irradiated from the plasma. Etching tends to proceed inward from the grain boundary 105, but if etching has already begun to proceed from the grain boundary 105, the C-containing film 107 is formed to fill the recess in the sidewall of the grain boundary 105. The surface of the nitride film 106 immediately after the nitriding treatment (step S2) is chemically stable RuN, or RuN ｘA protective film is formed, which suppresses the etching reaction of the sidewalls by etchants such as Cl and O, thereby suppressing roughness. Furthermore, when the C-containing film formation step (step S3) is performed, a C-containing film 107 is formed in a region that includes the mask 03 and also includes the surface 106 of the nitrided layer to be etched. By forming the C-containing film 107 in the region including the mask 103, a C-containing protective film is formed so as to fill the recesses in the sidewalls of the grain boundaries 105, thereby suppressing etching from the grain boundaries 105. The C-containing film 107 suppresses etching of the sidewalls by radicals, and when ions are irradiated onto the sidewalls, the C-containing protective film attenuates the energy of the ions, suppressing etching by ions as well, thus reducing the roughness of the metal pattern. Furthermore, a CN bond is formed at the interface between the nitrided film 106 and the C-containing film 107, and the films are formed in close contact, so a protective film with less roughness can be formed. If the formed carbon-containing film 107 is thicker than a predetermined thickness, or if the shape of the carbon-containing film 107 is not the desired shape, a trimming gas can be introduced into the processing chamber 31, and a portion of the carbon-containing film 107 can be removed by etching with radicals and ions generated from the plasma 42, thereby smoothing the shape of the carbon-containing film 107, reducing the roughness of the pattern and the surface of the carbon-containing film, and simultaneously obtaining the desired mask dimensions. Examples of trimming gases 36 include Ar gas, He gas, and O ２ gas 、 CO ２ gas 、 CO gas, COS gas, SO ２ Gas, N ２ gas 、 Hydrogen gas (H ２ ) mixed gases, or NF ３ CF ４ CHF ３ SF ６ Gases containing fluorine (F), such as those listed above, can be used.

[0028] Once the C-containing film is formed (step S3), etching of the layer to be etched 102 (step S4: fourth step: (iv) in Figure 2) is started. Based on the control signal 56 from the apparatus control unit 43, etching gas 37 is supplied to the processing chamber 31 at a predetermined flow rate. The supplied etching gas 37 becomes plasma 42 by the high-frequency power 56 applied to the high-frequency application unit 41, generating radicals 110 and ions 109. The radicals 110 and ions 109 generated in the plasma 42 reach the surface of the wafer 100, and as shown in Figure 2(iv), etching of the layer to be etched 102 is started using the mask pattern 103 and a part of the C-containing film 107 as masks. In this embodiment, the etching gas 37 is Cl ２ Gas and O ２ The case where a gas mixture is used is shown. Other etching gases 37 include, for example, Cl ２、 HBr, NF ３ SF ６ A gas containing halogen gases such as, or the said gas and O ２ A mixed gas such as gas can be used. Alternatively, CF ４ CHF ３ Fluorocarbon gases such as hydrofluorocarbon gases and O ２ A mixed gas such as gas can also be used as the etching gas 37. Ions generated from the etching gas 37 are accelerated by a bias voltage 55 applied to the wafer stage 32 from a bias power supply 39 controlled by a bias control unit 47 and irradiated onto the surface of the wafer 100. In other words, in the fourth step (S4), after the third step (S3), the metal film (etched layer 102) on which the protective film (C-containing film 107) has been formed is etched with plasma generated using a gas containing halogen elements.

[0029] Here, in etching in step S4, if ions 109 and radicals 110 are irradiated onto the sidewalls of the layer to be etched 102, the protective film formed by the nitride film 106 and C-containing film 107 formed in steps S3 and S4 can suppress excessive etching in the direction of the sidewalls, thereby suppressing bowing and an increase in roughness. Also, although etching progresses more easily at the grain boundaries 105 than at the grain portions, the protective film formed by the nitride film 106 and C-containing film 107 formed in steps S3 and S4 can suppress the progression of etching and an increase in roughness. When the nitride film 106 and C-containing film 107 are formed at the bottom 108 of the layer to be etched 102 in steps S3 and S4, ion energy is required for ions 109 irradiated from the plasma 42 to pass through the nitride film 106 and C-containing film 107 formed at the bottom 108 of the layer to be etched 102. By applying a wafer bias voltage 55 sufficient to have such ion energy, etching of the sidewalls can be suppressed by the nitride film 106 and C-containing film 107 formed in steps S3 and S4, and the bottom portion 108 of the layer to be etched 102 can be etched. Alternatively, as a method to further suppress etching of the sidewalls during etching of the layer to be etched 102 (step S4), a small amount of the nitriding gas 34 and the C-containing film forming gas described in steps S2 and S3 can be added to the etching gas 37 before etching.

[0030] The nitriding treatment (step S2), carbon-containing film formation treatment (step S3), and etching (step S4) cycle is repeated a predetermined number of times until the pattern depth of the layer to be etched 102 on the wafer 100 is etched to a desired depth. The etching is terminated when a predetermined number of etching treatments have been performed or when the desired depth has been reached (step S5). At this time, while the etching process is being performed, the thickness of the carbon-containing film 107, the pattern dimensions, and the etching depth may be measured using an optical system monitoring device provided in the plasma processing apparatus 30 to monitor whether the etching has reached the desired depth.

[0031] After etching is performed to a predetermined depth, the nitride film 106 and the carbon-containing film 107 are removed (protective film removal: step S6: fifth step). Figure 2(v) shows a cross-sectional view of the pattern after etching to a predetermined depth (a), a top view of the etched pattern in the cross-section A-A shown in (a) (b), and an enlarged top view of the vicinity of the grain boundary 105 (c). In other words, in the fifth step, the second to fourth steps are repeated until the depth of the etched metal film reaches a predetermined depth, and then the altered layer containing the sulfurized film (nitride film 106) and protective film (carbon-containing film 107) is removed. The nitride film 106, carbon-containing film 107, etching residue, etc. are formed on the etched pattern. The nitride film 106, carbon-containing film 107, etching residue, etc. remaining on the etched layer 102 need to be removed after etching because they can be mixed into the wiring material as impurities, increasing wiring resistance or causing disconnections. Furthermore, in the case of fine wiring, the width of the wiring and the pitch between wiring are small (narrow), so it is necessary to remove the nitride film 106, C-containing film 106 and etching residue without removing the unaltered etched layer 102, while suppressing the formation of roughness on the side walls. In the protective film and residue removal step (protective film removal step S6), first, the device control unit 43 controls the gas supply unit 33 to supply protective film removal gas 38 to the processing chamber 31 at a predetermined flow rate. When the protective film removal gas 38 is supplied and the inside of the processing chamber 31 reaches a predetermined pressure, the device control unit 43 controls the high-frequency power supply 40 to apply high-frequency power 56 to the high-frequency application unit 41 to generate plasma from the protective film removal gas 38 inside the processing chamber 31. The protective film removal gas 38 becomes plasma and generates radicals 110 and ions 109 that remove the nitride film 106, C-containing film 106, and etching residue on the etched layer 102. For example, H ２ A mixed gas containing gas can be used. Alternatively, H ２、 Gas and N ２A mixed gas such as the above can be used. The C-containing film 107 reacts with H radicals 110 and H ions 109 to generate and remove CH-based reaction products. Furthermore, the nitride film 106 also reacts with H radicals 110 and H ions 109 to generate and remove reaction products such as NHx. In addition, a CN bond is formed at the interface between the nitride film 106 and the C-containing film 107, which reacts with H radicals 110 and H ions 109 to generate and remove reaction products such as HCN. At this time, since the layer to be etched beneath the nitride film 106 and the C-containing film 107 is not easily etched by H, the protective film can be removed without removing the layer to be etched 102. Also, for example, if the layer to be etched 102 is a wiring material containing Ru, the etching residue may include, for example, reaction products of Ru such as RuOx and RuClx, reaction products containing Si generated from the mask 103, and reaction products generated from the C-containing film 107. These etching residues can be removed by volatilization using hydrogen radicals 110 and hydrogen ions 109. ２、 Gas and N ２ Even when using a mixed gas such as the above, the nitride film, C-containing film, and etching residue can be removed by volatilization using hydrogen radicals 110 and hydrogen ions 109. Furthermore, by renitriding the cleaned surface of the etched layer, it is possible to prevent further surface deterioration. In this way, the etching residue remaining on the processed surface can be removed without significantly removing the etched layer 102. This removal step S6 may also be performed after removing the mask 103.

[0032] In this way, by nitriding the pattern sidewalls (S2) to form a nitride film 106 and chemically stabilizing the sidewalls of the layer to be etched, then forming a C-containing film 107 (S3), and etching the layer to be etched at the bottom of the pattern 102 (S4), etching in the lateral direction of the pattern is suppressed, the formation of roughness on the sidewalls is suppressed, and the pattern can be processed in the vertical direction. In particular, etching of the grain boundaries 105 can be suppressed, making it possible to process patterns with less roughness. Furthermore, by performing etching to a desired depth and then treating with a hydrogen-containing plasma (step S6), the nitride film 106, the C-containing film 107, and etching residue on the pattern sidewalls of the layer to be etched 102 can be removed without advancing the etching of the sidewalls of the layer to be etched 102, making it possible to pattern the layer to be etched 102 without causing defects or deteriorating electrical characteristics such as wiring resistance.

[0033] If the surface of the sidewall of the etched layer formed in the nitriding treatment (step S2) is uniformly nitrided, step S4 may be performed after step S2 without performing step S3.

[0034] As a plasma processing method of the present disclosure, Example 2 of the plasma etching method will be described below. In Example 2, a sulfidation treatment is selectively performed on a region including the sidewall surface of a pattern of wiring material containing Ru or Mo in a processing chamber 31. Furthermore, a protective film containing C is formed on the region including the sidewall of the pattern, and then the layer to be etched, such as Ru or Mo, is etched and removed with a plasma containing O and halogen. Furthermore, after etching, the protective film remaining on the pattern and residues such as reaction products from etching are removed.

[0035] Figure 5 shows an example of the process flow of the pattern formation method in this embodiment.

[0036] In this embodiment, after the start of etching (step S1: first step), a process (step S8: second step) is performed in the processing chamber 31 to selectively sulfurize the region including the sidewall surface of the pattern of the wiring material containing Ru or Mo. As an explanatory diagram of the process flow of this embodiment, the nitride film 106 in the explanatory diagram shown in Figure 2 is replaced with the sulfide film 113.

[0037] First, the wafer 100 is introduced onto the stage 32 in the processing chamber 31, and the process of etching the layer to be etched 102 with respect to the pattern formed on the wafer 100 is started (Step S1: Initial etching process: First process). In other words, in the first process (S1), similar to Example 1, the metal film (layer to be etched 102) is etched by plasma generated using a gas containing oxygen and a gas containing halogen elements.

[0038] When etching of the layer to be etched 102 is performed to a predetermined depth, the grain boundary region is more prone to etching than the grain portion because its crystallinity is disordered, which increases the roughness of the groove pattern. Therefore, the initial etching (step S1) is terminated before etching progresses at the grain boundaries, and the sulfidation treatment (step S8: second step) is started.

[0039] Based on a control signal 56 from the device control unit 43, sulfurizing gas is supplied to the processing chamber 31 at a predetermined flow rate. The supplied sulfurizing gas becomes plasma 42 when high-frequency power 56 is applied to the high-frequency application unit 41, generating sulfur (S)-containing radicals and ions. The sulfurization process control unit can control the thickness and quality of the sulfurized film by setting and adjusting the flow rate of the sulfurizing gas, the pressure in the processing chamber, the high-frequency power 56 applied to the high-frequency application unit 41, the substrate temperature, the plasma irradiation time, etc. The S-containing radicals and ions generated in the plasma 42 sulfurize the region including the pattern sidewalls of the layer to be etched. For example, sulfur dioxide (SO4) can be used as the sulfurizing gas. ２ ), or carbonyl sulfide (COS), or hydrogen sulfide (H ２S) A mixed gas containing S can be used. Ions generated from the sulfurizing gas are accelerated by a bias voltage 55 applied to the wafer stage 32 from a bias power supply 41 controlled by the bias control unit 47 and irradiated onto the surface of the wafer 100, sulfurizing the region including the pattern sidewall of the layer to be etched. For example, SO ２ A plasma can be generated using a mixed gas of Ar, and the Ru pattern sidewall, which is the layer to be etched 102, can be sulfurized.

[0040] The surface of the etched layer 102, including the sidewalls of the grooves 104, is sulfurized by sulfur-containing radicals and ions irradiated from the plasma. The sidewalls of the grain boundaries 105 can also be sulfurized. For example, RuSx is formed as the sulfurized film 113. In other words, in the second step (S8), after the first step (S1), the etched metal film (etched layer 102) is sulfurized by plasma.

[0041] In this way, by sulfiding the etched sidewalls, the Ru surface is chemically stabilized, which suppresses lateral etching of the sidewalls during etching of the film to be etched, thereby suppressing the occurrence of shape abnormalities and roughness.

[0042] Once the sulfidation treatment (step S8) is completed, the carbon-containing film formation step (step S3: third step) is started, similar to Example 1. Based on the control signal 56 from the apparatus control unit 43, carbon-containing film formation gas 35 is supplied to the processing chamber 31 at a predetermined flow rate. The supplied carbon-containing film formation gas 35 becomes plasma 42 when high-frequency power 56 is applied to the high-frequency application unit 41, generating carbon-containing radicals and ions. The carbon-containing radicals and ions generated in the plasma 42 form a carbon-containing protective film 107 in the region including the pattern sidewalls of the etched layer that was sulfided in step S8. Here, the surface of the sidewalls of the etched layer formed in the sulfidation treatment (step S8) may not be uniformly sulfided because the crystallinity is disordered at the grain boundaries. In such cases, in particular, by protecting the sidewalls of the etched layer 102 with a carbon-containing film 107 through the carbon-containing film formation treatment, it is possible to suppress both chemical etching by radicals and etching by ion irradiation. In other words, in the third step (S3), after the second step (S8), a protective film containing carbon (C-containing film 107) is formed on the sulfurized metal film using plasma generated with a carbon-containing gas.

[0043] The protective film formation process control unit 49 can control the film thickness and quality of the carbon-containing film 107 by setting and adjusting the flow rate of the carbon-containing film formation gas 35, the pressure in the processing chamber 31, the high-frequency power 56 applied to the high-frequency application unit 41, the substrate temperature, the plasma irradiation time, etc. For example, the carbon-containing film formation gas 35 is CH ４、 CF ４、 CHF ３、 CH ３ F 、 C ４ F8, CO ２、 CO, COS and other carbon-containing gases, or the aforementioned gases with Ar, He, O ２ gas 、 CO ２ gas 、 CO gas, COS gas, SO ２ Gas, N ２ , H ２ HBr gas, BCl ３ A mixture of gases, such as gases, can be used.

[0044] After the carbon-containing film formation step (step S3), a carbon-containing film 107 is formed on the surface including the sidewalls of the sulfide film formed in the grooves 104 of the pattern to be etched by carbon-containing radicals and ions irradiated from the plasma. Etching tends to proceed inward from the grain boundary 105, but if etching has already begun from the grain boundary 105, the carbon-containing film 107 is formed to fill the depressions in the sidewalls of the grain boundary 105. Immediately after the sulfidation treatment (step S8), a chemically stable RuSx is formed on the surface of the sulfide film, suppressing the etching reaction of the sidewalls by etchants such as Cl and O, thereby suppressing roughness. Furthermore, when the carbon-containing film formation step (step S3) is performed, the carbon-containing film 107 is formed in the region including the mask 103 and the sulfided surface 113 of the etched layer. By forming a carbon-containing film 107 in the region including the mask 103, a carbon-containing protective film is formed to fill the recesses in the sidewalls of the grain boundaries 105, thereby suppressing etching from the grain boundaries 105. The carbon-containing film 107 suppresses etching of the sidewalls by radicals, and when ions are irradiated onto the sidewalls, the carbon-containing protective film attenuates the energy of the ions, suppressing etching by the ions as well, thus reducing the roughness of metal patterns such as Ru patterns. Furthermore, since a CS bond is formed at the interface between the sulfide film 113 and the carbon-containing film 107, the films are formed in close contact, resulting in a protective film with less roughness.

[0045] After forming the carbon-containing film (step S3), etching of the layer to be etched 102 (step S4: fourth step) is started, similar to Example 1. Based on the control signal 56 from the apparatus control unit 43, etching gas 37 is supplied to the processing chamber 31 at a predetermined flow rate. The supplied etching gas 37 becomes plasma 42 by the high-frequency power 56 applied to the high-frequency application unit 41, generating radicals and ions. The radicals and ions generated by the plasma 42 reach the surface of the wafer 100 and use the mask pattern 103 and a part of the carbon-containing film 107 as masks to perform etching of the layer to be etched 102. In other words, in the fourth step, after the third step (S3), the metal film (layer to be etched 102) on which the protective film (carbon-containing film 107) has been formed is etched by plasma generated using a gas containing halogen elements.

[0046] Here, similar to Example 1, the cycle of sulfurization treatment (step S2), C-containing film formation treatment (step S3), and etching (step S4) is repeated a predetermined number of times until the pattern depth of the layer to be etched 102 is etched to the desired depth. Etching is terminated when a predetermined number of etching treatments have been performed or when the desired depth has been reached (step S5).

[0047] When etching is performed to a predetermined depth, the sulfurized film and the C-containing film 107 are removed (step S6: the fifth step). On the etched pattern, a sulfurized film, a C-containing film 107, etching residues, etc. are formed. For example, when the etched layer 102 is a wiring material, it is necessary to suppress and remove the roughness formation on the sidewalls of the sulfurized film, C-containing film 107, etching residues, etc. remaining on the etched layer 102. In the protective film and residue removal step (S6), first, the apparatus control unit 43 controls the gas supply unit 33 to supply the protective film removal gas 38 to the processing chamber 31 at a predetermined flow rate. With the protective film removal gas 38 supplied and the inside of the processing chamber 31 at a predetermined pressure, the apparatus control unit 43 controls the high-frequency power supply 40 to apply high-frequency power 56 to the high-frequency application unit 41 to generate plasma by the protective film removal gas 38 inside the processing chamber 31. The protective film removal gas 38 becomes plasma and generates radicals 110 and ions 109 that remove the sulfurized film, C-containing film 107, and etching residues on the etched layer 102. As the protective film removal gas 38, for example, a mixed gas containing H ２ gas can be used. Alternatively, a mixed gas of H ２、 gas and N ２ etc. can be used. The C-containing film 107 can react with H radicals 110 and H ions 109 to generate and remove CH-based reaction products. Further, the sulfurized film can also react with H radicals 110 and H ions 109 to generate and remove reaction products such as H ２ S. A CS bond is formed at the interface between the sulfurized film 113 and the C-containing film 107, but it reacts with H radicals 110 and H ions 109 to form H ２ S, CH ｘReaction products such as the above can be generated and removed. At this time, since the layer to be etched beneath the sulfide film and the C-containing film 107 is not easily etched by H, the protective film can be removed without removing the layer to be etched 102. Examples of the layer to be etched include sulfides such as RuSx, reaction products of Ru such as RuOx and RuClx, reaction products containing Si generated from the mask 103, and reaction products generated from the C-containing film 107. These etching residues can be removed by volatilization using hydrogen radicals 110 and hydrogen ions 109. In this way, the etching residue remaining on the processed surface can be removed without significantly removing the layer to be etched 102. In other words, in the fifth step, the second to fourth steps are repeated until the depth of the etched metal film reaches a predetermined depth, and then the altered layer containing the sulfide film and the protective film (C-containing film 107) is removed.

[0048] If the surface of the sidewall of the etched layer formed in the elution treatment (step S8) is uniformly eluted, step S4 may be performed after step S2 without performing step S3.

[0049] As a plasma processing method of the present disclosure, Example 3 of the plasma etching method will be described below. In this Example 3, a selective chlorination treatment is performed on a region including the sidewall surface of a pattern of wiring material containing Ru or Mo in a processing chamber 31. Furthermore, a protective film containing C is formed on the region including the sidewall of the pattern, and then the layer to be etched, such as Ru or Mo, is etched and removed with a plasma containing O and halogen. Furthermore, after etching, the protective film remaining on the pattern and residues such as reaction products from etching are removed.

[0050] Figure 6 shows an example of the process flow of the pattern formation method in this embodiment.

[0051] In this embodiment, after the start of etching (step S1), a process of selectively chlorinating a region including the sidewall surface of a wiring material pattern containing Ru or Mo in the processing chamber 31 is performed. As an explanatory diagram of the process flow of this embodiment, it is shown by replacing the nitride film 106 in the explanatory diagram shown in FIG. 2 with a chloride film.

[0052] The process flow of this embodiment is shown by replacing the nitriding treatment (step S2) in the first embodiment with a chlorination treatment (step S9). In the chlorination treatment (step S9), as the chlorination gas, for example, a mixed gas containing chlorine (Cl ２ ) can be used. On the surface of the chloride film immediately after the chlorination treatment, chemically stable RuCl ３ is formed, and the etching reaction of the sidewall by the etchant Cl or O is suppressed, and the roughness can be suppressed. Further, when the C-containing film forming step (step S3) is performed, a C-containing film 107 is formed in a region including the mask 103 and further including the surface of the etched layer that has been chlorinated. By forming the C-containing film 107 in the region including the mask 103, a C-containing protective film is formed so as to fill the recesses on the sidewalls of the grain boundaries 105, and the etching from the grain boundaries 105 can be suppressed. The C-containing film 107 suppresses the etching of the sidewall by radicals, and when ions are irradiated onto the sidewall, the energy of the ions is attenuated in the C-containing protective film, and the etching by the ions is also suppressed, so that the roughness of a metal pattern such as a Ru pattern can be reduced. Further, since a CCl bond is formed at the interface between the chloride film and the C-containing film 107, the above-mentioned films are formed in close contact with each other, and a protective film with little roughness can be formed.

[0053] The C-containing film forming step (step S3), the etching step (step S4), the etching end step (step S5), and the protective film removing step (step S6) are performed by replacing the nitride film and the nitriding treatment in the process described in the first embodiment with a chloride film and a chlorination treatment, so that a metal pattern with little sidewall roughness can be formed.

[0054] That is, embodiment 3 can be summarized as having the following steps.

[0055] First step (S1): The metal film (etched layer 102) is etched using plasma generated with a gas containing oxygen and a gas containing halogen.

[0056] Second step (S9): After the first step (S1), the etched metal film (etched layer 102) is chlorinated by plasma.

[0057] Third step (S3): After the second step (S9), a protective film containing carbon elements (C-containing film 107) is formed on the chlorinated metal film (etched layer 102) using plasma generated with a carbon-containing gas.

[0058] Fourth step (S4): After the third step (S3), the metal film (etched layer 102) on which the protective film (C-containing film 107) has been formed is etched with plasma generated using a gas containing halogen elements. Then, the second step (S9) to the fourth step (S4) are repeated until the depth of the etched metal film reaches a predetermined depth.

[0059] Fifth step: After repeating the second to fourth steps until the depth of the etched metal film reaches a predetermined depth, the altered layer containing the chlorinated film and protective film (C-containing film 107) is removed.

[0060] If the surface of the sidewall of the etched layer formed by the chlorination treatment (step S9) is uniformly chlorinated, step S4 may be performed after step S9 without performing step S3.

[0061] Although the present invention has been specifically described above based on the examples, it goes without saying that the present invention is not limited to the above examples and can be modified in various ways without departing from its essence. For example, the above examples are described in detail in order to explain the present invention in an easy-to-understand manner and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to add, delete, or replace some of the configurations in each example with other configurations.

[0062] 30: Plasma processing apparatus, 31: Processing chamber, 32: Wafer stage, 33: Gas supply unit, 34: Nitriding gas, 35: C-containing film formation gas, 36: Trimming gas, 37: Etching gas, 38: Protective film removal gas, 39: Bias power supply, 40: High-frequency power supply, 41: High-frequency application unit, 42: Plasma, 43: Apparatus control unit, 44: Gas control unit, 45: Exhaust system control unit, 46: High-frequency control unit, 47: Bias control unit, 48: Nitriding process control unit, 49: Protective film formation process control unit, 50: Etching control unit, 51: Memory unit, 55: Bias voltage, 56 : High-frequency power, 57: Control signal, 100: Wafer, 101: Substrate, 102: Layer to be etched, 103: Mask pattern, 104: Groove portion of pattern, 105: Grain boundary, 106: Nitride film, 107: C-containing film, 108: Bottom of pattern, 109: Ion, 110: Radical, 111: Etched portion from grain boundary, 112: Roughness recess, 113: Sulfide film, S1: Initial etching process, S2: Nitriding treatment, S3: C-containing film formation, S4: Etching, S5: Depth determination, S6: Protective film removal process, S7: End, S8: Sulfidation treatment, S9: Chloridation treatment.

Claims

1. A plasma treatment method for etching a metal film using plasma, comprising: a first step of etching the metal film with plasma generated using a gas containing oxygen and a gas containing halogen; a second step of nitriding the etched metal film with plasma after the first step; and a third step of etching the nitrided metal film with plasma generated using a gas containing halogen after the second step, wherein the second and third steps are repeated until the depth of the etched metal film reaches a predetermined depth.

2. A plasma treatment method for etching a metal film using plasma, comprising: a first step of etching the metal film with plasma generated using a gas containing oxygen and a gas containing halogen; a second step of sulfidizing the etched metal film with plasma after the first step; and a third step of etching the sulfidized metal film with plasma generated using a gas containing halogen after the second step, wherein the second and third steps are repeated until the depth of the etched metal film reaches a predetermined depth.

3. A plasma treatment method for etching a metal film using plasma, comprising: a first step of etching the metal film with plasma generated using a gas containing an oxygen element and a gas containing a halogen element; a second step of chlorinating the etched metal film with plasma after the first step; and a third step of etching the chlorinated metal film with plasma generated using a gas containing a halogen element after the second step, wherein the second and third steps are repeated until the depth of the etched metal film reaches a predetermined depth.

4. A plasma treatment method for etching a metal film using plasma, comprising: a first step of etching the metal film with plasma generated using a gas containing oxygen and a gas containing halogen; a second step of nitriding the etched metal film with plasma after the first step; a third step of forming a protective film containing carbon on the nitrided metal film with plasma generated using a gas containing carbon after the second step; and a fourth step of etching the metal film on which the protective film has been formed with plasma generated using a gas containing halogen, wherein the second to fourth steps are repeated until the depth of the etched metal film reaches a predetermined depth.

5. A plasma treatment method for etching a metal film using plasma, comprising: a first step of etching the metal film with plasma generated using a gas containing oxygen and a gas containing halogen; a second step of sulfiding the etched metal film with plasma after the first step; a third step of forming a protective film containing carbon on the sulfided metal film with plasma generated using a gas containing carbon after the second step; and a fourth step of etching the metal film on which the protective film has been formed with plasma generated using a gas containing halogen, wherein the second to fourth steps are repeated until the depth of the etched metal film reaches a predetermined depth.

6. A plasma treatment method for etching a metal film using plasma, comprising: a first step of etching the metal film with plasma generated using a gas containing oxygen and a gas containing halogen; a second step of chlorinating the etched metal film with plasma after the first step; a third step of forming a protective film containing carbon on the chlorinated metal film with plasma generated using a gas containing carbon after the second step; and a fourth step of etching the metal film on which the protective film has been formed with plasma generated using a gas containing halogen, wherein the second to fourth steps are repeated until the depth of the etched metal film reaches a predetermined depth.

7. A plasma treatment method according to claim 4, further comprising a fifth step of removing the altered layer including the nitrided film and the protective film, after repeating the second to fourth steps until the depth of the etched metal film reaches a predetermined depth.

8. A plasma treatment method according to claim 5, further comprising a fifth step of removing the altered layer including the sulfurized film and the protective film, after repeating the second to fourth steps until the depth of the etched metal film reaches a predetermined depth.

9. A plasma treatment method according to claim 6, further comprising a fifth step of removing the altered layer including the chlorinated film and the protective film, after repeating the second to fourth steps until the depth of the etched metal film reaches a predetermined depth.

10. A plasma treatment method according to any one of claims 1 to 9, characterized in that the metal film is a ruthenium film (Ru) or a molybdenum film (Mo).

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