Plasma processing method

Abstract

A plasma processing method for plasma etching a metal film formed below a metal wiring pattern using the metal wiring pattern according to one embodiment of the present invention includes: a first step (S31) for forming a protective film on the metal wiring pattern by plasma generated using a first gas; a second step (S32) for etching the metal film by plasma generated using a second gas after the first step; a third step (S33) for etching the metal film after the second step by plasma generated using a third gas such that the etching shape of the metal film becomes a vertical shape after the second step; and a fourth step (S35) for removing the protective film formed on the metal wiring pattern by plasma generated using a fourth gas. The second step (S32) and the third step (S33) are repeated until the etching depth of the metal film reaches a predetermined depth.

Description

Plasma treatment method

[0001] The present invention relates to a plasma processing method.

[0002] As semiconductor device structures become more miniaturized and three-dimensional, the application of alternative metals to copper as wiring metals is being considered. One example is ruthenium, which can be patterned by plasma etching. Ruthenium wiring has a layered structure and requires appropriate plasma etching through a mask to create a pattern. Ruthenium patterns can be created by irradiating a pre-masked ruthenium surface with plasma generated from a gas mixture containing oxygen gas and halogen gas, followed by vertical etching. However, as the number of wiring layers increases and the wiring width becomes finer, ruthenium wiring processing is expected to become more complex and the number of steps required will increase.

[0003] US Patent Application Publication No. 2022 / 0139823

[0004] P. Marien et al., "Integrating 8nm Self-Aligned Tip-to-Tip to Enable 4-track Standard Cell Architecture as Scaling Booster", 2023 IEEE International Interconnect Technology Conference (IITC) and IEEE Materials for Advanced Metallization Conference (MAM)(ITC / MAM), Dresden, Germany, 2023, pp. 1-3, DOI: 10.1109 / IITC / MAM57687.2023.10154710

[0005] Generally, wiring in devices using ruthenium has a stacked structure. In this specification, the stacked wiring is simplified to two layers, referred to as the top ruthenium layer and the bottom ruthenium layer, respectively. A method is being considered to optimize the processing process by treating the top ruthenium pattern as a mask and etching the bottom ruthenium layer vertically immediately after processing the top ruthenium pattern.

[0006] For example, Non-Patent Document 1 proposes a process for insulating adjacent elements by vertically etching the bottom ruthenium exposed to the plasma interface relative to a previously etched upper ruthenium pattern and the bottom ruthenium buried via an insulating layer (Figure 1). In Figure 1, 10 denotes a mask, 11 denotes the upper ruthenium pattern, 12 denotes the insulating layer, 13 denotes the bottom ruthenium layer, 14 denotes the base layer, and 15 denotes ions in the plasma, showing cross-sectional views of the wiring before and after plasma treatment.

[0007] Patent Document 1 also discloses a process for vertically etching a metal located at the bottom and embedded in a dielectric along a pattern structure of the metal located at the top (FIG. 2), in which 21 denotes a mask, 22 denotes a ruthenium pattern located at the top, 23 denotes an insulating layer, 24 denotes an underlayer, and 25 denotes a ruthenium layer located at the bottom, and shows cross-sectional views of a wiring before and after plasma treatment.

[0008] However, in the etching process of the ruthenium layers 13, 25 located at the bottom as shown in Figures 1 and 2, the ruthenium patterns 11, 22 located at the top are also irradiated with plasma, causing side etching, as shown in Figures 3 and 4. Furthermore, the electrical conductivity of the ruthenium layers 13, 25 located at the bottom is reduced due to etching residues in the pattern grooves of the ruthenium layers 13, 25 located at the bottom and the influence of the tapered shape. Reference numeral 16 in Figure 3 and 26 in Figure 4 indicate residues generated in the pattern grooves of the ruthenium layers 13, 25 located at the bottom.

[0009] The present invention provides a technique that can suppress side etching of the upper ruthenium layer, remove residues of the lower ruthenium layer, and vertically process the lower ruthenium layer while improving the verticality of the pattern. Other objects and novel features are described in the present specification and the accompanying drawings.

[0010] A plasma processing method according to one embodiment of the present invention, in which a metal film formed below a metal wiring pattern is plasma-etched using the metal wiring pattern, comprises: a first step of forming a protective film on the metal wiring pattern by plasma generated using a first gas; a second step of etching the metal film by plasma generated using a second gas after the first step; a third step of etching the metal film after the second step by plasma generated using a third gas so that the etched shape of the metal film becomes vertical after the second step; and a fourth step of removing the protective film formed on the metal wiring pattern by plasma generated using a fourth gas, and the second and third steps are repeated until the etching depth of the metal film reaches a predetermined depth.

[0011] According to the plasma processing method of the present invention, side etching and surface damage to the sidewalls of the upper ruthenium layer can be suppressed during the etching process of the bottom ruthenium layer. Furthermore, the verticality of the pattern grooves of the bottom ruthenium layer can be improved, and residues can be removed. These processes are expected to improve the electrical conductivity of each patterned ruthenium wiring layer. As a result, vertical ruthenium wiring layers with precisely controlled pattern dimensions can be produced with a minimum number of processes and at high throughput.

[0012] 1 is an explanatory diagram for explaining the structure of ruthenium wiring obtained by a conventional method; and FIG. 2 is an explanatory diagram for explaining the structure of ruthenium wiring obtained by another conventional method. FIG. 3 is an explanatory diagram showing the problems of ruthenium wiring obtained by a conventional method; and FIG. 4 is an explanatory diagram showing the problems of the structure of ruthenium wiring obtained by another conventional method. FIG. 4 is an explanatory diagram showing an example of the internal structure of a plasma processing apparatus (apparatus A) of this embodiment. FIG. 5 is an explanatory diagram showing an example of the internal structure of a plasma processing apparatus (apparatus B) of this embodiment. FIG. 6 is a process flow diagram for when protection is performed with a modified film using apparatus A in this embodiment. FIG. 7 is an explanatory diagram for when protection is performed with a modified film using apparatus B in this embodiment. FIG. 8 is an explanatory diagram for when protection is performed with a modified film using apparatus B in this embodiment. FIG. 9 is an explanatory diagram for when protection is performed with a modified film using apparatus B in this embodiment. FIG. 10 is a diagram showing the etching rate of ruthenium according to the flow rate ratio of oxygen and chlorine. FIG. 11 is a diagram showing an example of a ruthenium compound expected to be generated by ruthenium etching, and its melting point and boiling point. FIG. 12 is a process flow diagram for when protection is performed with a deposited film using apparatus A in this embodiment. FIG. 13 is an explanatory diagram for when protection is performed with a deposited film using apparatus A in this embodiment. Fig. 1 is a process flow diagram in the case where the ruthenium layers located at the top and bottom are protected by altered films in this embodiment. Fig. 2 is an explanatory diagram of a process flow in the case where the ruthenium layers located at the top and bottom are protected by altered films in this embodiment. Fig. 3 is an explanatory diagram of a process flow in the case where the ruthenium layers located at the top and bottom are protected by altered films in this embodiment. Fig. 4 is an explanatory diagram of a process flow in which this embodiment is applied to the structure of ruthenium wiring shown in Fig. 2. Fig. 5 is an explanatory diagram of a process flow in which this embodiment is applied to another ruthenium wiring structure.

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all drawings, components having the same function are designated by the same reference numerals, and repeated explanations thereof may be omitted. In addition, the drawings may be more schematic than the actual embodiment in order to clarify the explanation, but they are merely examples and do not limit the interpretation of the present disclosure.

[0014] 5 and 6 are explanatory diagrams showing an example of the internal structure of the plasma processing apparatus of this embodiment. The etching of this embodiment can be performed by, for example, a microwave-electron cyclotron resonance (M-ECR) plasma etcher as the plasma processing apparatus.

[0015] 5 shows a configuration diagram of a plasma processing apparatus (hereinafter referred to as apparatus A). Apparatus A is equipped with an electromagnetic coil 101 for generating plasma, a microwave source 103, a circular waveguide 102, and a housing 105. Plasma 104 generated from an etchant gas contains radicals 111 and ions 112, and is irradiated onto a ruthenium laminated wiring formed on the main surface (surface) of a semiconductor wafer (also referred to as a substrate) 113 as a sample placed on a temperature control stage 114, which serves as a sample holder. A bias power supply 115 is connected to the temperature control stage 114, and the incident energy of the ions 112 used in etching can be adjusted by controlling the applied bias.

[0016] 6A and 6B are explanatory diagrams of another example of the internal structure of the plasma processing apparatus of this embodiment, where (a) shows a case where the ECR surface where plasma is generated is located below the ion shielding plate, and (b) shows a case where the ECR surface where plasma is generated is located above the ion shielding plate. Fig. 6 also shows a configuration diagram of another plasma processing apparatus (hereinafter referred to as apparatus B). In apparatus B, in addition to apparatus A of Fig. 5, an ion shielding plate 106 is installed inside a housing 105. The ion shielding plate 106 has the property of allowing radicals 111 in the plasma 104 to pass through but not allowing ions 112 to pass through.

[0017] Therefore, when the ECR surface on which the plasma 104 is formed is located below the ion shielding plate 106 (FIG. 6(a)), the ruthenium film formed on the main surface (surface) of the substrate 113 is irradiated with the plasma gas containing radicals 111 and ions 112, as in the apparatus A of FIG. 5. On the other hand, when the ECR surface on which the plasma 104 is formed is located above the ion shielding plate 106 (FIG. 6(b)), the plasma gas containing a large amount of radicals 111 that have passed through the ion shielding plate 106 is irradiated with the ruthenium film formed on the main surface (surface) of the substrate 113. In other words, by controlling the height of the plasma 104 generation region, it is possible to easily switch between a mode in which the radicals 111 and ions 112 contained in the plasma 104 are anisotropically irradiated and a mode in which the radicals 111 are isotropically irradiated (second etching mode: radical irradiation) within the same chamber.

[0018] 7, 8, 9, and 10 are flowcharts and explanatory diagrams of a method for etching ruthenium multilayer wiring, illustrating a case where the ruthenium pattern located at the top is protected by a protective film of an altered film. Also, FIGS. 7 and 8 illustrate a case where the apparatus A in FIG. 5 is used, and FIGS. 9 and 10 illustrate a case where the apparatus B in FIG. 6 is used.

[0019] 7 to 10, an etching method will be described in which a protective film is formed using a modified film and a gas containing oxygen and chlorine is used as the gas for ruthenium etching. The ruthenium patterns 31, 131 located at the top, which have been pre-patterned via masks 30, 130, are partially connected to the ruthenium layers 33, 133 located at the bottom, with the remaining regions insulated via insulating layers 32, 132. Examples of materials that can be used for the masks 30, 130 here include silicon oxide, silicon nitride, and titanium nitride, which have a low etching selectivity relative to the ruthenium 31, 131. The laminated wiring is formed on an underlayer 34, 134, such as silicon.

[0020] 11 is a graph showing the dependency of the etching rate of a ruthenium film on the gas mixture ratio when etching is performed with plasma using a mixed gas of oxygen and chlorine using the apparatus B. The vertical axis represents the etching rate (nm / min), and the horizontal axis represents the gas mixture ratio of the mixed gas of oxygen and chlorine (O ２ / (Cl ２ +O ２ ) %)%. In FIG. 11, the black circles indicate plasma irradiation (first etching mode), and the black squares indicate radical irradiation (second etching mode). In both etching modes, it can be confirmed that the etching rate of the ruthenium film is maximized by adding a small amount of chlorine (10-20%). Generally, dry etching proceeds by chemically converting the material to be etched into volatile compounds with low boiling points, and etching stops when the material is converted into non-volatile products.

[0021] FIG. 12 shows an example of a ruthenium compound produced by a chemical reaction between ruthenium and a plasma gas containing oxygen and chlorine, and its melting point (°C) and boiling point (°C). ２ ) has a melting point of 1300°C or higher and is nonvolatile, and is expected to be formed as an intermediate in the etching reaction. RuO ４ has a low boiling point and is volatile. In other words, the oxidation reaction rate of ruthenium increases due to the addition of a small amount of chlorine, and RuO ４ and ruthenium oxychloride (RuCl ｘ O ｙ It is expected that etching proceeds as a result of the formation of volatile ruthenium compounds such as ruthenium fluoride.

[0022] On the other hand, from Figure 11, it can be seen that when the flow rate ratio of chlorine gas increases above 20%, the etching rate of ruthenium decreases, and when the flow rate ratio of chlorine gas is close to 100%, etching hardly progresses. This is because when chlorine plasma is irradiated onto the surface of ruthenium, non-volatile ruthenium chloride (RuCl) with a melting point of 500°C or higher is formed. ３) is generated. In other words, when a plasma gas containing a large amount of chlorine is irradiated onto a ruthenium surface, a nonvolatile film is formed on the ruthenium surface, which is thought to inhibit the etching reaction of ruthenium. In the examples of Figures 7 to 10, this nonvolatile ruthenium film is used as a sidewall protection film for pattern etching.

[0023] First, an example of a pattern etching method using apparatus A and protecting the ruthenium pattern 31 located in the upper part with an altered film 35 will be described (see FIGS. 5, 7, and 8). In FIG. 8, the diagrams at the ends of the arrows S31, S32, S33, S34, and S35 correspond to the cross-sectional views after the respective steps (S31, S32, S33, S34, and S35) in FIG. 7.

[0024] In a wiring structure in which the upper ruthenium pattern 31 has been pre-etched, in the first step (S31: forming a protective film), the sidewalls of the upper ruthenium pattern 31 are irradiated with plasma gas containing a large amount of chlorine, thereby protecting the pattern with an altered film 35 derived from ruthenium chloride. At this time, the plasma contains both ions and radicals, and the altered film 35 is formed on the entire surface of the ruthenium that comes into contact with it. Therefore, the altered film 35 is formed not only on the sidewalls of the upper ruthenium pattern 31, but also on the portion of the ruthenium layer 33 at the bottom that is exposed to the plasma interface. Note that in this step, a gas containing sulfur (SO ) instead of chlorine is used. ２ When irradiating plasma generated from a gas containing nitrogen (N ２ When irradiating the plasma generated from the gases, ruthenium nitride is formed as the altered film 35, and therefore, these gases may be used.

[0025] In the second step (S32: vertical processing of the bottom ruthenium layer), the bottom ruthenium layer 33 is processed vertically by ions 36. The bias of the high-frequency power applied to the substrate 113 from the bias power supply 115 via the temperature adjustment stage 114 is set to a value large enough to pass through the altered layer 35 on the surface of the bottom ruthenium layer 33, and a mixed gas with an oxygen / chlorine flow ratio of approximately 80%:20% is used. In this step, in order to etch the ruthenium pattern 31 vertically, it is desirable to apply a high bias as the power value of the high-frequency power supplied to the temperature adjustment stage 114 and then irradiate the plasma gas onto the substrate 113. Furthermore, the power value of the high-frequency power applied to the substrate 113 via the temperature adjustment stage 114 is set to a power value necessary to sputter and remove the altered film 35 formed on the surface of the bottom ruthenium layer 33.

[0026] In the third step (S33: taper angle adjustment), plasma gas generated from a gas containing oxygen and chlorine is used to etch the pattern grooves in the ruthenium layer 33 located at the bottom in the horizontal direction, thereby adjusting the pattern shape so that it becomes vertical. Since the horizontal etching is caused by a chemical reaction by radicals, it is desirable to set the applied bias in this step to zero or a low bias. In addition, the substrate temperature may be adjusted using the temperature adjustment stage 114 to control the rate of the chemical reaction by radicals. In this step, the etching conditions are adjusted so that the dimensions of the pattern grooves become the desired dimensions.

[0027] In the fourth step (S34: residue removal), plasma gas generated from a gas containing oxygen and chlorine is irradiated to remove residue 37 from the pattern grooves of ruthenium 33 located at the bottom. Since the fourth step also proceeds through a chemical reaction caused by radicals, it is desirable to set the applied bias to zero or a low bias. Since the main component of residue 37 is expected to be ruthenium, it is thought that it can be removed by etching using radicals derived from oxygen and chlorine. In addition, the substrate temperature may be adjusted using a temperature adjustment stage 114 to control the rate of the chemical reaction caused by radicals.

[0028] Thereafter, the second to fourth steps are repeated until the ruthenium layer 33 located at the bottom reaches the predetermined pattern groove depth. If the ruthenium layer 33 located at the bottom reaches the predetermined pattern groove depth after the fourth step (S34), the process proceeds to the fifth step (S35).

[0029] In the fifth step (S35: reduction and removal of the altered film), the altered film 35 is reduced to return the surface of the ruthenium pattern 31 located thereon to metallic ruthenium by irradiating it with a reducing gas or a plasma gas derived from a reducing gas. For example, hydrogen radicals (H ＊ ) is irradiated onto ruthenium chloride to form RuCl ３ +3H ＊ The reaction of Ru + 3HCl occurs, and the altered film 35 on the pattern surface can be reduced to metallic ruthenium. In other words, the fifth step (S35) is a step of reducing the ruthenium compound to metallic ruthenium after the fourth step (S34). When the fifth step (S35) is completed, the pattern etching of the ruthenium layer 33 located at the bottom is completed (S36).

[0030] An advantageous feature of this embodiment is the first step (S31) of forming a protective film of the altered film 35 on the upper ruthenium pattern 31 of the two-layer ruthenium wiring. If this step is not applied and the bottom ruthenium layer 33 is vertically processed, both the upper ruthenium pattern 31 and the bottom ruthenium layer 33 are exposed to plasma. As a result, there is a concern that the sidewalls of the upper ruthenium pattern 31 may be etched, resulting in an unintended pattern shape. By applying this step, the sidewalls of the upper ruthenium pattern 31 are protected by the altered film 35 and are not exposed to the etching gas, thereby suppressing etching of the sidewalls of the upper ruthenium pattern 31. Although the altered film 35 is also formed on the surface of the bottom ruthenium layer 33, the bottom ruthenium layer 33 is vertically etched in the second step (S32), and the altered film 35 can be removed by physical sputtering due to ion collisions. Therefore, the ruthenium layer 33 located at the bottom can be selectively processed vertically while protecting the sidewalls of the ruthenium pattern 31 located at the top.

[0031] The process of this embodiment includes a step of isotropically forming an altered layer 35 on the pattern surface (S31), a step of adjusting the pattern dimensions (S33), a step of removing residue (S34), and a step of forming a pattern by anisotropic etching (S32). Therefore, by using the apparatus B, these steps can be performed in the same chamber. The following describes the steps of using the apparatus B and protecting the upper ruthenium pattern 131 with an altered film 135 (see FIGS. 6, 9, and 10). In FIG. 10, the arrows at the ends of S131, S132, S133, S134, and S135 correspond to the cross-sectional views of FIG. 9 after the respective steps (S131, S132, S133, S134, and S135).

[0032] The apparatus B is characterized in that it can process the bottom ruthenium layer 133 by using the first etching mode and the second etching mode complementarily. The process using a gas containing oxygen and chlorine will be described below. When using the first etching mode and the second etching mode, the applied bias and the substrate temperature may be adjusted to optimize the pattern shape.

[0033] In the first step (S131: forming a protective film), a gas containing chlorine as a main component is used to generate plasma in the second etching mode, thereby irradiating the surface with plasma containing a large amount of chlorine radicals. By applying this method, surface damage caused by ion collisions can be suppressed more effectively than in the corresponding step (S31) of the apparatus A, which irradiates both ions and radicals, and the ruthenium chloride-based altered film 135 can be formed more uniformly.

[0034] In the second step (S132), the first etching mode is applied to etch the bottom ruthenium layer 133 in the same manner as in the corresponding step (S32) using the device A.

[0035] In the third step (S133: taper angle adjustment), plasma is generated in the second etching mode, and the taper angle of the pattern groove in the ruthenium layer 133 located at the bottom is adjusted by isotropic etching.

[0036] In the fourth step (S134: residue removal), plasma is generated in the second etching mode, and residues 137 in the pattern grooves of the ruthenium layer 133 located at the bottom are removed by isotropic etching.

[0037] In the fifth step (S135: reduction and removal of the altered film), plasma is generated in the second etching mode, and the altered film on the surface of the upper ruthenium pattern 131 is isotropically reduced.

[0038] Next, a method will be described in which the apparatus A is used and the ruthenium pattern 41 located in the upper part is protected by a deposition film 45 (see FIGS. 13 and 14). In FIG. 14, the diagrams at the ends of the arrows S41, S42, S43, S44, and S45 correspond to the cross-sectional views after the respective steps (S41, S42, S43, S44, and S45) in FIG. 13.

[0039] In the first step (S41), a precursor gas of the deposition film 45 is irradiated to protect the ruthenium pattern 41 located at the top with the deposition film 45. For example, when a carbon-based precursor gas such as carbon dioxide or methane is irradiated, an organic deposition film is formed at the interface. When a silane-based or halide tungsten-based precursor gas is irradiated, an inorganic deposition film derived from silicon or tungsten is formed, respectively. The flow rate and pressure of the precursor gas, the irradiation time, and the substrate temperature are determined based on previously acquired data, and the deposition film 45 is formed to have an appropriate film thickness.

[0040] In the second step (S42), the third step (S43), and the fourth step (S44), the same processes as those in the corresponding process flows (S32, S33, S44) shown in FIG. 7 are carried out.

[0041] In the fifth step (S45), the deposition film 45 remaining on the ruthenium pattern 41 is removed by plasma treatment. If the deposition film 45 is organic, it can be removed by ashing with a plasma gas containing oxygen, for example. If the deposition film 45 is silicon-based or metal-based, it can be removed by irradiating it with a plasma gas (e.g., a gas mainly containing a halogen-based gas) that generates a volatile silicon compound or a volatile metal compound.

[0042] Next, a plasma processing method will be described in which the pattern shape can be more accurately controlled by adding a step (S151) of forming a protective film in the pattern grooves of the ruthenium layer 53 located at the bottom (see FIGS. 15 and 16). In FIG. 16, the arrows at S51, S52, S53, S54, S151, and S55 correspond to cross-sectional views after the respective steps (S51, S52, S53, S54, S151, and S55) in FIG. 13. Furthermore, the steps (S51, S52, S53, S54, S55, and S56) shown in FIGS. 15 and 16 correspond to the steps (S31, S32, S33, S34, S35, and S36) shown in FIGS. 7 and 8.

[0043] In this plasma processing method, etching of the ruthenium layer 53 located at the bottom in the second step (S52) is stopped temporarily before bowing or surface roughness is formed, the taper angle of the pattern groove in the ruthenium layer 53 located at the bottom is corrected in the third step (S53), and the residue 57 is removed in the fourth step (S54).

[0044] Thereafter, returning to the second step (S52), before resuming etching of the bottom ruthenium layer 53, a sixth step (S151) is added in which a protective film 58 is formed in the pattern grooves of the bottom ruthenium layer 53. In this step, the protective film 58 is formed in the regions of the pattern grooves of the bottom ruthenium layer 53 that come into contact with plasma using the same method (halogenation, sulfurization, or nitridation) as that for the protective film 55 of the upper ruthenium pattern.

[0045] As described above, by repeatedly performing the second step (S52), the third step (S53), the fourth step (S54), and the sixth step (S151), it is possible to perform plasma processing while suppressing sidewall etching of the bottom ruthenium layer 53. In the fifth step (S56), the protective film 55 of the upper ruthenium pattern 51 and the protective film 58 formed on the bottom ruthenium layer 53 are reduced to metallic ruthenium using a technique similar to that of S35 in Fig. 7 .

[0046] Fig. 17 is an explanatory diagram of a process flow in which this embodiment is applied to a plasma treatment step for vertically processing the ruthenium layer 74 located at the bottom and embedded in the insulating layer 72 along the sidewalls of the pattern grooves in the ruthenium layer 71 located at the top in the ruthenium wiring structure shown in Fig. 2. The steps in Fig. 17 (S71, S72, S73, S74, S171, S75) correspond to the steps (S51, S52, S53, S54, S151, S55) described in Figs. 15 and 16, and all steps are performed in the same manner as the steps in Figs. 15 and 16.

[0047] 18 is an explanatory diagram of a process flow in which this embodiment is applied to another ruthenium wiring structure. In the ruthenium wiring structure of FIG. 18, a ruthenium pattern 81 located at the top and a ruthenium layer 82 located at the bottom are cut out from the same bulk ruthenium, and the purpose is to form ruthenium patterns of different heights by etching each in the vertical direction through a mask 80. The steps in FIG. 18 (S81, S82, S83, S84, S181, S85) correspond to the steps (S51, S52, S53, S54, S151, S55) described in FIGS. 15 and 16, and all steps are performed in the same manner as the steps in FIGS. 15 and 16.

[0048] Although the present embodiment has been described with reference to an example in which a ruthenium pattern is etched, metal materials such as molybdenum can also be plasma etched, and therefore, a similar technique can be used to process the pattern while protecting the sidewalls of the pattern.

[0049] Although the present invention has been specifically described based on the embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways without departing from the spirit of the present invention. For example, the above embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the described configurations. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0050] 10: Mask, 11: Ruthenium pattern located at the top, 12: Insulating layer, 13: Ruthenium layer located at the bottom, 14: Underlayer, 15: Ions, 16: Residue, 21: Mask, 22: Ruthenium pattern located at the top, 23: Insulating layer, 24: Underlayer, 25: Ruthenium layer located at the bottom, 26: Residue, 101: Electromagnetic coil, 102: Circular waveguide, 103: Microwave source, 104: Plasma, 105: Housing, 10 6: ion shielding plate, 111: radicals, 112: ions, 113: substrate, 114: temperature adjustment stage, 115: bias power supply, 30: mask, 31: ruthenium pattern located at the top, 32: insulating layer, 33: ruthenium layer located at the bottom, 34: underlayer, 35: altered film, 36: ions, 37: residue, 130: mask, 131: ruthenium pattern located at the top, 132: insulating layer, 133: bottom ruthenium layer located at the top, 134: underlayer, 135: altered film, 136: ions, 137: residue, 40: mask, 41: ruthenium pattern located at the top, 42: insulating layer, 43: ruthenium layer located at the bottom, 44: underlayer, 45: deposited film, 46: ions, 47: residue, 50: mask, 51: ruthenium pattern located at the top, 52: insulating layer, 53: ruthenium layer located at the bottom, 54: underlayer, 55: altered film Film, 56: ions, 57: residue, 58: altered film, 70: mask, 71: ruthenium pattern located on top, 72: insulating layer, 73: underlayer, 74: ruthenium layer located on the bottom, 75: altered film, 76: ions, 77: residue, 78: altered film, 80: mask, 81: ruthenium pattern located on top, 82: ruthenium layer located on the bottom, 83: underlayer, 84: altered film, 85: ions, 86: residue, 87: altered film.

Claims

1. A plasma processing method for plasma etching a metal film formed below a metal wiring pattern using the metal wiring pattern, comprising: a first step of forming a protective film on the metal wiring pattern with plasma generated using a first gas; a second step of etching the metal film with plasma generated using a second gas after the first step; a third step of etching the metal film after the second step with plasma generated using a third gas so that the etched shape of the metal film becomes a vertical shape after the second step; and a fourth step of removing the protective film formed on the metal wiring pattern with plasma generated using a fourth gas, characterized in that the second step and the third step are repeated until the etching depth of the metal film reaches a predetermined depth.

2. The plasma processing method according to claim 1, wherein the metal film is a ruthenium film or a molybdenum film.

3. A plasma processing method according to claim 1 or 2, wherein the protective film is a modified film, and the modified film is formed by plasma generated using a gas that produces a non-volatile compound containing a metal element.

4. The plasma processing method according to claim 3, wherein the non-volatile compound is a nitrided compound, a sulfurized compound or a halogenated compound.

5. A plasma processing method according to claim 1 or 2, characterized in that the protective film is formed by plasma generated using a precursor gas containing a carbon element, a silicon element or a metal element.

6. A plasma processing method according to claim 1 or 2, characterized in that the metal film after the second step is etched using radicals generated by the plasma in the third step.

7. The plasma processing method according to claim 1 or 2, further comprising the step of removing residues on the metal film.

8. The plasma processing method according to claim 1 or 2, wherein the protective film is a deteriorated film, and the fourth step comprises removing the deteriorated film by a reduction treatment.

9. The plasma processing method according to claim 1, wherein the metal film is a ruthenium film, and the second gas and the third gas are mixed gases of oxygen gas and halogen gas.

10. The plasma processing method according to claim 1 or 2, wherein a portion of the metal wiring pattern is connected to the metal film.

11. A plasma processing method according to claim 1 or 2, wherein the metal film is embedded in a groove formed below the metal wiring pattern.

12. A plasma processing method according to claim 1 or 2, wherein all of the metal wiring patterns are connected to the metal film, and the second step etches the metal wiring patterns and the metal film with plasma generated using the second gas.

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