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 comprises: 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) in which, after the first step, the metal film is etched by plasma generated using a second gas; a third step (S33) in which, after the second step, the metal film after the second step is etched by plasma generated using a third gas such that the etched shape of the metal film becomes a vertical shape; and a fourth step (S35) in which the protective film formed on the metal wiring pattern is removed by plasma generated using a fourth gas until the etching depth of the metal film becomes a predetermined depth, and the second step (S32) and the third step (S33) are repeated.

Description

Technical Field

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

[0002] With the miniaturization and three-dimensionalization of semiconductor device structures, the application of alternative metals to replace copper is being studied as a wiring metal. Specifically, ruthenium that can be pattern-processed by plasma etching can be cited. The ruthenium wiring has a stacked structure, and it is necessary to appropriately perform plasma etching through a mask to process it into a pattern. By irradiating the surface of ruthenium that has been pre-mask-treated with plasma generated from a mixed gas containing oxygen gas and halogen gas, etching is performed in the vertical direction, whereby a ruthenium pattern can be fabricated. However, with the increase in the number of stacked wirings and the miniaturization of the wiring width, the wiring processing of ruthenium becomes complicated, and an increase in the number of processes is expected.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: U.S. Patent Application Publication No. 2022 / 0139823

[0006] Non-Patent Documents

[0007] Non-Patent Document 1: 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 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] Typically, wiring in devices using ruthenium is stacked on top of each other. In this specification, the stacked wiring is simplified to two layers, referred to as upper ruthenium and lower ruthenium. Researchers are investigating optimizing the processing by using the upper ruthenium pattern as a mask immediately after processing the upper ruthenium pattern to vertically etch the lower ruthenium layer.

[0010] For example, in Non-Patent Document 1, the following process is proposed: for a previously etched upper ruthenium pattern and a bottom ruthenium embedded via an insulating layer, the bottom ruthenium exposed to the plasma interface is etched in a vertical direction to insulate adjacent elements ( Figure 1 ). Here, in Figure 1 10 represents a mask, 11 represents a ruthenium pattern located at the upper portion, 12 represents an insulating layer, 13 represents a ruthenium layer located at the bottom, 14 represents a base layer, and 15 represents ions in plasma, showing a cross-sectional view of the wiring before and after plasma treatment.

[0011] In addition, Patent Document 1 discloses a process of etching the metal at the bottom embedded in the dielectric in a vertical direction along the pattern structure of the metal at the top ( Figure 2 ). Here, in Figure 2 21 denotes a mask, 22 denotes a ruthenium pattern located at the upper portion, 23 denotes an insulating layer, 24 denotes a base layer, and 25 denotes a ruthenium layer located at the bottom, showing a cross-sectional view of the wiring before and after plasma treatment.

[0012] But in Figure 1 、 Figure 2 In the etching process of the ruthenium layers 13 and 25 at the bottom as shown in FIG. Figure 3 、 Figure 4 As shown, since the ruthenium patterns 11 and 22 located at the top are also irradiated with plasma, side etching occurs. In addition, due to the etching residue and the tapered shape of the pattern grooves of the ruthenium layers 13 and 25 located at the bottom, the electrical conductivity of the ruthenium layers 13 and 25 located at the bottom is reduced. Figure 3 In the figure, 16 represents the residue generated in the pattern groove of the ruthenium layer 13 and 25 at the bottom. Figure 4 In FIG. 1 , 26 indicates residues generated in the pattern grooves of the ruthenium layers 13 and 25 located at the bottom.

[0013] The present invention provides a technique for suppressing lateral etching of the ruthenium layer located at the top, removing residue from the ruthenium layer located at the bottom, improving the verticality of the pattern, and simultaneously enabling vertical processing of the ruthenium layer located at the bottom. Other issues and novel features are described in this specification and the accompanying drawings.

[0014] Means for solving problems

[0015] A plasma processing method for plasma etching a metal film formed under a metal wiring pattern using the metal wiring pattern according to an embodiment of the present invention includes: 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 an etching shape of the metal film becomes a vertical shape; and a fourth step of removing the protective film formed on the metal wiring pattern by plasma generated using a fourth gas until an etching depth of the metal film becomes a given depth, and repeating the second step and the third step.

[0016] Effects of the Invention

[0017] According to the plasma processing method of the present invention, in the etching step of the ruthenium layer at the bottom, lateral etching and surface damage of the sidewalls of the ruthenium at the upper part can be suppressed. In addition, residues can be removed by improving the perpendicularity of the pattern grooves of the ruthenium layer at the bottom. Through the above steps, it is expected to improve the electrical conductivity of each ruthenium wiring layer formed into a pattern. As a result, a vertical ruthenium wiring layer with precisely controlled pattern dimensions can be produced with a minimum number of processes and high throughput. Description of the Drawings

[0018] Figure 1 It is an explanatory diagram for explaining the structure of a ruthenium wiring obtained by an existing method.

[0019] Figure 2 It is an explanatory diagram for explaining the structure of a ruthenium wiring obtained by another existing method.

[0020] Figure 3 It is an explanatory diagram showing the problems of a ruthenium wiring obtained by an existing method.

[0021] Figure 4 It is an explanatory diagram showing the problems of the structure of a ruthenium wiring obtained by another existing method.

[0022] Figure 5 It is an explanatory diagram showing an example of the internal structure of the plasma processing apparatus (Apparatus A) of the present embodiment.

[0023] Figure 6 It is an explanatory diagram showing an example of the internal structure of the plasma processing apparatus (Apparatus B) of the present embodiment.

[0024] Figure 7 It is a process flow diagram of a case where Apparatus A is used in the present embodiment and protected with a modified film.

[0025] Figure 8 It is an explanatory diagram of the process flow in the case of using apparatus A and protecting it with a modified film in this embodiment.

[0026] Figure 9 It is a process flow chart in the case of using apparatus B and protecting it with a modified film in this embodiment.

[0027] Figure 10 It is an explanatory diagram of the process flow in the case of using apparatus B and protecting it with a modified film in this embodiment.

[0028] Figure 11 It is a graph showing the etching rate of ruthenium corresponding to the flow rate ratio of oxygen to chlorine.

[0029] Figure 12 It is a graph showing an example of a ruthenium compound expected to be generated during ruthenium etching, its melting point, and its boiling point.

[0030] Figure 13 It is a process flow chart in the case of using apparatus A and protecting it with a deposition film in this embodiment.

[0031] Figure 14 It is an explanatory diagram of the process flow in the case of using apparatus A and protecting it with a deposition film in this embodiment.

[0032] Figure 15 It is a process flow chart in the case of protecting the ruthenium layers located at the upper and lower parts with a modified film respectively in this embodiment.

[0033] Figure 16 It is an explanatory diagram of the process flow in the case of protecting the ruthenium layers located at the upper and lower parts with a modified film respectively in this embodiment.

[0034] Figure 17 In Figure 2 It is an explanatory diagram of applying the process flow of this embodiment to the structure of the ruthenium wiring shown.

[0035] Figure 18 It is an explanatory diagram of applying the process flow of this embodiment to the structure of other ruthenium wirings. Detailed Description of the Invention

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings, elements having the same function are denoted by the same reference numerals, and redundant description thereof may be omitted. In addition, the drawings are sometimes schematically represented for clearer explanation compared to the actual mode, but this is only an example and does not limit the interpretation of the present disclosure.

[0037] Figure 5 、 Figure 6This is an explanatory diagram of an example of the internal structure of the plasma processing apparatus of the present embodiment. The etching of the present embodiment can be performed, for example, by a microwave electron cyclotron resonance (M-ECR: Microwave-Electron Cyclotron Resonance Plasma Etcher) apparatus as the plasma processing apparatus.

[0038] In Figure 5 a structural diagram of a plasma processing apparatus (hereinafter referred to as apparatus A) is shown. In apparatus A, there are provided: an electromagnetic coil 101 for generating plasma, a microwave source 103; a circular waveguide 102; and a housing 105. The plasma 104 generated from the etching 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 sample stage, i.e., a temperature control stage 114. 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 voltage.

[0039] Figure 6 This is an explanatory diagram of another example of the internal structure of the plasma processing apparatus of the present embodiment. (a) is a diagram showing the case where the ECR surface for forming plasma is located below the ion shield plate, and (b) is a diagram showing the case where the ECR surface for forming plasma is located above the ion shield plate. In Figure 6 a structural diagram of another plasma processing apparatus (hereinafter referred to as apparatus B) is shown. In apparatus B, in addition to Figure 5 apparatus A, an ion shield plate 106 is further provided inside the housing 105. The ion shield plate 106 has the property of allowing the radicals 111 in the plasma 104 to pass through and not allowing the ions 112 to pass through.

[0040] Therefore, in the case where the ECR surface for forming plasma 104 is located below the ion shield plate 106 ( Figure 6 the (a) of Figure 5 ), similar to apparatus A of Figure 6In (b)), a ruthenium film formed on the main surface (front surface) of substrate 113 is irradiated with a plasma gas containing a large amount of radicals 111 that has passed through ion shield plate 106. Specifically, by controlling the height of the region where plasma 104 is generated, it is possible to easily switch within the same chamber between a mode in which radicals 111 and ions 112 contained in plasma 104 are anisotropically irradiated (first etching mode: plasma irradiation) and a mode in which radicals 111 are isotropically irradiated (second etching mode: radical irradiation).

[0041] Figure 7 、 Figure 8 as well as Figure 9 、 Figure 10 The flowchart and its explanatory diagram of the etching method of ruthenium stacked wiring are described, which describe the situation where the ruthenium pattern located on the upper part is protected by a protective film of the modified film. Figure 7 、 Figure 8 In the Figure 5 In the case of device A, Figure 9 、 Figure 10 In the Figure 6 The case of device B.

[0042] exist Figures 7 - 10 The example of [ 1 ] describes an etching method in which a protective film is formed by modifying a film and a gas containing oxygen and chlorine is used as the gas for ruthenium etching. This method is described using a stacked wiring as an example, in which a ruthenium pattern 31, 131 located at the top, pre-patterned via a mask 30, 130, is partially connected to a ruthenium layer 33, 133 located at the bottom, while the remaining area is insulated via an insulating layer 32, 132. Materials such as silicon oxide, silicon nitride, and titanium nitride, which have a low etching selectivity with respect to ruthenium 31, 131, can be used for the mask 30, 130. This stacked wiring is formed on a base layer 34, 134 made of silicon or the like.

[0043] Figure 11 This is a graph illustrating the gas mixture ratio dependency of the ruthenium film etching rate when etching is performed using plasma of a mixed gas of oxygen and chlorine using 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 (O2 / (Cl2+O2)). Figure 11 In the figure, black circles represent plasma irradiation (first etching mode), and black squares represent radical irradiation (second etching mode). In both etching modes, it was confirmed that the ruthenium film etching rate was maximized by adding a small amount (10-20%) of chlorine. Generally, dry etching progresses when the etched material is converted into a low-boiling-point volatile compound through a chemical reaction, and etching stops when it is converted into a non-volatile product.

[0044] exist Figure 12Shows an example of a ruthenium compound generated in the chemical reaction of a plasma gas containing oxygen and chlorine with ruthenium, its melting point (°C), and boiling point (°C). Ruthenium dioxide (RuO2) has a melting point of 1300 °C or higher and is non-volatile, and is expected to form an intermediate of the etching reaction. Furthermore, RuO4 formed by the progress of oxidation has a low boiling point and is volatile. That is, the oxidation reaction rate of ruthenium increases by the addition of a small amount of chlorine, and volatile ruthenium compounds such as RuO4 and ruthenium oxychloride (RuCl x O y ), as a result, etching is expected to progress.

[0045] On the other hand, from Figure 11 it can be confirmed that if the flow rate ratio of chlorine increases to more than 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 on the ruthenium surface, non-volatile ruthenium chloride (RuCl3) with a melting point of 500 °C or higher is generated. That is, when a large amount of plasma gas containing chlorine is irradiated on the ruthenium surface, a non-volatile film is formed on the ruthenium surface, and it is considered that the etching reaction of ruthenium is hindered. In Figures 7 - 10 the example, this non-volatile ruthenium film is used as a sidewall protective film for pattern etching.

[0046] First, an example of a pattern etching method using apparatus A and protecting the upper ruthenium pattern 31 with the modified film 35 is described (see Figure 5 , Figure 7 , Figure 8 ). In Figure 8 , the figures in front of the arrows of S31, S32, S33, S34, and S35 correspond to the cross-sectional views after the respective processes (S31, S32, S33, S34, S35) of Figure 7 .

[0047] In a wiring structure in which the upper ruthenium pattern 31 has been pre-etched, in the first process (S31: protective film formation), the sidewalls of the upper ruthenium pattern 31 are irradiated with a large amount of chlorine-containing plasma gas to protect it with the modified film 35 derived from ruthenium chloride. At this time, the plasma contains both ions and radicals, and the modified film 35 is formed on the entire ruthenium surface in contact. Therefore, the modified film 35 is formed not only on the sidewalls of the upper ruthenium pattern 31 but also on the portions of the ruthenium layer 33 at the bottom that are exposed to the plasma interface. In addition, when plasma generated from a gas containing sulfur instead of chlorine (such as SO2) is irradiated in this process, ruthenium sulfide is formed as the modified film 35, and when plasma generated from a nitrogen-containing gas (such as N2) is irradiated, ruthenium nitride is generated as the modified film 35. Therefore, these gases can be used.

[0048] 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 voltage of the high-frequency power applied to the substrate 113 from the bias power supply 115 via the temperature control stage 114 is set high enough to pass through the modified layer 35 on the surface of the bottom ruthenium layer 33. A mixed gas with a flow ratio of oxygen and chlorine of approximately 80% to 20% is used. In this step, in order to etch the ruthenium pattern 31 vertically, it is desirable to apply a high bias voltage as the power value of the high-frequency power supplied to the temperature control stage 114 before irradiating the substrate 113 with plasma gas. Furthermore, the power value of the high-frequency power applied to the substrate 113 via the temperature control stage 114 is set to the power value required to sputter and remove the modified film 35 formed on the surface of the bottom ruthenium layer 33.

[0049] In the third step (S33: Taper Angle Adjustment), plasma gas generated from a gas containing oxygen and chlorine is used to horizontally etch the pattern grooves in the bottom ruthenium layer 33, thereby adjusting the pattern shape to a vertical position. Since horizontal etching is caused by a chemical reaction based on free radicals, it is desirable to set the applied bias voltage in this step to zero or a low bias voltage. Furthermore, the substrate temperature can be adjusted on the temperature control stage 114 to control the rate of the chemical reaction based on free radicals. In this step, etching conditions are adjusted to achieve the desired dimensions of the pattern grooves.

[0050] In the fourth step (S34: residue removal), plasma gas generated from a gas containing oxygen and chlorine is irradiated to remove residue 37 located at the bottom of the ruthenium pattern groove 33. This fourth step also proceeds through a chemical reaction based on free radicals, so it is desirable to set the applied bias voltage to zero or a low bias voltage. Since the residue 37 is expected to be primarily composed of ruthenium, it is conceivable that it can be removed by etching using free radicals derived from oxygen and chlorine. Furthermore, the substrate temperature can be adjusted on the temperature control stage 114 to control the rate of the free radical chemical reaction.

[0051] Thereafter, the second to fourth steps are repeated until the ruthenium layer 33 at the bottom reaches the predetermined pattern groove depth. If the ruthenium layer 33 at the bottom reaches the predetermined pattern groove depth after the fourth step (S34), the process proceeds to the fifth step (S35).

[0052] In the fifth step (S35: reduction and removal of the modified film), in order to restore the surface of the ruthenium pattern 31 located on the upper portion to metallic ruthenium by reducing the modified film 35, a reducing gas or a plasma gas derived from a reducing gas is irradiated. For example, when ruthenium chloride is irradiated with hydrogen radicals (H * ), which causes RuCl3+3H *→The reaction of Ru + 3HCl, thus, can reduce the modified film 35 on the pattern surface to metallic ruthenium. That is, the fifth process (S35) is a process of reducing the ruthenium compound to metallic ruthenium after the fourth process (S34). If the fifth process (S35) is completed, the pattern etching of the ruthenium layer 33 at the bottom ends (S36).

[0053] The advantageous feature of this embodiment lies in the first process (S31) of forming a protective film of the modified film 35 on the upper ruthenium pattern 31 among the two-layer ruthenium wirings in the stack. In the case of vertically processing the ruthenium layer 33 at the bottom without using this process, both the upper ruthenium pattern 31 and the ruthenium layer 33 at the bottom are exposed to the plasma. As a result, the sidewalls of the upper ruthenium pattern 31 will be etched, and it may become an unexpected pattern shape. If this process is used, since the sidewalls of the upper ruthenium pattern 31 are protected by the modified film 35 and are not exposed to the etching gas, the etching of the sidewalls of the upper ruthenium pattern 31 can be suppressed. Although the modified film 35 is also formed on the surface of the ruthenium layer 33 at the bottom, since the ruthenium layer 33 at the bottom is etched in the vertical direction in the second process (S32), this modified film 35 can be removed by physical sputtering based on ion collision. Therefore, while protecting the sidewalls of the upper ruthenium pattern 31, the ruthenium layer 33 at the bottom can be selectively vertically processed.

[0054] Since the processes in this embodiment include a process (S31) of isotropically forming the modified layer 35 on the pattern surface, a process (S33) of adjusting the pattern size, residue removal (S34), and a pattern forming process (S32) based on anisotropic etching, if apparatus B is used, these processes can be performed in the same chamber. Hereinafter, the process of using apparatus B and protecting the upper ruthenium pattern 131 with the modified film 135 is described (refer to Figure 6 , Figure 9 , Figure 10 ). In Figure 10 , the figures in front of the respective arrows of S131, S132, S133, S134, S135 correspond to the cross-sectional views after the respective processes (S131, S132, S133, S134, S135) of Figure 9 .

[0055] In apparatus B, it is characterized in that while complementarily using the first etching mode and the second etching mode, the ruthenium layer 133 at the bottom can be processed. Hereinafter, the process using a gas containing oxygen and chlorine is described. In addition, when applying the first etching mode and the second etching mode, the applied bias voltage and the substrate temperature can be adjusted to optimize the pattern shape.

[0056] In the process of forming the modified film 135 in the first process (S131: protective film formation), a large amount of plasma containing chlorine radicals is isotropically irradiated by generating plasma in the second etching mode using a gas mainly composed of chlorine. By using this method, compared with the corresponding process (S31) method of apparatus A that irradiates both ions and radicals, surface damage based on ion collision can be suppressed, and the ruthenium chloride-based modified film 135 can be formed uniformly.

[0057] In the second process (S132), the ruthenium layer 133 at the bottom is etched in the first etching mode in the same manner as the corresponding process (S32) using apparatus A.

[0058] In the third process (S133: tapered angle adjustment), plasma is generated in the second etching mode, and the tapered angle of the pattern groove of the ruthenium layer 133 at the bottom is adjusted by isotropic etching.

[0059] In the fourth process (S134: residue removal), plasma is generated in the second etching mode, and the residue 137 in the pattern groove of the ruthenium layer 133 at the bottom is removed by isotropic etching.

[0060] In the fifth process (S135: reduction and removal of the modified film), plasma is generated in the second etching mode, and the modified film on the surface of the ruthenium pattern 131 at the upper part is isotropically reduced.

[0061] Next, the method of using apparatus A and protecting the ruthenium pattern 41 at the upper part with the deposited film 45 is described (see Figure 13 , Figure 14 ). In Figure 14 , the diagrams in front of the respective arrows of S41, S42, S43, S44, and S45 correspond to the cross-sectional views after the respective processes (S41, S42, S43, S44, S45) of Figure 13 .

[0062] In the first process (S41), a precursor gas of the deposited film 45 is irradiated to protect the ruthenium pattern 41 at the upper part with the deposited film 45. For example, in the case of irradiating a carbon-based precursor gas such as carbon dioxide or methane, an organic deposited film is formed at the interface. In addition, in the case of irradiating a silane-based or tungsten halide-based precursor gas, an inorganic deposited film derived from silicon or tungsten is formed respectively. The flow rate, pressure, irradiation time, and substrate temperature of the precursor gas are determined based on previously obtained data, and the deposited film 45 is formed to have an appropriate film thickness.

[0063] In the second process (S42), the third process (S43), and the fourth process (S44), in the same manner as Figure 7The above-described corresponding process flows (S32, S33, S44) are processed by the same process.

[0064] In the fifth process (S45), the deposited film 45 remaining on the ruthenium pattern 41 is removed by plasma treatment. When the deposited film 45 is organic, for example, it can be removed by ashing with an oxygen-containing plasma gas. When the deposited film 45 is silicon-based or metal-based, it is removed by irradiating a plasma gas that generates volatile silicon compounds and volatile metal compounds (for example, a gas mainly composed of a halogen-based gas).

[0065] Next, a plasma treatment method for more accurately controlling the pattern shape by adding a process (S151) of forming a protective film in the pattern groove of the ruthenium layer 53 at the bottom is described (refer to Figure 15 , Figure 16 ). In Figure 16 , the diagrams in front of the arrows of each of S51, S52, S53, S54, S151, and S55 correspond to the cross-sectional views after the respective processes (S51, S52, S53, S54, S151, S55) of Figure 13 . In addition, Figure 15 , Figure 16 The respective processes (S51, S52, S53, S54, S55, S56) shown correspond to the respective processes (S31, S32, S33, S34, S35, S36) shown in Figure 7 , 8 .

[0066] In this plasma treatment method, the etching of the ruthenium layer 53 at the bottom in the second process (S52) is temporarily stopped before forming the bowing and surface roughness. In the third process (S53), the tapered angle of the pattern groove of the ruthenium layer 53 at the bottom is corrected, and in the fourth process (S54), the residue 57 is removed.

[0067] After that, return to the second process (S52), and before restarting the etching of the ruthenium layer 53 at the bottom, add a sixth process (S151) of forming a protective film 58 in the pattern groove of the ruthenium layer 53 at the bottom. In this process, in the area of the pattern groove of the ruthenium layer 53 at the bottom that contacts the plasma, a protective film 58 is formed by the same method (halogenation, sulfidation, or nitridation) as the protective film 55 of the ruthenium pattern on the upper part.

[0068] As described above, by repeatedly executing the second process (S52), the third process (S53), the fourth process (S54), and the sixth process (S151), plasma treatment can be performed while suppressing the sidewall etching of the ruthenium layer 53 at the bottom. In the fifth process (S56), the same method as Figure 7Using the same method as in S35, the protective film 55 of the ruthenium pattern 51 located in the upper part and the protective film 58 formed on the ruthenium layer 53 located at the bottom are reduced to metallic ruthenium.

[0069] In Figure 17 shows an explanatory diagram of the process flow of this embodiment applied to the plasma processing step of vertically processing and embedding the ruthenium layer 74 at the bottom into the insulating layer 72 along the side wall of the pattern groove of the ruthenium layer 71 located in the upper part in the structure of the ruthenium wiring shown in Figure 2 . Figure 17 Each process (S71, S72, S73, S74, S171, S75) in Figure 15 and Figure 16 corresponds to each process (S51, S52, S53, S54, S151, S55) described in Figure 15 and 16 , and any process is implemented in the same manner as each process in

[0070] In Figure 18 shows an explanatory diagram of the process flow of this embodiment applied to other ruthenium wiring structures. In Figure 18 in the ruthenium wiring structure, the purpose is to cut out the ruthenium pattern 81 located in the upper part and the ruthenium layer 82 located at the bottom from the same bulk ruthenium, and etch them vertically through the mask 80 respectively, thereby forming ruthenium patterns with different heights. Figure 18 Each process (S81, S82, S83, S84, S181, S85) in Figure 15 and Figure 16 corresponds to each process (S51, S52, S53, S54, S151, S55) described in Figure 15 and 16 , and any process is implemented in the same manner as each process in

[0071] In addition, although this embodiment describes an example of etching a ruthenium pattern, for metal materials such as molybdenum, plasma etching can also be performed. Therefore, the sidewall protection of the pattern can be implemented using the same method to process the pattern.

[0072] As described above, the present invention has been specifically described based on the embodiments. However, it is self-evident that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof. For example, the above-described embodiments have been described in detail for easy understanding of the present invention and are not necessarily limited to having all the structures described. In addition, additions, deletions, and replacements of other structures can be made to a part of the structure of each embodiment.

[0073] Explanation of reference numerals

[0074] 10: Mask, 11: Upper ruthenium pattern, 12: Insulating layer, 13: Bottom ruthenium layer, 14: Substrate layer, 15: Ion, 16: Residue, 21: Mask, 22: Upper ruthenium pattern, 23: Insulating layer, 24: Substrate layer, 25: Bottom ruthenium layer, 26: Residue, 101: Electromagnetic coil, 102: Circular waveguide, 103: Microwave source, 104: Plasma, 105: Outer shell, 106: Ion shielding plate, 111: Radical, 112: Ion, 113: Substrate, 114: Temperature control stage, 115: Bias power supply, 30: Mask, 31: Upper ruthenium pattern, 32: Insulating layer, 33: Bottom ruthenium layer, 34: Substrate layer, 35: Modified film, 36: Ion, 37: Residue, 130: Mask, 131: Upper ruthenium pattern, 132: Insulating layer, 133: Bottom ruthenium layer, 134: Substrate layer, 135: Modified film, 136: Ion, 137: Residue, 40: Mask, 41: Upper ruthenium pattern, 42: Insulating layer, 43: Bottom ruthenium layer, 44: Substrate layer, 45: Deposited film, 46: Ion, 47: Residue, 50: Mask, 51: Upper ruthenium pattern, 52: Insulating layer, 53: Bottom ruthenium layer, 54: Substrate layer, 55: Modified film, 56: Ion, 57: Residue, 58: Modified film, 70: Mask, 71: Upper ruthenium pattern, 72: Insulating layer, 73: Substrate layer, 74: Bottom ruthenium layer, 75: Modified film, 76: Ion, 77: Residue, 78: Modified film, 80: Mask, 81: Upper ruthenium pattern, 82: Bottom ruthenium layer, 83: Substrate layer, 84: Modified film, 85: Ion, 86: Residue, 87: Modified film.

Claims

1. A plasma processing method, which uses the metal wiring pattern to perform plasma etching on a metal film formed under the metal wiring pattern. The plasma processing method is characterized by comprising: A first step of forming a protective film on the metal wiring pattern by using plasma generated from a first gas; A second step of etching the metal film by using plasma generated from a second gas after the first step; A third step of etching the metal film after the second step by using plasma generated from a third gas so that the etching shape of the metal film becomes a vertical shape; And A fourth step of removing the protective film formed on the metal wiring pattern by using plasma generated from a fourth gas, The second step and the third step are repeated until the etching depth of the metal film reaches a given depth.

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

3. The plasma processing method according to claim 1 or 2, wherein The protective film is a modified film, The modified film is formed by using plasma generated from a gas that generates 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 sulfided compound or a halogenated compound.

5. The plasma processing method according to claim 1 or 2, wherein The protective film is formed by using plasma generated from a precursor gas containing a carbon element, a silicon element or a metal element.

6. The plasma processing method according to claim 1 or 2, wherein The metal film after the second step is etched by using radicals generated from the plasma of the third step.

7. The plasma processing method according to claim 1 or 2, wherein The plasma processing method further has a 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 modified film, The fourth step removes the modified film by a reduction treatment.

9. The plasma processing method according to claim 1, wherein The metal film is a ruthenium film, 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 part of the metal wiring pattern is connected to the metal film.

11. The plasma processing method according to claim 1 or 2, wherein The metal film is buried in a groove formed under the metal wiring pattern.

12. The plasma processing method according to claim 1 or 2, wherein The entire metal wiring pattern is connected to the metal film, The second step etches the metal wiring pattern and the metal film by using plasma generated from the second gas.

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