Plasma processing method

Abstract

The present invention provides a vertical pattern in plasma etching of a molybdenum-containing film or a ruthenium-containing film. Provided is a plasma processing method wherein, after a first step in which a molybdenum or ruthenium film is irradiated with a plasma generated using oxygen gas and halogen gas to form a pattern, the following second to fourth steps are repeated up to a prescribed depth: a second step in which a protective film comprising carbon is formed on a pattern side wall by a plasma which uses gas comprising carbon; a third step in which the protective film on a pattern bottom portion is selectively removed and the molybdenum or ruthenium film on the pattern bottom portion is oxidized by a plasma generated using oxygen gas; and a fourth step in which the oxidized molybdenum or ruthenium is etched by a plasma generated using halogen gas. The plasma processing method may further include a fifth step in which the protective film containing carbon formed on the pattern side wall and an altered layer are removed by a plasma comprising hydrogen.

Description

Plasma treatment method

[0001] The present disclosure relates to a plasma processing method, and more particularly to a plasma processing method for patterns of wiring materials such as Mo (molybdenum) and Ru (ruthenium).

[0002] Due to the miniaturization and three-dimensionalization of functional element products such as semiconductor elements, three-dimensional processing technology for various materials such as gate materials, interlayer films, and metals has become important in the dry etching process of semiconductor manufacturing, and technology for controlling and processing complex shapes at the atomic layer level is required. In particular, miniaturization is also progressing in the wiring process, and the increase in wiring resistance of the conventionally used Cu (copper) wiring is becoming an issue in the future, so the use of Mo (molybdenum), Ru (ruthenium), etc. as wiring materials is being considered.

[0003] As a method for etching Mo, Non-Patent Document 1 describes a method of etching a Mo film without a pattern by using oxygen (O ２ ) plasma treatment and chlorine (Cl ２ ) plasma treatment is alternately performed, whereby several atomic layers of Mo are etched in each cycle. When this method is used to process a pattern, O is also etched in the direction of the pattern sidewalls. ２ The oxidation progresses through the treatment, and the oxidized Mo is converted to Cl. ２ Because the material is removed by plasma and is etched isotropically, it is difficult to process the pattern in the vertical direction.

[0004] In addition, as a method for etching the Mo pattern, chlorine gas (Cl ２ ) and oxygen gas (O ２ ), or a mixture of hydrogen bromide (HBr) and oxygen gas (O ２A plasma etching technique using a mixed gas containing halogen and oxygen, such as a mixed gas containing halogen and oxygen, has been reported. However, as shown in FIG. 2(a), in a device structure having a Mo pattern 102, which is the material to be etched and formed on a substrate 101, and a mask 103 formed on the Mo pattern 102, plasma etching using a mixed gas containing halogen and oxygen tends to cause side etching toward the sidewalls of the pattern 102, making it difficult to process the pattern into a vertical cross-sectional shape. Furthermore, because Mo is easily oxidized, there is a problem in that the surface is easily oxidized during and after etching, resulting in an increase in wiring resistance. Therefore, in Non-Patent Document 2, in order to prevent the sidewalls of the Mo pattern 102 from being etched, a thin SiO 2 film is formed as a sidewall protective film for the Mo pattern 102 formed on the substrate 101 during processing of the Mo pattern 102, as shown in FIG. 2(b). ２ After the film 104 is formed by atomic layer deposition (ALD), Cl ２ and O ２ A method has been proposed in which processing is performed using plasma generated using a mixed gas of the above.

[0005] Yebin Lee, et al., Low-temperature plasma atomic layer etching of molybdenum via sequential oxidation and chlorination, Journal of Vacuum Science & Technology A 40, 022602 (2022); https: / / doi.org / 10.1116 / 6.0001603Stefan Decoster, et al., Patterning challenges for direct metal etch of ruthenium and molybdenum at 32 nm metal pitch and below, Journal of Vacuum Science & Technology B 40, 032802 (2022); https: / / doi.org / 10.1116 / 6.0001791

[0006] As mentioned above, in order to vertically process a fine pattern of Mo or Ru, it is important to have a technique for processing while preventing etching in the direction of the sidewall. ２ , or halogen and O ２ In etching using a gas mixture of Mo and Ru, etching proceeds in the sidewall direction, resulting in poor anisotropy and making vertical processing impossible. In addition, since the Mo or Ru surface is very susceptible to oxidation, molybdenum oxide (MoO) remaining after processing is easily oxidized. ｘ ), or ruthenium oxide (RuO ｘ ) increases wiring resistance, which has been an issue.

[0007] In Non-Patent Document 1, O is applied to a Mo film without a pattern. ２ Plasma treatment and Cl ２ By alternately performing plasma treatment, several atomic layers are etched in each cycle. However, when a pattern is processed using this method, O ２ The pattern sidewalls are easily oxidized by the treatment, and the oxidized Mo is converted to Cl ２ Since the pattern is removed by plasma processing, etching also occurs in the sidewall direction of the pattern, making it difficult to process the pattern in the vertical direction.

[0008] In Non-Patent Document 2, in order to prevent etching toward the pattern sidewalls, etching is interrupted during pattern processing and a thin silicon oxide film (SiO ２ A SiO film 104 is formed on the surface of the pattern including the sidewalls of the pattern 102. ２ The film 104 was used as a protective film to prevent etching in the direction of the sidewalls, and Mo was etched to a desired depth.

[0009] However, in this method, the SiO of the protective film 104 is ２ However, it is necessary to remove the SiO of the protective film 104 without etching the Mo on the sidewall of the Mo pattern 102, which is a fine pattern. ２ It was difficult to remove only the SiO ２In the process of removing the protective film 104, the Mo surface is oxidized, and residues of the protective film 104 and reaction products remain at the bottoms 201 of the grooves 200 between the Mo patterns 102, which can cause device defects and increase wiring resistance.

[0010] The present disclosure aims to perform vertical processing by suppressing side etching during Mo processing by forming a sidewall protective film made of a material that is easily removed after processing. It also aims to provide a plasma processing method that etches Mo at a uniform etching rate within the wafer surface and efficiently performs etching by simultaneously removing the unnecessary protective film formed at the groove bottom and performing processing for Mo etching in the Mo vertical processing step. It also aims to remove the sidewall protective film without scraping the sidewall of the Mo pattern after processing, and to remove residual impurities such as oxides formed on the Mo surface, thereby forming a Mo pattern that is free of defects and damage.

[0011] A plasma processing method for processing and forming a pattern by irradiating a pattern of a Mo (molybdenum) film (or a molybdenum-containing film) or a Ru (ruthenium) film (or a ruthenium-containing film) that is a material to be etched formed on a wafer placed on a stage with plasma generated by using an oxygen-containing gas and a halogen-containing gas, the method comprising: ２ a first step of irradiating a Mo film or Ru film with plasma generated using a mixed gas of a gas containing a halogen-containing gas and a gas containing a halogen to form a pattern; a second step of forming a protective film containing C on the sidewalls of the pattern using plasma generated using a gas containing carbon (C) after the first step; a third step of selectively removing the protective film on the bottom of the pattern with plasma generated using a gas containing oxygen (O) compared to the protective film on the sidewalls of the pattern formed in the second step, and oxidizing the Mo film or Ru film on the bottom of the pattern; a fourth step of generating plasma using a gas containing a halogen gas and etching the Mo film or Ru film oxidized in the third step after the third step; and repeating the second to fourth steps to a predetermined depth.

[0012] The plasma processing method may further include a fifth step of removing the protective film containing C formed in the second step, and the altered layer formed on the pattern in the third step and the fourth step, using plasma containing hydrogen (H).

[0013] By forming a protective film containing C on the sidewalls of the pattern and etching the bottom of the pattern, it becomes possible to process the pattern in the vertical direction. In addition, by oxidizing and removing the unnecessary protective film containing C attached to the bottom of the pattern and oxidizing the Mo film or Ru film at the bottom of the pattern, it is possible to etch the Mo film or Ru film efficiently and at a uniform etching rate within the wafer surface. Furthermore, after etching to a desired depth, hydrogen (H ２ By treating the pattern with a plasma containing C, it became possible to remove the protective film containing C and etching residues on the pattern sidewalls without progressing the etching of the Mo film or Ru film on the sidewalls.

[0014] FIG. 1 is a diagram showing an example of a process flow of the plasma processing method of the present disclosure. It is an explanatory diagram for explaining the problems of the conventional method, in which (a) is a diagram showing side etching in the sidewall direction of the pattern 102, and (b) is a diagram showing a state in which a sidewall protective film for preventing side etching in the sidewall direction of the pattern 102 is formed. It is a diagram showing an example of an apparatus for carrying out the plasma processing method of the present disclosure. It is a pattern cross-sectional view explaining an example of a process flow of the plasma processing method of the present embodiment. It is an explanatory diagram of an example of a protective film removal method in the oxidation processing step of the present embodiment. It is an explanatory diagram of an example of an oxidation processing step of the present embodiment, in which (a) shows the dependence of the etch rate on the oxidation processing time, (b) shows the dependence of the saturated etch rate (ER1) on the bias power of the oxidation processing (step S3), and (c) shows the dependence of the oxidation processing time (T) until the start of etching when a C-containing protective film 105 is formed. It is an explanatory diagram of an example of the dependence of the etch rate on the etching step conditions of the present embodiment, in which (a) shows the Cl of the etch rate. ２ (b) shows the dependence of the etching rate on Cl ２1A and 1B are diagrams showing the bias power dependency of processing, the etching amount dependency on the number of cycles when etching is performed using this embodiment, an explanatory diagram of an example of a protective film removal step in this embodiment, and a diagram showing another example of a pattern etched using this embodiment.

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In all drawings, components having the same functions are denoted by the same reference numerals, and repeated description thereof will be omitted.

[0016] The etching apparatus 30 according to this embodiment forms a protective film containing carbon (C) on the sidewall surface of a fine pattern of wiring material containing Mo (molybdenum) or Ru (ruthenium) formed on a wafer, which is a semiconductor substrate made of single-crystal silicon, placed on a stage, and then etches and removes the Mo or Ru film, which is the material to be etched at the bottom of the pattern. Furthermore, after etching, the protective film remaining on the pattern, oxidized components on the Mo or Ru, and residues such as reaction products produced by etching are removed using plasma. In this embodiment, Mo or Ru is described as the material to be etched, but the same process as this embodiment can also be carried out with a molybdenum-containing material (or a molybdenum-containing film) or a ruthenium-containing material (or a ruthenium-containing film).

[0017] FIG. 3 shows an overall configuration of an example of a plasma processing apparatus 30 used in this embodiment. The etching apparatus 30 as the plasma processing apparatus 30 includes a processing chamber 31, a wafer stage 32 on which a wafer is placed, a gas supply unit 33, a bias power supply 41, a high-frequency application unit 42, and an apparatus control unit 43. The apparatus control unit 43 includes functional blocks, not shown, such as an optical system control unit, a gas control unit 44, an exhaust system control unit 45, a high-frequency control unit 46, a bias control unit 47, a protective film formation process control unit 48, a determination unit 49, a memory unit 51, and a clock (not shown). Each of these functional blocks constituting the apparatus control unit 43 can be implemented by a single personal computer (PC). The apparatus control unit 43 includes a determination unit 49 and a database storage unit 50. By referencing the database 50 with a signal sent from the optical system control unit, the determination unit 49 can determine whether the desired processing has been completed.

[0018] The etching apparatus 30 is provided with a wafer stage 32 installed in a processing chamber 31 and a gas supply unit 33 equipped with a gas cylinder and a valve, and based on a control signal 56 from the apparatus control unit 43, an etching gas 34, a protective film forming gas 35, a film quality control gas 36, an etching gas 37, and a protective film removal gas 38 are each supplied to the processing chamber 31 according to the processing step.

[0019] The process gas supplied to the process chamber 31 is decomposed into plasma 57 within the process chamber 31 by radio frequency power 53 applied to the radio frequency application unit 42 from a radio frequency power supply 54 controlled by the device control unit 43. The pressure within the process chamber 31 can be kept constant by flowing a predetermined flow rate of the process gas using a variable conductance valve and a vacuum pump (not shown) connected to the process chamber 31. The radicals generated by the decomposition into plasma 57 within the process chamber 31 diffuse within the process chamber 31 and are irradiated onto the surface of the wafer 100 placed on the wafer stage 32. Ions generated by the plasma 57 are accelerated by a bias voltage 55 applied to the wafer stage 32 from a bias power supply 41 controlled by a bias control unit 47, and are irradiated onto the surface of the wafer 100.

[0020] The processing state of the wafer 100 can be determined by the determination unit 49 by acquiring the spectrum of light emitted from a light source (not shown) and reflected by the wafer 100, or the spectrum of light generated by the plasma 57. In the control unit 43, the reflection spectrum and the emission spectrum are stored in advance as reference data in a database 50, and the determination is made by comparing them with the reference data. That is, the plasma processing apparatus 30 has a function for observing the pattern shape (a light source, a determination unit 49 for determining the spectrum of light reflected by the wafer 100 or the spectrum of light generated by the plasma 57, and the reflection spectrum and the emission spectrum are stored in advance as reference data in the database 50, etc.), and is configured to adjust process conditions such as etching conditions (substrate temperature, flow rate of gas used, bias voltage, processing time such as etching time (oxidation time)) so as to obtain a desired pattern shape and pattern dimensions in the first to fourth steps described below.

[0021] As an example of the etching method of this embodiment, a method will be described in which a protective film containing carbon (C) is selectively formed on the material of a wiring material pattern containing Mo or Ru in the processing chamber 31, and then the protective film containing carbon (C) is modified to ensure etching resistance, and a method in which the modified protective film is used as a mask to process the material to be etched, such as Mo or Ru, with a high selectivity.

[0022] The etching apparatus 30 according to this embodiment forms a protective film containing carbon (C) on the sidewall surface of a fine pattern of wiring material containing Mo or Ru formed on a wafer 100, and then etches and removes the Mo or Ru material to be etched at the bottom of the pattern using a plasma containing halogen. After etching, the protective film remaining on the pattern, oxidized components on the Mo or Ru, and residues such as reaction products (degraded layers) produced by etching are removed by irradiating the pattern with a plasma containing hydrogen (H).

[0023] FIG. 1 is a diagram showing an example of the process flow of the plasma processing method of this embodiment. FIG. 4 is an example of a pattern cross-sectional view illustrating the process flow of the plasma processing method of this embodiment. In this embodiment, as shown in FIG. 4(a), a method of vertically processing a material to be etched 102 containing Mo or Ru formed on the surface of a substrate 101 using a mask pattern 103 as a mask will be described based on the flow of FIG. 1. In FIG. 4, the substrate 101 corresponds to a wafer 100. In this embodiment, as an example, a case will be described in which the material of the mask pattern 103 is a silicon nitride film (SiN) and the material to be etched (etching pattern) 102 is Mo. The material of the mask pattern 103 is a silicon oxide film (SiO ２ ), silicon nitride film (SiN), silicon carbide (SiC), and other materials containing oxygen (O), nitrogen (N), and carbon (C) in addition to Si, titanium nitride (TiN), titanium dioxide (TiO ２ materials containing titanium (Ti), aluminum oxide (Al ２ The same can be applied to materials containing aluminum (Al) or tantalum (Ta), such as tantalum nitride (TaN), and materials containing carbon (C).

[0024] First, the wafer 100 is introduced onto the wafer stage 32 in the processing chamber 31, and a process of etching the material 102 to be etched according to the pattern formed on the wafer 100 is initiated (step S1: etching initiation process, first process). Based on a control signal 56 from the device control unit 43, an etching gas 34 is supplied to the processing chamber 31 at a predetermined flow rate. The supplied etching gas 34 is converted into plasma 57 by high-frequency power 53 applied to the high-frequency application unit 42, generating radicals and ions that etch the material 102 to be etched. The radicals and ions generated by the plasma 57 reach the surface of the wafer 100, and as shown in FIG. 4(b), etching of the material 102 to be etched containing Mo or Ru is initiated using the mask pattern 103 as a mask. For example, chlorine gas (Cl) is used as the etching gas 34. ２ ) 、Hydrogen bromide gas (HBr), nitrogen trifluoride gas (NF ３ ), sulfur hexafluoride gas (SF ６ ) and O ２ The etching gas 34 may be a mixture of tetrafluoromethane gas (CF ４ ), trifluoromethane gas (CHF ３ ) and other fluorocarbon gases, hydrofluorocarbon gases, and O ２ The ions generated from the etching gas 34 are accelerated by a bias voltage 55 applied to the wafer stage 32 from a bias power supply 41 controlled by a bias control unit 47, and are irradiated onto the surface of the wafer 100.

[0025] Here, the etching in step S1 must be stopped before etching progresses toward the sidewall of the material to be etched 102. It is desirable to obtain optimal values ​​for the etching time, bias voltage, and substrate temperature in step S1 in advance. However, the determining unit 49 may determine the pattern dimensions and depth of the pattern of grooves (recesses) formed by etching the material to be etched 102 by acquiring the spectrum of light emitted from a light source installed in the etching apparatus 30 and reflected by the wafer 100, or the reflection spectrum of light generated by the plasma 57. Here, the horizontal direction refers to the direction horizontal to the surface of the wafer 100 (or substrate 101), and the vertical direction refers to the direction perpendicular to the horizontal direction and perpendicular to the surface of the wafer 100 (or substrate 101). The pattern dimension refers to the horizontal spacing of the grooves (recesses), and the pattern depth refers to the vertical depth of the grooves (recesses). If the pattern dimensions of the groove (recess) pattern in the material to be etched 102 are not within a predetermined range, for example, if the pattern dimensions are larger than the predetermined range, the pattern dimensions can be reduced to fall within the predetermined range by increasing the substrate temperature during etching. If the pattern dimensions are smaller than the predetermined range, the pattern dimensions can be increased to fall within the predetermined range by decreasing the substrate temperature during etching. If the dimensions of the initial mask pattern 103 vary across the surface of the wafer 100, a groove (recess) pattern with uniform dimensions can be formed by etching while changing the substrate temperature depending on the position within the wafer stage 32 so that the pattern dimensions of the groove (recess) pattern formed by etching fall within the predetermined range and become uniform.

[0026] Next, before etching of the material to be etched 102 toward its sidewalls in step S1 proceeds, a protective film 105 containing carbon (C) is formed on the surface of the material to be etched 102, including the sidewalls of the groove (recess) pattern (step S2: C-containing protective film formation process, second process). Based on a control signal from the protective film formation process control unit 48, the protective film formation gas 35 is supplied to the processing chamber 31 at a predetermined flow rate, and is converted into plasma 57 by high-frequency power 53 applied to the high-frequency application unit 42, generating radicals and ions. The radicals and ions generated from the protective film formation gas 35 have the property of bonding with or adhering to and depositing on the material of the mask pattern 103 and the material to be etched 102. The radicals and ions generated by the plasma 57 reach the surface of the wafer 100, forming a protective film 105 containing C on the upper surface of the mask pattern 103 and the sidewalls (sidewall surfaces) of the material to be etched 102. The protective film forming process control unit 48 can control the thickness and quality of the protective film 105 by setting and adjusting the flow rate of the protective film forming gas 35, the high frequency power 53 applied to the high frequency application unit 42, the substrate temperature, the plasma irradiation time, etc. As the protective film forming gas 35, for example, methane gas (CH ４ ) 、 Tetrafluoromethane gas (CF ４ ) 、 Trifluoromethane gas (CHF ３ ) 、 Fluoromethane gas (CH ３ F) 、 Perfluorocyclobutane gas (C ４ F8), carbon dioxide gas (CO ２ ) 、 A gas containing carbon (C), such as carbon monoxide gas (CO), or a gas containing carbon and argon gas (Ar), helium gas (He), or O ２ gas 、 CO ２ gas 、 CO gas, nitrogen gas (N ２ ) 、 Hydrogen gas (H ２) can be used. The thickness of the protective film 105 can be adjusted by adjusting the plasma irradiation time, the gas flow rate of the protective film forming gas 35, the substrate temperature, etc. Alternatively, the high frequency power 53 applied to the high frequency application unit 42 can be used to adjust the degree of dissociation of the plasma, thereby adjusting the reactivity of the generated radicals and ions with the material surface, thereby adjusting the thickness of the protective film 105. After the protective film 105 is formed, a gas mixture of Ar gas, He gas, N ２ gas 、 H ２ The shape of the protective film 105 may be smoothed by introducing a gas such as a gas to generate plasma and irradiating the groove (recess) pattern with the plasma, thereby reducing the roughness of the groove (recess) pattern and the roughness of the protective film surface.

[0027] After forming the C-containing protective film 105 in step S2, an oxidation treatment is carried out (step S3: oxidation treatment step, third step), which removes unnecessary C-containing protective film 105 formed on the pattern bottom (or pattern bottom) of the groove (recess) and oxidizes the Mo surface of the etching target region 102 on the pattern bottom, as shown in Fig. 4(d). After oxidation of Mo on the pattern bottom, a halogen-containing plasma treatment is carried out in the next step S4, whereby the oxidized Mo (Mo oxide film) 106 is selectively etched, accelerating the etching of Mo and enabling the etching of Mo on the pattern bottom with good controllability.

[0028] First, based on the control signal 56 from the device control unit 43, the film quality control gas 36 is supplied to the processing chamber 31 at a predetermined flow rate. ２ ), carbon dioxide gas (CO ２ ), sulfur dioxide gas (SO ２A mixed gas of oxygen (O)-containing gas such as Ar and rare gas such as He is supplied to the processing chamber 31. The supplied gas is converted into plasma by high-frequency power 53 applied to the high-frequency application unit 42, decomposed into radicals, ions, etc., and irradiated onto the surface of the wafer 100. FIG. 5 illustrates an example of a protective film removal method in the oxidation treatment step (S3). Ions 107 of Ar or the like generated from the film quality control gas 36 are accelerated by a bias voltage 55 applied to the wafer stage 32 from the bias power supply 41 controlled by the bias control unit 47, and irradiated onto the surface of the wafer 100. As an example, a protective film 105 of the same thickness is formed on the top surface and sidewalls of the mask 103, and on the bottom and sidewalls of the grooves (recesses) in the material 102 to be etched. Carbon (C) in the protective film 105 reacts with oxygen radicals 108 generated from the film quality control gas 36 to form CO. ２and volatilizes. At this time, if the ions 107 have enough energy to pass through the protective film 105 (1052) on the pattern bottom surface 120 of the groove (recess), the protective film 105 (1052) containing C reacts with the oxygen radicals 108 quickly, and the protective film 105 (1052) on the pattern bottom surface 120 can be removed. Also, if the ions 107 have enough energy to pass through the protective film 105 (1052) on the pattern bottom surface 120, the oxygen radicals 108 reach Mo (1022) of the material to be etched 102 below the protective film 105 (1052), and the Mo (1022) below the protective film 105 (1052) is easily oxidized (oxidized Mo (Mo oxide film) 106 in FIG. 4(d)). On the other hand, when ions 107 are irradiated onto the pattern sidewalls 125 of the grooves (recesses) in the material 102 to be etched, the ions 107 are irradiated onto the protective film 105 (1055) deposited on the pattern sidewalls 125 at a low incident angle, and therefore the ions 107 can penetrate only up to the surface region 1251 of the protective film 105 (1055), and it takes more time to remove the protective film 105 (1055) on the pattern sidewalls 125 of the material 102 to be etched than to remove the protective film 105 (1052) on the pattern bottom surface 120. In addition, the protective film 105 (1055) on the pattern sidewalls 125 can prevent the pattern sidewalls 125 of the material 102 to be etched from being oxidized. That is, it is preferable to apply to the wafer stage 32 from the bias power supply 41 controlled by the bias control unit 47 a bias voltage 55 capable of irradiating ions with an energy that passes through the protective film 1052 formed on the pattern bottom 120 but does not pass through the protective film 1055 on the pattern sidewall 125. Therefore, by adjusting the energy of the ions generated from the film quality control gas 36, it is possible to remove the protective film 105 (1052) on the pattern bottom surface 120 while leaving the protective film 105 (1055) on the pattern sidewall 125, and oxidize the material 102 (1022) to be etched on the pattern bottom surface 120.

[0029] Once the protective film 105 (1052) on the bottom surface 120 of the pattern has been removed, the oxide film (oxidized Mo (Mo oxide film) 106 in FIG. 4(d)) of the material to be etched 102 (1022) formed on the bottom surface 120 of the pattern is etched using a plasma containing halogen (step S4: etching process, fourth process).

[0030] First, the etching gas 37 is supplied to the processing chamber 31 at a predetermined flow rate based on the control signal 56 from the device control unit 43. ２ , HBr, CF4, CHF ３ , N.F. ３ , S.F. ６ A mixed gas containing halogens, fluorocarbons, and hydrofluorocarbons such as fluorine, fluorine, and fluorine-containing gases is supplied to the processing chamber 31. The supplied gas is converted into plasma by high-frequency power 53 applied to the high-frequency application unit 42, decomposed into radicals, ions, and the like, and irradiated onto the surface of the wafer 100. As shown in FIG. 4( e), the oxidized components (Mo oxide film 106: FIG. 4( d)) of the oxidized etched material 102 (1022) on the pattern bottom surface 120 are preferentially etched. Ions generated from the etching gas 37 are accelerated by a bias voltage 55 applied to the wafer stage 32 from the bias power supply 41 controlled by the bias control unit 47, thereby enabling more efficient etching of the oxidized etched material 102 (Mo oxide film 106: FIG. 4( d)) on the pattern bottom surface 120. On the other hand, since etching of the material 102 to be etched on the pattern sidewalls 125 is suppressed by the C-containing protective film 105, lateral etching of the material 102 to be etched on the pattern sidewalls 125 is suppressed, and the material 102 to be etched on the pattern bottom surface 120 can be etched in the vertical direction.

[0031] FIG. 6 is an explanatory diagram of the oxidation treatment step (S3) when etching is performed by forming a protective film (step S2), performing an oxidation treatment (step S3), and etching (step S4). FIG. 6(a) shows the dependence of the etch rate on the oxidation treatment time. 112 shows the dependence of the etch rate on the oxidation treatment time when the C-containing protective film 105 is not formed on the material to be etched 102, and 113 shows the dependence of the etch rate on the oxidation treatment time when the C-containing protective film 105 is formed on the material to be etched 102. When the C-containing protective film 105 is not formed, the etching rate increases rapidly when the oxidation treatment (step S3) is performed and saturates at a certain etch rate (ER1). As an example, when Mo was oxidized at a pressure of 0.2 Pa, the etch rate saturated at 4 nm / cycle. It was found that when the C-containing protective film 105 is formed on the material to be etched 102, oxidation for a certain oxidation treatment time (T) or more is required for etching. This indicates that oxidation is suppressed by the C-containing protective film 105 and that time is required to remove the C-containing protective film 105 by oxidation. Even when the C-containing protective film 105 is formed, if the oxidation treatment time is extended, the etch rate (ER1) becomes saturated at approximately the same rate as when the C-containing protective film 105 is not formed, which indicates that the C-containing protective film 105 is removed by oxidation.

[0032] 6B shows the bias power dependency of the saturated etch rate (ER1) in the oxidation treatment (step S3). Mo, which is the material 102 to be etched, is a material that is easily oxidized. When the oxidation treatment (step S3) is performed using plasma, the thickness of the Mo oxide film does not depend greatly on the bias power. Therefore, it was found that the saturated etch rate is almost independent of the bias power in the oxidation treatment (step S3). For example, when O ２ Even when the processing time was increased from 1 second to 10 seconds, the etch rate remained constant at about 4 nm / cycle. ２ Even when the bias power of the process was increased from 0 W to 50 W, the etch rate remained almost constant at about 4 nm / cycle.

[0033] 6C shows the bias power dependence of the oxidation process time (T) until the start of etching when a C-containing protective film 105 is formed. It can be seen that the time required to remove the protective film 105 is highly dependent on the bias power of the oxidation process (step S3), i.e., the ion energy. When etching a line pattern such as that shown in FIG. 4, ions are incident on the protective film 105 (1052) on the bottom surface 120 of the pattern from a perpendicular direction, but on the protective film 105 (1055) on the sidewalls 125 of the pattern at a low angle. Therefore, the energy in the perpendicular direction relative to the protective film 105 (1055) on the sidewalls 125 is small. As a result, the time required to remove the protective film 105 (1055) on the sidewalls 125 (Tsw) is longer than the time required to remove the protective film 105 (1052) on the bottom surface 120 of the pattern (Tbtm) (Tsw > Tbtm). Therefore, if the oxidation treatment time of the oxidation treatment (step S3) is set between Tbtm and Tsw, the protective film 105 (1052) on the pattern bottom surface 120 can be removed while leaving the protective film 105 (1055) on the pattern sidewall 125. If the protective film 105 (1052) on the pattern bottom surface 120 is removed, the material to be etched 102 (1022) on only the pattern bottom surface 120 can be oxidized.

[0034] 7 is a diagram illustrating an example of the dependency of the etching rate on the etching step conditions in this embodiment. ２ In the case where the etching rate is 100%, the etching rate of Cl is 100%. ２ The dependence of the etching rate on the processing time is shown in FIG. ２ The bias power dependence of the treatment is shown. ２ As the treatment time increases, the Cl ２ As the bias power of the process increases, the etch rate tends to increase gradually. ２ Increasing the treatment time from 3 seconds to 20 seconds increased the etch rate from 3 nm / cycle to 6 nm / cycle, and Cl ２ Increasing the bias power of the process from 0 W to 50 W increased the etch rate from 3 nm / cycle to 5-6 nm / cycle.

[0035] Here, in the protective film forming step (S2) of forming the C-containing protective film 105 on the pattern sidewall 125 and the oxidation treatment step (S3) of oxidizing the C-containing protective film 105 on the pattern bottom surface (bottom) 120, the protective film 105 below the pattern sidewall 125 can be oxidized and removed, thereby laterally etching the lower part of the pattern sidewall 125, thereby making the pattern dimensions uniform across the surface of the wafer 100. It is desirable to obtain optimal values ​​for the etching time (oxidation time), bias voltage, and substrate temperature in the oxidation treatment step S3 in advance. However, the pattern dimensions and depth may be determined by the determination unit 49 by acquiring the spectrum of light emitted from a light source installed in the etching apparatus 30 and reflected by the wafer 100, or the reflection spectrum of light generated by the plasma 57, and the pattern shape may be observed. If the pattern dimensions are not within a predetermined range, for example, if the pattern dimensions are larger than the predetermined range, the substrate temperature may be increased and the oxidation treatment step (S3) and etching step (S4) may be performed to reduce the pattern dimensions to fall within the predetermined range. For example, when the substrate temperature is 10°C, the etch rate is 2 nm / cycle, but when the substrate temperature is increased to 80°C, the etch rate increases to 5 nm / cycle. If the pattern dimensions are smaller than the predetermined dimensions, the pattern dimensions can be enlarged to fall within the predetermined range by lowering the substrate temperature and performing the oxidation treatment step (S3) and etching step (S4). Alternatively, the pattern dimensions can be reduced to fall within the predetermined range by increasing the substrate temperature and thinning the protective film 105 in the protective film formation step (S2). On the other hand, increasing the pattern dimensions to fall within the predetermined range can be achieved by lowering the substrate temperature and thickening the protective film 105 in the protective film formation step (S2). By varying the substrate temperature across the wafer surface during etching, the pattern dimensions could be precisely adjusted. That is, in the oxidation treatment step (S3), the in-plane temperature distribution of the wafer stage 32 is adjusted to adjust the substrate temperature of the wafer 100, thereby uniforming the in-plane pattern dimensions across the surface of the wafer 100.Alternatively, it is preferable to provide a step of observing the pattern shape and adjusting the process conditions (substrate temperature, flow rate of gas used, bias voltage, processing time such as etching time (oxidation time)) such as etching conditions of the etching start step (S1), protective film formation step (S2), oxidation treatment step (S3), and etching step (S4) so ​​as to obtain the desired pattern dimensions.

[0036] While the etching process (S4) is being performed, the film thickness, pattern dimensions, and etching depth of the protective film 105 are measured using an optical system. A cycle of the protective film formation step (S2), oxidation treatment step (S3), and etching step (S4) is repeated a predetermined number of times until the pattern depth of the material 102 to be etched on the wafer 100 reaches the desired etching depth. The etching is terminated (step S5) when the predetermined number of etching processes has been completed or when the desired etching depth is reached (Yes). Here, the cyclic process refers to a process in which one cycle of the protective film formation step (S2), oxidation treatment step (S3), and etching step (S4) is repeated a predetermined number of times. Figure 8 shows the dependence of the etching amount on the number of cycles when using the cyclic process described in this example. It was confirmed that a certain amount of etching depth was achieved per cycle.

[0037] As shown in FIG. 4( f), after etching to a predetermined depth, the C-containing protective film 105 is removed (step S6: protective film and residue removal process, fifth process). FIG. 9 shows a schematic diagram of a cross section of the pattern after etching to a predetermined depth. The C-containing protective film 105, an oxide film 106 of the oxidized material 102, and etching residues 111 are formed on the pattern of the material 102 to be etched. For example, when the material 102 to be etched is a wiring material, the C-containing protective film 105, the oxide film 106 of the oxidized material 102, and the etching residues 111 remaining on the material 102 to be etched need to be removed after etching because they may become mixed as impurities in the wiring material, increasing the wiring resistance or causing disconnections. Furthermore, in fine wiring and the like, the wiring width and the pitch between wirings are small (narrow), so it was necessary to remove the C-containing protective film 105, the oxide film 106 of the oxidized material to be etched 102, and the etching residues 111 without removing the unaltered material to be etched 102. Furthermore, since roughness of the sidewall 125 of the material to be etched 102 after removing the C-containing protective film 105, the oxide film 106 of the oxidized material to be etched 102, and the etching residues 111 increases the wiring resistance, it was necessary to suppress the roughness when removing them.

[0038] 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. Once the protective film removal gas 38 has been supplied and the interior of the processing chamber 31 is at a predetermined pressure, the apparatus control unit 43 controls the high frequency power supply 54 to apply high frequency power 53 to the high frequency application unit 42, thereby generating plasma from the protective film removal gas 38 inside the processing chamber 31. The protective film removal gas 38 becomes plasma, generating radicals 109 and ions 110 that remove the protective film 105 on the material to be etched 102, the oxide film 106 of the oxidized material to be etched 102, and the etching residue 111. The etching residue 111 can be referred to as an altered layer. For example, H ２ A gas mixture containing H ２ Gas and N ２A mixed gas such as the above can be used. The C-containing protective film 105 reacts with the H radicals 109 and H ions 110 to generate CH-based reaction products, which can be removed. At this time, the material to be etched 102 below the protective film 105 does not react with H, so the protective film 105 can be removed without removing the material to be etched 102. The oxide film 106 of the oxidized material to be etched 102 is converted into H by the hydrogen radicals 109 and hydrogen ions 110. ２ This reduces the oxide film 106 of the etched material 102, which has been oxidized by generating O. Examples of the etching residues 111 include reaction products of the C-containing protective film 105 with halogen ions and halogen radicals. These reaction products of carbon (C) and halogen can be volatilized and removed by hydrogen radicals 109 and hydrogen ions 110. In this way, the processed etched material 102 can be removed without being scraped. Furthermore, this removal step S6 may be performed after removing the mask material 103.

[0039] 10 shows another example of a pattern etched in this embodiment. Patterns with different horizontal dimensions (spacing) are formed as mask patterns 103 on the surface of the same wafer 100 (substrate 101), and the material 102 to be etched is processed with different pattern dimensions (spacing). When patterns 114 with different processing dimensions formed on the same wafer 100 are etched, the etching depth may differ depending on the pattern dimensions. However, in this embodiment, an oxide film 106 with the same thickness is formed in the oxidation step (S3) even at the bottom of the patterns with different dimensions, and the oxide film 106 is etched in the etching step (S4). This allows the same etching depth to be achieved even at the bottom of the patterns with different horizontal dimensions (spacing).

[0040] In this manner, the C-containing protective film 105 is formed on the pattern sidewall 125 (S2), the C-containing protective film 105 (1052) on the pattern bottom surface (bottom) 120 is oxidized (S3), and the oxide film 106 of the etched material 102 at the pattern bottom 120 is etched (S4). This suppresses lateral etching of the pattern, enabling the pattern to be processed vertically. Furthermore, by oxidizing and removing the unnecessary C-containing protective film 105 attached to the pattern bottom 120 and oxidizing the molybdenum or ruthenium that is the etched material 102 at the pattern bottom 120, uniform processing can be achieved within the surface of the wafer 100. Furthermore, after etching to the desired depth, the wafer is treated with a hydrogen-containing plasma (step S6) to remove the C-containing protective film 105 and etching residues 111 from the pattern sidewall 125 without progressing etching of the molybdenum or ruthenium on the sidewall 125 of the etched material 102. This makes it possible to pattern the material 102 to be etched without causing defects or deteriorating electrical characteristics such as wiring resistance.

[0041] Furthermore, in this embodiment, the case where a pattern shape perpendicular to the substrate 101 is processed has been mainly described, but it is also possible to form a pattern having an inverse tapered shape by forming a C-containing protective film 105 on the pattern sidewall 125 (S2), and then oxidizing and removing the protective film 105 below the pattern sidewall 125 in the oxidation treatment step (S3) of oxidizing the pattern bottom 120, thereby etching the lower part of the pattern sidewall 125 in the horizontal direction.

[0042] Although the present disclosure has been specifically described above based on the examples, it goes without saying that the present disclosure is not limited to the above examples and can be modified in various ways without departing from the spirit of the present disclosure. For example, the above examples have been described in detail to clearly explain the present disclosure, and the present disclosure 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 example with other configurations.

[0043] 30: Etching apparatus, 31: Processing chamber, 32: Wafer stage, 33: Gas supply unit, 34: Etching gas, 35: Protective film formation gas, 36: Film quality control gas, 37: Etching gas, 38: Protective film removal gas, 41: Bias power supply, 42: High frequency application unit, 43: Apparatus control unit, 44: Gas control unit, 45: Exhaust system control unit, 46: High frequency control unit, 47: Bias control unit, 48: Protective film formation process control unit, 49: Determination unit, 50: Database, 51: Storage unit, 52: Clock, 53: High frequency power, 54: High frequency power supply, 55: Bias voltage, 56: Control signal, 57: Plasma, 100: Wafer, 101: Substrate, 102: Material to be etched, 103: Mask, 104: SiO ２ Protective film, 105: C-containing protective film, 106: oxide film, 107: ions, 108: oxygen radicals, 109: hydrogen radicals, 110: hydrogen ions, 111: residues, 112: oxidation treatment time dependence of etching rate when no protective film is present, 113: oxidation treatment time dependence of etching rate when a protective film is formed, 114: patterns of different dimensions, ER1: saturated etching rate, T: oxidation time until etching starts, Tsw: oxygen treatment time required for etching the sidewalls, Tbtm: oxygen treatment time required for etching the bottom of the pattern

Claims

1. A first step of forming a pattern on a molybdenum-containing or ruthenium-containing film using a plasma generated by a mixture of an oxygen-containing gas and a halogen-containing gas; a second step of forming a protective film on the pattern using plasma generated by a carbon-containing gas after the first step; a third step of oxidizing the molybdenum-containing film or the ruthenium-containing film at the bottom of the pattern using plasma generated by an oxygen-containing gas after the second step; and a fourth step of etching the oxidized molybdenum-containing film or the oxidized ruthenium-containing film using plasma generated by a halogen-containing gas after the third step, A plasma processing method comprising repeating the second to fourth steps until a predetermined pattern depth is achieved.

2. 2. The plasma processing method according to claim 1, The plasma processing method further comprises a fifth step of removing, after the fourth step, the altered layer formed on the surface of the molybdenum-containing film or the altered layer formed on the surface of the ruthenium-containing film and the protective film by using plasma generated by a hydrogen-containing gas.

3. 2. The plasma processing method according to claim 1, The plasma processing method, wherein the halogen-containing gas is chlorine gas (Cl2), hydrogen bromide gas (HBr), nitrogen trifluoride gas (NF3) or sulfur hexafluoride gas (SF6).

4. 2. The plasma processing method according to claim 1, The plasma processing method is characterized in that the halogen-containing gas is tetrafluoromethane gas (CF4) or trifluoromethane gas (CHF3).

5. 2. The plasma processing method according to claim 1, The plasma processing method is characterized in that the carbon-containing gas is methane gas (CH4), tetrafluoromethane gas (CF4), trifluoromethane gas (CHF3), fluoromethane gas (CH3F), perfluorocyclobutane gas (C4F8), carbon monoxide gas (CO), or carbon dioxide gas (CO2).

6. 3. The plasma processing method according to claim 1, The plasma processing method further comprises, after the second step, a step of reducing roughness of the protective film using plasma generated from argon gas (Ar), helium gas (He), nitrogen gas (N2), and hydrogen gas (H2).