Plasma processing method and inspection method for pattern of metal film

Abstract

A plasma processing method for forming a pattern of a metal film according to one embodiment of the present invention includes: a first step (S1) for acquiring, from an image of a mask pattern acquired using an electron beam, roughness and dimensions of the mask pattern and information of grains of the metal film; a third step (S2) for defining an etching condition of the metal film on the basis of an allowable value in roughness of the pattern of the metal film; and a fourth step (S3 to S7) for etching the metal film using the defined etching condition of the metal film.

Description

Plasma processing method and metal film pattern inspection method

[0001] The present invention relates to a plasma processing method and a method for inspecting a pattern of a metal film.

[0002] Due to the miniaturization and three-dimensionalization of functional element products such as semiconductor devices, three-dimensional processing technologies for various materials have become important in the dry etching process of semiconductor manufacturing, requiring technology to control and process complex shapes at the atomic layer level. Miniaturization is also progressing in the wiring process, and with the commonly used Cu (copper) wiring, the future issue of increased wiring resistance is becoming a problem as the wiring width decreases. This is because a barrier metal layer is formed between the interlayer film material and the Cu wiring to prevent electromigration, in which metal atoms in the wiring move due to current and lead to disconnection. However, as the wiring width decreases, the proportion of the barrier metal layer in the wiring width increases rapidly, accelerating the increase in wiring resistance.

[0003] To solve this problem, the use of Mo (molybdenum), Ru (ruthenium), and the like as wiring materials has been considered. These metal materials have a relatively high melting point, allowing the barrier metal to be thin, and are therefore expected to reduce the resistance of wiring, including the barrier metal. Furthermore, these metal materials are expected to be materials that can realize low-resistance wiring because wiring patterns can be formed using plasma etching or the like, allowing wiring patterns to be formed from metal films with relatively large grain agglomerates.

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

[0005] On the other hand, as a conventional technique for non-destructively measuring or inspecting the roughness, dimensions, etc. of a wiring pattern, for example, a scanning electron microscope scans an electron beam onto a pattern sample, detects secondary electrons generated secondarily from the sample surface, and acquires a secondary electron image, thereby obtaining information on the dimensions, etc. of the pattern sample. For example, by scanning and irradiating an incident electron beam 116 onto a pattern sample as shown in Figure 3(a), secondary electrons 117 generated on the sample surface are detected, and a secondary electron image as shown in Figure 3(b) is acquired, thereby enabling the measurement of the dimensions 111 and roughness 112 of a mask pattern 103 on the top layer of the sample.

[0006] However, conventionally, an electron beam of several hundred eV or more and several keV or less has generally been used as the incident electron beam 116, and therefore, as shown in Figure 3(a), when the width of the pattern (wiring pattern) of the material to be etched 102 under the mask pattern 103 is comparable to or narrower than the dimension 111 of the mask pattern 103, the incident electron beam 116 cannot reach the pattern of the material to be etched 102, and the dimension, roughness, and grain cannot be measured. Furthermore, even when the thickness of the mask pattern 103 on the top layer of the sample is thin and the incident electron beam 116 reaches the pattern (wiring pattern) of the material to be etched 102, secondary electrons 117 generated from the sidewall are blocked by the mask pattern 103 and cannot be detected by a detector, and therefore the dimension, roughness, and grain of the pattern of the material to be etched 102 cannot be measured.

[0007] Transmission electron microscopy is known as a method for evaluating the dimensions, roughness, and grain of wiring patterns that are not the top layer of the pattern. Transmission electron microscopy allows electrons with an energy of several hundred keV to be incident on the sample, and the dimensions, roughness, and grain of the pattern of the material 102 to be etched can be measured from an image obtained by detecting the electron beam that has passed through the sample. However, this method requires the sample to be thinned and subjected to destructive testing in order to detect the electrons that have passed through the sample. Therefore, wafers evaluated using this method could not be used for the next process in a semiconductor manufacturing line.

[0008] As a method for measuring the internal structure of a sample without cutting the sample, the conventional technology disclosed in Patent Document 1 has a function of irradiating an incident electron beam 118 having energy sufficient to reach portions not exposed to the incident electron beam 118 onto a sample and detecting a signal 119 generated secondarily from the portion irradiated with the incident electron beam 118, as shown in Fig. 4(a) . By using this technology, an incident electron beam 118 having energy sufficient to reach a material 102 to be etched under a mask pattern 103 is irradiated, and reflected electrons 119 generated secondarily from the pattern of the material 102 to be etched are detected, thereby obtaining a reflected electron image as shown in Fig. 4(b) , and thereby obtaining information on the roughness 114, dimensions 113, and grains 115 of the pattern of the material 102 to be etched.

[0009] Japanese Patent Laid-Open No. 7-27549 Japanese Patent Laid-Open No. 2006-215020 Japanese Patent Laid-Open No. 2019-215788

[0010] R. S. Smith, et al. 12, "An evaluation of Fuchs-Sondheimer and Mayadas-Shatzkes models below 14nm node wide lines", [online], February 13, 2019, AIP Advances 9, 025015 (2019), [searched on October 11, 2023], Internet <URL: https: / / doi.org / 10.1063 / 1.<5063896> Sara. Paolillo, et al. 5, "Direct metal etch of ruthenium for advanced interconnect", Journal of Vacuum Science and Technology B 36, 03E103 (2018) Shibesh Dutta, et al. 8, "Thickness dependence of the resistivity of platinum-group metal thin films", Journal of Applied Physics 122, 025107 (2017) A. F. Mayadas, et al. 1, "Electrical-Resistivity Model for Polycrystalline Films: the Case of Arbitrary Reflection at External Surfaces", Physical Review B 1, 1382 - Published 15 February 1970 Daniel Gall, "The search for the most conductive metal for narrow interconnect lines", Journal of Applied Physics 127, 050901 (2020)

[0011] First, Non-Patent Document 2 discloses a technique for forming a wiring pattern using wiring materials such as Mo and Ru by dry etching. In a wiring pattern, the formation of roughness on the surface or sidewall increases the wiring resistance. Therefore, to form a low-resistance wiring pattern, a processing technique is required that controls and processes the cross section of the wiring to a desired shape while simultaneously suppressing the formation of surface roughness and sidewall roughness. When processing a wiring pattern by dry etching, a mask pattern is transferred to the underlying wiring material, so suppressing mask roughness is an issue. Furthermore, the roughness of the processed wiring pattern also varies depending on the processing conditions of the wiring pattern. Another issue is that the roughness formed after processing of a Ru wiring pattern varies not only depending on the Ru etching conditions but also on the Ru film formation method and film formation temperature.

[0012] Furthermore, as shown in Non-Patent Documents 2 and 3, in metal wiring, electrons are easily scattered at grain boundaries, so the wiring resistance depends on the size of the grain agglomerates, and when the grain agglomerates are small, the wiring resistance increases. Furthermore, when processing a wiring pattern using plasma etching or the like, the grain boundaries in a metal material are more easily etched than the interior of the grain agglomerates, so there is a problem that etching progresses from the grain boundaries, increasing the roughness of the sidewalls of the wiring pattern. Thus, there is a problem that the roughness of the wiring pattern is formed depending not only on the roughness of the mask but also on the grain size of the material to be etched. Furthermore, there is a problem that such roughness increases the wiring resistance and causes disconnections, degrading the electrical characteristics of the wiring and preventing desired device characteristics from being obtained.

[0013] On the other hand, before processing the wiring pattern as described above, the dimensions and roughness of the mask pattern can be measured by scanning an incident electron beam 116 having an energy of several hundred eV to several keV with a scanning electron microscope, irradiating the mask pattern 103 with the incident electron beam 116, and detecting secondary electrons 117 generated from the sample surface to obtain an image, thereby obtaining information on the sample, such as the dimensions 111 and roughness 112 of the mask pattern 103. However, with this method, if the width of the wiring pattern under the mask pattern 103 is equal to or narrower than the dimension (width) 111 of the mask pattern 103, the secondary electrons generated from the sidewalls of the wiring pattern are blocked by the mask pattern 103 and cannot be detected by the detector, which poses a problem in that the dimensions 113, roughness 114, and grain 115 of the wiring pattern cannot be measured inline.

[0014] A conventional technique disclosed in Patent Document 1 as a method for measuring the internal structure of a sample without cutting the sample has a function of irradiating an incident electron beam 118 having energy capable of reaching portions not exposed to the incident electron beam 118 and detecting a signal containing a large amount of reflected electrons 119 secondarily generated from the portion irradiated with the incident electron beam 118. When this technique was used to evaluate a material to be etched (metal film) 102 under a mask pattern 103 before etching as shown in Figure 2(a), an image of the signal secondarily generated from the material to be etched (metal film) 102 could be obtained, and information on grains 115 of the metal wiring could be evaluated.

[0015] However, with this technique, although it is possible to obtain information on the dimensions 111 and roughness 112 of the mask pattern 103 and information on the grain 115 of the underlying metal film 102, it is not possible to evaluate the electrical characteristics of the wiring pattern formed after etching. Furthermore, when evaluating a wiring pattern such as that shown in FIG. 4( b), it is possible to obtain information on the dimensions 113 and roughness 114 of the pattern (wiring pattern) of the material to be etched 102 and information on the grain 115, but it is not possible to evaluate the electrical characteristics of the formed wiring pattern. Therefore, it is not possible to process the material to be etched 102 to the appropriate dimensions 113 and roughness 114 and to control the pattern shape and electrical characteristics according to the comprehensive information on the roughness 112 and dimensions 111 of the mask pattern 103 and the grain 115 of the material to be etched 102.

[0016] The present invention aims to perform etching that ensures wiring resistance by acquiring information on the roughness and grain of a mask or metal wiring in-line and performing etching that reduces the roughness of the wiring pattern to an allowable value or less. Another aim is to estimate optimal etching conditions from the measured dimensions, roughness, and grain information and provide a wiring pattern with low wiring resistance.

[0017] A plasma processing method for forming a pattern of a metal film according to one embodiment of the present invention includes a first step of acquiring information on the roughness and dimensions of a mask pattern and the grain of the metal film from an image of the mask pattern acquired using an electron beam; a third step of specifying etching conditions for the metal film based on an allowable value for the roughness of the pattern of the metal film; and a fourth step of etching the metal film using the specified etching conditions for the metal film.

[0018] The wiring resistance can be estimated based on information on the dimensions and roughness of the mask pattern and the grain size of the metal film, and the optimum etching conditions can be set based on the tolerance for the roughness of the metal film pattern from the acquired information to create a wiring pattern with low wiring resistance, thereby providing a high-performance device.

[0019] FIG. 1 is a diagram showing an example of a process flow of a plasma processing method of the present embodiment; FIG. 2 is an explanatory diagram of a cross-sectional structure of a sample in the flow of the plasma processing method of the present embodiment; FIG. 3 is an explanatory diagram for explaining problems of a conventional method, showing (a) a cross-sectional view and (b) a top view of a secondary electron image of a sample on which a mask is formed after metal pattern processing; FIG. 4 is an explanatory diagram of an example of a metal pattern inspection method of the present embodiment, showing (a) a cross-sectional view and (b) a top view of a backscattered electron image in the case where an electron beam capable of reaching the metal pattern is irradiated; FIG. 5 is a diagram showing an example of a scanning secondary electron microscope used for pattern inspection of the present embodiment; FIG. 6 is a diagram showing an example of a secondary electron image and a backscattered electron image of a mask pattern acquired in step 1 of the present embodiment; FIG. 7 is a diagram showing an example of a secondary electron image and a backscattered electron image of a pattern acquired in step 8 of the present embodiment; FIG. 8 is a diagram showing an example of a plasma processing apparatus to which the present embodiment is applied; FIG. 9 is an explanatory diagram of a method for setting a roughness tolerance of the present embodiment; and FIG. 10 is an explanatory diagram of a method for setting a protective film thickness of a mask of the present embodiment.

[0020] 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.

[0021] FIG. 1 is a diagram showing an example of a process flow of the pattern forming method of this embodiment. FIG. 2 is an example of a pattern cross-sectional view illustrating the process flow of the pattern forming method of this embodiment. In this embodiment, a method for processing a material to be etched (metal film) 102, which is a metallic material, will be described based on the flow of FIG. 1. As the material to be etched 102, which is a metallic material, a metal film containing Mo or Ru can be used. In FIG. 2, a substrate 101 corresponds to a wafer. In this embodiment, as an example, a case will be described in which a silicon nitride film (SiN) is used as the material of the mask pattern 103 and Ru is used as the metallic material of the material to be etched (metal film) 102. 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 Titanium (Ti)-containing materials such as aluminum oxide (Al ２ O ３ ), materials containing aluminum (Al) or tantalum (Ta), such as tantalum nitride (TaN), and materials containing carbon (C) can be similarly implemented.

[0022] First, in the wafer inspection process (step S1) after mask formation, a semiconductor inspection device is used to irradiate an incident electron beam onto a wafer having a mask pattern 103 formed on a material to be etched (metal film) 102, and the width dimension of the mask pattern 103, the roughness of the mask pattern sidewalls, and the grain of the material to be etched (metal film) 102 are measured (step S1). After the mask pattern 103 shown in FIG. 2( a) is formed, the incident electron beam is scanned and irradiated, and secondarily generated electrons are detected to obtain an image. As the incident electron beam, an electron beam having an energy sufficient to penetrate the mask pattern 103 and reach the material to be etched (metal film) 102 is incident, and components mainly consisting of secondarily generated secondary electrons are detected to measure the roughness and dimensions of the mask pattern 103. Meanwhile, when the incident electron beam reaches the material to be etched (metal film) 102, many electrons are reflected by metal atoms and reach a detector. The scattering cross section of the reflected electrons increases depending on the atomic number of the metal atoms in the target, so by acquiring an image mainly composed of reflected electrons, it is possible to obtain information about the grains of the material to be etched (metal film) 102.

[0023] An image of a signal mainly composed of backscattered electrons can be obtained, for example, by a semiconductor inspection device 1 as shown in FIG. 5 . An incident electron beam 118 emitted from an electron source 5 is polarized by a scanning coil 8 controlled by a scan control unit 7 and raster-scanned on a wafer 100 placed on a moving stage 3. Secondary electrons and backscattered electrons secondarily generated from the surface of the wafer 100 by the scanning of the incident electron beam 118 are detected by a secondary electron detector 11 and a backscattered electron detector 12, respectively, and amplified by an amplifier 13. The secondary electron detector 11 detects low-energy components mainly composed of secondary electrons generated from the wafer 100, while the backscattered electron detector 12 detects high-energy components mainly composed of backscattered electrons. The electron signals amplified by the amplifier 13 are sent to the controller 4 via a converter 14 and a detector controller 15, and are displayed as a scanned image on a monitor 16 by the controller 4.

[0024] 6A and 6B show examples of images acquired by the semiconductor inspection device 1 in the wafer inspection process (step S1) after mask formation. FIG. 6A shows a secondary electron image 120, which mainly captures secondary electrons, and FIG. 6B shows a backscattered electron image 121, which mainly captures backscattered electrons. In FIG. 6A, secondary electrons generated in large quantities at the edge of the mask pattern 103 are captured, allowing the dimensions and roughness of the mask pattern 103 to be measured. FIG. 6B shows a backscattered electron image 121 generated by backscattered electrons reflected by atoms contained in the material to be etched (metal film) 102. Since the contrast differs depending on the crystal orientation of the grains, the grains of the material to be etched (metal film) 102 can be evaluated.

[0025] The roughness of the mask pattern 103 can be measured, for example, by the method disclosed in Patent Document 2, and the grains of the material to be etched (metal film) 102 can be measured, for example, by the method disclosed in Patent Document 3, to obtain grain information such as the grain size, the length of the grain boundary crossing the mask pattern 103, and the crystal orientation. The secondary electron image 120 and the backscattered electron image 121 acquired in step S1, as well as information on the measured dimensions and roughness of the mask pattern 103 and the grains of the material to be etched (metal film) 102, are stored in the storage unit 18. Here, while FIG. 5 illustrates the storage unit 18 and the calculation unit 19 in the semiconductor inspection apparatus 1, the storage unit 18 and the calculation unit 19 may be located in an external server 21 or in the plasma processing apparatus 30 shown in FIG. 8.

[0026] Next, from the information on the roughness and dimensions of the mask pattern 103 and the grain of the material to be etched (metal film) 102 obtained in the pattern inspection (step S1) performed after the mask formation, the wiring resistance after processing the material to be etched (metal film) 102 is estimated (step S2) on the assumption that the pattern of the material to be etched (metal film) 102 is transferred and formed with the same roughness as the mask pattern 103. The information on the measured dimensions and roughness of the mask pattern 103 and the grain of the material to be etched (metal film) 102 stored in the storage unit 18 is sent to the calculation unit 19, which estimates the wiring resistance after processing and calculates the allowable roughness value.

[0027] Non-Patent Documents 4 and 5 disclose that the resistance of a wiring pattern depends not only on the resistivity of the wiring material, but also on the scattering of electrons flowing through the wiring due to the roughness of the wiring sidewalls and the scattering at the grain boundaries of the wiring material. The relationship between scattering at the sidewalls, scattering at the grain boundaries, and the effective resistance of the wiring can be expressed as follows (Equation 1): ρ = ρ0 + ρ0λ * 3(1 - p) / 4d + ρ0λ * 3R / 2D(1 - R) ... (1) where ρ0 is the volume resistivity of the wiring metal, λ is the mean free path of electrons in the wiring metal, D is the grain size coefficient, p is the sidewall scattering coefficient, d is the wiring width, and R is the grain boundary scattering coefficient. Thus, the effective volume resistivity ρ of the wiring pattern can be calculated as the sum of scattering due to sidewall roughness and scattering due to grain boundaries. In step S2, the material to be etched (metal film) 102 is not processed. However, in the subsequent metal etching step S5, the material to be etched (metal film) 102 is basically processed based on the mask pattern 103. Therefore, the dimensions and roughness of the secondary electron image 120 of the mask pattern 103 acquired in step S1 are used as the dimensions and sidewall roughness of the material to be etched (metal film) 102 to estimate the wiring resistance. The wiring width d can be calculated from the dimensions of the mask pattern 103 in the secondary electron image 120. The sidewall scattering coefficient p varies depending on the wiring roughness, and can therefore be calculated from the roughness of the mask pattern 103 measured from the secondary electron image 120. The grain size coefficient D can be calculated from the grain size of the material to be etched (metal film) 102 acquired from the backscattered electron image 121.

[0028] After the calculation unit 19 estimates the wiring resistance, it is confirmed whether the estimated resistance value is within the desired resistance value range stored in the storage unit 18. If the wiring resistance value estimated in step S2 is within the desired resistance value range, the material to be etched (metal film) 102 is etched according to the etching conditions stored in the storage unit 18 (steps S3, S4, and S5). On the other hand, if the wiring resistance value estimated in step S2 is not within the desired resistance value range, the material to be etched (metal film) 102 is etched under the processing conditions stored in the database so that the pattern roughness of the material to be etched (metal film) 102 falls within the allowable value. If the resistance value is not within the desired resistance value range, first, the pattern dimensions and roughness of the material to be etched (metal film) 102 necessary to bring the wiring resistance within the desired resistance value range are calculated.

[0029] As an example, Figure 9(a) shows the relationship between wiring resistance and roughness as an explanatory diagram of a method for setting the tolerance for roughness of the pattern of the material to be etched (metal film) 102. For example, as shown in Figure 9(a), when the measured grain size is large, the tolerance for sidewall roughness required to obtain the desired wiring resistance can be set larger than when the grain size is small. The relationship between wiring resistance and roughness may be determined using a relationship obtained in advance using a test pattern, or may be determined by calculation from the relationship in (Equation 1) above.

[0030] If the tolerance for the roughness of the pattern of the material to be etched (metal film) 102 thus determined is greater than the roughness of the mask pattern 103 measured in step S1, the roughness can be reduced, for example, by forming a protective film 104 in steps S3 and S4. Figure 9(b) shows the relationship between the thickness of the protective film 104 formed on the mask pattern 103 and the mask roughness. This relationship can be obtained in advance through experiments using test patterns and stored in the storage unit 18. If the measured roughness of the mask pattern 103 is greater than the tolerance for the roughness of the pattern of the material to be etched (metal film) 102, the protective film 104 can be formed to reduce the roughness of the mask pattern 103 to or below the tolerance for the roughness of the pattern of the material to be etched (metal film) 102. In this way, the thickness of the protective film 104 on the mask pattern 103 formed in steps S3 and S4 is set according to the measured roughness of the mask pattern 103.

[0031] FIG. 8 shows the overall configuration of an example of a plasma processing apparatus 30 used in the present invention. The plasma processing apparatus 30 includes a processing chamber 31, a wafer stage 32, a gas supply unit 33, a bias power supply 39, a high-frequency power supply 40, a high-frequency application unit 41, and an apparatus control unit 43. The apparatus control unit 43 includes functional blocks such as a gas control unit 44, an exhaust system control unit 45, a high-frequency control unit 46, a bias control unit 47, a protective film formation process control unit 48, an etching control unit 49, a database 50, and a memory unit 51. The control unit 52 includes a calculation unit 53 and a database storage unit 54, and by referring to the database storage unit 54, the calculation unit 53 can determine whether the desired processing has been completed. The calculation unit 53 and the database storage unit 54 of the control unit 52 may be shared with the calculation unit 19 and the storage unit 1819 of the semiconductor inspection apparatus 1 shown in FIG. 5.

[0032] The plasma processing 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 57 from the apparatus control unit 43, a protective film forming gas 34, a trimming gas 35, an etching gas 36, a sidewall protective film forming gas 37, and a post-processing gas 38 are each supplied to the processing chamber 31 according to the processing step.

[0033] The process gas supplied to the process chamber 31 is decomposed into plasma 42 within the process chamber 31 by radio frequency power 56 applied to the radio frequency application unit 41 from the radio frequency power supply 40 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 42 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 42 are accelerated by a bias voltage 55 applied to the wafer stage 32 from the bias power supply 39 controlled by the bias control unit 47, and are irradiated onto the surface of the wafer 100.

[0034] Next, as an example of the etching method of this embodiment, an example of a method for etching to reduce the roughness of the mask pattern obtained in step S1 so that it falls within the tolerance will be described below. First, as shown in FIG. 2B, a thin protective film 104 is formed on the mask pattern 103 (step S3). The thickness of the protective film 104 to be formed is set based on the relationship between the thickness of the protective film 104 and the roughness of the mask pattern 103, for example, as shown in FIG. 9B.

[0035] As an example, a method for improving the roughness of a mask by forming a thin film containing C as a protective film 104 on a mask pattern 103 will be described with reference to Fig. 2. In this example, the mask pattern 103 is made of SiN and the material to be etched (metal film) 102 is made of Ru. The material of the mask pattern 103 is SiO ２ , Si ３ N ４ , SiC, etc., materials containing C, O, N in addition to Si, TiN, TiO２ Materials containing Ti such as Al ２ O ３ The same can be applied to materials containing Al or Ta, such as TaN, and materials containing C.

[0036] First, the wafer 100 is introduced onto the wafer stage 32 in the processing chamber 31, and as the conditions for processing the mask pattern 103 formed on the wafer 100, the processing conditions for the protective film formation process stored in the database storage unit 54 in the control unit 52 are transmitted to the device control unit 43 based on the roughness measured in step S1 and the roughness tolerance determined in step S2.

[0037] When the protective film forming process (step S3) is started, the protective film forming gas 34 is supplied to the processing chamber 31 at a predetermined flow rate based on a control signal 57 from the apparatus control unit 43. The supplied protective film forming gas 34 is converted into plasma 42 by high-frequency power 56 applied to the high-frequency application unit 41, generating radicals and ions. The radicals and ions generated from the protective film forming gas 34 have the property of bonding with or adhering to the material of the mask pattern 103 and depositing thereon. The radicals and ions generated by the plasma 42 reach the surface of the wafer 100 and form a protective film 104 containing C on the upper surface and sidewalls of the mask pattern 103. The protective film forming process control unit 48 can control the thickness and quality of the protective film 104 by setting and adjusting the flow rate of the protective film forming gas 34, the high-frequency power applied to the high-frequency application unit 41, the substrate temperature, the plasma irradiation time, etc.

[0038] The protective film forming gas 34 is, for example, CH ４ , C.F. ４ , CHF ３ , C.H. ３ F, C ４ F ８ , CO ２ , a C-containing gas such as CO, COS gas, or the above gases in combination with Ar, He, O ２ Gas, CO ２ Gas, CO gas, COS gas, SO ２ Gas, N ２ , H ２The protective film forming gas 34 may be, for example, HBr gas, BCl ３ Gas, SO ２ Gas or the above gas with Ar, He, O ２ Gas, CO ２ Gas, CO gas, COS gas, SO ２ Gas, N ２ , H ２ In this case, radicals and ions generated by plasma 42 from the gas react with the material of mask pattern 103 to form a thin film as protective film 104. The thickness of protective film 104 can be adjusted by the plasma irradiation time, the gas flow rate of protective film forming gas 34, the substrate temperature, etc. Alternatively, the reactivity of the generated radicals and ions with the material surface can be adjusted by adjusting the degree of plasma dissociation using high-frequency power 56 applied to high-frequency application unit 41, thereby adjusting the thickness of protective film 104.

[0039] After the protective film 104 is formed in step S3, a portion of the protective film is removed and trimmed (step S4). An example of a cross section of the pattern after trimming is shown in FIG. 2C. After the protective film 104 is formed, trimming is further performed to remove a portion of the protective film 104, thereby smoothing the shape of the protective film 104 and reducing the roughness of the pattern and the roughness of the protective film surface, while also allowing the desired mask dimensions to be obtained.

[0040] Based on a control signal from the protective film forming process control unit 48, the protective film trimming gas 35 is supplied to the processing chamber 31 at a predetermined flow rate, and is turned into plasma 42 by high-frequency power 56 applied to the high-frequency application unit 41, thereby generating radicals and ions. The radicals and ions generated from the protective film trimming gas 35 react with the material of the protective film 104 or remove part of the material of the protective film 104 by sputtering, thereby reducing the roughness of the pattern and the roughness of the protective film surface.

[0041] When the protective film 104 is made of a material containing a large amount of C, the trimming gas 35 may be, for example, argon gas (Ar), helium gas (He), or O ２ Gas, CO ２Gas, CO gas, COS gas, SO ２ Gas, nitrogen gas (N ２ ), hydrogen gas (H ２ ) or NF ３ , C.F. ４ , CHF ３ , S.F. ６ Gases containing F such as the above can be used.

[0042] The roughness of the protective film 104 can be adjusted by the plasma irradiation time, the gas flow rate of the protective film trimming gas 35, the substrate temperature, etc. Alternatively, the reactivity of the generated radicals and ions with the material surface can be adjusted by adjusting the degree of plasma dissociation using the high-frequency power 56 applied to the high-frequency application unit 41, thereby adjusting the film thickness, film quality, and roughness of the protective film 104. Alternatively, the energy of ions incident on the surface of the wafer 100 can be controlled by adjusting the bias voltage 55 applied to the wafer stage 32 by the bias power supply 39, thereby adjusting the film thickness, film quality, and roughness of the protective film 104.

[0043] In this embodiment, trimming (step S4) was performed after forming the protective film (step S3) to obtain a pattern with roughness within a specified range, but trimming of the mask pattern 103 may be performed before forming the protective film to reduce roughness, and then the protective film 104 may be formed, or either of the protective film formation and trimming processes may be performed. Furthermore, after performing trimming (step S4) after forming the protective film (step S3), a pattern inspection similar to step S1 may be performed to confirm whether a protective film with the desired dimensions and roughness has actually been formed on the mask pattern.

[0044] When the mask roughness satisfies the specified roughness and a mask pattern with desired dimensions is obtained, etching of the material to be etched (metal film) 102 is carried out (step S5).

[0045] Based on a control signal 57 from the device control unit 43, the etching gas 36 is supplied to the processing chamber 31 at a predetermined flow rate. The supplied etching gas 36 is turned into plasma 42 by high-frequency power 56 applied to the high-frequency application unit 41, generating radicals and ions that etch the material to be etched (metal film) 102. The radicals and ions generated by the plasma 42 reach the surface of the wafer 100, and as shown in FIG. 2(d), start etching the material to be etched (metal film) 102 using the mask pattern 103 and the protective film 104 as a mask. The etching gas 36 may be, for example, Cl. ２ , HBr, NF ３ , S.F. ６ or a gas containing a halogen gas such as O ２ The etching gas 36 may be a mixture of CF4 or other gases. ４ , CHF ３ Fluorocarbon gas, hydrofluorocarbon gas and O ２ A mixed gas such as a gas containing ions and a fluorine-containing gas may also be used. Ions generated from the etching gas 36 are accelerated by a bias voltage 55 applied to the wafer stage 32 from a bias power supply 39 controlled by a bias control unit 47, and are then irradiated onto the surface of the wafer 100.

[0046] Here, in the etching in step S5, etching may proceed toward the sidewalls of the material to be etched (metal film) 102, which may result in failure to obtain the desired metal pattern shape or increased roughness. In particular, as shown in FIG. 4( b), when many grain boundaries of the material to be etched (metal film) 102 are present on the sidewalls of the pattern, etching tends to proceed more easily at those boundaries than within the grains, which may result in increased roughness. In such cases, for example, as shown in FIG. 2( e), the increase in roughness can be suppressed by forming a sidewall protective film 105 on the sidewalls of the pattern of the material to be etched (metal film) 102.

[0047] Methods for forming the sidewall protective film 105 during etching of the material to be etched (metal film) 102 include a method of etching by adding a gas having a sidewall protective effect to the etching gas for the material to be etched (metal film) 102 described in step S5, and a method of performing a step of forming the sidewall protective film 105 (step S6) after the etching step of the layer to be etched (step S5), and performing steps S5 and S6 in a cycle.

[0048] As a method for adding a gas having a sidewall protection effect to the etching gas for the material to be etched (metal film) 102, for example, Cl ２ Gas and O ２ CH ４ There is a method for forming a C-based protective film on the sidewall using a highly depositing gas such as HBr gas or CO ２ Gas, COS gas, N ２ Gas, SO ２ By adding a gas or the like, it reacts with the sidewall of the material to be etched (metal film) 102 to form a reaction film with low volatility, thereby preventing etching of the sidewall.

[0049] When the step of forming the sidewall protective film 105 (step S6) is performed, the sidewall protective film forming gas 37 is supplied to the processing chamber 31 at a predetermined flow rate based on a control signal from the protective film forming process control unit 48, and the sidewall protective film forming gas 37 is turned into plasma 42 by the high-frequency power 56 applied to the high-frequency power applying unit 41, generating radicals and ions. The radicals and ions generated from the sidewall protective film forming gas 37 have the property of bonding with or adhering to the material to be etched (metal film) 102 and depositing thereon. The radicals and ions generated by the plasma 42 reach the surface of the wafer 100 and form the sidewall protective film 105 on the upper surface and sidewalls of the mask pattern 103 and on the sidewalls (sidewall surfaces) of the pattern of the material to be etched (metal film) 102. The protective film forming process control unit 48 can control the film thickness and film quality of the sidewall protective film 105 by setting and adjusting the flow rate of the sidewall protective film forming gas 37, the high-frequency power 56 applied to the high-frequency power applying unit 41, the substrate temperature, the plasma irradiation time, etc.

[0050] The sidewall protective film forming gas 37 is, for example, CH ４ , C.F. ４ , CHF ３ , C.H. ３ F, C ４ F ８ , CO ２ , C-containing gas such as CO, HBr gas, BCl ３ Gas, COS gas, SO ２ Gas or the above gas with Ar, He, O ２ Gas, CO ２ Gas, CO gas, COS gas, SO ２ Gas, N ２ , H ２ A mixed gas such as the above can be used. On the side walls of the material to be etched (metal film) 102, radicals and ions generated by plasma 42 due to the gas react with the material of the material to be etched (metal film) 102 to form a thin film as a sidewall protective film 105. The thickness of the sidewall protective film 105 can be adjusted by the plasma irradiation time, the gas flow rate of the sidewall protective film forming gas 37, the substrate temperature, etc. Alternatively, the thickness of the sidewall protective film 105 can be adjusted by adjusting the degree of plasma dissociation using the high-frequency power 56 applied to the high-frequency application unit 41, thereby adjusting the reactivity of the generated radicals and ions with the material surface.

[0051] After the sidewall protective film 105 is formed, Ar gas, He gas, N ２ Gas, H ２ The shape of the sidewall protective film 105 may be smoothed by introducing a gas such as a gas and irradiating the groove pattern with plasma, thereby reducing the roughness of the groove pattern and the roughness of the surface of the sidewall protective film.

[0052] After etching of the material to be etched (metal film) 102 (step S7) is completed, pattern inspection is performed (step S8). As an example, a case where the post-etching pattern shown in FIG. 2(f) is inspected using the semiconductor inspection device 1 will be described. After the pattern of the material to be etched (metal film) 102 is formed, the wafer 100 is irradiated with an electron beam having an energy sufficient to penetrate the mask pattern 103 and reach the pattern of the material to be etched (metal film) 102. Secondary electrons and backscattered electrons generated from the surface of the wafer 100 by the electron beam scanning are detected by the secondary electron detector 11 and the backscattered electron detector 12, and are amplified by the amplifier 13. The electronic signal amplified by the amplifier 13 is displayed as a scanned image on the monitor 16 by the controller 4.

[0053] FIG. 7 illustrates an example of a method for inspecting a wafer after forming an etched pattern. The secondary electron detector 11 detects components primarily consisting of secondary electrons, acquires a secondary electron image 120 as shown in FIG. 7( a), and measures the dimensions and roughness of the mask pattern. Meanwhile, the backscattered electron detector 12 detects components primarily consisting of backscattered electrons, acquires a backscattered electron image 121 as shown in FIG. 7( b), and measures grain information such as the width dimension of the pattern of the material to be etched (metal film) 102, sidewall roughness, and grain size of the metal pattern, the length of the grain boundary passing through the wiring pattern, and crystal orientation. When the pattern of the material to be etched (metal film) 102 is particularly fine, and it is difficult to evaluate the grain after etching the material to be etched (metal film) 102, the grain boundaries can be accurately determined by pattern matching with the image of the grain of the material to be etched (metal film) 102 before pattern processing, measured in step S1. The secondary electron image 120 and reflected electron image 121 acquired in step S8, the measured pattern dimensions, roughness and grain information of the material to be etched (metal film) 102, and the dimensions and roughness of the mask pattern 103 are stored in the storage unit 18.

[0054] Thereafter, it is determined whether the roughness of the pattern of the processed etched material (metal film) 102 is equal to or less than a predetermined tolerance (step S9). If it is not within the predetermined tolerance, the specified value of the mask pattern 103 is corrected. If the roughness after pattern formation of the etched material (metal film) 102 is increased compared to the roughness value of the mask pattern 103 measured in step S1 and stored in the storage unit 18, this can be fed back to the conditions of the protective film formation process (step S3), trimming (step S4), etching (steps S5 and S7), and sidewall protective film formation (step S6). For example, even if the roughness of the mask pattern 103 measured in step S1 was within the tolerance, if the pattern dimensions of the etched material (metal film) 102 after processing are smaller than the desired value and the roughness increases, and if the roughness of the mask after the sidewall protective film formation is not within the tolerance, the conditions of the sidewall protective film formation process (step S6) can be corrected to reduce the roughness of the pattern of the etched material (metal film) 102 to the tolerance. For example, as shown in FIG. 10 , if the relationship between the roughness of the pattern of the material to be etched (metal film) 102 after processing and the thickness of the formed sidewall protective film or the time for forming the sidewall protective film is acquired and stored in the storage unit 18, the conditions for processing the next wafer can be corrected to a condition in which the thickness of the sidewall protective film is increased by ΔH, thereby making it possible to reduce the roughness of the pattern of the material to be etched (metal film) 102 after processing to within an allowable value and avoid the production of defective patterns.

[0055] Alternatively, if the pattern dimensions of the etched material (metal film) 102 after processing are larger than the desired value but the roughness is within the tolerance, the dimensions of the etched pattern material (metal film) 102 after processing can be fine-tuned by shortening the time for forming the protective film (step S3) and the sidewall protective film (step S6) and lengthening the time for trimming (step S4).

[0056] Next, the wiring resistance is estimated (step S10) from the roughness, dimension, and grain information of the pattern of the material to be etched (metal film) 102 obtained in the pattern inspection (step S8) performed after processing the material to be etched (metal film) 102. The pattern dimension, roughness, and grain information of the material to be etched (metal film) 102 stored in the storage unit 18 is sent to the calculation unit 19, which estimates the wiring resistance after processing and calculates the specified roughness value. The wiring resistance can be calculated according to the effective resistance value of the wiring that takes into account scattering at side walls and scattering at grain boundaries shown in the above-mentioned (Equation 1). The wiring width d after metal pattern processing can be calculated from the pattern dimension of the material to be etched (metal film) 102 in the backscattered electron image 121. The sidewall scattering coefficient p varies depending on the roughness of the wiring, and can therefore be calculated from the roughness of the pattern of the material to be etched (metal film) 102 measured from the backscattered electron image 121. The grain size coefficient D can be determined from the grain size of the material to be etched (metal film) 102 in the reflected electron image 121. After the wiring resistance is estimated, it is confirmed whether the resistance value is within a desired resistance value range.

[0057] Once it is confirmed that the estimated resistance value is within the desired resistance value range, the sidewall protective film 105 and etching residues are removed (step S11). For example, if the sidewall protective film 105, the oxidized material to be etched 102, or etching residues remain in the pattern grooves after etching, they may become mixed into the wiring material as impurities, increasing the wiring resistance or causing disconnection, and therefore need to be removed after etching.

[0058] In this post-processing step (step S11), first, the apparatus control unit 43 controls the gas supply unit 33 to supply the post-processing gas 38 to the processing chamber 31 at a predetermined flow rate. After the post-processing gas 38 is supplied and the interior of the processing chamber 31 reaches a predetermined pressure, the apparatus control unit 43 controls the high-frequency power supply 40 to apply high-frequency power 56 to the high-frequency application unit 41, thereby generating plasma 42 from the post-processing gas 38 inside the processing chamber 31. The post-processing gas 38 becomes plasma 42, generating radicals and ions that remove the sidewall protective film 105, oxide film, and etching residue on the material to be etched (metal film) 102. The etching residue can be referred to as an altered layer. For example, H ２ A gas mixture containing H ２ Gas and N ２ Alternatively, it can be removed by treating with a gas mixture containing F for a short period of time.

[0059] According to the present invention, it is possible to obtain information on the dimensions, roughness, and grain of the wiring pattern under the mask nondestructively before processing the film to be etched. Furthermore, the wiring resistance can be estimated based on the measured information on the dimensions, roughness, and grain size of the mask pattern. Furthermore, it is possible to set and perform optimal etching conditions based on the measured information, and by performing etching that reduces the roughness of the wiring pattern to a specified tolerance or less, it is possible to perform etching that ensures wiring resistance, thereby reducing the number of wafers to be discarded. Furthermore, it is possible to estimate optimal etching conditions based on the measured information, create a wiring pattern with low wiring resistance, and provide a high-performance device.

[0060] Although the present invention has been specifically described above 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.

[0061] 1: Semiconductor inspection device, 2: Electronics system, 3: Stage, 4: Control unit, 5: Electron source, 7: Scanning control unit, 8: Scanning coil, 9: Condenser lens, 10: Objective lens, 11: Secondary electron detector, 12: Backscattered electron detector, 13: Amplification unit, 14: Conversion unit, 15: Detector control unit, 16: Monitor, 17: Operation board, 18: Storage unit, 19: Calculation unit, 20: Stage control unit, 21: External server, 30: Plasma processing device, 31: Processing chamber, 32: Wafer stage, 33: Gas supply unit, 34: Protective film forming gas, 35: Trimming gas, 36: Etching gas, 37: Sidewall protective film forming gas, 38: Post-processing gas, 39: Bias power supply, 40: High frequency power supply, 41: High frequency application unit, 42: Plasma: 43: Device control unit, 44: Gas control unit, 45: Exhaust system control unit, 46: High frequency control unit, 4 7: Bias control unit, 48: Protective film formation process control unit, 49: Etching control unit, 50: Database, 51: Memory unit, 52: Control unit, 53: Calculation unit, 54: Database storage unit, 55: Bias voltage, 56: High frequency power, 57: Control signal, 100: Wafer, 101: Substrate, 102: Material to be etched (metal film), 103: Mask pattern, 104: Protective film, 105: Side wall protective film, 111: Mask pattern dimensions, 112: Roughness of side walls of mask pattern, 113: Pattern dimensions of material to be etched (metal film), 114: Roughness of side walls of pattern of material to be etched (metal film), 115: Grain of material to be etched (metal film), 116: Incident electron beam, 117: Secondary electrons, 118: Incident electron beam, 119: Reflected electrons, 120: Secondary electron image, 121: Reflected electron image.

Claims

1. A plasma processing method for forming a metal film pattern, comprising: a first step of acquiring information on roughness and dimensions of a mask pattern and grain of the metal film from an image of the mask pattern acquired using an electron beam; a third step of defining etching conditions for the metal film based on an allowable value for the roughness of the metal film pattern; and a fourth step of etching the metal film using the defined etching conditions.

2. A plasma processing method according to claim 1, further comprising a second step of determining a tolerance for the roughness of the metal film pattern corresponding to a desired wiring resistance based on the acquired information on the roughness and dimensions of the mask pattern and the grain of the metal film.

3. A plasma processing method according to claim 2, wherein the specified etching conditions for the metal film include a step of forming a protective film on the mask pattern.

4. The plasma processing method according to claim 2, wherein the specified etching conditions for the metal film include a step of forming a protective film on a side wall of the metal film.

5. The plasma processing method according to claim 2, wherein the metal film is made of ruthenium (Ru).

6. A plasma processing method according to claim 1, further comprising a second step of estimating a resistance value of the wiring of the metal film based on the measurement results of the roughness and dimensions of the mask pattern and the grain size of the metal film.

7. A method for inspecting a metal film pattern, comprising: irradiating an electron beam from above a mask pattern for forming the metal film pattern, thereby measuring the roughness and dimensions of the mask pattern and the grain size of the metal film; and estimating a resistance value of the wiring of the metal film based on the measurement results.

8. A method for inspecting a metal film pattern, comprising: a first step of acquiring information on the roughness and dimensions of a mask pattern and the grain of the metal film from an image of the mask pattern acquired using an electron beam; and a second step of determining an allowable value for the roughness of the metal film pattern corresponding to a desired wiring resistance based on the acquired information on the roughness and dimensions of the mask pattern and the grain of the metal film.

Images