Plasma processing method and metal film pattern inspection method

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

[Technical Field]

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

[0002] As functional element products such as semiconductor devices become increasingly miniaturized and three-dimensional, three-dimensional processing technologies for various materials are becoming increasingly important in the dry etching process of semiconductor manufacturing, requiring technology that can control and process complex shapes at the atomic level. The interconnect process is also becoming increasingly miniaturized, and with the commonly used Cu (copper) interconnects, the future issue of increased interconnect resistance is becoming a problem as the interconnect width shrinks. This is because a barrier metal layer is formed between the interlayer film material and the Cu interconnect to prevent electromigration, in which metal atoms in the interconnect move due to current and lead to disconnections. However, as the interconnect width shrinks, the proportion of the barrier metal layer in the interconnect width increases dramatically, accelerating the increase in interconnect resistance.

[0003] To solve this problem, the use of Mo (molybdenum) and Ru (ruthenium) as wiring materials is being considered. These metal materials have a relatively high melting point, allowing for thinner barrier metals, 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, since wiring patterns can be formed using plasma etching or other methods, allowing for the formation of wiring patterns 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 having an energy of several hundred eV or more and several keV or less has been generally used as the incident electron beam 116. Therefore, as shown in Fig. 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 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 other than the top layer of the pattern. In transmission electron microscopy, electrons with an energy of several hundred keV are incident on a sample, and the dimensions, roughness, and grain of the pattern of the material 102 to be etched can be measured from the 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 cannot be used for the next process in the 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 enough energy 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 Figure 4(a). Using this technology, an incident electron beam 118 having enough energy 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 Figure 4(b), thereby making it possible to obtain information on the roughness 114, dimensions 113, and grain 115 of the pattern of the material 102 to be etched. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 7-27549 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-215020 [Patent Document 3] Japanese Patent Application Publication No. 2019-215788 [Non-patent literature]

[0010] [Non-Patent Document 1] RS Smith, et al., "An evaluation of Fuchs-Sondheimer and Mayadas-Shatzkes models below 14nm node wide lines," [online], February 13, 2019, AIP Advances 9, 025015 (2019), [Retrieved October 11, 2023], Internet〈URL: https: / / doi.org / 10.1063 / 1.5063896〉 [Non-patent document 2] Sara. Paolillo and 5 others, “Direct metal etch of ruthenium for advanced interconnect”, Journal of Vacuum Science and Technology B 36, 03E103 (2018) [Non-patent document 3] Shibesh Dutta, et al., “Thickness dependence of the resistivity of platinum-group metal thin films”, Journal of Applied Physics 122, 025107 (2017) [Non-patent document 4] AF Mayadas and 1 others, “Electrical-Resistivity Model for Polycrystalline Films: the Case of Arbitrary Reflection at External Surfaces”, Physical Review B 1, 1382 - Published 15 February 1970 [Non-patent document 5] Daniel Gall, “The search for the most conductive metal for narrow interconnect lines”, Journal of Applied Physics 127, 050901 (2020) Summary of the Invention [Problem to be solved by the invention]

[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 onto the mask pattern 103 using a scanning electron microscope, detecting secondary electrons 117 generated from the sample surface, and acquiring 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 parts not exposed to the incident electron beam 118 and detecting a signal containing a large amount of reflected electrons 119 secondarily generated from the part 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. For this reason, it is not possible to process the material to be etched 102 to the appropriate dimensions 113 and roughness 114 based on 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, and to control the pattern shape and electrical characteristics.

[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. [Means for solving the problem]

[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. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing an example of a process flow of a plasma processing method according to an embodiment of the present invention; [Figure 2] 1A to 1C are explanatory diagrams of cross-sectional structures of samples in the flow of the plasma processing method of the present embodiment. [Figure 3] 1A and 1B are explanatory diagrams for explaining the problems of the conventional method, in which (a) is a cross-sectional view of a sample on which a mask is formed after metal pattern processing, and (b) is a top view of a secondary electron image. [Figure 4] 1A and 1B are explanatory diagrams of an example of a metal pattern inspection method of the present embodiment, in which (a) is a cross-sectional view and (b) is a top view of a backscattered electron image when an electron beam capable of reaching the metal pattern is irradiated. [Figure 5] FIG. 1 is a diagram showing an example of a scanning secondary electron microscope used in pattern inspection in this embodiment. [Figure 6] 3A and 3B are diagrams showing an example of a secondary electron image and a reflected electron image of a mask pattern acquired in step 1 of this embodiment. [Figure 7] 10A and 10B are diagrams showing an example of a secondary electron image and a backscattered electron image of a pattern acquired in step 8 of this embodiment. [Figure 8] 1 is a diagram showing an example of a plasma processing apparatus to which the present embodiment is applied; [Figure 9] FIG. 2A is an explanatory diagram of a method for setting a roughness tolerance in this embodiment, and FIG. 2B is an explanatory diagram of a method for setting a protective film thickness of a mask in this embodiment. [Figure 10] 10A and 10B are diagrams illustrating a method for setting a sidewall protection film thickness according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[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 formation method of this embodiment. FIG. 2 is an example of a pattern cross-sectional view illustrating the process flow of the pattern formation 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 can be a material containing oxygen (O), nitrogen (N), and carbon (C) in addition to Si, such as silicon oxide film (SiO2), silicon nitride film (SiN), and silicon carbide (SiC: silicon carbide), a material containing titanium (Ti), such as titanium nitride (TiN: titanium nitride) and titanium dioxide (TiO2), a material containing aluminum (Al) or tantalum (Ta), such as aluminum oxide (Al2O3) and tantalum nitride (TaN), or a material containing carbon (C).

[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 measure 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 (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. An incident 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 target metal atoms, 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] A signal mainly composed of backscattered electrons can be used to obtain an image using, for example, 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 over a wafer 100 placed on a moving stage 3. Secondary electrons and backscattered electrons generated secondarily 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 control unit 15, and are displayed as a scanned image on a monitor 16 by the controller 4.

[0024] 6 shows examples of images acquired by the semiconductor inspection device 1 in the wafer inspection process (step S1) after mask formation. FIG. 6(a) shows a secondary electron image 120, which mainly captures secondary electrons, and FIG. 6(b) shows a backscattered electron image 121, which mainly captures backscattered electrons. In FIG. 6(a), secondary electrons generated in large quantities at the edge of the mask pattern 103 are acquired, allowing the dimensions and roughness of the mask pattern 103 to be measured. FIG. 6(b) 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 information on the grains, such as the size of the grains, the length of the grain boundaries 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. 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 also 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 obtained in the pattern inspection (step S1) performed after the mask formation and the grain of the material to be etched (metal film) 102, 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] Here, Non-Patent Documents 4 and 5 disclose that the resistance of a wiring depends not only on the resistivity of the wiring material, but also on the scattering of electrons flowing in the wiring due to the roughness of the wiring sidewalls and the scattering at the grain boundaries of the wiring material. The relationship between the scattering at the sidewalls, the scattering at the grain boundaries, and the effective resistance value of the wiring can be expressed as follows (Equation 1). ρ= ρ0+ ρ0λ * 3(1 - p) / 4d + ρ0λ* 3R / 2D(1 - R) ···(1) Here, 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. The effective volume resistivity ρ of the wiring pattern can be calculated by 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 roughness of the wiring, and can be determined from the roughness of the mask pattern 103 measured from the secondary electron image 120. The grain size coefficient D can be determined from the grain size of the material to be etched (metal film) 102 obtained from the reflected electron image 121.

[0028] After the calculation unit 19 estimates the wiring resistance, it checks 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, 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, FIG. 9(a) shows the relationship between wiring resistance and roughness as an explanatory diagram of a method for setting the tolerance for the pattern roughness of the material to be etched (metal film) 102. For example, as shown in FIG. 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 by using a relationship previously obtained using a test pattern, or by calculation using 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. FIG. 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 gas cylinders and valves, 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 in 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. 2(b), 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. 9(b).

[0035] As an example, a method for improving mask roughness 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 case where the material of the mask pattern 103 is SiN and the material to be etched (metal film) 102 is Ru will be described as an example. The same can be done with materials for the mask pattern 103 that contain C, O, and N in addition to Si, such as SiO2, Si3N4, and SiC, materials containing Ti, such as TiN and TiO2, materials containing Al and Ta, such as Al2O3 and TaN, and materials containing C.

[0036] First, the wafer 100 is introduced onto the wafer stage 32 in the processing chamber 31, and 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 as processing conditions for the mask pattern 103 formed on the wafer 100.

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

[0038] Examples of the protective film forming gas 34 include carbon-containing gases such as CH4, CF4, CHF3, CH3F, C4F8, CO2, and CO; COS gas; and mixtures of these gases with Ar, He, O2, CO2, CO, COS, SO2, N2, and H2. Alternatively, examples of the protective film forming gas 34 include HBr gas, BCl3 gas, and SO2 gas; and mixtures of these gases with Ar, He, O2, CO2, CO, COS, SO2, N2, and H2. In this case, radicals and ions generated by plasma 42 from these gases react with the material of the mask pattern 103 to form a thin film, which serves as the protective film 104. The thickness of the protective film 104 can be adjusted by adjusting the plasma exposure time, the flow rate of the protective film forming gas 34, the substrate temperature, and the like. Alternatively, by adjusting the degree of dissociation of the plasma using the high-frequency power 56 applied to the high-frequency application unit 41, the reactivity of the generated radicals and ions with the material surface can be adjusted, thereby adjusting the film thickness of the 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. 2(c). 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 formation 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, 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, a mixed gas of argon gas (Ar), helium gas (He), O2 gas, CO2 gas, CO gas, COS gas, SO2 gas, nitrogen gas (N2), hydrogen gas (H2), etc., or a gas containing F, such as NF3, CF4, CHF3, or SF6.

[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 wafer 100 surface 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 the mask pattern 103 may be trimmed before forming the protective film to reduce roughness, and then the protective film 104 may be formed, or either the protective film formation or trimming process may be performed. Furthermore, after trimming (step S4) is performed 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 roughness of the mask 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, an etching gas 36 is supplied to the processing chamber 31 at a predetermined flow rate. The supplied etching gas 36 is converted into plasma 42 by high-frequency power 56 applied to the high-frequency power 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), begin etching the material to be etched (metal film) 102 using the mask pattern 103 and protective film 104 as a mask. The etching gas 36 may be, for example, a gas containing a halogen gas such as Cl2, HBr, NF3, or SF6, or a mixture of such a gas with O2 gas or the like. Alternatively, a fluorocarbon gas such as CF4 or CHF3, or a mixture of a hydrofluorocarbon gas with O2 gas or the like, may also be used as the etching gas 36. 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 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 may proceed more easily at the 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] One method for adding a gas with a sidewall protection effect to the etching gas for the material to be etched (metal film) 102 is to form a C-based protective film on the sidewall by using a highly depositing gas such as CH4 gas or hydrofluorocarbon in a mixed gas of Cl2 gas and O2 gas. Alternatively, by adding HBr gas, CO2 gas, COS gas, N2 gas, SO2 gas, or the like, it reacts with the sidewall of the material to be etched (metal film) 102 to form a low-volatility reactive film, thereby preventing etching of the sidewall.

[0049] When performing the step of forming the sidewall protective film 105 (step S6), a 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. The gas is converted into plasma 42 by 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 thickness and 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] Examples of the sidewall protective film forming gas 37 include C-containing gases such as CH4, CF4, CHF3, CH3F, C4F8, CO2, and CO, HBr gas, BCl3 gas, COS gas, and SO2 gas, or mixtures of these gases with Ar, He, O2, CO2, CO gas, COS gas, SO2 gas, N2, and H2. A thin film, called a sidewall protective film 105, is formed on the sidewall of the material to be etched (metal film) 102 by reaction of radicals and ions generated by plasma 42 using the gases with the material of the material to be etched (metal film) 102. The thickness of the sidewall protective film 105 can be adjusted by adjusting the plasma irradiation time, the gas flow rate of the sidewall protective film forming gas 37, the substrate temperature, and the like. 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 power applying unit 41, thereby adjusting the reactivity of the generated radicals and ions with the material surface.

[0051] After forming the sidewall protective film 105, the groove pattern may be irradiated with plasma generated by introducing a gas such as Ar gas, He gas, N gas, or H gas, thereby smoothing the shape of the sidewall protective film 105 and 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 energy that can 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 electron 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, acquiring a secondary electron image 120 as shown in FIG. 7(a), which allows the dimensions and roughness of the mask pattern to be measured. Meanwhile, the backscattered electron detector 12 detects components primarily consisting of backscattered electrons, acquiring a backscattered electron image 121 as shown in FIG. 7(b), which allows the measurement of grain information, such as the width dimension of the pattern of the material to be etched (metal film) 102, sidewall roughness, 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, it may be difficult to evaluate the grains after etching the material to be etched (metal film) 102. By pattern matching with the image of the grains of the material to be etched (metal film) 102 before pattern processing, measured in step S1, the grain boundaries can be accurately determined. The secondary electron image 120 and backscattered 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 material to be etched (metal film) 102 is equal to or less than a predetermined tolerance (step S9). If it is not within the predetermined tolerance range, the specified value of the mask pattern 103 is corrected. If the roughness after pattern formation of the material to be etched (metal film) 102 has increased compared with 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 step (step S3), trimming (step S4), etching (steps S5 and S7), and sidewall protective film formation (step S6). For example, if the roughness of the mask pattern 103 measured in step S1 was within the tolerance, but the pattern dimensions of the processed material to be etched (metal film) 102 are smaller than the desired value, causing the roughness to increase, and if the roughness of the mask after the sidewall protective film formation is not within the tolerance, the conditions for the sidewall protective film formation process (step S6) can be corrected to reduce the roughness of the pattern of the etching 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 processed material to be etched (metal film) 102 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 sidewall protective film thickness is increased by ΔH, thereby reducing the roughness of the pattern of the processed material to be etched (metal film) 102 to the tolerance and avoiding the production of a defective pattern.

[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 information on the dimension, roughness, and grain information of the pattern 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 resistance value of the wiring can be calculated according to the effective resistance value of the wiring, which takes into account scattering at side walls and scattering at grain boundaries, as shown in the above (Equation 1). The wiring width d after metal pattern processing can be calculated from the dimension of the pattern 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, so it can 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 disconnections, and therefore need to be removed after etching.

[0058] In this post-processing step (step S11), the apparatus control unit 43 first 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 is at a predetermined pressure, the apparatus control unit 43 controls the high-frequency power supply 40 to apply high-frequency power 56 to the high-frequency application unit 41, 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, a mixed gas containing H2 gas can be used as the post-processing gas 38. Alternatively, a mixed gas of H2 gas and N2 gas can be used. Alternatively, the etching residue can be removed by short-term treatment with a mixed gas containing F.

[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. [Explanation of symbols]

[0061] 1: Semiconductor inspection equipment, 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 equipment, 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: Equipment 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. 1. A plasma processing method for forming a pattern of a metal film, comprising: a first step of acquiring information on the roughness and dimensions of the 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 defining etching conditions for the metal film based on a tolerance for pattern roughness of the metal film; and a fourth step of etching the metal film using the specified etching conditions.

2. 2. The plasma processing method according to claim 1, A plasma processing method characterized by 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. 3. The plasma processing method according to claim 2, The plasma processing method, wherein the specified etching conditions for the metal film include a step of forming a protection film on the mask pattern.

4. 3. The plasma processing method according to claim 2, 10. The plasma processing method, wherein the specified etching conditions for the metal film include a step of forming a protection film on a sidewall of the metal film.

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

6. 2. The plasma processing method according to claim 1, A plasma processing method 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 obtained.

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

8. 1. A method for inspecting a metal film pattern, comprising: a first step of acquiring information on the roughness and dimensions of the 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 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.

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