Etching method and plasma processing apparatus

Abstract

An etching method and a plasma processing apparatus capable of maintaining the uniformity of an etched surface in-plane well are provided. The etching method includes a first etching step of etching a first silicon-containing film of a substrate with a plasma of a first processing gas, and a second etching step of etching a second silicon-containing film of the substrate with a plasma of a second processing gas. The etching method repeats the first etching step to the second etching step a predetermined number of times.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to an etching method and a plasma processing apparatus. BACKGROUND

[0002] In manufacturing of three-dimensional laminated semiconductor memories such as 3D NAND flash memories, there is a step of etching a multilayer film into a stepped shape using plasma. Patent Literature 1 discloses a technique in which etching of a multilayer film on which a mask is formed and trimming of the mask on the multilayer film are alternately performed to etch the multilayer film into a stepped shape.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2013-183063 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present application provides a technique capable of maintaining in-plane uniformity to perform etching well.

[0008] TECHNICAL SOLUTION FOR SOLVING THE PROBLEMS

[0009] An etching method of one embodiment of the present application is an etching method of etching a substrate in which a plurality of first silicon-containing films and second silicon-containing films are alternately laminated. The etching method includes a first etching step of etching the first silicon-containing film of the substrate with plasma of a first processing gas, and a second etching step of etching the second silicon-containing film of the substrate with plasma of a second processing gas. The etching method repeats the first etching step to the second etching step a predetermined number of times.

[0010] EFFECT OF THE INVENTION

[0011] According to the present application, it is possible to maintain in-plane uniformity to perform etching well. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a cross-sectional view that shows one example of a structure of a plasma processing system of an embodiment.

[0013] Figure 2 is a view that schematically shows one example of a structure of a substrate of an embodiment.

[0014] Figure 3 is a view that shows an incident angle of ions with respect to a target film.

[0015] Figure 4A is a graph that shows one example of a relationship between an incident angle of ions and an etching amount of a target film.

[0016] Figure 4B This is a graph illustrating an example of the relationship between the incident angle of ions and the etching amount of the target film.

[0017] Figure 5 This is a diagram schematically illustrating an example of the change in the step shape of a multilayer film ML caused by plasma etching.

[0018] Figure 6 This is a diagram illustrating an example of the etching result of a plasma method according to an embodiment.

[0019] Figure 7 This is a diagram showing the area etched by the plasma method according to the implementation method.

[0020] Figure 8A This is a perspective view showing an example of a step shape etched by the etching method of the embodiment.

[0021] Figure 8B This is a perspective view showing an example of a step shape etched using existing etching methods.

[0022] Figure 9A This diagram schematically illustrates the state in which each step of the stepped shape etched by the etching method of this embodiment forms a metal wiring for contact.

[0023] Figure 9B This diagram schematically illustrates the state in which the steps of a stepped shape etched using existing etching methods form contact metal wiring.

[0024] Figure 10 This is a flowchart illustrating an example of the etching method implemented in this way.

[0025] Explanation of reference numerals in the attached figures

[0026] 1. Plasma processing system

[0027] 1a Plasma processing device 1a

[0028] 1b Control Department

[0029] 71 First silicon-containing film

[0030] 72 Second silicon-containing film

[0031] W substrate. Detailed Implementation

[0032] Next, embodiments of the etching method and the plasma processing apparatus disclosed in the present application will be described in detail with reference to the accompanying drawings. Furthermore, the disclosed etching method and the plasma processing apparatus are not limited by the present embodiments.

[0033] In the case where a multilayer film in which a plurality of first silicon-containing films and second silicon-containing films are alternately laminated is etched, sometimes an etching with good in-plane uniformity of each layer is required. For example, in the case where a multilayer film formed with a step shape is etched, in order to maintain the step shape, it is desired to maintain the in-plane uniformity to perform etching well.

[0034] [Apparatus structure]

[0035] The plasma processing apparatus of the embodiments will be described. Hereinafter, the case where the plasma processing apparatus of the embodiments is taken as a plasma processing system 1 of a system configuration will be described. Figure 1 is a cross-sectional view showing one example of the configuration of the plasma processing system 1 of the embodiments.

[0036] In one embodiment, the plasma processing system 1 includes a plasma processing apparatus 1a and a control section 1b. The plasma processing apparatus 1a includes a plasma processing chamber 10, a gas supply section 20, an RF (Radio Frequency) electric power supply section 30, and an exhaust system 40. Furthermore, the plasma processing apparatus 1a includes a support section 11 and an upper electrode showerhead 12. The support section 11 is disposed in a lower region of a plasma processing space 10s inside the plasma processing chamber 10. The upper electrode showerhead 12 is disposed above the support section 11 and functions as a part of the ceiling of the plasma processing chamber 10.

[0037] The support section 11 is capable of supporting a substrate W in the plasma processing space 10s. In one embodiment, the support section 11 includes a lower electrode 111, an electrostatic chuck 112, and an edge ring 113. The electrostatic chuck 112 is disposed on the lower electrode 111 and is capable of supporting the substrate W with an upper surface of the electrostatic chuck 112. The edge ring 113 is disposed on a peripheral portion upper surface of the lower electrode 111 in a manner of surrounding the substrate W. Furthermore, although not shown, in one embodiment, the support section 11 can further include a temperature adjustment unit that adjusts at least one of the electrostatic chuck 112 and the substrate W to a target temperature. The temperature adjustment unit can include a heater, a flow path, or a combination thereof. In the flow path, a temperature adjustment fluid such as a refrigerant or a heat-conducting gas is capable of flowing.

[0038] The upper electrode showerhead 12 is capable of supplying one or more process gases from the gas supply section 20 to the plasma processing space 10s. In one embodiment, the upper electrode showerhead 12 has a gas inlet 12a, a gas diffusion chamber 12b, and a plurality of gas outlets 12c. The gas inlet 12a is in fluid communication with the gas supply section 20 and the gas diffusion chamber 12b. The plurality of gas outlets 12c is in fluid communication with the gas diffusion chamber 12b and the plasma processing space 10s. In one embodiment, the upper electrode showerhead 12 is capable of supplying one or more process gases from the gas inlet 12a to the plasma processing space 10s via the gas diffusion chamber 12b and the plurality of gas outlets 12c.

[0039] The gas supply section 20 can include one or more gas sources 21 and one or more flow controllers 22. In one embodiment, the gas supply section 20 is capable of supplying one or more process gases from the respective gas sources 21 to the gas inlet 12a via the respective flow controllers 22. Each flow controller 22 can include, for example, a mass flow controller or a pressure-controlled flow controller. Moreover, the gas supply section 20 can include one or more flow modulation devices that modulate or pulse the flow of one or more process gases.

[0040] The RF electric power supply section 30 is capable of supplying RF electric power, for example, one or more RF signals, to one or more electrodes of the lower electrode 111, the upper electrode showerhead 12, or both the lower electrode 111 and the upper electrode showerhead 12. Thereby, a plasma is generated from one or more process gases supplied to the plasma processing space 10s. Thus, the RF electric power supply section 30 functions as at least a part of a plasma generation section capable of generating a plasma from one or more process gases in a plasma processing chamber. In one embodiment, the RF electric power supply section 30 includes two RF generation sections 31a, 31b and two matching circuits 32a, 32b. In one embodiment, the RF electric power supply section 30 is capable of supplying a first RF signal from the first RF generation section 31a to the lower electrode 111 via the first matching circuit 32a. For example, the first RF signal can have a frequency in a range of 27 MHz to 100 MHz.

[0041] In addition, in one embodiment, the RF electric power supply section 30 is capable of supplying a second RF signal from the second RF generation section 31b to the lower electrode 111 via the second matching circuit 32b. For example, the second RF signal can have a frequency in a range of 400 kHz to 13.56 MHz. Alternatively, instead of the second RF generation section 31b, a DC (Direct Current) pulse generation section can be used.

[0042] Although not illustrated, other embodiments are contemplated in the present application. For example, in an alternative embodiment, the RF electric power supply section 30 can supply a first RF signal from an RF generation section to the lower electrode 111, a second RF signal from another RF generation section to the lower electrode 111, and a third RF signal from yet another RF generation section to the lower electrode 111. Further, in other alternative embodiments, a DC voltage can be applied to the upper electrode showerhead 12.

[0043] In addition, in various embodiments, the amplitude of one or more RF signals (i.e., the first RF signal, the second RF signal, etc.) can be pulsed or modulated. The amplitude modulation can include pulsing the RF signal amplitude between an on state and an off state, or between 2 or more different on states.

[0044] The exhaust system 40 can be connected to an exhaust port 10e provided, for example, at the bottom of the plasma processing chamber 10. The exhaust system 40 can include a pressure valve and a vacuum pump. The vacuum pump can include a turbo molecular pump, a roughing pump, or a combination thereof.

[0045] In one embodiment, the control section 1b processes computer executable commands that cause the plasma processing apparatus 1a to perform various steps described in the present application. The control section 1b can control each element of the plasma processing apparatus 1a so that various steps described herein are performed. In one embodiment, part or all of the control section 1b can be included in the plasma processing apparatus 1a. The control section 1b may, for example, include a computer 51. The computer 51 may, for example, include a processing section (CPU: Central Processing Unit) 511, a storage section 512, and a communication interface 513. The processing section 511 can perform various control operations based on a program stored in the storage section 512. The storage section 512 can include a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), a SSD (Solid State Drive), or a combination thereof. The communication interface 513 can communicate with the plasma processing apparatus 1a via a communication circuit such as a LAN (Local Area Network).

[0046] The plasma processing apparatus 1a including part or all of the control section 1b corresponds to the plasma processing apparatus of the present application.

[0047] The gas supply section 20 is capable of supplying various gases used for etching. For example, the gas supply section 20 is capable of supplying various gases such as fluorocarbons, hydrofluorocarbons, rare gases, oxygen-containing gases, nitrogen-containing gases, and the like. The gas supply section 20 supplies the gas to the gas diffusion chamber 12b from the gas inlet 12a. The upper electrode shower head 12 supplies the gas supplied from the gas supply section 20 to the plasma processing space 10s from the plurality of gas outlets 12c. The control section lb controls the gas supply section 20 to supply various gases into the plasma processing chamber 10.

[0048] The control section lb controls each element of the plasma processing apparatus la to perform various processes. For example, the control section lb controls the gas supply section 20, the RF electric power supply section 30, and the exhaust system 40 to perform etching.

[0049] Next, the flow of the operation of the plasma processing apparatus la of the embodiment when performing etching will be explained simply. When performing etching, the substrate W held on the transport arm is fed into the plasma processing chamber 10 from a gate valve not shown, and the substrate W is placed on the electrostatic chuck 112.

[0050] The gas supply section 20 introduces the processing gas used for etching into the plasma processing chamber 10 at a prescribed flow rate and flow rate ratio. Further, the exhaust system 40 reduces the pressure in the plasma processing chamber 10 to a set value. Also, the RF electric power supply section 30 supplies high-frequency electric power of the first RF signal and the second RF signal at prescribed powers from the two RF generating sections 31a, 31b to the lower electrode 111, respectively. The processing gas introduced in a shower from the upper electrode shower head 12 to the plasma processing space 10s is plasma-ized by the high-frequency electric power of the first RF signal of the RF electric power supply section 30. Thus, the plasma is generated in the plasma processing space 10s. The radicals and ions of the processing gas are contained in the plasma. The radicals in the plasma are supplied to the substrate W by diffusion. The ions in the plasma are attracted to the substrate W by the voltage of the high-frequency electric power generated by the second RF signal. Thus, the main surface of the substrate W is etched by the interaction of the radicals and the ions supplied from the plasma.

[0051] After the plasma etching is completed, the transport arm is fed into the plasma processing chamber 10 from a gate valve not shown. The transport arm feeds out the substrate W to the outside of the plasma processing chamber 10 and feeds in the next substrate W into the plasma processing chamber 10. By repeating this process, the substrates W can be processed continuously.

[0052] [Structure of Substrate]

[0053] Next, the structure of the substrate W of the embodiment will be explained. Figure 2This is a schematic diagram illustrating an example of the structure of a substrate W according to an embodiment. The substrate W is, for example, a semiconductor wafer. The substrate W has a multilayer film ML formed with alternating layers of multiple first silicon-containing films 71 and second silicon-containing films 72. Figure 2 In this multilayer film ML, a first silicon-containing film 71 and a second silicon-containing film 72 are alternately stacked in 21 layers. The thickness of the first silicon-containing film 71 is 50 nm or less, for example, 30 nm. The thickness of the second silicon-containing film 72 is also 50 nm or less, for example, 30 nm. However, the number of layers is not limited to this. For example, the multilayer film ML is formed by alternately stacking the first silicon-containing film 71 and the second silicon-containing film 72 in dozens to hundreds of layers. Furthermore, as the number of layers increases, the thickness of the first silicon-containing film 71 and the second silicon-containing film 72 tends to become thinner.

[0054] The first silicon-containing film 71 and the second silicon-containing film 72 are insulating films with different relative permittivity. In this embodiment, the first silicon-containing film 71 is a silicon oxide film (SiO2), and the second silicon-containing film 72 is a silicon nitride film (SiN).

[0055] However, the combination of the first silicon-containing film 71 and the second silicon-containing film 72 is not limited to the silicon oxide film / silicon nitride film described above. For example, the first silicon-containing film 71 can be a polycrystalline silicon film (doped with impurities), and the second silicon-containing film 72 can be a polycrystalline silicon film (undoped with impurities). Depending on whether doping is present, the relative dielectric constants of the first silicon-containing film 71 and the second silicon-containing film 72 can be different. Impurities used as doping impurities can include, for example, boron.

[0056] Alternatively, as a combination of the first silicon-containing film 71 and the second silicon-containing film 72, the first silicon-containing film 71 can be a silicon oxide film (SiO2), and the second silicon-containing film 72 can be a polycrystalline silicon film (doped with impurities). Furthermore, as a combination of the first silicon-containing film 71 and the second silicon-containing film 72, the first silicon-containing film 71 can also be a silicon oxide film (SiO2), and the second silicon-containing film 72 can be a polycrystalline silicon film (undoped with impurities).

[0057] In the multilayer film ML of substrate W, steps are formed in a stepped shape. Figure 2In the multilayer film ML, the first silicon-containing film 71 and the second silicon-containing film 72 are formed in a step shape by each layer. The step shape is formed, for example, by using a conventional etching technique for forming a step shape described in Patent Document 1. In each step of the step shape of the multilayer film ML, a flat portion 73 that is flat and a front end portion 74 that is a corner of each step protruding are formed. Further, in the step shape, the first silicon-containing film 71 and the second silicon-containing film 72 can be formed in a step by each plurality of layers. For example, the step shape can be such that the first silicon-containing film 71 and the second silicon-containing film 72 are formed in a step by each two layers (four layers). Further, the step shape can be formed in two directions. For example, the first silicon-containing film 71 and the second silicon-containing film 72 are formed in a step of a first step shape by each two layers (four layers). Also, with respect to each two layers (four layers), a step of a second step shape can be formed by two layers in a direction intersecting the first step shape.

[0058] Around the region where the step shape of the multilayer film ML is formed, a photoresist layer 75 that functions as a mask is formed. As a material of the photoresist layer 75, an organic film, an amorphous carbon film (a-C) can be given as an example.

[0059] However, in the case of etching the multilayer film ML in which the plurality of first silicon-containing films 71 and the second silicon-containing films 72 are alternately stacked, etching with good uniformity in the plane of each layer is sometimes required. For example, in the case of etching the multilayer film ML in which the step shape as shown in FIG. 2 is formed, in order to maintain the step shape, etching with good uniformity in the plane of each step is desired. Figure 2

[0060] Therefore, the plasma processing apparatus 1a performs etching processing of the step shape of the multilayer film ML formed on the substrate W, the etching processing including a first etching step and a second etching step, and the first etching step to the second etching step are repeated a predetermined number of times.

[0061] ​In the first etching step, the substrate W has the first silicon-containing film 71 exposed on the top surface, and the second silicon-containing film 72 under the first silicon-containing film 71. The plasma processing apparatus 1a of the present embodiment supplies the first processing gas containing a fluorocarbon compound from the upper electrode shower head 12 to the plasma processing space 10s in the first etching step. As the fluorocarbon compound, for example, C4F6, C5F8, C3F8, C4F6 can be exemplified. For example, in the first etching step, the first processing gas containing C4F6 gas is supplied from the upper electrode shower head 12 to the plasma processing space 10s, and the exposed first silicon-containing film 71 of the multi-layer film ML is etched. The first processing gas can contain argon (Ar) gas, oxygen (O2) gas, or the like. Thereby, in the first etching step, the etching rate of the first silicon-containing film 71 becomes higher than the etching rate of the second silicon-containing film 72. For example, the selectivity ratio of SiO2 / SiN becomes 5 or more. By the first etching step, the first silicon-containing film 71 exposed from the surface side is etched, and the second silicon-containing film 72 is exposed on the surface.

[0062] In the second etching step, the substrate W has the second silicon-containing film 72 exposed on the top surface, and the first silicon-containing film 71 under the second silicon-containing film. The plasma processing apparatus 1a of the present embodiment supplies the second processing gas containing a hydrofluorocarbon from the upper electrode shower head 12 to the plasma processing space 10s in the second etching step. As the hydrofluorocarbon, for example, CH2F2, CHF3, CH3F can be exemplified. For example, in the second etching step, the second processing gas containing CH2F2 gas is supplied from the upper electrode shower head 12 to the plasma processing space 10s, and the exposed second silicon-containing film 72 of the multi-layer film ML is etched. The second processing gas can contain CF4 gas, argon (Ar) gas, oxygen (O2), or the like. Thereby, in the second etching step, the etching rate of the second silicon-containing film 72 becomes higher than the etching rate of the first silicon-containing film 71. For example, the selectivity ratio of SiN / SiO2 becomes 3 or more. By the second etching step, the second silicon-containing film 72 exposed from the surface side is etched, and the first silicon-containing film 71 is exposed on the surface.

[0063] Here, in the etching of the multi-layer film ML having the step shape, the etching rate of the flat portion 73 and the tip end portion 74 of each step of the step shape of the multi-layer film ML varies depending on the processing conditions of the plasma processing. For example, depending on the pressure in the plasma processing chamber 10 in the plasma processing, the electric power value of the second RF signal applied to attract ions in the plasma, the etching rate of the flat portion 73 and the tip end portion 74 of the step shape of the multi-layer film ML varies.

[0064] For example, in plasma etching, a target film is etched by radicals, ions, or the like generated in plasma being incident to the target film. The etching amount of plasma etching has an angle dependency. Figure 3is a graph showing the incident angle of ions with respect to the target film 90. Figure 3 The incident angle θ of ions with respect to the normal direction of the target film 90 is shown in the center.

[0065] Figure 4A , Figure 4B is a graph showing an example of the relationship between the incident angle of ions and the etching amount of the target film 90. Figure 4A , Figure 4B An example of the case where the ion beam device is used experimentally, the ions generated from the fluorocarbon gas are made incident to the target film 90, the target film 90 is tilted with respect to the incident direction of the ions, and the relationship between the incident angle θ of the ions with respect to the target film 90 and the etching amount when the incident energy of the ions is made variable from VI to V4. The incident energy VI to V4 of the ions is VI > V2 > V3 > V4. Figure 4A An example of the case where the target film 90 is a silicon nitride film (Si3N4 film), Figure 4B An example of the case where the target film 90 is a silicon oxide film (SiO2 film). The etching amount of the graph is represented by a value normalized by the etching amount when the incident angle θ = 0 is 1. As described above, the etching amount of the graph varies depending on the incident angle θ of the ions, and the etching amount increases as the incident angle θ from 0° to 60 to 75°, and the etching amount sharply decreases when exceeding 60 to 75°. In addition, the difference between the etching amount when the incident angle θ is 0° and the etching amount when it is 60 to 75° can be adjusted using the incident energy of the ions, and in order to reduce the difference in etching amount, it is preferable to reduce the incident energy of the ions. In addition, Figure 4B is a graph showing the case where the film is a SiO2 film, and the same tendency is also observed for the SiO2 film.

[0066] In the plasma etching, the ions in the plasma generated in the plasma processing space 10s by the high-frequency electric power of the first RF signal are attracted to the substrate W by the voltage of the high-frequency electric power generated by the second RF signal. Thereby, the main surface of the substrate W is etched by the plasma. At this time, the incident angle θ of the ions with respect to the main surface of the substrate W is approximately 0°. In addition, the incident energy of the ions is obtained by the voltage of the high-frequency electric power, and is proportional to the electric power value of the high-frequency electric power of the second RF signal.

[0067] The front end portion 74 of the stepped shape of the multilayer film ML is formed as a protruding corner, and various normals from horizontal to vertical are obtained when the front end portion 74 (corner portion) is observed in part. That is, the incidence angle θ of the ions with respect to the flat portion 73 of each step of the stepped shape of the multilayer film ML is substantially 0°, and the incidence angle θ of the ions with respect to the front end portion 74 of the stepped shape of the multilayer film ML has various angles depending on the site. Therefore, when the electric power value of the high-frequency electric power of the second RF signal is high, the etching amount of the front end portion 74 is more than that of the flat portion 73, and the front end portion 74 is formed into a shoulder shape with a small slope. Figure 5 is a view schematically showing one example of the change in the stepped shape of the multilayer film ML caused by plasma etching. Figure 5 In the present embodiment, the change over time of the first silicon-containing film 71 exposed to the upper surface of the multilayer film ML caused by plasma etching is shown as L1 to L5. L1 shows the state of the first silicon-containing film 71 before etching. L5 shows the state of the first silicon-containing film 71 at the end of etching. Figure 5 The case where the first silicon-containing film 71 exposed to the upper surface is etched in the first etching step is shown, and the case where the second silicon-containing film 72 exposed to the upper surface is etched in the second etching step is the same. The multilayer film ML is formed into a stepped shape, and thus the etching progresses rapidly from the edge portion of the front end portion 74, and the front end portion 74 is formed into a small slope shape. In order to make the etching amounts of the flat portion 73 and the front end portion 74 of the stepped shape the same degree, it is necessary to suppress the electric power value of the high-frequency electric power of the second RF signal to be low.

[0068] Therefore, the plasma processing apparatus 1a of the present embodiment adjusts the processing conditions of plasma processing so that the etching rates of the flat portion 73 and the front end portion 74 of each stepped shape are the same in the first etching step and the second etching step. For example, the voltage of the high-frequency electric power is adjusted so that the etching rates of the flat portion 73 and the front end portion 74 of the stepped shape are the same, and the pressure in the plasma processing chamber 10 in plasma processing, the electric power value of the high-frequency electric power of the second RF signal for attracting ions in plasma is adjusted so that an appropriate voltage of the high-frequency electric power can be obtained. For example, in the first etching step, it is preferable that the pressure in the plasma processing chamber 10 in plasma processing be 30 to 150 [mTorr], and the electric power value per unit area of the high-frequency electric power of the second RF signal be 0.5 to 3.0 [W / cm 2 ], so that the voltage of the high-frequency electric power becomes 1000 to 2000 [V]. Further, in the first etching step, it is more preferable that the pressure in the plasma processing chamber 10 in plasma processing be 50 to 100 [mTorr], and the electric power value per unit area of the high-frequency electric power of the second RF signal be 1.0 to 2.5 [W / cm 2] so that the voltage of the high-frequency electric power becomes 1300 to 1800 [V]. In the second etching step, it is preferable that the pressure in the plasma processing chamber 10 in the plasma processing be 30 to 150 [mTorr], and the electric power value per unit area of the high-frequency electric power of the second RF signal applied to attract ions be 0.5 to 2.0 [W / cm 2 ] so that the voltage of the high-frequency electric power becomes 1300 to 1800 [V]. In the second etching step, it is preferable that the pressure in the plasma processing chamber 10 in the plasma processing be 30 to 150 [mTorr], and the electric power value per unit area of the high-frequency electric power of the second RF signal applied to attract ions be 0.5 to 2.0 [W / cm 2 ] so that the voltage of the high-frequency electric power becomes 1300 to 1800 [V]. In the second etching step, it is preferable that the pressure in the plasma processing chamber 10 in the plasma processing be 30 to 150 [mTorr], and the electric power value per unit area of the high-frequency electric power of the second RF signal applied to attract ions be 0.5 to 2.0 [W / cm

[0069] The plasma processing apparatus 1a repeatedly performs the first etching step and the second etching step in accordance with the number of layers of the first silicon-containing film 71 and the second silicon-containing film 72 to be etched.

[0070] Figure 6 is a diagram schematically showing one example of the etching result based on the plasma method of the embodiment. Figure 6 The example of Figure 2 The first silicon-containing film 71 and the second silicon-containing film 72 are etched by 10 layers, respectively, in a state in which the first etching step and the second etching step are repeatedly performed 10 times on the substrate W shown in Figure 7 is a diagram showing the region etched by the plasma method of the embodiment. Figure 7 In the example of Figure 2 the first etching step and the second etching step are repeatedly performed 10 times on the substrate W shown in Figure 6embodiment can etch the flat portions 73 and the front end portions 74 of the first silicon-containing film 71 of the steps of the step shape to the same degree by the first etching step, and thus can etch the first silicon-containing film 71 of the steps of the step shape flatly. Further, the plasma processing apparatus 1a of the embodiment can etch the flat portions 73 and the front end portions 74 of the second silicon-containing film 72 of the steps of the step shape to the same degree by the second etching step, and thus can etch the second silicon-containing film 72 of the steps of the step shape flatly. Thus, the plasma processing apparatus 1a of the embodiment can etch the steps of the step shape with good in-plane uniformity. In addition, the plasma processing apparatus 1a of the embodiment can etch the first silicon-containing film 71 and the second silicon-containing film 72 substantially perpendicularly in the first etching step and the second etching step. Thus, the plasma processing apparatus 1a of the embodiment can suppress changes in the positions of the steps of the step shape, and can suppress changes in the flat portions of the steps of the step shape. Figure 7 In the embodiment, the positions of the front end portions 74 of the steps of the step shape before etching and after etching are indicated by the connected broken lines Lb, and the widths of the flat portions of the step shape are indicated as CD (Critical Dimension). The plasma processing apparatus 1a of the embodiment can maintain the CD to the same degree of etching the first silicon-containing film 71 and the second silicon-containing film 72.

[0071] Here, in the conventional etching of the step shape, for example, the first silicon-containing film 71 and the second silicon-containing film 72 are etched together by plasma processing under conditions in which the etching rate of the first silicon-containing film 71 and the etching rate of the second silicon-containing film 72 are substantially equal, for example, the selectivity ratio of SiO2 / SiN is 1 degree, using a processing gas containing CF4 gas and Ar gas. However, in the conventional etching of the first silicon-containing film 71 and the second silicon-containing film 72 together, the front end portions 74 of the step shape progress faster in etching than the flat portions 73, and the front end portions 74 are formed into a shoulder shape with a small slope.

[0072] Figure 8A is a perspective view showing one example of a step shape etched by the etching method of the embodiment. Figure 8B is a perspective view showing one example of a step shape etched by the conventional etching method. Figure 8A and Figure 8B illustrates an image of a SEM (Scanning Electron Microscope). The etching method of the embodiment, as shown in Figure 8A can etch the steps of the step shape while maintaining the shapes of the steps. On the other hand, the conventional etching method, as shown in Figure 8BAs shown in FIG. 6, the front end portion 74 of the step-shaped step is formed into a shoulder shape with a small slope.

[0073] In the manufacture of three-dimensional layered semiconductor memories such as 3D NAND flash memories, metal wiring for contact is formed on each step of the step-shaped steps of the multilayer film ML of the substrate W. However, there is a problem that when the front end portion 74 of the step-shaped step is formed into a shoulder shape with a small slope as in the existing etching method, the wiring layer of the other step is conducted.

[0074] Figure 9A FIG. 6 is a diagram schematically showing a state in which the metal wiring for contact is formed on each step of the step-shaped steps etched by the etching method of the embodiment. Figure 9B FIG. 7 is a diagram schematically showing a state in which the metal wiring for contact is formed on each step of the step-shaped steps etched by the existing etching method. Figure 9A 、 Figure 9B The SiO2layer 76 is further layered on the multilayer film ML of the substrate W on which the step-shaped steps are formed, and the photoresist layer 77 formed with a pattern is layered on the ideal position of the metal wiring formed on the SiO2layer 76. Figure 9A 、 Figure 9B In FIG. 5, the position of the metal wiring 78 is indicated by a broken line. Figure 9A 、 Figure 9B In FIG. 5, the wiring layer 72a is formed on each step of the step-shaped steps by, for example, tungsten or the like. The etching method of the embodiment, as shown in FIG. 6, maintains the shape of the step-shaped steps, and the metal wiring 78 can be conducted with the wiring layer 72a of each step. On the other hand, the existing etching method, as shown in FIG. 7, forms a shoulder shape with a small slope in the front end portion 74 of the step-shaped step, and the metal wiring 78 is conducted with the wiring layer 72a of the step above or below. Figure 9A 、 Figure 9B

[0075] [Flow of etching]

[0076] Next, the flow of the etching method performed by the plasma processing apparatus 1a of the embodiment will be described. Figure 10 FIG. 8 is a flowchart showing one example of the flow of the etching method of the embodiment. Figure 10 The flow of the etching step of forming the step-shaped steps is shown.

[0077] ​The control section 1b initializes the count value n to 1 (step S10). The control section 1b controls the plasma processing apparatus 1a to perform a first etching step of etching the multilayer film ML of the substrate W disposed in the plasma processing chamber 10 with plasma of a first processing gas containing a fluorocarbon gas (step Sll). The control section 1b controls the plasma processing apparatus 1a to perform a second etching step of etching the multilayer film ML with plasma of a second processing gas containing a hydrofluorocarbon gas (step S12).

[0078] The control section 1b determines whether the value of the count value n becomes a prescribed value or more corresponding to the number of steps to be etched (step S13). In the case where the value of the count value n is less than the prescribed value (S13: No), the control section 1b increments the count value n by 1 (step S14), and shifts to the above-described step Sll.

[0079] On the other hand, in the case where the value of the count value n is the prescribed value or more (S13: Yes), the processing is ended.

[0080] [Effects]

[0081] As described above, the plasma processing apparatus 1a of the embodiment etches the substrate W in which a plurality of first silicon-containing films 71 and second silicon-containing films 72 are alternately stacked. The plasma processing apparatus 1a includes a first etching step of etching the first silicon-containing film 71 of the substrate W with plasma of a first processing gas, and a second etching step of etching the second silicon-containing film 72 of the substrate W with plasma of a second processing gas. The plasma processing apparatus 1a repeats the first etching step to the second etching step for a predetermined number of times. Thereby, the plasma processing apparatus 1a can maintain the in-plane uniformity to perform etching well.

[0082] In addition, in the multilayer film of the substrate W in which the first silicon-containing film 71 and the second silicon-containing film 72 are alternately stacked, the first silicon-containing film 71 and the second silicon-containing film 72 are formed in steps of a step shape in each layer or each plurality of layers, respectively. The plasma processing apparatus 1a exposes the first silicon-containing film 71 at the top surface of the substrate W in the first etching step. In the first etching step, the etching rate of the flat portion of the first silicon-containing film 71 of each step in the step shape is the same as the etching rate of the leading end portion of each step of the step shape of the first silicon-containing film 71. The plasma processing apparatus 1a exposes the second silicon-containing film 72 at the top surface of the substrate W in the second etching step. In the second etching step, the etching rate of the flat portion of the second silicon-containing film 72 of each step in the step shape is the same as the etching rate of the leading end portion of each step of the step shape of the second silicon-containing film 72. Thereby, it is possible to suppress the occurrence of a shoulder shape like in the conventional etching method at each step of the step shape, and it is also possible to suppress the conduction with the wiring layer of other steps in the case where a metal wiring for contact is formed.

[0083] In the first etching step, the first silicon-containing film 71 is exposed on the top surface of the substrate W, and the second silicon-containing film 72 is present just below the first silicon-containing film 71. In the first etching step, the etching rate of the first silicon-containing film 71 is higher than the etching rate of the second silicon-containing film 72. In the second etching step, the second silicon-containing film 72 is exposed on the top surface of the substrate W, and the first silicon-containing film 71 is present just below the second silicon-containing film 72. In the second etching step, the etching rate of the second silicon-containing film 72 is higher than the etching rate of the first silicon-containing film 71. Thus, the first silicon-containing film 71 can be etched well in the first etching step, and the second silicon-containing film 72 can be etched well in the second etching step.

[0084] Further, the first silicon-containing film 71 is a silicon oxide film. The second silicon-containing film 72 is a silicon nitride film. The first processing gas includes a fluorocarbon gas. The second processing gas includes a hydrofluorocarbon gas. Thus, the silicon oxide film can be etched well in the first etching step, and the silicon nitride film can be etched well in the second etching step.

[0085] The above-described embodiments are illustrative only, and the present application is not limited to the above-described embodiments. Various additions, omissions, substitutions, and modifications can be made. Further, elements in different embodiments can be combined to form other embodiments.

[0086] For example, in the above-described embodiments, the case where the multilayer film ML having a step shape is etched is described as an example, but the present application is not limited thereto. The etching method of the present embodiment can also be applied to etching of a substrate W in which a plurality of first silicon-containing films 71 and second silicon-containing films 72 are alternately stacked without forming a step shape.

[0087] Further, in the above-described embodiments, the case where the substrate W is a semiconductor wafer is described as an example, but the present application is not limited thereto. The substrate W can be any substrate as long as it is an object to be formed with a step shape.

Claims

1. An etching method for etching a substrate having multiple first silicon-containing films and second silicon-containing films alternately stacked, characterized in that, comprises: a first etching step of etching the first silicon-containing film of the substrate with a plasma of a first processing gas; and a second etching step of etching the second silicon-containing film of the substrate with a plasma of a second processing gas, the first etching step to the second etching step are repeated a predetermined number of times, of a plurality of layers of the first silicon-containing film and the second silicon-containing film alternately stacked in the substrate, the first silicon-containing film and the second silicon-containing film are formed in a stepped shape by each layer or each multiple of layers, in the first etching step, the first silicon-containing film is exposed on the top surface of the substrate, in the first etching step, the energy of ions incident on the substrate from the plasma of the first processing gas is adjusted so that the etching amount of the first silicon-containing film etched by ions having an incident angle of 0° with respect to the vertical direction of the first silicon-containing film is the same as the etching amount of the first silicon-containing film etched by ions having an incident angle of 60 to 75° with respect to the vertical direction of the first silicon-containing film, and thus the etching rate of the flat portion of the first silicon-containing film of each step in the stepped shape is the same as the etching rate of the leading end portion of each step of the stepped shape of the first silicon-containing film, in the second etching step, the second silicon-containing film is exposed on the top surface of the substrate, in the second etching step, the energy of ions incident on the substrate from the plasma of the second processing gas is adjusted so that the etching amount of the second silicon-containing film etched by ions having an incident angle of 0° with respect to the vertical direction of the second silicon-containing film is the same as the etching amount of the second silicon-containing film etched by ions having an incident angle of 60 to 75° with respect to the vertical direction of the second silicon-containing film, and thus the etching rate of the flat portion of the second silicon-containing film of each step in the stepped shape is the same as the etching rate of the leading end portion of each step of the stepped shape of the second silicon-containing film.

2. The etching method according to claim 1, wherein: in the first etching step, the first silicon-containing film is exposed on the top surface of the substrate, and the second silicon-containing film is present immediately below the first silicon-containing film, in the first etching step, the etching rate of the first silicon-containing film is higher than the etching rate of the second silicon-containing film, in the second etching step, the second silicon-containing film is exposed on the top surface of the substrate, and the first silicon-containing film is present immediately below the second silicon-containing film, in the second etching step, the etching rate of the second silicon-containing film is higher than the etching rate of the first silicon-containing film.

3. The etching method according to claim 1 or 2, wherein: the first silicon-containing film is a silicon oxide film, the second silicon-containing film is a silicon nitride film, the first processing gas contains a fluorocarbon gas, the second processing gas contains a hydrofluorocarbon gas.

4. A plasma processing apparatus, comprising: a control section, the control section controls to repeat a first etching step and a second etching step a predetermined number of times for a substrate in which a plurality of first silicon-containing films and second silicon-containing films are alternately stacked, the first etching step etches the first silicon-containing film of the substrate with plasma of a first processing gas, the second etching step etches the second silicon-containing film of the substrate with plasma of a second processing gas, of the plurality of layers of the substrate in which the first silicon-containing film and the second silicon-containing film are alternately stacked, the first silicon-containing film and the second silicon-containing film are formed in a step shape by each layer or each plurality of layers, in the first etching step, the first silicon-containing film is exposed at the top surface of the substrate, in the first etching step, the energy of ions from the plasma of the first processing gas incident to the substrate is adjusted so that the etching amount of the first silicon-containing film etched by ions having an incident angle of 0° with respect to the vertical direction of the first silicon-containing film is the same as the etching amount of the first silicon-containing film etched by ions having an incident angle of 60 to 75° with respect to the vertical direction of the first silicon-containing film, and thus the etching rate of the flat portion of the first silicon-containing film of each step in the step shape is the same as the etching rate of the leading end portion of each step of the step shape of the first silicon-containing film, in the second etching step, the second silicon-containing film is exposed at the top surface of the substrate, in the second etching step, the energy of ions from the plasma of the second processing gas incident to the substrate is adjusted so that the etching amount of the second silicon-containing film etched by ions having an incident angle of 0° with respect to the vertical direction of the second silicon-containing film is the same as the etching amount of the second silicon-containing film etched by ions having an incident angle of 60 to 75° with respect to the vertical direction of the second silicon-containing film, and thus the etching rate of the flat portion of the second silicon-containing film of each step in the step shape is the same as the etching rate of the leading end portion of each step of the step shape of the second silicon-containing film.

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