Etching method and etching apparatus

Abstract

To improve the vertical workability of a pattern formed by etching.SOLUTION: An etching method includes steps a), b), c), d), and e). In the step a), a substrate having a silicon-containing film free of oxygen and nitrogen and a mask formed on the silicon-containing film is provided. In the step b), the silicon-containing film is etched with plasma of a first processing gas containing a halogen-containing gas to form a concave portion. In the step c), an oxide film is formed in the concave portion by plasma of a second processing gas containing an oxygen-containing gas and a gas containing carbon, hydrogen, and fluorine. In the step d), after the step c), the silicon-containing film is further etched by plasma of the first processing gas. In the step e), the steps c) and d) are repeated a preset number of times. The etching method changes the thickness of the oxide film to be formed in the step e) by changing the processing conditions of at least one of the steps c) and d).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an etching method and an etching apparatus. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there is a technique for etching a silicon film of a substrate having a silicon film and a pattern mask laminated in this order from below, by using plasma of a halogen-containing gas (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-37091 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique capable of improving the vertical processability of a pattern formed by etching. [Means for solving the problem]

[0005] An etching method according to an embodiment of the present disclosure includes steps a), b), c), d), and e). Step a) is a step of providing a substrate having a silicon-containing film free of oxygen and nitrogen and a mask formed on the silicon-containing film. Step b) is a step of etching the silicon-containing film with plasma of a first processing gas containing a halogen-containing gas to form a recess. Step c) is a step of forming an oxide film in the recess with plasma of a second processing gas containing an oxygen-containing gas and a gas containing carbon, hydrogen, and fluorine. Step d) is a step of further etching the silicon-containing film with plasma of the first processing gas after step c). Step e) is a step of repeatedly performing steps c) and d) a preset number of times. In the etching method, in step e), the thickness of the oxide film to be formed is changed by changing the processing conditions of at least one of steps c) and d). Effect of the Invention

[0006] According to the present disclosure, an effect is achieved in that the vertical processability of a pattern formed by etching can be improved. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a flowchart showing an example of the flow of an etching method according to an embodiment. [Figure 2A] FIG. 2A is a diagram showing an example of a state of a substrate in each step of the etching method according to the embodiment. [Figure 2B] FIG. 2B is a diagram showing an example of a state of the substrate in each step of the etching method according to the embodiment. [Figure 2C] FIG. 2C is a diagram showing an example of a state of the substrate in each step of the etching method according to the embodiment. [Figure 2D] FIG. 2D is a diagram showing an example of a state of a substrate in each step of the etching method according to the embodiment. [Figure 2E] FIG. 2E is a diagram showing an example of a state of a substrate in each step of the etching method according to the embodiment. [Diagram 3] FIG. 3 is a diagram illustrating an example of an oxide film forming step. [Figure 4] FIG. 4 is a diagram illustrating an example of an oxide film forming step. [Diagram 5] FIG. 5 is a diagram illustrating an example of an oxide film forming step. [Figure 6] FIG. 6 is a diagram showing an example of conditions used in the etching method according to the embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of an etching apparatus according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Various embodiments will be described in detail below with reference to the drawings. Note that the disclosed technology is not limited to the following embodiments.

[0009] In the following description of the embodiments, when describing the direction of a pattern formed on a substrate, a direction substantially perpendicular to the substrate surface is referred to as a thickness direction or a vertical direction. A direction substantially parallel to the substrate surface is referred to as a horizontal direction. In the case where the substrate is substantially disk-shaped, a direction parallel to the substrate surface from the center toward the circumference of the disk is also referred to as a radial direction.

[0010] In the following description, "pattern" refers to a shape formed on a substrate in general. A pattern refers to a hole, a trench, a line and space, a mask, and the whole of a plurality of shapes formed on a substrate. A "recess" refers to a part of a pattern formed on a substrate that is recessed in the thickness direction of the substrate. A recess has a "sidewall" which is the inner peripheral surface of the recessed shape, a "bottom" which is the bottom part of the recessed shape, and a "top" which is the substrate surface adjacent to the sidewall and continues from the sidewall. A space surrounded by the corners of the top is called an "opening". The term "opening" is also used to refer to the whole space surrounded by the bottom and sidewall of the recess or any position in the space.

[0011] Incidentally, it is known that shape abnormalities occur on the substrate when etching is performed to form a pattern with a high aspect ratio. For example, when forming a recess in the vertical direction, a shape abnormality may occur in which the inner peripheral surface of the recess bulges in the horizontal direction. Such a shape abnormality is called bowing.

[0012] On the other hand, a technique of forming a protective film on the sidewall of the recess has been proposed to suppress the occurrence of bowing. As such a technique, for example, there is a technique of forming an oxide film, which is a protective film, on the sidewall of the recess by plasma of a processing gas containing an oxygen-containing gas and a hydrofluorocarbon gas.

[0013] The position where bowing occurs is often directly below the position where the type of film formed on the substrate changes. For example, when a layer serving as a mask during etching is laminated on a silicon film to be etched, the etching rate is different between the mask and the silicon film. That is, the etching amount increases at the position where the mask switches to the silicon film, the opening bulges horizontally directly below the mask, and there is a high possibility that bowing will occur. The occurrence of bowing is a factor that deteriorates the vertical processability of the pattern formed by etching.

[0014] Therefore, a technique that can improve the vertical processability of the pattern formed by etching is expected.

[0015] (An example of the flow of the etching method according to the embodiment) FIG. 1 is a flowchart showing an example of the flow of the etching method according to the embodiment. FIGS. 2A to 2E are diagrams showing an example of the state of the substrate in each step of the etching method according to the embodiment.

[0016] First, a substrate 200 is provided (step S101, FIG. 2A). The substrate 200 has multiple stacked layers. For example, the substrate 200 has a silicon-containing film 201 and a mask 202 formed on the silicon-containing film 201 (see FIG. 2A). The silicon-containing film 201 is a silicon-containing film that does not contain oxygen or nitrogen. The mask 202 is a film having a predetermined pattern. A number of processes are performed on the substrate 200. In FIG. 1, the number of times the process is performed is indicated by "N", and is set to "N=1" at the start of the process.

[0017] Next, the silicon-containing film 201 is etched by plasma of a first process gas containing a halogen-containing gas (step S102, FIG. 2B). A pattern including a recess 300 is formed in the silicon-containing film 201 by the etching. In addition, during the process of forming the pattern on the substrate 200, by-products 250 generated by the etching are attached to the top of the pattern.

[0018] Next, an oxide film 400, which is a protective film, is formed in the recess 300 by plasma of a second process gas containing an oxygen-containing gas and a gas containing carbon, hydrogen, and fluorine (step S103, FIG. 2C). The oxide film 400 is formed so as to cover the bottom and sidewalls of the recess 300. At the same time as the formation of the oxide film 400, by-products 250 are removed from the top of the pattern by fluorine radicals contained in the plasma of the second process gas.

[0019] Here, an example of the process of forming the oxide film 400 (step S103, FIG. 2C) will be described with reference to FIG. 3 to FIG. 5. FIG. 3 to FIG. 5 are diagrams for explaining an example of the oxide film forming process. In FIG. 3 to FIG. 5, the surface Sf of the silicon-containing film 201 located in the recess 300 is shown.

[0020] 3, the silicon-containing film 201 forms a silicon crystal lattice consisting of Si-Si bonds. When plasma of the second process gas containing an oxygen-containing gas and a gas containing carbon, hydrogen, and fluorine is generated, oxygen radicals, fluorine radicals, and hydrogen radicals are dissociated from the oxygen-containing gas and the gas containing carbon, hydrogen, and fluorine. The oxygen radicals, fluorine radicals, and hydrogen radicals are adsorbed to the surface Sf of the silicon-containing film 201 located in the recess 300.

[0021] Fluorine radicals have an atomic radius smaller than the lattice distance of silicon crystals, so they penetrate from the surface Sf in the depth direction. Fluorine radicals have a higher electronegativity than oxygen radicals, so when they are adsorbed onto the surface Sf, they pull electrons from the silicon crystal lattice and form negative fluorine ions (F-). The negative fluorine ions (F-) penetrate into the silicon crystal lattice and react with the positively charged silicon. As a result, the negative fluorine ions (F-) break the Si-Si bonds and form Si-F bonds, which are ionic bonds.

[0022] 4, the fluorine radicals penetrate into the silicon-containing film 201 while forming dangling bonds of silicon and Si-F bonds. Then, oxygen, hydrogen or fluorine bonds to the dangling bonds of silicon. As a result, Si-O bonds, Si-H bonds and Si-F bonds are formed.

[0023] The bond containing oxygen forms an O-Si-O bond and is stabilized. The fluorine in the surface layer of the silicon-containing film 201 is bonded with hydrogen and removed as HF gas, and the ratio of fluorine in the surface layer of the silicon-containing film 201 is reduced. As a result, as shown in FIG. 5, a high-purity and high-quality oxide film 400 containing silicon and oxygen as main components is formed on the surface layer of the silicon-containing film 201 (i.e., the bottom and sidewall of the recess 300). In addition, in the process of forming the oxide film 400, the second process gas contains not only an oxygen-containing gas but also a gas containing carbon, hydrogen, and fluorine. In this way, in the process of forming the oxide film 400, the oxidation time can be shortened compared to the case of forming an oxide film using only O2 gas, and therefore the total etching time can be shortened. As a result, the throughput can be improved.

[0024] 1 and 2. Next, silicon-containing film 201 is further etched by plasma of the first process gas (step S104, FIG. 2D). By further etching silicon-containing film 201, recess 300 becomes deeper. By the etching, a portion of oxide film 400 covering the bottom of recess 300 is removed, and a portion covering the sidewall of recess 300 remains.

[0025] Next, it is determined whether the number of executions has reached a preset number of times (step S105). If it is determined that the number of executions has reached the preset number of times (step S105, Yes), the process ends. If it is determined that the number of executions has not reached the preset number of times (step S105, No), the number of times is updated (step S106, N=N+1), and the oxide film formation process (step S103) and the etching process (step S104) are executed again.

[0026] Thereafter, the process from step S103 to step S104 is repeated until the number of executions reaches a preset number. When the number of executions reaches the preset number, the process ends. By repeating the oxide film forming process (step S103) and the etching process (step S104), the shape shown in FIG. 2E is obtained.

[0027] 1, the process conditions of at least one of the oxide film forming process (step S103) and the etching process (step S104) which are repeatedly performed are changed so as to change the thickness of the oxide film 400 to be formed. Specifically, when the depth of the recess 300 is relatively shallow, the process conditions of at least one of the steps S103 and S104 are set so as to maximize the thickness of the oxide film 400. Then, when the depth of the recess 300 reaches a predetermined value by repeating the etching, the process conditions of at least one of the steps S103 and S104 are changed so as to reduce the thickness of the oxide film 400.

[0028] In etching, bowing often occurs at a position where mask 202 switches to silicon-containing film 201 (for example, the position indicated by R1 in FIG. 2C). The position where mask 202 switches to silicon-containing film 201 is located above an opening of a pattern including recess 300. Therefore, in the etching method according to the embodiment, the occurrence of bowing after etching is suppressed by changing the processing conditions so that the thickness of oxide film 400 is maximized when recess 300 is relatively shallow. As a result, the etching method according to the embodiment can improve the vertical processability of a pattern formed by etching.

[0029] The silicon-containing film 201 may be a silicon film, a silicon germanium film, a doped silicon film, or a laminated film including at least two films selected from the group consisting of these films. The doped silicon film may be a boron-doped silicon film or a phosphorus-doped silicon film.

[0030] The mask 202 may be a silicon oxide film, a silicon nitride film, or a silicon carbide film. The mask 202 may contain a metal, such as tungsten (W), titanium (Ti), or hafnium (Hf).

[0031] In addition, in the etching steps of step S102 and step S104, at least one halogen-containing gas selected from the group consisting of a chlorine-containing gas and a bromine-containing gas can be used as the halogen-containing gas contained in the first processing gas. As the chlorine-containing gas, at least one chlorine-containing gas selected from the group consisting of Cl2, SiCl4, and HCl can be used. As the bromine-containing gas, at least one bromine-containing gas selected from the group consisting of HBr and Br2 can be used.

[0032] In addition, in the oxide film formation step of step S103, at least one oxygen-containing gas selected from the group consisting of O2, CO, CO2, and SO2 can be used as the oxygen-containing gas contained in the second processing gas.

[0033] In addition, in the oxide film formation step of step S103, at least one selected from the group consisting of CxHyFz (x, y, and z are natural numbers) gas, and a mixed gas containing CxFy (x and y are natural numbers) gas and H2 gas can be used as the gas containing carbon, hydrogen, and fluorine. For example, as the gas containing carbon, hydrogen, and fluorine, at least one selected from the group consisting of CH3F, CH2F2, and CHF3 can be used. Also, for example, as the gas containing carbon, hydrogen, and fluorine, CF4 gas and H2 gas can be used.

[0034] (Processing conditions for changing the thickness of the oxide film) As described above, in the etching method according to the embodiment, the thickness of the oxide film 400 to be formed is changed until the depth of the recess 300 reaches a predetermined value by repeating the etching. For example, the processing conditions are changed so that the thickness of the oxide film 400 is maximized at a stage where the depth of the recess 300 is relatively shallow.

[0035] As processing conditions to be changed in order to realize such an etching method, for example, there are the following two processing conditions. (1) Flow rate ratio of the oxygen-containing gas and the gas containing carbon, hydrogen, and fluorine in the second processing gas (2) Ratio of the processing time of the oxide film forming step (step S103) to the processing time of the etching step (step S104)

[0036] First, a case will be described in which the thickness of the oxide film 400 to be formed is changed by changing the flow rate ratio of the oxygen-containing gas to the gas containing carbon, hydrogen, and fluorine in the second process gas as a process condition. The oxide film forming process (step S103) and the etching process (step S104) are repeatedly performed at least n times (n is a natural number equal to or greater than 2).

[0037] Then, in the oxide film formation process (step S103) up to the (n-1)th time, the flow rate ratio of the gas containing carbon, hydrogen and fluorine to the oxygen-containing gas is set to a maximum value. After that, in the oxide film formation process (step S103) from the nth time onwards, the flow rate ratio of the gas containing carbon, hydrogen and fluorine to the oxygen-containing gas is changed to a value lower than the maximum value, thereby changing (reducing) the thickness of the oxide film 400 to be formed. The flow rate ratio of the gas containing carbon, hydrogen and fluorine to the oxygen-containing gas is, for example, 0.3 or less.

[0038] In this manner, by changing the flow rate ratio of the gas containing carbon, hydrogen, and fluorine to the oxygen-containing gas so that the thickness of the oxide film 400 is maximized when the depth of the recess 300 is relatively shallow, the oxide film 400 having the maximum thickness can be formed in the area where bowing is likely to occur.

[0039] Next, a case will be described in which the ratio of the processing time of the oxide film forming step (step S103) to the processing time of the etching step (step S104) is changed as a processing condition to change the thickness of the oxide film 400 to be formed. The oxide film forming step (step S103) and the etching step (step S104) are repeatedly performed at least n times (n is a natural number equal to or greater than 2).

[0040] Then, in the oxide film forming step (step S103) and the etching step (step S104) up to the (n-1)th time, the ratio of the processing time of the etching step to the processing time of the oxide film forming step is set to a minimum value. Thereafter, in the oxide film forming step and the etching step from the nth time onwards, the ratio of the processing time of the etching step to the processing time of the oxide film forming step is changed to a value higher than the minimum value, thereby changing (reducing) the thickness of the oxide film 400 to be formed. The ratio of the processing time of the etching step to the processing time of the oxide film forming step is, for example, 0.5 or more and 5.0 or less.

[0041] In this way, by changing the ratio of the processing time of the etching process to the processing time of the oxide film formation process so that the thickness of the oxide film 400 is maximized when the depth of the recess 300 is relatively shallow, the oxide film 400 of maximum thickness can be formed in the location where bowing is likely to occur.

[0042] (Example of changing processing conditions) FIG. 6 is a diagram showing an example of conditions used in the etching method according to the embodiment. In the example of FIG. 6, "number of times," "processing time (oxide film formation)," and "processing time (etching)" are set as conditions. "Number of times" indicates the number of times of processing, i.e., the number of times of processing. "Processing time (oxide film formation)" indicates the processing time of the oxide film formation step (FIG. 1, step S103) in the corresponding number of processings. "Processing time (etching)" indicates the processing time of the etching step (FIG. 1, step S104) in the corresponding number of processings.

[0043] In the example of FIG. 6, when the number of times is 1 or more and 4 or less, the ratio of the processing time of the etching process to the processing time of the oxide film formation process is set to the minimum value of 1.5 (=15 / 10). Thereafter, when the number of times is 5 or more and 40 or less, the ratio of the processing time of the etching process to the processing time of the oxide film formation process is changed to 3.5 (=35 / 10), which is higher than the minimum value. The example of FIG. 6 shows a condition in which the ratio of the processing time is set to the minimum value until the depth of the recess 300 reaches a predetermined value as the processing progresses, thereby maintaining the thickness of the oxide film 400 at the maximum thickness, and then the ratio of the processing time is reduced to reduce the thickness of the oxide film 400. Note that the condition of the ratio of the processing time used in the etching method according to the embodiment is not particularly limited. For example, a condition may be used in which the ratio of the processing time is set to the minimum value until the depth of the recess 300 reaches a predetermined value as the processing progresses, and then the ratio of the processing time is gradually reduced.

[0044] (Configuration Example of Etching Apparatus According to the Embodiment) Fig. 7 is a diagram showing an example of an etching apparatus according to an embodiment. The etching apparatus shown in Fig. 7 is a plasma processing system. An example of the configuration of the plasma processing system will be described below.

[0045] The plasma processing system includes an inductively coupled plasma processing apparatus (hereinafter, simply referred to as a plasma processing apparatus) 1 and a control unit 2. The plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing chamber 10 includes a dielectric window 101. The plasma processing apparatus 1 also includes a substrate support 11, a gas inlet unit, and an antenna 14. The substrate support 11 is disposed in the plasma processing chamber 10. The antenna 14 is disposed on or above the plasma processing chamber 10 (i.e., on or above the dielectric window 101). The plasma processing chamber 10 has a plasma processing space 10s defined by the dielectric window 101, a sidewall 102 of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 has at least one gas supply port for supplying at least one processing gas to the plasma processing space 10s, and at least one gas exhaust port for exhausting gas from the plasma processing space.

[0046] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region (substrate support surface) 111a for supporting a substrate (wafer) W, and an annular region (ring support surface) 111b for supporting the ring assembly 112. The annular region 111b of the main body 111 surrounds the central region 111a of the main body 111 in a plan view. The substrate W is disposed on the central region 111a of the main body 111, and the ring assembly 112 is disposed on the annular region 111b of the main body 111 so as to surround the substrate W on the central region 111a of the main body 111. In one embodiment, the main body 111 includes a base and an electrostatic chuck. The base includes a conductive member. The conductive member of the base functions as a lower electrode. The electrostatic chuck is disposed on the base. The upper surface of the electrostatic chuck has a substrate support surface 111a. The ring assembly 112 includes one or more annular members. At least one of the one or more annular members is an edge ring. Although not shown, the substrate support 11 may include a temperature adjustment module configured to adjust at least one of the electrostatic chuck, the ring assembly 112, and the substrate to a target temperature. The temperature adjustment module may include a heater, a heat transfer medium, a flow path, or a combination thereof. A heat transfer fluid such as brine or gas flows through the flow path. The substrate support 11 may also include a heat transfer gas supply unit configured to supply a heat transfer gas between the back surface of the substrate W and the substrate support surface 111a.

[0047] The gas introduction unit is configured to introduce at least one processing gas from the gas supply unit 20 into the plasma processing space 10s. In one embodiment, the gas introduction unit includes a center gas injector (CGI) 13. The center gas injector 13 is disposed above the substrate support 11 and attached to a central opening formed in the dielectric window 101. The center gas injector 13 has at least one gas supply port 13a, at least one gas flow path 13b, and at least one gas inlet port 13c. The processing gas supplied to the gas supply port 13a passes through the gas flow path 13b and is introduced into the plasma processing space 10s from the gas inlet port 13c. Note that the gas introduction unit may include one or more side gas injectors (SGI) attached to one or more openings formed in the sidewall 102 in addition to or instead of the center gas injector 13.

[0048] The gas supply 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply 20 is configured to supply at least one process gas from a respective gas source 21 through a respective flow controller 22 to the central gas inlet 13. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, the gas supply 20 may include one or more flow modulation devices to modulate or pulse the flow rate of the at least one process gas.

[0049] The power source 30 includes an RF power source 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power source 31 is configured to supply at least one RF signal (RF power), such as a source RF signal and a bias RF signal, to the conductive member of the substrate support 11 and the antenna 14. This causes a plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Thus, the RF power source 31 can function as at least a part of a plasma generating unit configured to generate a plasma from one or more processing gases in the plasma processing chamber 10. In addition, by supplying a bias RF signal to the conductive member of the substrate support 11, a bias potential is generated on the substrate W, and ions in the formed plasma can be attracted to the substrate W.

[0050] In one embodiment, the RF power supply 31 includes a first RF generating unit 31a and a second RF generating unit 31b. The first RF generating unit 31a is coupled to the antenna 14 and configured to generate a source RF signal (source RF power) for plasma generation via at least one impedance matching circuit. In one embodiment, the source RF signal has a frequency in the range of 13 MHz to 150 MHz. In one embodiment, the first RF generating unit 31a may be configured to generate a plurality of source RF signals having different frequencies. The generated one or more source RF signals are supplied to the antenna 14. The second RF generating unit 31b is coupled to a conductive member of the substrate support 11 via at least one impedance matching circuit and configured to generate a bias RF signal (bias RF power). In one embodiment, the bias RF signal has a lower frequency than the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 400 kHz to 13.56 MHz. In one embodiment, the second RF generating unit 31b may be configured to generate a plurality of bias RF signals having different frequencies. The generated bias RF signal or signals are supplied to conductive members of the substrate support 11. Also, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0051] The power supply 30 may also include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a bias DC generator 32a. In one embodiment, the bias DC generator 32a is connected to a conductive member of the substrate support 11 and configured to generate a bias DC signal. The generated bias DC signal is applied to the conductive member of the substrate support 11. In one embodiment, the bias DC signal may be applied to another electrode, such as an electrode in an electrostatic chuck. In various embodiments, the bias DC signal may be pulsed. It is noted that the bias DC generator 32a may be provided in addition to the RF power supply 31 or may be provided instead of the second RF generator 31b.

[0052] The antenna 14 includes one or more coils. In one embodiment, the antenna 14 may include an outer coil and an inner coil arranged coaxially. In this case, the RF power source 31 may be connected to both the outer coil and the inner coil, or to either the outer coil or the inner coil. In the former case, the same RF generator may be connected to both the outer coil and the inner coil, or separate RF generators may be connected to the outer coil and the inner coil separately.

[0053] The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure in the plasma processing space 10s is adjusted by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0054] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various steps described in the present disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform various steps described herein. In one embodiment, a part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include, for example, a computer 2a. The computer 2a may include, for example, a processing unit (CPU: Central Processing Unit) 2a1, a storage unit 2a2, and a communication interface 2a3. The processing unit 2a1 may be configured to perform various control operations based on a program stored in the storage unit 2a2. The storage unit 2a2 may include a random access memory (RAM), a read only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a local area network (LAN).

[0055] (Effects of the embodiment) The etching method according to the embodiment includes steps a), b), c), d), and e). Step a) is a step of providing a substrate (e.g., substrate 200) having a silicon-containing film (e.g., silicon-containing film 201) that does not contain oxygen and nitrogen and a mask (e.g., mask 202) formed on the silicon-containing film. Step b) is a step of etching the silicon-containing film with plasma of a first processing gas that contains a halogen-containing gas to form a recess (e.g., recess 300). Step c) is a step of forming an oxide film (e.g., oxide film 400) in the recess with plasma of a second processing gas that contains an oxygen-containing gas and a gas that contains carbon, hydrogen, and fluorine. Step d) is a step of further etching the silicon-containing film with plasma of the first processing gas after step c). Step e) is a step of repeatedly performing steps c) and d) a preset number of times. In the etching method, in step e), the thickness of the oxide film to be formed is changed by changing the processing conditions of at least one of steps c) and d). As a result, according to the embodiment, it is possible to improve the vertical processability of a pattern formed by etching.

[0056] In the etching method according to the above embodiment, the thickness of the oxide film to be formed may be changed by changing the flow rate ratio of the oxygen-containing gas to the gas containing carbon, hydrogen and fluorine in the second process gas as a process condition in step e. This allows the thickness of the oxide film to be finely adjusted according to the depth of the recess that is deepened by repeated etching.

[0057] In the etching method according to the above embodiment, in step e), steps c) and d) may be repeated at least n times (n is a natural number equal to or greater than 2). In the etching method, the flow rate ratio of the gas containing carbon, hydrogen and fluorine to the oxygen-containing gas may be set to a maximum value in the first (n-1) steps of step c). In the etching method, the thickness of the oxide film to be formed may be changed by changing the flow rate ratio to a value lower than the maximum value in the nth and subsequent steps of step c). In addition, the flow rate ratio of the gas containing carbon, hydrogen and fluorine to the oxygen-containing gas may be 0.3 or less. As a result, according to the embodiment, an oxide film with the maximum thickness can be formed in a location where bowing of the pattern is likely to occur due to etching.

[0058] In the etching method according to the above embodiment, the thickness of the oxide film to be formed may be changed by changing the ratio of the processing time of step c) to the processing time of step d) as a processing condition in step e), which allows the thickness of the oxide film to be finely adjusted according to the depth of the recess that is deepened by repeated etching.

[0059] In the etching method according to the above embodiment, in step e), steps c) and d) may be repeated at least n (n is a natural number equal to or greater than 2) times. In the etching method according to the above embodiment, the ratio of the processing time of step d) to the processing time of step c) may be set to a minimum value in steps c) and d) up to the (n-1)th time. In the etching method according to the above embodiment, the thickness of the oxide film to be formed may be changed by changing the ratio to a value higher than the minimum value in steps c) and d) from the nth time onwards. In addition, the ratio of the processing time of step d) to the processing time of step c) may be 0.5 or more and 5.0 or less. As a result, according to the embodiment, an oxide film with the maximum thickness can be formed in a location where bowing of the pattern is likely to occur due to etching.

[0060] In the above embodiment, the halogen-containing gas may be at least one halogen-containing gas selected from the group consisting of a chlorine-containing gas and a bromine-containing gas. The chlorine-containing gas may be at least one chlorine-containing gas selected from the group consisting of Cl2, SiCl4, and HCl. The bromine-containing gas may be at least one bromine-containing gas selected from the group consisting of HBr and Br2. The oxygen-containing gas may be at least one oxygen-containing gas selected from the group consisting of O2, CO, CO2, and SO2. The gas containing carbon, hydrogen, and fluorine may be at least one selected from the group of CxHyFz (x, y, and z are natural numbers) gas, and a mixed gas containing CxFy (x and y are natural numbers) gas and H2 gas. The gas containing carbon, hydrogen, and fluorine may be at least one selected from the group consisting of CH3F, CH2F2, and CHF3. The gas containing carbon, hydrogen, and fluorine may be CF4 gas and H2 gas. The silicon-containing film may be a silicon film, a silicon germanium film, a doped silicon film, or a laminated film including at least two films selected from the group consisting of these films. The doped silicon film may be a boron-doped silicon film or a phosphorus-doped silicon film. This makes it possible to improve the vertical processability of patterns formed in various silicon-containing films on a substrate by etching according to the embodiment.

[0061] Although the embodiments have been described above, the disclosed embodiments should be considered to be illustrative and not restrictive in all respects. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the claims. [Explanation of symbols]

[0062] 1. Plasma processing equipment 2. Control section 2a Computer 2a1 Processing section 2a2 Storage section 2a3 Communication Interface 10 Plasma Processing Chamber 10e Gas exhaust port 10s Plasma treatment space 11 Substrate support 13 Central gas injection section 13a Gas supply port 13b Gas flow path 13c Gas inlet 14 Antenna 20 Gas supply section 21 Gas Source 22 Flow Controller 30 power supply 31 RF power supply 31a First RF generation unit 31b Second RF generation unit 32 DC power supply 32a Bias DC generator 40 Exhaust system 101 Dielectric window 102 Side wall 111 Main body 111a Central area 111b Annular region 112 Ring Assembly 200 boards 201 Silicon-containing films 202 Mask 250 By-products 300 Recess 400 Oxide film

Claims

1. a) providing a substrate having an oxygen- and nitrogen-free silicon-containing film and a mask formed on the silicon-containing film; b) etching the silicon-containing film with a plasma of a first process gas including a halogen-containing gas to form a recess; c) forming an oxide film in the recess by plasma of a second process gas containing an oxygen-containing gas and a gas containing carbon, hydrogen and fluorine; d) after step c), further etching the silicon-containing film with a plasma of the first process gas; e) repeating steps c) and d) a preset number of times; Including, The etching method according to claim 8, wherein a thickness of the oxide film to be formed is changed by changing a flow rate ratio of the oxygen-containing gas to the gas containing carbon, hydrogen and fluorine in the second process gas.

2. a) providing a substrate having an oxygen- and nitrogen-free silicon-containing film and a mask formed on the silicon-containing film; b) etching the silicon-containing film with a plasma of a first process gas including a halogen-containing gas to form a recess; c) forming an oxide film in the recess by plasma of a second process gas containing an oxygen-containing gas and a gas containing carbon, hydrogen and fluorine; d) after step c), further etching the silicon-containing film with a plasma of the first process gas; e) repeating steps c) and d) a preset number of times; Including, In the etching method, a ratio of the treatment time of the step c) to the treatment time of the step d) is changed to change a thickness of the oxide film to be formed.

3. In the step e), the steps c) and d) are repeatedly executed at least n times (n is a natural number equal to or greater than 2); In the (n-1)th time of c), a flow rate ratio of the gas containing carbon, hydrogen and fluorine to the oxygen-containing gas is set to a maximum value; 3. The etching method according to claim 1, further comprising the step of changing the flow rate ratio to a value lower than the maximum value in the n-th or subsequent times of the etching step c) to thereby change the thickness of the oxide film to be formed.

4. 4. The etching method according to claim 1, wherein a flow rate ratio of said gas containing carbon, hydrogen and fluorine to said oxygen-containing gas is 0.3 or less.

5. In the step e), the steps c) and d) are repeatedly executed at least n times (n is a natural number equal to or greater than 2); In the (n-1)th iteration of c) and d), a ratio of the processing time of d) to the processing time of c) is set to a minimum value; 5. The etching method according to claim 1, wherein in the n-th or subsequent times of c) and d), the ratio is changed to a value higher than the minimum value, thereby changing the thickness of the oxide film to be formed.

6. 6. The etching method according to claim 1, wherein a ratio of the treatment time of said d) to the treatment time of said c) is 0.5 or more and 5.0 or less.

7. The halogen-containing gas is 7. The etching method according to claim 1, wherein the halogen-containing gas is at least one selected from the group consisting of a chlorine-containing gas and a bromine-containing gas.

8. The chlorine-containing gas is 8. The etching method according to claim 7, wherein the chlorine-containing gas is at least one selected from the group consisting of Cl2, SiCl4, and HCl.

9. The bromine-containing gas is 8. The etching method of claim 7, wherein the bromine-containing gas is at least one selected from the group consisting of HBr and Br2.

10. The oxygen-containing gas is 10. The etching method according to claim 1, wherein the oxygen-containing gas is at least one selected from the group consisting of O2, CO, CO2 and SO2.

11. The etching method according to any one of claims 1 to 10, wherein the gas containing carbon, hydrogen and fluorine is at least one selected from the group consisting of CxHyFz (x, y, and z are natural numbers) gas and a mixed gas containing CxFy (x and y are natural numbers) gas and H2 gas.

12. 11. The etching method according to claim 1, wherein the gas containing carbon, hydrogen and fluorine is at least one selected from the group consisting of CH3F, CH2F2 and CHF3.

13. 11. The etching method according to claim 1, wherein the gas containing carbon, hydrogen and fluorine is CF4 gas and H2 gas.

14. The silicon-containing film is 14. The etching method according to claim 1, wherein the etching target is a silicon film, a silicon germanium film, a doped silicon film, or a laminated film including at least two films selected from the group consisting of these films.

15. The doped silicon film is 15. The etching method according to claim 14, wherein the silicon film is a boron-doped silicon film or a phosphorus-doped silicon film.

16. a processing chamber providing a processing space; a mounting table provided inside the processing chamber and capable of mounting a substrate thereon; a gas supply unit for supplying a process gas into the processing chamber; A control unit that controls each part Equipped with The control unit is a) providing a substrate having an oxygen- and nitrogen-free silicon-containing film and a mask formed on the silicon-containing film; b) etching the silicon-containing film with a plasma of a first process gas including a halogen-containing gas to form a recess; c) forming an oxide film in the recess by plasma of a second process gas containing an oxygen-containing gas and a gas containing carbon, hydrogen and fluorine; d) after step c), further etching the silicon-containing film with a plasma of the first process gas; e) repeating steps c) and d) a predetermined number of times; Run In the step e), a flow rate ratio of the oxygen-containing gas to the gas containing carbon, hydrogen and fluorine in the second process gas is changed to change a thickness of the oxide film to be formed.

17. A process chamber providing a process space; a mounting table provided inside the processing chamber and capable of mounting a substrate thereon; a gas supply unit for supplying a process gas into the processing chamber; A control unit that controls each part Equipped with The control unit is a) providing a substrate having an oxygen- and nitrogen-free silicon-containing film and a mask formed on the silicon-containing film; b) etching the silicon-containing film with a plasma of a first process gas including a halogen-containing gas to form a recess; c) forming an oxide film in the recess by plasma of a second process gas containing an oxygen-containing gas and a gas containing carbon, hydrogen and fluorine; d) after step c), further etching the silicon-containing film with a plasma of the first process gas; e) repeating steps c) and d) a predetermined number of times; Run An etching apparatus, wherein in the step e), a ratio between the processing time of the step c) and the processing time of the step d) is changed to thereby change a thickness of the oxide film to be formed.

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