Etching method and plasma processing apparatus

Abstract

To provide a technique for protecting a mask in plasma etching of a silicon containing film.SOLUTION: An etching method disclosed comprises a step (a) for preparing a substrate in a chamber of a plasma processing apparatus. The substrate incudes a silicon containing film and a mask. The mask contains carbon. The etching method further comprises a step (b) for etching the silicon containing film using a chemical species coming from a plasma generated from a process gas in the chamber. The process gas includes halogen and phosphorus. In the step (b), binding between carbon and phosphorus is formed on a surface of the mask.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] Exemplary embodiments of the present disclosure relate to an etching method and a plasma processing apparatus. [Background technology]

[0002] In the manufacture of electronic devices, plasma etching of silicon-containing films on substrates is performed. In the plasma etching of silicon-containing films, a process gas containing a fluorocarbon gas is used. Such plasma etching is described in the following Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2016 / 0343580 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides techniques for protecting substrates during plasma etching of silicon-containing films. [Means for solving the problem]

[0005] In one exemplary embodiment, an etching method is provided. The etching method includes step (a) of providing a substrate in a chamber of a plasma processing apparatus. The substrate includes a silicon-containing film and a mask. The mask includes carbon. The etching method further includes step (b) of etching the silicon-containing film with chemical species from a plasma generated in the chamber from a process gas. The process gas includes a halogen element and phosphorus. In step (b), carbon and phosphorus bonds are formed on a surface of the mask. Effect of the Invention

[0006] According to one exemplary embodiment, a substrate can be protected during plasma etching of a silicon-containing film. [Brief description of the drawings]

[0007] [Figure 1] 1 is a flow diagram of an etching method according to an exemplary embodiment. [Diagram 2] 2 is a partially enlarged cross-sectional view of an example of a substrate to which the etching method shown in FIG. 1 can be applied. [Diagram 3] 1 is a schematic diagram illustrating a plasma processing apparatus according to an exemplary embodiment; [Figure 4] FIG. 4(a) is a partially enlarged cross-sectional view of an example substrate to which the etching method shown in FIG. 1 is applied, and FIG. 4(b) is a partially enlarged cross-sectional view of an example substrate etched by plasma generated from a processing gas that does not contain phosphorus. [Diagram 5] 4 is an example timing diagram for an etching method according to an exemplary embodiment. [Figure 6] 6(a) and 6(b) are diagrams showing the results of XPS analysis of the protective film PF formed in an experimental example in which the silicon oxide film and the silicon nitride film were etched in the process STP, respectively. [Figure 7] 5 is a timing diagram of another example of an etching method according to an exemplary embodiment. [Figure 8] FIG. 13 is a plan view of another example substrate. [Figure 9] 9(a) is a cross-sectional view taken along line IXA-IXA in FIG. 8, and FIG. 9(b) is a cross-sectional view taken along line IXB-IXB in FIG. [Figure 10] 11 is a graph showing the relationship between the flow rate of PF3 gas in the processing gas and the etching rate of a silicon oxide film, which was obtained in a first experiment. [Figure 11] 11 is a graph showing the relationship between the flow rate of PF3 gas in the processing gas and the maximum width of an opening formed in a silicon oxide film, obtained in a first experiment. [Figure 12]1 is a graph showing the relationship between the flow rate of PF3 gas in the processing gas and the selectivity obtained in a first experiment. [Figure 13] 11 is a graph showing the relationship between the flow rate of PF3 gas in the process gas and each of LER and LWR obtained in a second experiment. [Figure 14] 13 is a flow chart of an etching method (Method MT2) according to another exemplary embodiment. [Figure 15] Figures 15(a), 15(b), and 15(c) are partially enlarged cross-sectional views of an example of a substrate, respectively in the state when step ST22 of method MT2 is applied, the state when step ST23 of method MT2 is applied, and the state after method MT2 has been applied. [Figure 16] 13 is a flow diagram of an etching method (Method MT3) according to yet another exemplary embodiment. [Figure 17] 17(a) and 17(b) are partially enlarged cross-sectional views of an example of a substrate when step STP3 of method MT3 is being applied and after method MT3 has been applied, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Various exemplary embodiments are described below.

[0009] In one exemplary embodiment, an etching method is provided. The etching method includes step (a) of providing a substrate in a chamber of a plasma processing apparatus. The substrate includes a silicon-containing film and a mask. The mask includes carbon. The etching method further includes step (b) of etching the silicon-containing film with chemical species from a plasma generated in the chamber from a process gas. The process gas includes a halogen element and phosphorus. In step (b), carbon and phosphorus bonds are formed on a surface of the mask. The halogen element may be fluorine.

[0010] In the etching method of the above embodiment, the carbon-phosphorus bond formed on the surface of the mask has a higher bond energy than the carbon-carbon bond in the mask. Therefore, according to the etching method of the above embodiment, the mask is protected during plasma etching of the silicon-containing film. Therefore, according to the above embodiment, it is possible to protect the substrate during plasma etching of the silicon-containing film. Furthermore, according to the etching method of the above embodiment, deterioration of the shape of the mask during plasma etching of the silicon-containing film is suppressed.

[0011] In one exemplary embodiment, the silicon-containing film may include a silicon oxide film. The silicon-containing film may further include at least one of a silicon nitride film, a polycrystalline silicon film, a carbon-containing silicon film, and a low dielectric constant film.

[0012] In one exemplary embodiment, the mask may include a portion where the mask occupies a high proportion of the opening defined by the mask on the silicon-containing film and a portion where the mask occupies a low proportion. The portion where the mask occupies a high proportion of the opening is a portion where the mask is densely formed (hereinafter referred to as a "dense region"). The portion where the mask occupies a low proportion of the opening is a portion where the mask is sparsely formed (hereinafter referred to as a "coarse region"). In general, the mask in the coarse region is etched more than the mask in the dense region by plasma etching of the silicon-containing film. However, in this embodiment, the mask is protected by the bond between carbon and phosphorus formed on its surface. Therefore, the etching amount of the mask in the coarse region is reduced. As a result, the difference between the etching amount of the mask in the coarse region and the etching amount of the mask in the dense region is reduced. In addition, the deterioration of the shape of the mask having both the coarse region and the dense region is suppressed.

[0013] In one exemplary embodiment, the etching method may further include a step (c) of forming a protective film on a sidewall surface that defines the opening formed by etching in the step (b). The protective film includes phosphorus contained in the processing gas. Steps (b) and (c) may be performed simultaneously. The protective film may include a phosphorus-oxygen bond and / or a phosphorus-silicon bond.

[0014] In one exemplary embodiment, the process gas may include a fluorine-containing gas and a phosphorus-containing gas.

[0015] In one exemplary embodiment, the process gas may include at least one of the following phosphorus-containing molecules: PF3, PCl3, PF5, PCl5, POCl3, PH3, PBr3, and PBr5.

[0016] In one exemplary embodiment, the process gas may further include a hydrocarbon, a hydrofluorocarbon, or a fluorocarbon.

[0017] In one exemplary embodiment, a pulse wave including a pulse of an electric bias may be periodically applied to a lower electrode in a substrate support that supports the substrate in step (b). A frequency defining the period of the pulse wave may be 1 Hz or more and 100 kHz or less. A ratio of the time length during which the pulse of the electric bias is applied to the lower electrode to the time length of the period of the pulse wave may be 50% or more and 99% or less. The electric bias may be high frequency power, and the level of the high frequency power in the pulse of the electric bias may be 2 kW or more.

[0018] In one exemplary embodiment, the temperature of the substrate may be set to a temperature below 0° C. at the start of step (b).

[0019] In another exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a gas supply, and a plasma generator. The substrate support is configured to support a substrate in the chamber. The substrate includes a silicon-containing film and a mask. The mask includes carbon, and the gas supply is configured to supply a process gas into the chamber for etching the silicon-containing film. The process gas includes a halogen element and phosphorus. The plasma generator is configured to generate a plasma from the process gas in the chamber to etch the silicon-containing film and form carbon and phosphorus bonds on a surface of the mask. The halogen element may be fluorine.

[0020] In yet another exemplary embodiment, an etching method is provided. The etching method includes a step (a1) of preparing a substrate. The substrate includes a silicon-containing film and a mask disposed on the silicon-containing film. The etching method further includes a step (b1) of passivating a sidewall surface defining an opening in the silicon-containing film by supplying a phosphorus species to the substrate. The etching method further includes a step (c1) of etching the silicon-containing film by supplying a halogen species to the substrate.

[0021] In the etching method of the above embodiment, the sidewall surface of the silicon-containing film is inactivated (or passivated) by phosphorus. That is, the sidewall surface is passivated. Therefore, according to the etching method of the above embodiment, the sidewall surface is protected so as to suppress lateral etching of the silicon-containing film during plasma etching of the silicon-containing film. Therefore, according to the etching method of the above embodiment, it is possible to protect the substrate during plasma etching of the silicon-containing film.

[0022] In one exemplary embodiment, the mask may contain carbon. Step (b1) may form carbon-phosphorus bonds on the surface of the mask.

[0023] In one exemplary embodiment, the silicon-containing film may include a silicon oxide film, and step (b1) may form phosphorus and oxygen bonds on the sidewall surface.

[0024] In one exemplary embodiment, steps (b1) and (c1) may be carried out simultaneously.

[0025] In one exemplary embodiment, steps (b1) and (c1) may be repeated. Steps (b1) and (c1) may be repeated alternately.

[0026] In one exemplary embodiment, steps (b1) and (c1) may be performed with the substrate housed within a chamber of a plasma processing apparatus.

[0027] In one exemplary embodiment, the phosphorus species may be generated by generating a plasma of a phosphorus-containing gas, and the halogen species may be generated by generating a plasma of a halogen-containing gas.

[0028] In one exemplary embodiment, the halogen-containing gas may include a fluorine-containing gas, which may include at least one of hydrogen fluoride, iodine fluoride, and a fluorocarbon.

[0029] In one exemplary embodiment, the phosphorus-containing gas may be fluorine-free. In one exemplary embodiment, the phosphorus-containing gas may include PCl3 or POCl3.

[0030] In yet another exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a gas supply, a plasma generation unit, and a controller. The substrate support is configured to support a substrate in the chamber. The substrate includes a silicon-containing film and a mask disposed on the silicon-containing film. The gas supply is configured to supply a phosphorus-containing gas and a halogen-containing gas into the chamber. The plasma generation unit is configured to generate a plasma from the gases in the chamber. The controller is configured to control the gas supply and the plasma generation unit. The controller controls the gas supply and the plasma generation unit to supply the phosphorus-containing gas into the chamber and generate a plasma from the phosphorus-containing gas to generate a phosphorus species that passivates a sidewall surface that defines an opening in the silicon-containing film. The controller controls the gas supply and the plasma generation unit to supply the halogen-containing gas into the chamber and generate a plasma from the halogen-containing gas to generate a halogen species that etches the silicon-containing film.

[0031] In yet another exemplary embodiment, an etching method is provided. The etching method includes a step (a2) of providing a substrate in a chamber of a plasma processing apparatus. The substrate includes a silicon-containing film. The etching method further includes a step (b2) of etching the silicon-containing film with chemical species from a plasma generated in the chamber from a processing gas. The processing gas includes a halogen element and phosphorus.

[0032] According to the above embodiment, a protective film containing silicon and phosphorus contained in a processing gas is formed on a sidewall surface that defines an opening formed in a silicon-containing film by etching. The silicon-containing film is etched while protecting the sidewall surface by the protective film. Therefore, it is possible to suppress lateral etching in plasma etching of the silicon-containing film.

[0033] In one exemplary embodiment, the etching method may further include a step (c2) of forming a protective film on a sidewall surface defining the opening formed by etching in step (b2). The protective film includes phosphorus contained in the process gas. Steps (b2) and (c2) may occur simultaneously.

[0034] In one exemplary embodiment, the process gas may include at least one of the following phosphorus-containing molecules: PF3, PCl3, PF5, PCl5, POCl3, PH3, PBr3, and PBr5.

[0035] In one exemplary embodiment, the process gas may further include carbon and hydrogen.

[0036] In one exemplary embodiment, the process gas contains hydrogen-containing molecules such as H2, HF, C x H y , C s H t F u , and NH3, where x, y, s, t, and u are each a natural number.

[0037] In one exemplary embodiment, the halogen element may be fluorine.

[0038] In one exemplary embodiment, the process gas may further include oxygen.

[0039] In one exemplary embodiment, the silicon-containing film may be a silicon-containing dielectric film.

[0040] In one exemplary embodiment, the silicon-containing film may include at least one of a silicon oxide film, a silicon nitride film, and a silicon film.

[0041] In one exemplary embodiment, the silicon-containing film may include two or more silicon-containing films having different film types.

[0042] In one exemplary embodiment, the two or more silicon-containing films may include a silicon oxide film and a silicon nitride film. Alternatively, the two or more silicon-containing films may include a silicon oxide film and a silicon film. Alternatively, the two or more silicon-containing films may include a silicon oxide film, a silicon nitride film, and a silicon film.

[0043] In one exemplary embodiment, the substrate may further include a mask disposed over the silicon-containing film.

[0044] In one exemplary embodiment, the temperature of the substrate may be set to a temperature below 0° C. at the start of step (b2).

[0045] In yet another exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a gas supply, and a radio frequency power source. The substrate support is configured to support a substrate within the chamber. The gas supply is configured to supply a process gas into the chamber for etching a silicon-containing film. The process gas includes a halogen element and phosphorus. The radio frequency power source is configured to generate radio frequency power to generate a plasma from the process gas within the chamber.

[0046] Various exemplary embodiments will now be described in detail with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals.

[0047] 1 is a flow diagram of an etching method according to one exemplary embodiment. The etching method shown in FIG. 1 (hereinafter referred to as "Method MT") is applied to a substrate having a silicon-containing film. In Method MT, the silicon-containing film is etched.

[0048] FIG. 2 is a partially enlarged cross-sectional view of an example of a substrate to which the etching method shown in FIG. 1 can be applied. The substrate W shown in FIG. 2 can be used in the manufacture of devices such as DRAM and 3D-NAND. The substrate W has a silicon-containing film SF. The substrate W may further have an underlayer region UR. The silicon-containing film SF can be provided on the underlayer region UR. The silicon-containing film SF can be a silicon-containing dielectric film. The silicon-containing dielectric film can include a silicon oxide film or a silicon nitride film. The silicon-containing dielectric film can be a film having other film types as long as it contains silicon. The silicon-containing film SF can also include a silicon film (e.g., a polycrystalline silicon film). The silicon-containing film SF can also include at least one of a silicon nitride film, a polycrystalline silicon film, a carbon-containing silicon film, and a low-k film. The carbon-containing silicon film can include a SiC film and / or a SiOC film. The low-k film contains silicon and can be used as an interlayer insulating film. The silicon-containing film SF can also include two or more silicon-containing films having different film types. The two or more silicon-containing films may include a silicon oxide film and a silicon nitride film. The silicon-containing film SF may be, for example, a multilayer film including one or more silicon oxide films and one or more silicon nitride films that are alternately stacked. The silicon-containing film SF may be a multilayer film including a plurality of silicon oxide films and a plurality of silicon nitride films that are alternately stacked. Alternatively, the two or more silicon-containing films may include a silicon oxide film and a silicon film. The silicon-containing film SF may be, for example, a multilayer film including one or more silicon oxide films and one or more silicon films that are alternately stacked. The silicon-containing film SF may be a multilayer film including a plurality of silicon oxide films and a plurality of polycrystalline silicon films that are alternately stacked. Alternatively, the two or more silicon-containing films may include a silicon oxide film, a silicon nitride film, and a silicon film.

[0049] The substrate W may further include a mask MK. The mask MK is provided on the silicon-containing film SF. The mask MK is formed of a material having an etching rate lower than that of the silicon-containing film SF in step ST2. The mask MK may be formed of an organic material. That is, the mask MK may contain carbon. The mask MK may be formed of, for example, an amorphous carbon film, a photoresist film, or a spin-on carbon film (SOC film). Alternatively, the mask MK may be formed of a silicon-containing film such as a silicon-containing anti-reflective film. Alternatively, the mask MK may be a metal-containing mask formed of a metal-containing material such as titanium nitride, tungsten, or tungsten carbide. The mask MK may have a thickness of 3 μm or more.

[0050] The mask MK is patterned. That is, the mask MK has a pattern to be transferred to the silicon-containing film SF in step ST2. When the pattern of the mask MK is transferred to the silicon-containing film SF, an opening (recess) such as a hole or a trench is formed in the silicon-containing film SF. The aspect ratio of the opening formed in the silicon-containing film SF in step ST2 may be 20 or more, 30 or more, 40 or more, or 50 or more. The mask MK may have a line-and-space pattern.

[0051] In the method MT, a plasma processing apparatus is used for etching the silicon-containing film SF. FIG. 3 is a schematic diagram of a plasma processing apparatus according to an exemplary embodiment. The plasma processing apparatus 1 shown in FIG. 3 includes a chamber 10. The chamber 10 provides an internal space 10s therein. The chamber 10 includes a chamber body 12. The chamber body 12 has a substantially cylindrical shape. The chamber body 12 is formed of, for example, aluminum. A corrosion-resistant film is provided on the inner wall surface of the chamber body 12. The corrosion-resistant film may be formed of a ceramic such as aluminum oxide or yttrium oxide.

[0052] A passage 12p is formed in a sidewall of the chamber body 12. The substrate W is transferred between the internal space 10s and the outside of the chamber 10 through the passage 12p. The passage 12p is opened and closed by a gate valve 12g. The gate valve 12g is provided along the sidewall of the chamber body 12.

[0053] A support 13 is provided on the bottom of the chamber body 12. The support 13 is made of an insulating material. The support 13 has a generally cylindrical shape. The support 13 extends upward from the bottom of the chamber body 12 in the internal space 10s. The support 13 supports a substrate support 14. The substrate support 14 is configured to support a substrate W in the internal space 10s.

[0054] The substrate support 14 has a lower electrode 18 and an electrostatic chuck 20. The substrate support 14 may further have an electrode plate 16. The electrode plate 16 is made of a conductor such as aluminum and has a substantially disk-like shape. The lower electrode 18 is provided on the electrode plate 16. The lower electrode 18 is made of a conductor such as aluminum and has a substantially disk-like shape. The lower electrode 18 is electrically connected to the electrode plate 16.

[0055] The electrostatic chuck 20 is provided on the lower electrode 18. The substrate W is placed on the upper surface of the electrostatic chuck 20. The electrostatic chuck 20 has a body and an electrode. The body of the electrostatic chuck 20 has a substantially disk shape and is formed from a dielectric material. The electrode of the electrostatic chuck 20 is a film-like electrode and is provided in the body of the electrostatic chuck 20. The electrode of the electrostatic chuck 20 is connected to a DC power supply 20p via a switch 20s. When a voltage from the DC power supply 20p is applied to the electrode of the electrostatic chuck 20, an electrostatic attractive force is generated between the electrostatic chuck 20 and the substrate W. The substrate W is attracted to the electrostatic chuck 20 by the electrostatic attractive force and is held by the electrostatic chuck 20.

[0056] An edge ring 25 is disposed on the substrate support 14. The edge ring 25 is a ring-shaped member. The edge ring 25 may be made of silicon, silicon carbide, quartz, or the like. The substrate W is disposed on the electrostatic chuck 20 and within a region surrounded by the edge ring 25.

[0057] A flow path 18f is provided inside the lower electrode 18. A heat exchange medium (e.g., a coolant) is supplied to the flow path 18f from a chiller unit provided outside the chamber 10 via a pipe 22a. The heat exchange medium supplied to the flow path 18f is returned to the chiller unit via a pipe 22b. In the plasma processing apparatus 1, the temperature of the substrate W placed on the electrostatic chuck 20 is adjusted by heat exchange between the heat exchange medium and the lower electrode 18.

[0058] The plasma processing apparatus 1 is provided with a gas supply line 24. The gas supply line 24 supplies a heat transfer gas (for example, He gas) from a heat transfer gas supply mechanism to the gap between the upper surface of the electrostatic chuck 20 and the back surface of the substrate W.

[0059] The plasma processing apparatus 1 further includes an upper electrode 30. The upper electrode 30 is provided above the substrate support 14. The upper electrode 30 is supported on the upper part of the chamber body 12 via a member 32. The member 32 is made of an insulating material. The upper electrode 30 and the member 32 close the upper opening of the chamber body 12.

[0060] The upper electrode 30 may include a top plate 34 and a support 36. The bottom surface of the top plate 34 is the bottom surface on the side of the internal space 10s and defines the internal space 10s. The top plate 34 may be formed of a low-resistance conductor or semiconductor that generates little Joule heat. The top plate 34 has a plurality of gas discharge holes 34a penetrating the top plate 34 in its plate thickness direction.

[0061] The support 36 detachably supports the top plate 34. The support 36 is made of a conductive material such as aluminum. A gas diffusion chamber 36a is provided inside the support 36. The support 36 has a plurality of gas holes 36b extending downward from the gas diffusion chamber 36a. The plurality of gas holes 36b are connected to the plurality of gas discharge holes 34a, respectively. A gas inlet 36c is formed in the support 36. The gas inlet 36c is connected to the gas diffusion chamber 36a. A gas supply pipe 38 is connected to the gas inlet 36c.

[0062] A gas source group 40 is connected to the gas supply pipe 38 via a flow rate controller group 41 and a valve group 42. The flow rate controller group 41 and the valve group 42 configure a gas supply unit. The gas supply unit may further include a gas source group 40. The gas source group 40 includes a plurality of gas sources. The plurality of gas sources include sources of processing gases used in the method MT. The flow rate controller group 41 includes a plurality of flow rate controllers. Each of the plurality of flow rate controllers in the flow rate controller group 41 is a mass flow controller or a pressure-controlled flow rate controller. The valve group 42 includes a plurality of opening and closing valves. Each of the plurality of gas sources in the gas source group 40 is connected to the gas supply pipe 38 via a corresponding flow rate controller in the flow rate controller group 41 and a corresponding opening and closing valve in the valve group 42.

[0063] In the plasma processing apparatus 1, a shield 46 is detachably provided along the inner wall surface of the chamber body 12 and the outer periphery of the support part 13. The shield 46 prevents reaction by-products from adhering to the chamber body 12. The shield 46 is formed by forming a corrosion-resistant film on the surface of a base material made of, for example, aluminum. The corrosion-resistant film may be made of a ceramic such as yttrium oxide.

[0064] A baffle plate 48 is provided between the support 13 and the side wall of the chamber body 12. The baffle plate 48 is formed, for example, by forming a corrosion-resistant film (a film of yttrium oxide or the like) on the surface of a member made of aluminum. A plurality of through holes are formed in the baffle plate 48. An exhaust port 12e is provided below the baffle plate 48 and at the bottom of the chamber body 12. An exhaust device 50 is connected to the exhaust port 12e via an exhaust pipe 52. The exhaust device 50 includes a pressure regulating valve and a vacuum pump such as a turbo molecular pump.

[0065] The plasma processing apparatus 1 includes a high-frequency power supply 62 and a bias power supply 64. The high-frequency power supply 62 is a power supply that generates high-frequency power HF. The high-frequency power HF has a first frequency suitable for generating plasma. The first frequency is, for example, a frequency within a range of 27 MHz to 100 MHz. The high-frequency power supply 62 is connected to the lower electrode 18 via a matching device 66 and the electrode plate 16. The matching device 66 has a circuit for matching the impedance of the load side (lower electrode 18 side) of the high-frequency power supply 62 to the output impedance of the high-frequency power supply 62. The high-frequency power supply 62 may be connected to the upper electrode 30 via the matching device 66. The high-frequency power supply 62 constitutes an example of a plasma generating unit.

[0066] The bias power supply 64 is a power supply that generates an electric bias. The bias power supply 64 is electrically connected to the lower electrode 18. The electric bias has a second frequency. The second frequency is lower than the first frequency. The second frequency is, for example, a frequency in the range of 400 kHz to 13.56 MHz. When the electric bias is used together with the high frequency power HF, it is applied to the lower electrode 18 to attract ions to the substrate W. When the electric bias is applied to the lower electrode 18, the potential of the substrate W placed on the substrate support 14 fluctuates within a period defined by the second frequency.

[0067] In one embodiment, the electric bias may be a high frequency power LF having a second frequency. When the high frequency power LF is used together with the high frequency power HF, it is used as a high frequency bias power for attracting ions to the substrate W. A bias power supply 64 configured to generate the high frequency power LF is connected to the lower electrode 18 via a matching box 68 and the electrode plate 16. The matching box 68 has a circuit for matching the impedance of the load side (lower electrode 18 side) of the bias power supply 64 to the output impedance of the bias power supply 64.

[0068] It is also possible to generate plasma using high frequency power LF without using high frequency power HF, that is, using only a single high frequency power. In this case, the frequency of the high frequency power LF may be a frequency higher than 13.56 MHz, for example, 40 MHz. In this case, the plasma processing apparatus 1 does not need to include the high frequency power supply 62 and the matching box 66. In this case, the bias power supply 64 constitutes an example of a plasma generating unit.

[0069] In another embodiment, the electrical bias may be a pulse wave of a DC voltage. The pulse wave of the DC voltage is periodically generated and applied to the lower electrode 18. The period of the pulse wave of the DC voltage is defined by the second frequency. The period of the pulse wave of the DC voltage includes two periods. The DC voltage in one of the two periods is a negative DC voltage. The level (i.e., absolute value) of the DC voltage in one of the two periods is higher than the level (i.e., absolute value) of the DC voltage in the other of the two periods. The DC voltage in the other period may be either negative or positive. The level of the DC voltage in the other period may be zero. In this embodiment, the bias power supply 64 is connected to the lower electrode 18 via a low-pass filter and the electrode plate 16.

[0070] In one embodiment, the bias power supply 64 may provide a continuous wave of an electric bias to the lower electrode 18. That is, the bias power supply 64 may continuously provide an electric bias to the lower electrode 18. The continuous wave of an electric bias may be provided to the lower electrode 18 during the period when step STP or steps ST2 and ST3 of the method MT are being performed.

[0071] In another embodiment, the bias power supply 64 may apply a pulse wave of an electric bias to the lower electrode 18. The pulse wave of the electric bias may be applied periodically to the lower electrode 18. The period of the pulse wave of the electric bias is defined by a third frequency. The third frequency is lower than the second frequency. The third frequency is, for example, 1 Hz or more and 200 kHz or less. In another example, the third frequency may be 5 Hz or more and 100 kHz or less.

[0072] The period of the pulse wave of the electric bias includes two periods, namely, an H period and an L period. The level of the electric bias in the H period (i.e., the level of the pulse of the electric bias) is higher than the level of the electric bias in the L period. That is, the pulse wave of the electric bias may be applied to the lower electrode 18 by increasing or decreasing the level of the electric bias. The level of the electric bias in the L period may be greater than zero. Alternatively, the level of the electric bias in the L period may be zero. That is, the pulse wave of the electric bias may be applied to the lower electrode 18 by alternately switching between supplying and stopping the supply of the electric bias to the lower electrode 18. Here, when the electric bias is a high frequency power LF, the level of the electric bias is the power level of the high frequency power LF. When the electric bias is a high frequency power LF, the level of the high frequency power LF in the pulse of the electric bias may be 2 kW or more. When the electric bias is a pulse wave of a negative polarity DC voltage, the level of the electric bias is the effective value of the absolute value of the negative polarity DC voltage. The duty ratio of the pulse wave of the electric bias, i.e., the ratio of the H period to the period of the pulse wave of the electric bias, is, for example, 1% or more and 80% or less. In another example, the duty ratio of the pulse wave of the electric bias may be 5% or more and 50% or less. Alternatively, the duty ratio of the pulse wave of the electric bias may be 50% or more and 99% or less. The pulse wave of the electric bias may be applied to the lower electrode 18 to perform steps ST2 and ST3 of the method MT.

[0073] In one embodiment, the high frequency power supply 62 may supply a continuous wave of high frequency power HF. That is, the high frequency power supply 62 may supply the high frequency power HF continuously. The continuous wave of high frequency power HF may be supplied during the period in which step STP or steps ST2 and ST3 of the method MT are performed.

[0074] In another embodiment, the high frequency power supply 62 may supply a pulse wave of high frequency power HF. The pulse wave of high frequency power HF may be supplied periodically. The period of the pulse wave of high frequency power HF is defined by a fourth frequency. The fourth frequency is lower than the second frequency. In one embodiment, the fourth frequency is the same as the third frequency. The period of the pulse wave of high frequency power HF includes two periods, namely, an H period and an L period. The power level of the high frequency power HF in the H period is higher than the power level of the high frequency power HF in the L period of the two periods. The power level of the high frequency power HF in the L period may be greater than zero or may be zero.

[0075] The period of the pulse wave of the high frequency power HF may be synchronized with the period of the pulse wave of the electric bias. The H period in the period of the pulse wave of the high frequency power HF may be synchronized with the H period in the period of the pulse wave of the electric bias. Alternatively, the H period in the period of the pulse wave of the high frequency power HF may not be synchronized with the H period in the period of the pulse wave of the electric bias. The time length of the H period in the period of the pulse wave of the high frequency power HF may be the same as or different from the time length of the H period in the period of the pulse wave of the electric bias.

[0076] When plasma processing is performed in the plasma processing apparatus 1, a gas is supplied from a gas supply unit to the internal space 10s. In addition, a high-frequency electric field is generated between the upper electrode 30 and the lower electrode 18 by supplying high-frequency power HF and / or an electric bias. The generated high-frequency electric field generates plasma from the gas in the internal space 10s.

[0077] The plasma processing apparatus 1 may further include a control unit 80. The control unit 80 may be a computer including a processor, a storage unit such as a memory, an input device, a display device, a signal input / output interface, and the like. The control unit 80 controls each part of the plasma processing apparatus 1. In the control unit 80, an operator can use the input device to input commands and the like to manage the plasma processing apparatus 1. In addition, the control unit 80 can visualize and display the operating status of the plasma processing apparatus 1 using the display device. Furthermore, the storage unit stores a control program and recipe data. The control program is executed by the processor to execute various processes in the plasma processing apparatus 1. The processor executes the control program and controls each part of the plasma processing apparatus 1 according to the recipe data.

[0078] Referring again to Fig. 1, the method MT will be described below taking as an example a case where the method MT is applied to a substrate W shown in Fig. 2 using a plasma processing apparatus 1. When the plasma processing apparatus 1 is used, the method MT can be executed in the plasma processing apparatus 1 by controlling each part of the plasma processing apparatus 1 by a control unit 80. In the following description, the control of each part of the plasma processing apparatus 1 by the control unit 80 for executing the method MT will also be described.

[0079] In the following description, in addition to FIG. 1, FIG. 4(a), FIG. 4(b), and FIG. 5 are referred to. FIG. 4(a) is a partially enlarged cross-sectional view of an example substrate to which the etching method shown in FIG. 1 is applied, and FIG. 4(b) is a partially enlarged cross-sectional view of an example substrate etched by plasma generated from a processing gas that does not contain phosphorus. FIG. 5 is a timing chart of an example of an etching method according to an exemplary embodiment. In FIG. 5, the horizontal axis indicates time. In FIG. 5, the vertical axis indicates the power level of the high frequency power HF, the level of the electric bias, and the supply state of the processing gas. The "L" level of the high frequency power HF indicates that the high frequency power HF is not supplied or that the power level of the high frequency power HF is lower than the power level indicated by "H". The "L" level of the electric bias indicates that the electric bias is not applied to the lower electrode 18 or that the level of the electric bias is lower than the level indicated by "H". In addition, the processing gas supply status of "ON" indicates that the processing gas is being supplied into the chamber 10, and the processing gas supply status of "OFF" indicates that the supply of the processing gas into the chamber 10 is stopped.

[0080] 1, the method MT starts with step ST1. In step ST1, a substrate W is prepared in a chamber 10. The substrate W is placed on an electrostatic chuck 20 in the chamber 10 and held by the electrostatic chuck 20. The substrate W may have a diameter of 300 mm.

[0081] In the method MT, step STP is then performed. In step STP, plasma processing is performed on the substrate W. In step STP, plasma is generated from a processing gas in the chamber 10. The method MT includes step ST2. Step ST2 is performed during the execution of step STP. The method MT may further include step ST3. Step ST3 is performed during the execution of step STP. Step ST2 and step ST3 may be performed simultaneously or independently of each other.

[0082] In step ST2, the silicon-containing film SF is etched by chemical species from the plasma generated from the process gas in the chamber 10 in step STP. In step ST3, a protective film PF is formed on the substrate W by chemical species from the plasma generated from the process gas in the chamber 10 in step STP. The protective film PF is formed on a sidewall surface that defines an opening formed in the silicon-containing film SF.

[0083] The process gas used in the process STP includes a halogen element and phosphorus. The halogen element included in the process gas may be fluorine. That is, the process gas may include a fluorine-containing gas. The process gas may include at least one halogen-containing molecule. The process gas may include at least one of a fluorocarbon and a hydrofluorocarbon as the at least one halogen-containing molecule. The fluorocarbon may be at least one of CF4, C2F6, C3F6, C3F8, C4F6, C4F8, C5F8, etc. The hydrofluorocarbon may be at least one of CH2F2, CHF3, CH3F, etc.

[0084] The process gas may include at least one phosphorus-containing molecule. That is, the process gas may include at least one phosphorus-containing gas. The phosphorus-containing gas may be a gas that includes both phosphorus and a halogen. The phosphorus-containing molecule may be tetraphosphorus decaoxide (PO 10The phosphorus-containing molecule may be an oxide such as tetraphosphorus octoxide (P4O8), tetraphosphorus hexoxide (P4O6). Tetraphosphorus decaoxide is sometimes called diphosphorus pentoxide (P2O5). The phosphorus-containing molecule may be a molecule containing both phosphorus and a halogen. The phosphorus-containing molecule may be a halide such as phosphorus trifluoride (PF3), phosphorus pentafluoride (PF5), phosphorus trichloride (PCl3), phosphorus pentachloride (PCl5), phosphorus tribromide (PBr3), phosphorus pentabromide (PBr5), phosphorus iodide (PI3). The phosphorus-containing molecule may be a phosphoryl halide such as phosphoryl fluoride (POF3), phosphoryl chloride (POCl3), phosphoryl bromide (POBr3). The phosphorus-containing molecule may be phosphine (PH3), calcium phosphide (e.g., Ca3P2), phosphoric acid (H3PO4), sodium phosphate (Na3PO4), hexafluorophosphoric acid (HPF6), etc. Phosphorus-containing molecules include fluorophosphines (H x PF y ) where the sum of x and y is 3 or 5. Examples of fluorophosphines include HPF2 and H2PF3. The process gas may contain one or more of the above phosphorus-containing molecules as the at least one phosphorus-containing molecule. For example, the process gas may contain at least one of PF3, PCl3, PF5, PCl5, POCl3, PH3, PBr3, and PBr5 as the at least one phosphorus-containing molecule. Note that, when each phosphorus-containing molecule contained in the process gas is liquid or solid, it may be vaporized by heating or the like and supplied into the chamber 10.

[0085] The process gas used in step ST2 may further contain carbon and hydrogen. The process gas may contain H2, hydrogen fluoride (HF), hydrocarbon (C x H y ), hydrofluorocarbons (C s H t F u ), and NH3. The hydrocarbon is, for example, CH4 or C3H6. The process gas may contain, as the carbon-containing molecule, the above-mentioned hydrocarbons, the above-mentioned hydrofluorocarbons, and fluorocarbons (C v F w), where x, y, s, t, u, v, and w are each a natural number. The process gas may further include oxygen. The process gas may include an oxygen-containing gas, such as O2. Alternatively, the process gas may be free of oxygen.

[0086] In one embodiment, the process gas may include a first gas and a second gas. The first gas is a gas that does not contain phosphorus. The first gas may include a halogen element. The first gas may include at least one gas of halogen-containing molecules as described above. The first gas may further include carbon and hydrogen. The first gas may further include a gas of molecules that include hydrogen and / or a gas of molecules that include carbon as described above. The first gas may further include oxygen. The first gas may include O2 gas. Alternatively, the first gas may not include oxygen. The second gas is a gas that contains phosphorus. The second gas may include at least one gas of phosphorus-containing molecules as described above.

[0087] In the process gas used in the process STP, a flow rate ratio, which is a ratio of a flow rate of the second gas to a flow rate of the first gas, may be set to be greater than 0 and equal to or less than 0.5. The flow rate ratio may be set to be equal to or greater than 0.075 and equal to or less than 0.3. The flow rate ratio may be set to be equal to or greater than 0.1 and equal to or less than 0.25.

[0088] In the process STP, the pressure of the gas in the chamber 10 is set to a specified pressure. In the process STP, the pressure of the gas in the chamber 10 may be set to a pressure of 10 mTorr (1.3 Pa) or more and 100 mTorr (13.3 Pa) or less. In addition, in the process STP, a high frequency power HF is supplied to generate plasma from the processing gas in the chamber 10. As shown by the solid line in FIG. 5, a continuous wave of the high frequency power HF may be supplied in the process STP. In place of the high frequency power HF, a high frequency power LF may be used in the process STP. In the process STP, both the high frequency power HF and an electric bias may be supplied. As shown by the solid line in FIG. 5, a continuous wave of the electric bias may be applied to the lower electrode 18 in the process STP. The power level of the high frequency power HF may be set to a level of 2 kW or more and 10 kW or less. The level of the high frequency power LF is 2 kW (2.83 W / cm in terms of the power level per unit area of ​​the substrate W). 2 The level of the high frequency power LF can be set to a level of 10 kW (14.2 W / cm in terms of the power per unit area of ​​the substrate W). 2 ) or higher.

[0089] To perform the process STP, the control unit 80 controls the gas supply unit to supply a process gas into the chamber 10. The control unit 80 also controls the exhaust unit 50 to set the gas pressure in the chamber 10 to a designated pressure. The control unit 80 also controls the plasma generation unit to generate plasma from the process gas. In the plasma processing apparatus 1, the control unit 80 controls the high frequency power supply 62 and the bias power supply 64 to supply high frequency power HF, high frequency power LF, or high frequency power HF and an electric bias.

[0090] In one embodiment of the method MT, the temperature of the substrate W at the start of step ST2 (or step STP) may be set to a temperature of 0° C. or less. When the temperature of the substrate W is set to such a temperature, the etching rate of the silicon-containing film SF in step ST2 increases. In order to set the temperature of the substrate W at the start of step ST2, the control unit 80 may control the chiller unit. Note that the temperature of the substrate W during the execution of step ST2 (or step STP) may be a temperature of 200° C. or less.

[0091] In one embodiment, the method MT may further include a step STT. The step STT is performed before the step ST2 (or the step STP). The temperature of the substrate W is set to a temperature of 0° C. or lower in the step STT. The temperature of the substrate W at the start of the step ST2 is set in the step STT. In order to set the temperature of the substrate W in the step STT, the control unit 80 may control a chiller unit.

[0092] In step ST2, the silicon-containing film SF is etched by halogen species from the plasma generated from the process gas. In one embodiment, the silicon-containing film SF is etched only in a portion of the entire region thereof that is exposed by the mask MK (see FIG. 4(a)).

[0093] When the processing gas contains molecules containing phosphorus and a halogen element such as PF3 as phosphorus-containing molecules, halogen species derived from such molecules contribute to etching of the silicon-containing film SF. Therefore, the phosphorus-containing molecules containing phosphorus and a halogen element such as PF3 increase the etching rate of the silicon-containing film SF in step ST2.

[0094] Furthermore, when the mask MK contains carbon, carbon-phosphorus bonds are formed on the surface of the mask in step ST2. The carbon-phosphorus bonds formed on the surface of the mask MK have higher bond energy than the carbon-carbon bonds in the mask MK. Therefore, according to the method MT, the mask MK is protected during plasma etching of the silicon-containing film SF. Furthermore, during plasma etching of the silicon-containing film SF, deterioration of the shape of the mask MK is suppressed. Therefore, according to the method MT, it is possible to protect the substrate during plasma etching of the film.

[0095] In one embodiment, the method MT may further include step ST3, as shown in FIG. 1. In step ST3, a protective film PF is formed on a sidewall surface that defines an opening formed in the silicon-containing film SF by etching in step ST2 (see FIG. 4(a)). The protective film PF is formed by chemical species from plasma generated from a processing gas in the chamber 10 in step STP. In one embodiment, step ST3 may proceed simultaneously with step ST2. As shown in FIG. 4(a), in one embodiment, the protective film PF may be formed such that its thickness decreases along the depth direction of the opening formed in the silicon-containing film SF.

[0096] The protective film PF includes silicon and phosphorus contained in a process gas used in the process STP. In one embodiment, the protective film PF may further include carbon and / or hydrogen contained in the process gas. In one embodiment, the protective film PF may further include oxygen contained in the process gas or contained in the silicon-containing film SF. In one embodiment, the protective film PF may include a bond of phosphorus and oxygen.

[0097] Figure 6 (a) and Figure 6 (b) are diagrams showing the results of XPS analysis of the protective film PF formed in an experimental example in which a silicon oxide film and a silicon nitride film were etched in the process STP. Each of Figure 6 (a) and Figure 6 (b) shows a P2p spectrum. The conditions of the process STP in the experimental example are shown below. <Conditions for process STP> Gas pressure in chamber 10: 100 mTorr (13.33 Pa) Processing gas: 50sccm PF3 gas and 150sccm Ar gas High frequency power HF (continuous wave): 40MHz, 4500W High frequency power LF (continuous wave): 400kHz, 7000W Substrate temperature (temperature of substrate holder before etching starts): -70℃ Time length of process STP execution period: 30 seconds

[0098] In an experimental example in which a silicon oxide film was etched in the process STP, the XPS analysis of the protective film PF showed a Si-O bond peak and a PO bond peak, as shown in Figure 6(a). Also, in an experimental example in which a silicon nitride film was etched in the process STP, the XPS analysis of the protective film PF showed a Si-P bond peak and a PN bond peak, as shown in Figure 6(b).

[0099] If the processing gas does not contain phosphorus, the silicon-containing film SF is also etched laterally as shown in FIG. 4B. As a result, the width of the opening formed in the silicon-containing film SF becomes wider in some places. For example, the width of the opening formed in the silicon-containing film SF becomes wider in some places near the mask MK.

[0100] On the other hand, in method MT, a protective film PF is formed on a sidewall surface that defines an opening formed in the silicon-containing film SF by etching. The silicon-containing film SF is etched while the sidewall surface is protected by the protective film PF. Therefore, according to method MT, it is possible to suppress lateral etching in the plasma etching of the silicon-containing film SF.

[0101] In one embodiment, during the period during which the process STP is continued, i.e., during the period during which plasma is generated from the processing gas in the process STP, one or more cycles each including the process ST2 and the process ST3 may be sequentially performed. In the process STP, two or more cycles may be sequentially performed.

[0102] In one embodiment, as shown by the dashed line in Fig. 5, the above-mentioned pulse wave of the electric bias may be applied from the bias power supply 64 to the lower electrode 18 in the process STP. That is, when plasma generated from the processing gas is present in the chamber 10, the pulse wave of the electric bias may be applied from the bias power supply 64 to the lower electrode 18. In this embodiment, the etching of the silicon-containing film SF in the process ST2 mainly occurs in the H period in the period of the pulse wave of the electric bias. Moreover, the formation of the protective film PF in the process ST3 mainly occurs in the L period in the period of the pulse wave of the electric bias.

[0103] In addition, when the electric bias is high frequency power LF, the power level of the high frequency power LF may be set to a level of 2 kW or more during the H period in the period of the pulse wave of the electric bias. The power level of the high frequency power LF may be set to a level of 10 kW or more during the H period in the period of the pulse wave of the electric bias.

[0104] In one embodiment, as shown by the dashed line in FIG. 5, the pulse wave of the high frequency power HF described above may be supplied in the step STP. In the H period in the cycle of the pulse wave of the high frequency power HF, the power level of the high frequency power HF may be set to a level of 1 kW or more and 10 kW or less. As shown in FIG. 5, the cycle of the pulse wave of the high frequency power HF may be synchronized with the cycle of the pulse wave of the electric bias. As shown in FIG. 5, the H period in the cycle of the pulse wave of the high frequency power HF may be synchronized with the H period in the cycle of the pulse wave of the electric bias. Alternatively, the H period in the cycle of the pulse wave of the high frequency power HF may not be synchronized with the H period in the cycle of the pulse wave of the electric bias. The time length of the H period in the cycle of the pulse wave of the high frequency power HF may be the same as or different from the time length of the H period in the cycle of the pulse wave of the electric bias.

[0105] FIG. 7 is a timing chart of another example of an etching method according to an exemplary embodiment. In FIG. 7, the horizontal axis indicates time. In FIG. 7, the vertical axis indicates the power level of the high frequency power HF, the level of the electric bias, the supply state of the first gas, and the supply state of the second gas. The "L" level of the high frequency power HF indicates that the high frequency power HF is not supplied or that the power level of the high frequency power HF is lower than the power level indicated by "H". The "L" level of the electric bias indicates that the electric bias is not applied to the lower electrode 18 or that the level of the electric bias is lower than the level indicated by "H". In addition, the "ON" supply state of the first gas indicates that the first gas is supplied into the chamber 10, and the "OFF" supply state of the first gas indicates that the supply of the first gas into the chamber 10 is stopped. In addition, the supply status of the second gas being "ON" indicates that the second gas is being supplied into the chamber 10, and the supply status of the second gas being "OFF" indicates that the supply of the second gas into the chamber 10 is stopped.

[0106] 7, in step STP, the first gas and the second gas may be alternately supplied into the chamber 10. The etching of the silicon-containing film SF in step ST2 occurs mainly during the period in which the first gas is supplied into the chamber 10. Moreover, the formation of the protective film PF in step ST3 occurs mainly during the period in which the second gas is supplied into the chamber 10.

[0107] As shown by the solid line in Fig. 7, a continuous wave of high frequency power HF may be supplied in the step STP. Alternatively, a pulse wave of high frequency power HF may be supplied in the step STP, similar to the pulse wave of high frequency power HF shown in Fig. 5. The pulse wave of high frequency power HF is shown by the dashed line in Fig. 7. The H period in the period of the pulse wave of high frequency power HF is synchronized with or partially overlaps with the period during which the first gas is supplied into the chamber 10. Also, the L period in the period of the pulse wave of high frequency power HF is synchronized with or partially overlaps with the period during which the second gas is supplied into the chamber 10.

[0108] Also, as shown by the solid line in Fig. 7, a continuous wave of an electric bias may be applied to the lower electrode 18 in the step STP. Alternatively, a pulse wave of an electric bias may be applied to the lower electrode 18 in the step STP, similar to the pulse wave of an electric bias shown in Fig. 5. The pulse wave of an electric bias is shown by the dashed line in Fig. 7. The H period in the period of the pulse wave of the electric bias is synchronized with or partially overlaps with the period in which the first gas is supplied into the chamber 10. Also, the L period in the period of the pulse wave of the electric bias is synchronized with or partially overlaps with the period in which the second gas is supplied into the chamber 10.

[0109] Hereinafter, reference will be made to Fig. 8, Fig. 9(a), and Fig. 9(b). Fig. 8 is a plan view of a substrate of another example. Fig. 9(a) is a cross-sectional view taken along line IXA-IXA in Fig. 8, and Fig. 9(b) is a cross-sectional view taken along line IXB-IXB in Fig. 8. The substrate to which the method MT is applied may have a mask MK like the substrate W shown in Fig. 8, Fig. 9(a), and Fig. 9(b). That is, the mask of the substrate to which the method MT is applied may include a portion where the mask occupies a high proportion and a portion where the mask occupies a low proportion with respect to an opening defined by the mask on the silicon-containing film SF.

[0110] The mask MK of the substrate W shown in Figures 8, 9(a) and 9(b) contains carbon. The mask MK is formed of, for example, an amorphous carbon film, a photoresist film or a spin-on carbon film (SOC film).

[0111] In the substrate W shown in Figures 8, 9(a) and 9(b), the mask MK defines a plurality of openings OP. The mask MK includes a portion MKA where the mask MK occupies a high proportion of the opening OP defined by the mask MK on the silicon-containing film SF and a portion MKB where the proportion is low. The portion MKA where the mask MK occupies a high proportion of the opening OP is a portion where the mask MK is densely formed, i.e., a dense region. The portion MKB where the mask MK occupies a low proportion of the opening OP is a portion where the mask MK is sparsely formed, i.e., a sparse region. Note that this "proportion" refers to the proportion of the area of ​​the mask MK per unit area in the plane on the silicon-containing film SF, or the proportion of the length of the mask MK per unit length in the plane on the silicon-containing film SF.

[0112] Each of the multiple openings OP may have a rectangular planar shape as shown in Fig. 8. Alternatively, each of the multiple openings OP may have other planar shapes such as a circle or an ellipse. Each of the multiple openings OP may be two-dimensionally arranged to provide a plurality of rows and a plurality of columns thereof as shown in Fig. 8. In the substrate W shown in Figs. 8, 9(a) and 9(b), the portion MKA includes a pattern of the mask MK in one of the row direction and column direction of the above-mentioned array, and the portion MKB includes a pattern of the mask MK in the other direction.

[0113] In general, the mask MK in the sparse region is etched more than the mask MK in the dense region by the plasma etching of the silicon-containing film SF. In the substrate W shown in FIG. 8, FIG. 9(a) and FIG. 9(b), when the mask MK in the sparse region is etched more than the mask MK in the dense region, the shape of the line LN is distorted due to the internal stress of the mask MK. When the shape of the line LN is distorted, the LER (Line Edge Roughness) and LWR (Line Width Roughness) of the line LN become large. However, in the method MT, the carbon of the mask MK and the phosphorus from the plasma generated in the step STP are bonded on the surface of the mask MK. The carbon-phosphorus bond formed on the surface of the mask MK has a higher bond energy than the carbon-carbon bond in the mask MK. Therefore, in the method MT, the carbon-phosphorus bond formed on the surface of the mask MK protects the mask MK during the etching of the silicon-containing film SF in the step ST2. Therefore, according to the method MT, it is possible to protect the substrate W during the plasma etching of the silicon-containing film SF. In addition, the carbon-phosphorus bond formed on the surface of the mask MK reduces the amount of etching of the mask MK in the sparse region. As a result, the difference between the amount of etching of the mask MK in the sparse region and the amount of etching of the mask MK in the dense region is reduced. As a result, deterioration of the shape of the mask MK having both sparse and dense regions is suppressed.

[0114] The first experiment performed to evaluate the method MT will be described below. In the first experiment, a plurality of sample substrates having the same structure as the substrate W shown in FIG. 2 were prepared. Each of the plurality of sample substrates had a silicon oxide film and a mask provided on the silicon oxide film. The mask was a mask formed of an amorphous carbon film. In the first experiment, the process STP of the method MT was applied to the plurality of sample substrates. The process gas used for each of the plurality of sample substrates contained PF3 gas with different flow rates. Other conditions in the process STP are shown below. The flow rates of the PF3 gas were 0 sccm, 15 sccm, 30 sccm, 50 sccm, and 100 sccm, respectively. That is, in the first experiment, the flow rate ratios, which are the ratios of the flow rate of the second gas to the flow rate of the first gas, were 0, 0.075, 0.15, 0.25, and 0.5, respectively. <Conditions for process STP> Gas pressure in chamber 10: 25 mTorr (3.3 Pa) Process gas: 50sccm CH4 gas, 100sccm CF4 gas, 50sccm O2 gas High frequency power HF (continuous wave): 40MHz, 4500W High frequency power LF (continuous wave): 400kHz, 7000W Temperature of sample substrate (temperature of substrate holder before etching starts): -30℃ Time length of process STP execution period: 600 seconds

[0115] In the first experiment, the etching rate of the silicon oxide film, the maximum width of the opening formed in the silicon oxide film, and the selectivity were obtained for each of the multiple sample substrates. The selectivity is a value obtained by dividing the etching rate of the silicon oxide film by the etching rate of the mask. In the first experiment, the relationship between the flow rate of the PF3 gas in the processing gas used in the process STP and the etching rate of the silicon oxide film was obtained. Also, the relationship between the flow rate of the PF3 gas in the processing gas used in the process STP and the maximum width of the opening formed in the silicon oxide film was obtained. Also, the relationship between the flow rate of the PF3 gas in the processing gas used in the process STP and the selectivity was obtained. The relationship between the flow rate of the PF3 gas in the processing gas and the etching rate of the silicon oxide film is shown in FIG. 10. Also, the relationship between the flow rate of the PF3 gas in the processing gas and the maximum width of the opening formed in the silicon oxide film is shown in FIG. 11. Also, the relationship between the flow rate of the PF3 gas in the processing gas and the selectivity is shown in FIG. 12.

[0116] As shown in Fig. 10 and Fig. 12, when the processing gas contains phosphorus, that is, when the flow rate ratio, which is the ratio of the flow rate of the second gas to the flow rate of the first gas, is greater than 0, it was confirmed that the etching rate and the selectivity of the silicon oxide film are high. Also, as shown in Fig. 12, when the flow rate of PF3 gas in the processing gas is 15 sccm or more and 60 sccm or less or 50 sccm or less, it was confirmed that a considerably high selectivity is obtained. That is, when the flow rate ratio is 0.075 or more and 0.3 or less or 0.25 or less, it was confirmed that a considerably high selectivity is obtained. Also, as shown in Fig. 10, when the flow rate of PF3 gas in the processing gas is 20 sccm or more, that is, when the flow rate ratio is 0.1 or more, it was confirmed that the etching rate is about 1.5 times higher than that when PF3 is not added.

[0117] 11, it was confirmed that when the processing gas contains phosphorus, it is possible to suppress the maximum width of the opening of the silicon oxide film from becoming smaller, that is, to suppress the width of the opening of the silicon oxide film from becoming wider in part. In particular, it was confirmed that when the flow rate of the PF3 gas in the processing gas is 50 sccm or more, it is possible to more significantly suppress the width of the opening of the silicon oxide film from becoming wider in part.

[0118] The second experiment performed to evaluate the method MT will be described below. In the second experiment, a plurality of sample substrates having the same structure as the substrate W shown in FIG. 8, FIG. 9(a), and FIG. 9(b) were prepared. Each of the plurality of sample substrates had a silicon oxide film and a mask provided on the silicon oxide film. The mask was a mask formed of an amorphous carbon film. In the second experiment, the process STP of the method MT was applied to the plurality of sample substrates. The process gas used for each of the plurality of sample substrates contained PF3 gas at flow rates different from each other. The other conditions of the process STP in the second experiment were the same as the other conditions of the process STP in the first experiment.

[0119] In the second experiment, the LER and LWR of the line LN of the mask MK of the substrate W after the process STP was applied were obtained. The relationship between the flow rate of PF3 gas in the process gas and each of the LER and LWR obtained in the second experiment is shown in Fig. 13. As shown in Fig. 13, it was confirmed that the LER and LWR became smaller as the flow rate of PF3 gas in the process gas increased. In other words, it was confirmed that the deterioration of the shape of the mask MK was reduced as the flow rate of PF3 gas in the process gas increased.

[0120] An etching method according to another exemplary embodiment will be described below. In the following description, reference will be made to FIG. 14, FIG. 15(a), FIG. 15(b), and FIG. 15(c). FIG. 14 is a flow chart of an etching method according to another exemplary embodiment (hereinafter, referred to as "method MT2"). FIG. 15(a), FIG. 15(b), and FIG. 15(c) are partially enlarged cross-sectional views of an example of a substrate in a state in which step ST22 of method MT2 is applied, a state in which step ST23 of method MT2 is applied, and a state after method MT2 is applied. In the following, method MT2 will be described by taking as an example a case in which it is performed using a plasma processing apparatus 1.

[0121] The method MT2 shown in Fig. 14 may be applied to a substrate W having a silicon-containing film SF and a mask MK, such as the substrate shown in Fig. 2. The method MT2 starts with step ST21. Step ST21 is the same step as step ST1 of the method MT1. In step ST21, the substrate W is prepared in the chamber 10. The substrate W is placed on the electrostatic chuck 20 in the chamber 10 and held by the electrostatic chuck 20. Steps ST22, ST23, and ST24 of the method MT2 may be performed with the substrate W accommodated in the chamber 10.

[0122] In the method MT2, step ST22 is performed after step ST21. In step ST22, the silicon-containing film SF is etched. In step ST22, as shown in (a) of FIG. 15, a halogen species is supplied to the substrate W to partially etch the silicon-containing film SF. The halogen species is, for example, an ion, and is shown by a circle surrounding a "+" in (a) of FIG.

[0123] The halogen species used in step ST22 is supplied from plasma generated from an etching gas. The etching gas includes a halogen-containing gas. The halogen-containing gas may include a fluorine-containing gas. The fluorine-containing gas may include at least one of hydrogen fluoride, nitrogen trifluoride (NF3), sulfur hexafluoride (SF6), the above-mentioned fluorocarbon, and the above-mentioned hydrofluorocarbon. The etching gas including a fluorocarbon may be used when the silicon-containing film SF includes a silicon oxide film. The etching gas including a hydrofluorocarbon may be used when the silicon-containing film SF includes a silicon nitride film. When the silicon-containing film SF includes polycrystalline silicon, the halogen-containing gas may include a halogen gas such as Cl2 gas. The etching gas may further include carbon and hydrogen, as in the first gas described above. The etching gas may further include the above-mentioned gas of molecules including hydrogen and / or gas of molecules including carbon. The etching gas may further include oxygen. The etching gas may include O2 gas.

[0124] To perform step ST22, the control unit 80 controls the gas supply unit to supply an etching gas into the chamber 10. The control unit 80 also controls the exhaust unit 50 to set the gas pressure in the chamber 10 to a designated pressure. The control unit 80 also controls the plasma generation unit to generate plasma from the etching gas in the chamber 10. In the plasma processing apparatus 1, the control unit 80 controls the high frequency power supply 62 and the bias power supply 64 to supply high frequency power HF, high frequency power LF, or high frequency power HF and an electric bias.

[0125] In the method MT2, step ST23 and step ST24 are performed in order after step ST22. In step ST23, as shown in FIG. 15(b), phosphorus species are supplied to the substrate W. The phosphorus species is, for example, phosphorus active species such as ions and / or radicals, and is shown in FIG. 15(b) as a circle surrounding "P". In step ST23, as shown in FIG. 15(b), a bond between an element contained in the silicon-containing film SF and phosphorus is formed on a sidewall surface that defines an opening in the silicon-containing film SF. When the silicon-containing film SF includes a silicon oxide film, a bond between phosphorus and oxygen is formed on the sidewall surface of the silicon-containing film SF. In step ST23, the sidewall surface of the silicon-containing film SF is inactivated (or passivated) by the phosphorus species. That is, the sidewall surface of the silicon-containing film SF is passivated. In addition, when the mask MK includes carbon, a bond between carbon and phosphorus may be formed on the surface of the mask MK in step ST23.

[0126] The phosphorus species used in step ST23 is provided from a plasma generated from a passivation gas. The passivation gas used in step ST23 includes a phosphorus-containing gas. The phosphorus-containing gas includes at least one phosphorus-containing molecule as described above. In an embodiment, the phosphorus-containing gas may be fluorine-free. Such a phosphorus-containing gas may include PCl3 or POCl3.

[0127] To perform step ST23, the control unit 80 controls the gas supply unit to supply a passivation gas into the chamber 10. The control unit 80 also controls the exhaust unit 50 to set the gas pressure in the chamber 10 to a designated pressure. The control unit 80 also controls the plasma generation unit to generate plasma from the passivation gas in the chamber 10. In the plasma processing apparatus 1, the control unit 80 controls the high frequency power supply 62 and the bias power supply 64 to supply high frequency power HF, high frequency power LF, or high frequency power HF and an electric bias.

[0128] In step ST24, the silicon-containing film SF is further etched. Step ST24 is the same as step ST22. That is, in step ST24, the silicon-containing film SF is etched by halogen species supplied from plasma generated from an etching gas.

[0129] In one embodiment, step ST23 and step ST24 may be repeated alternately. In this case, method MT2 may further include step ST25. In step ST25, it is determined whether or not a stop condition is satisfied. In step ST25, the stop condition is determined to be satisfied when, for example, the number of repetitions of a cycle including steps ST23 and ST24 reaches a predetermined number. If it is determined in step ST25 that the stop condition is not satisfied, the cycle is executed again. On the other hand, if it is determined in step ST25 that the stop condition is satisfied, method MT2 is terminated. When method MT2 is terminated, the base region UR may be exposed as shown in (c) of FIG. 15.

[0130] The phosphorus species used in step ST23 may be supplied from plasma generated at a location away from the chamber in which the substrate W is housed. The plasma processing apparatus used in step ST23 and the plasma processing apparatus used in step ST24 may be different from each other. In this case, the substrate W may be transported between the plasma processing apparatus used in step ST23 and the plasma processing apparatus used in step ST24 only through a reduced pressure space (i.e., without breaking the vacuum).

[0131] An etching method according to yet another exemplary embodiment will be described below. In the following description, reference will be made to FIG. 16, FIG. 17(a), and FIG. 17(b). FIG. 16 is a flow chart of an etching method according to yet another exemplary embodiment (hereinafter, referred to as "method MT3"). FIG. 17(a) and FIG. 17(b) are partially enlarged cross-sectional views of an example of a substrate in a state in which step STP3 of method MT3 is being applied and in a state after method MT3 has been applied, respectively. In the following, method MT3 will be described by taking as an example a case in which it is performed using a plasma processing apparatus 1.

[0132] The method MT3 shown in Fig. 16 may be applied to a substrate W having a silicon-containing film SF and a mask MK, such as the substrate shown in Fig. 2. The method MT3 starts with step ST31. Step ST31 is the same step as step ST1 of the method MT1. In step ST31, the substrate W is prepared in the chamber 10. The substrate W is placed on the electrostatic chuck 20 in the chamber 10 and held by the electrostatic chuck 20. Step STP3 of the method MT3 is performed with the substrate W accommodated in the chamber 10.

[0133] Step STP3 includes steps ST33 and ST34 which are performed simultaneously. Step ST33 is the same as step ST23 of method MT2. In step ST33, as shown in FIG. 17(a), phosphorus species are supplied to the substrate W to perform a passivation treatment on the sidewall surface of the silicon-containing film SF. In FIG. 17(a), the phosphorus species is indicated by a circle surrounding a "P". Step ST34 is the same as step ST24 of method MT2. In step ST34, as shown in FIG. 17(a), halogen species are supplied to the substrate W to etch the silicon-containing film SF. In FIG. 17(a), the halogen species is indicated by a circle surrounding a "+".

[0134] In step STP3, in order to simultaneously perform steps ST33 and ST34, a plasma of a process gas is generated in the chamber 10. The process gas includes the passivation gas described above in relation to step ST23 and the etching gas described above in relation to step ST22.

[0135] To perform step STP3, the control unit 80 controls the gas supply unit to supply a processing gas into the chamber 10. The control unit 80 also controls the exhaust unit 50 to set the gas pressure in the chamber 10 to a designated pressure. The control unit 80 also controls the plasma generation unit to generate plasma from the processing gas in the chamber 10. In the plasma processing apparatus 1, the control unit 80 controls the high frequency power supply 62 and the bias power supply 64 to supply high frequency power HF, high frequency power LF, or high frequency power HF and an electric bias.

[0136] In the methods MT2 and MT3, the sidewall surface of the silicon-containing film SF is inactivated (or passivated) by phosphorus. That is, the sidewall surface is passivated. Therefore, according to the methods MT2 and MT3, the sidewall surface is protected so as to suppress lateral etching of the silicon-containing film SF during plasma etching of the silicon-containing film SF. Therefore, according to the methods MT2 and MT3, it is possible to protect the substrate W during plasma etching of the silicon-containing film SF.

[0137] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various additions, omissions, substitutions, and modifications may be made. In addition, elements in different embodiments can be combined to form other embodiments.

[0138] For example, the plasma processing apparatus used in each of the methods MT, MT2, and MT3 may be a capacitively coupled plasma processing apparatus other than the plasma processing apparatus 1. Alternatively, the plasma processing apparatus used in each of the methods MT, MT2, and MT3 may be a type of plasma processing apparatus other than the capacitively coupled type. Such a plasma processing apparatus may be an inductively coupled plasma processing apparatus, an ECR (electron cyclotron resonance) plasma processing apparatus, or a plasma processing apparatus that generates plasma using surface waves such as microwaves.

[0139] In addition to the bias power supply 64 that supplies high frequency power LF to the lower electrode 18, the plasma processing apparatus may also include another bias power supply configured to apply pulses of negative polarity DC voltage intermittently or periodically to the lower electrode 18.

[0140] From the foregoing, it will be understood that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims. [Explanation of symbols]

[0141] 1...plasma processing apparatus, 10...chamber, W...substrate, SF...silicon-containing film.

Claims

1. A chamber, a substrate support configured to support a substrate in the chamber, the substrate including a silicon-containing film and a mask disposed on the silicon-containing film; and a gas supply unit configured to supply into the chamber a process gas for etching the silicon-containing film and forming recesses in the silicon-containing film, the process gas including a halogen element and phosphorus; and a plasma generating unit configured to generate a plasma from the process gas in the chamber to etch the silicon-containing film and form a protective film containing phosphorus on a sidewall of the recess; A plasma processing apparatus comprising:

2. The substrate support includes a lower electrode, a bias power supply that supplies an electrical bias to the lower electrode during etching of the silicon-containing film; The plasma processing apparatus according to claim 1 .

3. A plasma processing apparatus as described in claim 2, wherein the electrical bias is a continuous wave.

4. A plasma processing apparatus as described in claim 2, wherein the electrical bias is a pulse wave.

5. A plasma processing apparatus as described in claim 2, wherein the electrical bias is a pulse wave of DC voltage.

6. A plasma processing apparatus according to claim 1, wherein the processing gas includes a fluorine-containing gas and a phosphorus-containing gas.

7. The plasma processing apparatus of claim 6, wherein the phosphorus-containing gas includes at least one of PF 3 , PCl 3 , PF 5 , PCl 5 , POCl 3 , PH 3 , PBr 3 , and PBr 5 .

8. The plasma processing apparatus of claim 6, wherein the processing gas further contains a hydrocarbon, a hydrofluorocarbon, or a fluorocarbon.

9. A plasma processing apparatus according to claim 1, wherein the processing gas further contains carbon and hydrogen.

10. The plasma processing apparatus according to claim 9, wherein the processing gas contains at least one of H 2 , hydrogen fluoride, hydrocarbon, hydrofluorocarbon, and NH 3 as hydrogen-containing molecules.

11. The plasma processing apparatus of claim 9, wherein the processing gas contains at least one of hydrocarbons, hydrofluorocarbons, and fluorocarbons as carbon-containing molecules.

12. A plasma processing apparatus according to claim 1, wherein the processing gas further contains an oxygen-containing gas.

13. A plasma processing apparatus described in any one of claims 1 to 12, wherein the protective film is formed so that its thickness decreases along the depth direction of the recess.

14. A plasma processing apparatus according to claim 1, wherein the protective film contains a bond between phosphorus and oxygen and / or a bond between phosphorus and silicon.

15. A plasma processing apparatus described in any one of claims 1 to 14, wherein the silicon-containing film includes a silicon oxide film.

16. The plasma processing apparatus described in claim 15, wherein the silicon-containing film further includes at least one of a silicon nitride film, a polycrystalline silicon film, a carbon-containing silicon film, and a low dielectric constant film.

17. The mask comprising carbon, carbon-phosphorus bonds are formed on the surface of the mask during etching of the silicon-containing film; The plasma processing apparatus according to any one of claims 1 to 16.

18. A plasma processing apparatus described in any one of claims 1 to 16, wherein the mask includes a metal.

19. The plasma processing apparatus of claim 18, wherein the mask comprises at least one material selected from the group consisting of titanium nitride, tungsten, and tungsten carbide.

20. The method of claim 1, further comprising: (a) providing a substrate in a chamber of a plasma processing apparatus, the substrate including a silicon-containing film and a mask disposed on the silicon-containing film; (b) etching the silicon-containing film with chemical species from a plasma generated from a process gas in the chamber, the process gas including a halogen element and phosphorus; Including, In the step (b), the protective film containing phosphorus is formed on a side wall of a recess formed in the silicon-containing film by the etching. Etching method.

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