Plasma processing apparatus and etching method

Abstract

To provide a technique for improving a selection ratio of etching of a film containing silicon to etching of a mask in plasma etching.SOLUTION: The substrate processing method according to the exemplary embodiment includes providing a substrate in a chamber of a plasma processing apparatus. The substrate includes a silicon-containing film and a mask provided on the silicon-containing film. The substrate processing method further includes generating plasma from a first processing gas containing a hydrogen fluoride gas within the chamber. In the step of generating the plasma, the film is etched by chemical species from the plasma. The flow rate of the hydrogen fluoride gas with respect to the total flow rate of the first processing gas excluding the inert gas is 25% by volume or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a method for etching a film in a substrate. The film contains silicon, and the substrate further has a mask disposed on the film. The mask includes amorphous carbon or an organic polymer. The etching in this method uses plasma generated from a process gas including a hydrocarbon gas and a fluorohydrocarbon gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-39310 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique for improving the selectivity of etching a silicon-containing film relative to etching a mask in plasma etching. [Means for solving the problem]

[0005] In one exemplary embodiment, a substrate processing method is provided. The substrate processing method includes providing a substrate in a chamber of a plasma processing apparatus. The substrate has a silicon-containing film and a mask disposed on the silicon-containing film. The substrate processing method further includes generating a plasma from a first process gas including hydrogen fluoride gas in the chamber. In the plasma generating step, the silicon-containing film is etched by chemical species from the plasma. A flow rate of the hydrogen fluoride gas relative to a total flow rate of the first process gas excluding an inert gas is 25% by volume or more. [Effects of the Invention]

[0006] According to the present disclosure, a technique can be provided for improving the etching selectivity of a silicon-containing film relative to the etching of a mask in plasma etching. [Brief explanation of the drawings]

[0007] [Figure 1] 4 is a flowchart showing an example of a substrate processing method according to the first embodiment. [Figure 2] FIG. 1 is a diagram schematically illustrating an example of a plasma processing apparatus. [Figure 3] FIG. 2 is a partially enlarged cross-sectional view of an example substrate provided in step ST1. [Figure 4] 2 is a partially enlarged cross-sectional view of the example substrate after the substrate processing method shown in FIG. 1 is performed. [Figure 5] 2 is a graph showing the results of an experiment conducted to evaluate the substrate processing method shown in FIG. [Figure 6] 10 is a flowchart showing an example of a substrate processing method according to a second embodiment. [Figure 7] 10 is a flowchart showing an example of a substrate processing method according to a third embodiment. [Figure 8] 10 is a flowchart showing another example of the substrate processing method according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Various exemplary embodiments are described below.

[0009] In one exemplary embodiment, a substrate processing method is provided. The substrate processing method includes providing a substrate in a chamber of a plasma processing apparatus. The substrate has a silicon-containing film and a mask disposed on the silicon-containing film. The substrate processing method further includes generating a plasma from a first process gas including hydrogen fluoride gas in the chamber. In the plasma generating step, the silicon-containing film is etched by chemical species from the plasma. A flow rate of the hydrogen fluoride gas relative to a total flow rate of the first process gas excluding an inert gas is 25% by volume or more. According to this embodiment, by using plasma generated from the first process gas in which a flow rate of the hydrogen fluoride gas is 25% by volume or more relative to a total flow rate excluding an inert gas, the selectivity of etching the silicon-containing film relative to etching the mask is improved.

[0010] In one exemplary embodiment, the flow rate of the hydrogen fluoride gas relative to the total flow rate of the first process gas excluding the inert gas may be less than 80% by volume.

[0011] In one exemplary embodiment, the first process gas comprises at least one selected from the group consisting of a carbon-containing gas, an oxygen-containing gas, and a halogen-containing gas.

[0012] In one exemplary embodiment, the carbon-containing gas may include at least one selected from the group consisting of a fluorocarbon gas, a hydrofluorocarbon gas, and a hydrocarbon gas.

[0013] In one exemplary embodiment, the silicon-containing film may be at least one selected from the group consisting of a stacked film including a silicon oxide film and a silicon nitride film, a polysilicon film, a low dielectric constant film, and a stacked film including a silicon oxide film and a polysilicon film.

[0014] In one exemplary embodiment, the mask may be a carbon-containing mask or a metal-containing mask.

[0015] In one exemplary embodiment, the carbon-containing mask may be formed from at least one selected from the group consisting of spin-on carbon, tungsten carbide, amorphous carbon, and boron carbide.

[0016] In one exemplary embodiment, the substrate processing method further includes generating a plasma from the second process gas in the chamber, wherein the plasma is generated from the second process gas to clean the interior of the chamber with chemical species from the plasma.

[0017] In one exemplary embodiment, the second process gas may include at least one selected from the group consisting of a fluorine-containing gas, an oxygen-containing gas, a hydrogen-containing gas, and a nitrogen-containing gas.

[0018] In one exemplary embodiment, the substrate processing method further includes generating a plasma from a third process gas in the chamber before providing the substrate, wherein the plasma is generated from the third process gas to form a pre-coat film on the inner wall of the chamber.

[0019] In one exemplary embodiment, the third process gas may include a silicon-containing gas and an oxygen-containing gas.

[0020] In another exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a plasma generation unit, and a control unit. The chamber has a gas supply port and a gas exhaust port. The control unit is configured to perform a process including a disposing step and an etching step. In the disposing step, a substrate having a silicon-containing film and a mask provided on the silicon-containing film is disposed in the chamber. In the etching step, plasma is generated from a first process gas containing hydrogen fluoride gas to etch the silicon-containing film. In the etching step, the control unit is configured to control the flow rate of the hydrogen fluoride gas to be 25% by volume or more relative to the total flow rate of the first process gas excluding the inert gas.

[0021] Various exemplary embodiments will be described in detail below with reference to the drawings, in which the same or equivalent parts are designated by the same reference numerals.

[0022] [First embodiment] FIG. 1 is a flowchart showing an example of a substrate processing method according to the first embodiment. The method MT1 shown in FIG. 1 is performed to etch a silicon-containing film. The method MT1 can be used, for example, in manufacturing a NAND flash memory having a three-dimensional structure. The method MT1 is performed using a plasma processing apparatus. FIG. 2 is a diagram schematically showing an example of the plasma processing apparatus. The method MT1 shown in FIG. 1 can be performed using the plasma processing apparatus 1 shown in FIG. 2.

[0023] The plasma processing apparatus 1 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 made of, for example, aluminum. A corrosion-resistant film is provided on the inner wall surface of the chamber body 12. The film may be a ceramic such as aluminum oxide or yttrium oxide.

[0024] A passage 12p is formed in the 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 provided along the sidewall of the chamber body 12.

[0025] 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 within the internal space 10s. The support 13 has a support pedestal 14 on its upper portion. The support pedestal 14 is configured to support a substrate W within the internal space 10s.

[0026] The support table 14 has a lower electrode 18 and an electrostatic chuck 20. The support table 14 may further have an electrode plate 16. The electrode plate 16 is made of a conductor such as aluminum and has a generally disc 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 generally disc shape. The lower electrode 18 is electrically connected to the electrode plate 16.

[0027] The electrostatic chuck 20 is provided on the lower electrode 18. A substrate W is placed on the upper surface of the electrostatic chuck 20. The electrostatic chuck 20 has a main body and an electrode. The main 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 inside the main 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 held by the electrostatic chuck 20 due to the electrostatic attractive force.

[0028] An edge ring 25 is disposed on the peripheral edge of the lower electrode 18 so as to surround the edge of the substrate W. The edge ring 25 improves the in-plane uniformity of the plasma processing on the substrate W. The edge ring 25 may be made of silicon, silicon carbide, quartz, or the like.

[0029] A flow path 18f is provided inside the lower electrode 18. A heat exchange medium (e.g., a refrigerant) is supplied to the flow path 18f from a chiller unit (not shown) 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.

[0030] 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 between the upper surface of the electrostatic chuck 20 and the back surface of the substrate W.

[0031] The plasma processing apparatus 1 further includes an upper electrode 30. The upper electrode 30 is provided above the support table 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.

[0032] 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 from a low-resistance conductor or semiconductor that generates little Joule heat. The top plate 34 has a plurality of gas discharge holes 34a that penetrate the top plate 34 in its thickness direction.

[0033] 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 supply port 36c is formed in the support 36. The gas supply port 36c is connected to the gas diffusion chamber 36a. A gas supply pipe 38 is connected to the gas supply port 36c.

[0034] The gas supply pipe 38 is connected to a valve group 42, a flow rate controller group 44, and a gas source group 40. The gas source group 40, the valve group 42, and the flow rate controller group 44 constitute a gas supply unit. The gas source group 40 includes a plurality of gas sources. The valve group 42 includes a plurality of on-off valves. The flow rate controller group 44 includes a plurality of flow rate controllers. Each of the plurality of flow rate controllers in the flow rate controller group 44 is a mass flow controller or a pressure-controlled flow rate controller. Each of the plurality of gas sources in the gas source group 40 is connected to the gas supply pipe 38 via a corresponding on-off valve in the valve group 42 and a corresponding flow rate controller in the flow rate controller group 44.

[0035] 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 can be made of a ceramic such as yttrium oxide.

[0036] 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 base material made of aluminum. A plurality of through holes are formed in the baffle plate 48. A gas 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 gas exhaust port 12e via an exhaust pipe 52. The exhaust device 50 includes a pressure adjustment valve and a vacuum pump such as a turbomolecular pump.

[0037] The plasma processing apparatus 1 includes a first high-frequency power supply 62 and a second high-frequency power supply 64. The first high-frequency power supply 62 is a power supply that generates a first high-frequency power. The first high-frequency power has a frequency suitable for generating plasma. The frequency of the first high-frequency power is, for example, within a range of 27 MHz to 100 MHz. The first high-frequency power supply 62 is connected to the lower electrode 18 via a matching box 66 and the electrode plate 16. The matching box 66 has a circuit for matching the output impedance of the first high-frequency power supply 62 with the impedance on the load side (lower electrode 18 side). The first high-frequency power supply 62 may be connected to the upper electrode 30 via the matching box 66. The first high-frequency power supply 62 constitutes an example of a plasma generation unit.

[0038] The second high frequency power supply 64 is a power supply that generates second high frequency power. The second high frequency power has a frequency lower than that of the first high frequency power. When the second high frequency power is used together with the first high frequency power, the second high frequency power is used as bias high frequency power for attracting ions into the substrate W. The frequency of the second high frequency power is, for example, within the range of 400 kHz to 13.56 MHz. The second high frequency power supply 64 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 output impedance of the second high frequency power supply 64 with the impedance on the load side (lower electrode 18 side).

[0039] It is also possible to generate plasma using the second high-frequency power without using the first high-frequency power, i.e., using only a single high-frequency power. In this case, the frequency of the second high-frequency power may be greater than 13.56 MHz, for example, 40 MHz. The plasma processing apparatus 1 does not necessarily have to include the first high-frequency power supply 62 and the matching box 66. The second high-frequency power supply 64 constitutes an example of a plasma generation unit.

[0040] In the plasma processing apparatus 1, a gas is supplied from a gas supply unit to the internal space 10s to generate plasma. Furthermore, a high-frequency electric field is generated between the upper electrode 30 and the lower electrode 18 by supplying a first high-frequency power and / or a second high-frequency power. The generated high-frequency electric field generates plasma.

[0041] 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, etc. The control unit 80 controls each unit of the plasma processing apparatus 1. The control unit 80 allows an operator to use the input device to input commands and perform other operations to manage the plasma processing apparatus 1. The control unit 80 also allows the display device to visualize and display the operating status of the plasma processing apparatus 1. Furthermore, the storage unit stores a control program and recipe data. The control program is executed by the processor to perform various processes in the plasma processing apparatus 1. The processor executes the control program and controls each unit of the plasma processing apparatus 1 according to the recipe data.

[0042] Referring again to FIG. 1 , the method MT1 will be described below using a plasma processing apparatus 1 as an example for its implementation. As shown in FIG. 1 , the method MT1 includes a step ST1. In the step ST1, a substrate W is provided in a chamber 10 of the plasma processing apparatus. The substrate W is placed on an electrostatic chuck 20 and held by the electrostatic chuck 20.

[0043] FIG. 3 is a partially enlarged cross-sectional view of an example substrate provided in step ST1 of method MT1. The substrate W shown in FIG. 3 includes an underlayer UL, a film SF, and a mask MSK. The underlayer UL may be a polycrystalline silicon layer. The film SF is disposed on the underlayer UL. The film SF contains silicon. The film SF may be a stacked film including one or more silicon oxide films and one or more silicon nitride films. In the example shown in FIG. 3, the film SF is a multilayer film including multiple silicon oxide films IL1 and multiple silicon nitride films IL2. The multiple silicon oxide films IL1 and multiple silicon nitride films IL2 are alternately stacked. Note that the film SF may also be another silicon-containing single-layer film or another silicon-containing multilayer film. When the film SF is a single-layer film, it may be a low-k film formed of, for example, SiOC, SiOF, or SiCOH, or a polysilicon film. Alternatively, when the film SF is a multilayer film, it may be a stacked film including, for example, one or more silicon oxide films and one or more polysilicon films.

[0044] The mask MSK is provided on the film SF. The mask MSK has a pattern for forming spaces such as holes in the film SF. The mask MSK may be, for example, a hard mask. The mask MSK may be, for example, a carbon-containing mask and / or a metal-containing mask. The carbon-containing mask may be formed of at least one material selected from the group consisting of spin-on carbon, tungsten carbide, amorphous carbon, and boron carbide. The metal-containing mask may be formed of at least one material selected from the group consisting of titanium nitride, titanium oxide, and tungsten. Alternatively, the mask MSK may be a boron-containing mask formed of, for example, silicon boride, boron nitride, or boron carbide.

[0045] 1, the method MT1 further includes step ST2, which is performed after step ST1. In step ST2, a plasma is generated from the first process gas in the chamber 10. In step ST2, the film SF is etched by chemical species from the plasma.

[0046] The first process gas used in step ST2 contains hydrogen fluoride gas. The flow rate of the hydrogen fluoride gas in step ST2 may be 25 vol% or more, 30 vol% or more, or 34 vol% or more relative to the total flow rate of the first process gas excluding the inert gas. Because hydrogen fluoride gas is highly corrosive, the flow rate of the hydrogen fluoride gas may be less than 80 vol%, 78 vol% or less, or 75 vol% or less relative to the total flow rate of the first process gas excluding the inert gas, in order to suppress corrosion of the inner wall of the chamber 10. In one example, the flow rate of the hydrogen fluoride gas is adjusted to 25 vol% or more and less than 80 vol% relative to the total flow rate of the first process gas excluding the inert gas. By controlling the flow rate of the hydrogen fluoride gas in the first process gas excluding the inert gas within this range, the etching rate of the film SF relative to the etching rate of the mask MK can be improved. As a result, the selectivity of etching the silicon-containing film relative to etching the mask can be improved. On the other hand, if the flow rate of hydrogen fluoride gas in the first process gas excluding the inert gas is less than 25% by volume, the selectivity may not be sufficiently improved. The total flow rate of the first process gas excluding the inert gas may be adjusted appropriately depending on the chamber volume, and may be 100 sccm or more, for example.

[0047] The first processing gas may contain, in addition to hydrogen fluoride gas, at least one gas selected from the group consisting of a carbon-containing gas, an oxygen-containing gas, and a halogen-containing gas.

[0048] When the first process gas contains a carbon-containing gas, carbon-containing deposits are formed on the mask surface, further improving the etching selectivity of the silicon-containing film relative to the etching of the mask. The carbon-containing gas may include at least one selected from the group consisting of a fluorocarbon gas, a hydrofluorocarbon gas, and a hydrocarbon gas. Examples of the fluorocarbon gas include CF4, C2F2, C2F4, C3F8, C4F6, C4F8, and C5F8. Examples of the hydrofluorocarbon gas include CHF3, CH2F2, CH3F, C2HF5, C2H2F4, C2H3F3, C2H4F2, C3HF7, C3H2F6, C3H2F4, C3H3F5, C4H5F5, and C5H2F. 10 , c-C5H3F7 or C3H2F4 can be used. Examples of hydrocarbon gases include CH4, C2H6, C3H6, C3H8 or C4H 10 The carbon-containing gas may contain CO and / or CO2 in addition to the above. In one example, a hydrofluorocarbon gas having two or more carbon atoms may be used as the carbon-containing gas. When a hydrofluorocarbon gas having two or more carbon atoms is used, shape abnormalities such as bowing can be effectively suppressed.

[0049] When the first process gas contains an oxygen-containing gas, blocking of the mask during etching can be suppressed. The oxygen-containing gas can be, for example, at least one selected from the group consisting of O2, CO, CO2, H2O, and H2O2.

[0050] When the first process gas contains a halogen-containing gas, the etching profile can be controlled. The halogen-containing gas can be, for example, at least one selected from the group consisting of a fluorine-containing gas, a chlorine-containing gas, a boron-containing gas, and an iodine-containing gas. The fluorine-containing gas can be, for example, SF6, NF3, XeF2, SiF4, IF7, ClF5, BrF5, AsF5, NF5, PF3, PF5, POF3, BF3, HPF6, or WF6. The chlorine-containing gas can be, for example, SiCl2, SiCl4, CCl4, BCl3, PCl3, PCl5, or POCl3. The bromine-containing gas can be, for example, CBr2F2, C2F5Br, PBr3, PBr5, or POBr3. The iodine-containing gas can be, for example, HI, CF3I, C2F5I, C3F7I, IF5, IF7, I2, or PI3.

[0051] In addition to the above, the first processing gas may be a gas having a sidewall protection effect, such as a sulfur-containing gas such as COS, PO 10 , P4O8, P4O6, PH3, Ca3P2, H3PO4, Na3PO4, or other phosphorus-containing gases, or boron-containing gases such as B2H6.

[0052] In addition to these gas species, the first process gas may contain an inert gas. Examples of the inert gas include nitrogen-containing gas and rare gases such as Ar, Kr, and Xe. However, the flow rate of the first process gas is controlled so that the ratio of the hydrogen fluoride gas to the total flow rate of the first process gas excluding these inert gases is as described above.

[0053] To perform step ST2, the control unit 80 controls the gas supply unit to supply the above-described process gas into the chamber 10. To perform step ST2, the control unit 80 controls the gas supply unit so that the flow rate of hydrogen fluoride gas in the process gas supplied into the chamber 10 is 25 volume % or more of the total flow rate of the process gas. To perform step ST2, the control unit 80 controls the exhaust device 50 to adjust the pressure in the chamber 10 to a specified pressure. To perform step ST2, the control unit 80 controls the first high frequency power supply 62 and / or the second high frequency power supply 64 to supply first high frequency power and / or second high frequency power to generate plasma from the process gas in the chamber 10.

[0054] In step ST2, the second high-frequency power supply 64 is set to 5 W / cm to attract ions from the plasma to the substrate W. 2 The second high frequency power (i.e., high frequency power for bias) may be supplied to the lower electrode 18. 5 W / cm 2 The second high frequency power described above allows ions from the plasma to sufficiently reach the bottom of the space (for example, the space SP shown in FIG. 4) in the film SF formed by etching. Note that instead of the high frequency bias power, a negative DC voltage may be applied to the lower electrode 18. Furthermore, the high frequency bias power or the negative DC voltage may be applied in pulses to the lower electrode 18. In this case, the pulse frequency may be 5 Hz to 100 kHz.

[0055] The temperature of the electrostatic chuck in step ST2 is not particularly limited. However, by adjusting the temperature of the electrostatic chuck to a low temperature, for example, 0° C. or lower or −50° C. or lower, before starting step ST2, adsorption of the etchant on the substrate surface is promoted, thereby improving the etching rate.

[0056] When the execution of step ST2 is completed, the method MT1 is completed. Fig. 4 is a partially enlarged cross-sectional view of an example substrate after the execution of the substrate processing method shown in Fig. 1. By executing the method MT1, as shown in Fig. 4, a space SP is formed in the film SF, for example, reaching the base layer UL.

[0057] The following describes the results of an experiment conducted to evaluate method MT1. Eight sample substrates identical to the substrate W shown in FIG. 3 were prepared for the experiment. In the experiment, plasma etching of the film SF on the eight sample substrates was performed using plasma processing apparatus 1. A first process gas containing a carbon-containing gas was used for the plasma etching. The first process gas used for plasma etching of the first of the eight sample substrates did not contain hydrogen fluoride gas. In the plasma etching of sample substrates 2 to 8, the flow rate ratios of hydrogen fluoride gas to the total flow rate of the first process gas were 34.2 vol%, 51.0 vol%, 80.0 vol%, 95.2 vol%, 98.8 vol%, 99.5 vol%, and 100 vol%, respectively. In the experiment, the temperature of the electrostatic chuck on which the sample substrates were placed was adjusted to −50°C or below before the start of plasma etching.

[0058] In the experiment, the etching selectivity of the film SF relative to the etching of the mask MSK was calculated from the results of plasma etching of the film SF of the eight sample substrates. Specifically, the selectivity was calculated by dividing the etching rate of the film SF by the etching rate of the mask MK from the results of plasma etching of the film SF of the eight sample substrates.

[0059] The results of the experiment are shown in FIG. 5. FIG. 5 is a graph showing the results of an experiment conducted to evaluate the substrate processing method shown in FIG. 1. In the graph of FIG. 5, the horizontal axis represents the flow rate ratio. The flow rate ratio is the ratio (volume %) of the flow rate of hydrogen fluoride gas to the total flow rate of the first processing gas excluding the inert gas. In the graph of FIG. 5, the vertical axis represents the selectivity ratio. In FIG. 5, reference symbols P1 to P8 represent the selectivity ratios obtained from the results of plasma etching of the film SF of the first to eighth sample substrates.

[0060] As shown in Figure 5, the experimental results confirmed that the selectivity increases with an increase in the ratio of the flow rate of hydrogen fluoride gas to the total flow rate of the first process gas excluding the inert gas (hereinafter referred to as "flow rate ratio"). Figure 5 also shows that a selectivity of 4 or more can be obtained when the flow rate of hydrogen fluoride gas accounts for 25 volume % or more of the total flow rate of the first process gas excluding the inert gas.

[0061] [Second embodiment] In the substrate processing method according to the first embodiment, as the number of processing operations increases, the amount of reaction products adhering to the inner walls of the chamber 10, the support table 14, and the like increases. When the amount of reaction products increases, the processing environment changes, which may result in a decrease in processing uniformity between substrates W. Furthermore, an increase in the amount of reaction products adhering can cause particle generation. Therefore, the inside of the chamber is cleaned with plasma obtained by converting a cleaning gas into plasma.

[0062] 6 is a flowchart showing an example of a substrate processing method according to the second embodiment. Similar to the method MT1, the method MT2 shown in FIG. 6 is performed to etch a silicon-containing film. Steps ST21 and ST22 are similar to steps ST11 and ST12 of the method MT1 described above, and therefore will not be described here.

[0063] As shown in FIG. 6, method MT2 further includes step ST23. Step ST23 is performed after step ST22. In step ST23, plasma is generated from the second processing gas in chamber 10. In step ST23, chemical species from this plasma clean the interior of chamber 10. The processing time for step ST23 is usually determined by monitoring the plasma emission state. According to the second embodiment, the cleaning time can be reduced to 50% or less compared to the conventional technique, thereby improving the throughput of substrate processing.

[0064] The second process gas used in step ST23 may contain at least one gas selected from the group consisting of a fluorine-containing gas, an oxygen-containing gas, a hydrogen-containing gas, and a nitrogen-containing gas. The fluorine-containing gas may be, for example, CF4, SF6, or NF3. The oxygen-containing gas may be, for example, O2, CO, CO2, H2O, or H2O2. The hydrogen-containing gas may be, for example, H2 or HCl. The nitrogen-containing gas may be, for example, N2. In addition to the above, the second process gas may contain a rare gas such as Ar.

[0065] Step ST23 may be performed after each substrate W is processed, or after a predetermined number or a predetermined number of lots of substrates W have been processed, or after substrates have been processed for a predetermined period of time.

[0066] [Third embodiment] In both the first and second embodiments, the first process gas contains hydrogen fluoride gas. Because hydrogen fluoride gas is highly corrosive, it is preferable to form a precoat film on the inner wall of the chamber 10 before the etching process. In particular, when using hydrogen fluoride gas at a high concentration, forming a precoat film on the inner wall of the chamber 10 can suppress corrosion of the inner wall of the chamber 10, thereby reducing the frequency of maintenance. Here, the inner wall of the chamber 10 includes the side wall and ceiling of the chamber 10 (top plate 34 of the upper electrode 30), as well as the support table 14, etc.

[0067] The precoat film may be formed from a silicon-containing film such as a silicon oxide film or from the same material as the mask MSK. When the mask MSK is a carbon-containing mask, the precoat film may be formed from a carbon-containing substance. The carbon-containing substance may include, for example, at least one selected from the group consisting of spin-on carbon, tungsten carbide, amorphous carbon, and boron carbide. When the mask MSK is a metal-containing mask, the precoat film may be formed from a metal-containing substance. The metal-containing substance may include, for example, at least one selected from the group consisting of titanium nitride, titanium oxide, and tungsten. When the mask MSK is a boron-containing mask, the precoat film may be formed from a boron-containing substance. The boron-containing substance may include, for example, at least one selected from the group consisting of silicon boride, boron nitride, and boron carbide. The protective film PF is formed from the same material as the mask MK. When the mask MK is formed from an organic film, the protective film PF is formed from a carbon-containing substance. When the mask MK is formed from a silicon-containing film, the protective film PF is formed from a silicon-containing material (e.g., polycrystalline silicon or silicon carbide). When the mask MK is formed from a metal-containing film, the protective film PF is formed from a metal-containing material. The metal-containing material includes any of titanium, titanium nitride, titanium carbide, titanium oxide, tungsten, tungsten carbide, ruthenium, ruthenium oxide, molybdenum, molybdenum carbide, etc.

[0068] 7 is a flowchart showing an example of a substrate processing method according to the third embodiment. Similar to the method MT1, the method MT3 shown in FIG. 7 is performed to etch a silicon-containing film. Steps ST31 and ST32 are similar to steps ST11 and ST12 of the method MT1 described above, and therefore will not be described here.

[0069] 7, the method MT2 further includes step ST303. Step ST30 is performed before step ST31. In step ST30, plasma is generated from the third process gas in the chamber 10. In step ST30, chemical species from the plasma form a pre-coat film on the inner wall of the chamber 10.

[0070] The pre-coat film can be formed by chemical vapor deposition (CVD) or atomic layer deposition (ALD) using a third process gas. For example, when a silicon oxide film is formed as the pre-coat film, a silicon-containing gas such as SiCl4 or an aminosilane-based gas and an oxygen-containing gas such as O2 can be used as the third process gas.

[0071] Step ST33 may be performed after each substrate W is processed, or after a predetermined number or a predetermined number of lots of substrates W have been processed, or after substrates have been processed for a predetermined period of time.

[0072] The step of forming the pre-coat film may be performed in combination with a cleaning step as shown in another example of the substrate processing method according to the third embodiment in Fig. 8. This makes it possible to simultaneously suppress the generation of particles and corrosion of the inner wall of the chamber 10.

[0073] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various omissions, substitutions, and modifications may be made. Furthermore, elements in different exemplary embodiments may be combined to form other exemplary embodiments.

[0074] For example, the plasma processing apparatus used in the methods MT1 to MT4 may be a plasma processing apparatus other than the plasma processing apparatus 1. The plasma processing apparatus used in the methods MT1 to MT4 may be another capacitively coupled plasma processing apparatus, an inductively coupled plasma processing apparatus, or a plasma processing apparatus that generates plasma using surface waves such as microwaves.

[0075] Furthermore, because hydrogen fluoride gas is a highly corrosive gas as described above, the flow rate of the hydrogen fluoride gas and the type of gas added to the first process gas may be changed depending on the process stage. For example, the flow rate of the hydrogen fluoride gas at the end of etching, when it is not necessary to maintain the mask thickness, may be lower than the flow rate of the hydrogen fluoride gas at the beginning to middle stages of etching, when it is necessary to maintain the mask thickness. For example, the flow rate of the gas having a sidewall protection effect may be higher in etching of low aspect ratio regions, where shape abnormalities such as bowing are likely to occur, than in etching of high aspect ratio regions. Furthermore, the shape after etching may be monitored using an optical observation device or the like, and the flow rate of the hydrogen fluoride gas and the type or flow rate of the gas added to the first process gas may be changed depending on the shape.

[0076] From the foregoing, it will be understood that various exemplary 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 exemplary embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims. [Explanation of symbols]

[0077] 1...plasma processing apparatus, 10...chamber, W...substrate, SF...film, MSK...mask.

Claims

1. providing a substrate having a silicon-containing film and a mask on the silicon-containing film in a chamber; adjusting the temperature of an electrostatic chuck on which the substrate is placed to 0°C or less; generating a plasma from a first process gas including hydrogen fluoride gas and a phosphorus-containing gas in the chamber to etch the silicon-containing film; Including, a flow rate of the hydrogen fluoride gas relative to a total flow rate of the first process gas excluding an inert gas is 25% by volume or more; Substrate processing method.

2. 2. The substrate processing method according to claim 1, wherein a flow rate of the hydrogen fluoride gas relative to a total flow rate of the first processing gas excluding the inert gas is less than 80% by volume.

3. 3. The substrate processing method according to claim 1, wherein the first processing gas contains at least one gas selected from the group consisting of a carbon-containing gas, an oxygen-containing gas, and a halogen-containing gas.

4. 3. The substrate processing method according to claim 1, wherein the first processing gas contains a halogen-containing gas.

5. The halogen-containing gas is SF ６ , N.F. ３ , XeF ２ , SiF ４ , IF ７ , ClF ５ , BrF ５ , AsF ５ , N.F. ５ , P.F. ３ , P.F. ５ , POF ３ , B.F. ３ , HPF ６ , W.F. ６ , SiCl ２ , SiCl ４ , CCl ４ , BCl ３ , PCl ３ , PCl ５ , POCl ３ , CBr ２ F ２ , C ２ F ５ Br, PBr ３ , PBr ５ , POBr ３ , H.I., C.F. ３ I, C ２ F ５ I, C ３ F ７ I, IF ５ , I ２ and P.I. ３ 5. The substrate processing method according to claim 3, wherein the solvent is at least one selected from the group consisting of:

6. The halogen-containing gas is XeF ２ , P.F. ３ , P.F. ５ , W.F. ６ , BCl ３ , PCl ３ , PCl ５ , POCl ３ , CBr ２ F ２ , C ２ F ５ Br, CF ３ I, C ２ F ５ I and C ３ F ７ 5. The substrate processing method according to claim 3, wherein the compound is at least one selected from the group consisting of I.

7. 4. The substrate processing method according to claim 3, wherein the carbon-containing gas includes at least one gas selected from the group consisting of a fluorocarbon gas, a hydrofluorocarbon gas, and a hydrocarbon gas.

8. The first process gas is O ２ , CO, CO ２ , H ２ O or H ２ O ２ The substrate processing method according to claim 1 , further comprising at least one selected from the group consisting of:

9. 9. The substrate processing method according to claim 1, wherein the first processing gas contains a nitrogen-containing gas or a rare gas.

10. 10. The substrate processing method according to claim 1, wherein the silicon-containing film is at least one selected from the group consisting of a stacked film containing a silicon oxide film and a silicon nitride film, a polysilicon film, a low dielectric constant film, and a stacked film containing a silicon oxide film and a polysilicon film.

11. 11. The substrate processing method according to claim 1, wherein the mask is a carbon-containing mask or a metal-containing mask.

12. 12. The substrate processing method according to claim 1, wherein the mask is a metal-containing mask containing at least one selected from the group consisting of titanium nitride, titanium oxide, and tungsten.

13. 12. The substrate processing method of claim 11, wherein the carbon-containing mask is formed from at least one selected from the group consisting of spin-on carbon, tungsten carbide, amorphous carbon, and boron carbide.

14. 14. The substrate processing method according to claim 1, further comprising the step of generating plasma from a second processing gas in the chamber to clean the inside of the chamber.

15. 15. The substrate processing method of claim 14, wherein the second processing gas includes at least one gas selected from the group consisting of a fluorine-containing gas, an oxygen-containing gas, a hydrogen-containing gas, and a nitrogen-containing gas.

16. 16. The substrate processing method according to claim 1, further comprising, before the step of providing the substrate, generating plasma from a third processing gas in the chamber to form a pre-coat film on an inner wall of the chamber.

17. 17. The substrate processing method of claim 16, wherein the third process gas includes a silicon-containing gas and an oxygen-containing gas.

18. a chamber having a gas inlet and a gas outlet; a plasma generating unit; A control unit; A plasma processing apparatus comprising: The control unit placing a substrate having a silicon-containing film and a mask disposed on the silicon-containing film in the chamber; adjusting the temperature of an electrostatic chuck on which the substrate is placed to 0°C or less; generating a plasma from a first process gas including hydrogen fluoride gas and a phosphorus-containing gas in the chamber to etch the silicon-containing film; Perform a process including In the etching step, a flow rate of the hydrogen fluoride gas is controlled to be 25% by volume or more relative to a total flow rate of the first process gas excluding an inert gas. Plasma processing equipment.

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