Etching method and plasma treatment device

Abstract

The etching method of the present invention includes a step of preparing a substrate within a cavity of a plasma processing apparatus. The substrate includes a silicon-containing film. The etching method further includes a step of etching the silicon-containing film by means of chemical species from the plasma formed in the cavity by a process gas. The process gas includes halogen elements and phosphorus.

Description

Technical Field

[0001] Exemplary embodiments of the present invention relate to an etching method and a plasma treatment apparatus. Background Technology

[0002] In the manufacture of electronic devices, a silicon-containing film on a substrate is plasma etched. During plasma etching of the silicon-containing film, a process gas containing fluorocarbons is used. This type of plasma etching is described in U.S. Patent Application Publication No. 2016 / 0343580. Summary of the Invention

[0003] This invention provides a technique for suppressing lateral etching during plasma etching of silicon-containing films.

[0004] In one exemplary embodiment, an etching method is provided. The etching method includes a step of preparing a substrate within a chamber of a plasma processing apparatus. The substrate includes a silicon-containing film. The etching method further includes a step of etching the silicon-containing film using chemical species from the plasma formed in the chamber by a process gas. The process gas includes halogen elements and phosphorus.

[0005] According to an exemplary embodiment, it becomes possible to suppress lateral etching during plasma etching of a silicon-containing film. Attached Figure Description

[0006] Figure 1 This is a flowchart of an exemplary embodiment of an etching method.

[0007] Figure 2 It is applicable Figure 1 A partially enlarged cross-sectional view of a substrate for an example of the etching method shown.

[0008] Figure 3 This is a diagram schematically illustrating a plasma processing apparatus according to an exemplary embodiment.

[0009] Figure 4 (a) is applicable Figure 1 A partially enlarged cross-sectional view of a substrate illustrating an example of the etching method. Figure 4 (b) is a partially enlarged cross-sectional view of an example substrate etched by plasma formed from a process gas that does not contain phosphorus.

[0010] Figure 5 (a) is applicable Figure 1 Another example of the etching method shown is a partially enlarged cross-sectional view of the substrate. Figure 5 (b) is applicable Figure 1 Another example of the etching method shown is a partially enlarged cross-sectional view of a substrate.

[0011] Figure 6This is a graph showing the relationship between the flow rate of PF3 gas in the treatment gas and the etching rate of the silicon oxide film, as determined in Experiment 1.

[0012] Figure 7 This is a graph showing the relationship between the flow rate of PF3 gas in the treatment gas determined in Experiment 1 and the maximum width of the opening formed on the silicon oxide film.

[0013] Figure 8 This is a graph showing the ratio of PF3 gas flow rate to etching rate determined in Experiment 3. Detailed Implementation

[0014] The following describes various exemplary embodiments.

[0015] In one exemplary embodiment, an etching method is provided. The etching method includes a step of preparing a substrate within a chamber of a plasma processing apparatus. The substrate includes a silicon-containing film. The etching method further includes a step of etching the silicon-containing film using chemical species from the plasma formed in the chamber by a process gas. The process gas includes halogen elements and phosphorus.

[0016] According to the above embodiment, a protective film comprising silicon and phosphorus contained in the processing gas is formed on the sidewall surface, the sidewall surface being divided by openings formed in the silicon-containing film by etching. The silicon-containing film is etched while the sidewall surface is protected by this protective film. Therefore, it becomes possible to suppress lateral etching during plasma etching of the silicon-containing film.

[0017] In one exemplary embodiment, the etching method may further include a step of forming a protective film on the sidewall surface of the opening formed by etching. The protective film contains phosphorus contained in the process gas.

[0018] In one exemplary embodiment, the etching process and the process of forming a protective film can be performed simultaneously.

[0019] In one exemplary embodiment, the processing gas may contain at least one of PF3, PCl3, PF5, PCl5, POCl3, PH3, PBr3 or PBr5 as a phosphorus-containing molecule.

[0020] In one exemplary embodiment, the processing gas may also contain carbon and hydrogen.

[0021] In one exemplary embodiment, the processing gas may include H2, HF, and C. x H y CH x F y Or at least one of NH3 as a molecule containing hydrogen. Where x and y are natural numbers.

[0022] In one exemplary embodiment, the halogen element can be fluorine.

[0023] In one exemplary embodiment, the processing gas may also contain oxygen.

[0024] In one exemplary embodiment, the silicon-containing film may be a silicon-containing dielectric film.

[0025] In one exemplary embodiment, the silicon-containing film may include at least one of a silicon oxide film, a silicon nitride film, or a silicon film.

[0026] In one exemplary embodiment, the silicon-containing film may include two or more silicon-containing films having different types of films from each other.

[0027] 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.

[0028] In one exemplary embodiment, the substrate may also have a mask disposed on a silicon-containing film.

[0029] In one exemplary embodiment, the temperature of the substrate can be set to below 0°C when the etching process begins.

[0030] In another exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a gas supply unit, and a high-frequency power supply. The substrate support is configured to support a substrate within the chamber. The gas supply unit is configured to supply a processing gas for etching a silicon-containing film into the chamber. The processing gas includes a halogen element and phosphorus. The high-frequency power supply is configured to generate high-frequency power to generate plasma within the chamber from the processing gas.

[0031] Hereinafter, various exemplary embodiments will be described in detail with reference to the accompanying drawings. Furthermore, in the drawings, the same or equivalent parts are labeled with the same symbols.

[0032] Figure 1 This is a flowchart of an exemplary embodiment of an etching method. Figure 1 The etching method shown (hereinafter referred to as "Method MT") includes steps ST1 and ST2. Method MT is applicable to substrates with silicon-containing films. In Method MT, the silicon-containing film is etched.

[0033] Figure 2 It is applicable Figure 1 A partially enlarged cross-sectional view of a substrate for an example of the etching method shown. Figure 2The substrate W shown 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 also have a substrate region UR. The silicon-containing film SF can be disposed on the substrate 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 containing silicon, or it can be a film of other film types. Furthermore, the silicon-containing film SF can include a silicon film (e.g., a polycrystalline silicon film). Furthermore, the silicon-containing film SF can include two or more silicon-containing films having different film types from each other. The two or more silicon-containing films can include silicon oxide films and silicon nitride films. The silicon-containing film SF can, for example, be a multilayer film comprising one or more silicon oxide films and one or more silicon nitride films alternately stacked. Alternatively, the two or more silicon-containing films can include silicon oxide films and silicon films. The silicon-containing film SF can, for example, be a multilayer film comprising one or more silicon oxide films and one or more silicon films alternately stacked. Alternatively, the two or more silicon-containing films can include silicon oxide films, silicon nitride films, and silicon films.

[0034] The substrate W may also have a mask MK. The mask MK is disposed on a 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 process ST2. The mask MK may be formed of an organic material. For example, the mask MK may be formed of an amorphous carbon film, a photoresist film, or a SOC film (spin-coated carbon 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.

[0035] The mask MK is patterned. That is, the mask MK has a pattern that is transferred onto the silicon-containing film SF in step ST2. If the pattern of the mask MK is transferred onto the silicon-containing film SF, openings such as holes or trenches are formed on the silicon-containing film SF. In step ST2, the aspect ratio of the openings formed on the silicon-containing film SF can be 20 or more, or 40 or 50 or more.

[0036] In the MT method, a plasma treatment device is used for etching the silicon-containing SF film. Figure 3 This is a diagram schematically illustrating a plasma processing apparatus according to an exemplary embodiment. Figure 3 The plasma processing apparatus 1 shown includes a chamber 10. The chamber 10 provides an internal space 10s within itself. The chamber 10 includes a chamber body 12. The chamber body 12 has a generally cylindrical shape. The chamber body 12 is formed, for example, of aluminum. A corrosion-resistant film is provided on the inner wall surface of the chamber body 12. The corrosion-resistant film can be formed of ceramics such as alumina or yttrium oxide.

[0037] A channel 12p is formed on the side wall of the chamber body 12. The substrate W is transported between the internal space 10s and the outside of the chamber 10 through the channel 12p. The channel 12p is opened and closed by a gate valve 12g. The gate valve 12g is provided along the side wall of the chamber body 12.

[0038] A support portion 13 is provided at the bottom of the chamber body 12. The support portion 13 is formed of an insulating material. The support portion 13 has a generally cylindrical shape. The support portion 13 extends upward from the bottom of the chamber body 12 within the internal space 10s. The support portion 13 supports a substrate support 14. The substrate support 14 is configured to support the substrate W within the internal space 10s.

[0039] The substrate support 14 has a lower electrode 18 and an electrostatic chuck 20. The substrate support 14 may also have an electrode plate 16. The electrode plate 16 is formed of a conductor such as aluminum and has a generally disc-shaped form. The lower electrode 18 is disposed on the electrode plate 16. The lower electrode 18 is formed of a conductor such as aluminum and has a generally disc-shaped form. The lower electrode 18 is electrically connected to the electrode plate 16.

[0040] An electrostatic chuck 20 is disposed 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 electrodes. The main body of the electrostatic chuck 20 has a generally disc-shaped shape and is formed of a dielectric material. The electrodes of the electrostatic chuck 20 are film electrodes and are disposed within the main body of the electrostatic chuck 20. The electrodes of the electrostatic chuck 20 are connected to a DC power supply 20p via a switch 20s. When a voltage from the DC power supply 20p is applied to the electrodes of the electrostatic chuck 20, an electrostatic attraction is generated between the electrostatic chuck 20 and the substrate W. The substrate W is attracted to the electrostatic chuck 20 by this electrostatic attraction and is held by the electrostatic chuck 20.

[0041] An edge ring 25 is disposed on the substrate support 14. The edge ring 25 is a ring-shaped component. The edge ring 25 can be formed of silicon, silicon carbide, or quartz, etc. The substrate W is disposed on the electrostatic chuck 20 and within the area surrounded by the edge ring 25.

[0042] A flow path 18f is provided inside the lower electrode 18. A heat exchange medium (e.g., refrigerant) is supplied to the flow path 18f from a cooler unit located outside the chamber 10 via a pipe 22a. The heat exchange medium supplied to the flow path 18f returns to the cooler 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.

[0043] A gas supply line 24 is provided in the plasma processing apparatus 1. The gas supply line 24 supplies heat transfer gas (e.g., He gas) from the 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.

[0044] The plasma processing apparatus 1 also includes an upper electrode 30. The upper electrode 30 is disposed above the substrate support 14. The upper electrode 30 is supported on the upper part of the chamber body 12 via a component 32. The component 32 is formed of an insulating material. The upper electrode 30 and the component 32 close the upper opening of the chamber body 12.

[0045] The upper electrode 30 may include a top plate 34 and a support 36. The lower surface of the top plate 34 is the lower surface of one side of the internal space 10s, and divides 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 vent holes 34a extending through the top plate 34 along its thickness direction.

[0046] The support body 36 can be detachably mounted and dismounted to support the top plate 34. The support body 36 is made of a conductive material such as aluminum. A gas diffusion chamber 36a is provided inside the support body 36. The support body 36 has a plurality of gas holes 36b extending downward from the gas diffusion chamber 36a. The plurality of gas holes 36b are respectively connected to a plurality of gas exhaust holes 34a. A gas inlet 36c is formed in the support body 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.

[0047] A gas source group 40 is connected to the gas supply pipe 38 via a flow controller group 41 and a valve group 42. The flow controller group 41 and the valve group 42 constitute the gas supply unit. The gas supply unit may also include the gas source group 40. The gas source group 40 includes multiple gas sources. The multiple gas sources include the source of the process gas used in method MT. The flow controller group 41 includes multiple flow controllers. The multiple flow controllers of the flow controller group 41 are either mass flow controllers or pressure control flow controllers. The valve group 42 includes multiple on / off valves. The multiple gas sources of the gas source group 40 are respectively connected to the gas supply pipe 38 via the flow controllers corresponding to the flow controller group 41 and the on / off valves corresponding to the valve group 42.

[0048] In the plasma processing apparatus 1, a shielding element 46 is detachably provided along the inner wall of the chamber body 12 and the outer periphery of the support portion 13. The shielding element 46 prevents reaction byproducts from adhering to the chamber body 12. The shielding element 46 is constructed, for example, by forming a corrosion-resistant film on the surface of a base material formed of aluminum. The corrosion-resistant film can be formed of ceramics such as yttrium oxide.

[0049] A baffle 48 is provided between the support 13 and the side wall of the chamber body 12. The baffle 48 is constructed, for example, by forming a corrosion-resistant film (such as yttrium oxide) on the surface of a component made of aluminum. Multiple through holes are formed in the baffle 48. An exhaust port 12e is provided below the baffle 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 turbomolecular pump.

[0050] 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 source for generating 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, a frequency in the range of 27MHz to 100MHz. The first high-frequency power supply 62 is connected to the lower electrode 18 via a matching device 66 and an electrode plate 16. The matching device 66 has a circuit for matching the output impedance of the first high-frequency power supply 62 with the impedance of the load side (lower electrode 18 side). In addition, the first high-frequency power supply 62 can be connected to the upper electrode 30 via the matching device 66. An example plasma generation unit is constituted by the first high-frequency power supply 62.

[0051] The second high-frequency power supply 64 is a power source for generating a second high-frequency power. This second high-frequency power has a frequency lower than that of the first high-frequency power. When used in conjunction with the first high-frequency power, the second high-frequency power serves as a bias high-frequency power for introducing ions into the substrate W. The frequency of the second high-frequency power is, for example, in 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 adapter 68 and an electrode plate 16. The matching adapter 68 has circuitry for matching the output impedance of the second high-frequency power supply 64 with the impedance of the load side (the lower electrode 18 side).

[0052] Furthermore, by using a second high-frequency power instead of the first high-frequency power, plasma can be generated using only a single high-frequency power. In this case, the frequency of the second high-frequency power can be greater than 13.56 MHz (e.g., 40 MHz). Also, in this case, the plasma processing apparatus 1 may not include the first high-frequency power supply 62 and the matching device 66. In this case, the second high-frequency power supply 64 constitutes an example of a plasma generation unit.

[0053] In the plasma processing apparatus 1, gas is supplied to the internal space 10s from the gas supply unit. 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 from the gas in the internal space 10s.

[0054] The plasma processing apparatus 1 may also include a control unit 80. The control unit 80 may be a computer equipped with a processor, memory, and other storage units, input devices, a display device, and signal input / output interfaces. The control unit 80 controls each part of the plasma processing apparatus 1. In the control unit 80, the operator can use the input devices to input commands and manage the plasma processing apparatus 1. Furthermore, the control unit 80 can visualize and display the operating status of the plasma processing apparatus 1 via the display device. Moreover, the storage unit stores control programs and recipe data. The control program is executed by the processor to perform various processes within 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.

[0055] Refer again Figure 1 The following describes method MT, using plasma processing apparatus 1 suitable for method MT. Figure 2 The case of substrate W shown will be used as an example for explanation. When using plasma processing apparatus 1, method MT can be executed in plasma processing apparatus 1 by controlling each part of plasma processing apparatus 1 by control unit 80. In the following explanation, the control of each part of plasma processing apparatus 1 by control unit 80 for executing method MT will also be explained.

[0056] Method MT begins in process ST1. In process ST1, substrate W is prepared within chamber 10. Substrate W is placed on electrostatic chuck 20 within chamber 10 and held by electrostatic chuck 20. Additionally, substrate W may have a diameter of 300 mm.

[0057] In method MT, step ST2 is then performed. In step ST2, the silicon-containing film SF is etched by chemical species from the plasma formed by the process gas within chamber 10.

[0058] The processing gas used in process ST2 contains halogen elements and phosphorus. The halogen element in the processing gas can be fluorine. The processing gas may contain at least one of fluorocarbons or hydrofluorocarbons. Fluorocarbons are, for example, at least one of CF4, C3F8, C4F6, or C4F8. Hydrofluorocarbons are, for example, at least one of CH2F2, CHF3, or CH3F. Hydrofluorocarbons may contain more than two carbon atoms. The processing gas may contain phosphorus-containing molecules. Phosphorus-containing molecules may be, for example, tetraphosphorus decaoxide (P4O3). 10Phosphorus oxides include tetraphosphorus octoxide (P4O8) and tetraphosphorus hexaoxide (P4O6). Tetraphosphorus decaoxide is sometimes called diphosphorus pentoxide (P2O5). Phosphorus-containing molecules can be halides such as phosphorus trifluoride (PF3), phosphorus pentafluoride (PF5), phosphorus trichloride (PCl3), phosphorus pentachloride (PCl5), phosphorus tribromide (PBr3), phosphorus pentabromide (PBr5), and phosphorus iodide (PI3). That is, phosphorus-containing molecules can contain fluorine as a halogen element. Alternatively, phosphorus-containing molecules can contain halogen elements other than fluorine. Phosphorus-containing molecules can be phosphoroyl fluoride halides such as phosphoroyl fluoride (POF3), phosphoroyl chloride (POCl3), and phosphoroyl bromide (POBr3). Phosphorus-containing molecules can be phosphine (PH3), calcium phosphide (Ca3P2), phosphoric acid (H3PO4), sodium phosphate (Na3PO4), hexafluorophosphate (HPF6), etc. Phosphorus-containing molecules can be fluorophosphine derivatives (H... x PF y In this case, the sum of x and y is 3 or 5. Examples of fluorophosphine molecules include HPF2 and H2PF3. The process gas may contain one or more of these molecules as phosphorus-containing molecules. For example, the process gas may contain at least one of PF3, PCl3, PF5, PCl5, POCl3, PH3, PBr3, or PBr5 as phosphorus-containing molecules. Furthermore, if the phosphorus-containing molecules are liquid or solid, they can be vaporized by heating or the like and supplied to chamber 10.

[0059] The processing gas used in process ST2 may also contain carbon and hydrogen. The processing gas may contain H2, hydrogen fluoride (HF), and hydrocarbons (C). x H y ), hydrofluorocarbons (CH) x F y At least one of NH3 or NH4 is used as a molecule containing hydrogen. Hydrocarbons are, for example, CH4 or C3H6. Where x and y are natural numbers. The process gas may contain fluorocarbons or hydrocarbons (e.g., CH4) as molecules containing carbon. The process gas may also contain oxygen. For example, the process gas may contain O2.

[0060] The processing gas used in step ST2 includes a phosphorus-containing gas as the source of phosphorus. The phosphorus-containing gas is the gas containing phosphorus molecules as described above. In one embodiment, as described above, step ST2 is applicable to a silicon-containing film SF comprising a silicon oxide film and a silicon nitride film. In step ST2, the ratio of the etching rate of the alternating silicon oxide and silicon nitride film stack to the etching rate of the silicon oxide film is set (controlled) by setting the ratio of the phosphorus-containing gas flow rate to the total flow rate of the processing gas. In step ST2, the ratio of the phosphorus-containing gas flow rate to the total flow rate of the processing gas can be set in such a way that the difference between the etching rate of the silicon oxide film and the etching rate of the alternating silicon oxide and silicon nitride film stack becomes smaller. In one embodiment, the ratio of the phosphorus-containing gas flow rate to the total flow rate of the processing gas is set such that the ratio of the etching rate of the alternating silicon oxide and silicon nitride film stack to the etching rate of the silicon oxide film is 0.8 or more and 1.2 or less. The ratio of the phosphorus-containing gas flow rate to the total flow rate of the processing gas can, for example, be set to 10% or more and 50% or less. Additionally, the ratio of the etching rate of the alternating silicon oxide and silicon nitride films to the etching rate of the silicon oxide film can be changed by altering the flow rate of the phosphorus-containing gas during the etching process ST2.

[0061] In step ST2, the pressure of the gas inside chamber 10 is set to a specified pressure. In step ST2, the pressure of the gas inside chamber 10 can be set to a pressure of 10 mTorr (1.3 Pa) or higher and 100 mTorr (13.3 Pa) or lower. Furthermore, in step ST2, a first high-frequency power and / or a second high-frequency power are supplied to generate plasma from the process gas inside chamber 10. The level of the first high-frequency power can be set to a level of 2 kW or higher and 10 kW or lower. The level of the second high-frequency power can be set to 2 kW (2.83 W / cm² in the power level per unit area of ​​substrate W). 2 The second high-frequency power level can be set to 10kW (14.2W / cm² per unit area of ​​the substrate). 2 The level is above ).

[0062] In order to perform process ST2, the control unit 80 controls the gas supply unit to supply processing gas into the chamber 10. Furthermore, the control unit 80 controls the exhaust device 50 to set the pressure of the gas in the chamber 10 to a specified pressure. Additionally, the control unit 80 controls the first high-frequency power supply 62 and the second high-frequency power supply 64 to supply first high-frequency power and / or second high-frequency power.

[0063] In one embodiment of the method MT, the temperature of the substrate W at the start of step ST2 can be set to a temperature below 0°C. If the temperature of the substrate W is set to this temperature, the etching rate of the silicon-containing film SF in step ST2 becomes higher. To set the temperature of the substrate W at the start of step ST2, the control unit 80 can control the cooler unit.

[0064] In process ST2, the silicon-containing film SF is etched using halogen chemical species derived from the plasma formed from the processing gas. In one embodiment, the portion of the mask MK exposed across the entire region of the silicon-containing film SF is etched (see reference). Figure 4 (a)).

[0065] In one implementation, such as Figure 1 As shown, method MT may further include step ST3. In step ST3, a protective film PF is formed on the sidewall surface that divides the opening formed on the silicon-containing film SF by etching in step ST2 (see reference). Figure 4 (a) The protective film PF contains silicon and phosphorus contained in the processing gas used in step ST2. In one embodiment, step ST3 is performed simultaneously with step ST2. In one embodiment, the protective film PF may also contain carbon and / or hydrogen contained in the processing gas. In one embodiment, the protective film PF may also contain oxygen contained in the processing gas or in the silicon-containing film SF. Based on an experimental example in which a silicon oxide film was etched in step ST2, as a result of XPS analysis of the protective film PF, Si-O bonding peaks and PO bonding peaks were observed. Furthermore, based on an experimental example in which a silicon nitride film was etched in step ST2, as a result of XPS analysis of the protective film PF, Si-P bonding peaks and PN bonding peaks were observed.

[0066] If the gas being processed does not contain phosphorus, then as follows Figure 4 As shown in (b), the silicon-containing film SF is also etched laterally. As a result, the width of the openings formed on the silicon-containing film SF becomes locally wider. For example, the width of the openings formed on the silicon-containing film SF becomes locally wider near the mask MK.

[0067] On the other hand, in method MT, a protective film PF is formed on the sidewall surface that divides the opening formed on the silicon-containing film SF by etching. The silicon-containing film SF is etched while the sidewall surface is protected by this protective film PF. Therefore, according to method MT, it becomes possible to suppress lateral etching during plasma etching of the silicon-containing film SF.

[0068] The following is for reference. Figure 5 (a) and Figure 5 (b) Figure 5 (a) is applicable Figure 1Another example of the etching method shown is a partially enlarged cross-sectional view of the substrate. Figure 5 (b) is applicable Figure 1 A partially enlarged cross-sectional view of a substrate illustrating another example of the etching method. Figure 5 In the substrate W shown in (a), the silicon-containing film SF has a single-layer film SL and a multilayer film ML. The single-layer film SL is, for example, a silicon oxide film, a silicon nitride film, or a polycrystalline silicon film. The multilayer film ML may include one or more silicon oxide films and one or more silicon nitride films stacked together. The multilayer film ML may include multiple silicon oxide films and multiple silicon nitride films stacked alternately. Alternatively, the multilayer film ML may include one or more silicon oxide films and one or more polycrystalline silicon films stacked alternately. Alternatively, the multilayer film ML may include one or more silicon oxide films, one or more polycrystalline silicon films, and one or more silicon nitride films stacked together.

[0069] The above method MT can be applied to Figure 5 The substrate W is shown in (a). In step ST2 of method MT, the single-layer film SL and the multilayer film ML are etched simultaneously. In step ST2, as described above, a processing gas containing halogen elements and phosphorus is used. In one example, the processing gas may contain H2 and C. x H y F z (x, y, z are integers greater than or equal to 0), except for C x H y F z The process gas contains fluorine molecules or fluorine-containing molecules other than fluorine, halogen elements other than fluorine or halogen-containing molecules other than fluorine, and molecules containing phosphorus as described above. Fluorine-containing molecules in the process gas are, for example, NF3, SF6, and HF. Halogen elements or halogen-containing molecules in the process gas are, for example, Cl2, HBr, HI, ClF3, and IF7. That is, the halogen elements or halogen-containing molecules in the process gas may not contain fluorine. Alternatively, the halogen elements or halogen-containing molecules in the process gas may contain fluorine. The ratio of the flow rate of the gas containing phosphorus-containing molecules to the total flow rate of the process gas is, for example, 3% or more and 20% or less. Furthermore, at the start of process ST2, the temperature of the substrate W is set to a temperature below 0°C (e.g., -40°C or -70°C).

[0070] In the method MT, such as Figure 5 As shown in (b), the monolayer film SL and the multilayer film ML are etched while the sidewalls are protected by the protective film PF. Therefore, according to method MT, it becomes possible to suppress lateral etching while simultaneously performing plasma etching on the monolayer film SL and the multilayer film ML. Furthermore, in step ST2, the difference between the etching rates of the monolayer film SL and the multilayer film ML is reduced by using the aforementioned processing gas.

[0071] The first experiment conducted to evaluate method MT will be described below. In the first experiment, multiple sample substrates were prepared. Each sample substrate had a silicon oxide film and a mask disposed on the silicon oxide film. In the first experiment, method MT was performed to etch the silicon oxide films of the multiple sample substrates. The processing gas used to etch the silicon oxide films of the multiple sample substrates (step ST2) contained PF3 gas with different flow rates. Another condition in step ST2 is shown below.

[0072] <Conditions for Process ST2>

[0073] The gas pressure in chamber 10 of process ST2 is 25 mTorr (3.3 Pa).

[0074] The processing gases used in process ST2 are: CH4 gas at 50 sccm, CF4 gas at 100 sccm, and O2 gas at 50 sccm.

[0075] The first high-frequency power in process ST2: 40MHz, 4500W

[0076] The second high-frequency power in process ST2: 400kHz, 7000W

[0077] Temperature of the substrate in process ST2 (temperature of the substrate support before etching begins): -30°C; Duration of process ST2: 600 seconds

[0078] In Experiment 1, the maximum width of the opening formed on the silicon oxide film and the etching rate of the silicon oxide film were determined for each of the multiple sample substrates. Then, the relationship between the flow rate of PF3 gas in the processing gas used in step ST2 and the etching rate of the silicon oxide film was determined. Furthermore, the relationship between the flow rate of PF3 gas in the processing gas used in step ST2 and the maximum width of the opening formed on the silicon oxide film was determined. The relationship between the flow rate of PF3 gas in the processing gas and the etching rate of the silicon oxide film is shown below. Figure 6 Furthermore, the relationship between the flow rate of PF3 gas in the treatment gas and the maximum width of the opening formed on the silicon oxide film is shown in [the figure]. Figure 7 In the middle. For example Figure 6 As shown, it was confirmed that including phosphorus in the process gas increases the etching rate of the silicon oxide film. Furthermore, it was confirmed that when the flow rate of PF3 gas in the process gas is 20 sccm or higher, the etching rate is approximately 1.5 times higher compared to the case without PF3. And, as... Figure 7As shown, it was confirmed that by including phosphorus in the process gas to protect the sidewalls, the maximum width of the opening in the silicon oxide film can be suppressed from decreasing, i.e., the width of the opening in the silicon oxide film locally widens. In particular, it was confirmed that when the flow rate of PF3 gas in the process gas is 15 sccm, the effect of suppressing the local widening of the opening width in the silicon oxide film, i.e., the protection effect on the sidewalls, is increased. Furthermore, it was confirmed that when the flow rate of PF3 gas in the process gas is 50 sccm or more, the local widening of the opening width in the silicon oxide film can be suppressed more significantly. That is, it was confirmed that when the flow rate of PF3 gas in the process gas is 50 sccm or more, the protection effect on the sidewalls becomes significant.

[0079] The second experiment conducted for evaluating method MT will now be described. In the second experiment, a first sample substrate and a second sample substrate were prepared. The first sample substrate has a single-layer film as a silicon oxide film. The second sample substrate has a multilayer film comprising alternating layers of multiple silicon oxide films and multiple silicon nitride films. In the second experiment, the single-layer film of the first sample substrate and the multilayer film of the second sample substrate were etched using a plasma processing apparatus 1 and method MT. The processing gas used for etching (step ST2) contained H2, hydrofluorocarbons, fluorine-containing molecules, halogen-containing molecules, and the aforementioned phosphorus-containing molecules. A comparative experiment was then conducted. In the comparative experiment, the single-layer film of the first sample substrate and the multilayer film of the second sample substrate were etched using a processing gas different from the processing gas used in step ST2 of the second experiment. From the viewpoint of not containing phosphorus-containing molecules, the processing gas used in the comparative experiment is different from the processing gas used in step ST2 of the second experiment.

[0080] In the second and comparative experiments, the ratio of the etching rate of the multilayer film to the etching rate of the single-layer film was determined. In the comparative experiment, when the temperatures of the first and second sample substrates at the start of etching were both -40°C, the ratio was approximately 1.3. On the other hand, in the second experiment, when the temperatures of the first and second sample substrates at the start of etching were both -40°C, the ratio was approximately 1.17. Furthermore, in the second experiment, when the temperatures of the first and second sample substrates at the start of etching were both -70°C, the ratio was approximately 1.05. Based on these experimental results, it was confirmed that in process ST2, the difference between the etching rates of the single-layer film and the multilayer film can be reduced by using a process gas containing phosphorus molecules. Furthermore, it was confirmed that the lower the substrate temperature at the start of etching, the smaller the difference between the etching rates of the single-layer film and the multilayer film.

[0081] The third experiment conducted to evaluate method MT will now be described. In the third experiment, multiple first sample substrates and multiple second sample substrates were prepared. Each of the multiple first sample substrates had a silicon oxide film (monolayer). Each of the multiple second sample substrates had alternating layers of silicon oxide and silicon nitride films. In the third experiment, plasma processing apparatus 1 was used to etch the monolayer films of the multiple first sample substrates and the layered films of the multiple second sample substrates using method MT. The processing gases used in the etching (step ST2) included H2 gas, hydrofluorocarbon gas, fluorine-containing gas, halogen-containing gas without fluorine, and halogen and phosphorus-containing gas (PF3 gas). In the third experiment, multiple combinations of different etching temperatures and PF3 gas flow rates were used in the etching of the monolayer films of the multiple first sample substrates. The etching temperature was the temperature of the sample substrate at the start of etching (temperature of the heat medium). Furthermore, the PF3 gas flow rate ratio was the ratio of the PF3 gas flow rate to the total flow rate of the processing gases. Furthermore, the etching of the multilayer films of the multiple second sample substrates employed multiple combinations of etching temperatures and PF3 gas flow rates that were used in the etching of the single-layer films of the multiple first sample substrates. Additionally, the effective power of the second high-frequency power during the etching of the alternating multilayer films of the multiple first sample substrates and the multiple second sample substrates was 6 kW.

[0082] In Experiment 3, the etching rates of the single-layer films of multiple first sample substrates were determined based on the etching results of the single-layer films. Furthermore, the etching rates of the stacked films of multiple second sample substrates were determined based on the etching results of the stacked films. Then, the ratio of the etching rate of the alternating silicon oxide and silicon nitride stacked films to the etching rate of the silicon oxide film (single-layer film) under each of the above combinations was calculated. Finally, the relationship between the PF3 gas flow rate ratio and the etching rate ratio was determined. The ratio of the PF3 gas flow rate ratio and the etching rate obtained in Experiment 3 is shown below. Figure 8 In the chart. For example Figure 8 As shown in the third experimental result, it was confirmed that the etching rate ratio can be adjusted by adjusting the flow rate ratio of PF3 gas. Furthermore, it was confirmed that the etching rate ratio can be set to 0.8 or higher and 1.2 or lower without depending on the temperature of the sample substrate at the start of etching by setting the flow rate ratio of PF3 gas to 10% or higher and 50% or lower.

[0083] The above descriptions have illustrated various exemplary embodiments, but the embodiments are not limited to these exemplary embodiments. Various additions, omissions, substitutions, and modifications can be made. Furthermore, elements from different embodiments can be combined to form other embodiments.

[0084] For example, the plasma processing device used in method MT can be a capacitively coupled plasma processing device other than plasma processing device 1. Alternatively, the plasma processing device used in method MT can be an inductively coupled plasma processing device, an electron cyclotron resonance (ECR) plasma processing device, or a plasma processing device that generates plasma using surface waves such as microwaves.

[0085] Furthermore, instead of the second high-frequency power supply 64, the plasma processing apparatus may also include a DC power supply configured to intermittently or periodically apply pulses of negative polarity DC voltage to the lower electrode 18. Alternatively, in addition to the second high-frequency power supply 64, the plasma processing apparatus may also include a DC power supply configured to intermittently or periodically apply pulses of negative polarity DC voltage to the lower electrode 18.

[0086] As can be understood from the above description, various embodiments of the present invention have been described in this specification for illustrative purposes, and various modifications can be made without departing from the scope and spirit of the invention. Therefore, the invention is not limited to the various embodiments disclosed in this specification, and the true scope and spirit are indicated by the appended claims.

Claims

1. An etching method, comprising: The process of preparing a substrate within a plasma processing apparatus chamber, wherein the substrate includes a silicon-containing film, the silicon-containing film comprising a single-layer film of silicon oxide film and a multilayer film comprising alternating layers of silicon oxide film and silicon nitride film; and The process of etching the silicon-containing film using chemical species from a plasma formed by a process gas within the chamber, wherein the process gas contains hydrogen fluoride, halogen-containing molecules other than hydrogen fluoride, and phosphorus. The processing gas contains a phosphorus-containing gas as the source of the phosphorus. The ratio of the flow rate of the phosphorus-containing gas to the total flow rate of the processing gas is set to be 10% or more and 50% or less, such that the ratio of the etching rate of the multilayer film to the etching rate of the single layer film of the silicon oxide film is 0.8 or more and 1.2 or less.

2. The etching method according to claim 1, further comprising the step of forming a protective film on a sidewall surface dividing an opening formed by the etching, the protective film comprising phosphorus contained in the processing gas.

3. The etching method according to claim 2, wherein, The etching process and the protective film formation process are performed simultaneously.

4. The etching method according to any one of claims 1 to 3, wherein, The processing gas contains at least one of PF3, PCl3, PF5, PCl5, POCl3, PH3, PBr3, or PBr5 as a molecule containing the phosphorus.

5. The etching method according to any one of claims 1 to 3, wherein, The processed gas also contains carbon.

6. The etching method according to any one of claims 1 to 3, wherein, The halogenated molecules other than hydrogen fluoride include fluorine.

7. The etching method according to any one of claims 1 to 3, wherein, The processing gas also contains oxygen.

8. The etching method according to any one of claims 1 to 3, wherein, The etching of the silicon-containing film also includes a step of changing the flow rate of the phosphorus-containing gas to change the ratio of the etching rate of the multilayer film to the etching rate of the single-layer film.

9. The etching method according to any one of claims 1 to 3, wherein, In the etching process, both the single-layer film and the multilayer film are etched simultaneously.

10. The etching method according to any one of claims 1 to 3, wherein, The substrate also has a mask disposed on the silicon-containing film.

11. The etching method according to any one of claims 1 to 3, wherein, When the etching process begins, the temperature of the substrate is set to below 0°C.

12. A plasma processing apparatus comprising: chamber; A substrate support, configured to support a substrate within the cavity; A gas supply unit is configured to supply processing gas for etching the silicon-containing film of the substrate into the chamber, wherein... The processing gas contains hydrogen fluoride, halogen-containing molecules other than hydrogen fluoride, and phosphorus, and includes a phosphorus-containing gas as a source of said phosphorus. The silicon-containing film includes a single-layer film of silicon oxide and a multilayer film comprising alternating layers of silicon oxide and silicon nitride films; and A high-frequency power supply, configured to generate high-frequency power to generate plasma from the process gas within the chamber, through which chemical species from the plasma are used to etch the silicon-containing film. The ratio of the flow rate of the phosphorus-containing gas to the total flow rate of the processing gas is set to be 10% or more and 50% or less, such that the ratio of the etching rate of the multilayer film to the etching rate of the single layer film of the silicon oxide film is 0.8 or more and 1.2 or less.

13. The plasma processing apparatus according to claim 12, wherein, In the etching of the silicon-containing film, the flow rate of the phosphorus-containing gas is changed to change the ratio of the etching rate of the multilayer film to the etching rate of the single-layer film.

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