Etching method

Abstract

The invention provides an etching method capable of suppressing degradation of characteristics contributing to precursor generation in plasma generated in a discharge tube. The etching method includes: generating a reaction plasma containing hydrogen and nitrogen in a discharge tube (24A) having an inner surface made of an inorganic oxide, and supplying the reaction plasma to an etching chamber (11) to which the discharge tube (24A) is connected; and generating a precursor containing fluorine and hydrogen in the etching chamber (11) using the gas containing fluorine and the reaction plasma, and supplying the precursor to the substrate disposed in the etching chamber (11). The etching method includes: supplying hydrogen plasma to an inner surface of a discharge tube (24A) in which reaction plasma is generated; and supplying oxygen plasma to the inner surface to which the hydrogen plasma is supplied.

Description

Technical Field

[0001] The present disclosure relates to etching methods. Background Art

[0002] An example of an etching device for removing a natural oxide film from a silicon substrate is an etching agent for generating a natural oxide film from free radicals in a plasma generated by microwave irradiation. When generating the etching agent, a gas for generating plasma is supplied to a discharge tube having an inner surface composed of an inorganic oxide. Next, the discharge tube is irradiated with microwaves to generate plasma in the discharge tube. Japanese Patent Application Publication No. 2011-096937 describes an example of an etching device for gasifying a complex generated by an etching agent and a natural oxide film by heating a silicon substrate. Summary of the invention Problems to be solved by the invention

[0003] In addition, a nitrogen-containing gas such as ammonia is used to generate plasma for generating an etchant. When plasma is generated by the nitrogen-containing gas in a discharge tube made of an inorganic oxide such as sapphire or quartz, the inner surface of the discharge tube is nitrided. Therefore, the plasma generated in the discharge tube whose inner surface is nitrided has a lower property of contributing to the generation of precursors than before nitridation. Means for solving problems

[0004] An etching method based on one viewpoint includes: generating a reactive plasma containing hydrogen and nitrogen in a discharge tube having an inner surface composed of an inorganic oxide, supplying the reactive plasma to a processing chamber connected to the discharge tube; and generating a precursor containing fluorine and hydrogen in the processing chamber using a gas containing fluorine and the reactive plasma, and supplying the precursor to an etching object arranged in the processing chamber. The etching method includes: supplying hydrogen plasma to the inner surface of the discharge tube in which the reactive plasma is generated; and supplying oxygen plasma to the inner surface to which the hydrogen plasma is supplied.

[0005] According to the above etching method, the inner surface of the discharge tube nitrided by the generation of reactive plasma is reduced by modification of hydrogen plasma. The inner surface reduced by hydrogen plasma is oxidized by oxygen plasma. Thereafter, the inner surface composed of inorganic oxide is restored to the state before nitridation. As a result, the inner surface properties in the discharge tube become stable, and the characteristics of the reactive plasma become stable accordingly. Therefore, the reduction in the etching amount can be suppressed in accordance with the stabilization of the characteristics of the reactive plasma. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a device configuration diagram showing the configuration of an etching device. Figure 2It is shown Figure 1 FIG. 2 is a diagram showing the structure of an etching chamber included in the etching apparatus shown in FIG. Figure 3 It is a flowchart for explaining the processing procedure in the etching method. Figure 4 Graph showing the relationship between the elapsed time and the etching amount in Example 1 and Comparative Example 1. Figure 5 This is a diagram showing the relationship between the groove number and the etching amount in Evaluation 2. DETAILED DESCRIPTION

[0007] Reference Figures 1 to 5 , an embodiment of the etching method is described. [Etching equipment] like Figure 1 As shown, the etching apparatus 10 includes an etching chamber 11, a load lock chamber 12, and a gate valve 13. The etching apparatus 10 includes a mixed gas supply unit 21, a fluorine-containing gas supply unit 23, and a plasma supply unit 24. The etching apparatus 10 includes a control device 10C.

[0008] The etching chamber 11 is divided into sections for storing a substrate S (see Figure 2 ) space. The etching chamber 11 etches the silicon oxide film in the space for storing the substrate S. The load lock chamber 12 carries the substrate S before etching from the outside into the etching chamber 11. The load lock chamber 12 carries the substrate S after etching from the etching chamber 11 to the outside.

[0009] The gate valve 13 is disposed between the etching chamber 11 and the load lock chamber 12. When the gate valve 13 is opened, the etching chamber 11 and the load lock chamber 12 are communicated with each other. When the gate valve 13 is closed, the etching chamber 11 and the load lock chamber 12 are isolated from each other.

[0010] The load lock chamber 12 is connected to a cooling gas supply unit 12A. The cooling gas supply unit 12A supplies cooling gas to the load lock chamber 12. The cooling gas is an inert gas for cooling the substrate S after etching.

[0011] The etching chamber 11 includes a first heating unit 11A, an exhaust unit 11B, and a second heating unit 11C. The first heating unit 11A heats the etching chamber 11. The exhaust unit 11B decompresses the etching chamber 11 to a predetermined pressure. The second heating unit 11C heats the substrate S accommodated in the etching chamber 11. The etching chamber 11 is an example of a processing chamber.

[0012] The etching chamber 11 is connected to a fluorine-containing gas supply unit 23 and a plasma supply unit 24. The fluorine-containing gas supply unit 23 supplies a fluorine-containing gas to a space in the etching chamber 11 where the substrate S is stored. An example of the fluorine-containing gas is nitrogen trifluoride gas. The plasma supply unit 24 supplies a reactive plasma to a space in the etching chamber 11 where the substrate S is stored.

[0013] The plasma supply unit 24 includes a discharge tube 24A, a waveguide 24B, and a microwave source 24C. The microwave source 24C irradiates microwaves to the discharge tube 24A through the waveguide 24B. The discharge tube 24A is connected to the mixed gas supply unit 21. The inner surface of the discharge tube 24A is composed of an inorganic oxide. The inorganic oxide constituting the inner surface of the discharge tube 24A may be silicon oxide or aluminum oxide. The discharge tube 24A may be, for example, a quartz tube.

[0014] The mixed gas supply unit 21 supplies a first mixed gas containing hydrogen atoms and nitrogen atoms to the discharge tube 24A. In addition, the mixed gas supply unit 21 supplies a second mixed gas containing hydrogen atoms and oxygen atoms to the discharge tube 24A. Alternatively, the mixed gas supply unit 21 supplies a gas containing hydrogen atoms to the discharge tube 24A, and then supplies a gas containing oxygen atoms.

[0015] The mixed gas supply unit 21 is composed of a nitrogen-containing gas supply unit 21A, a hydrogen-containing gas supply unit 21B, and an oxygen-containing gas supply unit 21C. An example of nitrogen-containing gas is nitrogen. An example of hydrogen-containing gas is ammonia. The hydrogen-containing gas may also be hydrogen. An example of oxygen-containing gas is oxygen. The oxygen-containing gas may also be a gas of an oxygen compound. The oxygen compound may be, for example, water or a nitrogen oxide.

[0016] The plasma supply unit 24 generates a reaction plasma in the discharge tube 24A by irradiating the first mixed gas with microwaves in the discharge tube 24A. The reaction plasma contains hydrogen radicals, nitrogen radicals, and nitrogen-hydrogen radicals. A precursor containing fluorine atoms and hydrogen atoms is generated in the etching chamber 11 using the reaction plasma and the fluorine-containing gas, and the precursor is supplied to the substrate S.

[0017] The plasma supply unit 24 generates hydrogen plasma in the discharge tube 24A by irradiating microwaves to the hydrogen-containing gas in the discharge tube 24A. The hydrogen plasma contains plasmatized hydrogen atoms or hydrogen molecules that have the function of cutting the bonds between inorganic atoms and nitrogen atoms in the inorganic nitride formed by nitriding the inorganic oxide with plasmatized hydrogen atoms. The hydrogen plasma may be a plasma generated from hydrogen gas, may be composed of plasmatized hydrogen atoms, or may contain plasmatized hydrogen molecules. The hydrogen plasma may be a plasma generated from ammonia gas, or may contain plasmatized hydrogen atoms and plasmatized hydrogen nitride.

[0018] The plasma supply unit 24 generates oxygen plasma in the discharge tube 24A by irradiating microwaves to the oxygen-containing gas in the discharge tube 24A. The oxygen plasma contains plasmatized oxygen atoms, plasmatized oxygen molecules, ozone, or plasmatized oxygen compounds, which have the function of oxidizing inorganic nitrides reduced by plasmatized hydrogen atoms and restoring them to inorganic oxides. The oxygen compound may be water or a nitrogen oxide. The oxygen plasma may be a plasma generated from oxygen gas, may be composed of plasmatized oxygen atoms, may contain plasmatized oxygen molecules, or may contain ozone. The oxygen plasma may be a plasma generated from an oxygen compound, or may contain plasmatized oxygen atoms and a plasmatized oxygen compound.

[0019] The plasma supply unit 24 irradiates the second mixed gas with microwaves in the discharge tube 24A to generate reformed plasma in the discharge tube 24A. The reformed plasma includes hydrogen plasma and oxygen plasma.

[0020] The modified plasma can be generated in the discharge tube 24A by adding a trace amount of oxygen to the first mixed gas for generating a reaction plasma containing hydrogen and nitrogen. In the case where the first mixed gas is a mixed gas of ammonia and nitrogen, the modified plasma can be generated by adding a trace amount of oxygen to the first mixed gas. Thus, since the environment for etching the substrate S and the environment for modifying the inner surface of the discharge tube 24A are close to each other inside the etching chamber 11, it is easier to stabilize the state of the plasma during etching than in the case where their environments are significantly different. The flow rate of the trace amount of oxygen can be 0.5% or more and 10% or less, or 1% or more and 10% or less, relative to the flow rate of the gas for generating hydrogen plasma. The flow rate of the trace amount of oxygen can be 0.5% or more and 10% or less, relative to the flow rate of the ammonia gas for generating hydrogen plasma.

[0021] The control device 10C includes a storage unit 10CM. The storage unit 10CM stores process conditions for etching the silicon oxide film. The process conditions include the pressure of the etching chamber 11, the temperature of the substrate S, the flow rates of various gases, and the output of the microwave source 24C. The control device 10C controls the driving of the first heating unit 11A, the exhaust unit 11B, the second heating unit 11C, the mixed gas supply unit 21, the fluorine-containing gas supply unit 23, and the plasma supply unit 24 in a manner that the etching conditions are consistent with the process conditions.

[0022] [Etching chamber 11] like Figure 2As shown, the etching chamber 11 accommodates a support portion 10A. The support portion 10A can support a plurality of substrates S. The plurality of substrates S supported by the support portion 10A are stacked with gaps between mutually adjacent substrates S. The substrate S has a silicon oxide film. An example of the substrate S is a disk-shaped silicon substrate.

[0023] The etching chamber 11 includes a shower head 11D. The shower head 11D is connected to a discharge tube 24A. The number of discharge tubes 24A connected to the shower head 11D may be one or more than two. Figure 2 The example in which two discharge tubes 24A are connected to the shower head 11D is shown. The shower head 11D has a plurality of supply ports. The supply ports of the shower head 11D are arranged along the stacking direction of the substrates S. The supply ports of the shower head 11D supply the plasma supplied from the discharge tubes 24A toward the substrates S.

[0024] The etching chamber 11 includes a rotating part 11E. The rotating part 11E rotates the support part 10A in the circumferential direction of the substrate S. The rotating part 11E disperses the plasma supplied from the shower head 11D toward the substrate S and the fluorine-containing gas supplied from the fluorine-containing gas supply part 23 toward the substrate S in the circumferential direction of the substrate S. Thus, in the etching chamber 11, the precursor is supplied from the periphery of the substrate S toward the space between the substrates S adjacent to each other.

[0025] The etching chamber 11 includes a temperature measuring unit 11F. The temperature measuring unit 11F measures the temperature inside the etching chamber 11 and uses it as the temperature of the substrate S. The temperature measuring unit 11F is connected to the control device 10C. The temperature measurement result obtained by the temperature measuring unit 11F is input to the control device 10C. The control device 10C controls the driving of the first heating unit 11A and the second heating unit 11C based on the measurement result obtained by the temperature measuring unit 11F.

[0026] [Etching method] The etching method includes supplying a reactive plasma to a processing chamber, supplying a precursor to an etching object, supplying a hydrogen plasma, and supplying an oxygen plasma. When supplying the reactive plasma, a reactive plasma containing hydrogen and nitrogen is generated in a discharge tube having an inner surface composed of an inorganic oxide, and the reactive plasma is supplied to a processing chamber connected to the discharge tube. When supplying the precursor, a precursor containing fluorine and hydrogen is generated in the processing chamber using a gas containing fluorine and a reactive plasma, and the precursor is supplied to an etching object arranged in the processing chamber. When supplying the hydrogen plasma, the hydrogen plasma is supplied to the inner surface of the discharge tube in which the reactive plasma is generated in a state where no etching object exists in the processing chamber. When supplying the oxygen plasma, the oxygen plasma is supplied to the inner surface of the discharge tube to which the hydrogen plasma is supplied.

[0027] According to the etching method disclosed in the present invention, the inner surface of the discharge tube that has been nitrided by the generation of reactive plasma is reduced by modification of hydrogen plasma. The inner surface that has been reduced by hydrogen plasma is oxidized by oxygen plasma. Thereafter, the inner surface composed of inorganic oxide is restored to the state before nitridation. As a result, the inner surface properties in the discharge tube become stable, and the characteristics of the reactive plasma become stable accordingly. Therefore, the reduction in the etching amount can be suppressed in accordance with the stabilization of the characteristics of the reactive plasma. The etching method is described in more detail below with reference to the accompanying drawings.

[0028] like Figure 3 As shown, the etching method includes a hydrogen plasma supply process (step S11) and an oxygen plasma supply process (step S12). In the hydrogen plasma supply process, hydrogen plasma is supplied to the inner surface of the discharge tube 24A. In the oxygen plasma supply process, oxygen plasma is supplied to the inner surface of the discharge tube 24A supplied with hydrogen plasma.

[0029] The hydrogen plasma supplying step and the oxygen plasma supplying step may be performed separately. That is, after the supply of hydrogen plasma to the inner surface of the discharge tube 24A is completed, the supply of oxygen plasma to the inner surface of the discharge tube 24A may be started.

[0030] Alternatively, the hydrogen plasma supply process and the oxygen plasma supply process may also be performed simultaneously. That is, in the discharge tube 24A, hydrogen-containing gas and oxygen-containing gas may be supplied simultaneously, and then hydrogen plasma and oxygen plasma are generated in the discharge tube 24A by the hydrogen-containing gas and the oxygen-containing gas. In this case, the hydrogen plasma and the oxygen plasma are supplied to the inner surface of the discharge tube 24A almost simultaneously. Afterwards, the inner surface reduced by hydrogen plasma is oxidized, and an environment, time, etc. for maintaining the reduced state are not required. Therefore, it is also possible to simplify the process required to restore the nitrided inner surface to the state before nitridation, and shorten the time required to restore the nitrided inner surface to the state before nitridation.

[0031] In the hydrogen plasma supply process, hydrogen or ammonia supplied to the discharge tube 24A can generate hydrogen plasma in the discharge tube 24A. In addition, in the oxygen plasma supply process, oxygen or water supplied to the discharge tube 24A can generate oxygen plasma in the discharge tube 24A. In these cases, the effectiveness of suppressing the reduction of the etching amount is improved.

[0032] The etching method includes a reactive plasma supplying step (step S13) and a precursor supplying step (step S14) after the hydrogen plasma supplying step and the oxygen plasma supplying step. In the reactive plasma supplying step, the reactive plasma generated in the discharge tube 24A is supplied to the etching chamber 11. In the precursor supplying step, the reactive plasma is supplied to the etching chamber 11, and the fluorine-containing gas is supplied to the etching chamber 11, thereby generating a precursor in the etching chamber 11. Thereafter, the generated precursor is supplied to the substrate S accommodated in the etching chamber 11. Thus, a reaction product having a higher volatility than the silicon oxide film is generated on the substrate S by the reaction between the silicon oxide film of the substrate S and the precursor.

[0033] In the precursor supply process, as described above, the precursor is supplied from the periphery of the substrate S having the silicon oxide film toward the interval between the mutually adjacent substrates S. In the process of simultaneously etching a plurality of substrates S in one etching chamber 11, the reduction in the etching amount due to one treatment will affect the treatment results of all substrates S. Therefore, compared with the process of etching a plurality of substrates S one by one, the process of simultaneously etching a plurality of substrates S in one etching chamber 11 more strongly requires suppression of the variation in the etching amount between treatments. In this regard, in the etching method of the present embodiment, the reduction in the etching amount can be suppressed in the process of etching a plurality of substrates S in one etching chamber 11. Therefore, the usefulness of supplying hydrogen plasma and oxygen plasma to the inner surface of the discharge tube 24A is further improved.

[0034] The reactive plasma supply process and the precursor supply process are performed a predetermined number of times. The reactive plasma supply process and the precursor supply process may be performed once or twice or more. If the reactive plasma supply process and the precursor supply process are performed a predetermined number of times (step S15: yes), the hydrogen plasma supply process is performed (step S16), followed by the oxygen plasma supply process (step S17).

[0035] In the hydrogen plasma supply process of step S16, hydrogen plasma is supplied to the inner surface of the discharge tube 24A in the same manner as the hydrogen plasma supply process of step S11. In the oxygen plasma supply process of step S17, oxygen plasma is supplied to the inner surface of the discharge tube 24A to which the hydrogen plasma is supplied in the same manner as the oxygen plasma supply process of step S12.

[0036] The hydrogen plasma supply process and the oxygen plasma supply process may be performed separately. That is, after the supply of hydrogen plasma to the inner surface of the discharge tube 24A is completed, the supply of oxygen plasma to the inner surface of the discharge tube 24A may be started. Alternatively, the hydrogen plasma supply process and the oxygen plasma supply process may be performed simultaneously.

[0037] Thus, in the etching method, each time the discharge tube 24A generates a predetermined number of reactive plasmas, only one supply of hydrogen plasma and one supply of oxygen plasma are performed. Thus, each time the reactive plasmas are generated a predetermined number of times, the inner surface of the discharge tube 24A is modified by reduction and oxidation, so that the characteristics of the reactive plasmas become more stable.

[0038] In the etching method, the supply of hydrogen plasma and the supply of oxygen plasma are performed before and after the discharge tube 24A generates the reactive plasma a predetermined number of times, thereby further stabilizing the characteristics of the reactive plasma.

[0039] It should be noted that the hydrogen plasma supply process (step S111) and the oxygen plasma supply process (step S12) performed before the reactive plasma supply process can also be omitted. When the processes of steps S11 and S12 are performed, the environment in the etching chamber 11 when performing step S13 can be kept substantially constant regardless of the period from the completion of the process of step S17 to the process of step S13. Therefore, the deviation of the etching amount of the silicon oxide film can be further suppressed.

[0040] [Example] [Example 1] An etching apparatus 10 is prepared in which two quartz tubes as an example of discharge tubes 24A are connected to an etching chamber 11. A mixed gas supply unit 21 is connected to each discharge tube 24A. Figure 3 n in is set to 1, that is, the discharge tube 24A is subjected to the modification process. When the discharge tube 24A is subjected to the modification process, the hydrogen-containing gas and the oxygen-containing gas are simultaneously supplied, and then the modified plasma is generated by the hydrogen-containing gas and the oxygen-containing gas. At this time, the gas supplied to each discharge tube 24A and the flow rate of each gas supplied to each discharge tube 24A are set as follows.

[0041] [Modification treatment conditions] Ammonia (hydrogen-containing gas): 1300sccm Oxygen (oxygen-containing gas): 9sccm Nitrogen: 3900sccm

[0042] [Comparative Example 1] When etching the silicon oxide film using the same etching apparatus 10 as in Example 1, etching of the substrate S was performed by the same method as in Example 1 except that the modification treatment of the discharge tube 24A was not performed.

[0043] [Evaluation 1] The change of etching amount over time was measured, and the results were as follows Figure 4It should be noted that Figure 4 , the etching amount of Example 1 is represented by a solid circle, and the etching amount of Comparative Example 1 is represented by a hollow circle.

[0044] like Figure 4 As shown, in Example 1 in which the reforming process of the discharge tube 24A was performed, it was confirmed that the etching amount per process was stable, compared with Comparative Example 1 in which the reforming process of the discharge tube 24A was not performed.

[0045] [Evaluation 2] In the etching apparatus 10 used in Example 1, the etching amount at the substrate S of each groove number in the support part 10A is measured. At this time, the etching amount at the initial stage of etching, the etching amount after etching is performed multiple times and before the modification treatment, and the etching amount after etching is performed multiple times and after the modification treatment are measured. It should be noted that, Figure 5 In the figure, the etching amount in the initial stage of etching is represented by a hollow circle, the etching amount before the modification treatment is represented by a solid triangle, and the etching amount after the modification treatment is represented by a solid quadrilateral.

[0046] like Figure 5 As shown, it has been confirmed that among the stacked multiple substrates, the etching amount is significantly recovered after the modification treatment at the position of the substrate where the etching amount is greatly reduced, and on the other hand, the etching amount is also recovered less after the modification treatment at the position of the substrate where the etching amount is less reduced. In addition, it has been confirmed that the etching amount in the substrate S of all slot numbers is included in the specified range by performing the modification treatment.

[0047] As described above, according to one embodiment of the etching method, the following effects can be obtained. (1) The inner surface of the discharge tube 24A that has been nitrided by the generation of the reactive plasma is reduced by modification with the hydrogen plasma. The inner surface that has been reduced by the hydrogen plasma is oxidized by the oxygen plasma. And the inner surface composed of the inorganic oxide is restored to the state before nitridation. As a result, the inner surface properties of the discharge tube 24A become stable, and the characteristics of the reactive plasma become stable accordingly. Therefore, the reduction in the etching amount can be suppressed accordingly as the characteristics of the reactive plasma become stable.

[0048] (2) Since the inner surface of the discharge tube 24A is reformed by reduction and oxidation every time the reactive plasma is generated a predetermined number of times, the characteristics of the reactive plasma become more stable. (3) Since the inner surface of the discharge tube is reformed by reduction and oxidation before and after the reaction plasma is generated a predetermined number of times, the characteristics of the reaction plasma become more stable.

[0049] (4) When plasma is generated from a mixed gas containing hydrogen-containing gas and oxygen-containing gas, hydrogen plasma and oxygen plasma are supplied to the inner surface of the discharge tube 24A almost simultaneously. After that, the inner surface reduced by hydrogen plasma is oxidized, and an environment, time, etc. for maintaining the reduced state are not required. Therefore, it is also possible to simplify the process required to restore the nitrided inner surface to the state before nitridation, and shorten the time required to restore the nitrided inner surface to the state before nitridation.

[0050] (5) In the process of etching a plurality of substrates S in one etching chamber 11 , since a decrease in the etching amount is suppressed, the usefulness of supplying hydrogen plasma and oxygen plasma to the inner surface of the discharge tube 24A is further improved.

[0051] It should be noted that the above-mentioned embodiment can be implemented by changing the above-mentioned embodiment as follows. [Etching chamber] In the etching chamber 11 , the first heating unit 11A may be omitted, and the second heating unit 11C may also be omitted.

[0052] The etching chamber 11 may be connected to an inert gas supply unit. The inert gas supply unit supplies an inert gas such as nitrogen gas or argon gas for heating the substrate S into the etching chamber 11 .

[0053] The etching chamber 11 may be changed to a single-wafer type in which one substrate S is etched in one etching operation. [gas] The fluorine-containing gas may be hydrogen fluoride gas, carbon tetrafluoride gas, or silicon tetrafluoride gas. The fluorine-containing gas is a gas that generates an etchant by reacting with plasma generated from the mixed gas in the silicon-containing film.

[0054] [Etching method] In the reforming process, part of the period during which the hydrogen-containing gas for generating hydrogen plasma is supplied to the discharge tube 24A may overlap part of the period during which the oxygen-containing gas for generating oxygen plasma is supplied to the discharge tube 24A.

[0055] When hydrogen plasma is supplied to the inner surface of the discharge tube 24A and when oxygen plasma is supplied to the inner surface of the discharge tube 24A, the etching target may be located in the etching chamber 11 . Description of Reference Numerals

[0056] 10… Etching device 10C…Control device 11…Etching chamber 12…Load lock chamber 21…Mixed gas supply unit 21A…Nitrogen-containing gas supply unit 21B…Hydrogen-containing gas supply unit 21C…Oxygen-containing gas supply unit 23…Fluorine-containing gas supply unit 24…Plasma supply unit 24A...Discharge tube 24B…waveguide 24C…Microwave source S…Substrate

Claims

1. An etching method, characterized in that: It includes: generating a reactive plasma containing hydrogen and nitrogen in a discharge tube having an inner surface formed of an inorganic oxide, and supplying the reactive plasma to a processing chamber connected to the discharge tube; generating a precursor containing fluorine and hydrogen in the processing chamber using a gas containing fluorine and the reactive plasma, and supplying the precursor to an etching object disposed in the processing chamber; supplying hydrogen plasma to the inner surface of the discharge tube where the reaction plasma is generated; and Oxygen plasma is supplied to the inner surface to which the hydrogen plasma is supplied.

2. The etching method according to claim 1, wherein: Whenever the discharge tube generates the reaction plasma a predetermined number of times, the supply of the hydrogen plasma and the supply of the oxygen plasma are performed only once.

3. The etching method according to claim 1, wherein: Before the discharge tube generates the reaction plasma a predetermined number of times, supplying the hydrogen plasma and supplying the oxygen plasma; After the discharge tube generates the reaction plasma the predetermined number of times, the supply of the hydrogen plasma and the supply of the oxygen plasma are performed.

4. The etching method according to claim 1, wherein: Supplying oxygen plasma to the inner surface of the discharge tube includes generating the oxygen plasma in the discharge tube from oxygen gas or water supplied to the discharge tube.

5. The etching method according to claim 1, wherein: Supplying hydrogen plasma to the inner surface of the discharge tube includes generating the hydrogen plasma in the discharge tube from hydrogen gas or ammonia gas supplied to the discharge tube.

6. The etching method according to any one of claims 1 to 5, wherein: The supplying of the hydrogen plasma to the inner surface of the discharge tube and the supplying of the oxygen plasma to the inner surface of the discharge tube are performed by simultaneously supplying a gas containing hydrogen and a gas containing oxygen into the discharge tube, and generating the hydrogen plasma and the oxygen plasma from the gas containing hydrogen and the gas containing oxygen in the discharge tube.

7. The etching method according to any one of claims 1 to 5, wherein: The etching objects are a plurality of silicon substrates each having a silicon oxide film. The processing chamber accommodates the plurality of silicon substrates adjacent to each other at intervals. The supplying of the precursor includes supplying the precursor from around the plurality of silicon substrates toward the space.

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