Etching method

Abstract

To provide an etching method capable of suppressing deterioration in characteristics contributing to generation of a precursor in plasma generated in a discharge tube.SOLUTION: An etching method includes the steps of: generating a hydrogen-nitrogen containing reactive plasma in a discharge tube 24A having an inner surface made of an inorganic oxide to supply the reactive 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 a gas containing fluorine and the reactive plasma to supply the precursor to a substrate arranged in the etching chamber 11. The etching method includes the steps of supplying a hydrogen plasma to the inner surface of the discharge tube 24A in which the reactive plasma has been generated, and supplying an oxygen plasma to the inner surface to which the hydrogen-containing plasma has been supplied in a state where no substrate is present in the etching chamber 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an etching method.

Background Art

[0002] An example of an etching apparatus for removing a native oxide film from a silicon substrate generates an etchant for the native oxide film by radicals in plasma generated by microwave irradiation. When generating the etchant, a gas for plasma generation is supplied to a discharge tube having an inner surface composed of an inorganic oxide. Then, by irradiating the discharge tube with microwaves, plasma is generated in the discharge tube. The etching apparatus vaporizes a complex generated from the etchant and the native oxide film by heating the silicon substrate (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, for the generation of plasma for generating an etchant, a nitrogen-containing gas such as ammonia gas is used. Generating plasma from a nitrogen-containing gas in a discharge tube composed of an inorganic oxide such as sapphire or quartz nitrides the inner surface of the discharge tube. As a result, in the plasma generated in the discharge tube whose inner surface is nitrided, the characteristics contributing to the generation of precursors are deteriorated as compared with those before nitridation.

Means for Solving the Problems

[0005] The etching method for solving the above problems 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 to which the discharge tube is connected, 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 object to be etched disposed in the processing chamber. The etching method includes supplying a hydrogen plasma to the inner surface of the discharge tube that has generated the reactive plasma, and supplying an oxygen plasma to the inner surface supplied with the hydrogen plasma.

[0006] According to the above etching method, the inner surface of the discharge tube nitrided by the generation of the reactive plasma is reduced by the modification of the hydrogen plasma. The inner surface reduced by the hydrogen plasma is oxidized by the oxygen plasma. Then, the inner surface composed of the inorganic oxide returns to the state before being nitrided. As a result, the characteristics of the reactive plasma are stabilized by the amount by which the properties of the inner surface in the discharge tube are stabilized. For this reason, the decrease in the etching amount is suppressed by the amount by which the characteristics of the reactive plasma are stabilized.

[0007] In the above etching method, each time the discharge tube generates the reactive plasma a predetermined number of times, the supply of the hydrogen plasma and the supply of the oxygen plasma may be performed only once.

[0008] According to the above etching method, since the inner surface modification of the discharge tube by reduction and oxidation is performed each time the reactive plasma is generated a predetermined number of times, the characteristics of the reactive plasma are further stabilized.

[0009] In the above etching method, the supply of the hydrogen plasma and the supply of the oxygen plasma may be performed before and after the discharge tube generates the reactive plasma a predetermined number of times. According to the above etching method, since the inner surface modification of the discharge tube by reduction and oxidation is performed before and after the reactive plasma is generated a predetermined number of times, the characteristics of the reactive plasma are further stabilized.

[0010] In the above etching method, supplying oxygen plasma to the inner surface of the discharge tube may be to generate the oxygen plasma in the discharge tube from the oxygen gas or water supplied to the discharge tube.

[0011] In the above etching method, supplying hydrogen plasma to the inner surface of the discharge tube may be to generate the hydrogen plasma in the discharge tube from the hydrogen gas or ammonia gas supplied to the discharge tube. According to each of the above etching methods, the effectiveness of suppressing a decrease in the etching amount is enhanced.

[0012] In the above etching method, supplying the hydrogen plasma and supplying the oxygen plasma to the inner surface of the discharge tube may be to simultaneously supply a gas containing hydrogen and a gas containing oxygen into the discharge tube, and generate the hydrogen plasma and the oxygen plasma in the discharge tube from the gas containing hydrogen and the gas containing oxygen.

[0013] According to the above etching method, the hydrogen plasma and the oxygen plasma are supplied to the inner surface of the discharge tube almost simultaneously. Then, the inner surface reduced by the hydrogen plasma is oxidized without requiring an environment, time, etc. for maintaining the reduced state. For this reason, it is also possible to simplify the steps required to return the nitrided inner surface to the state before nitridation, and shorten the time required to return the nitrided inner surface to the state before nitridation.

[0014] In the above etching method, the object to be etched is a silicon substrate provided with a silicon oxide film, the processing chamber accommodates a plurality of the silicon substrates such that the adjacent silicon substrates are stacked with a space therebetween, and supplying the precursor may be to supply the precursor from around the silicon substrate toward the space.

[0015] The process of simultaneously etching a plurality of silicon substrates in one processing chamber is such that a decrease in the etching amount per process affects the processing results of all silicon substrates. Therefore, compared with the process of etching a plurality of silicon substrates one by one, the process of simultaneously etching a plurality of silicon substrates in one processing chamber is more strongly required to suppress fluctuations in the etching amount between processes. According to the above etching method, in the process of etching a plurality of silicon substrates in one processing chamber, 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 is further enhanced.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0017] With reference to FIGS. 1 to 5, an embodiment of the etching method will be described. [Etching Apparatus] As shown in FIG. 1, 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.

[0018] The etching chamber 11 demarcates a space for accommodating a substrate S (see FIG. 2), which is an example of an object to be etched. The etching chamber 11 etches a silicon oxide film within the space for accommodating the substrate S. The load lock chamber 12 carries the substrate S before etching into the etching chamber 11 from the outside. The load lock chamber 12 carries the substrate S after etching out of the etching chamber 11 to the outside.

[0019] The gate valve 13 is disposed between the etching chamber 11 and the load lock chamber 12. When the gate valve 13 opens, the etching chamber 11 communicates with the load lock chamber 12. When the gate valve 13 closes, the etching chamber 11 is blocked from the load lock chamber 12.

[0020] The load lock chamber 12 is connected to a cooling gas supply unit 12A. The cooling gas supply unit 12A supplies a cooling gas to the load lock chamber 12. The cooling gas is an inert gas for cooling the substrate S after etching.

[0021] 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 reduces the pressure of 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.

[0022] 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 the space for accommodating the substrate S within the etching chamber 11. An example of the fluorine-containing gas is nitrogen trifluoride gas. The plasma supply unit 24 supplies reactive plasma to the space for accommodating the substrate S within the etching chamber 11.

[0023] The plasma supply unit 24 includes a discharge tube 24A, a waveguide 24B, and a microwave source 24C. The microwave source 24C irradiates the discharge tube 24A with microwaves 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 made of an inorganic oxide. The inorganic oxide constituting the inner surface of the discharge tube 24A may be a silicon oxide or an aluminum oxide. The discharge tube 24A may be, for example, a quartz tube.

[0024] The mixed gas supply unit 21 supplies a first mixed gas containing hydrogen atoms and nitrogen atoms to the discharge tube 24A. Further, 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.

[0025] 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 the nitrogen-containing gas is nitrogen gas. An example of the hydrogen-containing gas is ammonia gas. The hydrogen-containing gas may be hydrogen gas. An example of the oxygen-containing gas is oxygen gas. The oxygen-containing gas may be a gas of an oxygen compound. The oxygen compound may be, for example, water or a nitrogen oxygen compound.

[0026] The plasma supply unit 24 generates reactive plasma in the discharge tube 24A by irradiating the first mixed gas in the discharge tube 24A with microwaves. The reactive plasma contains hydrogen radicals, nitrogen radicals, and hydrogen nitride radicals. In the etching chamber 11, a precursor containing fluorine atoms and hydrogen atoms is generated by the reactive plasma and the fluorine-containing gas, and the precursor is thereby supplied to the substrate S.

[0027] The plasma supply unit 24 generates hydrogen plasma in the discharge tube 24A by irradiating a hydrogen-containing gas with microwaves in the discharge tube 24A. The hydrogen plasma contains hydrogen atoms or hydrogen molecules that have been plasmaized and have the function of cleaving the bond between inorganic atoms and nitrogen atoms in an inorganic nitride in which an inorganic oxide has been nitrided by the plasmaized hydrogen atoms. The hydrogen plasma is plasma generated from hydrogen gas and may be composed of plasmaized hydrogen atoms or may contain plasmaized hydrogen molecules. The hydrogen plasma is plasma generated from ammonia gas and may contain plasmaized hydrogen atoms and plasmaized hydrogen nitride.

[0028] The plasma supply unit 24 generates oxygen plasma in the discharge tube 24A by irradiating an oxygen-containing gas with microwaves in the discharge tube 24A. The oxygen plasma contains plasmaized oxygen atoms, plasmaized oxygen molecules, ozone, or plasmaized oxygen compounds that have the function of oxidizing an inorganic nitride reduced by plasmaized hydrogen atoms back to an inorganic oxide. The oxygen compound may be water or a nitrogen-oxygen compound. The oxygen plasma is plasma generated from oxygen gas and may be composed of plasmaized oxygen atoms, may contain plasmaized oxygen molecules, or may contain ozone. The oxygen plasma is plasma generated from an oxygen compound and may contain plasmaized oxygen atoms and plasmaized oxygen compounds.

[0029] The plasma supply unit 24 generates reformed plasma in the discharge tube 24A by irradiating a second mixed gas with microwaves in the discharge tube 24A. The reformed plasma contains hydrogen plasma and oxygen plasma.

[0030] The modified plasma may be generated in the discharge tube 24A from a gas obtained by adding a trace amount of oxygen to a first mixed gas for generating a reactive plasma containing hydrogen and nitrogen. When the first mixed gas is a mixed gas of ammonia gas and nitrogen gas, the modified plasma may be generated from a mixed gas obtained by adding a trace amount of oxygen gas to the first mixed gas. As a result, the environment for etching the substrate S and the environment for modifying the inner surface of the discharge tube 24A become close inside the etching chamber 11, so that it becomes easier to stabilize the state of the plasma in etching compared to the case where these environments are greatly different. The flow rate of the trace amount of oxygen gas may be 0.5% or more and 10% or less, or 1% or more and 10% or less with respect to the flow rate of the gas for generating hydrogen plasma. The trace amount of oxygen gas may be 0.5% or more and 10% or less, or 1% or more and 10% or less with respect to the flow rate of the ammonia gas for generating hydrogen plasma.

[0031] The control device 10C includes a storage unit 10CM. The storage unit 10CM stores the 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 so that the etching conditions match the process conditions.

[0032] [Etching Chamber 11] As shown in FIG. 2, the etching chamber 11 houses 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 a gap between adjacent substrates S. The substrate S includes a silicon oxide film. An example of the substrate S is a silicon substrate having a disk shape.

[0033] The etching chamber 11 is provided with 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 two or more. Note that FIG. 2 shows an example in which two discharge tubes 24A are connected to the shower head 11D. The shower head 11D is provided with 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 tube 24A toward the substrate S.

[0034] The etching chamber 11 is provided with a rotating unit 11E. The rotating unit 11E rotates the support unit 10A in the circumferential direction of the substrate S. The rotating unit 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 unit 23 toward the substrate S in the circumferential direction of the substrate S. Thereby, in the etching chamber 11, the precursor is supplied from around the substrate S toward the interval between the adjacent substrates S.

[0035] The etching chamber 11 is provided with a temperature measurement unit 11F. The temperature measurement unit 11F measures the temperature inside the etching chamber 11 as the temperature of the substrate S. The temperature measurement unit 11F is connected to the control device 10C. The temperature measurement result by the temperature measurement 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 by the temperature measurement unit 11F.

[0036] [Etching method] The etching method includes supplying reactive plasma to a processing chamber, supplying a precursor to an object to be etched, supplying hydrogen plasma, and supplying oxygen plasma. By 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 the processing chamber to which the discharge tube is connected. By supplying the precursor, a precursor containing fluorine and hydrogen is generated in the processing chamber using a gas containing fluorine and the reactive plasma, and the precursor is supplied to the object to be etched disposed in the processing chamber. By supplying the hydrogen plasma, the hydrogen plasma is supplied to the inner surface of the discharge tube that generated the reactive plasma in a state where the object to be etched does not exist in the processing chamber. By supplying the oxygen plasma, the oxygen plasma is supplied to the inner surface of the discharge tube supplied with the hydrogen plasma.

[0037] According to the etching method of the present disclosure, the inner surface of the discharge tube nitrided by the generation of the reactive plasma is reduced by the reforming of the hydrogen plasma. The inner surface reduced by the hydrogen plasma is oxidized by the oxygen plasma. Then, the inner surface composed of the inorganic oxide returns to the state before being nitrided. As a result, the characteristics of the reactive plasma are stabilized by the amount by which the properties of the inner surface in the discharge tube are stabilized. Therefore, the decrease in the etching amount is suppressed by the amount by which the characteristics of the reactive plasma are stabilized. Hereinafter, the etching method will be described in more detail with reference to the drawings.

[0038] As shown in FIG. 3, the etching method includes a hydrogen plasma supply step (step S11) and an oxygen plasma supply step (step S12). In the hydrogen plasma supply step, hydrogen plasma is supplied to the inner surface of the discharge tube 24A. In the oxygen plasma supply step, oxygen plasma is supplied to the inner surface of the discharge tube 24A supplied with the hydrogen plasma.

[0039] The hydrogen plasma supply step and the oxygen plasma supply step may be performed individually. That is, after the supply of the hydrogen plasma to the inner surface of the discharge tube 24A is completed, the supply of the oxygen plasma to the inner surface of the discharge tube 24A may be started.

[0040] Alternatively, the hydrogen plasma supply step and the oxygen plasma supply step may be performed simultaneously. That is, in the discharge tube 24A, a hydrogen-containing gas and an oxygen-containing gas may be supplied simultaneously, and then, hydrogen plasma and oxygen plasma may be generated in the discharge tube 24A from 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. And the inner surface reduced by the hydrogen plasma is oxidized without requiring an environment, time, etc. for maintaining the reduced state. For this reason, it is possible to simplify the process required to return the nitrided inner surface to the state before nitriding, and to shorten the time required to return the nitrided inner surface to the state before nitriding.

[0041] In the hydrogen plasma supply step, hydrogen plasma may be generated in the discharge tube 24A from the hydrogen gas or ammonia gas supplied to the discharge tube 24A. Also, in the oxygen plasma supply step, oxygen plasma may be generated in the discharge tube 24A from the oxygen gas or water supplied to the discharge tube 24A. In these cases, the effectiveness of suppressing a decrease in the etching amount is enhanced.

[0042] The etching method includes a reaction plasma supply step (step S13) and a precursor supply step (step S14) after the hydrogen plasma supply step and the oxygen plasma supply step. In the reaction plasma supply step, the reaction plasma generated in the discharge tube 24A is supplied into the etching chamber 11. In the precursor supply step, the reaction plasma is supplied into the etching chamber 11, and a fluorine-containing gas is supplied into the etching chamber 11, whereby a precursor is generated in the etching chamber 11. And the generated precursor is supplied to the substrate S accommodated in the etching chamber 11. Thereby, a reaction product more volatile than the silicon oxide film is generated on the substrate S by the reaction between the silicon oxide film on the substrate S and the precursor.

[0043] In the precursor supply step, as described above, the precursor is supplied from around the substrate S provided with the silicon oxide film toward the interval between adjacent substrates S. In the process of etching a plurality of substrates S simultaneously in one etching chamber 11, a decrease in the etching amount due to one process affects the processing results of all the substrates S. For this reason, in the process of etching a plurality of substrates S simultaneously in one etching chamber 11, it is more strongly required to suppress fluctuations in the etching amount between processes compared to the process of etching the plurality of substrates S one by one. In this regard, in the etching method of the present embodiment, in the process of etching a plurality of substrates S in one etching chamber 11, a decrease in the etching amount is suppressed. Therefore, the usefulness of supplying hydrogen plasma and oxygen plasma to the inner surface of the discharge tube 24A is further enhanced.

[0044] The reactive plasma supply step and the precursor supply step are performed a predetermined number of times. The number of times the reactive plasma supply step and the precursor supply step are performed may be once or two or more times. When the reactive plasma supply step and the precursor supply step are performed a predetermined number of times (step S15: YES), the hydrogen plasma supply step (step S16) is performed, and subsequently the oxygen plasma supply step (step S17) is performed.

[0045] In the hydrogen plasma supply step, hydrogen plasma is supplied to the inner surface of the discharge tube 24A in the same manner as the hydrogen plasma supply step in step S12 described above. In the oxygen plasma supply step, oxygen plasma is supplied to the inner surface of the discharge tube 24A to which hydrogen plasma has been supplied in the same manner as the oxygen plasma supply step described above.

[0046] The hydrogen plasma supply step and the oxygen plasma supply step may be performed individually. 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 step and the oxygen plasma supply step may be performed simultaneously.

[0047] In this way, in the etching method, every time the discharge tube 24A generates the reactive plasma a predetermined number of times, the supply of hydrogen plasma and the supply of oxygen plasma are each performed only once. As a result, the inner surface modification of the discharge tube 24A by reduction and oxidation is carried out every time the reactive plasma is generated a predetermined number of times, so that the characteristics of the reactive plasma become more stable.

[0048] Also, in the etching method, before and after the discharge tube 24A generates the reactive plasma a predetermined number of times, the supply of hydrogen plasma and the supply of oxygen plasma are performed. This also makes the characteristics of the reactive plasma more stable.

[0049] Note that the hydrogen plasma supply step (step S111) and the oxygen plasma supply step (step S12) performed before the reactive plasma supply step may be omitted. When the processes of steps S11 and S12 are performed, regardless of the period from the completion of the process of step S17 to the performance of the process of step S13, it is possible to keep the environment in the etching chamber 11 substantially constant when step S13 is performed. Therefore, variations in the etching amount of the silicon oxide film can be further suppressed.

[0050] [Example] [Example 1] An etching apparatus 10 in which two quartz tubes, which are an example of the discharge tube 24A, are connected to the etching chamber 11 was prepared. A mixed gas supply unit 21 was connected to each discharge tube 24A. Every time the substrate S was etched once in the etching apparatus 10, that is, when n in FIG. 3 was set to 1, the modification process of the discharge tube 24A was performed. When performing the modification process of the discharge tube 24A, a hydrogen-containing gas and an oxygen-containing gas were simultaneously supplied, and then a modification plasma was generated from 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 were set as follows.

[0051] [Modification Process Conditions] Ammonia gas (hydrogen-containing gas): 1300 sccm Oxygen gas (oxygen-containing gas): 9 sccm Nitrogen gas: 3900 sccm

[0052] [Comparative Example 1] When etching the silicon oxide film using the same etching apparatus 10 as in Example 1, the substrate S was etched in the same manner as in Example 1, except that the modification treatment of the discharge tube 24A was not performed.

[0053] [Evaluation 1] As a result of measuring the change over time in the etching amount, it was as shown in FIG. 4. In FIG. 4, the etching amount of Example 1 is indicated by black circles, and the etching amount of Comparative Example 1 is indicated by white circles.

[0054] As shown in FIG. 4, in Example 1 where the modification treatment of the discharge tube 24A was performed, it was confirmed that the etching amount per treatment was more stable than in Comparative Example 1 where the modification treatment of the discharge tube 24A was not performed.

[0055] [Evaluation 2] In the etching apparatus 10 used in Example 1, the etching amount of the substrate S at each slot number in the support portion 10A was measured. At this time, the etching amount at the initial stage of etching, the etching amount before the modification treatment after performing etching a plurality of times, and the etching amount after the modification treatment after performing etching a plurality of times were measured. In FIG. 5, the etching amount at the initial stage of etching is indicated by white circles, the etching amount before the modification treatment is indicated by black-filled triangles, and the etching amount after the modification treatment is indicated by black-filled squares.

[0056] As shown in FIG. 5, in a plurality of stacked substrates, at positions where the decrease in the etching amount is large, the etching amount greatly recovers after the modification treatment, while at positions where the decrease in the etching amount is small, it was confirmed that the recovery of the etching amount after the modification treatment is also small. Also, by performing the modification treatment, it was confirmed that the etching amount of the substrate S at all slot numbers was included within a predetermined range.

[0057] 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 nitrided by the generation of reactive plasma is reduced by the reforming of hydrogen plasma. The inner surface reduced by hydrogen plasma is oxidized by oxygen plasma. Then, the inner surface composed of inorganic oxide returns to the state before nitriding. As a result, the characteristics of the reactive plasma are stabilized by the amount corresponding to the stabilization of the properties of the inner surface in the discharge tube 24A. Therefore, the decrease in the etching amount is suppressed by the amount corresponding to the stabilization of the characteristics of the reactive plasma.

[0058] (2) Since the inner surface modification of the discharge tube 24A by reduction and oxidation is performed every time reactive plasma is generated a predetermined number of times, the characteristics of the reactive plasma are further stabilized. (3) Since the inner surface modification of the discharge tube by reduction and oxidation is performed before and after reactive plasma is generated a predetermined number of times, the characteristics of the reactive plasma are further stabilized.

[0059] (4) When generating plasma from a mixed gas containing a hydrogen-containing gas and an oxygen-containing gas, hydrogen plasma and oxygen plasma are supplied to the inner surface of the discharge tube 24A almost simultaneously. Then, the inner surface reduced by hydrogen plasma is oxidized without requiring an environment, time, etc. for maintaining the reduced state. Therefore, it is also possible to simplify the process required to return the nitrided inner surface to the state before nitriding and shorten the time required to return the nitrided inner surface to the state before nitriding.

[0060] (5) In the process of etching a plurality of substrates S in one etching chamber 11, since the 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 enhanced.

[0061] Note that the above-described embodiment can be implemented with the following modifications. [Etching Chamber] · The etching chamber 11 may omit the first heating unit 11A or may omit the second heating unit 11C.

[0062] · 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 to the etching chamber 11.

[0063] · The etching chamber 11 may be changed to a mode of etching one substrate S by one etching. [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 the plasma generated from the mixed gas and the silicon-containing film.

[0064] [Etching Method] · In the reforming process, a part of the period in which the hydrogen-containing gas for generating hydrogen plasma is supplied to the discharge tube 24A may overlap with a part of the period in which the oxygen-containing gas for generating oxygen plasma is supplied to the discharge tube 24A.

[0065] · When supplying hydrogen plasma to the inner surface of the discharge tube 24A and when supplying oxygen plasma to the inner surface of the discharge tube 24A, the object to be etched may be located in the etching chamber 11.

Explanation of Reference Numerals

[0066] 10…Etching apparatus 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. Generating a reactive plasma containing hydrogen and nitrogen in a discharge tube having an inner surface composed of an inorganic oxide, and supplying the reactive plasma to a processing chamber to which the discharge tube is connected; 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 object to be etched disposed in the processing chamber; An etching method comprising: Supplying a hydrogen plasma to the inner surface of the discharge tube that generated the reactive plasma, and supplying an oxygen plasma to the inner surface supplied with the hydrogen plasma; An etching method characterized by the above.

2. Each time the discharge tube generates the reactive plasma a predetermined number of times, the supply of the hydrogen plasma and the supply of the oxygen plasma are each performed only once; The etching method according to Claim 1.

3. Before and after the discharge tube generates the reactive plasma a predetermined number of times, the supply of the hydrogen plasma and the supply of the oxygen plasma are performed; The etching method according to Claim 1.

4. Supplying the oxygen plasma to the inner surface of the discharge tube is generating the oxygen plasma in the discharge tube from the oxygen gas supplied to the discharge tube or water; The etching method according to Claim 1.

5. Supplying the hydrogen plasma to the inner surface of the discharge tube is generating the hydrogen plasma in the discharge tube from the hydrogen gas supplied to the discharge tube or ammonia gas; The etching method according to Claim 1.

6. Supplying the hydrogen plasma to the inner surface of the discharge tube and supplying the oxygen plasma is simultaneously supplying a gas containing hydrogen and a gas containing oxygen into the discharge tube, and generating the hydrogen plasma and the oxygen plasma in the discharge tube from the gas containing hydrogen and the gas containing oxygen; The etching method according to any one of Claims 1 to 5.

7. The object to be etched is a silicon substrate provided with a silicon oxide film; The processing chamber accommodates a plurality of the silicon substrates such that the adjacent silicon substrates are stacked with a space therebetween; Supplying the precursor is supplying the precursor from around the silicon substrate toward the space; The etching method according to any one of Claims 1 to 5.

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