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 technology]

[0002] One example of an etching apparatus for removing native oxide films from silicon substrates produces an etchant for the native oxide film by radicals in plasma generated by microwave irradiation. When producing the etchant, a gas for plasma production is supplied to a discharge tube having an inner surface made of an inorganic oxide. Next, the discharge tube is irradiated with microwaves to produce plasma within the discharge tube. The etching apparatus vaporizes a complex produced 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] JP 2011-096937 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, a nitrogen-containing gas such as ammonia gas is used to generate plasma for generating an etchant. Generating plasma from a nitrogen-containing gas in a discharge tube made of an inorganic oxide such as sapphire or quartz nitrides the inner surface of the discharge tube. As a result, the plasma generated in the discharge tube with the nitrided inner surface has a reduced ability to contribute to the generation of precursors compared to before nitridation. [Means for solving the problem]

[0005] An etching method for solving the above problems includes generating a reactive plasma containing hydrogen and nitrogen in a discharge tube having an inner surface made of an inorganic oxide, 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 target placed in the processing chamber. The etching method includes supplying hydrogen plasma to the inner surface of the discharge tube where the reactive plasma is generated, and supplying oxygen plasma to the inner surface to which the hydrogen plasma has been supplied.

[0006] According to the above etching method, the inner surface of the discharge tube, which has been nitrided by the generation of reactive plasma, is reduced by modification with hydrogen plasma. The inner surface reduced by hydrogen plasma is oxidized by oxygen plasma. The inner surface made of inorganic oxide returns to the state before nitridation. As a result, the characteristics of the reactive plasma are stabilized to the extent that the properties of the inner surface of the discharge tube are stabilized. Therefore, the decrease in the amount of etching is suppressed to the extent that the characteristics of the reactive plasma are stabilized.

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

[0008] According to the above etching method, the modification of the inner surface of the discharge tube by reduction and oxidation is carried out every time a reactive plasma is generated a predetermined number of times, so that the characteristics of the reactive plasma become more stable.

[0009] In the above etching method, the hydrogen plasma and the oxygen plasma may be supplied before and after the discharge tube generates the reactive plasma a predetermined number of times. According to the above etching method, the modification of the inner surface of the discharge tube by reduction and oxidation is carried out a predetermined number of times before and after the generation of the reactive plasma, so that the characteristics of the reactive plasma become more stable.

[0010] In the above etching method, supplying oxygen plasma to the inner surface of the discharge tube may comprise generating the oxygen plasma within the discharge tube from 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 comprise generating the hydrogen plasma within the discharge tube from hydrogen gas or ammonia gas supplied to the discharge tube. According to each of the above etching methods, the effectiveness of suppressing the decrease in the amount of etching is increased.

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

[0013] According to the above etching method, hydrogen plasma and oxygen plasma are supplied to the inner surface of the discharge tube almost simultaneously. The inner surface reduced by hydrogen plasma is then oxidized without requiring an environment or time to maintain the reduced state. This makes it possible to simplify the process required to return the nitrided inner surface to its pre-nitrided state and to shorten the time required to return the nitrided inner surface to its pre-nitrided state.

[0014] In the above etching method, the etching target may be a silicon substrate having a silicon oxide film, the processing chamber may accommodate a plurality of the silicon substrates stacked with a gap between adjacent silicon substrates, and supplying the precursor may include supplying the precursor from a periphery of the silicon substrate toward the gap.

[0015] In a process in which multiple silicon substrates are etched simultaneously in one processing chamber, a decrease in the amount of etching due to one processing step affects the processing results of all the silicon substrates. Therefore, in a process in which multiple silicon substrates are etched simultaneously in one processing chamber, it is more strongly required to suppress the variation in the amount of etching between processing steps than in a process in which multiple silicon substrates are etched one by one. According to the above etching method, the decrease in the amount of etching is suppressed in a process in which multiple silicon substrates are etched in one processing chamber, and therefore 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] FIG. 1 is a diagram showing the configuration of an etching apparatus. [Diagram 2] FIG. 2 is a diagram showing the structure of an etching chamber included in the etching apparatus shown in FIG. [Diagram 3] FIG. 3 is a flowchart illustrating the procedure of the etching method. [Figure 4] FIG. 4 is a graph showing the relationship between the elapsed time and the amount of etching in Example 1 and Comparative Example 1. [Diagram 5] FIG. 5 is a graph showing the relationship between the slot number and the etching amount in Evaluation 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] One embodiment of an etching method will be described with reference to Figures 1 to 5. [Etching equipment] 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 defines a space for accommodating a substrate S (see FIG. 2), which is an example of an etching target. The etching chamber 11 etches a silicon oxide film in the space accommodating 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.

[0019] 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 communicates with the load lock chamber 12. When the gate valve 13 is closed, the etching chamber 11 is isolated 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 in 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 a space in the etching chamber 11 that accommodates the substrate S. An example of the fluorine-containing gas is nitrogen trifluoride gas. The plasma supply unit 24 supplies a reactive plasma to the space in the etching chamber 11 that accommodates the substrate S.

[0023] 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 made 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.

[0024] The mixed gas supply unit 21 supplies a first mixed gas containing hydrogen atoms and nitrogen atoms to the discharge tube 24A. Also, 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 an oxygen compound gas. 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 with microwaves in the discharge tube 24A. 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 supplied to the substrate S.

[0027] 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 a function of breaking bonds between inorganic atoms and nitrogen atoms in an inorganic nitride obtained by nitriding an inorganic oxide with the plasmatized hydrogen atoms. The hydrogen plasma is plasma generated from hydrogen gas and may be composed of plasmatized hydrogen atoms or may contain plasmatized hydrogen molecules. The hydrogen plasma is plasma generated from ammonia gas and may contain plasmatized hydrogen atoms and plasmatized hydrogen nitride.

[0028] The plasma supply unit 24 generates oxygen plasma in the discharge tube 24A by irradiating microwaves to an oxygen-containing gas in the discharge tube 24A. The oxygen plasma includes plasmatized oxygen atoms, plasmatized oxygen molecules, ozone, or plasmatized oxygen compounds, which have the function of oxidizing inorganic nitrides reduced by plasmatized hydrogen atoms back to inorganic oxides. The oxygen compounds may be water or nitrogen-oxygen compounds. The oxygen plasma is a plasma generated from oxygen gas, and may be composed of plasmatized oxygen atoms, may include plasmatized oxygen molecules, or may include ozone. The oxygen plasma is a plasma generated from an oxygen compound, and may include plasmatized oxygen atoms and plasmatized oxygen compounds.

[0029] The plasma supply unit 24 irradiates microwaves to the second mixed gas in the discharge tube 24A to generate a modifying plasma in the discharge tube 24A. The modifying plasma includes hydrogen plasma and oxygen plasma.

[0030] The modified plasma may be generated in the discharge tube 24A from a gas obtained by adding a small 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 small amount of oxygen gas to the first mixed gas. This makes the environment for etching the substrate S and the environment for modifying the inner surface of the discharge tube 24A similar inside the etching chamber 11, so that it is easier to stabilize the state of plasma during etching compared to when these environments are significantly different. The flow rate of the small amount of oxygen gas may be 0.5% to 10% or 1% to 10% of the flow rate of the gas for generating hydrogen plasma. The flow rate of the small amount of oxygen gas may be 0.5% to 10% or 1% to 10% of the flow rate of the ammonia gas for generating hydrogen plasma.

[0031] The control device 10C includes a memory unit 10CM. The memory unit 10CM stores process conditions for etching a silicon oxide film. The process conditions include the pressure in 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 contains a support 10A. The support 10A is capable of supporting a plurality of substrates S. The plurality of substrates S supported by the support 10A are stacked with a gap between adjacent substrates S. The substrates S include a silicon oxide film. One example of the substrate S is a silicon substrate having a disk shape.

[0033] 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. Note that FIG. 2 shows an example in which two discharge tubes 24A are connected to the shower head 11D. The shower head 11D includes a plurality of supply ports. The supply ports of the shower head 11D are aligned along the stacking direction of the substrates S. The supply ports of the shower head 11D supply plasma supplied from the discharge tube 24A toward the substrates S.

[0034] The etching chamber 11 includes 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. As a result, in the etching chamber 11, a precursor is supplied from the periphery of the substrate S toward the gap between the adjacent substrates S.

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

[0036] [Etching method] The etching method includes supplying reactive plasma to a processing chamber, supplying a precursor to an etching target, supplying hydrogen plasma, and supplying oxygen plasma. In supplying reactive plasma, reactive plasma containing hydrogen and nitrogen is generated in a discharge tube having an inner surface made of an inorganic oxide, and the reactive plasma is supplied to a processing chamber connected to the discharge tube. In supplying precursor, a precursor containing fluorine and hydrogen is generated in the processing chamber using a fluorine-containing gas and reactive plasma, and the precursor is supplied to an etching target disposed in the processing chamber. In supplying hydrogen plasma, hydrogen plasma is supplied to the inner surface of the discharge tube that generated the reactive plasma, without the etching target being present in the processing chamber. In supplying oxygen plasma, oxygen plasma is supplied to the inner surface of the discharge tube to which the hydrogen plasma has been supplied.

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

[0038] 3, the etching method includes a hydrogen plasma supplying step (step S11) and an oxygen plasma supplying step (step S12). In the hydrogen plasma supplying step, hydrogen plasma is supplied to the inner surface of the discharge tube 24A. In the oxygen plasma supplying step, oxygen plasma is supplied to the inner surface of the discharge tube 24A to which the hydrogen plasma has been supplied.

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

[0040] Alternatively, the hydrogen plasma supply step and the oxygen plasma supply step may be performed simultaneously. That is, a hydrogen-containing gas and an oxygen-containing gas may be simultaneously supplied into the discharge tube 24A, and then hydrogen plasma and oxygen plasma may be generated from the hydrogen-containing gas and the oxygen-containing gas in the discharge tube 24A. In this case, the hydrogen plasma and the oxygen plasma are supplied to the inner surface of the discharge tube 24A almost simultaneously. Then, the inner surface reduced by the hydrogen plasma is oxidized without requiring an environment or time to maintain the reduced state. This makes it possible to simplify the steps required to return the nitrided inner surface to its pre-nitrided state, and to shorten the time required to return the nitrided inner surface to its pre-nitrided state.

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

[0042] The etching method includes a hydrogen plasma supply step and an oxygen plasma supply step, followed by a reactive plasma supply step (step S13) and a precursor supply step (step S14). In the reactive plasma supply step, reactive plasma generated in the discharge tube 24A is supplied into the etching chamber 11. In the precursor supply step, reactive plasma is supplied into the etching chamber 11, and a fluorine-containing gas is supplied into the etching chamber 11, thereby generating a precursor in the etching chamber 11. The generated precursor is then supplied to the substrate S accommodated in the etching chamber 11. As a result, a reaction product that is more volatile than the silicon oxide film is generated on the substrate S by a reaction between the silicon oxide film of the substrate S and the precursor.

[0043] In the precursor supply step, as described above, the precursor is supplied from the periphery of the substrate S having the silicon oxide film toward the gap between the adjacent substrates S. In the process of simultaneously etching a plurality of substrates S in one etching chamber 11, a decrease in the amount of etching due to one process affects the processing results of all the substrates S. Therefore, in the process of simultaneously etching a plurality of substrates S in one etching chamber 11, it is more strongly required to suppress the variation in the amount of etching between processes than in the process of etching a plurality of substrates S one by one. In this respect, in the etching method of this embodiment, a decrease in the amount of etching is 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 increased.

[0044] The reactive plasma supply step and the precursor supply step are performed a predetermined number of times. The reactive plasma supply step and the precursor supply step may be performed once or twice or more. 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, followed by the oxygen plasma supply step (step S17).

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

[0046] The hydrogen plasma supply process and the oxygen plasma supply process may be carried out separately. That is, the supply of oxygen plasma to the inner surface of the discharge tube 24A may be started after the supply of hydrogen plasma to the inner surface of the discharge tube 24A is finished. Alternatively, the hydrogen plasma supply process and the oxygen plasma supply process may be carried out simultaneously.

[0047] In this way, in the etching method, hydrogen plasma and oxygen plasma are supplied only once each time the discharge tube 24A generates reactive plasma a predetermined number of times. This allows the inner surface of the discharge tube 24A to be modified by reduction and oxidation each time reactive plasma is generated a predetermined number of times, further stabilizing the characteristics of the reactive plasma.

[0048] In addition, in the etching method, hydrogen plasma and oxygen plasma are supplied before and after the discharge tube 24A generates reactive plasma a predetermined number of times, which also further stabilizes the characteristics of the reactive plasma.

[0049] 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 steps S11 and S12 are performed, the environment in the etching chamber 11 can be kept substantially constant when step S13 is performed, regardless of the period from the completion of step S17 to the start of step S13. This makes it possible to further reduce variations in the amount of etching of the silicon oxide film.

[0050] [Example] [Example 1] An etching apparatus 10 was prepared in which two quartz tubes, which are an example of the discharge tubes 24A, were connected to an etching chamber 11. A mixed gas supply unit 21 was connected to each discharge tube 24A. In the etching apparatus 10, every time the substrate S was etched once, that is, n in FIG. 3 was set to 1, a modification process was performed on the discharge tube 24A. When performing the modification process on 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 treatment conditions] Ammonia gas (hydrogen-containing gas): 1300sccm Oxygen gas (oxygen-containing gas): 9sccm Nitrogen gas: 3900sccm

[0052] [Comparative Example 1] When etching a 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] [Rating 1] The results of measuring the change over time in the amount of etching are shown in Figure 4. In Figure 4, the amount of etching in Example 1 is shown by a black circle, and the amount of etching in Comparative Example 1 is shown by a white circle.

[0054] As shown in FIG. 4, in Example 1 in which the modification treatment of the discharge tubes 24A was performed, the amount of etching for each treatment was found to be more stable than in Comparative Example 1 in which the modification treatment of the discharge tubes 24A was not performed.

[0055] [Rating 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. In this case, the etching amount at the beginning of the etching, the etching amount before the modification treatment after performing etching multiple times, and the etching amount after the modification treatment after performing etching multiple times were measured. In FIG. 5, the etching amount at the beginning of the etching is indicated by a white circle, the etching amount before the modification treatment is indicated by a black triangle, and the etching amount after the modification treatment is indicated by a black square.

[0056] As shown in Fig. 5, it was found that in the stacked substrates, the etching amount recovered significantly after the modification process at the positions where the etching amount was significantly decreased, while the etching amount recovered less at the positions where the etching amount was slightly decreased. It was also found that the etching amount of the substrates S of all slot numbers was within a predetermined range by performing the modification process.

[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, which has been nitrided by the generation of reactive plasma, is reduced by modification with hydrogen plasma. The inner surface reduced by hydrogen plasma is oxidized by oxygen plasma. The inner surface made of inorganic oxide returns to the state before nitridation. As a result, the characteristics of the reactive plasma are stabilized to the extent that the properties of the inner surface of the discharge tube 24A are stabilized. Therefore, the decrease in the amount of etching is suppressed to the extent that the characteristics of the reactive plasma are stabilized.

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

[0059] (4) When plasma is generated 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. The inner surface reduced by hydrogen plasma is then oxidized without requiring an environment or time to maintain the reduced state. This makes it possible to simplify the process required to return the nitrided inner surface to its pre-nitrided state and to shorten the time required to return the nitrided inner surface to its pre-nitrided state.

[0060] (5) In a process of etching a plurality of substrates S in a single etching chamber 11, the reduction in the amount of etching is suppressed, so that the usefulness of supplying hydrogen plasma and oxygen plasma to the inner surface of the discharge tube 24A is further increased.

[0061] The above-described embodiment can be modified as follows. [Etching chamber] The etching chamber 11 may be configured such that the first heating unit 11A is omitted, and the second heating unit 11C is omitted.

[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, to the etching chamber 11 for heating the substrate S.

[0063] The etching chamber 11 may be modified to etch one substrate S at a time. [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 in the silicon-containing film.

[0064] [Etching method] In the reforming process, a portion of a period during which a hydrogen-containing gas for generating hydrogen plasma is supplied to the discharge tube 24A may overlap a portion of a period during which an oxygen-containing gas for generating oxygen plasma is supplied to the discharge tube 24A.

[0065] An etching target may be located within the etching chamber 11 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. [Explanation of symbols]

[0066] 10. Etching equipment 10C…Control device 11…Etching chamber 12...Load lock chamber 21...Mixed gas supply section 21A: Nitrogen-containing gas supply unit 21B...Hydrogen-containing gas supply unit 21C...Oxygen-containing gas supply section 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 made of an inorganic oxide, and supplying the reactive plasma to a processing chamber to which the discharge tube is connected; generating a precursor comprising fluorine and hydrogen in the process chamber using a gas comprising fluorine and the reactive plasma, and delivering the precursor to an etching target disposed in the process chamber; 1. An etching method comprising the steps of: supplying hydrogen plasma to the inner surface of the discharge tube where the reactive plasma is generated, and supplying oxygen plasma to the inner surface to which the hydrogen plasma has been supplied.

1. An etching method comprising:

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

3. The hydrogen plasma is supplied and the oxygen plasma is supplied before and after the discharge tube generates the reactive plasma a predetermined number of times. The etching method according to claim 1 .

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

5. Supplying hydrogen plasma to the inner surface of the discharge tube means generating the hydrogen plasma in the discharge tube from hydrogen gas or ammonia gas supplied to the discharge tube. 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 to the inner surface of the discharge tube means 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 etching target is a silicon substrate having a silicon oxide film; the processing chamber accommodates a plurality of the silicon substrates such that adjacent silicon substrates are stacked with a space therebetween; supplying the precursor comprises supplying the precursor from a periphery of the silicon substrate toward the gap; The etching method according to any one of claims 1 to 5.

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