Plasma processing method and plasma processing apparatus

Abstract

To provide a plasma processing method and a plasma processing apparatus that can achieve a high oxide film reduction rate and suppress damage to a substrate.SOLUTION: A plasma processing method includes: a placing step of placing a substrate having a surface including a metal and an oxide film formed on the metal in a plasma processing chamber; and a first step of reducing the oxide film by introducing a first gas into the plasma processing chamber to generate first plasma. The oxide film is a film formed by oxidizing the surface of the metal. The first gas contains water vapor and argon. In the first gas, a ratio Va / Vw of a volume Va of the argon to a volume Vw of the water vapor is in a range of 0.01 to 1.50.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a plasma processing method and a plasma processing apparatus. [Background technology]

[0002] Circuit elements mounted on a circuit board or the like usually have electrodes formed thereon for electrically connecting the elements to each other. An oxide film of the metal contained in the electrode is formed on the surface of the electrode. It is known that such a surface oxide film reduces the connection strength of the joint formed on the electrode. Techniques for removing the surface oxide film have been proposed in the past.

[0003] Claim 1 of Patent Document 1 (JP Patent Publication No. 2001-262378) describes, "A plasma processing method for removing an oxide film on a surface of an electrode, the surface of which is made of copper or a copper alloy, by plasma processing the object to be processed, the electrode having such an electrode surface, the method comprising the steps of: subjecting the object to be processed to plasma processing using a plasma generating gas containing a reducing gas; and cooling the object to be processed to room temperature in a reducing gas atmosphere following the plasma processing." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-262378 A Summary of the Invention [Problem to be solved by the invention]

[0005] Regarding the removal of oxide films, there is a demand for an improvement in the reduction rate of the oxide films. Meanwhile, in the reduction of the oxide films, it is necessary to suppress damage to the substrate other than the oxide films. One of the objectives of the present disclosure is to provide a plasma processing method and a plasma processing apparatus that can achieve a high reduction rate of the oxide films and suppress damage to the substrate. [Means for solving the problem]

[0006] One aspect of the present disclosure is a plasma processing method, comprising: A placement step of placing a substrate including a metal and an oxide film formed on the metal on a surface thereof in a plasma processing chamber; a first step of reducing the oxide film by introducing a first gas into the plasma processing chamber to generate a first plasma; the oxide film is a film formed by oxidizing a surface of the metal, The first gas contains water vapor and argon, In the first gas, a ratio Va / Vw of the volume Va of the argon to the volume Vw of the water vapor is in the range of 0.01 to 1.50.

[0007] Another aspect of the present disclosure is a plasma processing apparatus for processing a substrate including a metal and an oxide film formed on the metal on a surface thereof, the plasma processing apparatus comprising: a chamber having a plasma processing chamber in which the substrate is plasma processed; a gas supply device that controls a gas supplied from a gas supply source and supplies the gas as a process gas to the plasma processing chamber; an electrode and a power source for generating plasma in the plasma processing chamber; the oxide film is a film formed by oxidizing a surface of the metal, a first step of plasma processing the substrate with a first plasma in the plasma processing chamber is performed; In the first step, a first gas is supplied as the process gas to the plasma processing chamber; The first gas contains water vapor and argon, The plasma processing apparatus relates to a ratio Va / Vw of the volume Va of the argon to the volume Vw of the water vapor in the first gas, which is in the range of 0.01 to 1.50. Effect of the Invention

[0008] According to the present disclosure, it is possible to perform plasma processing that can achieve a high oxide film reduction rate and suppress damage to a substrate. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a plasma processing apparatus according to the first embodiment. [Diagram 2] FIG. 2 is a graph showing the results of the evaluation carried out in the examples. [Diagram 3] FIG. 3 is a graph showing an example of the emission spectrum of the plasma measured in the example. [Figure 4] FIG. 4 is a graph showing another example of the emission spectrum of the plasma measured in the example. [Diagram 5] FIG. 5 is a graph showing another example of the emission spectrum of the plasma measured in the example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the following, the embodiment according to the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and other materials may be applied as long as the invention according to the present disclosure can be implemented. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "numerical value A or more and numerical value B or less." In the following description, when a lower limit and an upper limit of a numerical value related to a specific physical property or condition are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined as long as the lower limit is not equal to or greater than the upper limit. In the following description, when examples of components or methods are listed, only one of the listed examples may be used, or multiple of the listed examples may be used in combination, unless otherwise specified.

[0011] (Plasma treatment method) The plasma processing method according to this embodiment may be referred to as a "processing method (M)" below. The processing method (M) includes a placement step and a first step. These steps will be described below.

[0012] (Placement process) The placement step is a step of placing a substrate having a surface including a metal and an oxide film formed on the metal, in a plasma processing chamber. The oxide film is a film formed by oxidizing the surface of a metal. At least a part of the oxide film (surface oxide film) present on the surface of the metal is exposed. In the processing method (M), at least a part of the exposed oxide film is reduced by the first step.

[0013] The metal having an oxidized surface is not particularly limited, and may be any metal for which a surface oxide film is required to be reduced. Examples of the metal having an oxidized surface include electrodes and wiring of an element. The metal having an oxidized surface may be copper, a copper alloy, or silver, or may be copper or silver. Examples of the element include an LED element, a MOSFET element, and various other elements.

[0014] An electrode (such as a pad) of an element (such as an LED element) may be connected to wiring (such as a circuit wiring or a lead frame) by wire bonding or the like. If an oxide film is formed on the surface of the electrode or wiring, connection failures are likely to occur. For this reason, it is important to reduce (or remove) the surface oxide film. Furthermore, reducing the surface oxide film increases the wettability of the sealing resin, thereby improving the reliability of sealing by the sealing resin. At least one element may be arranged on the substrate, or multiple elements may be arranged on the substrate.

[0015] (1st step) The first step is a step of reducing the oxide film by introducing a first gas (process gas) into a plasma processing chamber to generate a first plasma. The first gas contains water vapor and argon (argon gas). In the first gas, a ratio Va / Vw of a volume Va of argon to a volume Vw of water vapor is in a range of 0.01 to 1.50. In the first step, hydrogen radicals are generated in the first plasma by using water vapor as the process gas. In the first step, the substrate is exposed to the first plasma, and at least a part of the exposed oxide film is reduced by the generated hydrogen radicals.

[0016] As shown in the examples, by setting the ratio Va / Vw in the range of 0.01 to 1.50, the reduction rate Rr of the oxide film can be increased while keeping the etching rate Re of the metal low. That is, by setting the ratio Va / Vw in the range of 0.01 to 1.50, both a high reduction rate Rr of the oxide film and a low etching rate Re of the metal can be achieved. This makes it possible to increase the ratio of the reduction rate Rr to the etching rate Re (selection ratio Rr / Re). By increasing the selection ratio Rr / Re, it is possible to suppress damage to the metal and reduce the oxide film in a short time. The reduction rate of the oxide film is the thickness of the oxide film reduced per unit time.

[0017] The first gas may be composed of only water vapor and argon. The first gas may contain other gases besides water vapor and argon. In a preferred example, the first gas does not contain oxygen gas.

[0018] The first step is performed before a step in which the presence of an oxide film would cause a disadvantage, for example, before the step of connecting the electrodes and the wiring.

[0019] The first plasma can be generated by supplying high-frequency power to an electrode (plasma generating electrode) while the first gas is introduced into the plasma processing chamber. The high-frequency power may be 20 W or more, or 150 W or more, and may be 1000 W or less, or 450 W or less. The frequency of the high-frequency power (high-frequency voltage) may be in the range of 3 MHz to 30 MHz (e.g., 13.56 MHz). The pressure in the plasma processing chamber when the first plasma is generated may be 1 Pa or more, or 5 Pa or more, and may be 132 Pa or less, or 30 Pa or less.

[0020] The ratio Va / Vw can be controlled by controlling the flow rates of water vapor and argon (argon gas) supplied to the plasma processing chamber. Water vapor and argon may be supplied to the plasma processing chamber separately, or may be supplied to the plasma processing chamber in a mixed state. By supplying water vapor and argon to the plasma processing chamber in a mixed state, more uniform processing can be achieved.

[0021] The substrate stage on which the substrate is placed may be the electrode to which the voltage for generating plasma is applied, or the electrode may be located within the substrate stage, or the electrode to which the voltage for generating plasma is applied may be located at a position other than the substrate stage.

[0022] The first step may be performed under conditions that generate a significant self-bias voltage between the substrate stage functioning as an electrode and the first plasma. Alternatively, the first step may be performed under conditions that do not generate a significant self-bias voltage between the substrate stage and the first plasma. The self-bias voltage may be generated using a power source for generating the self-bias voltage. For example, a high frequency power source for generating the self-bias voltage may be connected to the substrate stage functioning as an electrode.

[0023] The time for which the first step is performed may be selected in consideration of the reduction rate of the oxide film, the thickness of the surface oxide film to be reduced, etc. The first step is preferably performed for a time sufficient for all of the surface oxide film to be reduced.

[0024] The ratio Va / Vw is preferably in the range of 0.01 to 1.00, or 0.50 to 1.00, in which case both a high reduction rate Rr of the oxide film and a particularly high selectivity Rr / Re can be achieved.

[0025] The first step may be performed in a state where the temperature of the substrate is 60° C. or less (for example, 50° C. or less). By performing the first step in a state where the temperature of the substrate is 60° C. or less, reoxidation of the metal can be suppressed. The temperature of the substrate may be controlled by the time for generating the first plasma, a cooling gas, or the like. For example, if the substrate temperature rises and approaches 60° C. during the treatment with the first plasma, the treatment with the first plasma may be stopped, and a cooling gas may be introduced into the plasma treatment chamber during the stop period to cool the substrate. Then, after the substrate temperature has decreased, the treatment with the first plasma may be performed again. Examples of the cooling gas include nitrogen gas and rare gas (for example, argon gas or helium gas). Alternatively, the substrate temperature may be controlled to 60° C. or less by cooling the substrate stage on which the substrate is placed. In that case, a substrate stage having a flow passage through which a coolant flows may be used. The lower limit of the substrate temperature when the first step is performed is not particularly limited, and may be 0° C. or more.

[0026] (2nd process) The processing method (M) may further include a second step of generating a second plasma by introducing a second gas (process gas) containing nitrogen atoms into the plasma processing chamber after the first step, and exposing the substrate to the second plasma. The second step can suppress reoxidation of the metal surface whose oxide film has been reduced. The second gas may contain nitrogen gas or may be nitrogen gas. Alternatively, the second gas may be at least one gas selected from the group consisting of nitrogen gas and ammonia gas.

[0027] The second plasma may be generated under the conditions exemplified for the first plasma, except that the process gas is different. The time for which the second process is performed is not particularly limited. The time for which the second process is performed may be in the range of 1 second to 120 seconds.

[0028] In the processing method (M), when the substrate that has undergone the first step is removed from the plasma processing chamber, an inert gas may be introduced into the plasma processing chamber to release the reduced pressure in the plasma processing chamber. Examples of the inert gas include nitrogen gas and rare gases (e.g., argon gas and helium gas). By using an inert gas as a gas for releasing the reduced pressure in the plasma processing chamber, reoxidation of the metal surface where the oxide film has been reduced can be suppressed.

[0029] (Plasma processing equipment) The plasma processing apparatus according to this embodiment may be referred to as the "processing apparatus (A)" below. The processing apparatus (A) allows the above-mentioned processing method (M) to be easily performed. However, the processing method (M) may be performed using an apparatus other than the processing apparatus (A). The matters described for the processing method (M) can be applied to the processing apparatus (A), so duplicated explanations will be omitted. The matters described for the processing apparatus (A) may also be applied to the processing method (M).

[0030] The processing apparatus (A) is a plasma processing apparatus for processing a substrate containing an oxidized metal on the surface. The processing apparatus (A) includes a chamber having a plasma processing chamber in which the substrate is plasma-processed, a gas supply device for controlling a gas supplied from a gas supply source and supplying it to the plasma processing chamber as a process gas, and an electrode and a power supply for generating plasma in the plasma processing chamber. In the processing apparatus (A), a first step is performed in which the substrate is plasma-processed with a first plasma in the plasma processing chamber. In the first step, a first gas is supplied to the plasma processing chamber as the process gas. The first gas contains water vapor and argon. In the first gas, a ratio Va / Vw of a volume Va of argon to a volume Vw of water vapor is in a range of 0.01 to 1.50.

[0031] The first step performed in the treatment device (A) corresponds to the first step performed in the treatment method (M). In the treatment device (A), the first step is performed using a first gas having a Va / Vw ratio in the range of 0.01 to 1.50. Therefore, the treatment device (A) can obtain the same effect as that obtained in the treatment method (M).

[0032] The gas supply source supplies water vapor and argon gas. The water vapor supply source is not particularly limited, and a known water vapor supply source may be used. For example, a vaporizer that vaporizes water may be used as the water vapor supply source. An argon gas cylinder or the like may be used as the argon gas supply source.

[0033] The gas supply device controls the flow rate of the gas supplied from the gas supply source and supplies it to the plasma processing chamber. A mass flow controller or the like can be used for the gas supply device. The volume ratio of the gases constituting the process gas (first gas, second gas) can be considered to be the same as the flow rate ratio of the gases supplied to the plasma processing chamber.

[0034] The electrodes and power source for generating plasma are not particularly limited, and electrodes and power sources used in known plasma processing apparatuses may be used.

[0035] The processing apparatus may include other devices in addition to the above-mentioned devices as necessary. Examples of the other devices include a pressure reducing device (e.g., a vacuum pump) for reducing the pressure inside the plasma processing chamber, a pressure gauge for monitoring the pressure inside the plasma processing chamber, a thermometer for monitoring the temperature of the substrate (or the temperature of the substrate stage), and a control device. These devices may be the same as those used in known plasma processing apparatuses.

[0036] The control device includes a storage device in which a program for executing a predetermined process is stored, and controls the predetermined equipment based on the program. The control device is connected to measuring equipment (pressure gauge, thermometer, etc.), and performs control according to the output of the measuring equipment. In the first process, the control device controls the predetermined equipment (gas supply device, power supply, etc.) so that a first plasma is generated with a first gas introduced into the plasma processing chamber. For example, the control device controls the gas supply device so that a ratio Va / Vw of a volume Va of argon to a volume Vw of water vapor in the first gas is in a range of 0.01 to 1.50.

[0037] In the processing apparatus (A), the ratio Va / Vw is preferably in the range of 0.50 to 1.00. In the processing apparatus (A), the first step may be performed in a state where the temperature of the substrate is 60° C. or less. In the processing apparatus (A), after the first step, a second step of processing the substrate with a second plasma in the plasma processing chamber may be performed. In that case, in the second step, a second gas containing nitrogen atoms may be supplied as a process gas to the plasma processing chamber. The second step performed in the processing apparatus (A) corresponds to the second step performed in the processing method (M). When the second step is performed, the control device controls a predetermined device (gas supply device, power source, etc.) so that a second plasma is generated in a state where the second gas is introduced into the plasma processing chamber.

[0038] In another aspect, the present disclosure discloses a method for manufacturing a device mounting substrate (PM). The manufacturing method (PM) includes a step (i) of treating a substrate including at least one device having at least one electrode and wiring by a processing method (M). The manufacturing method (PM) may further include a step (ii) of connecting the at least one electrode and the wiring by wire bonding after the step (i). The manufacturing method (PM) may further include a step (iii) of sealing the substrate that has been subjected to the step (ii) with a sealing resin after the step (ii). The sealing resin is not particularly limited, and a known sealing resin (such as a silicone resin or an epoxy resin) may be used. The at least one device may include a semiconductor light emitting element (such as a light emitting diode). The device mounting substrate may be a light emitting device including a light emitting diode.

[0039] An example of this embodiment will be specifically described below with reference to the drawings. The steps and components described above can be applied to the steps and components of the example described below. The steps and components of the example described below can be modified based on the above description. The matters described below may also be applied to the above embodiment. In addition, among the steps and components described below, steps and components that are not essential to the processing method (M) and processing device (A) according to the present disclosure may be omitted.

[0040] (Embodiment 1) In the embodiment 1, an example of a processing apparatus (A) and a processing method (M) will be described. The configuration of a plasma processing apparatus 100 of the embodiment 1 is shown in FIG.

[0041] The plasma processing apparatus 100 includes a chamber 110, a gas supply device 120, an electrode 130, a power supply 140, a pressure reduction device 150, and a control device 200. The inside of the chamber 110 is a plasma processing chamber 111. A substrate 10 having a surface including a metal and an oxide film formed on the metal is placed in the plasma processing chamber 111. The pressure in the plasma processing chamber 111 is reduced by the pressure reduction device 150.

[0042] The gas supply device (gas flow rate control device) 120 includes a plurality of mass flow controllers that control the flow rate of the gas supplied from the gas supply source 20. The gas supply source 20 includes a plurality of gas supply sources corresponding to the gases to be supplied. At least a part of the gas supply source 20 (e.g., a gas cylinder) may or may not be included in the plasma processing apparatus 100.

[0043] 1, the gas supply source 20 includes a water vapor supply source 21, an argon gas supply source 22, and a nitrogen gas supply source 23, and the gas supply device 120 includes mass flow controllers 121 to 123 corresponding thereto. The gases whose flow rates are controlled by the gas supply device 120 are mixed in a gas flow path 125 and introduced into the plasma processing chamber 111. When the second step is not performed, the nitrogen gas supply source 23 and the mass flow controller 123 are not necessary.

[0044] 1 includes a lower electrode 131 and an upper electrode 132 as an electrode 130. The lower electrode 131 is connected to a power supply 140 which is a high frequency power supply. The upper electrode 132 is connected to earth. The lower electrode 131 also functions as a substrate stage on which the substrate 10 is placed. If necessary, a matching circuit or the like may be connected between the electrode 130 and the power supply 140.

[0045] With a process gas introduced into the plasma processing chamber 111, a high frequency voltage is applied to the lower electrode 131 to generate plasma. With this configuration, it is possible to generate the self-bias voltage described above. The configuration of the electrodes and the power supply is not limited to the configuration shown in FIG. 1. For example, a high frequency power supply for generating plasma may be connected to the upper electrode 132. Alternatively, a high frequency power supply for generating plasma may be connected to the upper electrode 132, and a power supply for generating the self-bias voltage may be connected to the lower electrode 131.

[0046] The control device 200 is connected to predetermined devices and controls these devices. The above-mentioned steps are executed by the control device 200. An example of executing the first step using the plasma processing device 100 will be described below.

[0047] First, the substrate 10 is placed in the plasma processing chamber 111. Specifically, the substrate 10 is placed on the lower electrode 131, which is a substrate stage. Next, the gas supply device 120 is controlled to introduce the above-mentioned first gas into the plasma processing chamber 111. Next, a high-frequency voltage is applied to the lower electrode 131 to generate a first plasma in the plasma processing chamber 111. The substrate 10 is exposed to the first plasma, which reduces the metal oxide film on the substrate 10. In this manner, the first step is performed.

[0048] When the second step is performed, after the first step, the gas supply device 120 is controlled to introduce the above-mentioned second gas into the plasma processing chamber 111. Next, a high-frequency voltage is applied to the lower electrode 131 to generate a second plasma in the plasma processing chamber 111. The substrate 10 is exposed to the second plasma, whereby the substrate 10 is processed.

[0049] After the above-mentioned processing is performed, the chamber 110 is opened and the substrate 10 is removed. When the pressure inside the plasma processing chamber 111 is returned to atmospheric pressure, the reduced pressure state inside the plasma processing chamber may be released by introducing an inert gas into the plasma processing chamber, as described above.

[0050] (Additional Note) The above description of the embodiments discloses the following techniques. (Technology 1) 1. A plasma processing method, comprising: A placement step of placing a substrate including a metal and an oxide film formed on the metal on a surface thereof in a plasma processing chamber; a first step of reducing the oxide film by introducing a first gas into the plasma processing chamber to generate a first plasma; the oxide film is a film formed by oxidizing a surface of the metal, The first gas contains water vapor and argon, The plasma processing method, wherein in the first gas, a ratio Va / Vw of the volume Va of the argon to the volume Vw of the water vapor is in the range of 0.01 to 1.50. (Technology 2) The plasma processing method according to technique 1, wherein the ratio Va / Vw is in the range of 0.50 to 1.00. (Technology 3) 3. The plasma processing method according to claim 1, wherein the first step is performed in a state where the temperature of the substrate is 60° C. or less. (Technology 4) The plasma processing method according to any one of Techniques 1 to 3, further comprising a second step of introducing a second gas containing nitrogen atoms into the plasma processing chamber after the first step to generate a second plasma and exposing the substrate to the second plasma. (Technology 5) 1. A plasma processing apparatus for processing a substrate having a surface including a metal and an oxide film formed on the metal, comprising: a chamber having a plasma processing chamber in which the substrate is plasma processed; a gas supply device that controls a gas supplied from a gas supply source and supplies the gas as a process gas to the plasma processing chamber; an electrode and a power source for generating plasma in the plasma processing chamber; the oxide film is a film formed by oxidizing a surface of the metal, a first step of plasma processing the substrate with a first plasma in the plasma processing chamber is performed; In the first step, a first gas is supplied as the process gas to the plasma processing chamber; The first gas contains water vapor and argon, The plasma processing apparatus, wherein in the first gas, a ratio Va / Vw of a volume Va of the argon to a volume Vw of the water vapor is in a range of 0.01 to 1.50. (Technology 6) The plasma processing apparatus according to technique 5, wherein the ratio Va / Vw is in the range of 0.50 to 1.00. (Technology 7) The plasma processing apparatus according to technique 5 or 6, wherein the first step is performed in a state where the temperature of the substrate is 60° C. or less. (Technology 8) a second step of treating the substrate with a second plasma in the plasma processing chamber is performed after the first step; The plasma processing apparatus according to any one of Techniques 5 to 7, wherein in the second step, a second gas containing nitrogen atoms is supplied to the plasma processing chamber as the process gas. EXAMPLES

[0051] The processing method and processing apparatus according to the present disclosure will be described in more detail with reference to an example. In this example, the effect of changing the process gas in plasma processing was evaluated. The processing apparatus used was the same as that shown in FIG.

[0052] Water vapor or a mixture of water vapor and argon gas was used as the process gas. The reduction rate Rr of the oxide film and the etching rate Re of the metal (copper) were evaluated when the ratio Va / Vw of the argon gas volume Va to the water vapor volume Vw was changed. A 13.56 MHz high-frequency power (600 W) was applied to the lower electrode, and the flow rate of the argon gas relative to the flow rate of the water vapor was changed.

[0053] The reduction rate Rr of the oxide film was obtained by the following procedure. First, a plurality of substrates (e.g., glass substrates) were prepared on the surface of which an oxide film (e.g., a CuO film with a thickness of X) was formed. Next, the surface of the substrate was exposed to plasma, and the compositional depth distribution of the substrate surface after the plasma treatment was measured using XPS (X-ray photoelectron spectroscopy). Then, the compositional depth distribution of the substrate surface was measured for a plurality of substrates with different plasma treatment times, and the results were compared to derive the time T1 required for the entire oxide film to be reduced to a metal film (e.g., a Cu film) and the thickness Y of the metal film when the entire oxide film with a thickness of X was reduced to a metal film. The reduction rate Rr is the thickness of the oxide film reduced per unit time, and was calculated by the formula Rr=X / T1.

[0054] The etching rate Re of the metal film was calculated by the following procedure. First, a substrate was prepared on which an oxide film (e.g., CuO) with a thickness of X was formed. Next, the surface of the substrate was exposed to plasma, and the total time T3 from when the oxide film was reduced to a metal film and when the metal film disappeared was measured. Here, the time T1 required for the oxide film (thickness X) to be reduced and the thickness Y of the metal film at that time were known from the above-mentioned experiment performed to calculate the reduction rate Rr of the oxide film. The time T2 required for the metal film with thickness Y to disappear was calculated by the formula T2=T3-T1. The etching rate Re was calculated by the formula Re=Y / T2.

[0055] The composition of the process gas and the evaluation results are shown in Table 1. The Ar flow rate (argon gas flow rate) in Table 1 is a relative value when the water vapor flow rate is set to 100. In Table 1, the ratio of the argon gas flow rate to the water vapor flow rate was considered to be the ratio Va / Vw. The reduction rate Rr in Table 1 indicates the thickness of the oxide film reduced per minute of plasma processing.

[0056] [Table 1]

[0057] The results of Table 1 are shown in FIG. 2. As is clear from Table 1 and FIG. 2, by setting the ratio Va / Vw in the range of 0.01 to 1.50, it was possible to achieve both a high reduction rate Rr of the oxide film and a low etching rate Re of the metal. Furthermore, by setting the ratio Va / Vw in the range of 0.01 to 1.00 or in the range of 0.50 to 1.00, it was possible to achieve both a high reduction rate Rr of the oxide film and a particularly high selectivity Rr / Re. For example, by setting the ratio Va / Vw in the range of 0.01 to 1.00, it was possible to achieve an etching rate Re of 0.1 nm / min or more and a selectivity Rr / Re of 107 or more. Furthermore, from Table 1 and FIG. 2, it is considered that by setting the ratio Va / Vw in the range of 0.01 to 1.50, it is possible to achieve an etching rate Re of 0.1 nm / min or more and a selectivity Rr / Re of 80 or more. By increasing the selection ratio Rr / Re, it is possible to reduce damage to metals (electrodes, etc.) and to reduce oxide films in a short period of time.

[0058] In the above experiment, the emission spectrum of the plasma was measured when the ratio Va / Vw was changed. In addition, in the above experiment, the emission spectrum of the plasma was measured when the process gas was changed to a mixed gas of water vapor and oxygen gas. In this case, the flow rate of the water vapor and the flow rate of the oxygen gas were each 10 mL / min. The measured emission spectra are shown in Figures 3 to 5. The vertical axis of Figures 3 to 5 indicates the emission intensity.

[0059] Fig. 3 shows the emission spectrum when the ratio Va / Vw = 0 (comparative example). Fig. 4 shows the emission spectrum when the ratio Va / Vw = 1.00. Fig. 5 shows the emission spectrum when a mixed gas of water vapor and oxygen gas is used as the process gas. Each figure shows the emission intensity of the hydrogen Hα line peak (near 656 nm) as a numerical value.

[0060] As is clear from a comparison of Figures 3 and 4, the intensity of the hydrogen atom emission spectrum Hα is increased by using a mixed gas of water vapor gas and argon gas as the process gas. This suggests that the use of a mixed gas of water vapor gas and argon gas as the process gas increases the number of hydrogen radicals. As is clear from a comparison of Figures 4 and 5, the intensity of Hα is decreased by adding oxygen gas to water vapor gas. This suggests that the addition of oxygen gas to water vapor gas reduces the number of hydrogen radicals. [Industrial Applicability]

[0061] The present disclosure can be used for a plasma processing method and a plasma processing apparatus. [Explanation of symbols]

[0062] 10: Substrate 20: Gas supply source 100: Plasma processing device 110: Chamber 111: Plasma processing chamber 120: Gas supply equipment 130: Electrode 140: Power supply

Claims

1. 1. A plasma processing method, comprising: A placement step of placing a substrate including a metal and an oxide film formed on the metal on a surface thereof in a plasma processing chamber; a first step of reducing the oxide film by introducing a first gas into the plasma processing chamber to generate a first plasma; the oxide film is a film formed by oxidizing a surface of the metal, The first gas contains water vapor and argon, In the first gas, a ratio Va / Vw of a volume Va of the argon to a volume Vw of the water vapor is in a range of 0.01 to 1.

50.

2. 2. The plasma processing method according to claim 1, wherein the ratio Va / Vw is in the range of 0.50 to 1.

00.

3. 3. The plasma processing method according to claim 1, wherein the first step is performed in a state where the temperature of the substrate is 60[deg.] C. or less.

4. 3. The plasma processing method according to claim 1, further comprising a second step of introducing a second gas containing nitrogen atoms into the plasma processing chamber after the first step to generate a second plasma, and exposing the substrate to the second plasma.

5. 1. A plasma processing apparatus for processing a substrate having a surface including a metal and an oxide film formed on the metal, comprising: a chamber having a plasma processing chamber in which the substrate is plasma processed; a gas supply device that controls a gas supplied from a gas supply source and supplies the gas as a process gas to the plasma processing chamber; an electrode and a power source for generating plasma in the plasma processing chamber; the oxide film is a film formed by oxidizing a surface of the metal, a first step of plasma processing the substrate with a first plasma in the plasma processing chamber is performed; In the first step, a first gas is supplied as the process gas to the plasma processing chamber; The first gas contains water vapor and argon, In the first gas, a ratio Va / Vw of a volume Va of the argon to a volume Vw of the water vapor is in a range of 0.01 to 1.

50.

6. 6. The plasma processing apparatus according to claim 5, wherein the ratio Va / Vw is in a range of 0.50 to 1.

00.

7. 7. The plasma processing apparatus according to claim 5, wherein the first step is performed in a state where the temperature of the substrate is 60[deg.] C. or less.

8. After the first step, a second step of treating the substrate with a second plasma is performed in the plasma processing chamber; 7. The plasma processing apparatus according to claim 5, wherein in the second step, a second gas containing nitrogen atoms is supplied as the process gas to the plasma processing chamber.

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