Negative ion generating device and negative ion generating method

Abstract

The negative ion generating device of the present application is a negative ion generating device that generates negative ions and irradiates the negative ions to an object, and includes: a chamber that generates negative ions inside; a negative ion generating section that generates negative ions by generating plasma inside the chamber; and a voltage applying section that can apply a bias to the object, the voltage applying section having a power source that can apply a high-frequency voltage signal.

Description

TECHNICAL FIELD

[0001] The present application relates to a negative ion generating apparatus and a negative ion generating method. BACKGROUND

[0002] In the past, as a negative ion generating apparatus, a negative ion generating apparatus described in Patent Literature 1 has been known. The negative ion generating apparatus is provided with a gas supply portion that supplies a gas that is a raw material of a negative ion into a chamber, and a negative ion generating portion that generates a negative ion by generating a plasma in the chamber. The negative ion generating portion generates a negative ion in the chamber by the plasma, and thereby irradiates the negative ion to an object.

[0003] Prior Art Documents

[0004] Patent Literature

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 2017-025407 SUMMARY

[0006] Technical Problem to be Solved by the Invention

[0007] Here, in the negative ion generating apparatus as described above, sometimes an insulator is irradiated with a negative ion as an object. At this time, there is a problem that the negative ion generating apparatus cannot sufficiently irradiate a negative ion to an insulator. Therefore, it is required that a negative ion is well irradiated regardless of an object even in a case where the object is an insulator.

[0008] Therefore, an object of one embodiment of the present application is to provide a negative ion generating apparatus and a negative ion generating method capable of well irradiating a negative ion regardless of an object.

[0009] Means for Solving the Technical Problem

[0010] In order to solve the above problem, a negative ion generating apparatus of one embodiment of the present application is a negative ion generating apparatus that generates a negative ion and irradiates the negative ion to an object, and includes a chamber in which generation of a negative ion is performed, a negative ion generating portion that generates a negative ion by generating a plasma in the chamber, and a voltage application portion that can apply a bias to the object, the voltage application portion having a power supply that can apply a high-frequency voltage signal.

[0011] The negative ion generating apparatus of one embodiment of the present application includes a voltage application portion that can apply a bias to an object. Thus, at the timing when a negative ion is generated by the negative ion generating portion, the voltage application portion applies a bias to the object, and thereby the negative ion is irradiated to the object. Here, the voltage application portion has a power supply that can apply a high-frequency voltage signal. Thus, the voltage application portion also causes a current to continuously flow through an insulator by applying a high-frequency voltage signal, and thereby can irradiate a negative ion. Thus, a negative ion can be well irradiated regardless of an object.

[0012] The power source can superimpose the high-frequency voltage signal and the direct-current voltage signal. At this time, the voltage application unit can irradiate only the negative ions to the object.

[0013] The power source can have an adjustment mechanism that adjusts the direct-current voltage signal. Thereby, the voltage application unit can adjust the amount of positive ions, for example, at the time of irradiating both the positive ions and the negative ions, and the like, superimposing the direct-current voltage signal based on the adjustment mechanism.

[0014] A negative ion generation device according to an embodiment of the present application is a negative ion generation device that generates negative ions and irradiates the negative ions to an object, and includes: a chamber in which generation of the negative ions is performed; a negative ion generation unit that generates the negative ions by generating plasma in the chamber; and a voltage application unit that is capable of applying a bias to the object, the voltage application unit having a configuration unit configured to configure a power source capable of applying a high-frequency voltage signal.

[0015] A negative ion generation method according to an embodiment of the present application is a negative ion generation method that generates negative ions and irradiates the negative ions to an object, and includes: a negative ion generation step of generating the negative ions by generating plasma in a chamber; and a voltage application step of applying a bias to the object, in which a high-frequency voltage signal is applied to the object in the voltage application step.

[0016] According to these negative ion generation device and the negative ion generation method, the same effects as the above-described negative ion generation device can be obtained.

[0017] Effects of the Invention

[0018] According to an embodiment of the present application, a negative ion generation device and a negative ion generation method that are capable of irradiating negative ions to an object well without depending on the object can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a schematic cross-sectional view that shows a structure of a negative ion generation device according to the present embodiment.

[0020] Figure 2 is a graph that shows a timing of turning on (ON) and off (OFF) of the plasma P and a condition of arrival of the positive ions and the negative ions to the object.

[0021] Figure 3 is a graph that shows a detailed structure of a voltage application unit of the negative ion generation device.

[0022] Figure 4 is a graph that shows waveforms of a voltage and a current at the time when the voltage application unit of the negative ion generation device according to the present embodiment applies a bias.

[0023] Figure 5 is a graph showing waveforms of voltage and current when a voltage applying section of a negative ion generating apparatus according to a comparative example applies a bias voltage. DETAILED DESCRIPTION

[0024] Hereinafter, a negative ion generating apparatus according to an embodiment of the present application will be described with reference to the drawings. In the description of the drawings, the same reference signs are assigned to the same elements, and repetitive description will be omitted.

[0025] First, reference will be made to Figure 1 The structure of the negative ion generating apparatus according to the embodiment of the present application will be described. Figure 1 is a schematic cross-sectional view showing the structure of the negative ion generating apparatus according to the present embodiment. In addition, for the convenience of description, Figure 1 is shown in FIG. 1. The X-axis direction is the thickness direction of the substrate as the object. The Y-axis direction and the Z-axis direction are directions orthogonal to the X-axis direction while being orthogonal to each other.

[0026] As shown in Figure 1 , the negative ion generating apparatus 1 of the present embodiment is provided with a chamber 2, an object arrangement section 3, a negative ion generating section 4, a gas supply section 6, a circuit section 7, a voltage applying section 8, and a control section 50.

[0027] The chamber 2 is a member for accommodating the substrate 11 (object) and performing irradiation processing of negative ions. The chamber 2 is a member in which generation of negative ions is performed inside. The chamber 2 is composed of a material having electrical conductivity, and is connected to a ground potential.

[0028] The chamber 2 is provided with a pair of wall sections 2a, 2b opposed to the X-axis direction, a pair of wall sections 2c, 2d opposed to the Y-axis direction, and a pair of wall sections (not shown) opposed to the Z-axis direction. In addition, the wall section 2a is arranged on the negative side in the X-axis direction, and the wall section 2b is arranged on the positive side. The wall section 2c is arranged on the negative side in the Y-axis direction, and the wall section 2d is arranged on the positive side.

[0029] The object arrangement section 3 arranges the substrate 11 that is an irradiation object of negative ions. The object arrangement section 3 is provided to the wall section 2a of the chamber 2. The object arrangement section 3 has a placement member 12 and a connection member 13. The placement member 12 and the connection member 13 are made of an electrically conductive material. The placement member 12 is a member for placing the substrate 11 on a placement surface 12a. The placement member 12 is attached to the wall section 2a and arranged in the internal space of the chamber 2. The placement surface 12a is a flat surface that extends in a direction orthogonal to the X-axis direction. Thus, the substrate 11 is placed on the placement surface 12a in a manner that is orthogonal to the X-axis direction and in a manner that is parallel to the ZY plane. The connection member 13 is a member that electrically connects the placement member 12 and the voltage application section 8. The connection member 13 extends through the wall section 2a to the outside of the chamber 2. The placement member 12 and the connection member 13 are insulated from the chamber 2.

[0030] In the present embodiment, as the substrate 11 that is an irradiation object of negative ions, a material of an insulator is used. As the substrate 11 of the insulator, for example, a glass substrate, a fine ceramic such as SiO2, SiON, AlN, Al2O3, Si3N4, a substrate to which a resin such as a phenol resin, an epoxy resin, a polyimide resin, Teflon (registered trademark) / fluororesin, or the like is added, a material of a flexible substrate such as polyimide, PET, or the like can be cited.

[0031] Next, the structure of the negative ion generation section 4 will be described in detail. The negative ion generation section 4 generates plasma and electrons in the chamber 2, thereby generating negative ions and radicals, or the like. The negative ion generation section 4 has a plasma gun 14 and an anode 16.

[0032] The plasma gun 14 is, for example, a pressure gradient type plasma gun, and a main body portion thereof is provided to the wall section 2c of the chamber 2 and connected to the internal space of the chamber 2. The plasma gun 14 has a gas supply section (not shown) that supplies a rare gas such as Ar or He, and generates plasma. The plasma gun 14 generates plasma P in the chamber 2. The plasma P generated in the plasma gun 14 is emitted in a beam shape from a plasma port to the internal space of the chamber 2. Thus, the plasma P is generated in the internal space of the chamber 2.

[0033] The anode 16 is a mechanism that guides the plasma P from the plasma gun to a desired position. The anode 16 is a mechanism that has an electromagnet for inducing the plasma P. The anode 16 is provided to the wall section 2d of the chamber and arranged at a position that faces the plasma gun 14 in the Y-axis direction. Thus, the plasma P is emitted from the plasma gun 14, diffuses in the internal space of the chamber 2 while heading to the positive side in the Y-axis direction, and is guided to the anode 16 while converging. Note that the positional relationship between the plasma gun 14 and the anode 16 is not limited to the above, and any positional relationship can be adopted as long as negative ions can be generated.

[0034] The gas supply portion 6 is arranged outside the chamber 2. The gas supply portion 6 supplies gas into the chamber 2 through a gas supply port 26 formed in the wall portion 2d. The gas supply port 26 is formed at a position between the negative ion generation portion 4 and the object arrangement portion 3. Here, the gas supply port 26 is formed at a position between the end portion of the wall portion 2d on the negative side in the X-axis direction and the anode 16. However, the position of the gas supply port 26 is not particularly limited. The gas supply portion 6 supplies gas that is a raw material of a negative ion. As the gas, for example, O2, NH3, NH4, C2H6, SiH4, or the like that is a raw material of a negative ion can be used. In addition, the gas also includes a rare gas such as Ar. - - - -

[0035] The circuit portion 7 has a variable power supply 30, a first wiring 31, a second wiring 32, resistors R1 to R3, and a switch SW1. The variable power supply 30 sandwiches the chamber 2 that is at a ground potential, applies a negative voltage to the cathode 21 of the plasma gun 14, and applies a positive voltage to the anode 16. Thus, the variable power supply 30 generates a potential difference between the cathode 21 and the anode 16 of the plasma gun 14. The first wiring 31 electrically connects the cathode 21 of the plasma gun 14 and the negative potential side of the variable power supply 30. The second wiring 32 electrically connects the anode 16 and the positive potential side of the variable power supply 30. The resistor R1 is connected in series between the first intermediate electrode 22 and the variable power supply 30. The resistor R2 is connected in series between the second intermediate electrode 23 and the variable power supply 30. The resistor R3 is connected in series between the chamber 2 and the variable power supply 30. The switch SW1 switches the on / off state by receiving an instruction signal from the control portion 50. The switch SW1 is connected in parallel to the resistor R2. The switch SW1 becomes the off state when the plasma P is generated. On the other hand, the switch SW1 becomes the on state when the plasma P is stopped.

[0036] ​​​​The voltage application section 8 applies a bias voltage to the substrate 11. The voltage application section 8 has a power supply 36 that applies a bias voltage to the substrate 11, a third wiring 37 that connects the power supply 36 and the object arrangement section 3, and a switch SW2 that is provided on the third wiring 37. The power supply 36 applies a positive voltage as the bias voltage. One end of the third wiring 37 is connected to the positive potential side of the power supply 36, and the other end is connected to the connection member 13. Thus, the third wiring 37 electrically connects the power supply 36 and the substrate 11 via the connection member 13 and the placement member 12. The switch SW2 switches its on / off state by the control of the control section 50. The switch SW2 becomes the on state at a prescribed timing when the negative ions are generated. When the switch SW2 is in the on state, the connection member 13 and the positive potential side of the power supply 36 are electrically connected to each other, and the bias voltage is applied to the connection member 13. On the other hand, the switch SW2 becomes the off state at a prescribed timing when the negative ions are generated. When the switch SW2 is in the off state, the connection member 13 and the power supply 36 are electrically disconnected from each other, and the bias voltage is not applied to the connection member 13, and the connection member 13 becomes a floating state. Further, a more detailed structure of the voltage application section 8 will be described later.

[0037] The control section 50 is a device that controls the entire negative ion generating device 1, and has an ECU [Electronic Control Unit] that centrally manages the entire device. The ECU is an electronic control unit that has a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], a CAN [Controller Area Network] communication circuit, and the like. In the ECU, for example, a program stored in the ROM is loaded to the RAM, and the program loaded to the RAM is executed by the CPU, whereby various functions are realized. The ECU can also be constituted by a plurality of electronic units.

[0038] The control section 50 is disposed outside the chamber 2. Further, the control section 50 has a gas supply control section 51 that controls the gas supply based on the gas supply section 6, a plasma control section 52 that controls the generation of the plasma P based on the negative ion generating section 4, and a voltage control section 53 that controls the application of the bias voltage based on the voltage application section 8. The control section 50 performs control to perform intermittent operation in which the generation and the stop of the plasma P are repeated.

[0039] When the switch SW1 is in the off state under the control of the plasma control unit 52, plasma P from the plasma gun 14 is ejected into the chamber 2, thus generating plasma P within the chamber 2. Plasma P is composed of neutral particles, positive ions, negative ions (in the presence of negative gases such as oxygen), and electrons. When the switch SW1 is in the on state under the control of the plasma control unit 52, plasma P from the plasma gun 14 is not ejected into the chamber 2, thus the electron temperature of plasma P within the chamber 2 drops sharply. Therefore, electrons readily attach to the particles of the gas supplied to the chamber 2. As a result, negative ions are effectively generated within the generation chamber 10b. When plasma P stops, the voltage control unit 53 controls the voltage application unit 8 to apply a positive bias voltage to the substrate 11. As a result, the negative ions within the chamber 2 are guided to the substrate 11, and the negative ions are irradiated onto the substrate 11.

[0040] Figure 2 This is a graph representing the on / off times of plasma P and the arrival of positive and negative ions towards the target object. In the graph, the area marked "on" represents the generation state of plasma P, and the area marked "off" represents the stopping state of plasma P. At time t1, plasma P stops. During the generation of plasma P, a large number of positive ions are generated. At this time, a large number of electrons are also generated in chamber 2. Moreover, when plasma P stops, the number of positive ions decreases sharply. At this time, the number of electrons also decreases. After plasma P stops, the number of negative ions increases sharply from time t2 after a predetermined time, reaching a peak at time t3. Furthermore, the number of positive ions and electrons decreases after plasma P stops, and near time t3, the amount of positive ions is the same as the amount of negative ions, while electrons almost disappear.

[0041] Next, refer to Figure 3 and Figure 4 A more detailed explanation will be given of the voltage application section 8. Figure 3 Figure (a) is a diagram showing the detailed structure of the voltage application section 8 of the negative ion generating device 1 according to this embodiment. Figure 4 It is a graph showing the waveforms of voltage and current when the voltage application section 8 applies a bias voltage.

[0042] like Figure 3 As shown in (a), the power supply 36 of the voltage application unit 8 is a power supply capable of applying a high-frequency (RF) voltage signal. Furthermore, the power supply 36 is capable of superimposing a high-frequency voltage signal and a direct-current (DC) voltage signal. The on / off interval of the plasma P is, for example, 60 Hz, and preferably can be applied at a frequency of 60 Hz or higher. Therefore, the frequency of the high-frequency voltage signal is preferably 10 kHz or higher, more preferably 13.56 MHz or higher. Additionally, the upper limit of the frequency of the high-frequency voltage signal is not particularly limited and can be 13.56 MHz or lower.

[0043] The frequency of the high-frequency voltage signal can be adjusted by a user operating an adjustment mechanism 61 provided on the power supply 36. Alternatively, the frequency of the high-frequency voltage signal of the power supply 36 can be set to a value based on a control signal of a voltage control section 53 of the control section 50. Also, the power supply 36 can stop the high-frequency voltage signal. The stopping of the high-frequency voltage signal can be switched by a user operating a switching section 62 provided on the power supply 36. Alternatively, the voltage control section 53 of the control section 50 can switch the stopping of the high-frequency voltage signal. The power supply 36 has an adjustment mechanism 63 for adjusting the direct-current voltage signal. The adjustment mechanism 63 is adjusted by a user's operation. Alternatively, the voltage control section 53 of the control section 50 can adjust the direct-current voltage signal.

[0044] The voltage application section 8 has a configuration section 71 for configuring the power supply 36. The configuration section 71 is a region configured to be able to configure the power supply 36 for high frequency. The configuration section 71 is constituted by, for example, a distribution box or a distribution substrate, and also has a mechanism for connecting the power supply 36 and the third wiring 37. Therefore, an operator configures and assembles the power supply 36 in the configuration section 71, whereby the power supply 36 can be directly connected to the third wiring. The voltage application section 8 has a configuration section 72 for configuring the switch SW2. The configuration section 72 is a region configured to be able to configure the switch SW2. The configuration section 72 is constituted by, for example, a distribution box or a distribution substrate, like the configuration section 71. In addition, the configuration section 72 can be provided in one region of the same distribution box or distribution substrate as the configuration section 71.

[0045] The power supply 36 capable of superimposing a high-frequency voltage signal can be provided in the negative ion generating apparatus 1 at the time of delivery of the negative ion generating apparatus 1 to the site. In addition to this, the negative ion generating apparatus 1 can be constituted by replacing the power supply of an already installed negative ion generating apparatus with the power supply 36 of the present embodiment. For example, in an already installed negative ion generating apparatus, as in Figure 3As shown in (b), only a DC power supply 136 is assembled in the configuration unit 71, and a DC switch SW12 is assembled in the configuration unit 72. The user removes the power supply 136 from the configuration unit 71 and reassembles the power supply 36 into the configuration unit 71. At this time, since the DC switch SW12 is of the type that only handles voltage signals of constant voltage or higher, it cannot be used as a switch for the high-frequency power supply 36. In this case, the user removes the switch SW12 from the configuration unit 72 and reassembles the switch SW2 into the configuration unit 72. Alternatively, if the switch SW12 does not have the aforementioned limitations, it can be directly used as the switch SW2. The power supply 36 configured in the configuration unit 71 can utilize a single unit that simultaneously handles high-frequency voltage signals and DC voltage signals. However, it is also possible to connect a dedicated high-frequency power supply and a dedicated DC power supply in parallel on the configuration unit 71. That is, the power supply 36 can also be composed of a combination of multiple power supplies.

[0046] Next, refer to Figure 4 The waveforms of voltage and current when a bias voltage is applied to the voltage application unit 8 are explained. The voltage application unit 8 applies a bias voltage when plasma P is off and negative ions are abundant in the chamber. Specifically, in... Figure 2 At time E1 shown, apply as follows Figure 4 The bias voltage shown. Figure 4 Figure (b) shows the voltage and current waveforms when the voltage application unit 8 applies only a high-frequency voltage signal and sets the DC voltage signal to 0. Figure 4 As shown in the voltage curve of the upper segment of (b), under the condition of only high-frequency voltage signals, the bias voltage alternately repeats positive and negative voltages. When the bias voltage is positive, negative ions irradiate the substrate 11, and when the bias voltage is negative, positive ions irradiate the substrate 11. Therefore, as... Figure 4 The current curve in the lower segment of (b) shows that the current direction is reversed at the moment of irradiation of positive ions. As an example, the current is applied at time E1, but if electron irradiation is allowed, the bias voltage can also be applied from time points t1 and t2.

[0047] As described above, when only a high-frequency voltage signal is applied, both negative and positive ions irradiate the substrate 11. Therefore, the user can adjust the ratio of negative to positive ions by superimposing a positive DC voltage signal. In the case where only negative ions are desired to irradiate the substrate 11, such as... Figure 4 As shown in the upper section of the graph in (a), the DC voltage signal is adjusted to make "high frequency + DC > 0V" in all phases. At this time, only negative ions are irradiated onto substrate 11, therefore... Figure 4As shown in the graph of the lower section of (a), current does not flow to the opposite side. In addition, in a case where a small amount of positive ions is allowed to be irradiated to the substrate 11, for example, control can be performed in a relationship of "high frequency + direct current > -(wave height value of high frequency / 2)". Alternatively, as shown in (b), only a voltage signal of high frequency can be applied. Figure 4

[0048] According to Figure 4 the contents explained in the above, the negative ion generation method will be explained. In the method, first, the negative ion generation section 4 performs a negative ion generation step of generating negative ions by generating plasma P inside the chamber 2. Next, the voltage application section 8 performs a voltage application step of applying a bias to the substrate 11. At this time, in the voltage application step, at least a voltage signal of high frequency is applied to the substrate 11. A voltage signal of direct current of what degree of magnitude is superimposed on the voltage signal of high frequency or not is set in advance. Thereby, negative ions are irradiated to the substrate 11.

[0049] Next, the effects of the negative ion generation apparatus 1 and the negative ion generation method according to the present embodiment will be explained.

[0050] The negative ion generation apparatus 1 according to the present embodiment is provided with the voltage application section 8 capable of applying a bias to the substrate 11. Therefore, at the time when the negative ion generation section 4 generates negative ions, the voltage application section 8 applies a bias to the substrate 11, whereby negative ions are irradiated to the object.

[0051] Here, reference will be made to Figure 5 The negative ion generation apparatus according to the comparative example will be explained. The negative ion generation apparatus according to the comparative example has a power source capable of applying only a voltage signal of direct current. Therefore, as shown in the graph of the upper section of Figure 5 a constant magnitude of voltage is continuously applied. At this time, as shown in the graph of the lower section, current flows at the time of application start, but since the substrate 11 is an insulator, the current immediately decreases, and then, the current stops flowing. Thus, in the negative ion generation apparatus according to the comparative example, negative ions cannot be well irradiated to the substrate 11 which is an insulator.

[0052] On the contrary, the voltage application section 8 of the negative ion generation apparatus 1 according to the present embodiment has the power source 36 capable of at least applying a voltage signal of high frequency. Therefore, the voltage application section 8 causes current to continuously flow to an insulator by applying a voltage signal of high frequency, and thereby, negative ions can be irradiated (refer to Figure 4 ). Thereby, negative ions can be well irradiated regardless of the object.

[0053] The power source 36 can superimpose a voltage signal of high frequency and a voltage signal of direct current. At this time, the voltage application section 8 can irradiate only negative ions to the substrate 11. ​

[0054] The power supply 36 can have an adjustment mechanism 63 that adjusts the voltage signal of the direct current. Thereby, the voltage application section 8, for example, at the time of irradiation of both positive ions and negative ions, etc., can adjust the amount of positive ions by superimposing the voltage signal of the direct current based on the adjustment mechanism 63.

[0055] The negative ion generating apparatus 1 according to the present embodiment is a negative ion generating apparatus 1 that generates negative ions and irradiates the negative ions onto a substrate 11, and includes: a chamber 2 that generates negative ions inside; a negative ion generating section 4 that generates negative ions by generating plasma P inside the chamber 2; and a voltage application section 8 that can apply a bias to the substrate 11, the voltage application section 8 having a disposition section 71 for disposing a power supply 36 that can apply a high-frequency voltage signal.

[0056] The negative ion generating method according to the present embodiment is a negative ion generating method that generates negative ions and irradiates the negative ions onto a substrate 11, and includes: a negative ion generating step of generating negative ions by generating plasma P inside a chamber 2; and a voltage application step of applying a bias to the substrate 11, in which a high-frequency voltage signal is applied in the voltage application step.

[0057] According to these negative ion generating apparatus 1 and negative ion generating method, the same effects / advantages as the above-described negative ion generating apparatus 1 can be obtained.

[0058] The present application is not limited to the above-described embodiments.

[0059] For example, in the above-described embodiments, the plasma gun 14 is provided as a pressure gradient type plasma gun, but the plasma gun 14 can be any type as long as it can generate plasma inside the chamber 2, and is not limited to the pressure gradient type plasma gun.

[0060] Also, in the above-described embodiments, only one set of the plasma gun 14 and the set of the anode 16 that guides the plasma P are provided inside the chamber 2, but a plurality of sets can be provided. Also, the plasma P can be supplied from a plurality of plasma guns 14 to one site.

[0061] Explanation of Symbols

[0062] 1 - negative ion generating apparatus, 2 - chamber, 4 - negative ion generating section, 8 - voltage application section, 11 - substrate (object), 36 - power supply, 53 - voltage control section (adjustment mechanism), 63 - adjustment mechanism.

Claims

1. A negative ion generating apparatus that generates negative ions and irradiates the negative ions to an object, comprising: a chamber in which the generation of the negative ions is performed; a negative ion generating section that generates the negative ions by generating plasma in the chamber; and a voltage applying section that is capable of applying a bias to the object, wherein the voltage applying section has a power source that applies a high-frequency bias to the object at the time of stopping of the plasma in intermittent operation in which the generation and the stopping of the plasma are repeated.

2. The negative ion generating apparatus according to claim 1, wherein the power source applies a high-frequency voltage signal at a frequency that is higher than the intermittent operation.

3. The negative ion generating apparatus according to claim 1, wherein the power source superimposes a high-frequency voltage signal and a direct-current voltage signal.

4. The negative ion generating apparatus according to claim 3, wherein the power source has an adjustment mechanism that adjusts the direct-current voltage signal.

5. A negative ion generating apparatus that generates negative ions and irradiates the negative ions to an object, comprising: a chamber in which the generation of the negative ions is performed; a negative ion generating section that generates the negative ions by generating plasma in the chamber; and a voltage applying section that is capable of applying a bias to the object, wherein the voltage applying section has a disposition section that disposes a power source that applies a high-frequency bias to the object at the time of stopping of the plasma in intermittent operation in which the generation and the stopping of the plasma are repeated.

6. A negative ion generating method that generates negative ions and irradiates the negative ions to an object, comprising: a negative ion generating step of generating the negative ions by generating plasma in a chamber; and a voltage applying step of applying a bias to the object, wherein in the voltage applying step, a high-frequency bias is applied to the object at the time of stopping of the plasma in intermittent operation in which the generation and the stopping of the plasma are repeated. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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