Negative ion generator and method

Abstract

To provide a negative ion generation device that can irradiate a target object with negative ions at an appropriate time.SOLUTION: A negative ion generation device 1 includes a negative ion generation unit 4 that generates negative ions by generating plasma P in a chamber 2. Therefore, after the negative ion generation unit 4 stops the plasma P, a substrate 11 can be irradiated with negative ions. Here, the negative ion generation device 1 includes a detection unit 40 that detects generation and disappearance of plasma P. Therefore, the negative ion generation device 1 can irradiate the substrate 11 with negative ions after the detection unit 40 confirms that the plasma P has disappeared. Therefore, negative ion irradiation can be performed at appropriate timing. The substrate 11 can be irradiated with negative ions at appropriate timing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a negative ion generating device.

Background Art

[0002] Conventionally, as a negative ion generating device, the one described in Patent Document 1 is known. This negative ion generating device includes a gas supply unit that supplies a gas serving as a raw material for negative ions into a chamber, and a negative ion generating unit that generates negative ions by generating plasma in the chamber. The negative ion generating unit irradiates the target object with the negative ions generated in the chamber by the plasma. The negative ion generating device irradiates the target object with negative ions at the timing when the plasma is turned off.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, the above-described negative ion generating device measures the potential in the chamber after the plasma is stopped, and grasps the appropriate timing for irradiating the target object with negative ions based on the measurement result. However, in order to incorporate such a potential measurement probe, a vacuum introduction mechanism into the chamber or the like is required, and there is a problem that the detection becomes complicated. On the other hand, after performing the plasma OFF control, negative ions may be irradiated to the target object after a predetermined delay time has elapsed. However, in such a negative ion generating device, even after performing the plasma OFF control, the plasma may not disappear and the plasma ON state may continue. When trying to irradiate the target object with negative ions in such a case, there is a possibility of damaging the target object or the device.

[0005] Therefore, the present invention aims to provide a negative ion generator that can irradiate an object with negative ions at an appropriate timing. [Means for solving the problem]

[0006] To solve the above problems, the negative ion generating apparatus according to the present invention is a negative ion generating apparatus that generates negative ions and irradiates a target object, comprising: a chamber in which negative ions are generated internally; a negative ion generating unit that generates negative ions by generating plasma in the chamber; and a detection unit that detects the generation and disappearance of plasma.

[0007] The negative ion generator according to the present invention includes a negative ion generation unit that generates negative ions by generating plasma in a chamber. Therefore, after the negative ion generation unit stops generating plasma, it becomes possible to irradiate the target object with negative ions. The negative ion generator also includes a detection unit that detects the generation and disappearance of plasma. Therefore, after the detection unit confirms the disappearance of plasma, the negative ion generator can irradiate the target object with negative ions. Thus, it is possible to irradiate the target object with negative ions at an appropriate timing.

[0008] The detection unit may have a photodetector element that detects the amount of light inside the chamber. When plasma is generated, plasma light is always emitted, and as the plasma disappears, this light decreases. Therefore, the detection unit can accurately detect the disappearance of the plasma by monitoring the plasma light with the photodetector element.

[0009] The photodetector may be mounted on the viewport of the chamber. In this case, the photodetector can detect the disappearance of the plasma from outside the chamber. Therefore, the photodetector can be easily incorporated into the device.

[0010] The negative ion generator may stop operating based on the detection results of the detection unit. In this case, if plasma disappearance is not detected despite the plasma OFF control being applied, the device may be considered to have a malfunction and its operation may be stopped. This allows for maintenance to be performed after the operation has stopped.

[0011] The detection unit may detect the voltage at a predetermined location within the negative ion generator. In this case, it becomes possible to detect the disappearance of the plasma without adding a photodetector or the like.

[0012] The detection unit may detect the pressure inside the chamber. In this case, it becomes possible to detect the disappearance of the plasma using an existing pressure gauge or the like, without adding an optical detection element or the like. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a negative ion generator that can irradiate an object with negative ions at an appropriate timing. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic cross-sectional view showing the configuration of the negative ion generator according to this embodiment. [Figure 2] This graph shows the ON / OFF timing of plasma P and the arrival of positive and negative ions at the target object. [Figure 3] The time change of the anode voltage V and the time change of the detection signal, i.e., the amount of light, detected by the photodetector are shown. [Figure 4] This diagram illustrates the malfunctions that occur when a bias voltage is applied while the plasma is ON. [Figure 5] This graph shows the time variation of the voltage at each point. [Figure 6] This graph shows the time variation of the voltage between the anode and cathode. [Modes for carrying out the invention]

[0015] Hereinafter, a negative ion generation device according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0016] First, referring to FIG. 1, the configuration of the negative ion generation device according to the embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view showing the configuration of the negative ion generation device according to the present embodiment. For the sake of convenience of explanation, an XYZ coordinate system is shown in FIG. 1. The X-axis direction is the thickness direction of the substrate, which is the object. The Y-axis direction and the Z-axis direction are directions orthogonal to the X-axis direction and orthogonal to each other.

[0017] As shown in FIG. 1, the negative ion generation device 1 of the present embodiment includes a chamber 2, an object placement unit 3, a negative ion generation unit 4, a gas supply unit 6, a circuit unit 7, a voltage application unit 8, and a control unit 50.

[0018] The chamber 2 is a member for housing the substrate 11 (object) and performing the irradiation treatment of negative ions. The chamber 2 is a member in which negative ions are generated inside. The chamber 2 is made of a conductive material and is connected to the ground potential.

[0019] The chamber 2 includes a pair of wall portions 2a and 2b facing each other in the X-axis direction, a pair of wall portions 2c and 2d facing each other in the Y-axis direction, and a pair of wall portions (not shown) facing each other in the Z-axis direction. The wall portion 2a is arranged on the negative side in the X-axis direction, and the wall portion 2b is arranged on the positive side. The wall portion 2c is arranged on the negative side in the Y-axis direction, and the wall portion 2d is arranged on the positive side.

[0020] The object placement section 3 is used to position the substrate 11, which will be irradiated with negative ions. The object placement section 3 is provided on the wall 2a of the chamber 2. The object placement section 3 comprises a mounting member 12 and a connecting member 13. The mounting member 12 and the connecting member 13 are made of conductive material. The mounting member 12 is a member for mounting the substrate 11 on the mounting surface 12a. The mounting member 12 is attached to the wall 2a and positioned within the internal space of the chamber 2. The mounting surface 12a is a plane that extends perpendicular to the X-axis direction. As a result, the substrate 11 is placed on the mounting surface 12a so as to be perpendicular to the X-axis direction and parallel to the ZY plane. The connecting member 13 is a member that electrically connects the mounting member 12 and the voltage application section 8. The connecting member 13 extends through the wall 2a to the outside of the chamber 2. The mounting member 12 and the connecting member 13 are insulated from the chamber 2.

[0021] In this embodiment, an insulating material may be used as the substrate 11 to be irradiated with negative ions. Examples of insulating substrates 11 include glass substrates, fine ceramics such as SiO2, SiON, AlN, Al2O3, and Si3N4, phenolic resins, epoxy resins, polyimide resins, resin-containing substrates such as Teflon® and fluororesins, polyimide, and flexible substrate materials such as PET. In addition, metal plates, conductive substrates, and semiconductors can also be used as the substrate 11.

[0022] Next, the configuration of the negative ion generation unit 4 will be described in detail. The negative ion generation unit 4 generates plasma and electrons within the chamber 2, thereby generating negative ions and radicals. The negative ion generation unit 4 includes a plasma gun 14 and an anode 16.

[0023] The plasma gun 14 is, for example, a pressure gradient type plasma gun, and its main body is provided on the wall 2c of the chamber 2 and connected to the internal space of the chamber 2. The plasma gun 14 has a gas supply unit (not shown) and supplies noble gases such as Ar and He to generate 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 the plasma port into the internal space of the chamber 2. As a result, plasma P is generated in the internal space of the chamber 2.

[0024] 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 guiding the plasma P. The anode 16 is provided on the wall portion 2d of the chamber and is positioned opposite the plasma gun 14 in the Y-axis direction. As a result, the plasma P is emitted from the plasma gun 14, spreads out in the internal space of the chamber 2 while moving toward the positive side in the Y-axis direction, and then converges and is guided to the anode 16. Note that the positional relationship between the plasma gun 14 and the anode 16 is not limited to the above, and any positional relationship may be adopted as long as negative ions can be generated.

[0025] The gas supply unit 6 is located outside the chamber 2. The gas supply unit 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 between the negative ion generation unit 4 and the object placement unit 3. Here, the gas supply port 26 is formed between the negative end of the wall portion 2d 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 unit 6 supplies a gas that serves as the raw material for negative ions. For example, O - O2 and NH4 are the raw materials for negative ions. - NH2, NH4, and others are used as raw materials for negative ions of nitrides such as C - Ya Si - C2H6 and SiH4, which are used as raw materials for negative ions, are employed. Note that the gas also includes noble gases such as Ar.

[0026] The circuit section 7 includes 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 applies a negative voltage to the cathode 21 and a positive voltage to the anode 16 of the plasma gun 14, with the chamber 2, which is at ground potential, in between. This generates a potential difference between the cathode 21 and anode 16 of the plasma gun 14. The first wiring 31 electrically connects the cathode 21 of the plasma gun 14 to the negative potential side of the variable power supply 30. The second wiring 32 electrically connects the anode 16 to the positive potential side of the variable power supply 30. Resistor R1 is connected in series between the first intermediate electrode 22 and the variable power supply 30. Resistor R2 is connected in series between the second intermediate electrode 23 and the variable power supply 30. Resistor R3 is connected in series between the chamber 2 and the variable power supply 30. Switch SW1 is switched between ON and OFF states by receiving a command signal from the control unit 50. Switch SW1 is connected in parallel with resistor R2. Switch SW1 is in the OFF state when generating plasma P. On the other hand, switch SW1 is in the ON state when stopping plasma P.

[0027] The voltage application unit 8 applies a bias voltage to the substrate 11. The voltage application unit 8 includes a power supply 36 for applying a bias voltage to the substrate 11, a third wiring 37 connecting the power supply 36 and the object placement unit 3, and a switch SW2 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 connecting member 13. As a result, the third wiring 37 electrically connects the power supply 36 and the substrate 11 via the connecting member 13 and the mounting member 12. The ON / OFF state of the switch SW2 is switched by the control unit 50. The switch SW2 is turned ON at a predetermined timing when negative ions are generated. When the switch SW2 is turned ON, the connecting member 13 and the positive potential side of the power supply 36 are electrically connected to each other, and a bias voltage is applied to the connecting member 13. On the other hand, switch SW2 is turned OFF at a predetermined timing during negative ion generation. When switch SW2 is turned OFF, the connecting member 13 and the power supply 36 are electrically disconnected from each other, no bias voltage is applied to the connecting member 13, and the connecting member 13 becomes floating. The more detailed configuration of the voltage application unit 8 will be described later.

[0028] The control unit 50 is a device that controls the entire negative ion generator 1 and is equipped with an ECU (Electronic Control Unit) that comprehensively manages the entire device. The ECU is an electronic control unit that has a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), CAN (Controller Area Network) communication circuit, etc. In the ECU, for example, various functions are realized by loading a program stored in ROM into RAM and executing the program loaded in RAM with the CPU. The ECU may be composed of multiple electronic units.

[0029] The control unit 50 is located outside the chamber 2. The control unit 50 includes a gas supply control unit 51 that controls the gas supply by the gas supply unit 6, a plasma control unit 52 that controls the generation of plasma P by the negative ion generation unit 4, and a voltage control unit 53 that controls the application of bias voltage by the voltage application unit 8. The control unit 50 controls the system to perform intermittent operation, repeatedly generating and stopping plasma P.

[0030] When switch SW1 is OFF, controlled by the plasma control unit 52, plasma P is emitted from the plasma gun 14 into the chamber 2, thus generating plasma P within the chamber 2. Plasma P consists of neutral particles, positive ions, negative ions (if a negative gas such as oxygen gas is present), and electrons. When switch SW1 is ON, controlled by the plasma control unit 52, plasma P is not emitted from the plasma gun 14 into the chamber 2, causing a rapid decrease in the electron temperature of the plasma P within the chamber 2. As a result, electrons are more easily attached to the gas particles supplied into the chamber 2. This efficiently generates negative ions in the generation chamber 10b. The voltage control unit 53 controls the voltage application unit 8 to apply a positive bias voltage to the substrate 11 when the plasma P is stopped. This guides negative ions in the chamber 2 to the substrate 11, and the negative ions irradiate the substrate 11.

[0031] Figure 2 is a graph showing the ON / OFF timing of plasma P and the arrival of positive and negative ions on the target object. In the figure, the region labeled "ON" indicates the generation state of plasma P, and the region labeled "OFF" indicates the stopped state of plasma P. Plasma P is stopped at time t1. During plasma P generation, many positive ions are generated. At this time, many electrons are also generated in chamber 2. When plasma P is stopped, the number of positive ions decreases rapidly. At this time, the number of electrons also decreases. Negative ions increase rapidly from time t2, a predetermined time after plasma P has stopped, and peak at time t3. Note that both positive ions and electrons decrease after plasma P stops, and around time t3, the amount of positive ions becomes equal to the amount of negative ions, and there are almost no electrons left.

[0032] Here, as shown in Figure 1, the negative ion generator 1 includes a detection unit 40 for detecting the generation and disappearance of plasma P. The detection unit 40 has a photodetector element 41 and a plasma monitoring unit 54 of the control unit 50.

[0033] The photodetector element 41 is an element that detects the amount of light in the chamber 2. For the photodetector element 41, a photodiode with low delay is preferable, but if there is a delay in the circuit for amplifying the photodiode signal, a phototransistor, which is an optical element with a built-in amplifier, may be used. When a photodiode is used as the photodetector element 41, it has the characteristic of low delay to light, but the resulting signal strength is low. When a combination of a photodiode and an amplifier is used as the photodetector element 41, the photodiode signal can be amplified by the amplifier. When a phototransistor is used as the photodetector element 41, a delay occurs due to amplification, but it has the advantage of high signal strength. The response speed is fastest with a photodiode alone, and approximately the same for the "photodiode + amplifier" and phototransistor combinations. The signal strength is weakest with a photodiode alone, and approximately the same for the "photodiode + amplifier" and phototransistor combinations.

[0034] The photodetector 41 is mounted on the viewport 42 of the chamber 2. The viewport 42 is a viewing window formed in the wall of the chamber 2, allowing the interior of the chamber 2 to be visually inspected from the outside. The viewport 42 has a light-transmitting member provided in the wall of the chamber 2. The photodetector 41 is located outside the chamber 2 and detects the amount of light inside the chamber 2 through the light-transmitting member of the viewport 42. The photodetector 41 transmits the detected signal to the control unit 50.

[0035] The plasma monitoring unit 54 of the control unit 50 monitors the plasma P in the chamber 2 based on the signal detected by the photodetector 41. The plasma monitoring unit 54 detects that plasma P is being generated in the chamber 2 when the amount of light detected by the photodetector 41 is above a predetermined value. The plasma monitoring unit 54 detects that the plasma P has disappeared in the chamber 2 when the amount of light detected by the photodetector 41 decreases and falls below a predetermined threshold.

[0036] For example, Figure 3 shows the time change of the voltage V of the anode 16 and the time change of the detection signal, i.e., the light intensity PT, detected by the photodetector element 41. As shown in Figure 3, the light intensity PT decreases sharply at the moment the plasma control unit 52 turns off the plasma P. The plasma monitoring unit 54 detects that the plasma P has disappeared when the light intensity PT falls below a predetermined threshold TH. The voltage control unit 53 controls the plasma control unit 52 to stop the plasma P, and after the plasma monitoring unit 54 detects the disappearance of the plasma P, it controls the voltage application unit 8 to apply a positive bias voltage to the substrate 11. As a result, negative ions are guided to the substrate 11 in the chamber 2 after the plasma P has disappeared, and the substrate 11 is irradiated with negative ions. For example, the voltage control unit 53 applies the bias voltage at a time domain E1 (see Figure 2) when the plasma P is OFF and there are many negative ions in the chamber.

[0037] Furthermore, the plasma monitoring unit 54 stops the negative ion generator 1 based on the detection results of the detection unit 40. For example, if the plasma monitoring unit 54 cannot detect the disappearance of plasma P even after a predetermined time has elapsed since the plasma control unit 52 turned off plasma P, it stops the negative ion generator 4.

[0038] Next, the operation and effects of the negative ion generator 1 according to this embodiment will be described.

[0039] The negative ion generator 1 according to this embodiment includes a negative ion generation unit 4 that generates negative ions by generating plasma P in a chamber 2. Therefore, after the negative ion generation unit 4 stops generating plasma P, it becomes possible to irradiate the substrate 11 with negative ions. The negative ion generator 1 also includes a detection unit 40 that detects the generation and disappearance of plasma P. Therefore, the negative ion generator 1 can irradiate the substrate 11 with negative ions after the detection unit 40 confirms the disappearance of plasma P. This allows for negative ion irradiation at an appropriate timing. Thus, the substrate 11 can be irradiated with negative ions at an appropriate timing.

[0040] For example, if the voltage control unit 53 applies a bias voltage to the substrate 11 when the plasma P is not actually turned OFF, malfunctions such as damage to the substrate 11 or failure of the device may occur. An example of a malfunction that occurs when a bias voltage is applied while the plasma P is ON will be explained with reference to Figure 4. Figure 4(a) is a graph showing the time change of negative ion density etc. when a low bias voltage is applied, and Figure 4(b) is a graph showing the time change of negative ion density etc. when a high bias voltage is applied. Here, we assume that the bias voltage is applied from time t0 when the plasma is OFF. Time t0 is determined by the charge balance and becomes larger when there are many electrons. In other words, when the bias is high compared to when the bias is low, residual electrons are temporarily collected, so the rise of the negative ion flux is delayed accordingly. If a high bias voltage is applied at the timing of low bias, a large current will flow because there are more electrons. The same thing happens with the discharge current, and on the high current side, time t0 becomes larger, and the peak after the rise at low current (low bias) disappears, resulting in a flat negative ion flux. As shown in Figure 4(c), at high bias, the mode is CC at Δt, and then it switches to CV mode.

[0041] Depending on the bias, if too many electrons are collected or too much negative ion current flows, the bias power supply may switch from CV mode to CC mode. If a bias voltage is applied when the plasma is ON, the current limiting mechanism on the power supply side will activate, causing it to switch to CC mode, and the voltage application may change even more than what is shown in Figure 4. The problem in this case is that the protection circuit will activate and the voltage cannot be applied at a constant level, resulting in uneven negative ion irradiation. Also, if too much current flows through the bias power supply and it switches to CC mode without applying voltage, even if the power supply can withstand it to some extent, the bias power supply output switch may be damaged.

[0042] In contrast, the negative ion generator 1 can apply a bias voltage only after confirming that the plasma P has disappeared, thus enabling negative ion irradiation at the appropriate timing without the aforementioned problems occurring. Therefore, negative ions can be irradiated onto the substrate 11 at the appropriate timing.

[0043] The detection unit 40 may have a photodetector 41 that detects the amount of light inside the chamber 2. When plasma P is generated, plasma light is always generated, and as the plasma P disappears, the amount of light decreases. Therefore, the detection unit 40 can accurately detect the disappearance of plasma P by monitoring the plasma light with the photodetector 41.

[0044] The photodetector 41 may be mounted on the viewport 42 of the chamber 2. In this case, the photodetector 41 can detect the disappearance of the plasma P from outside the chamber 2. Therefore, the photodetector 41 can be easily incorporated into the device. For example, by attaching the photodetector 41 to the viewport 42 of an existing negative ion generator 1 and inputting the signal to the control unit 50, the detection unit 40 can be easily added later.

[0045] The negative ion generator 1 may stop operating based on the detection result of the detection unit 40. In this case, if the disappearance of plasma P is not detected despite the plasma OFF control being performed, the device may be considered to have a malfunction and its operation may be stopped. This allows maintenance to be performed after the operation has stopped.

[0046] The present invention is not limited to the embodiments described above.

[0047] For example, in the above-described embodiment, the photodetector 41 was provided in the viewport 42, but the position of the photodetector 41 is not particularly limited. For example, the photodetector 41 may be provided inside the chamber 2. Also, the position of the viewport 42 is not limited as long as it is a position from which plasma light can be seen. The same applies to the position of the photodetector 41.

[0048] In the above-described embodiment, the detection unit 40 used a photodetector 41, but it is not necessary to use a photodetector 41. For example, the detection unit 40 may detect the voltage at a predetermined location within the negative ion generator 1. In this case, it is possible to detect the disappearance of plasma P without adding a photodetector 41 or the like. However, the detection unit 40 may use both the photodetector 41 and voltage detection, in which case the disappearance of plasma P can be detected more accurately.

[0049] As shown in Figures 5(a) and 5(b), the voltage at each part of the negative ion generator 1 changes at the timing when the plasma is turned ON to OFF. Although the negative ion generator 1 shown in Figure 1 does not have a main hearth and a ring hearth, it may have a main hearth that holds such materials and guides the plasma, and a ring hearth provided around the main hearth.

[0050] The detection unit 40 may perform detection based on the voltage of the main hearth (anode). If the voltage of the main hearth drops, for example, from around +25V to +10V, the threshold should be set between these voltages (for example, +20V). The detection unit 40 may detect the disappearance of plasma P when it detects a plasma OFF signal and the voltage value falls below the threshold.

[0051] The detection unit 40 may perform detection based on the voltage of the second intermediate electrode 23. If the voltage of the second intermediate electrode 23 rises, for example, from around -5V to around +10V, the threshold should be set between these voltages (for example, 0V). The detection unit 40 may detect the disappearance of the plasma P upon detecting a plasma OFF signal and confirming that the voltage value is above the threshold.

[0052] The detection unit 40 may perform detection based on the voltage of the ring hearth. The voltage of the ring hearth fluctuates little, but a negative peak is observed when the plasma is OFF and a positive peak is observed when the plasma is ON. The detection unit 40 may perform detection based on these fluctuations.

[0053] The detection unit 40 may perform detection based on the voltage of the cathode 21. The cathode 21 is basically a negative voltage, and the absolute value of the voltage is smaller when the plasma is OFF than when the plasma is ON. For example, the detection unit 40 may detect the disappearance of the plasma P when the voltage approaches 0V from -30V.

[0054] Since plasma P is introduced / de-introduced by short-circuiting the anode 16 and cathode 21, the potential between the two electrodes becomes approximately 0 when plasma is not introduced, as shown in the graph in Figure 6 (see A). Therefore, the detection unit 40 may detect the disappearance of plasma P when the voltage becomes 0V.

[0055] The detection unit 40 may also perform detection based on the temperature of the wall portion of the chamber 2, which is heated when the plasma is turned ON and cooled when the plasma is turned OFF.

[0056] Furthermore, the detection unit 40 may detect the pressure inside the chamber 2. In this case, it is possible to detect the disappearance of plasma P using an existing pressure gauge or the like without adding a photodetector 41 or the like. However, the detection unit 40 may use both the photodetector 41 and pressure detection, in which case the disappearance of plasma P can be detected more accurately.

[0057] Chamber 2 is heated when the plasma is ON, so the pressure increases, and when the plasma is OFF, the pressure decreases. The detection unit 40 may detect the pressure using, for example, a diaphragm pressure gauge with good responsiveness. Alternatively, although ionization vacuum gauges are usually installed with a wire mesh to prevent electrons and ions from the plasma P from entering, or connected via elbow piping, the pressure may be detected by intentionally omitting these measures. Since the ionization vacuum gauge ionizes residual gas and observes the current value, if electrons and ions flow in, it will judge that a large amount of residual gas has been ionized, resulting in a high pressure reading. The detection unit 40 can detect the disappearance of plasma P by utilizing this property of the ionization vacuum gauge.

[0058] For example, in the above embodiment, the plasma gun 14 was a pressure gradient type plasma gun, but the plasma gun 14 is not limited to a pressure gradient type as long as it can generate plasma in the chamber 2.

[0059] Furthermore, in the above embodiment, only one set of plasma gun 14 and anode 16 for guiding plasma P was provided in the chamber 2, but multiple sets may be provided. Also, plasma P may be supplied to a single location from multiple plasma guns 14. [Explanation of Symbols]

[0060] 1...Negative ion generator, 2...Chamber, 4...Negative ion generation unit, 11...Substrate (object), 40...Detection unit, 41...Photodetector element, 42...Viewport.

Claims

1. A negative ion generating device that generates negative ions and irradiates an object with them, A chamber in which the negative ions are generated internally, A negative ion generation unit generates negative ions by generating plasma in the chamber, The system includes a detection unit that detects the generation and disappearance of the plasma by the amount of light, After the detection unit detects the disappearance of the electron-containing plasma, an electric field is generated in the chamber to guide the negative ions to the object. A negative ion generator that stops operating based on the detection result of the aforementioned detection unit.

2. The negative ion generating apparatus according to claim 1, wherein the detection unit has a photodetector element for detecting the amount of light in the chamber.

3. The negative ion generating apparatus according to claim 2, wherein the photodetector is mounted on the viewport of the chamber.

4. The negative ion generator according to any one of claims 1 to 3, wherein the detection unit detects the voltage at a predetermined location within the negative ion generator.

5. The detection unit detects the pressure inside the chamber, as described in any one of claims 1 to 4.

6. A method of generating negative ions and irradiating an object with them, A negative ion generation step involves generating plasma in a chamber to generate the negative ions, A detection step for detecting the generation and disappearance of the plasma by the amount of light, The detection step includes, after the disappearance of the electron-containing plasma is detected, an electric field generation step of generating an electric field in the chamber to guide the negative ions to the object, A method for stopping operation based on the detection result of the aforementioned detection step.

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