JPS5867869A - Controlling means for ion source - Google Patents

Abstract

PURPOSE:To project the improvement in operatability such as adjusting the maximum dose of ion beams and the inhibition of misoperation, by operating an indicating lamp when the detected value of voltage of a drawing-out accelerating source is above predetermined reference voltage, and reducing the output of a magnetron or the intensity of a magnetic field. CONSTITUTION:AC voltage to be inputted to a drawing-out accelerating power source 21 is inputted through a rectifying circuit 23 and a filter 24 to a transformer 25. Differential voltage between an output voltage-setting instrument 31 and detected voltage is inputted to an oscillator 26, a high-frequency signal corresponding to the differential voltage is outputted from the oscillator 26, and input voltage to the transformer 25 is transduced into high frequency. The AC high voltage is then changed into DC high voltage by passing it through a rectifying circuit 27 and a filter 28 and charged to the accelerating electrode 20 of an ion source. An output current from the power source 21 is hence detected by a resistor R2 and compared with reference voltage 33 by a comparator 32 through an amplifier 31. When the former becomes larger than the latter, a luminous diode 36 is lighted and at least one of outputs of a magnetron and a magnet coil 41 is automatically reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion source, and more particularly to a control device for an ion source used in an ion implanter, an ion etching device, and the like.

A microwave ion source shown in FIG. 1 has been known as this type of ion source.

As shown, magnetron 1 that generates microwaves
is attached to the cylindrical end of a cylindrical accelerating electrode 4 via a waveguide 2 and a choke flange 3 made of a cylindrical insulating material. The other end of the accelerating electrode 4 is closed by a flat plate 4A, and a slit is bored in the center of the flat plate. Further, an ionization chamber 5 is formed by the flat plate 4A and a partition plate 4B provided inside the cylindrical portion and having an opening in the center. A sample gas introduction tube 6 is connected to the ionization chamber 5 . The accelerating electrode 4 is supported and fixed to one end of the cylindrical insulator 7 via a support material so that the ionization chamber 5 is inserted into the cylindrical insulator 7. The other end of the cylindrical insulator 7 is connected to an analysis tube section 8.

The ground electrode 9 and the deceleration electrode 10 are formed of a flat plate, with a slit bored in the center. The ground electrode 9 and the deceleration electrode 10 are fixed with an insulating material at a predetermined distance from each other, and are arranged so as to face the end surface of the acceleration electrode 4 in which the slit is provided and to align the axes of the slit. There is. The earth electrode 9 is supported and fixed to the analysis tube section 8. A magnet coil 11 is provided on the outer periphery of the cylindrical insulator 7.The analysis tube section 8 is also connected to an ion implanter or an ion etching device (not shown). An ion beam detector 12 is provided in the ion implanter, ion etching device, and the like.

A magnetron power supply 13 is connected to the magnetron 1, an extraction acceleration power supply 14 is connected to the acceleration electrode 4, a magnetic field generation power supply 15 is connected to the magnet coil 11, and the other ends of these power supplies are grounded. The earth electrode 9 is grounded via the analysis tube section 8.

The operation will be explained below.

The microwave output generated by the magnetron 1 is introduced into the ionization chamber 5 through the waveguide 2 and the choke flange 3, and then when the sample gas is injected into the ionization chamber 5 through the sample gas introduction pipe 6, the magnetron The magnetic field generated by the coil 11 causes cyclotron resonance, and the gas is turned into plasma and becomes plasma ions. The plasma ions are pulled out of the ionization chamber 5 by the electric field formed between the acceleration electrode 4 and the earth electrode 9, are accelerated, pass through the slits of the deceleration electrode 10 and the earth electrode 9, become an ion beam, and are output to the analysis tube section 8. be done.

In the case of an ion implanter, etc., the ion beam of the desired gas is selectively separated from the ion beam introduced into the analysis tube section and supplied to the ion implantation system.The amount of the ion beam is determined by beam detection. is detected by the meter 12, and the meter (M
l).

The beam current flowing into the beam detector returns to the extraction accelerating power source 14 via a grounding circuit. In addition, ions other than those of the desired gas are returned to the extraction region J power supply 14 from the pipe wall of the analysis system, etc., through the ground circuit. That is, the total amount of ion beam output from the ion source is
4, and is displayed on a meter (M2) provided within the power supply 14. The ratio of the total ion beam amount to the ion beam amount of the desired gas is determined by the amount of the desired gas,
Depends on the type of on. For example, in the actual measurement example, id,
When trying to obtain P ions using PHIl gas,
Approximately 1/3 of the total ion beam amount was detected by the beam detector as door ions.

To extract the maximum amount of ion beam from the ion source.

While monitoring the meter (M□), it is necessary to adjust the magnetron pressure, magnetic field strength, sample gas flow rate, etc. to the optimum values. At this time, be especially careful not to dissipate the plasma. Therefore,
While monitoring the plasma condition with a meter (M,),
The above-mentioned adjustment has to be made while simultaneously looking at two meters, which is an extremely complicated operation and can lead to erroneous operation. In particular, devices such as ion implanters are large-sized, and the extraction acceleration power source is often installed separately.In such cases, the above-mentioned adjustment operation becomes even more difficult.

Additionally, although a strong microwave output and strong magnetic field are generally required to ignite plasma, once the plasma has been ignited, it is necessary to continue generating plasma even if the microwave output or magnetic field strength is reduced to approximately 1/2. can be done.

Therefore, conventionally, after confirming the generation of plasma using a meter (M), an operation is performed to reduce the magnetron output and/or the magnetic field strength.

However, as described above, if the meter (M) is located far from the magnetron or the magnetic field generating power source, the operation is difficult, as is the case with the adjustment of the maximum ion beam amount described above.

An object of the present invention is to provide an ion source control device that can improve operability in adjusting the maximum ion beam amount and prevent erroneous operations.

The present invention detects the output current of the extraction acceleration power source.

By comparing the detected current value and a predetermined reference current value, and operating an indicator light when the detected current value is equal to or higher than the reference voltage, and automatically reducing at least one of the magnetron output and the magnetic field strength. This is intended to improve operability in adjusting the maximum ion beam amount, etc., and to prevent erroneous operations.

The present invention will be explained below based on illustrated embodiments.

FIG. 2 shows a circuit diagram of an extraction acceleration power source and a magnetic field generation power source of an ion source to which the present invention is applied.

An AC input power source is connected to the extraction acceleration power source 21 via a switch 22 to a rectifier circuit 23 . The rectifier circuit 23 is connected to a transformer 25 via a filter 24.
The output of an oscillator 26 is input to the transformer 25, and the output end of the transformer 25 is connected to a filter 28 via a rectifier circuit 27. One of the output ends of the filter 28 is connected directly to the output ends 29A and 2913 of the extraction acceleration power source 21, and the other is connected to the output ends 29A and 2913 of the extraction acceleration power source 21, respectively, through an output current detection resistor R□. The output end 29A is connected to the accelerating electrode 20, and the output end 29B is grounded.

The output voltage detection resistor R9 is connected between the positive and negative output terminals of the filter 28, and the intermediate terminal of the resistor R2 is connected to the input terminal of the amplifier 30 via the resistor R11. A reference voltage from the output voltage setter 31 is inputted to this input terminal via a resistor R4, and the output of the amplifier 30 is fed back via a resistor R.

The other input terminal of the amplifier 30 is grounded via a resistor R6. The output of the amplifier 30 is input to the oscillator 26.

The input terminal of the amplifier 31 is connected to the anti-ground side of the output current detection resistor R0 via a resistor R7.

The other input terminal of the amplifier 31 is grounded via a resistor R8, and is also connected to the output terminal of the amplifier 31 via a resistor 1 and the like. The output terminal of the amplifier 31 is a resistor. is connected to the input terminal of the comparator 32 via a diode D connected in the forward direction and a resistor 1 (
□Connected to the output terminal of the comparator 32 by a 1Q series circuit. Above diode I)1 and resistor R1□
The connection point of is connected to the control power supply ■ through the resistor ■ (.12).

The other input terminal of the comparator 32 is a reference voltage source 33,
It is also connected to the output terminal of the comparator 32 via a resistor R18. The output terminal of the comparator 32 is connected to the input terminal of the amplifier 34, 35 through a resistor R. The input terminal of the amplifier 3435 is connected to the control power supply V through a forward-connected diode I),
It is also grounded via a diode D8 connected in the opposite direction. The output terminal of the amplifier 34 is connected to the cathode of a light emitting diode 36 provided at an arbitrary location, and the anode of the light emitting diode is connected to the control power supply V.

It is connected to the.

On the other hand, the magnetic field generation' power source 37 has 9. A power source is connected to a rectifier circuit 39 via a switch 38.

The rectifier circuit 39 is connected to a filter 40.

One output end of the filter 40 is connected to a magnet coil 41, and the other output end is connected to the magnet coil 41 via a transistor 42 and a current detection resistor &a. The connection point between the transistor 42 and the current detection resistor E3r, 5 is grounded. The anti-ground side of the current detection resistor R15 is connected to the input terminal of the amplifier 43 via a resistor R26. The input terminal is connected to the amplifier 4 via a resistor I (17).
3 and a movable terminal of an output current setting device 44 made of a variable resistor via a resistor 1%ts. The fixed resistance of the output current setting device 44 is a resistance)
tl.

The other end of the fixed resistor is grounded. Relay 4 in parallel with the above resistance) t119
No. 5 contact 45A is connected. The relay 45 is connected to the output terminal of the amplifier 35 in the extraction acceleration power supply 21 and the control/control terminal.
They are respectively connected to a power supply Vc. The amplifier 43
The other input terminal of is grounded via the resistor R2o,
The output terminal is connected to the base of the transistor 46 via a resistor R21. The emitter of the transistor 46 is grounded, and the collector is connected to the base of the transistor 42 and to the control power supply V via a resistor I (2□).

The operation will be explained below.

The father current pressure input to the extraction acceleration power supply 21 is transferred to the rectifier circuit 2.
3 and filter 24 and is then rectified and filtered and input to a transformer 25. At this time, the output 'voltage setting device 3
The difference voltage between the output layer pressure given from oscillator 1 and the detection voltage detected by output voltage detection resistor R2 is
6 is input. The oscillator 26 outputs a high frequency signal (20KH2) with a pulse width corresponding to the voltage difference, and converts the input voltage of the transformer 25 into a high frequency voltage. As a result, the transformer 25 outputs an AC high voltage according to the set voltage. The AC high voltage is current-filtered by a rectifier circuit 27 and a filter 28, outputted as a DC high voltage, and applied to the accelerating electrode 20 of the ion source. Plasma ions generated in an ionization chamber (not shown) are pulled out of the ionization chamber by applying a diurnal pressure to the high-velocity electrode, are further accelerated, and are outputted from the ion source as an ion beam. The ion beam output from the ion source is consumed during ion implantation, etc.
The output current of the extraction accelerating power source 21 corresponding to the output ion beam amount is connected to the ground circuit and output voltage detection resistor.

flows to When plasma ions are not ignited in the ionization chamber, no ion beam is output.
The output current becomes small.

Therefore, the presence or absence of plasma ion ignition can be detected based on the output current of the extraction acceleration power source. The output current is formed by an output current run-in resistor 2, and this detected voltage is amplified to a predetermined level by an amplifier 31 and input to a comparator 32.

A reference voltage 3'3 serving as a detection standard for the plasma ignition state is input to the comparator 32, and when the detection voltage exceeds the reference voltage, the comparator 32 outputs a plasma ignition signal.

Further, the comparator 32 has hysteresis characteristics, and has stable characteristics against minute fluctuations in the detection voltage. The plasma ignition signal is amplified by an amplifier 34, and a light emitting diode 36 is turned on by the amplified signal VC. On the other hand, when the detected voltage is lower than the reference voltage, the light emitting diode 36 is turned off. This allows the plasma ignition state in the ionization chamber to be perceived.

The AC power input to the magnetic field generating power supply 37 is still rectified and filtered by the rectifier circuit 39 and filter 40. The DC output voltage of the filter 40 is applied to the magnet coil 41 via a transistor 42 and a current detection resistor R15. At this time, the detected voltage detected by the current detection resistor and the set voltage given from the output current setter 44 are amplified by an amplification circuit formed from an amplifier 43, The output voltage causes the transistor 46 to operate. As a result, the voltage of the resistor R2□, that is, the base voltage of the transistor 42 is controlled, and an output current corresponding to the set current is caused to flow through the magnet coil 41. magnet coil 4
When a strong magnetic field is generated in the ionization chamber by 1, the microwave output introduced into the ionization chamber and the sample gas cause cyclotron resonance, and the sample gas is turned into plasma. The generated plasma is detected by the output current of the extraction accelerating power source 21 as described above, and the detection signal is amplified by the amplifier 35 to excite the relay 45. By energizing the relay 45,! llll contact 45A is closed, and the resistance R
19 is shorted. Thereby, the set voltage is switched to a value necessary to sustain the plasma, and the output current is reduced. Further, when the plasma disappears due to some reason, a disappearance signal is output from the heater 32,
The relay 45 is demagnetized by the operation of the amplifier 35, and the contact 45A is opened to enter the above-mentioned initial state. relay 4
By using a delay relay in 5, the above operation can be further stabilized.

Note that the set value of the output current of the magnetic field generating power supply is determined and set in advance through actual measurements or the like. According to a measurement example, it was necessary to flow a current of 40A to make the magnetic field strength 800 Gauss at the time of plasma ignition, but after ignition, even if the current was reduced to 2OA, the plasma ignition state could be maintained. was completed.

In addition, the magnetron is a magnetron′ not shown in the figure.
The magnetron output can be controlled by controlling the anode current of the magnetron by the set voltage output from the output equipment installed in the sleep source. Therefore, similarly to the magnetic field generating power supply described above, the magnetron output can be reduced by switching the set voltage of the magnetron output according to the plasma ignition signal. In this case as well, the set value of the microwave output is determined and set in advance by actual measurement or the like. According to an actual measurement example, a magnetron output of 300 mA is required at the time of plasma ignition, but even if the output was reduced to 150 mA after ignition, the plasma ignition state could be maintained.

Therefore, when adjusting the magnetron/output and magnetic field strength to draw the maximum ion beam of the desired gas from the ion source, the output current of the extraction power supply corresponding to the total amount of ion beam is The indicated meter (
M2), so the beam detector meter (
Since two meter readings, M, ) and the meter (M2), must be read at the same time, the adjustment operation of the front convexity is extremely complicated, and the plasma may disappear due to this operation. However, according to this example,
By lighting the light emitting diode when the output/current of the extraction accelerating power source exceeds a predetermined current value, the recommendation for plasma ignition can be perceived very easily and reliably, so when adjusting the maximum ion beam amount. This makes the operation extremely easy, and furthermore, it is possible to prevent erroneous operations.

In addition, conventionally, after plasma ignition, operations were performed to reduce the magnetic field strength or the direction of magnetron output while checking the plasma ignition state according to the instructions from the meter CM2), but according to the present example, the above-mentioned Since the operation is performed automatically, there is an effect that the operability is greatly improved.

Furthermore, since energy saving is achieved, the operating cost is reduced, and in addition, since the cutting edge is reduced, the service life of the cutting machine is promoted and the reliability is improved. be.

In this example, we have explained how to reduce either the magnetic field strength or the magnetron output after plasma ignition, but if the set value is set to an appropriate value, the magnetic field strength and the magnetron output can be reduced at the same time. It is also possible to do so, and the same effect as in the above embodiment can be obtained.

Second, according to the present invention, the state of plasma ignition can be perceived extremely easily and reliably using the indicator light, so operations such as adjusting the maximum ion beam amount are extremely easy, and erroneous operations can be avoided. This can be prevented.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional example, and FIG. 2 is a circuit diagram of an embodiment to which the present invention is applied. 20... Acceleration 'electrode, 21... Extraction Karo speed' power supply,
32... Comparator, 33... Reference voltage, 36.
...Light emitting diode (indicator light), 37...Magnetic field generation'
U1.41...Magnet coil, 44...Output current setting d145...Relay, R1°°°output current resistance.

Claims (1)

[Claims] 1. Apply microwaves to a sample gas introduced into an ionization chamber provided in a magnetic field to turn the sample gas into plasma, and connect an acceleration electrode and a ground electrode connected to an extraction acceleration power source. In the ion source that accelerates plasma gas in the ionization chamber by an electric field formed and outputs it as an ion beam, the detection circuit outputs a detection voltage according to the output current of the extraction acceleration power source; An ion source control device comprising: a comparator that performs comparison with a predetermined reference voltage; and an indicator light operated by an output signal of the comparator p. 2. The sample gas introduced into the ionization chamber provided in the magnetic field formed by the electromagnet is subjected to microwaves output from the magneto/ to turn the sample gas into plasma, and the sample gas is connected to the extraction accelerating power source. In an ion source that accelerates plasma gas in the ionization chamber and outputs it as an ion beam by an electric field formed by an accelerating electrode and a ground electrode, a detection circuit that outputs a detection voltage according to an output current of the extraction acceleration power source; A comparator for comparing the detected voltage with a predetermined reference voltage, an indicator light operated by the output signal of the comparator, and means for controlling at least one of the output of the electromagnet and the output of the magnetron by the output signal of the comparator. An ion source control device comprising: