JP2556549B2 - DC high voltage generator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a DC high voltage generator used in a charged particle beam device or the like, and particularly based on a signal obtained by detecting a beam current or an emission current of a charged particle beam. And a DC high voltage generator for controlling the output voltage of the high voltage generating circuit.

2. Description of the Related Art Conventionally, in a charged particle beam device such as a focused ion beam device, a device for stabilizing a charged particle beam emitted from a charged particle beam generation source has a high DC voltage as shown in FIG. A voltage generator is used.

In FIG. 2, 1 is an acceleration voltage generation circuit, 2 is an emitter, 3 is an extraction voltage generation circuit, 4 is an extraction electrode, 5
Is an ion beam, 6 is a beam current detector, 7 is a detection signal amplifier, 8 is an error amplifier, 9 is a reference signal setting device, and 10 is a Zener diode.

The high voltage generated by the acceleration voltage generating circuit 1 is applied to the emitter 2. An ion beam 5 is extracted from the tip of the emitter 2 by applying a voltage generated by the extraction voltage generation circuit 3 (hereinafter simply referred to as a voltage generation circuit) between the emitter 2 and the extraction electrode 4. Then, the beam current detected by the beam current detector 6 arranged in the path of the ion beam 5 or the emission current detected through the current detection resistor Rd is changed over to the switch S.
And is supplied to the error amplifier 8. The error amplifier 8 compares the detected signal with the target value of the beam current or emission current set by the reference signal setting device 9. Then, the output signal obtained by the error amplifier 8 is supplied to the voltage generating circuit 3 as a control signal to control the high voltage value generated by the voltage generating circuit 3, and the ion beam 5 emitted from the emitter 2 is controlled. The target value is stabilized.

[Problems to be Solved by the Invention] In the apparatus having such a configuration, when the beam current is not normally detected due to a failure of the detector, or the detected emission current or beam current is supplied to the error amplifier 8 due to disconnection or the like. If not, the output signal of the error amplifier 8 continues to increase. Therefore, the voltage generation circuit 3 controlled by the output signal runs out of control and operates so as to increase the voltage value up to the maximum value, and the semiconductor amplifier, the extraction electrode 4, etc. constituting the voltage generation circuit 3 are operated. May be destroyed. Therefore, as shown in FIG.
A Zener diode is provided between the error amplifier 8 and the voltage generating circuit 3 in order to limit the voltage value generated by the voltage generating circuit 3.
10 are provided. As a result, even if the output signal of the error amplifier 8 increases excessively, the output signal of the error amplifier 8 is limited according to the breakdown voltage value of the Zener diode 10, so that the voltage value generated by the voltage generation circuit 3 is reduced. Can also be provided with a limiting voltage.

However, this zener diode has a limited breakdown voltage value and its operating point is unstable, so that the output signal of the error amplifier 8 cannot be limited to an arbitrary value. Therefore, there is a problem that the voltage value generated by the voltage generating circuit 3 cannot be limited to an arbitrary value.

The present invention provides a comparator for comparing a high voltage proportional signal proportional to the output of the high voltage generating circuit and a second reference signal defining a high voltage limit value, and the output signal of the comparator is output from the error amplifier. It is an object of the present invention to provide a DC voltage generator that overcomes the above-mentioned problems by combining the above with the above, and limiting the output signal of the error amplifier so as not to exceed an arbitrary value.

[Means for Solving the Problems] The present invention detects a beam current or an emission current of a charged particle beam emitted from a charged particle beam generation source, supplies the detection signal to an error amplifier, and compares it with a reference signal. In a direct current high voltage generator that controls and stabilizes a high voltage generating circuit that supplies a voltage to an extraction electrode based on an output signal of an error amplifier, a high voltage proportional to the output of the high voltage generating circuit. Second to define signal and high voltage limits
A comparator for comparing the high voltage proportional signal to the high voltage limit value, and outputs a signal for controlling the high voltage generation circuit from the comparator when the high voltage proportional signal exceeds the high voltage limit value. The output of the high voltage generating circuit is prevented from exceeding the limit value by combining with the output signal of the error amplifier.

[Operation] According to the present invention, a comparator for comparing a high-voltage proportional signal proportional to the output of the high-voltage generating circuit with a second reference signal defining a high-voltage limit value is provided, and the high-voltage proportional signal is high-voltage limited. The comparator outputs a signal for controlling the high-voltage generating circuit when the output voltage exceeds the value, and combines the output signal of the comparator with the output signal of the error amplifier to limit the output of the high-voltage generating circuit. I try not to exceed the value.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram for explaining one embodiment of the present invention. In FIG. 1, the same components as those in FIG. 2 are designated by the same reference numerals.

The embodiment shown in FIG. 1 differs from the conventional example in that a limit value setting circuit for setting a limit value of the output of the voltage generating circuit and a high voltage proportional signal proportional to the output signal of the circuit and the output of the voltage generating circuit. A comparison amplifier (differential amplifier) for comparing
The output signal of the comparison amplifier is supplied between the error amplifier and the high voltage generating circuit via a diode.

In FIG. 1, the voltage value generated by the voltage generating circuit 3 is changed by the control voltage supplied to the circuit. For example, the variable range of the output voltage of this voltage generation circuit 3 is from 0V to 20V.
In the case of KV, the output voltage of the circuit 3 is controlled by the output signal voltage obtained by the error amplifier 8, for example, a linear voltage change from 0V to 20V. The beam current detected by the beam current detector 6 is supplied to the error amplifier 8 and compared with the target value of the beam current set by the reference signal setter 9. Then, the output signal voltage obtained by the error amplifier 8 is supplied to the extraction voltage generating circuit 3 as a control voltage. For example, when the output signal voltage of the error amplifier 8 is 15V, the output voltage of the voltage generating circuit 3 is as high as 15KV. A voltage is applied to the extraction electrode. Further, a high voltage proportional signal proportional to the voltage value detected via the voltage detection resistor R _V is supplied to the comparison amplifier 11 and compared with the limit value set in the limit value setting circuit 12. Where the comparison amplifier
11 is the error amplifier 8 when the high voltage proportional signal is below the limit value.
A voltage higher than the output voltage is output to make the diode 13 in a non-conductive state. Then, when the high-voltage proportional signal increases above the limit value, a voltage lower than the output voltage of the error amplifier 8 is output to turn on the diode 13, and the output signal of the error amplifier 8 is combined with the output signal of the comparison amplifier 11. By doing so, the control voltage supplied to the high voltage generation circuit 3 is prevented from exceeding the limit value.

[Effect of the Invention] As is apparent from the above description, according to the present invention, the comparison for comparing the high-voltage proportional signal proportional to the output of the high-voltage generating circuit with the second reference signal defining the high-voltage limit value. A comparator for outputting a signal for controlling the high voltage generation circuit from the comparator when the high voltage proportional signal exceeds the high voltage limit value, and synthesizing the output signal of the comparator with the output signal of the error amplifier. By doing so, the output of the high voltage generating circuit is prevented from exceeding the limit value. Therefore, it is possible to set the limit of the high voltage value output from the voltage generation circuit to an arbitrary value and limit it.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram for explaining an embodiment of the present invention, and FIG. 2 is a diagram for explaining a conventional example. 1: Acceleration voltage generation circuit, 2: Emitter 3: Voltage generation circuit, 4: Extraction electrode 5: Ion beam, 6: Beam current detector 7: Detection signal amplifier, 8: Error amplifier 9: Reference signal setting device, 11: Comparative amplifier 12: Limit value setting circuit, 13: Diode

Claims (1)

(57) [Claims] 1. A beam current or an emission current of a charged particle beam emitted from a charged particle beam source is detected, the detected signal is supplied to an error amplifier and compared with a reference signal, and based on an output signal of the error amplifier. In a DC high-voltage generator that controls and stabilizes a high-voltage generating circuit that supplies a voltage to a lead-out electrode, a high-voltage proportional signal proportional to the output of the high-voltage generating circuit and a high-voltage limit value are specified. Second
A comparator for comparing the high voltage proportional signal to the high voltage limit value, and outputs a signal for controlling the high voltage generation circuit from the comparator when the high voltage proportional signal exceeds the high voltage limit value. A DC high voltage generator characterized in that the output of the high voltage generating circuit is prevented from exceeding a limit value by combining with the output signal of the error amplifier.