JPH0628143B2 - Ion beam device - Google Patents

Description

The present invention relates to an ion beam apparatus for generating an ion beam and irradiating a material to be drawn with the ion beam.

[Prior Art] In an ion beam apparatus equipped with a gas phase ion source, a gas serving as an ion species is introduced in the vicinity of the tip of the emitter, and the gas is ionized by an electric field at the tip of the emitter to extract an ion beam. FIG. 4 shows a conventional example of such an ion beam apparatus. In the figure, 1 is an emitter of a gas phase ion source, 2 is an extraction electrode, and 3 is an ion beam current for detecting a current of emitted ions. Detector, 4 is a focusing lens, 5 is an objective lens, 6 is a material to be drawn, 7 is an accelerating power source, 8a is a drawing power source, 8b is a control circuit for controlling the output voltage of the drawing power source 8a, 9 is an amplifier, 10 Is a differential amplifier for performing negative feedback control, 11
Is a limit circuit, 12 is a summing amplifier, 13 is an emitter 1.
Ion beam current designation signal generation circuit for setting a target value of the amount of ion beam current emitted more, 1
Reference numeral 4 denotes an extraction voltage designation signal generating circuit for setting a target value of the extraction voltage. The limit circuit 11 is mainly composed of two Zener diodes connected in opposite polarities, and has an input / output characteristic as shown by the characteristic line (a) in FIG. That is, when the input signal X is −ΔX or more and + ΔX or more, the input signal value is linearly converted from −ΔY to + ΔX.
The signals Y up to Y are output, and when the input signal X is smaller than -ΔX, the signal of the value -ΔY is output, and when the input signal is larger than + ΔX, the signal of the value + ΔY is output.

Now, in the case of the gas phase ion source, the emitted ion beam current I has a maximum point with respect to the extraction voltage V, as shown by the characteristic line A or B in FIG. Since it is desired that the ion beam amount to be extracted is large, when the ion beam current amount close to the maximum value is to be extracted from the ion source, the designation signal is set as follows.
That is, for example, a signal for designating the ion beam current value I ₀ corresponding to the point P ₀ in FIG.
A signal corresponding to ₀ is generated by the extraction voltage designating signal generation circuit 14. Then, a signal obtained by amplifying the deviation between the output signal from the ion beam current detector 3 and the ion beam current designation signal from the ion beam current designation signal generation circuit 13 is output from the differential amplifier 10. This signal is converted by the limit circuit 11 according to the conversion characteristic and then sent to the summing amplifier 12. The output signal from the limit circuit 11 and the output signal from the extraction voltage designating signal generation circuit 14 are added in the addition amplifier 12, and the output signal of the addition amplifier 12 is sent to the control circuit 8b. It is controlled to generate an extraction voltage corresponding to P ₀ .

If the limit circuit 11 does not exist, the extraction voltage may shift to the right of the voltage Vp corresponding to the peak value Ip for some reason during the negative feedback control. In such cases,
In the negative feedback control system, it is determined that the extraction voltage is insufficient, and the extraction power source 8a applies the maximum value of the extraction voltage to the extraction electrode 2. Therefore, the negative feedback loop is broken by further decreasing the ion beam current. The limit circuit 11 is provided to solve such a problem. Since the range of the input signal to the summing amplifier 12 is limited by the limit circuit 11, the above situation does not occur, and the negative feedback loop is not generated. Does not come off.

[Problems to be Solved by the Invention] By the way, by predicting the characteristic indicated by B in FIG. 6, a signal corresponding to V ₀ in FIG. 6 is generated from the extraction voltage designation signal generation circuit 14, and the beam current designation signal is generated. Even if the signal corresponding to I ₀ in FIG. 6 is generated from the generation circuit 13, the characteristic that gives the relation between the ion beam current I and the extraction voltage V changes depending on the supply amount of ionized gas, the temperature near the emitter, and the like. To do. Therefore, when the actual characteristic is as shown by B in FIG. 6, the point on the characteristic curve where the ion current is I ₀ is within the control range (V
₀ + ΔV to V ₀ −ΔV), the amplifier 10
The desired current I ₀ cannot be realized even if a signal with more amplified deviation is sent to the control circuit 8b. Therefore, in the past,
In such a case, the output signal of the extraction voltage designating signal generating circuit 14 was readjusted by trial and error by manual operation, and the operation was complicated.

The present invention solves such a conventional drawback, and the voltage-current characteristic of the gas phase ion source deviates from the expected one. Therefore, depending on the initial setting of the extraction voltage and the ion beam current designation signal, desired ion An object of the present invention is to provide a device capable of automatically shifting the set value of the extraction voltage designating signal by an appropriate amount when the control for maintaining the beam current cannot be performed.

[Means for Solving Problems] Therefore, according to the present invention, an extraction power source for applying an extraction voltage between an emitter and an extraction electrode of a gas phase ion source, and an ion beam current amount generated from the emitter are detected. Detecting means, an amplifier for amplifying the deviation between the output signal from the detecting means and the signal representing the set value of the ion beam current amount, and the range of the output signal value of the amplifier is limited within a predetermined width. A limit circuit for outputting, an extraction voltage designation signal generation circuit for generating a signal for designating the output voltage of the extraction electrode, an output signal of the limit circuit and an output signal of the extraction voltage designation signal generation circuit And a circuit for detecting that the output signal of the amplifier deviates from the limit range of the limit circuit. A control circuit for automatically shifting the designation signal from the extraction voltage designation signal generating circuit based on the signal from the detection circuit so that the output signal of the amplifier does not deviate from the limited range of the limit circuit. It is characterized by that.

EXAMPLES Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention.
In the figure, the same components as those in FIG. 4 are designated by the same reference numerals.

In FIG. 1, 15 is a rotary encoder,
Reference numeral 16 is an up / down pulse generating circuit, 17 and 18 are OR circuits, 19 and 20 are AND circuits, 21 is an up / down counter, 22 is a DA converter, and the output signal of the DA converter 22 is the extraction voltage designating signal. It is sent to the summing amplifier 12. Reference numerals 23 and 24 are comparators, and the comparator 2
3 and 24 have first and second reference signal generators 25 and 2 respectively.
The reference signal is sent from 6. The output signals of the comparators 23 and 24 are sent to the first and second pulse generating circuits 27 and 28, respectively. These first and second pulse generation circuits 2
The output signals of 7 and 28 are sent to the AND circuits 19 and 20, respectively. A gate signal can be sent from the gate signal generating circuit 29 to the AND circuits 19 and 20.

In such a configuration, S in FIG. 5 is slightly smaller than the level ΔY in FIG. 5 from the first reference signal generator 25.
The generator 25 is adjusted so that the signal indicated by 1 is generated, and the level of FIG.
The generator 26 is adjusted so that the signal indicated by S2 in FIG.

Next, when the operator rotates the rotary encoder 15, the pulse from the encoder 15 is sent to the up-down counter 21, and the count value of the up-down counter 21 is increased or decreased. The output signal of the up / down counter 21 is D
It is converted into an analog signal by the A converter 22 and sent to the summing amplifier 12 as an extraction voltage designating signal. Therefore, the operator rotates the rotary encoder 15 in anticipation of the characteristic curve shown in A of FIG. 2 so that the extraction voltage designating signal corresponding to V ₀ of FIG. Second from the current designation signal generation circuit 13
It is assumed that a signal corresponding to I ₀ in the figure is generated. On the other hand, it is assumed that the actual characteristics of the ion beam current I and the extraction voltage V are as shown by B in FIG.

In such a case, the output signal X of the amplifier 10 gradually increases in order to realize the target beam current I ₀ , and finally exceeds the level of the signal S1 in FIG.
As a result, the comparator 23 outputs a high-level signal instead of the low-level signal up to that point. When a high level signal is sent from the comparator 23, the pulse generating circuit 27 continues to generate pulses until the output signal X of the amplifier 10 does not exceed S1. Since this pulse is sent to the up / down counter 21 via the OR circuit 17, the up / down counter 21 counts up. Therefore, the extraction voltage increases from V _{0 in} FIG. 2 to about V ₁ -ΔV based on the output signal of the DA converter 22 which is the extraction voltage designating signal. As a result, the detection signal based on the ion beam current detector 3 becomes smaller than the reference signal from the reference signal generator 25, so that the output signal of the comparator 23 becomes low level. After the output signal of the comparator 23 changes to the low level, the pulse generation circuit 27 further generates a preset number of pulses and then terminates the generation of pulses. This preset pulse corresponds to the magnitude of ΔV in FIG. 2, and as a result, the extraction voltage shifts to the value of V1 in FIG. 2 based on the output signal of the DA converter 22. At the stage where this shift is completed, the extraction voltage is limited within the width of 2ΔV by the limit circuit 11 centering on V1, but within this range, the point P1 of I = I ₀ on the characteristic line B
Is present, negative feedback control for maintaining the ion beam current at I ₀ can be performed based on the output signal of the amplifier 10. Therefore, without complicated readjustment of the extraction voltage designating signal by hand, the ion beam having the initially set current I ₀ can be generated from the emitter 1 to draw the material 6. When the characteristic line (b) shifts to the side opposite to the characteristic line (b), a high level signal is generated from the comparator 24, and the same curing as described above can be achieved.

Further, the gate signal may not be generated by the gate signal generation circuit 29 when the emitter is flushed or when the ion beam is not generated.

The above-described embodiment is only one embodiment of the present invention, and the present invention can be modified and implemented.

For example, in the above-described embodiment, as shown in FIG. 3, the characteristic of the limit circuit 11 is such that the range of the − side of X is set to, for example, twice as wide as the + side, and the reference signal is generated accordingly. The absolute value of the output signal from the generator 26 may be double the absolute value of the output signal from the reference signal generator 25.

Further, in the above-described embodiment, the electric current generated from the emitter 1 is detected by using the diaphragm-shaped detector arranged in the optical path of the ion beam, but a resistance is provided between the acceleration power source 8a and the emitter 1. The ion beam current may be detected by disposing an element and extracting the current flowing through the resistance element.

Furthermore, the extraction power supply is divided into two currents, the output voltage of one power supply is controlled based on the output signal of the extraction voltage designating signal generating circuit, and the output voltage of the other power supply is generated by the ion beam current designating signal. It is also possible to omit the summing amplifier by controlling based on the output signal of the circuit and setting the added voltage of the output voltages of both power supplies as the extraction voltage.

[Effects of the Invention] As is apparent from the above description, in the device according to the present invention, a circuit for detecting that the output signal of the amplifier deviates from the limit range of the limit circuit, and a signal from the detection circuit. Based on the above, since the output signal of the amplifier does not deviate from the limited range of the limit circuit, a control circuit for automatically shifting the designation signal from the extraction voltage designation signal generating circuit is provided, so that the gas phase ion The voltage-current characteristics of the source deviate from what is expected, so that if the desired ion beam current cannot be obtained by the initial specification of the extraction voltage and the ion beam current, the extraction voltage specification signal It is possible to shift the set value to an appropriate value and perform negative feedback control to extract the set ion beam current, improving operability. An ion beam device is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for showing an embodiment of the present invention, and FIG. 2 is a diagram for explaining changes in the voltage-current characteristics of a gas phase ion source and the operation of the above-mentioned embodiment device. FIG. 3 is a diagram showing a modification of the characteristic of the limit circuit, FIG. 4 is a diagram showing a conventional device, and FIG. 5 is a characteristic of the limit circuit and a reference signal set by a reference signal generator. Figure 6 to show
The figure is a figure for showing the conventional fault. 1: Emitter, 2: Extraction electrode 3: Ion beam current detector 4: Focusing lens, 5: Objective lens 6: Drawing material, 7: Accelerating electrode 8a: Extraction power supply, 8b: Control circuit 9: Amplifier, 10: Difference Dynamic amplifier 11: Limit circuit, 12: Addition amplifier 13: Beam current designation signal generation circuit 14: Extraction voltage designation signal generation circuit 15: Rotary encoder 16: Up / down pulse generation circuit 17, 18: OR circuit 19, 20: AND circuit 21: Up-down counter 22: DA converter, 23, 24: Comparator 25, 26: Reference signal generation circuit 27, 28: Pulse generation circuit 29: Gate signal generation circuit

Claims (1)

[Claims] 1. An extraction power source for applying an extraction voltage between an emitter and an extraction electrode of a gas phase ion source, a detection means for detecting the amount of ion beam current generated by the emitter, and a detection means for detecting the ion beam current amount. An amplifier for amplifying a deviation between the output signal and a signal representing the set value of the ion beam current amount, a limit circuit for limiting and outputting the output signal value range of the amplifier within a predetermined width, and the drawer. An extraction voltage designating signal generation circuit that generates a signal for designating an output voltage of the power supply, and an output voltage of the extraction power supply is controlled based on the output signal of the limit circuit and the output signal of the extraction voltage designating signal generation circuit. A device for detecting that the output signal of the amplifier deviates from the limited range of the limit circuit, and the circuit based on the signal from the detection circuit. Ion beam and wherein the output signal of the wide unit has a control circuit for automatically shifting the designation signal from the extraction voltage designation signal generating circuit so as not to deviate from the limit range of the limiter circuit.