JPH0240849A - Charged particle beam device - Google Patents

Abstract

PURPOSE:To prevent a sample from receiving a damage by setting an accelerating voltage and a sample (target) applying voltage so that the differential voltage does not have a magnitude as causing a damage to the sample, when these voltages are set by an operator. CONSTITUTION:In either of an accelerating voltage generating circuit 10 or a target 5 applying voltage generating circuit 11, a voltage value corresponding to the voltage giving a charged particle an energy to the extent not causing a damage to the target 5 is set only a time. Thereafter, various voltage values corresponding to the target 5 applying voltage or accelerating voltage value are set in the other circuit. Thus, not only the operation is made extremely simple, but also the energized voltage is fixed except when the energized voltage is particularly changed. Hence, the target 5 can be prevented from receiving a damage during the operation by an operator.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a retarding type charged particle beam device, and in particular, to facilitate the setting of acceleration voltage and target applied voltage, and to The present invention relates to a charged particle beam device that prevents irradiation of a beam with energy that would damage a target.

[Conventional technology] Recently, electron beam lithography equipment and scanning electron microscopes have been developed.

BACKGROUND ART In charged particle beam devices such as focused ion beam devices and focused ion beam devices, a beam irradiation method that can maintain high resolution without damaging the target is used. That is, if the accelerating voltage is increased, the beam can be narrowed down, so if the target is irradiated with the beam, the resolution can be increased, but the damage to the target is large. Of course, lowering the accelerating voltage will reduce damage to the target, but since the beam cannot be narrowed down, the resolution will decrease.

Therefore, by keeping the accelerating voltage high and applying a voltage to the target that has the same polarity as the accelerating voltage and is smaller than the accelerating voltage (target applied voltage), the beam will be accelerated at the high accelerating voltage, but the target will not be accelerated. The beam is irradiated with energy based on the voltage that corresponds to the difference between the voltage and the voltage applied to the target, making it possible to maintain high resolution without damaging the target. This method is called a retarding method.

FIG. 4 is a schematic diagram of a scanning electron microscope shown as an example of a charged particle beam device employing such a tarding method.

In the figure, 1 is an electron source, 2 is a focusing lens, and 3X.

3Y is an X-direction and Y-direction deflection coil, 4 is an objective lens, 5 is a sample (target), 6 is a secondary electron detector, 7 is an amplifier, 8 is a display device such as a cathode ray tube, and 9 is a scanning signal generation circuit. , 10 is an accelerating voltage generation circuit, 11 is a sample applied voltage generation circuit, and 12 is a DC power supply.

In such an apparatus, an accelerating voltage Va (for example, 30 KV) is generated by an accelerating voltage generating circuit 10 and applied to the electron generating source 1. At this time, at the same time, the sample applied voltage generation circuit 11
A sample applied voltage Vs (for example, 29 KV) is generated and applied to the sample 5. Then, the electrons generated from the electron source 1 are accelerated by the accelerating voltage Va and move toward the sample. The electron beam is focused onto the sample by a focusing lens 2 and an objective lens 4, and at the same time is scanned over the sample by deflection coils in the X and Y directions. At this time, the acceleration voltage Va (30KV) and the sample applied voltage Vs (29KV) are applied to the sample 5.
) is irradiated with electrons energized with energy corresponding to the difference (Va-Vs) (IKV). Secondary electrons generated from the sample by the scanning are detected by a secondary electron detector 6 and sent to a cathode ray tube 8 via an amplifier 7. The cathode ray tube 8 is provided with the above-mentioned X direction and Y direction deflection coils 3X, 3Y.
Since the X and Y scanning signals are sent in synchronization with the supply to the cathode ray tube, the sample image is displayed on the screen of the cathode ray tube.

Now, the accelerating voltage generating circuit 10 and sample applied voltage generating circuit 11 in such an apparatus are constructed as shown in FIG.

In the figure, 13.14 is an oscillation drive circuit, 15.16 is a step-up transformer, 17.18 is a rectification and ripple removal circuit,
Reference numerals 19 and 20 are voltage detection resistors, 21 and 22 are an acceleration voltage setter and a sample voltage setter, respectively, and 23 and 24 are error amplifiers.

In such a circuit, when the accelerating voltage is set by the accelerating voltage setter 21, a current corresponding to the set voltage enters the error amplifier 23, so the error amplifier oscillates the DC voltage from the DC power supply 12 at several tens of KH2. Oscillation drive 1
3 to generate a voltage 1/N of the acceleration voltage to be set from the oscillation drive. The voltage is a step-up transformer 15
Since the voltage is boosted eight times and sent to the rectification and ripple removal circuit 17, a predetermined acceleration voltage is generated from the circuit. At this time, a voltage corresponding to the accelerating voltage from the rectification and ripple removal circuit 17 is detected by the voltage detection resistor 19, and a current corresponding to the voltage enters the error amplifier 23.
The error amplifier feeds back the difference between the current corresponding to the detected acceleration voltage and the current corresponding to the acceleration voltage set by the acceleration voltage setter 21 to the oscillation drive 13, and outputs a predetermined signal from the rectification and ripple removal circuit 17. Make sure that accelerating voltage is generated.

The sample applied voltage is also set by the sample applied voltage setting device 22,
A current corresponding to the set voltage enters the error amplifier 24. The error amplifier converts the DC voltage from the DC power supply 12 to several tens of KH.
2, the oscillation drive 14 which is being oscillated is controlled, and the oscillation drive generates a voltage that is 1/N of the voltage applied to the sample to be set.

This voltage is boosted eight times by the step-up transformer 16 and sent to the rectification and ripple removal circuit 18, so that a predetermined sample applied voltage is generated from this circuit. At this time, a voltage corresponding to the voltage applied to the sample from the rectification and ripple removal circuit 18 is detected by the voltage detection resistor 20, and a current corresponding to the voltage enters the error amplifier 24, so that the error amplifier detects the detected voltage. The difference between the current corresponding to the sample applied voltage and the current corresponding to the sample applied voltage set by the sample applied voltage setting device 22 is fed back to the oscillation drive 14, and the rectification and ripple removal circuit 18 outputs a predetermined sample applied voltage. Let it happen.

[Second Problems to be Solved by the Invention] As described above, the setting of the accelerating voltage and the setting of the voltage applied to the sample are configured to be performed separately. For that reason,
When the operator sets the acceleration voltage and sample applied voltage,
The accelerating voltage setting device 21 and sample applied voltage setting device 22 are operated with great care so that the voltage difference does not reach a level that would damage the sample. This operation is extremely troublesome. Moreover, since this operation is troublesome, the voltage difference increases instantaneously or for a short period of time during the operation, and the sample is often damaged.

The present invention aims to solve such problems and provides a novel charged particle beam device.

[Means for Solving the Problems] To this end, the charged particle beam device of the present invention includes a charged particle generation source, a lens system that focuses charged particles from the charged particle generation source and irradiates the charged particles onto a target, and the charged particle beam device of the present invention. an accelerating voltage generation circuit that generates a voltage for accelerating charged particles from a particle generation source; and a target applied voltage that generates a voltage that is smaller than the accelerating voltage but has the same polarity as the accelerating voltage to the target. In a charged particle beam device equipped with a generation circuit, either the accelerating voltage generation circuit or the target applied voltage generation circuit sets a voltage (energizing voltage) value that applies energy to the charged particles to an extent that does not damage the target. If a voltage value corresponding to the energizing voltage is set in the former circuit, a voltage value corresponding to the target applied voltage value is set in the latter circuit to generate the target applied voltage value. In the former circuit, the accelerating voltage value is generated from the voltage value obtained by adding the voltage value corresponding to the energizing voltage and the voltage value corresponding to the target applied voltage value, and in the latter circuit, the energizing voltage is generated. If a voltage value corresponding to the acceleration voltage value is set in the former circuit, the voltage value corresponding to the acceleration voltage value is set to generate the acceleration voltage value, and the voltage value corresponding to the acceleration voltage value is set in the latter circuit. The target applied voltage value is generated from the voltage value corresponding to the difference between the target applied voltage value and the voltage value corresponding to the applied voltage.

[Embodiment] FIG. 1 is a schematic diagram of an accelerating voltage generation circuit 1o and a sample applied voltage generation circuit 11, which are essential parts of a scanning electron microscope shown as an embodiment of the present invention.

In the figure, the same components are denoted by the same numbers as those used in FIG. 5 above.

In the figure, reference numeral 25 denotes an adder that adds the current corresponding to the voltage from the accelerating voltage setter 21 and the current corresponding to the voltage from the sample voltage setter 22 and inputs the result to the error amplifier 23.

Next, the operation of the accelerating voltage generating circuit 10 and sample applied voltage generating circuit 11 will be described when applied to the scanning electron microscope shown in FIG. 4 above.

A case will be described in which electrons irradiating a sample are energized with a voltage (hereinafter referred to as an energizing voltage) that provides energy to the electrons to an extent that does not damage the sample, for example, IKV energy.

First, only at the beginning, the acceleration voltage setter 21 is set to the energizing voltage Vo.
(IKV). Thereafter, except for the first setting when changing the magnitude of the energizing voltage, the accelerating voltage setter 21
is not manipulated.

In this state, the sample applied voltage Vs (for example, 29 KV) is set in the sample voltage setting device 22, taking into consideration the magnitude of the accelerating voltage. Then, the adder 25 outputs the energizing voltage Vo (I
A current corresponding to the sum of the sample voltage Vs (29 KV) and the sample applied voltage Vs (29 KV) is input into the error amplifier 23. Thereafter, the operation is similar to that described in FIG. 5, and the added voltage, that is, (Vo+Vs)(30
KV) is the predetermined acceleration voltage Va in the acceleration voltage generation circuit 1.
Generated from 0. At this time, since the sample applied voltage Vs (for example, 29 KV) set by the sample voltage setting device 22 is also input to the error amplifier 24, the operation is the same as explained in FIG. 5, and the sample applied voltage A predetermined sample applied voltage Vs (29 KV) is generated from the generating circuit 11.

In this way, the acceleration voltage generation circuit 10 generates the acceleration voltage Va, that is, t.
), (Vo+Vs) (30KV) are generated and applied to the electron generation source 1. At the same time, the sample applied voltage generation circuit 11 generates a sample applied voltage Vs (29 KV) and applies it to the sample 5. Then, the electrons generated from the electron source 1 are accelerated by the accelerating voltage Va and move toward the sample. The electron beam is focused onto the sample by a focusing lens 2 and an objective lens 4, and at the same time is scanned over the sample by deflection coils in the X and Y directions. At this time, the acceleration voltage (Vo+Vs) (30KV) and the sample applied voltage Vs (2
Electrons energized with energy corresponding to the difference Vo (IKV) of 9KV) are irradiated. Secondary electrons generated from the sample by the scanning are detected by a secondary electron detector 6,
The signal is sent to a cathode ray tube 8 via an amplifier 7. The cathode ray tube 8
Since X and Y scanning signals are sent to the X and Y direction deflection coils 3X and 3Y in synchronization with the supply to the X and Y direction deflection coils 3X and 3Y, a sample image is displayed on the screen of the cathode ray tube.

Next, when changing the accelerating voltage Va, only the sample voltage setting device 22 is operated as described below, and the setting value of the voltage applied to the sample in the setting device is changed. That is, the sample applied voltage Vs is the difference between the accelerating voltage Va and the energizing voltage Vo, and the energizing voltage Vo is I
Since it is fixed at KV, for example, the acceleration voltage Va is
To increase the voltage to 32 KV, set the sample voltage setting device 22 to 31 KV as the sample applied voltage. Further, for example, in order to lower the acceleration voltage Va to 28 KV, the sample voltage setting device 22 is set to 27 KV as the sample applied voltage.

When changing the accelerating voltage Va in this way, it is only necessary to operate the sample voltage setting device 22 and change the setting value of the sample applied voltage on the setting device. In either case, the energy corresponding to Vo (IKV) is set. The energized electrons are irradiated.

Furthermore, when changing the magnitude of the energizing voltage Vo, first set the desired energizing voltage in the accelerating voltage setter 21, and while the set voltage is fixed, determine the magnitude of the accelerating voltage. Depending on the degree of application, set an appropriate sample applied voltage in the sample voltage/setter 22.

FIG. 2 shows another embodiment of the accelerating voltage generating circuit and the sample applied voltage generating circuit, each designated by 1011'. In the figure, the same numbers as those used in FIG. 1 above represent the same components. In this embodiment, the accelerating voltage setting system and sample applied voltage setting system are digitalized.

In the figure, 26.27 is the rotary encoder 28.29
is up/down counter 3o is addition circuit, 31.3
2 is a data conversion circuit, and 33 and 34 are DA converters.

For example, when the rotary encoder is turned to the right, the number of up pulses corresponding to the amount of rotation is sent to the up/down counter, and when turned to the left, the number of down pulses corresponding to the amount of rotation is sent to the up/down counter. The up/down counter increases/decreases the count value using up pulses and down pulses from the rotary encoder.

First, only at the beginning, the energizing voltage Vo (for example, IKV) is controlled by the up/down counter 2 using the rotary encoder 26.
Set to 8. Thereafter, the rotary encoder 26 is not operated except for the initial setting when changing the magnitude of the energizing voltage. In this state, considering the magnitude of the accelerating voltage,
The sample applied voltage Vs (for example, 29 KV) is set on the up/down counter 29 using the rotary encoder 27 . The output of the up/down counter 28 is sent to an addition circuit 30, and the output of the up/down counter 29 is sent to the addition circuit 30 and a data conversion circuit 32, respectively. The adder circuit 30 receives an energizing voltage V.

The voltage value corresponding to the sample applied voltage Vs is added to the voltage value corresponding to the sample applied voltage Vs, and the added voltage value, that is, the voltage value corresponding to the acceleration voltage is sent to the data conversion circuit 31. Each of the data conversion circuits described above controls how many volts are changed per pulse.

The outputs of the data conversion circuits 31 and 32 (respectively, acceleration voltage VA (30KV), sample applied voltage Vs (29KV)
) is input to the error amplifiers 23 and 24 via the DA converters 32 and 34.

The subsequent operation is performed in the same manner as the operation explained in FIG. 1, and the acceleration voltage Va, ie,
(Vo+Vs) (30 KV) is generated, and the sample applied voltage Vs (29 KV) is generated from the sample applied voltage generation circuit 11-. Then, the acceleration voltage (Vo+Vs
) (30 KV) and the sample applied voltage Vs (29 KV). Electrons energized with energy corresponding to the difference Vo (IKV) are irradiated.

FIG. 3 shows another embodiment of the accelerating voltage generating circuit and the sample applied voltage generating circuit in which the accelerating voltage setting system and the sample applied voltage setting system are digitalized. In the figure, the same numbers as those used in FIG. 2 above represent the same components.

The difference from the embodiment shown in FIG. 2 above is that the addition circuit 30 in FIG.
In contrast, in FIG. 3, a subtraction circuit 35 is provided between the up/down counter 29 and the data conversion circuit 32. First, the energizing voltage Vo (for example, IKV) is set in the up/down counter 29 using the rotary encoder 27 only at the beginning.

Thereafter, the rotary encoder 27 is not operated except for the initial setting when changing the magnitude of the energizing voltage. In this state, a desired acceleration voltage Va (for example, 30 KV) is set in the up/down counter 28 using the rotary encoder 26. The output of the up-down counter 29 is sent to the subtraction circuit 35, and the up-down counter 28
The outputs are sent to the subtraction circuit 35 and the data conversion circuit 31, respectively. The subtraction circuit 35. subtracts the voltage corresponding to the accelerating voltage Va and the voltage value corresponding to the energizing voltage Vo, and sends the difference voltage value, that is, the voltage value corresponding to the sample applied voltage to the data conversion circuit 32. Each data conversion circuit 31.
The outputs of 32 (corresponding to acceleration voltage VA (30 KV) and sample applied voltage Vs (29 KV), respectively) are input to error amplifiers 23.24 via DA converters 32.34. The subsequent operation is performed in the same manner as the operation explained in FIG.
1, that is, (Vo+Vs) (30KV) is generated, and the sample applied voltage Vs (2
9KV) is generated. Then, sample 5 is applied with accelerating voltage (
Vo+Vs) (30KV) and sample applied voltage Vs (29
KV) (7) Electrons energized with energy corresponding to the difference Vo (IKV) are irradiated.

Although each of the above embodiments has been described using a scanning electron microscope as an example, the present invention is not limited thereto, and can be applied to an apparatus having an accelerating voltage generation circuit and a target applied voltage generation circuit.

[Effects of the Invention] The present invention provides a voltage (energizing voltage) that applies energy to charged particles to an extent that does not damage the target in either the accelerating voltage generating circuit or the target applied voltage generating circuit only once at the beginning. After that, in the other circuit, various voltage values corresponding to the target applied voltage or acceleration voltage value are set. The configuration is not such that settings and sample applied voltage settings are performed separately. Therefore, not only is the operation extremely easy, but the energizing voltage is fixed except when changing the energizing voltage, so there is no possibility of damaging the target during operation by the operator. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an accelerating voltage generating circuit and a sample applied voltage generating circuit, which are the main parts of a scanning electron microscope shown as an embodiment of the present invention, and FIG. 2 is a schematic diagram of an accelerating voltage generating circuit and a sample applied voltage generating circuit. Fig. 3 shows another embodiment of the accelerating voltage generation circuit and sample applied voltage generation circuit in which the accelerating voltage setting system and the sample applied voltage setting system are digitalized, Fig. 4 FIG. 5 is a schematic diagram of a scanning electron microscope shown as an example of a charged particle beam apparatus employing the beam tarding method, and FIG. 5 is a schematic diagram of a conventional accelerating voltage generation circuit and sample application voltage generation circuit. 1: Electron source 2: Focusing lens 3X. 3Y: X direction, Y direction deflection coil 4: Objective lens
5: Sample (target) 6: Secondary electron detector
7: Amplifier 82 Display device 9: Scanning signal generation circuit 10: Accelerating voltage generation circuit 11: Sample applied voltage generation circuit 12: DC power supply 13.14: Oscillation drive circuit 15° 16: Step-up transformer 17.18: Rectification and ripple Elimination circuit 19.20: Voltage detection resistor 2
1.22: Accelerating voltage setting device Sample voltage setting device 23
．． 24: Error amplifier 25: Adder 26. 27: Rotary encoder 28. 297 up/down counter 30: Addition circuit 31. 32: Data conversion circuit 33, 34: DA converter

Claims (1)

[Claims] A charged particle generation source, a lens system that focuses charged particles from the charged particle generation source and irradiates it onto a target, an accelerating voltage generation circuit that generates a voltage for accelerating the charged particles from the charged particle generation source, and the above. In a charged particle beam device equipped with a target applied voltage generation circuit that generates a voltage for applying a voltage smaller than the accelerating voltage to the target but having the same polarity as the accelerating voltage, the accelerating voltage generating circuit and the target applied voltage generating circuit are provided. In either of the circuits, set a voltage value corresponding to the voltage (energizing voltage) that gives energy to the charged particles to the extent that it does not damage the target, and in the former circuit, set a voltage value corresponding to the energizing voltage. In this case, the voltage value corresponding to the target applied voltage value is set in the latter circuit to generate the target applied voltage value, and the voltage value corresponding to the energizing voltage and the target applied voltage value are set in the former circuit. The accelerating voltage value is generated from the voltage value obtained by adding the corresponding voltage values, and when the voltage value corresponding to the energizing voltage is set in the latter circuit, the voltage corresponding to the accelerating voltage value is set in the former circuit. A value is set to generate an accelerating voltage value, and the latter circuit generates a target applied voltage value from a voltage value corresponding to the difference between the voltage value corresponding to the accelerating voltage value and the voltage value corresponding to the energizing voltage. A charged particle beam device designed to