JPS63216256A - Charged particle beam device - Google Patents

Abstract

PURPOSE:To perform the axis alignment in a short time by concurrently feeding a wobbler signal to multiple lenses and reversing the phase of some lenses. CONSTITUTION:Only specific type of ions among multiple types of ions from an emitter 1 are advanced straightly by an EXB filter 6 and radiated to a sample 10. An ion beam is scanned two-dimensionally on the sample 10 by the signal from a scan signal generating circuit to deflecting electrodes 9. Secondary electrons by the radiation are detected by a detector 16, the detection signal is fed to a cathode-ray tube 18, and a secondary electron image is displayed. To perform the axis alignment between a focusing lens 4 and an objective lens 7, a wobbler signal is fed to an amplifier 26 and a reversal amplifier 27 via amplitude adjusters 20, 21, 22 from a generator 19. The amplified signal is fed to a high-voltage power supply 12 for the lens 4. A signal with the same cycle and the opposite phase to the signal to the power supply 12 is fed to a high-voltage power supply 14 for the lens 7. When a switch 24 is turned on and a switch 25 off, the wobbler signal is applied only to the lens 4. Accordingly, the axis alignment can be performed in a short time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a charged particle beam device that irradiates a sample with an electron beam or an ion beam, and particularly relates to a charged particle beam device suitable for aligning a lens. Regarding line equipment.

[Prior art] For example, in a focused ion beam device, an ion beam generated from an emitter is directed to a sample or material F4 using an electrostatic lens.
It is designed to narrowly focus on targets such as By the way, the irradiation position of the ion beam on the target is scanned, the secondary electrons generated from the sample are detected along with the scanning, and the detected secondary electron signals are transmitted to the cathode ray tube in synchronization with the scanning. When the electron beam is supplied to the cathode ray tube, the secondary electron density of the sample is displayed on the cathode ray tube. When aligning the axis of the ion beam after exchanging the emitter, if the voltage applied to the electrostatic lens is periodically varied using a wobbler mechanism, if the ion beam does not pass through the center of the lens, The image vibrates as the applied voltage changes. While observing the state of the image on the cathode ray tube, the signal supplied to the alignment electrode placed above the lens is adjusted, and the ion beam is appropriately deflected. The statue also stops moving. At this time, the alignment of the lenses is completed.

[Problem to be Solved by the Invention 1] In a focusing system using two stages of electrostatic lenses, each lens is provided with a wobbler mechanism to enable axis alignment of each lens. In this case, after applying a variable voltage to the first stage lens to align the first stage lens, apply a variable voltage to the second stage lens to align the second stage lens. That's what I do. However, when the axis of each lens is aligned once, the axes of the entire lens are not ideally aligned, and it is necessary to repeat the alignment of each lens many times alternately, which is a complicated operation. In addition, periodically changing the lens voltage causes the focal position to change, and the image on the cathode ray tube not only vibrates, but also changes the degree of blurring, making it difficult to accurately determine the state of image vibration. It becomes difficult to understand the situation.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a charged particle beam device in which lens alignment can be easily performed.

[Means for Solving the Problems] A charged particle beam device according to the present invention includes at least first and second lenses for converging a charged particle beam onto a target. It is characterized in that it is configured to supply wobbler signals having the same period and opposite phases to the first and second lenses.

Effect] A wobbler signal is supplied to the first and second lenses at the same time, but the wobbler signals have the same period and opposite phases. As a result, it is possible to simultaneously adjust the axis alignment of the first and second stage lenses, and the focal position of the charged particle beam does not change even when the wobbler signal is supplied. images can be easily observed.

[Example] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a focused ion beam device, in which 1 is an emitter, 2 is an extraction electrode, and 3 is an emitter.
is an accelerating electrode; for example, the liquid metal at the tip of the emitter 1 is extracted and ionized by the extraction voltage applied to the extraction electrode 2, and the accelerating voltage applied between the emitter 1 and the accelerating electrode 3 accelerated by 4
is a convergent lens, 5 is an alignment electrode of the convergent lens 4,
6 is an EXB filter, 7 is an objective lens, 8 is an alignment electrode of the objective lens 7, 9 is a deflection electrode, and 10 is a sample. The ion beam from the emitter 1 is narrowly focused onto the sample 10 by the converging lens 4 and objective lens 7. 11 is an alignment signal generator that generates an alignment signal to be supplied to the alignment electrode 5; 12 is a high voltage power source for the converging lens 4; 13 is an alignment signal generator that generates an alignment signal to be supplied to the alignment electrode 8; 14 is an alignment signal generator that generates an alignment signal to be supplied to the alignment electrode 5; A high-voltage power supply for the objective lens 7; 15 a scanning signal generation circuit that generates a scanning signal to be applied to the deflection electrode 9; 16 a detector that detects secondary electrons generated when the sample is irradiated with the ion beam; 17 is an amplifier; 18 is a cathode ray tube to which a signal detected by the detector 16 and amplified by the amplifier 17 is supplied as a luminance signal; a deflection coil of the cathode ray tube receives a scanning signal from the scanning signal generation circuit 15; is supplied. 1 is a wobbler signal generator, 20.21.22 is a signal adjuster for arbitrarily adjusting the signal strength, 23.24°25 is a switch, 26
is an amplifier, and 27 is an inverting amplifier.

In the above-described configuration, the ion beam generated from the emitter 1 is narrowly focused onto the sample 10 by the converging lens 4 and the objective lens 7. Only EX
The light travels straight through the B filter 6 and is irradiated onto the sample 10.

Here, by supplying a scanning signal from the scanning signal generation circuit 15 to the deflection electrode 9, the ion beam is
Scanned dimensionally. The secondary electrons generated by irradiation of the sample with the ion beam are detected by the detector 16, and the detection signal is supplied to the cathode ray tube 18 to which the scanning signal from the scanning signal generation circuit 15 is supplied. , a secondary electron image of the sample will be displayed on the cathode ray tube.

Now, when aligning the axes of the converging lens 4 and the objective lens 7, a wobbler signal from the wobbler signal generator 19 is supplied to the lens. The signal shown in FIG. 2(a) is generated from the generator 19, and this signal is supplied to an amplifier 26 and an inverting amplifier 27 via amplitude adjusters 20, 21 and 22. The signal shown in FIG. 2(a) amplified by the amplifier 26 is transmitted to the high-voltage power supply 1
2, so that from the power source 12 the converging lens 4
The voltage applied to will vary periodically. On the other hand, since the inverting amplifier 27 inverts and amplifies the signal shown in FIG.
As shown in FIG. (1)), a signal having the same period as the signal supplied to the high-voltage power supply 12 of the converging lens but having an opposite phase is supplied. As a result, the voltage applied from the power source 14 to the objective lens 7 will fluctuate periodically, but the phase of this fluctuation will be opposite to the phase of the voltage applied to the converging lens 4.

Now, when the switch 24 is turned on and the switch 25 is turned off, a variable voltage, that is, a wobbler signal, is applied only to the converging lens 4. The state of focus f3 of the ion beam in this case is shown in FIG. 3(a). In the figure, the state of the actual FAB + is just focus, the state of point ta B z is the state of overfocus due to the high voltage applied to the converging lens, and the state of the two-dot chain PiIB 3 is the state of focus to the converging lens 4. This is a state in which the applied voltage has become low, resulting in underfocus. In this figure, the optical axis and converging lens 4
．． The center of the objective lens 7 coincides with the center of the converging lens 4.
Even if a wobbler signal is applied to the ion beam, the focal point of the ion beam in the direction perpendicular to the optical axis does not move. However, if the optical axis and the lens center do not match, the focal point will move perpendicular to the optical axis. It will move in the direction. Also, turn on switch 25
When the switch 24 is turned off, the wobbler signal is applied only to the objective lens 7. The focused state of the ion beam in this case is shown in FIG. 3(b). In the figure, solid line 8
State 1" is just focus, the state indicated by dotted line B2 is a state in which the voltage applied to the converging lens 4 has become high and overfocus has occurred, and the state indicated by two-dot chain line B3 is a state in which the voltage applied to the converging lens 4 has become low. This is a state of underfocus. In this figure, as before, the optical axis and the center of the converging lens 4 and objective lens 7 coincide, and even if the wobbler signal is applied to the objective lens 7, the light The focal point of the ion beam in the direction perpendicular to the axis does not move, but if the optical axis and the lens center do not coincide, the focal point will move in the direction perpendicular to the optical axis. Figure 3 (
In both a) and (b), the application of a wobbler signal to the lens changes the focal point of the ion beam in the optical axis direction, and the resulting secondary electron image becomes blurred as the focal point changes. .

Now, when both switches 24 and 25 are turned ON, the wobbler signal shown in FIG. 2(a) is applied to the converging lens 4, and the wobbler signal shown in FIG. 2<1)) is applied to the objective lens 7. Ru. As a result, both wobbler signals have the same period and opposite phases, so when the ion beam is strongly focused by the converging lens 4, the ion beam is focused by the objective lens 7, as shown by the dotted line F1 in FIG. Conversely, when the ion beam is weakly focused by the converging lens, as shown by the two-dot chain line F2, the ion beam is strongly focused by the objective lens 7. As shown by the solid line F3, when the converging lens 4 is in just focus, the objective lens 7 is also in just focus. Therefore, the movement of the focal point in the optical axis direction by the converging lens 4 is offset by the movement of the focal point by the objective lens 7, and an in-focus image can always be obtained even by supplying the wobbler signal. Na J3,
If the image becomes blurred depending on the supply of the wobbler signal, the amplitude adjusters 21 and 22 may be adjusted to arbitrarily increase or decrease the amplitude of the wobbler signal to prevent the image from becoming blurred. Although the image does not become blurred by supplying the wobbler signal to both lenses, if the center of each lens does not match the optical axis, the application of the wobbler signal to the lenses causes the image to become blurred on the cathode ray tube 18. The image will vibrate. While monitoring the vibration of the image on the cathode ray tube, the alignment signal generator 1
1.13 and align the center of the lens with the axis of the ion beam, the image on the cathode ray tube 18 will not vibrate even when the wobbler signal is supplied, and the axis alignment of each lens is completed. It turns out. After the axis alignment of each lens is completed, the switch 23 is turned off, and the supply of the wobbler signal to each lens is stopped.

In this embodiment, it is necessary to fix the focal position of the converging lens 4 to the center of the 1ifl field of the EXB filter 6, but this adjustment can be easily performed by supplying the Wopler signal to the converging lens 4. can. Further, it is effective to adjust the signal adjuster 20 and adjust the amplitude of the wobbler signal applied to each lens in accordance with coarse adjustment or fine adjustment of the axis alignment.

Although one embodiment of the present invention has been described above in detail, the present invention is not limited to this embodiment and can be modified in many ways.

For example, although an example in which an ion beam is focused by an electro-electric lens has been described, the present invention can also be applied to a case where an electron beam is focused by a magnetic field type lens. Further, the present invention can be applied not only to a two-stage focusing system but also to a three-stage or more focusing system. In the case of a three-stage focusing system, the phase of the fluctuation signal applied to any one stage lens and the fluctuation signal applied to the other two lenses are reversed, and the beam finally irradiated on the target is adjusted. It is sufficient that the focal point is not changed even by supplying the fluctuation signal.

[Effects] As detailed above, in the present invention, wobbler signals are simultaneously supplied to a plurality of lenses, and the phase of the wobbler signals is reversed depending on the lenses, so that alignment of the entire lens system can be accomplished in a short time. In addition, it is possible to perform the alignment work while observing a focused image during the alignment work.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a wobbler signal, and FIG. 3 is a diagram showing a state of beam focusing in response to supply of the wobbler signal to the lens. 1... Emitter 2... Extraction electrode 3...
・Accelerating electrode 4... Converging lens 5.8...
Alignment electrode 6...EXB filter 7...Objective lens 9...
・Deflection electrode 1o...Sample 11.13 Alignment signal generator 12.14...High voltage power supply 15...Scanning signal generation circuit 16...Detector 17...Amplifier 18...
・Cathode ray tube

Claims (2)

[Claims] (1) In a charged particle beam device having at least first and second lenses for converging a charged particle beam onto a target, wobblers having the same period and opposite phases are attached to the first and second lenses. A charged particle beam device configured to provide a signal. (2) The charged particle beam device according to claim 1, wherein the amplitude of the wobbler signal supplied to the first and second lenses can be adjusted.