JPH01221848A - Charged particle ray device - Google Patents

Abstract

PURPOSE:To improve the detecting efficiency of a secondary electron by providing a means for applying negative micro voltage for a target to a secondary electron detector arranged between the target and an auxiliary electrode, and the auxiliary electrode. CONSTITUTION:Between a target 7 and a decelerating electrode 8 is provided a power supply 11 for applying micro voltage less than the target 7 to the decelerating electrode 8. A secondary electron having a small outgoing angle, therefore, is returned toward the target 7 with the negative voltage applied to the decelerating electrode 8, and the efficient incidence thereof to a micro channel plate 10 as a secondary electron detector becomes possible. According to the aforesaid construction, the detecting efficiency of the secondary electron is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a charged particle beam device, and particularly to a charged particle beam device that irradiates a target with a decelerated charged particle beam.

[Prior Art] In an ion beam device or an electron beam device, a target is irradiated with an ion beam or an electron beam, and the irradiation position is moved to draw a desired figure, or the ion beam or electron beam is Secondary electrons generated during the irradiation of the target are detected, and the surface of the target is observed. By the way, when a target is irradiated with a beam accelerated at about 30 kV, for example, the high energy of this beam may damage the surface of the target or etch the surface portion of the target to change its shape. For this reason, the beam acceleration voltage can be lowered and
It is possible to reduce the energy of the beam irradiated to the target, but lowering the accelerating voltage increases the amount of chromatic aberration in the beam, making it impossible to focus the beam narrowly with a focusing lens, and damaging or etching the target. Although this can be avoided, it becomes impossible to irradiate a minute part with a beam with high accuracy.

For this reason, it has been considered to accelerate the beam with a high acceleration voltage while forming a deceleration electric field between the focusing lens and the target. For example, for an electron beam, -30k
By accelerating at V and applying -27 kV to the target, the electron beam enters the objective lens with relatively high energy and is narrowly focused, and then the electron beam irradiates the target with an accelerating voltage of -3 kV. be done. As a result, the electron beam can be narrowly focused onto the target, and damage to the target can also be avoided. In the case of an ion beam, the same effect as that of an electron beam can be obtained by forming a deceleration electric field between the objective lens and the target.

However, in the device using the decelerating electric field described above, if a secondary electron detector is placed between the objective lens and the target in order to detect the secondary electrons generated based on the irradiation of the beam to the target, the ion beam In this case, since the potential of the target is higher than that of the objective lens, the secondary electrons from the target are drawn back to the target, making it impossible to effectively detect the secondary electrons. Furthermore, in the case of an electron beam, since a high voltage is applied to the target, the secondary electrons are accelerated with high energy and ejected, and enter the detector, resulting in rapid deterioration of the detector. For this reason, a charged particle beam device as shown in FIG. 5 was devised. This figure shows an improved ion beam device, in which 1 is the ion beam, 2 is the outer electrode 3.4 at ground potential, and the power source 5.
7 is a target, 8 is a deceleration electrode, 9 is a power source for applying a high voltage for a deceleration electric field to the target and the deceleration electrode 8; 10 is a microchannel plate or the like placed in the space between the target 7 and the deceleration electrode 8;
It is a secondary electron detector.

With this configuration, the secondary electron detector is arranged in the equipotential space between the target 7 and the deceleration electrode 8, so that the secondary electron detector generated by the ion beam irradiation on the target 7 is The electrons are not returned to the target 7, but are directed towards the secondary electron detector by the collection field applied to the detector. Note that the distance between the deceleration electrode 8 and the target 7 is set as much as possible in order to prevent the focusing of the ion beam from being disturbed due to the equipotential space between the deceleration electrode 8 and the target 7. It needs to be short. In view of this requirement and the need to secure a space for arranging the secondary electron detector, the shape of the deceleration electrode 8 is formed into a cone shape with the center convex toward the target side.

Although not shown, in the case of an electron beam device, a deceleration electrode is placed between the target and the objective lens, and a secondary electron detector is placed in the equipotential space between the target and the objective lens. , the secondary electrons generated from the target are not accelerated with high energy, and rapid deterioration of the detector is prevented.

Now, when considering the secondary electron detection efficiency in the configuration shown in FIG. 5, this efficiency is expected to vary depending on the energy of the secondary electrons. The inventor calculated the trajectory of secondary electrons generated from a target and directed toward a secondary electron detector. FIG. 6 shows the result, and the same components as in FIG. 5 are given the same numbers. With this configuration, the deceleration electrode 8 has the same potential as the target 7, and the microchannel plate 10 has a secondary electron absorption voltage.
100v is applied. Of the secondary electrons generated from the ion beam irradiation point P, the trajectory Tl shown by the solid line is 2e
Secondary electron with energy of V, orbit T2 shown by dotted line is 4
It is a secondary electron with an energy of eV. As is clear from this figure, secondary electrons with a small emission angle (emitted at an angle close to the optical axis O) collide with the shield member 11 of the microchannel plate 10, etc., and cannot efficiently enter the microchannel plate.

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 with excellent secondary electron detection efficiency.

[Means for Solving the Problems] A charged particle beam device based on the present invention includes a focusing lens for focusing a charged particle beam generated from a charged particle beam generation source and means for forming a deceleration electric field between the focusing lens and the target; an auxiliary electrode disposed between the target and the focusing lens and having substantially the same potential as the target; The present invention is characterized in that it includes a secondary electron detector disposed between the auxiliary electrode and the auxiliary electrode, and a power supply means for applying a negative minute voltage to the target to the auxiliary electrode.

[Embodiment] FIG. 1 shows an ion beam apparatus which is an embodiment of the present invention. The difference between the apparatus shown in FIG. 1 and the apparatus shown in FIG.
2 is provided. FIG. 2 shows the results of calculating the trajectory of secondary electrons when -2V is applied to the deceleration electrode 8 with respect to the target 7. The structures of the deceleration electrode 8 and the microchannel plate 10 are the same as those shown in FIG.
Of the secondary electrons, the orbit Tl shown by a solid line is a secondary electron with an energy of 2 eV, and the orbit Tz shown with a dotted line is a secondary electron with an energy of 4 eV.

As is clear from this figure, even secondary electrons with a small emission angle (emitted at an angle close to the optical axis O) can efficiently reach the microchannel plate 10 without colliding with the shield member 11 of the microchannel plate 10. It is incident. That is, the secondary electrons with a small emission angle are returned to the target direction by the negative potential applied to the deceleration electrode 8, and are returned to the microchannel plate 1.
This makes it possible to make an injection into 0. Note that this is not limited to the case where a microchannel plate is used as the secondary electron detector, and the same effect can be obtained by using a secondary electron detector using a combination of a scintillator and a photomultiplier. .

FIG. 3 shows another embodiment of the invention. In this embodiment, 15 is a control device such as a computer, 16 is a storage means such as a ROM, and 17 is an input means such as a keyboard. Here, since the energy distribution of the secondary electrons generated from the target differs depending on the ion species and energy of the ion beam to be irradiated, the storage means 16 stores the ion species to be used and the ion beam to be irradiated to the target. The optimum voltage to be applied to the power supply 12 is stored in accordance with the acceleration voltage. When the ion species and accelerating voltage are input through the input means 17, the control device 15 reads out a voltage corresponding to the ion species and accelerating voltage from the storage means, and controls the power supply 12 to obtain this voltage.

FIG. 4 shows another embodiment of the invention. In the figure, 21 is a control device such as a computer, 22 is an amplifier for amplifying the output signal of the microchannel plate, and 22 is a sweep circuit. The control device 21 controls the sweep circuit 22 to generate a sawtooth wave from the control circuit 22, thereby repeatedly sweeping the output voltage of the power source 12 over a predetermined range. As this voltage sweeps, the detection signal of the microchannel plate 10 changes. This detection signal is supplied to the control device 20, and the control device 20 detects the voltage of the power supply 12 when the detection signal is maximum. Thereafter, the control device 20 controls the voltage of the power source 12 to be the value at the time of the detected maximum detection signal.
The output signal of the sweep circuit 22 is fixed.

Although the embodiments of the present invention have been described above using an ion beam device as an example, the present invention can also be applied to an electron beam device. In the case of an electron beam device, the polarity of the voltage applied to the deceleration electrode 8 is reversed. In the case of this electron beam device, it is preferable to use an electromagnetic lens as the objective lens.

Further, although a cone-shaped electrode is used as the deceleration electrode 8, a parallel plate-shaped electrode may also be used. Furthermore, a high voltage is applied to the target 7 and the deceleration electrode 8, and the potential of the emitter that generates ions and electrons is set to the ground potential. may be applied.

[Effects] As detailed above, the present invention can improve the detection efficiency of secondary electrons with a simple configuration. Furthermore, the apparatus can be set in an optimal state for the type of ion beam to be irradiated to the target and the accelerating voltage of the ion beam and electron beam.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the trajectory of secondary electrons based on the present invention, and FIG. 3 is a diagram showing an example of the present invention. FIG. 4 is a diagram showing another embodiment of the present invention, FIG. 5 is a diagram showing a conventional device, and FIG. 6 is a diagram showing the trajectory of secondary electrons in the conventional device. 1...Ion beam 2...Objective lens 3.4
...Outer electrode 5...Lens power source 6...Intermediate electrode 7...Target 8...Deceleration electrode
9... Deceleration power source 10... Micro channel plate 12... Power source 15... Control device 16... Storage means 17... Input means 2
0...Control device 21...Amplifier 22...
sweep circuit

Claims (1)

[Scope of Claims] (1) A focusing lens for focusing an accelerated charged particle beam generated from a charged particle beam generation source, a target to which the charged particle beam is irradiated, and a combination of the focusing lens and the target. means for forming a decelerating electric field between the targets and the focusing lens; an auxiliary electrode located between the target and the focusing lens and having substantially the same potential as the target; A charged particle beam device comprising a secondary electron detector and a power supply means for applying a minute negative voltage to the target to the auxiliary electrode. (2) The electron beam device according to claim 1, wherein the charged particle beam is an electron beam, and the focusing lens is an electromagnetic lens. (3) The charged particle beam device according to claim 1, wherein the charged particle beam is an ion beam, and the focusing lens is an electrostatic lens. (4) A focusing lens for focusing the accelerated charged particle beam generated from the charged particle beam source, a target to which the charged particle beam is irradiated, and a decelerating electric field between the focusing lens and the target. an auxiliary electrode disposed between the target and the focusing lens and having substantially the same potential as the target; and a secondary electron detector disposed between the target and the auxiliary electrode. , a power supply means for applying a negative minute voltage to the target to the auxiliary electrode, and a storage means for storing a value of the minute voltage to be applied to the auxiliary electrode according to the energy of the charged particle beam irradiated to the target. , a control means for reading a corresponding voltage value from the storage means based on the designation of the energy of the charged particle beam and controlling the power supply means. (5) A focusing lens for focusing the accelerated ion beam generated from the ion beam source, a target to which the ion beam is irradiated, and a deceleration electric field formed between the focusing lens and the target. an auxiliary electrode disposed between the target and the focusing lens and having substantially the same potential as the target; a secondary electron detector disposed between the target and the auxiliary electrode; a power supply means for applying a negative microvoltage to the electrode with respect to the target; a storage means for storing a value of the microvoltage to be applied to the auxiliary electrode according to the ion species and energy of the ion beam irradiating the target; An ion beam apparatus comprising: control means for reading a corresponding voltage value from the storage means and controlling the power supply means based on designation of ion species and energy of the ion beam. (6) A focusing lens for focusing the accelerated ion beam generated from the ion beam source, a target to which the ion beam is irradiated, and a deceleration electric field formed between the focusing lens and the target. an auxiliary electrode disposed between the target and the focusing lens and having substantially the same potential as the target; a secondary electron detector disposed between the target and the auxiliary electrode; A power supply means for applying a negative microvoltage to the target to the electrode, a means for sweeping the microvoltage, and an output signal of the secondary electron detector are supplied, and as the microvoltage is swept, the detection is performed. A charged particle beam device comprising: a control means for detecting a microvoltage at which a signal becomes maximum, and setting the microvoltage so that the detected signal intensity becomes maximum.