JPH0232746B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charged particle beam device, and more particularly to a charged particle beam device that selects and uses a specific ion from a plurality of ions.

Ion beam exposure using a metal ion source can expose fine patterns because the diffusion of ions within the photoresist is smaller than exposure using an electron beam. Maskless ion implantation is also possible by narrowing down metal ions and irradiating them onto a desired fine region on a semiconductor wafer. Therefore, microfabrication using ions is attracting attention as a future technology for VLSI manufacturing, and research on metal ion sources suitable for this is actively conducted in various fields. This type of ion source usually places the substance to be ionized in a reservoir, heats the substance directly or indirectly by heating the reservoir, turns the substance into a liquid, and sharpens the liquid substance to a tip with a diameter of about 1 μm. ionized by a strong electric field formed near the tip.
Such an ion source requires heating the substance to make it liquid, and therefore a substance with a high melting point cannot be used alone as an ionizing substance. As a result, the melting point of an alloy is generally lower than the melting point of the substance that makes up the alloy, so in order to obtain ions of a substance with a high melting point, the alloy containing that substance is placed in the above-mentioned reservoir and heated to form a liquid. There is. For example, if you want to obtain ions of metal element (B) with a melting point of 2000°C or higher, use Pt alloy with platinum (Pt).
-B (melting point: 795°C), heat the Pt-B to make it liquid, generate Pt ions and B ions using a strong electric field, and then move the ion beam containing a mixture of both ions into an orthogonal electric and magnetic field. The B ions are introduced into a Vienna-type charged particle filter consisting of B ions to obtain only B ions.

FIG. 1 shows an example of a charged particle filter that uses the above-described orthogonal electric and magnetic fields to selectively pass charged particles of a predetermined energy and mass. In the figure, 1 is a charged particle beam, and the charged particle beam 1 is condensed to a constant beam diameter by an entrance aperture plate 2 having an opening, and is formed by magnetic poles 3, 4 and electrodes 5, 6. Proceeds through magnetic and electric fields. The electric and magnetic fields are set so that only charged particles having a predetermined energy and mass among the charged particle beams incident on this field pass through the opening 8 of the slit plate 7 provided below the field. . Particles with other energy or mass cannot pass through the opening 8 and collide with the slit plate 7. This filter is basically constructed so that the electric field and the magnetic field are uniform and their directions are perpendicular to each other within the range in which the charged particle beam travels. If the strength of this electric field is 〓 (vector) and the magnetic flux density is 〓 (vector), then −〓＝〓 ₀ ×〓 …(1) can be set. Here 〓 ₀ is the velocity of the charged particle. In such a field, charge Q, mass M, velocity 〓
Considering the force exerted on the charged particle, the force e due to the electric field is: e=Q〓 The force b due to the magnetic field is: b=Q〓×〓, and the force exerted on the charged particle is: 〓=〓e+〓b. However, considering equation (1), 〓=Q〓+Q〓×〓 =Q{〓+(〓 ₀ +△〓)×〓} =Q×△〓×〓. However, 〓=〓 ₀ +△〓. Therefore, 〓
=〓 When _0〓 = 0, and the charged particle does not receive any force, so it moves straight. By arranging the opening 8 of the slit plate in this direction, only charged particles with == ₀ can be taken out of the filter. On the other hand, the velocity 〓 can be written as |〓|=√2 using the kinetic energy U of the charged particle. If |〓 ₀ |=v ₀ and v ₀ =√2 _{0 0} , charged particles with M≠M ₀ or U≠U ₀ will generally have v≠v ₀ and cannot pass through the filter.

The present invention is capable of obtaining only desired specific ions without troublesome adjustment work in a charged particle beam device using a charged particle filter as described above.
The purpose is to provide a charged particle beam device with improved operability.

Therefore, the present invention includes a pair of electrodes and a magnetic pole for forming a magnetic field in a direction perpendicular to the electric field between the pair of electrodes, and the electric field and the magnetic field are orthogonal to each other to generate a charged object having a predetermined energy and mass. a charged particle filter for sorting particles, and a charged particle filter disposed between the magnetic field,
a detector for detecting the strength of the magnetic field; an output signal of the detector and a signal for setting the strength of the magnetic field;
means for generating the difference signal; means for controlling the magnetic field between the magnetic poles in response to the difference signal; a variable DC signal source for driving the magnetic field detector; and a drive signal for the detector. The present invention is characterized by comprising a sweep signal generation source that generates a periodic sweep signal for the purpose of detecting the magnetic field, and a switch means for controlling the supply of the output signal from the sweep signal generation source to the magnetic field detector.

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

FIG. 2 shows an ion beam apparatus based on the present invention, 11 is an ion source, and the ion source 1
1, for example, the eutectic alloy Pt-B is ionized and accelerated. The accelerated Pt ions and B
The ion beam consisting of ions enters a charged particle filter consisting of an entrance slit plate 12, a pair of magnetic poles 13A and 13B, a pair of electrodes 14A and 14B (only 14A is shown), and an exit slit plate 15.
16A and 16B are excitation coils for generating a magnetic field between the magnetic poles 13A and 13B, and an excitation current is supplied from an excitation power source 17 to the excitation coils. Reference numeral 18 denotes a Hall element disposed in a space between the magnetic poles 13A and 13B, and an adder 19 is connected to the element 18.
A current is supplied from the element, and a voltage signal generated in the element according to the current value and the strength of the magnetic field between the magnetic poles is amplified by the amplifier 20 and then supplied to one terminal of the differential amplifier 21. Ru. The differential amplifier 2
A reference voltage from a variable power supply 22 is supplied to the other terminal of the differential amplifier 1, and the differential amplifier generates two types of differential voltages. The differential voltage is supplied to the excitation power source 17, which is controlled by the differential voltage, and the coil 16 is controlled so that the differential voltage becomes 0.
Controls the excitation current supplied to A and 16B. As a result, the voltage according to the desired magnetic field strength can be adjusted by the variable power supply 2.
2, a desired magnetic field can be obtained between the magnetic poles. An adder 19 that supplies current to the Hall element 18 adds the current from the variable power supply 23 and the sawtooth wave current from the sawtooth wave generation circuit 24.

A predetermined voltage is applied to the electrodes 14A, 14B from a power source (not shown), and the magnetic poles 13A, 1
3B is formed, and the incident beam is selected according to the strength of the electric field and magnetic field, and only ions with a specific mass and energy pass through the opening of the exit slit plate 15. . A portion of the ions that have passed through the opening of the exit slit plate 15 are detected by a ring-shaped ion detector 25.
The detection signal is amplified by an amplifier 26, differentiated by a differentiation circuit 27, and then supplied to a pulse generation circuit 28. The pulses generated by the pulse generation circuit 28 are supplied to a comparison circuit 29, which generates pulses in response to the pulses from the circuit 28 and the sawtooth wave current from the sawtooth wave generation circuit 24. The pulses from the pulse generation circuit 30 are compared. The output signal of the comparison circuit 29 is supplied to the variable power supply 23 to control the current value from the power supply 23. Note that the current value of the ion beam incident on the exit slit plate 15 of the charged particle filter is supplied to a display device 32 via an amplifier 31.

In the configuration described above, when only B ions are selected from the Pt ions and B ions generated from the ion source 11 by the charged particle filter, the filter applies an electric field and a magnetic field according to the mass and energy of the B ions. The strength is set to . With this setting, approximately B ions pass through the opening of the exit slit 15, but in order to take out the B ions in an optimal condition,
Minor adjustments are made. For this fine adjustment, the sawtooth wave generating circuit 24 outputs signals from -I to + as shown in FIG. 3A.
A sawtooth current varying up to I is generated, and this varying current is added to a constant current from the power source 23 and supplied to the Hall element 18. As a result, the output voltage of the Hall element 18 varies in a sawtooth manner according to the input current, so that the output voltage of the differential amplifier 21, the output current from the excitation power supply 17, and the magnetic pole 13A,
The strength of the magnetic field between 13B also changes in a sawtooth pattern. As the strength of the magnetic field changes, the selection conditions of the charged particle filter also change, and the number of ions passing through the opening of the exit slit 15 changes in accordance with the strength of the magnetic field. FIG. 3B shows the output signal of the ion detector 25, which corresponds to the variation in the amount of the ion beam passing through the opening of the exit slit 15. The output signal of the detector 25 is sent to the amplifier 2
6 and then differentiated in a differentiating circuit 27 to obtain the differential signal shown in FIG. 3C. The differential signal is supplied to the pulse generating circuit 28 to obtain the pulse shown in FIG. 3D, which pulse is generated corresponding to the peak position of the signal shown in FIG. 3B. The pulses are supplied to a comparison circuit 29, which is also supplied with pulses from a pulse generation circuit 30. The circuit 30 generates the pulse shown in FIG. 3E at the center of the sawtooth wave from the sawtooth wave generating circuit 24, that is, when the sawtooth wave reaches 0 level. The comparator circuit 29 determines the time difference between the two types of pulses supplied, generates a signal corresponding to the time difference, and supplies the generated signal to the current power supply 23 of the Hall element. The power supply 23 is controlled so that the signal from the comparator circuit 29 becomes 0, and in the state of the waveform shown in FIG. 3, the current value from the current power supply 23 decreases in accordance with the time difference between the two types of pulses. I am made to do so.
Along with this, the output voltage of the Hall element is reduced, but the excitation current supplied to the coils 16A and 16B by the differential amplifier 21 and the power supply 17 is increased, and finally two types of pulses are generated at the same time. controlled to occur. That is, when the fluctuating sawtooth wave reaches 0 level, the peak of the waveform shown in FIG. 3B is obtained. After such control, the switch 33 is turned off and the sawtooth wave generation circuit 24 is turned off.
By stopping the supply of the sawtooth wave current from the adder 19 to the adder 19, the desired single ion to be sorted can be continuously extracted from the opening of the exit slit 15 with maximum intensity.

In this embodiment, the exit slit 15
Ions shielded by the slit 15 are also detected, and a current corresponding to the amount of ions incident on the slit 15 is amplified by the amplifier 31 and then supplied to the display device 32. A sawtooth wave is supplied as a reference signal from the sawtooth wave generating circuit 24 to the display device 32, and the waveform shown in FIG. 3F is displayed on the display device. It is also possible to manually control the power supply 23 while observing the waveform displayed by the display device 32, or by supplying the output signal from the amplifier 26 to the display device 32 as shown in FIG.
While observing the waveform, turn on the power supply 2.
3 may be controlled manually. Furthermore, the current value from the power supply 23 may be automatically controlled by processing the signal shown in FIG. 3F.

As described above, in the present invention, a detector is arranged between the magnetic fields and detects the strength of the magnetic field, an output signal of the detector and a signal for setting the strength of the magnetic field are supplied, and the difference signal is means for generating a magnetic field between the magnetic poles in accordance with the difference signal; a variable DC signal source for driving the magnetic field detector; and a variable DC signal source for driving the detector. Since the apparatus includes a sweep signal generation source that generates a periodic sweep signal and a switch means for controlling the supply of an output signal from the sweep signal generation source to the magnetic field detector, desired ions can be extracted. Adjustments can be made accurately, easily, and in a short time.

Note that the present invention is not limited to the embodiments described above, and can be modified in many ways.

For example, the strength of the magnetic field was changed in a sawtooth pattern,
It is also possible to change the waveform to another waveform, for example, a sine wave.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a charged particle filter using orthogonal electric and magnetic fields, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 shows each signal waveform in the embodiment of Fig. 2. It is a diagram. 11: ion source, 12: entrance slit plate, 13
A, 13B: magnetic pole, 14A, 14B: electrode, 1
5: Output slit plate, 16A, 16B: Excitation coil, 17: Excitation power supply, 18: Hall element, 19:
Adder, 20, 26, 31: Amplifier, 21: Differential amplifier, 22, 23: Variable power supply, 24: Sawtooth wave generation circuit, 25: Ion detector, 27: Differentiator circuit, 28, 30: Pulse generation circuit , 29: comparison circuit, 32: display device.

Claims (1)

[Claims] 1 comprising a pair of electrodes and a magnetic pole for forming a magnetic field in a direction perpendicular to the electric field between the pair of electrodes,
A charged particle filter that selects charged particles having a predetermined energy and mass using the orthogonal electric and magnetic fields, a detector that is placed between the magnetic fields and detects the strength of the magnetic field, and an output signal of the detector. and means for generating a difference signal, means for controlling the magnetic field between the magnetic poles in response to the difference signal, and for driving the magnetic field detector. a variable DC signal source, a sweep signal generation source that generates a periodic sweep signal to be used as a drive signal for the detector, and controlling supply of an output signal from the sweep signal generation source to the magnetic field detector. A charged particle beam device equipped with a switch means for