JPS6364254A - Charged particle optical system - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a charged beam device capable of handling ions or electrons, and in particular, to a charged beam device capable of handling ions or electrons, and particularly to a charged beam device capable of selecting and selecting specific ions or electrons within the same optical system and the same vacuum. This invention relates to a charged particle optical system suitable for modulation.

[Conventional technology]

Conventionally, devices with mass separation and blanking (modulation) functions have been described in Applied Physics, Vol. 53, No. 8 (198
4) On pages 704 to 708, a maskless ion implanter with a mass analyzer is discussed. In the conventional device, in order to perform mass separation and blanking only for specific ions, an EXR (orthogonal electric field/magnetic field) type mass separator is used, and the above function is achieved by keeping the magnetic field constant and changing only the electric field. I'm here. However, no consideration was given to an optical system that includes electrons, which have an extremely small mass in addition to ions.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into account the function of mass-separating ions and electrons and blanking (modulation), and the conventional technology cannot mass-separate and blank both ions and electrons. The problem was that it was difficult.

The purpose of the present invention is to use a charged particle source capable of extracting positively and negatively charged particles from the same emission source to
The objective is to obtain a charged particle optical system that can perform mass separation (selection) and blanking (modulation) of electrons.

[Failure to solve the problem]

The above purpose is to simultaneously control not only the electric field but also the strength of the magnetic field, as seen in the EX1'3 model used in the conventional technology, and to separate the mass of not only ions but also electrons. (selection) and blanking (modulation)).

[Effect]

Ions and electrons can be shared using a charged particle optical system.
Hexaquantal separation Z; requires mass separation from ions to electrons. At present, the ExB type particle separator is most commonly used, and the particle un is expressed from the energy cV of charged particles as follows.

However, E: electric field strength, B: magnetic flux density.

For example, the mass ratio of electrons to Ga ions is 7.8X10-
It becomes 6. In this case, the ratio of the electric field and magnetic flux density is Es/F:aa (E.

: electric field when using electrons, EOa: electric field when using Ga ions), Be/Baa (r3e
: The magnetic flux density when electrons are used, the magnetic flux density when Baa:Ga+ is used) is given as follows.

(1) When 11 is constant, e (2) When g is constant, In the case of (1), YIJ and polar voltage v1 applied to the parallel plate to create an electric field when separating Ga ions. 10
In the case of electrons, Vp is 3.5 KV.

This value is a voltage that is difficult to control if blanking is to be performed. In addition, in the case of (2), nG in Ga ions
If a is 1000 Gauss, 11e is 2,8
It becomes Gauss. Magnetic flux density becomes smaller when it comes to electrons, so it can be easily obtained. Therefore, it is possible to make B variable and control it. That is, with a control method like (2),
If blanking is performed using an electric field, it is possible to perform mass separation and blanking in a charged particle optical system that uses both ions and electrons. In addition, a method of controlling magnetic and electric fields can be considered as a means of performing mass separation, and even if blanking zero fat is added to this method, it can constitute the goal of this book.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The figure shows a charged particle optical system that extracts ion particles from the liquid metal ion electron source 25 and performs ion etching, ion implantation, etc.

The charged particle optical system of the present invention is a liquid metal ion source 25.
．． It consists of a 1ζxn type mass divider, an objective lens 26, and a deflection electrode 15. Liquid metal ion electron source 25
1 needle tip, 2 crucibles, 4.17p raw materials for ionic species
It is composed of a lid 3 for evaporation cutting of the material 4, an extraction electrode 5, an intermediate electrode 6, and a rear acceleration/deceleration electrode 7. still,
Here, the chip heating function is omitted. The EXTB type mass separator consists of a magnetic path 9 made of a material such as iron, a magnet consisting of a coil 8 for generating an electric field, and a parallel plate electrode 10 that generates an electric field in the cross direction; In addition, a blanking aperture was provided directly below the reproductive organs to remove unnecessary ions or electrons.

Furthermore, there are 3 lenses in the objective lens 26? l pole 12,13゜1
4, the deflection electrode 15 is provided with a parallel plate type two-dimensional deflector. The ion beam 17 extracted by the power sources 18, 19, and 2.0 is connected to the ExnJljd field control circuit 23 and the electric field control circuit and blanking circuit 22 for E
The desired current and voltage are applied, and only the desired ions are
It passes through the blanking aperture 11 and passes through the objective lens 26.
A spot is imaged at a desired position r on the sample] 6 using the deflection electrode 15.

The values of the electric field and magnetic field at this time are controlled so as to satisfy the above formula (]). Blanking (modulation) is parallel plate electrode 1
This is carried out by applying a voltage to the aperture 11 such that no other ions are emitted from the aperture 11. In this case, the @ field method is also possible, but high-speed drive! FIJ is possible 5
Electric blanking is desirable.

Next, when obtaining an electron beam, switch the polarity of the power source 19°20 to the opposite sign as shown in the figure, extract the electron beam, control the magnetic field and electric field so as to satisfy equation (1), and set the aperture 11 pass. At this time, there are two possible methods: controlling the magnetic field and electric field, and controlling the magnetic field by keeping the electric field constant when the ions are separated, and either method is possible. The electrons that have passed through the aperture 11 can be focused on a desired position on the sample by the objective lens 26 and the deflection electrode 15, making it possible to perform image observation, analysis, and the like.

At this time, since the lens 26 and the deflector 15 are of an electrostatic type, a spot is focused on the same location as the ions. The blanking function can be modulated at desired timing by controlling the electric field of the T.XB type mass separator with the EXB type electric field control circuit and blanking circuit 122.

In addition, when controlling the magnetic field as explained above, it is recommended to provide a reference current and control the current value so that it always increases or decreases from the base current value to a desired current value to prevent the influence of hysteresis of the magnetic field. Desirable.

Furthermore, in order to completely eliminate the effects of magnetic field hysteresis, an alternating magnetic field is applied when the magnetic field changes.

A possible method is to set the desired magnetic field by gradually attenuating and converging to the desired magnetic field. FIG. 2 shows an embodiment for embodying the above method. FIG. 3 shows waveforms of various parts for explaining the circuit configuration of FIG. 2. In FIGS. 2 and 3, when a signal for changing the magnetic field strength is input from the control circuit 36 to the magnetic field strength setting circuit 35, the output voltage changes as shown in FIG. 3(a). That is, at time t1, the ion selection mode is changed to the electron selection mode. In this case, the electron selection mode is the magnetic field strength,
The case where the electric field is zero is shown, and when the electronic beam Is "ON", the electric field must also be zero. That is, in this case, the optical system is equivalent to the optical system of a normal electron beam device. The above-mentioned output voltage is input to a differentiating circuit 34 and an adding circuit 32. The differentiating circuit 3.1 generates a waveform as shown in the third waveform (b). Further, the output waveform is input to the multiplier 31 together with the output signal from the oscillator 30 (FIG. 3(C)), and
) to obtain the output signal. By inputting the output signal to the force calculator 32, the voltage waveform shown in FIG. 3(e) is formed.

A current similar to that in (e) is input to the coil 8 via the constant current circuit. When the coil current (FIG. 3(f)) is input to the coil, the magnetic flux density changes from state (a) to state (b) as shown in FIG. This behaves as if the alternating magnetic flux is attenuated and converged to a desired magnetic field strength. Although FIGS. 3 and 4 show the electron selection mode from the ion selection mode, the above explanation can also be applied when switching from the electron selection mode to the ion selection mode or from the ion selection mode to another ion selection mode. Similarly, the magnetic field strength changes,
A magnetic circuit that is completely unaffected by magnetic field hysteresis can be realized. Also, when the magnetic field strength is other than zero, the electric field is expressed as (
If 1) is satisfied, specific ions can pass through the aperture 11. still.

Fig. 2 shows one embodiment, and Fig. 3(f)
A path 11 that provides a current waveform like this to the coil 8 does not depart from the scope of the present invention. It is also possible to consider a method of controlling the magnetic field strength by combining permanent magnets without using the coil 8, but this method is also within the scope of the present invention. Furthermore, even if the control circuit system is controlled by a computer, it is equivalent to the present invention. As for ion and electron sources, functions similar to those of the present invention can be obtained even with an ion source such as a dioplasmatron, and sources other than liquid metal ions and electron sources do not depart from the present invention.

As described above, according to the present invention, it is possible to realize a charged particle optical system that can select specific ions or electrons and simultaneously modulate a charged t-beam.

〔Effect of the invention〕

According to the present invention, ions and electrons can be obtained from the same optical system, and the following new effects can be obtained.

(1) Specific ions and electrons are extracted alternately and independently from the same source, and by utilizing the characteristics of each, the performance of the device can be improved.

(2) As an effect of (1) above, it is possible to perform processing and analysis using ions, and at the same time, it is possible to obtain scanning electron microscope images using a sub-beam. This makes it possible to determine and shape ll'16.

(3) Three-dimensional observation using ions and electrons alternately;
Dimensional analysis becomes possible.

(4) It can be applied as a means of semiconductor failure analysis using ions and electrons.Ion etching is used to open holes on the surface and on electrodes below 7, and irradiation with an electron probe is used to evaluate the performance of the device. It is possible to modify the bit relief.

(5) Application to maskless ion implantation 'Ati'f' and 'i' with one beam matching function becomes iJ function.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the overall configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing the device configuration of an embodiment for removing field hysteresis and controlling magnetic field strength, and FIG. The output waveforms of each section in FIG. 2 are shown, and FIG. 4 shows the changes in magnetic flux density and degree for one coil flow when the magnetic field is controlled to the same as shown in FIG. 3. 1-...acicular tip, 2...rotsul instep, :3...lid,
4...raw material for ionic species, 5...drawer? ! pole, 6
...Middle 1111 electrode, 7... Acceleration/deceleration later;;! Pole, 8...coil, 9...magnetic path. 10.. Prison parallel electrode, 11.. Aperture, 15.. Deflection "mandrel," (5. Sample, 17.. IonBee 1z, 2
2... Electric field control circuit and blanking circuit for EXB, 2
3... EXB magnetic field control circuit, 30... Oscillator, 3
1...#) Calculator, 32... Adder, 33... Constant current circuit, 34... Differential circuit, 35... Magnetic field strength setting circuit; 36... Control circuit.・-＼ 11 people Patent attorney Ogawa Takumi JIS No. 20 Mao No. 4 Plate porcelain banquet 1. B

Claims (1)

[Claims] 1. In a charged particle optical system having a charged particle source capable of extracting positively and negatively charged particles from the same emission source, a means for controlling the magnetic field strength within the optical system and a direction perpendicular to the magnetic flux. A charged particle optical system characterized by having means for controlling electric field strength, and having functions for selecting specific ions or electrons and beam modulation. 2. The charged particle optical system according to item 1, characterized in that mass separation is controlled only by a magnetic field. 3. The charged particle optical system according to items 1 and 2, characterized in that the magnetic field is controlled by increasing or decreasing the magnetic field based on a reference magnetic field. 4. The charged particle optical system according to items 1 and 2, further comprising means for applying an alternating magnetic field when setting the magnetic field, gradually attenuating the alternating magnetic field, and converging it to a desired magnetic field. . 5. The charged particle optical system according to item 4, wherein the electron beam is selected so that the magnetic field strength is zero. 6. The charged particle optical system according to any one of items 1 to 5, characterized in that blanking (modulation) of the charged beam is controlled by an electric field.