JPS63195941A - Electric field radiation type charged particle source - Google Patents

Abstract

PURPOSE:To enable very exact axis alignment between an ion source (emitter) and an EXB (E cross B) mass filter by applying a voltage, which is proportional to a square root of acceleration voltage VACCXextraction voltage VEXT, to an electrostatic deflector for alignment so that axis alignment is performed. CONSTITUTION:A deflection voltage generating circuit 40 receives signals which correspond to an acceleration voltage VACC and an extraction voltage VEXT from an acceleration voltage source 1 and an extraction voltage source 2, respectively, and it applies a voltage, which is proportional to (VEXT)<-1/2>.(VACC)<-1/2>, to an electrostatic deflector for alignment 7 (unillustrated) so that axis aligning regulation (gun alignment) is performed. Since the voltage proportional to VEXT<-1/2>.VACC<-1/2> is generated from the deflection voltage generating circuit 40 and applied to the electrostatic deflector for alignment 7 so that axis alignment is performed, exact alignment can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a field emission charged particle source, and more particularly to alignment between an ion source (emitter) and an EXB (pronounced E-cross and -) mass filter. This invention relates to a field emission type charged particle source that can perform extremely accurate calculations.

(Prior art) A field emission type charged particle source applies an ultra-high accelerating voltage (for example, about 100 KV) to an emitter serving as an ion source.
When an extraction voltage (e.g., 10 KVPj degrees) is applied between the emitter and the extraction electrode (extractor), particles near the emitter tip are ionized and emitted by the electric field radiation effect based on the high electric field generated at the emitter tip. do[
It is j. This kind of electric field g! Ion implantation is performed by irradiating a sample with a charged particle beam emitted from an i-shaped charged particle source.
Ion etching, beam writing, etc. can be performed.

FIG. 2 is a diagram showing a conventional configuration of a charged particle beam device using a liquid metal ion source. In the figure, 1 is an acceleration voltage source that generates an acceleration voltage VACC, and 2 is an extraction voltage VEx.
3 is an extraction voltage source that generates T, and 3 is a condenser lens voltage source that generates a condenser lens voltage. 4 is an emitter (ion source) to which an accelerating voltage VACC is applied, 5 is an extractor to which one end of the extraction voltage source 2 is connected, and 6 is a lens to which one end of the condenser lens voltage source 3 is connected. Electrode 6' is the ground electrode, electrode 5゜6.6
' forms a pi-potential lens and becomes a condenser lens 50. , the positive polarity output sides of the voltage sources 1°2.3 are commonly connected. Reference numeral 7 denotes a two-stage alignment deflector arranged below the lens electrode 6 for axial alignment. The portion surrounded by the broken line described above constitutes the field emission type charged particle source 10.

11 is a beam current detection annular aperture for detecting charged particle beam current; 12 is the beam current detector 1;
This is an amplifier that amplifies the output of 1 and sends it to a subsequent circuit (not shown). 13 is an alignment electrode for aligning the magnetic field axis of the EX8 mass filter, and 14 is an EX that cuts unnecessary charged particles by bending their orbits among the charged particles passing through.
B mass filter, 15 is EX [3 mass filter electric field electrode, 16 is avertise (aperture) to cut unnecessary beams
It is. 17 is a two-stage objective lens alignment deflector, and 18 is a stigmameter.

1, an objective lens; 20, an objective lens voltage source that generates a voltage to be applied to the objective lens 19; 21, an objective lens aperture; 22, a deflector that two-dimensionally deflects the charged particle beam; 23; is the sample that is irradiated with the charged particle beam.

In the device configured in this way, the charged particle beam emitted from the emitter 4 is accelerated by the accelerating potential, focused by the condenser lens 50, and then EXB? filter 14. After unnecessary ions are removed by the aberration 1116, the light is focused by one objective lens, deflected by the deflector 22, and then irradiated onto the sample 23.

By the way, in the apparatus shown in the figure, the EXB mass filter 14 and the emitter 4. Extraction electrode 5. Lens electrode 6. Ground electrode 6
The axis of the ion gun is aligned with the axis of the ion gun. Then, the voltage of the condenser lens voltage source 3 applied to the electrode of the condenser lens 6 is controlled so that the crossover point is exactly at the center of the EXB mass filter 14.

Conventionally, the voltage applied to the electrostatic deflector of the alignment deflector 7 was simply made proportional to the accelerating voltage VACC. For example, the applied voltage set at VA c c of 100 KV was set so that when VA c c reached 50 KV, it became 1/2 of that of 100 KV.

(Problem to be Solved by the Invention) However, unless the voltage applied to the electrostatic deflector of the alignment deflector 7 is varied not only by the accelerating voltage VACC but also by the extraction voltage VEX, it will not be possible to maintain the same voltage. It has been found that accurate wJ alignment of the beam alignment is not possible. The reason for this will be explained below.

Now, the trajectory of the charged particle beam emitted from emitter 4 is
As shown in the figure. As shown in the figure, the charged particle beam Bi emitted from the emitter 4 is emitted at an angle θ with respect to the central axis Z.
It is assumed that the condenser lens 6 of the accelerating section receives a focusing action, the deflectors 7a and 7b of the alignment deflector 7 deflect the light in two stages, and the light is incident on the EXB mass filter 14.

Here, if the distance from the ExB mass filter 14 to the main surface of the condenser lens 50 is K11, and the distance from the emitter 4 to the main surface of the condenser lens 50 is 2, then the magnification M
is expressed as 2 in Kl/.

The angular magnification m at this time is given by the following equation.

11 (1/Ml εX7 ACC...(
1) Here, VεX is the above-mentioned extraction voltage, and VACC is the acceleration voltage. Now, assume that the beam deflection by the alignment deflector is as shown in FIG. Here, [)d
is the deflection distance, 30a and 30b are the deflection electrodes, d is the distance between the deflection electrodes, and l! is the length of the deflection electrodes 30a and 30b, L
Is it a deflection? ! l! It is the distance from the center of the pole to the point where the deflection of [)d is obtained.

The deflector flDd is given by the following equation.

Dd −(/L/d) ・(Vd/VA c c
)...(2) Here, Vd is the voltage between the deflection electrodes.

As is clear from formula (2), since / and d are constants, (IIL/d) is set as Kt (constant) (and Dd = Kt (Vd /VA c c ). From this, Vd is V (1-VA CC-Dd /Kt -(3
) can be expressed as Deflector MD (l is proportional to the angular magnification, so with 2 as a constant, Qd - Kz ・l ... (4
) can be expressed as

By substituting equations (1) and (4) into equation (3), the deflection inter-electrode voltage Vd becomes as shown in the following equation.

Vd=(1/Kx)VACC-Kz・(1/M)-
l: x Ding ^ cc = (K2/to 1)・(1/M) x EXT ACC reference V ^ cc
0°0 Ku 5) Here, (K2/Kl)・(
Since 1/M) is a constant, (K2/Kt) ・(1/M)-! (constant)
Then, equation (5) is further simplified as Vd=Kx EXT ACCXVA c
c...(6).

From equation (6), the following can be found. In other words, in the past, Vd − in equation (6) was set as 3·VACC, and the interelectrode voltage Vd was controlled simply as being proportional to the accelerating voltage·VAcC. It can be seen from equation (6) that this alone was insufficient. Further EXT
This indicates that it is necessary to add ACc as a correction term. Equation (6) is further simplified as follows: Vd = Kx ・F y]] ・C ■ T d τ ... (7)
becomes.

The present invention has been made with these points in mind, and
The purpose is to realize a field emission particle source in which alignment between the ion source and the ExB mass filter can be performed very precisely.

<Means for Solving the Problems> The present invention for solving the above-mentioned problems applies an extraction voltage εX7 between the emitter to which the accelerating voltage VACC is applied and the extraction electrode to emit charged particles from the emitter, and
In a field emission charged particle source in which a bipotential condenser lens is provided by arranging a lens electrode and a ground bridge under an extraction electrode, an alignment deflector is placed between the condenser lens and the next stage optical system. When performing axis alignment between the emitter and the next stage optical system, the electrostatic deflector for alignment is CTvY lower
This is characterized in that the axis alignment is performed by applying a voltage proportional to τ.

(Operation) A voltage proportional to CvTT lower×C■Td τ is applied to the electrostatic deflector for alignment.

<Examples> Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

Components that are the same as those in FIG. 2 are given the same reference numerals.

In the figure, reference numeral 40 receives signals corresponding to the acceleration voltage VACC and the extraction voltage VEXT from the acceleration voltage source 1 and the extraction voltage source 2, and sends C animals to an electrostatic deflector (not shown) of the alignment 7. This is a deflection voltage generation circuit that performs axis alignment adjustment (gun alignment) by applying a voltage proportional to [C]].

According to the device configured in this manner, a voltage proportional to FTvT ? Therefore, axis alignment can be performed accurately. still,
The deflection voltage generation circuit 40 generates an ultra-high acceleration voltage VA c c
input, so it is necessary to ensure insulation from the surrounding area. In order to achieve relatively reliable insulation, it is preferable to take measures such as transmitting signals through optical fibers.

For example, a square root calculator used in an analog computer or the like can be used as a means for generating a signal such as [F animals]]. A multiplier can be used for the multiplication below.

Although the above-described embodiment is a case in which the present invention is applied to axis alignment with an EXB mass filter, the present invention can be similarly applied to a case where the next-stage optical system is an objective lens.

(Effects of the Invention) As described above in detail, according to the present invention, the alignment tt? By changing the voltage applied to the electric deflector in proportion to F τ, the axis alignment between the emitter and the ExB mass filter can be achieved extremely accurately. A field emission type charged particle source can be realized.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a diagram not showing a conventional charged particle beam device, Fig. 3 is a diagram showing the beam trajectory of the charged particle beam, and Fig. 4 is a diagram showing the instruction direction. FIG. 2 is an explanatory diagram of beam deflection by the device. 1... Accelerating voltage source 2... Extracting voltage source 3.
...Condenser lens voltage source 4...Emitter 5...Extraction electrode 6...
・Condenser lens 7... Alignment deflector 10... Field emission charged particle source 11... Beam current detector 12... Amplifier 13.
... Alignment electrode for magnetic field axis alignment 14 ... EXB mass filter 15 ... ExB mass filter electric field electrode 16 ... Aperture 17 ... Alignment deflector for objective lens 18 ...
One stigma meter...Objective lens 20...↑U pressure source for objective lens 21...Objective lens aperture 22...Deflector 23...Sample 30a,
30b...Deflection electrode 40...Deflection voltage generation circuit 50...Condenser lens patent applicant Japan Electronics Co., Ltd.
Ceremony for the meeting Patent attorney
Ijima knee 1 person tube 1 4 times 1J [I speed voltage source 2 □ Extraction voltage source 3, condenser lens voltage RF 41 emitter 5, extraction electrode 6I lens 11 cup 6゛・embedded l soft 501 capacitor Figure 3

Claims (1)

[Claims] An extraction voltage V_Ex_T is applied between the emitter to which the accelerating voltage V_A_C_C is applied and the extraction electrode to emit charged particles from the emitter, and a bipotential condenser lens is provided by placing a lens electrode and a ground electrode under the extraction electrode. In a field emission type charged particle source with 1. A field emission type charged particle source, characterized in that the field emission type charged particle source is configured to perform axis alignment by applying a voltage proportional to √(V_Ex_T)×√(V_A_C_C) to an electrostatic deflector for use in the field.