JPS63310545A - Mass separator - Google Patents

Abstract

PURPOSE:To prevent beam focusing-characteristic of several kinds of ion beam apparatuses from being deteriorated by making electrical field-distribution spread out along the incidence direction of ion beams similar to magnetic field- distribution spread out between the magnetic electrode plates of a magnetic deflection means. CONSTITUTION:Magnetic electrode plates 5a, 5b of a main electrostatic deflection means facing each other are fixed respectively to the side of the surfaces of insulating plates 9a, 9b facing each other arranged in parallel and also electrode plates 9a, 9b and 8a, 8b composing auxiliary electrostatic deflection means are fixed respectively to an ion beam incidence side and its emission side on the back of the insulation panels. An adequate D.C. voltage is supplied to them to change the electrical field at the end of the main electrostatic deflection means so that electrical field-distribution spread out along the incidence direction of ion means is made similar to magnetic field-distribution of a magnetic deflection means spread out in the same direction. Ion beams composed of kinds of ions selected by this, that is, external forces acting upon the selected beams are mostly cancelled at every positions located along the ion beam incidence direction, so that rectilinearity can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention extracts and accelerates ions from plasma using an electric field. It is a mass separator used in ion implantation equipment, ion beam lithography equipment, ion beam processing equipment, etc. using so-called field emission ion sources.
Provides a vertical deflection effect to the linearly incident ion beam.

A magnetic deflection means consisting of a pair of flat magnetic pole plates facing each other provides a deflection action in the opposite direction. a selection member having a main electrostatic deflection means consisting of a pair of opposing flat electrode plates, and an aperture that imparts both of the deflection effects to the incident ion beam and allows only ion species of a specific mass in the ion beam to pass through; Relating to something that is equipped with.

[Conventional technology]

An example of a conventional configuration of this type of mass separator is shown in FIG. This mass separator attempts to deflect the ion beam in the -y force direction shown in the figure when the polarity of various ion species constituting the linearly incident ion beam 1 is positive. Magnetic deflection means 4 consisting of flat magnetic pole plates 4a and 4b facing vertically
and attempts to deflect the ion beam 1 in the opposite y direction.

When the main electrostatic deflection means 5 consists of flat electrode plates 5a and 5b facing each other on the left and right, and when both deflection actions are applied to the ion beam at the same time, the deflection forces are balanced to maintain straightness at the time of incidence. It is constructed using a selection member 6 having an opening 6a through which only ion species, that is, ion species having a specific value of the ratio of mass to charge amount, pass through. For ions with other mass-to-charge ratios, the deflection forces are not balanced, and for this reason, the ion beams of these ion types cannot travel straight, becoming a so-called cut beam 3 and being deflected by the force. .

When this type of mass separator is used in a focused ion beam device where the ion beam diameter is 1 micron or less, that is, submicron, the better the straightness of the ion beam 2 passing through the aperture 6a, the better the mass separator can be said to be. .

[Problem that the invention seeks to solve]

However, conventional mass separators configured as one or more have the following problems.

FIG. 3 shows the magnetic field Bx along the direction of incidence of the ion beam.

An example of the distribution of the electric field Ey is shown. In the figure, L is the length of the magnetic pole plate of the magnetic deflection means and the electrode plate of the main electrostatic deflection means in the ion beam incident direction. Generally, the magnetic field has a large leakage at the ends of the magnetic pole plates, and also reaches far away.

On the other hand, the leakage of the electric field at the edges of the electrode plate is relatively small.

Further, since it is shielded by various ion optical system elements arranged on the ion beam entrance side and the exit side, the electric field becomes zero at a position slightly away from the electrode plate. Furthermore, since the shielding is generally asymmetrical, the shapes of both sides of the electric field distribution shown in FIG. 3 are asymmetrical. In this way, the magnetic field distribution and the electric field distribution are not similar, so in reality, the beam composed of one selected ion species does not travel straight,
There is a problem in that the beam is subject to minute displacements, which deteriorates the focusing characteristics of the beam, and a solution to this problem has been desired.

An object of the present invention is to provide a mass separator that greatly improves the straightness of an ion beam made of one selected ion species and eliminates deterioration of its focusing characteristics when used in various ion beam devices. .

[Means for solving the invention]

According to the present invention, to achieve the above object.

Provides a vertical deflection effect to the linearly incident ion beam. A magnetic deflection means consisting of a pair of flat magnetic pole plates facing each other provides a deflection action in the opposite direction.

a selection member having a main electrostatic deflection means consisting of a pair of opposing flat electrode plates, and an aperture that imparts both of the deflection effects to the incident ion beam and allows only ion species of a specific mass in the ion beam to pass through; In the mass separator, an electrostatic field is generated in the same direction as the main electrostatic deflection means near an end in the ion beam incident direction of a flat electrode plate constituting the main electrostatic deflection means. A small number of auxiliary electrostatic deflection means (one set of auxiliary electrostatic deflection means) each consisting of a pair of opposing child plate-shaped electrode plates are arranged to supply an appropriate DC voltage and change the end electric field of the main electrostatic deflection means to deflect the ions. The electric field distribution along the direction of incidence of the beam is made similar to the magnetic field distribution occurring between the magnetic pole plates of the magnetic deflection means.

[Effect]

In this way, the auxiliary electrostatic deflection means that generates an electrostatic field in the same direction as the main electrostatic deflection means is arranged near the end in the ion beam incident direction of the flat electrode plate constituting the main electrostatic deflection means. By changing the end electric field in the main electrostatic deflection means and making the electric field distribution along the direction of incidence of the ion beam similar to the magnetic field distribution in the same direction in the magnetic deflection means, an ion beam consisting of one selected ion species is selected. There is almost no external force acting on the beam at any position along the ion beam incident direction, and straightness can be greatly improved.

[Embodiments of the invention]

FIG. 1 shows one embodiment of the present invention, and is a cross-sectional plan view in the yz plane direction in FIG. 2. The opposing electrode plates 5a and 5b of the main electrostatic deflection means are respectively attached to the opposing surfaces of insulating plates La and 9b arranged in parallel to each other, and constitute auxiliary electrostatic deflection means on the back side of these insulating plates. Electrode plate 7
a, 7b and F3a.

8b are attached to the ion beam entrance side and the ion beam exit side, respectively. Since the length of the skirt on the ion beam entrance side of the electric field distribution Ey shown in Fig. 3 is shorter than that on the exit side, in order to correct this asymmetry and obtain similarity with the magnetic field distribution, the electrode plate on the ion beam entrance side is 7a and 7b are set longer than the electrode plates 3a and 8b on the emission side. Also, ■ in the figure
. , ■□+■2 are electrode plates 5a, 5b, 7m, 7, respectively.
b, 8a, and 8b, and each electrode plate is given a potential so as to be symmetrical in positive and negative directions with respect to the incident axis of the ion beam. FIG. 4 shows an example of the electric field distribution along the ion beam incident direction when the magnitude of each potential difference is set to the relationship 0<Vz<Vt<Vo. Third
Comparing with the figure, it can be seen that the magnetic field distribution is very similar. In this example, the length of the electrode plate of the main electrostatic deflection means in the ion beam incident direction is shorter than the length of the magnetic pole plate.

In the above-described embodiment, the auxiliary electrostatic deflection means are arranged on both sides of the main electrostatic deflection means in the ion beam incident direction, but the auxiliary electrostatic deflection means may be disposed on either side of the electrode of the main electrostatic deflection means. By changing the length of the plate and the length of the electrode plate of the auxiliary electrostatic deflection means in coordination with each other and appropriately setting the potential difference between the electrode plates, the electric field distribution in the ion beam incident direction can be made to match the magnetic field distribution in the same direction. It is also possible to make them similar, and instead of always applying strictly equal potentials to the opposing electrode plates, it is also possible to apply potentials with a slight shift to compensate for mechanical misalignment of the electrode plates. good. Although not particularly shown here, if the electrode plate of the auxiliary electrostatic deflection means is arranged so as to be movable in the plane of the plate and in the direction of incidence of the ion beam, adjustments can be made to obtain similarity with the magnetic field distribution. becomes easier.

〔Effect of the invention〕

As described above, according to the present invention, a vertical deflection effect is applied to the linearly incident ion beam.

A magnetic deflection means consisting of a pair of flat magnetic pole plates facing each other provides a deflection action in the opposite direction. a selection member having a main electrostatic deflection means consisting of a pair of opposing flat electrode plates, and an aperture that imparts both of the deflection effects to the incident ion beam and allows only ion species of a specific mass in the ion beam to pass through; In the mass separator, an electrostatic field is generated in the same direction as the main electrostatic deflection means near an end in the ion beam incident direction of a flat electrode plate constituting the main electrostatic deflection means. A small number of auxiliary electrostatic deflection means (one set of auxiliary electrostatic deflection means) each consisting of a pair of opposing flat electrode plates are arranged to supply an appropriate DC voltage and change the end electric field of the main electrostatic deflection means to deflect the ion beam. The electric field distribution along the incident direction of the magnetic deflector is made similar to the magnetic field distribution generated between the magnetic pole plates of the magnetic deflection means, so that the straightness of the ion beam composed of the ion species having the selected mass is improved. As a result, the problem of deterioration of beam focusing characteristics in various ion beam devices using this mass separator can be solved.Furthermore, if the mass separator is configured as in the present invention, By slightly adjusting the DC voltage applied to the opposing electrode plates of the auxiliary electrostatic deflection means, it has become possible to correct the distortion during machining of the mass separator.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the static deflection section of the mass separator according to the embodiment of the present invention, Fig. 2 is a perspective view showing an example of the configuration of the deflection section in a conventional mass separator, and Fig. 3 is the ion beam incident direction. An example of the conventional magnetic field distribution and electric field distribution along . FIG. 84 is an electric field distribution diagram improved by the present invention. 1... Ion beam, 4a, 4b... Magnetic pole plate, 53
゜5b, 7a, 7b, 8a, 8b...electrode plate%6...
・Selected parts. 1st diagram 3rd diagram 4th diagram

Claims (1)

[Claims] 1) Magnetic deflection means consisting of a pair of opposing flat magnetic pole plates that give a vertical deflection effect to a linearly incident ion beam, and deflection in the opposite direction. a main electrostatic deflection means consisting of a pair of opposing flat electrode plates, and an aperture that imparts both of the deflection effects to the incident ion beam and allows only ion species of a specific mass in the ion beam to pass through; In the mass separator, an electrostatic field in the same direction as the main electrostatic deflection means is applied near an end in the ion beam incident direction of the flat electrode plate constituting the main electrostatic deflection means. At least one set of auxiliary electrostatic deflection means consisting of a pair of opposing flat electrode plates is arranged to supply an appropriate DC voltage to change the end electric field of the main electrostatic deflection means to deflect the ion beam. A mass separator characterized in that an electric field distribution along the incident direction of the magnetic deflector is made similar to a magnetic field distribution occurring between the magnetic pole plates of the magnetic deflection means. 2) In the mass separator according to claim 1,
A mass separator characterized in that the flat electrode plates constituting the auxiliary electrostatic deflection means are arranged with a wider facing distance than the flat electrode plates constituting the main electrostatic deflection means. 3) In the mass separator according to claim 1,
A mass separator characterized in that the auxiliary electrostatic deflection means are arranged near both ends of the main electrostatic deflection means in the ion beam incident direction, and are supplied with different DC voltages. 4) In the mass separator according to claim 1,
A mass separator characterized in that a flat electrode plate constituting the auxiliary electrostatic deflection means is disposed so as to be movable in the in-plane direction of the electrode plate and in the ion beam incident direction.