JP2852144B2 - Objective collimator for charged particle beam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the analysis and processing of a minute area of a sample using a high-energy charged particle beam focused on an extremely small beam in fields such as new materials and semiconductor technology, as well as medical and biotechnology. The present invention relates to a charged particle beam focusing device for injecting foreign matter and the like, and relates to an objective collimator for narrowing a charged particle beam from an emission source to a micro beam having a predetermined diameter on a beam orbit.

[0002]

2. Description of the Related Art In the field of new materials and semiconductor technology, processing processes in a micro area such as injecting a minute amount of foreign matter into a sample, forming a thin film made of a different material after performing fine processing, and the like are used. However, in recent years, the tendency of microfabrication processes in these fields to be extremely miniaturized and multilayered has been increasingly accelerated. In the micro-manufacturing process and the medical and biotechnology fields where analysis of minute regions is required for quantitative evaluation of trace element composition in cells, processing and analysis using focused charged particle beams are effective means. As it becomes more and more important. On the other hand, in response to the demand for miniaturization, the focusing of the charged particle beam diameter in the charged particle beam focusing device can be reduced to the order of 1 μm.

FIG. 3 and FIG. 4 are schematic diagrams showing an example of the arrangement of a typical charged particle beam focusing apparatus.
In the example of the device shown in FIG. 3, it is generated in the ion source (31),
Accelerator (32) Accelerated high energy ion beam B
The ion species and energy are selected by a deflection analysis electromagnet (33), then focused to a beam of several tens of μm diameter by an objective collimator (34), and a quadrupole electromagnet lens (35 ) In the chamber (3
6) and placed in this chamber (36).
7) The configuration is such that a beam spot of the order of 1 μm is connected on top. In the apparatus shown in FIG. 4, the high-energy ion beam B generated by the ion source (41) and accelerated by the accelerator (42) is narrowed down to a beam having a diameter of several tens μm by the objective collimator (43). Next, a Vienna (E × B) mass spectrometer (44)
The ion species and energy are selected at, and then introduced into the chamber (46) as an intended focused beam by the quadrupole electromagnet lens (45), on the sample (47) placed in the chamber (46). To
The configuration is such that a beam spot on the order of 1 μm is connected. In these apparatuses, an ion beam from an ion source is guided to a chamber via a vacuum pipe not shown here.

In these charged particle beam focusing apparatuses, a beam spot on the order of 1 μm is obtained and micromachining and analysis of the sample are performed under the above-described configuration. In any case, the size of the beam spot on the sample is Is determined by the beam diameter narrowed down by the objective collimator and the beam reduction rate by the quadrupole electromagnet lens. Therefore, in order to focus the ion beam on the sample with an accuracy of the order of 1 μm, it is necessary to control the beam diameter with the same level of accuracy in the objective collimator.

A typical example of the configuration of a conventional objective collimator mounted on these charged particle beam focusing devices is shown in FIG. FIG. 5 is a sectional view of a main part showing a schematic configuration and a mounted state of a conventional objective collimator. FIG. 5A is a front sectional view, and FIG. 5B is a sectional view taken along line AA of FIG. FIG. This conventional objective collimator includes a pair of slits (51) arranged in parallel and opposed to each other, and a precision translation drive mechanism (52) connected to the base ends of these pairs of slits (51). Position the slit (51) in the vacuum duct (53) that guides the beam,
Two pairs are mounted adjacent to the vacuum duct (53) in the axial direction. The two pairs of objective collimators (51) are orthogonally opposed to the vacuum duct (53) to form a pair, and the two pairs are provided at a 90-degree angle from each other in the vertical and horizontal directions. The vacuum duct (53) is attached to the vacuum duct (53) through a port (54), and the distance between each of the two pairs of slits (51) is finely adjusted by a precision translation drive mechanism (52). Is cut out from the top and bottom, left and right with a precision of μm unit, and narrowed down to a beam B ′ having a predetermined diameter of several tens μm.

[0006]

However, in the above-mentioned conventional objective collimator, the two pairs of slits (51) have a 90-degree angular phase because the charged particle beam is narrowed down, up and down, left and right, that is, in two directions XY. In addition, it is necessary to provide a precise translation drive mechanism (52) for controlling the distance between each pair of slits (51), and the configuration is complicated, the operability is inferior, and the equipment cost is reduced. Is required. Furthermore, the number of ports (54) provided in the vacuum duct (53) for installation thereof is increased, and this tends to be a factor that adversely affects the vacuum duct (53), such as an increase in outgas and a decrease in conductance. .

Some devices using high-energy beams do not focus a beam from a radiation source into a microbeam with a quadrupole electromagnet lens or the like, but directly convert the beam into a beam having a diameter on the order of several mm by an objective collimator. Some are squeezed. In such an apparatus, an objective collimator having a single-layer plate made of a high melting point material (molybdenum, tantalum, or the like) provided with a beam passage hole having a predetermined diameter is used. In this objective collimator, the position can be controlled only in one axial direction. Therefore, it is possible to obtain an advantage that the configuration is simplified and the operability is good, and that only one port for mounting the vacuum duct is required. However, the present inventors have studied the application of the objective collimator of this configuration to the charged particle beam focusing apparatus in order to obtain these advantages, and found that the following problems are derived, and it is difficult to apply the objective collimator as it is. did. That is, in the objective collimator used in the charged particle beam focusing device, the size of the aperture for narrowing the charged particle beam is finished to the order of 1 μm, and the edge portion has a surface roughness of R _max 0.1 μmm in order to prevent scattering of the beam. A single-layer plate made of a high-melting-point material (molybdenum, tantalum, etc.), which is a difficult-to-machine material, must be drilled to a diameter of several tens of μm that satisfies such accuracy and roughness at the same time. This is very difficult and the processing costs are significantly higher. Furthermore, when the surface of the edge portion is roughened by the irradiation of the beam, the surface roughness can be restored by re-polishing the edge portion, but the dimension of the opening portion changes and the intended function is lost. For this reason, there is also a disadvantage that it must be replaced as a consumable part.

An object of the present invention is to provide a charged particle beam objective collimator which has a simple structure, is excellent in operability, can set a slit interval with high precision, and can narrow a charged particle beam to a beam having a predetermined diameter. It is the purpose.

[0009]

In order to achieve the above object, the present invention has the following arrangement. That is, the charged particle beam objective collimator according to the first aspect of the present invention includes a driving device mounted orthogonally to a vacuum duct for guiding a beam, and a base end connected to an output portion of the driving device. An aperture plate capable of moving forward and backward toward the inside of the vacuum duct, and a pair of slit bars attached to the front and back surfaces of the aperture plate so as to face each other. While having a beam passage hole in the portion, the plane thereof is disposed perpendicular to the axis of the vacuum duct, the pair of slit bars are opposed to each other in parallel with a space between the beam passage holes of the aperture plate, and The pair on the front surface and the pair on the back surface of the aperture plate are crossed with each other and detachably attached to the aperture plate.

In the objective collimator for a charged particle beam according to the present invention, the aperture plate has a plurality of beam passage holes arranged in the main body in parallel in the forward and backward directions. It is provided with a plurality of pairs of slit bars attached to each other so as to sandwich each of the beam passage holes on the front and back surfaces.

[0011]

According to the first aspect of the present invention, a beam passage hole is provided in a main portion of an aperture plate which can advance and retreat toward a vacuum duct for guiding a beam, and the beam is provided on each of the front and back surfaces of the aperture plate. Since two pairs of slit bars, which are arranged in parallel and face each other with a space between the passage holes and cross each other, are attached, the charged particle beam passed through the vacuum duct is converted into two pairs of slit bars. The beam can be narrowed down to a beam having a predetermined diameter from two directions crossing each other. In addition, by controlling the position of the aperture plate in one axis direction by one driving device, the center of the beam passage hole can be made to coincide with the center axis of the vacuum duct, so that the operation is easy and the driving is further facilitated. At least one mounting portion for the vacuum duct of the apparatus is required, and mounting is easy, and airtightness of the vacuum duct is easily maintained. In addition, the pair of slit bars for narrowing the charged particle beam is detachably attached in parallel on the front and back surfaces of the aperture plate. Even if the surface can be narrowed down and the surface becomes rough due to the irradiation of the beam, the function can be easily restored and reused by removing and repolishing.

In the invention according to the second aspect, the aperture plate has a plurality of beam passage holes arranged in the main body in the reciprocating direction, and the respective beam passage holes of the aperture plate are formed on the front and back surfaces. Since there are provided a plurality of pairs of slit bars that are sandwiched and attached, by setting the intervals between the pair of slit bars arranged in each beam passage hole to different dimensions, the position control of the aperture plate in the uniaxial direction can also be performed. Thus, a plurality of types of beam diameters can be selected.

[0013]

Embodiments of the objective collimator of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing a schematic configuration and a mounted state of an objective collimator according to an embodiment of the present invention, wherein FIG. 1A is a front sectional view, and FIG. Partial view from arrow A, (c)
The figure is a partial view taken on line CC of FIG.

In FIG. 1, (1) is a drive device, which is driven by a motor (not shown), and has an output end (in which cooling means is provided). It adopts a screw cylinder configuration that advances and retreats 1a) at a minute pitch, and is hermetically mounted on a port P provided orthogonal to a vacuum duct D for guiding a beam B, and a port at the lower end of the output end (1a). It is located in P and arranged in a direction perpendicular to the axis of the vacuum duct D. The driving device (1) is mounted on the port P via an insulating member, and is electrically insulated from the port P and the vacuum duct D.

Reference numeral (2) denotes an aperture plate. The aperture plate (2) is a flat plate (made of copper plate in this example) made of a material having a high thermal conductivity, and its base end is connected to a drive unit (1). Is connected to the output end (1a), and the main body can be advanced and retracted into the vacuum duct D. Also, this aperture plate (2)
Is a plurality of (three in this example) beam passage holes
(2a) is provided in parallel in the forward and backward directions, while its plane is arranged perpendicular to the axis of the vacuum duct D.

The slit bar (3) is a rod-shaped body made of a high melting point material, and has a hemispherical edge (3a) at the front edge corresponding to one side. The beam B is arranged opposite to each other at a predetermined interval in parallel with each beam passing hole (2a) of the aperture plate (2) therebetween, and the beam B is cut into a predetermined width by the pair. Further, these slit bars (3) are arranged on one surface of the aperture plate (2) in a direction orthogonal to the advance / retreat direction of the aperture plate (2).
On the other surface, the aperture plate (2) is sandwiched between the beam passing holes (2a) in a direction parallel to the advance / retreat direction of the aperture plate (2).
It is detachably attached to. That is, they are arranged orthogonally to each other on the front and back surfaces of the same beam passage hole (2a),
The beam B passed through the inside of the vacuum duct D is narrowed to a micro beam B 'having a predetermined diameter from two orthogonal directions by two pairs of slit bars (3). The distance between the two pairs of slit bars (3) arranged in each beam passage hole (2a) is set to a different size in each beam passage hole (2a). Also, each pair of slit bars (3)
For setting the spacing between the pairs of slit bars
When attaching (3) to the aperture plate (2), a precision gap gauge was inserted between the edge portions (3a) of these slit bars (3) to set the interval with an accuracy of μm unit.

In the objective collimator of this embodiment having the above configuration, the center of one of the beam passage holes (2a) of the aperture plate (2) is positioned on the center axis of the vacuum duct D by the driving device (1). The beam B passed through the vacuum duct D by two pairs of slit bars (3) arranged on the front and back of the beam passage hole (2a) is cut out from two orthogonal directions with a precision of μm unit, and The beam is narrowed down to a microbeam B 'having a diameter of several tens of μm. The heat generated in the slit bar (3) by the collision of the beam B is transmitted through an aperture plate (2) made of a highly heat-conductive material and an output end (1a) of a driving device (1) provided with cooling means. Pump outside and slit bar (3)
Is suppressed and the function of narrowing down the beam B is stabilized.

In this way, in the objective collimator of the present embodiment for narrowing the beam B passed through the vacuum duct D to a predetermined micro-beam B 'having a diameter of several tens of μm, the position of the aperture plate (2) in one axial direction is reduced. Under the control, the diameter of the micro beam B 'can be selected from a plurality of types (three types in this example).

Further, the position of the aperture plate (2) is controlled in one axial direction by one driving device (1) so that the center of each beam passage hole (2a) coincides with the center axis of the vacuum duct D. Is easy to operate.
It is not necessary to provide a plurality of ports for attaching the drive device to the vacuum duct as in the related art, so that the airtight maintenance of the vacuum duct becomes much easier and the installation becomes easier.

The slit bar (3) made of a high melting point material for narrowing the beam B is detachably attached to the aperture plate (2) in pairs, so that the edge portion (3) at the time of the attachment is removed.
a) Easy adjustment of the distance between the two, achieving high-precision beam narrowing.Even if the surface of the edge part (3a) becomes rough due to beam irradiation, the function can be easily restored by removing and re-polishing. And maintenance is easy.

As described above, the objective collimator of the present embodiment has a simple structure, is excellent in operability, is easy to maintain, and can achieve high economic efficiency.

In this embodiment, three apertures for arranging slit bars are provided in the aperture plate. However, this is an example. If the number is one or more, the objective collimator is mounted. The selection may be made according to the size and application of the charged particle beam focusing device.

The pair of slit bars to be attached to the aperture plate is a rod-like body having a semi-spherical cross-section at the opposing front edge. This is effective in preventing scattering of the narrowed beam. If a similar effect can be obtained, for example, as shown in FIG. 2 which is a cross-sectional view of the main part, a knife edge-shaped edge portion (23a) is provided at the front edge. A rectangular slit bar (23) may be employed.

Furthermore, in the present embodiment, two pairs of front and back slit bars attached to the aperture plate are arranged perpendicular to each other. However, if the beam can be narrowed down to a predetermined micro beam from two different directions, These two pairs of slit bars need not always be orthogonal.

[0026]

As described above, the objective collimator of the embodiment according to the present invention can set the slit interval with high precision and can narrow the charged particle beam to a micro beam having a predetermined diameter. The structure is simple, the mounting is easy, and the operability is excellent, and a high economical gain can be obtained by applying the structure.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration and a mounted state of an objective collimator according to an embodiment of the present invention, wherein FIG.
(b) is a partial view taken along the line AA in (a), and (c) is a partial view taken along the line CC in (a).

FIG. 2 is a cross-sectional view of a principal part for describing another embodiment of the objective collimator according to the embodiment of the present invention.

FIG. 3 is a schematic diagram showing an example of the configuration and arrangement of a typical charged particle beam focusing device.

FIG. 4 is a schematic diagram showing a configuration example of a typical charged particle beam focusing apparatus.

FIG. 5 is a cross-sectional view of a main part showing a schematic configuration and a mounted state of a conventional objective collimator.

[Explanation of symbols]

(1)-Drive (1a)-Output end (2)-Aperture plate (2a)-Beam passage hole (3)-Slit bar (3a)-Edge D-Vacuum duct P --Port B --Beam B '-Microbeam

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-209200 (JP, A) Japanese Utility Model Application Sho 59-4500 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G21K 1/02-1/04 G21K 5/04 H01J 37/09

Claims (2)

(57) [Claims] 1. A drive device mounted orthogonally to a vacuum duct for guiding a beam, a base end portion of which is connected to an output portion of the drive device, and a main body portion can be advanced and retracted into the vacuum duct. An aperture plate, and a pair of slit bars attached to each other on the front and back surfaces of the aperture plate, wherein the aperture plate has a beam passage hole in the main body portion, and the flat surface thereof The slit bars are arranged perpendicular to the axis of the vacuum duct, and the pair of slit bars are opposed to each other in parallel with a space between the beam passage holes of the aperture plate, and the pair on the front surface and the back surface on the aperture plate. An objective collimator for a charged particle beam, wherein said objective collimator is detachably attached to an aperture plate with a pair intersecting each other. 2. An aperture plate having a plurality of beam passage holes arranged in the main body in the advancing and retreating directions, and a plurality of pairs attached to each other by sandwiching each of the beam passage holes of the aperture plate on the front and back surfaces. 2. The objective collimator for a charged particle beam according to claim 1, further comprising a slit bar.