JP2017004907A - Vacuum chamber and mass spectrometer electromagnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce divergence nonuniformity of a ribbon beam in a lengthwise direction caused by beam potential.SOLUTION: In a vacuum chamber C constituting a transportation path of a ribbon beam B, when a direction of travel of the ribbon beam B passing through the vacuum chamber C is denoted as Z direction, a lengthwise direction of the ribbon beam B is denoted as Y direction, and a direction orthogonal to both directions is denoted as X direction, in an end part area of the vacuum chamber C in the Y direction, an inner dimension of the vacuum chamber C in the X direction becomes smaller toward the end part of the vacuum chamber C.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vacuum chamber used for transporting a ribbon beam and a mass spectrometry electromagnet having the same chamber.

  Ion beams and electron beams are used in various industrial equipment such as ion implantation apparatuses and electron beam irradiation apparatuses. There are various beam shapes used in each apparatus, and various types such as a spot beam, a ribbon beam, and a surface beam are used depending on the apparatus configuration and the type of substrate to be processed. An apparatus that handles such a charged beam is called a charged particle beam apparatus.

  As a specific example of an ion implantation apparatus which is one of the charged particle beam apparatuses described above, there is an ion implantation apparatus using a ribbon beam described in Patent Document 1. The ribbon beam is a beam having a substantially rectangular cut surface when the charged particle beam is cut along a plane perpendicular to the traveling direction of the charged particle beam transported inside the apparatus.

  Many charged particle beam devices have a vacuum chamber for transporting the beam in a vacuum. In the example of Patent Document 1, the vacuum chamber is provided so as to cover the transport path of the ion beam from the ion source where the ion beam is generated to the processing chamber where the substrate is arranged.

FIG. 11 and FIG. 13 of Patent Document 1 illustrate a state in which the vacuum chamber is cut along a plane perpendicular to the traveling direction of the ribbon beam.
As can be seen from these drawings, the vacuum chamber of Patent Document 1 is a rectangular container in which a space through which a ribbon beam passes is formed. The vacuum chamber having such a shape is used not only in the ion implantation apparatus disclosed in Patent Document 1, but also in other charged particle beam apparatuses using a ribbon beam.

JP 2005-327713 A

  A charged particle beam is a beam having a positive or negative charge. In such a beam, a potential (beam potential) is formed inside the beam by the charge of the beam itself. In many cases, since the vacuum chamber is electrically grounded, a potential difference is generated between the vacuum chamber and the beam, and an electric field is generated. The charged particle beam diverges during transport due to the action of this electric field, but in the case of a ribbon beam, the beam potential tends to be different in the length direction of the ribbon beam, so the electric field in the same direction becomes non-uniform and the ribbon The degree of divergence is different at each part of the beam.

  The reason why the divergence of the ribbon beam is uneven depending on the location will be described in detail with reference to FIG. In FIG. 10, the equipotential lines of the electric field formed in the vacuum chamber by the beam potential are drawn with broken lines. The vacuum chamber C depicted in this figure has the same shape as the vacuum chamber depicted in FIGS. In FIG. 10, the lower region of the vacuum chamber C is omitted because it is substantially the same as the upper region illustrated in FIG.

  The vacuum chamber C is electrically grounded, and a ribbon beam B having a positive charge passes through the vacuum chamber C. In the longitudinal direction of the ribbon beam B (vertical direction in the figure), the potential is higher in the central region (approximately the region surrounded by CR) of the vacuum chamber C through which the center of the ribbon beam B passes, and the end of the ribbon beam B passes through. The potential of the end region of the vacuum chamber C (region surrounded by ER) tends to be lower. For this reason, a stronger electric field is generated in the central region of the vacuum chamber C than in the end region, and the divergence of the ribbon beam B is increased. On the contrary, in the end region of the vacuum chamber C, a weak electric field is generated as compared with the central region, and the divergence of the ribbon beam B is reduced.

  If the degree of divergence due to the beam potential is different in each part in the length direction of the ribbon beam, the shape of the ribbon beam is distorted. If the shape of the ribbon beam is distorted, there is a concern that the substrate processing using the ribbon beam may be hindered and the beam transport efficiency in the beam optical system may be adversely affected.

  Therefore, in the present invention, it is an initial task to reduce the divergence non-uniformity in the length direction of the ribbon beam due to the beam potential.

  The vacuum chamber according to the present invention is a vacuum chamber constituting a transport path of the ribbon beam, and the traveling direction of the ribbon beam passing through the vacuum chamber is defined as the Z direction, and the length direction of the ribbon beam is defined as the Y direction. Assuming that the direction to be performed is the X direction, the inner dimension of the vacuum chamber in the X direction becomes smaller toward the end of the vacuum chamber in the end region of the vacuum chamber in the Y direction.

  In the case of the vacuum chamber configured as described above, the equipotential lines formed in the end region of the vacuum chamber through which the end in the length direction of the ribbon beam having a relatively low beam potential passes are dense so that the electric field in the same region Strength can be increased. As a result, the non-uniformity of divergence in the length direction of the ribbon beam is reduced.

  Depending on the beam optical system arranged in the transport path of the ribbon beam, the shape of the ribbon beam changes along the transport path. The shape of the vacuum chamber may be changed in accordance with such a change in the shape of the ribbon beam. Specifically, in the end region of the vacuum chamber, the inner dimension of the vacuum chamber in the X direction is changed in the Z direction as the dimension of the ribbon beam in the X direction is changed along the Z direction. A configuration that changes along the line is used.

  Further, in the X direction, when considering the difference in Lorentz force acting on the ribbon beam in the deflecting electromagnet, the shape of the ribbon beam in the same direction, etc., the inner wall shape of the vacuum chamber includes the center of the ribbon beam in the Y direction. However, the configuration may be asymmetric in the X direction.

  Moreover, you may use the structure by which a some electroconductive plate is arrange | positioned in the edge part area | region of the said vacuum chamber.

  With the above configuration, it is possible to easily change the configuration of the internal region of the vacuum chamber through which the ribbon beam passes by simply changing the mounting location and angle of the conductive plate, the dimensions of the conductive plate, etc. Become. As a result, it is possible to easily reduce the divergence non-uniformity in the length direction of the ribbon beam.

  Furthermore, when a conductive plate is disposed, the potential of the vacuum chamber and the conductive plate may be different.

  With the above configuration, the electric field distribution formed in the internal region of the vacuum chamber can be adjusted by changing the voltage applied to the conductive plate.

  As a more specific configuration, a configuration in which the ribbon beam has a positive charge and the potential of the conductive plate is lower than the potential of the vacuum chamber is used.

It is desirable to use a mass spectrometry electromagnet provided with the vacuum chamber. The mass analyzing electromagnet is used to rotate the ribbon beam by a sufficient distance to remove unnecessary components contained in the beam. The beam transport distance in the electromagnet is relatively smaller than that of other beam optical elements. long.
When the divergence non-uniformity of the ribbon beam is large, it is difficult to perform normal mass analysis. However, by using the vacuum chamber of the present invention as a beam transport tube of the mass analysis electromagnet, the ribbon beam that passes through the inside of the mass analysis electromagnet. The divergence non-uniformity is sufficiently reduced, and normal mass spectrometry can be performed.

  By making dense equipotential lines formed in the end region of the vacuum chamber through which the end in the length direction of the ribbon beam having a relatively low beam potential passes, it is possible to increase the electric field strength in the same region. As a result, the non-uniformity of divergence in the length direction of the ribbon beam is reduced.

It is a top view which shows the structural example of the ion implantation apparatus with which this invention is applied. It is the sectional view on the AA line shown in FIG. (A) is a structure which forms the internal space of a vacuum chamber using an electroconductive plate, (B) is a structure which deform | transforms the shape of a vacuum chamber itself and forms the internal space of a vacuum chamber. It is sectional drawing which shows the 1st modification of the vacuum chamber shown in FIG. It is sectional drawing which shows the 2nd modification of the vacuum chamber shown in FIG. (A) is a configuration using a stepped conductive plate, and (B) is a configuration using a curved conductive plate. It is sectional drawing which shows the 3rd modification of the vacuum chamber shown in FIG. (A) is a structure which arrange | positions many electroconductive plates on the upper and lower surfaces of a vacuum chamber, (B) is a structure which arrange | positions many electroconductive plates on the left and right side surfaces of a vacuum chamber. It is sectional drawing which shows the 4th modification of the vacuum chamber shown in FIG. (A) is a configuration in which one power source is connected to a plurality of conductive plates, and (B) is a configuration in which a power source is individually connected to each conductive plate. It is a top view which shows the structural example of another ion implantation apparatus with which this invention is applied. It is explanatory drawing regarding the structure where the edge part area | region of a vacuum chamber changes with the change of a beam diameter. (A) is a top view showing a mode that a beam diameter changes within a mass spectrometry electromagnet. (B) is sectional drawing in the BB line of (A). (C) is sectional drawing in the CC line of (A). (D) is sectional drawing in the DD line of (A). It is explanatory drawing regarding the structure where the left-right side surface is asymmetrical in the edge part area | region of a vacuum chamber. (A) is a top view showing a mode that a beam diameter changes within a mass spectrometry electromagnet. (B) is sectional drawing in the BB line of (A). (C) is sectional drawing in the CC line of (A). (D) is sectional drawing in the DD line of (A). In the sectional view of the conventional vacuum chamber, the electric field distribution by the beam potential of the ribbon beam is represented.

As an example of a charged particle beam apparatus to which the present invention is applied, a configuration example of an ion implantation apparatus is depicted in FIG. The overall configuration of the ion implantation apparatus IM will be briefly described. The XYZ axes shown in the drawing represent the direction of the ribbon beam B in the processing chamber 4.
Specifically, the Z-axis direction (Z direction) is the traveling direction of the ribbon beam B, and the Y-axis direction (Y direction) is a beam cross section when the ribbon beam B is cut along a plane perpendicular to the Z axis. It is the length direction of the ribbon beam B in FIG. The X-axis direction (X direction) is the short-side direction of the ribbon beam B, and is also the direction orthogonal to the Y-axis and the Z-axis.

  The ribbon beam B generated by the ion source 1 passes through the mass analysis electromagnet 2 and the analysis slit 3 so that unnecessary ions contained in the beam are removed. A substrate S (a glass substrate, a semiconductor substrate such as a silicon wafer) supported by a scanning mechanism (not shown) is disposed in the processing chamber 4, and the substrate S is a ribbon beam irradiated into the processing chamber 4 by the scanning mechanism. It is scanned across B in the direction of the arrow shown.

A beam current measuring device 5 is disposed on the downstream side of the substrate S. When the substrate S is not irradiated with the ribbon beam B, the ribbon beam B is applied to the beam current measuring device 5.
The beam current measuring instrument 5 is a multi-point Faraday cup composed of, for example, a plurality of Faraday cups arranged along the Y direction. Using this measuring instrument, the beam current distribution of the ribbon beam B in the Y direction can be measured.
Further, instead of the multi-point Faraday cup, the beam current measuring device 5 is constituted by one Faraday cup, and this is moved along the Y direction so that the beam current distribution in the Y direction can be measured. It may be configured.

  In the transport path of the ribbon beam B from the ion source 1 to the processing chamber 4, a vacuum chamber C for keeping the transport path in a vacuum is provided. The configuration of the vacuum chamber C of the present invention will be described below with reference to FIG.

FIG. 2 is a cross-sectional view taken along line AA shown in FIG. Compared with the configuration of the vacuum chamber of the prior art, the configuration of the end region of the vacuum chamber C through which the end of the ribbon beam B in the Y direction passes is different.
Specifically, as can be seen in FIGS. 2A and 2B, in the end region of the vacuum chamber C through which the end of the ribbon beam B in the Y direction passes, the inside of the vacuum chamber C in the X direction. The size is configured to be smaller at the end of the vacuum chamber C.
The end region of the vacuum chamber C is a region through which the end of the ribbon beam B in the Y direction passes, and refers to a region including an inner wall surface formed at the end of the vacuum chamber C in the same direction.

A vacuum chamber C shown in FIG. 2A is a vacuum chamber C having a rectangular cross section as in the prior art, and conductive plates P are arranged at four inner corners of the vacuum chamber C. A space in which the ribbon beam B is transported is formed by the conductive plate P and a part of the inner wall of the vacuum chamber C.
In the configuration example of FIG. 2A, the internal dimension of the vacuum chamber C in the X direction in the end region of the vacuum chamber C refers to the distance between the conductive plates P in the X direction.

  The vacuum chamber C is made of a conductive material such as iron, stainless steel, aluminum, or carbon, and a conductive plate P made of the same kind of material is fixed by a bolt (not shown). In this embodiment, the vacuum chamber C and the conductive plate P are electrically grounded.

  By disposing the conductive plates P at the four corners of the vacuum chamber C, the space in which the ribbon beam B is transported becomes narrow in the end region of the vacuum chamber C in the Y direction. Thereby, the equipotential lines in the end region of the vacuum chamber C become dense, and the electric field in the same region becomes strong. As a result, it is possible to reduce the beam divergence non-uniformity due to the difference in the beam potential in the length direction of the ribbon beam B.

  The vacuum chamber C of the present invention is not limited to the configuration using the conductive plate P. Instead of using the conductive plate P, the shape of the vacuum chamber C may be changed. The vacuum chamber C shown in FIG. 2B has an octagonal configuration so that an internal region similar to that in FIG.

Even if the configuration shown in FIG. 2 (B) is used, the difference in beam potential in the length direction of the ribbon beam B by increasing the electric field in the end region of the vacuum chamber C as in the configuration of FIG. 2 (A). It is possible to reduce the beam divergence non-uniformity. Further, as shown in FIG. 2B, the outer shape of the vacuum chamber C is not necessarily an octagonal shape, and a configuration in which the outer shape is a rectangular shape and the inner shape is an octagonal shape may be used.
2B, the inner dimension of the vacuum chamber C in the X direction in the end region of the vacuum chamber C refers to the distance between the inner walls of the vacuum chamber C in the X direction.

2A and 2B, the same effect can be obtained in terms of reducing the non-uniformity of beam divergence, but the electric field in the end region of the vacuum chamber C can be obtained. In order to easily adjust the distribution, the configuration using the conductive plate P shown in FIG.
This is because the configuration of the internal region of the vacuum chamber C through which the ribbon beam B passes can be easily changed by simply changing the mounting location and mounting angle of the conductive plate P, the dimensions of the conductive plate P, and the like. This is because it becomes possible.

  Further, as the configuration of the vacuum chamber C, the configuration shown in FIG. 3 may be used. FIG. 3 is a cross-sectional view showing a first modification of the vacuum chamber C shown in FIG. In the configuration of FIG. 3, two conductive plates P1 and P2 are used. As in the embodiment depicted in this figure, a combination of a plurality of conductive plates P may be arranged at the four corners of the vacuum chamber C to constitute an internal region of the vacuum chamber C through which the ribbon beam B passes. .

Furthermore, the configuration shown in FIG. 4 may be used. FIG. 4 is a sectional view showing a second modification of the vacuum chamber C shown in FIG. The conductive plate P shown in FIGS. 2A and 3 is a flat plate having a substantially rectangular cross section, but the shape of the conductive plate P may be other shapes.
As the shape of the conductive plate P, for example, a conductive plate P having a stepped cross section as shown in FIG. 4A may be used. Further, as shown in FIG. 4B, a conductive plate P having a curved cross-sectional shape may be used.

  The configuration shown in FIG. 4A is configured such that the inner dimension of the vacuum chamber C in the X direction is intermittently reduced toward the end of the vacuum chamber C in the end region of the vacuum chamber C. . 4B, in the end region of the vacuum chamber C, the inner dimension of the vacuum chamber C in the X direction is exponentially decreased toward the end of the vacuum chamber C. Has been.

  As can be understood from these configuration examples, in the present invention, if the inner dimension of the vacuum chamber C in the X direction is smaller in the end region of the vacuum chamber C, the end of the vacuum chamber C is smaller. good. How the inner dimension of the vacuum chamber C in the X direction is reduced is related to the shape of the conductive plate P and the shape of the inner wall of the vacuum chamber C.

In the embodiments described so far, the conductive plate P is fixedly supported on two adjacent surfaces of the inner wall of the vacuum chamber C. However, the conductive plate P may be fixedly supported on one specific surface.
For example, when a plurality of conductive plates P are fixedly supported on one specific surface of the inner wall of the vacuum chamber C, the configuration example shown in FIG. 5 may be used.

  FIG. 5 is a sectional view showing a third modification of the vacuum chamber shown in FIG. FIG. 5A shows a configuration example in which a plurality of conductive plates P having different lengths are fixedly supported on the upper and lower surfaces of the vacuum chamber C. FIG. The vacuum chamber C of the present invention may have such a configuration. On the other hand, as shown in FIG. 5B, a configuration may be employed in which a plurality of conductive plates P having different lengths are fixedly supported on the left and right side surfaces of the vacuum chamber C.

  In the embodiments described so far, the potential of the conductive plate P is fixed to the same ground potential as the vacuum chamber C. However, the potential of the conductive plate P may be different from that of the vacuum chamber C.

  FIG. 6 is a sectional view showing a fourth modification of the vacuum chamber C shown in FIG. A power supply V is connected to the conductive plate P disposed in the vacuum chamber C of FIG. In the present embodiment, the conductive plate P is fixedly supported by the vacuum chamber C through an insulating member (not shown), and the conductive plate P and the vacuum chamber C are electrically insulated. A voltage of minus tens of volts is applied to each conductive plate P by a power supply V, and the vacuum chamber C is grounded. The ribbon beam passing through the vacuum chamber C has a positive charge.

  If it is the said structure, it will become possible to adjust the electric field strength in the edge part area | region of the vacuum chamber C more easily than the previous embodiment.

Further, as shown in FIG. 6A, a single power source V may be used to apply a voltage to each conductive plate P, but as shown in FIG. 6B. A power supply V corresponding to each conductive plate P may be provided so that the potential of each conductive plate P can be set independently.
Further, regarding the potential setting of the conductive plate P, it is possible to set the potential using a common power source for each set of the conductive plates P, with the conductive plates P arranged above and below or left and right of the vacuum chamber C as a set. It may be configured as follows.

  The vacuum chamber C of the present invention described in the embodiments so far may be provided over the entire transport path of the ribbon beam B from the ion source 1 to the processing chamber 4, but in a part of the transport path. It may be configured to be provided.

  FIG. 7 is a plan view showing a configuration example of another ion implantation apparatus IM to which the present invention is applied. In this configuration example, the vacuum chamber C of the present invention is used for the transport path of the ribbon beam B in the mass analysis electromagnet 2. Further, as shown in the drawing, the conductive plate P is divided into a plurality along the traveling direction of the ribbon beam B.

In the ion implantation apparatus IM of FIG. 7, movable beam current measuring devices 10a and 10b are provided at positions sandwiching the mass analysis electromagnet 2 in which the vacuum chamber C is provided. These beam current measuring devices 10a and 10b have the same function and configuration as the beam current measuring device 5 described in the configuration example of FIG. 1, and are moved in the direction of the arrow in the drawing by a driving mechanism (not shown).
While the substrate S is being processed by the ribbon beam B, the beam current measuring devices 10a and 10b are moved to positions that do not hinder the transport of the ribbon beam B.

Under this configuration, the beam current distribution in the length direction of the ribbon beam B is first measured by the beam current measuring instrument 10a. Next, the beam current distribution in the length direction of the ribbon beam B is measured by the beam current measuring instrument 10b. Thereafter, the measurement results of both measuring instruments are transmitted to the control device Cont, and the control device Cont calculates how the beam current distribution of the ribbon beam B has changed as it passes through the mass analysis electromagnet 2.
Then, the control device Cont controls a power source (not shown) connected to each conductive plate P so that an appropriate voltage is applied to each conductive plate P based on the calculation result.

  If it is the structure which applies a desired voltage to the electroconductive plate P in the vacuum chamber C of this invention, it also becomes possible to combine with the feedback system mentioned above.

In the configuration example of FIG. 7, the voltage applied to each conductive plate P may be controlled based on the measurement result of one of the beam current measuring devices 10a and 10b. In this case, since the number of beam current measuring devices is only one, the ion implantation apparatus IM may be provided with either the beam current measuring device 10a or the beam current measuring device 10b.
Furthermore, instead of the beam current measuring devices 10a and 10b, the voltage applied to each conductive plate P may be controlled based on the measurement result of the beam current measuring device 5. In this case, the ion implantation apparatus IM only needs to include the beam current measuring device 5.

  Further, in the configuration example of FIG. 7, the conductive plate P is divided into a plurality along the beam traveling direction. However, it is not necessary to take such a divided structure, and the conductive plate P is long and integrated along the beam traveling direction. A conductive plate P may be used. Further, in the configuration example of FIG. 7, a configuration in which the conductive plates P are disposed at the four corners of the vacuum chamber C is assumed as in FIG. 2A. However, the conductive plates P are arranged along the beam traveling direction. In this case, the dimension of the conductive plate P arranged in the vacuum chamber C in the beam traveling direction is different in the vertical and horizontal directions of the vacuum chamber C in accordance with the structure of the transport path of the ribbon beam B. May be.

  In addition, the shape of the end region of the vacuum chamber C may change along the traveling direction of the ribbon beam B. For example, the dimension in the X direction of the ribbon beam B passing through the mass analysis electromagnet 2 varies depending on the location of the mass analysis electromagnet 2. FIG. 8 shows a configuration example in which the shape of the end region of the vacuum chamber C changes with such a change in the dimensions of the ribbon beam B.

FIG. 8A is a plan view showing how the beam diameter changes in the mass analysis electromagnet 2, and FIGS. 8B to 8D show the BB line and C shown in FIG. The state of the cross section in the -C line and the DD line is drawn. In this configuration example, conductive plates P are provided at four corners of the vacuum chamber C, and the end regions of the vacuum chamber C are formed by these conductive plates P.
8B and 8D, the conductive plate P is attached to the inner wall of the vacuum chamber C at an angle θa. In FIG. 8C, the conductive plate P is attached to the vacuum chamber C. It is attached to the inner wall at an angle θb (<θa).
Note that the coordinate axes shown in FIG. 8A relate to the ribbon beam B incident on the mass analysis electromagnet 2 and the ribbon beam B emitted from the mass analysis electromagnet 2.

As illustrated in FIG. 8A, the ribbon beam B incident on the mass analysis electromagnet 2 spreads so that the dimension in the X direction is maximized near the center of the mass analysis electromagnet 2, and downstream of the mass analysis electromagnet 2. Focusing is performed so as to focus on the arranged analysis slit.
As the beam size changes in the X direction, the electric field distribution in the end region of the vacuum chamber C also changes. In consideration of this point, in order to sufficiently reduce the divergence non-uniformity in the length direction of the ribbon beam B, it is necessary to change the shape of the end region of the vacuum chamber C in accordance with the change of the beam size.

Specifically, when the dimension of the ribbon beam B in the X direction increases along the Z direction, the inner dimension of the vacuum chamber C in the X direction gradually increases along the Z direction in the end region of the vacuum chamber C. It is configured to spread.
As shown in the figure, when the mounting angle of the conductive plate P shown in FIG. 8B is θa and the mounting angle of the conductive plate P shown in FIG. 8C is θb (<θa), the Z direction The conductive plate P is attached to the vacuum chamber C so that the angle gradually decreases from the angle θa to the angle θb.

On the other hand, when the dimension of the ribbon beam B in the X direction decreases along the Z direction, the inner dimension of the vacuum chamber C in the X direction gradually narrows along the Z direction in the end region of the vacuum chamber C. It is constituted so that it becomes.
In this case, contrary to the above-described configuration, the conductive plate P is attached to the vacuum chamber C so that the angle gradually increases from the angle θb to the angle θa along the Z direction.

The embodiment of FIG. 8 is a configuration example of the mass analysis electromagnet 2, but may be applied to a beam optical element that changes the dimensions of the ribbon beam B other than the mass analysis electromagnet 2.
Further, although an example in which the beam dimension in the X direction changes has been described, the configuration of the end region of the vacuum chamber C may be changed according to the change in the beam dimension in the Y direction.

  When the ribbon beam B passes through the mass analysis electromagnet 2, Lorentz force acts on the ribbon beam B. The ribbon beam B has a width in the X direction, and is transported at different positions on the OUT side and the IN side of the mass analysis electromagnet 2 illustrated in FIG. 9A in the X direction. Since the beam transport distance is different between the OUT side and the IN side of the mass analysis electromagnet 2, the magnitude of the Lorentz force received when the ribbon beam B passes through the mass analysis electromagnet 2 is different between the OUT side and the IN side. Considering this point, the configuration example shown in FIG. 9 may be used.

Similarly to FIGS. 8A to 8D, FIG. 9A is a plan view showing how the beam diameter changes in the mass analysis electromagnet 2, and FIGS. 9B to 9D are diagrams. The state of the cross section in the BB line, CC line, and DD line of 9 (A) is drawn.
The component of the ribbon beam B that passes through the OUT side in the mass analysis electromagnet 2 has a longer transport distance in the mass analysis electromagnet 2, so the Lorentz force acting on the component is increased. On the contrary, the component of the ribbon beam B that passes through the IN side in the mass analysis electromagnet 2 has a short transport distance in the mass analysis electromagnet 2, and thus the Lorentz force acting on the component becomes small.

In consideration of the above points, the mounting angle of the conductive plate P is configured to be different between the left and right sides of the vacuum chamber C as illustrated in FIGS.
In these drawings, the relationship between the mounting angles of the conductive plate P is θa1> θa2, θa1> θb1, θa2> θb2, and θb1> θb2.

Since the component of the ribbon beam B that passes through the OUT side of the mass analysis electromagnet 2 is largely deflected toward the IN side by the Lorentz force, the beam spread due to the beam potential passes through the IN side of the mass analysis electromagnet 2. This is somewhat reduced compared to the beam spread due to the beam potential of the component B.
Considering this point, the attachment angle θa1 of the conductive plate P arranged on the OUT side is made larger than the attachment angle θa2 of the conductive plate P arranged on the IN side.

  With the above configuration, the beam spread due to the beam potential is larger on the OUT side than on the IN side, but on the OUT side, the deflection action due to the Lorentz force works toward the IN side. Alleviated. As a result, the degree of divergence due to the beam potential at both ends of the ribbon beam B in the X direction passing through the end region of the vacuum chamber C can be made substantially the same.

  In consideration of changes in the beam diameter as described in the embodiment of FIG. 8, in the configuration example of FIG. 9, the attachment angle of the conductive plate P is along the Z direction from the entrance to the center of the mass analysis electromagnet 2. The mounting angle of the conductive plate P may be gradually increased along the Z direction from the center to the outlet of the mass analysis electromagnet 2 so as to be gradually decreased.

  In the embodiment shown in FIG. 9, the ribbon beam B is swung clockwise, but conversely, the ribbon beam B may be swung counterclockwise. In this case, the relationship of the mounting angle of the conductive plate P is reversed on the left and right from the configuration example of FIG.

  Further, in the embodiments so far, in order to simplify the description, the ribbon beam B having a substantially uniform beam current distribution in the length direction and the mass analyzing electromagnet 2 having a substantially uniform magnetic field generated in the magnet are used. Although the description has been made on the assumption, it is not limited to these conditions. The present invention can also be applied to a configuration in which the beam current distribution and the magnetic field distribution are not uniform.

  In this case, in the configuration example of FIG. 9, what is the relationship between the left and right attachment angles of the conductive plate P is the optimum angle at which the non-uniformity in the length direction of the ribbon beam B is reduced. Whether it is possible is determined by various conditions such as a beam current distribution, a magnetic field distribution, and a beam turning angle.

  Regarding the configuration example of FIG. 9 and other similar configuration examples, generally speaking, in the transport path of the ribbon beam B in which the vacuum chamber C of the present invention is disposed, the vacuum chamber is at least partially in the transport path. The inner wall shape of C is configured to be asymmetric in the X direction with respect to the YZ plane including the center of the ribbon beam B.

The at least part of the transport path may be configured such that the shape of the inner wall of the vacuum chamber C is asymmetrical over the entire transport path in which the vacuum chamber C is disposed, or one of the transport paths in which the vacuum chamber C is disposed. This means that the shape of the inner wall of the vacuum chamber C may be asymmetrical.
The reason for adopting the above-described configuration is that the inner wall shape of the vacuum chamber C changes in some transport paths of the mass analyzing electromagnet depending on the beam current distribution of the ribbon beam B, the magnetic field distribution in the electromagnet, the turning angle of the beam, etc. This is because the inner wall shape of the vacuum chamber C can be symmetric in the X direction with respect to the YZ plane including the center of the ribbon beam B.

Here, the mass analysis electromagnet has been described as an example, but the same can be said for a deflection electromagnet having a difference in Lorentz force acting on the ribbon beam B in the X direction.
Further, the inner wall shape of the vacuum chamber C can be obtained even when the ribbon beam B whose end shape in the length direction is asymmetric in the X direction with respect to the Y direction including the center of the ribbon beam B passes through the vacuum chamber C of the present invention. It is conceivable to have an asymmetric configuration. Similarly, when the ribbon beam B having an end shape in the length direction that is asymmetric in the Y direction with respect to the X direction including the center of the ribbon beam B passes through the vacuum chamber C of the present invention, It is also conceivable that the inner wall shape is asymmetric with respect to the X direction including the center of the ribbon beam B.

  The various embodiments described so far may be combined as necessary. For example, the embodiment described in FIGS. 8 and 9 may be combined with the embodiment described in FIG. In many of the embodiments described so far, the conductive plate P is used. However, such a conductive plate P may be eliminated, and the inner wall shape of the vacuum chamber C may be changed as appropriate. In this case, the inner wall shape of the vacuum chamber C is not limited to the octagonal shape described with reference to FIG. 2B, and various shapes such as a polygonal shape such as a hexagonal shape and a dodecagonal shape, and an elliptical shape are used.

  Further, the various embodiments described so far have been described by taking the ion beam as an example of the ribbon beam B, but the present invention can also be applied to an electron beam.

Further, in the Y direction, the divergence due to the beam potential tends to be smaller at the end portion of the ribbon beam B than at the central portion. There may be cases where the divergence due to the beam potential is small.
In such a case, a conductive plate P corresponding to a predetermined position other than the end of the ribbon beam B may be added.

  In addition to the above, it goes without saying that various improvements and modifications may be made without departing from the scope of the present invention.

2 Mass spectrometry electromagnet B Ribbon beam C Vacuum chamber P Conductive plate V Power supply

Claims (7)

A vacuum chamber that forms the transport path of the ribbon beam,
When the traveling direction of the ribbon beam passing through the vacuum chamber is the Z direction, the length direction of the ribbon beam is the Y direction, and the direction orthogonal to both directions is the X direction,
A vacuum chamber in which the inner dimension of the vacuum chamber in the X direction becomes smaller toward the end of the vacuum chamber in the end region of the vacuum chamber in the Y direction.   As the dimension of the ribbon beam in the X direction varies along the Z direction in the end region of the vacuum chamber, the inner dimension of the vacuum chamber in the X direction varies along the Z direction. The vacuum chamber according to claim 1.   The vacuum chamber according to claim 1 or 2, wherein an inner wall shape of the vacuum chamber is asymmetric in the X direction with respect to a Y direction including a center of the ribbon beam.   The vacuum chamber according to any one of claims 1 to 3, wherein a plurality of conductive plates are arranged in an end region of the vacuum chamber.   The vacuum chamber according to claim 4, wherein potentials of the vacuum chamber and the conductive plate are different. The ribbon beam has a positive charge;
The vacuum chamber according to claim 5, wherein a potential of the conductive plate is lower than a potential of the vacuum chamber.   The mass spectrometry electromagnet provided with the vacuum chamber of any one of Claims 1 thru | or 6.