JPH056663U - Impregnated electrode type metal ion source - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an impregnated electrode type metal ion source capable of easily and stably controlling the temperature of the low melting point metal in the impregnated electrode with a relatively small electric power, and further miniaturizing the structure. To do. [Structure] An electric resistance material (2, 2) such as graphite is interposed between a pair of conductive holding members (1, 1) connected to respective through electrodes, and the electric resistance materials (2, 2) are brought into surface contact with each other to form a cylinder. The impregnated electrode 3 is sandwiched and heated by electric heat generation.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of an impregnated electrode type metal ion source in which a low melting point metal stored in a cylindrical container is heated to generate an ion beam.

[0002]

[Prior Art]

 This type of ion source has been conventionally used as an ion source for a focused ion beam device or the like, but the conventional one uses a cylindrical impregnating electrode 100 having a low melting point metal stored therein. As shown in FIG. 7, since a pair of conductive knife-edge type sandwiching plates 101, 101 and 102, 102 are sandwiched in a two-tiered configuration from above and below, each knife-edge type sandwiching plate 101, 101 101, 102, and 102 have openings 201 and 301 formed at the centers thereof, and two large and small support frames 200 and 300 having threads 202 and 302 formed at the outer circumference thereof, and openings 203 and 303 formed at the centers thereof. It is fixed by screwing the screw covers 204 and 304. Then, bolts 400 and 500, which serve as through electrodes, are screwed into these two supporting frame bodies 200 and 300, and these supporting frame bodies 200 and 300 are housed together with the impregnation electrode 100 in a vacuum container (not shown). ing.

Therefore, in such a structure, when a current is passed from the through electrodes 400 and 500, a current flows through the supporting frame bodies 200 and 300 to the impregnating electrode 100, and the impregnating electrode 100 serves as a heating element to generate heat. Therefore, the metal stored therein is heated and exudes from the porous portion 100b of the impregnated electrode 100, and a potential difference is generated between the tip of the needle 100c and the electrode (not shown) facing the needle 100c to cause electric field concentration. Ions are released.

[0004]

[Problems to be solved by the device]

 However, in such a conventional impregnation electrode type ion source, since the cylindrical impregnation electrodes are sandwiched by the upper and lower knife edges and energized to generate heat, there are the following problems to be improved. ..

First, in the impregnated electrode, the lower temperature of the impregnated electrode is lower than that of the portion sandwiched by the upper and lower knife edges, and the heating is not uniform, and the shape of the tip of the knife edge is changed. As a result, the contact resistance with the impregnated electrode also changes, making temperature control difficult. Such non-uniformity and instability of temperature greatly affect the emitted ion beam, and in extreme cases, the ion beam cannot be emitted.

Secondly, since a supporting frame having a two-stage structure for supporting the impregnated electrodes by the upper and lower knife edges is required, the structure becomes large. The present invention has been made in view of such circumstances, and an immersion electrode type in which the temperature of the metal in the impregnated electrode can be uniformly and easily controlled with a relatively small electric power and the structure can be downsized. It is intended to provide an ion source.

[0007]

[Means for Solving the Problems]

 According to the present invention proposed to achieve the above object, an electrically resistive material is interposed between a pair of conductive holders, and the electrically impregnated electrode is brought into surface contact to sandwich a cylindrical impregnated electrode. The structure is such that it is heated by energization.

[0008]

[Action]

 According to the present invention, when an electric current is applied from the through electrode, the cylindrical body of the impregnated electrode is energized through the surface-contacted electrical resistance material, and at this time, the electrical resistance material generates heat and the cylindrical body of the impregnated electrode is removed. To heat. Therefore, the metal stored in the tubular body is uniformly heated, the temperature control during metal heating is facilitated, and the metal can be efficiently heated with a small electric power.

FIG. 5 shows the resistance value of the electric resistance material used in the present invention and the temperature change of the impregnated electrode, and FIG. 6 shows the electric power supplied to the electric resistance material and the temperature rise change of the impregnated electrode. .. As is clear from these graphs, the relationship between the heating temperature of the impregnated electrode, the resistance value of the electric resistance material, and the electric power supplied to the electric resistance material is as follows. It can be seen that a linear characteristic is shown between ℃ and 900 ℃ (shown by the solid line in FIGS. 5 and 6). Therefore, by controlling the electric power applied to the impregnated electrode, the metal in the impregnated electrode can be heated and raised in a stable manner accordingly, and it is possible to heat with a small electric power without performing extra heating due to instability.

[0011]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. The impregnated electrode type metal ion source A of the present invention has a pair of electrically conductive holders 1 and 1 housed in a vacuum container (not shown) with a pair of electric resistance materials 2 and 2 interposed at the tips thereof. The structure is such that the impregnated electrode 3 is sandwiched between the electric resistance materials 2 and 2.

Here, as shown in FIG. 4, the impregnated electrode 3 is provided with a porous tungsten 32 at the tip of a cylindrical main body 31 made of a tungsten pipe or the like, and a low melting point metal 33 is provided thereon. The structure is such that a needle 34 is arranged at the tip of the porous tungsten 32 and the cylindrical main body 31 is covered with a cap 35. The pair of conductive holders 1 and 1 are formed by bending a metal plate having good conductivity into an L shape, and are fixed to a cover plate (not shown) of the vacuum container by bolts 6 and 6. It is composed of horizontal upper pieces 1a, 1a and vertically standing pieces 1b, 1b for holding the cylindrical impregnation electrode 3 from both sides with electric resistance materials 2, 2 interposed at the lower ends. The upper piece portions 1a, 1a are fixed by screwing bolts 6, 6 into a set of screw hole portions 7, 7 attached to the lid plate by metallization or the like. Then, these bolts 6 and 6 are formed with air vent holes 6c and 6c for venting air remaining in the screw hole portions 7 and 7 in order to maintain the degree of vacuum in the vacuum container. In addition, 6a is a screw thread of the bolt 6, and 7a is a screw groove of the screw hole portion 7.

In addition, in the example shown in the figure, a pair of bolts 6 and 6 for fixing the upper piece portions 1a and 1a of the pair of conductive holders 1 and 1 to the above-mentioned lid plate side connect the through electrodes. A current is supplied from a power source (not shown) arranged outside the vacuum container through the through electrodes 6 and 6, and the end surfaces 2a of the electric resistance materials 2 and 2 are Since 2a is adapted to hold the impregnated electrode 3 in surface contact therewith, it is formed into a curved surface that matches the outer peripheral surface of the impregnated electrode 3.

Further, in such a pair of conductive holders 1 and 1, the electric resistance materials 2 and 2 are interposed at the lower ends of the vertically sandwiched clip portions 1b and 1b, respectively. , 1b are tightened with bolts 4a and nuts 4b so that the cylindrical impregnated electrode 3 is held from both sides by the electric resistance materials 2, 2. For this reason, recesses 1c, 1c are provided in the lower portions of the sandwiching pieces 1b, 1b of the conductive holders 1, 1 and the end portions of the electric resistance materials 2, 2 are provided in the recesses 1c, 1c. The disk-shaped insulator 5, which is made of an insulating material, is inserted into the holes 1d and 1d formed in the sandwiching pieces 1b and 1b of the pair of conductive holders 1 and 1, respectively. 5 is inserted and is fastened with bolts 4a and nuts 4b with washers 8 interposed therebetween to hold the electric resistance materials 2 and 2 with a sufficient pressure contact force. Reference numeral 5a is a locking projection for fixing the mounting position of the disk-shaped insulator 5 to the sandwiching piece 1b, and this portion is fitted into the positioning hole 1d formed in the sandwiching piece 1b. Is becoming

The present invention having such a structure is not limited to the above-mentioned embodiment, and for example, bolts and nuts used for the supporting structure of the electric resistance material are provided with a loosening prevention means, or even pressure contact with the impregnated electrode. A spring may be used to provide the force. Further, although graphite is used as the electric resistance material in the above embodiments, it is not limited to this, and it goes without saying that an electric resistance material having electric resistance characteristics similar to those of Grafite may be used.

[0016]

As can be understood from the above description, according to the present invention, an electric resistance material such as graphite is interposed between a pair of conductive holders and the electric resistance materials are brought into surface contact with each other. Since the cylindrical impregnated electrode is sandwiched, the cylindrical body can be heated more uniformly according to the change in the resistance value of the electric resistance material than the conventional method, and the temperature rises with the supplied electric power. Since the change is linear and stable, temperature control is easy without the need for a thermometer, and power can be saved. Further, as compared with the conventional structure in which it is held by a knife edge, a supporting frame body having a two-stage structure is not required, so that the size and weight can be reduced.

[Brief description of drawings]

FIG. 1 is a front vertical cross-sectional structural view showing a main part of an impregnated electrode type metal ion source of the present invention.

FIG. 2 is a bottom view of a conductive holder having an impregnated electrode sandwiched therebetween.

FIG. 3 is a side view of a conductive holder in which an impregnated electrode is sandwiched.

FIG. 4 is a vertical sectional view of an impregnated electrode.

FIG. 5 is a graph showing a resistance value of an electric resistance material serving as a heating element and a temperature change of an impregnated electrode in the present invention.

FIG. 6 is a graph showing changes in temperature of an impregnated electrode and electric power supplied to an electric resistance material serving as a heating element in the present invention.

FIG. 7 is a structure explanatory view of a conventional knife edge type impregnated electrode type ion source.

[Explanation of symbols]

 A: Impregnated electrode type metal ion source of the present invention 1 ... Conductive holder 2 ... Electrical resistance material 3 ... Impregnated electrode

Claims (1)

[Claims for utility model registration] [Claim 1] A cylindrical impregnation electrode is sandwiched by interposing an electric resistance material between a pair of conductive holders so that the electric resistance material is in surface contact, and the impregnation is performed. Impregnated electrode type metal ion source with a structure in which the electrodes are energized and heated.