JPS6081746A - Electron beam generator - Google Patents

Abstract

PURPOSE:To enable both the density distribution of a beam current and the level of the beam current to be effectively controlled by installing a cathode having a long electron-discharging surfase, the first grid having the same electric potential as the cathode and the second grid having an electric potential independent of the electric potential of the first grid. CONSTITUTION:The central hole 8 of the first grid 6 has a rectangular shape similare to the shape of an electron-discharging surface 2. The central hole 9 of the second grid 2 has a circular shape. The middle point between resistances 11 and 12 is electrically shorted from the first grid 6, so that the electron-dischargint surface 2 and the first grid 6 have almost the same electric potential. To the second grid 7, a bias voltage positive or negative to the electron-discharging surface 2 and other parts is applied from a variable d.c. bias power supply 13. The anode 4 is made to have a high electric potential positive to the electron-discharging surface 2 by a d.c. high voltage power supply 13. Owing to the above constitution, it is easily possible to properly adjust the magnitude of a beam current, the current density distribution in the cross section of the beam current and the shape of a beam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam generator that generates an elongated electron beam with a rectangular cross section and irradiates it onto materials such as dielectrics, semiconductors, and metals to melt, heat treat, change physical properties, etc. It is something.

For example, when heat-treating (annealing) a semiconductor wafer with an electron beam having a rectangular cross section, a relatively wide area can be treated at once by moving the electron beam and the wafer relative to each other in the short side direction of the electron beam.

However, such an advantage is that the current density distribution in the long side direction of the electron beam is, for example, uniform, and in order to process the electron beam in a short time, the value of the total beam current is as large as possible, and stability and reproducibility are sufficient. Or, it can only be realized if the condition that some kind of correction can be made is satisfied. To construct this type of device, it is conceivable to use a triode electron gun consisting of a cathode, a grid, and an anode. In this case, the method to adjust the beam current is as follows:
Adjustment can be considered by changing the potential of the grid. In this method of adjusting the grid potential, the bias of the grid is changed according to the beam current, so
There is a problem in that the electric field distribution changes and the current density distribution in the cross section of the electron beam changes17. Furthermore, this type of device usually uses a so-called demountable electron gun in which the cathode can be replaced, but the current density distribution changes each time the cathode is replaced, and some kind of correction means is required.

In order to eliminate these drawbacks, the present invention provides a first grid having the same potential as the cathode, and a second grid having a potential independent of the above potential, thereby adjusting the cross-sectional shape of the electron beam (beam current density distribution) and the beam. This allows both current values to be effectively adjusted (corrected), and will be described in detail below with reference to the drawings.

FIG. 1 is a schematic side cross-sectional view of an electron gun portion of an embodiment of the apparatus of the present invention, and FIG. 2 is a schematic plan view viewed upward from line AA' in FIG. In these figures, a group of electrons 3 emitted from an elongated electron emitting surface 2 of a cathode 1 is connected to a high potential anode 4.
It is pulled out and accelerated and passes through the center hole (circular hole in this example) 5 of the anode 4. The first grid 6 closest to the cathode 1 plays a major role in determining the magnitude of the current value (beam current) of the electron group 3 that can be extracted from the electron emission surface 2 and the emission current density distribution. On the other hand, the first
The second grid 7 located around the grid 6 or in the intermediate region between the first grid 6 and the anode 4 has the function of auxiliary adjustment of the emission current density distribution of the electron emission surface 2 and also controls the electron group. 3 outline shape (child beam shape,
It plays a major role in determining and correcting the beam angle and divergence angle.

In the electron gun of this embodiment, the center hole 8 of the first grid 6 has a rectangular shape similar to the electron emission surface 2, as shown in the planar positional relationship seen from the anode side in FIG. Although the center hole 9 is circular, any other shape may be selected. Further, in FIG. 1, a cathode heating DC power supply 10 adjusts the temperature of the electron emission surface 2 and controls the current value of the electron group 3 (in the so-called temperature limited region). resistance 11
Since the midpoint between and 12 electrically shorts the first grid 6, the electron emitting surface 2 and the first grid 6 are at approximately the same potential. The second grid 7 is connected to a variable DC bias power supply 13,
A negative or positive bias voltage is applied to the electron emitting surface 2 and the like as shown in the figure. The anode 4 is brought to a positive high potential with respect to the smitter emitting surface 2 by a DC high voltage power supply 14 .

Thus, when the temperature of the electron emitting surface 2 in vacuum is raised by the cathode heating power supply 10, the upper limit of the beam current that can be extracted is mainly determined by the shape and arrangement of the electrodes of the first grid 6. ) The beam current density distribution can be corrected or optimized by adjusting the bias voltage of the second grid 7, electrode shape, or relative position without causing problems such as a large drop in beam current. Therefore, when it is necessary to process a substance by changing the beam current level, when using a different type of cathode, or when there is a change in the shape of the cathode over time and you want to compensate for changes in the electron emission situation due to this, etc. First, by using an electron gun having the structure of this embodiment, the magnitude of the beam current, the current density distribution in its cross section, and the beam shape can be easily optimized.

3, 4, and 5 are other embodiments of the electron gun for the device of the present invention, and elements corresponding to those shown in FIGS. 1 and 2 have the same numbers. It shows. In FIG. 3, the center hole 9 of the second grid 7 has a special shape as shown in the figure, and when a negative bias voltage is applied to it, electron emission from the center of the electron emitting surface 2 is slightly suppressed, and the center hole 9 near both ends is slightly suppressed. The current density distribution in the cross section of the electron beam can be adjusted so as to relatively encourage electron emission. on the other hand.

The electron gun shown in FIG. 4 uses a ring-shaped N''l with a circular cross section as the second grid, and controls the contour shape of the shim group 2 by adjusting its potential (bias voltage). The electron gun having the structure shown in the schematic diagram (bottom view of the cathode-first grid-second grid portion) has six cylindrical columns 1.2 as the second grid 7 whose axial direction coincides with the traveling direction of electrons.
The poles are arranged symmetrically, and potentials (same potential or different potentials) are applied to each of these electrodes to correct the shape of the electron beam cross section or the current density distribution in the cross section.

The electron gun of the device of the present invention and some embodiments thereof have been described above, but in addition to this method, the generated electron beam can be controlled by an electrostatic electron lens, a magnetic lens, an astigmatism correction system, a beam trajectory correction system, etc. Even if the shape of the electron beam is controlled using, for example, the material can be sufficiently processed.

[Brief explanation of drawings]

1 and 2 are a partial schematic diagram and a partial plan schematic diagram, respectively, of one embodiment of the device of the present invention, FIGS. 3 and 5 are partial diagrammatic diagrams of two other embodiments, and FIG. 1 is a schematic partial side cross-sectional view of an embodiment; FIG. DESCRIPTION OF SYMBOLS 1... Cathode, 2... Electron emission surface, 3... Electron group, 4... Anode, 5... Center hole of anode. 6... 1st grid, 7... 2nd grid, 8...
... center hole of the first grid, 9 ... center hole of the second grid, 10 ... DC power supply for cathode heating. 11.12...Resistor, 13...Variable DC bias power supply, 14...DC high voltage power supply.

Claims (1)

[Claims] a cathode having an elongated electron emitting surface; a first grid adjacent to the cathode and having the same potential as the cathode; and a first grid located at a distance from the cathode by a distance of 4, An electron beam generator comprising: a second grid to which a potential is applied independently from the first grid; and an anode for extracting and accelerating electrons from the cathode.