JPH0143809Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an electron beam source that can freely control the temperature distribution on the emission surface.

[Prior Art] Recently, electron beam exposure apparatuses have been attracting attention as a means of manufacturing LSI devices and VLSI devices. especially,
It is equipped with a plurality of slit plates having polygonal holes and a deflection system placed between each of the slit plates to deflect the electron beam that has passed through the holes in the upper slit plate. ) Variable area electron beam exposure equipment that attempts to obtain an electron beam with a cross section of Since the pattern is drawn in one step or by connecting multiple times (referred to as area exposure), it is seen as promising because it is significantly superior in terms of drawing speed and drawing accuracy.

Now, in such a variable area electron beam exposure system, it is necessary to make the current density of each square beam uniform, so an electron beam source with a cathode with a wide electron emission surface (referred to as an emission surface) is desired. There is. However, conventional electron beam sources heat a rod-shaped cathode material and emit thermoelectrons from the emission surface of the material. It was difficult to make the heating temperature uniform over the entire surface, and it was not possible to make the amount of thermionic electrons emitted from each part of the emission surface uniform. Even if a beam with a cross section of a predetermined shape and size is created from the electron beam emitted from such an emission surface,
Since the electron density differs depending on the location of the cross section, it is difficult to obtain a beam with a uniform current density. In such cases, when the beam is irradiated onto the resist surface coated on the sample and developed in order to draw a pattern directly on the sample, for example, when a positive resist is used, the current density is lower than the sensitivity of the resist. If the area hit by a beam with a current density remains as it is, or if a beam with a current density higher than the sensitivity hits, the edges of the pattern may be There will be a portion nearby that will be developed together with the pattern portion. Therefore, pattern drawing accuracy is significantly reduced.

[Problems to be solved by the invention] The purpose of the present invention is to solve such problems.

[Means for Solving the Problems] For this purpose, the electron beam source of the present invention includes an electron emission surface and a large number of pairs of conductive parts at both ends of the emission surface in one direction for guiding heating current to the emission surface. A hot cathode having no conducting portion was provided at both ends in a direction perpendicular to the above direction, and means for individually controlling the heating current flowing through each of the conducting portions was provided.

[Embodiment] FIG. 1 shows a hot cathode section of an electron beam source showing an embodiment of the present invention. The hot cathode part includes a rectangular electron emission surface 1 and a conductive plate for guiding heating currents I ₁ , I ₂ , I ₃ , I ₄ , I ₅ , and I ₆ from heating power sources not shown to the electron emission surface. It has L ₁ , L ₂ , L ₃ , L ₄ , L ₅ , and L ₆ . The electron emitting surface and the conductive plate are initially formed into an integrated flat plate, and the cathode section shown in Fig. 1 is manufactured by mechanically punching out the area A between each conductive plate. . The cathode section shown in FIG. 1 is bent at the dotted line in the drawing to form the shape shown in FIG. 2, and then mounted on an electron beam drawing device or the like. Although not shown outside the cathode section, the heating power source, a heating current control circuit for individually controlling the heating current flowing from the power source to each of the conductive plates, and below the electron emitting surface 1 are arranged. An acceleration power source for accelerating thermoelectrons emitted from the electron emitting surface is provided between the anode (not shown) and the electron emitting surface.

_{In the} electron beam source configured _in this way _{, I 1 ,} I ₂ , I ₃ ,
Send heating currents I ₄ , I ₅ , and I ₆ . As shown in FIG. 1, each heating current flowing through each conductive plate flows from the inflow side of each conductive plate (left side of electron emitting surface 1) to the outflow side of each conductive plate through the electron emitting surface. Assuming that the current values flowing through each conductive plate are all constant, the temperature distribution in the direction perpendicular to the direction of current flow on the electron emission surface 1 is such that heat escapes due to radiation near the side edges of the electron emission surface 1. As shown in Fig. 3a, the closer to the side edge of the electron emitting surface 1 the lower the temperature, and the farther away from the side edge the heat is trapped. It gets a little expensive.

Similarly, when the current values flowing through each conductive plate are all constant, the temperature distribution in the direction of current flow on the electron emission surface 1 is as follows, since each conductive plate is connected to the terminal of the heating current control circuit. A temperature gradient occurs around the boundary between the electron emitting surface 1 and the conductive plate due to the escape of heat due to conduction to the terminal, but there is no significant temperature difference elsewhere, so There is not much difference in temperature between the area away from the conductive plate. Therefore, the temperature distribution near the side edge of the electron emitting surface 1 is as shown in Figure 3b.
The part far from the side edge of the electron emitting surface ₁ becomes as shown in b ₂ of Figure 3 b, and the middle part becomes as shown in b ₃ of Figure 3 b. .

Furthermore, at this time, each conductive plate L ₁ , L ₂ , L ₃ , L ₄ , L ₅ , L ₆
Heating current flowing on the inflow side of I ₁ , I ₂ , I ₃ , I ₄ , I ₅ , I ₆
follows various paths depending on the resistance value at each location on the electron emission surface 1, but naturally, each conductive plate L ₁ , L ₂ ,
Heating currents I ₁ , I 2 , I ₃ , I ₄ , I ₅ , and I 6 flow on the outflow sides of L ₃ , _{L 4} , L ₅ , and L ₆ , which are the same as the heating currents flowing on the inflow _sides . At this time, as shown in FIG.
A focusing lens 12, a deflection device 13, an aperture plate 14, and a beam current detector 15 such as a Faraday cup are arranged below an electron beam source 11 consisting of an electron beam source 11, a Wehnelt 19, and an anode 20, and the aperture plate 14 is scanned with a beam. The beam current passing through the aperture of the aperture plate is detected by the current detector 15, and the beam current density distribution on the aperture plate 14 is measured by the current density distribution measuring device 16. For example, each time the beam is shifted little by little in the current flow direction (X direction), the beam scans the aperture plate 14 many times in the same Y direction. Then, during each Y-direction scan, the beam current density distribution in the beam cross section on the aperture plate 14 in the direction perpendicular to the direction of current flow on the electron emission surface is measured by the current density distribution measuring device 16. hand,
Perform the following operations. That is, for each scan in the Y direction, a beam current density distribution with a waveform similar to the temperature distribution shown in FIG. , the heating current control circuit 17 connected to the density distribution measurement device 16 controls the heating current control circuit 17 connected to the density distribution measurement device 16 to control the current flow to each conductive plate of the hot cathode section 18 of the electron beam source 11 so that the shape of the density distribution becomes a linear shape at level S. control the magnitude of the heating current. By doing this, the temperature distribution in the direction perpendicular to the direction of current flow on the electron emission surface 1 becomes linear at level S' corresponding to level S. Note that it is possible to adjust the level once without moving the beam in the X direction, but as explained above, the beam may be moved intermittently in the X direction and the level adjusted each time several times. The more you repeat, the better the accuracy will be. Also, each time the beam is shifted in the Y direction, the beam scans the aperture plate 14 many times in the same X direction, and each
During the direction scanning, the beam current density distribution in the direction of current flow on the electron emission surface of the beam cross section on the aperture plate 14 was measured by the current density distribution measuring device 16, and is shown in FIG. 3b. The hot cathode portion of the electron beam source 11 is controlled by the heating current control circuit 17 connected to the density distribution measuring device 16 so that the level of the beam current density distribution having a waveform similar to the temperature distribution becomes a straight line S. The magnitude of the heating current flowing through each of the 18 conductive plates may be controlled.

By such an operation, approximately the same number of thermoelectrons can be emitted from each part of the electron-emitting cotton of the hot cathode 18. Incidentally, depending on the purpose of use, the amount of thermoelectrons from each part of the electron emitting surface can be controlled to be different as appropriate.

[Effects of the invention] According to the invention, the temperature distribution on the emitter surface can be freely controlled, so that, for example, the amount of thermoelectrons from each part of the emitter surface can be made uniform.

[Brief explanation of the drawing]

1 and 2 show the hot cathode part of an electron beam source showing an embodiment of the present invention, FIGS. 3a and 3b show the temperature distribution of the electron emission surface, and FIG. 4 shows an example of a device for uniformizing thermionic emission from various parts of the electron emitting surface. 1: Emission surface, I ₁ , I ₂ , I ₃ , I ₄ , I ₅ , I ₆ :
Heating current, L ₁ , L ₂ , L ₃ , L ₄ , L ₅ , L ₆ : Conductive plate, 1
1: Electron beam source, 12: Focusing lens, 13: Deflection device, 14: Aperture plate, 15: Beam current detector, 16: Current density distribution measuring device, 17: Heating current control circuit, 18: Hot cathode section, 19 : Wehnelt, 20: Anode.

Claims (1)

[Scope of utility model registration request] It has an electron emitting surface and a large number of pairs of conductive parts at both ends of the emitting surface in one direction for guiding a heating current to the emitting surface,
An electron beam source comprising: a hot cathode having no conductor at both ends in a direction perpendicular to the direction; and means for individually controlling heating current flowing through each conductor.