JPS5966118A - Plasma x ray source - Google Patents

Abstract

PURPOSE:To improve dielectric strength and to increase the amount of X rays that can be taken out, by providing intermediate electrodes, which have through holes that agree with the through hole of an insulator, at the intermediate part of the insulator, and a means, which applies the voltages that are obtained by dividing a discharge voltage to be applied across electrodes to the intermediate electrodes. CONSTITUTION:Two intermediate electrodes 6 and 7, which have through holes whose center agrees with that of the through hole of an insulator 1, are provided at the intermediate part of the insulator 1, with an interval being provided. Voltages, which are obtained by dividing the voltage across electrodes 2 and 3 by resistors r1-r3, are applied to the intermediate electrodes 6 and 7. A trigger signal T is supplied to one intermediate electrode 6 from a trigger circuit. Since the voltages obtained by dividing the voltage across the electrodes 2 and 3 are applied to the intermediate electrodes 6 and 7, respectively, electric field inclination in a capillary becomes uniform. The part, wherein the electric field is concentrated or becomes unstable, does not exist. Therefore, the dielectric strength between the electrodes 2 and 3 becomes very high in comparison with a device, wherein divided voltages are not applied to intermediate electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma x-ray source suitable for implementing x-ray based techniques such as x-ray lithography.

In X-ray lithography and the like, an apparatus that generates X-rays with extremely large bullet holes is desired, and in order to meet this demand, a plasma X-ray source as shown in FIG. 1 has been proposed. In the figure, 1 is a cylindrical insulator made of polyethylene, for example;
1a is a through hole (capillary) with a diameter of about 11 m and a length of 20 u, 2 is a ground electrode made of carbon, for example,
3 is a high-voltage electrode also made of carbon, 4 is a cathode also made of carbon, R1 and R2 are resistors, Cb and Cd are capacitors, 5 is a high-voltage power supply, e is an electron beam, and PQ is a plasma. and at least an insulator 1. Electrode 2.
3. and cathode 4 are placed in a high vacuum container.

In the illustrated device, capacitors Cd and cb are each charged by increasing the voltage generated by power supply 5. When the charging voltage of the capacitor Cd exceeds the dielectric strength between the electrodes 3.2, discharge occurs between the electrodes 3.2. The discharge takes the form of a creeping discharge that travels along the inner wall of the capillary 1a, and this discharge evaporates the insulating material and forms plasma of carbon, hydrogen, etc. in the capillary. At the same time, the potential of the high voltage electrode 3 becomes approximately the ground potential, so the cathode 4
The electric field at the tip becomes stronger, and an electron beam is generated from that part. This electron beam hits the plasma while self-pinch, and when it combines with the plasma, the energy of the plasma and ions increases, and the plasma density also increases, resulting in the emission of powerful X-rays in a pulsed manner. It is something that will be done.

In this proposed device, the potential distribution in the capillary is given by the potentials of electrodes 2 and 3, but because the distance between them is short, about 20 ms, it is easy to become unstable due to the effects of space charges, etc., so the dielectric strength of the capillary is It is inevitable that the Therefore, discharge started at a low voltage, making it impossible to increase the X-ray dose.

The present invention has been made in view of this point, and an intermediate electrode having a through hole that matches the through hole of the insulator is interposed between the insulators, and an electric voltage is applied between the electrodes 2 and 3 to the intermediate electrode. By providing a means for applying a voltage obtained by dividing the discharge voltage, it is possible to completely improve the dielectric strength voltage and increase the amount of X-rays that can be taken out. Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 2 is a sectional view showing the configuration of an embodiment of the present invention,
What is different from the proposed device shown in FIG. 1 is that two intermediate electrodes 6 and 7 having a through hole whose core coincides with the through hole of the insulator are interposed at a distance between each intermediate electrode. Electrode 2
．． 3 is applied by dividing the voltage between them by the resistors '1+rz+r3, and at the same time, a trigger signal T is supplied to one intermediate electrode 6 from a trigger circuit (not shown).

With such a configuration, the voltage obtained by dividing the voltage between the electrodes 2 and 3 is applied to the intermediate electrodes 6 and 7, respectively, so that the electric field gradient inside the capillary becomes uniform, and the electric field is neither concentrated nor uneven. There is no longer any part that would be stable. Therefore electrode 2.3
The dielectric strength between the two electrodes is extremely high compared to the device shown in FIG. 1 in which no divided voltage is applied to the intermediate electrodes. As a result, in this embodiment, the voltage that can be applied between the electrodes 2 and 3 can be increased.1. Due to the high applied voltage, it is possible to extract a large amount of X-rays. According to experiments conducted by the present inventors, it has been confirmed that while the discharge voltage in the apparatus shown in FIG. 1 was 42 KV on average at a vacuum pressure of 10-2 Pa, it was increased to 60 KV or more in this example.

Furthermore, in the device shown in Figure 1, since the discharge between the electrodes 2 and 3 is a creeping discharge in a vacuum, the discharge starting voltage is
It shows a variation of 30%. This variation in discharge voltage is
This results in variations in the amount of X-rays generated, which is the final output. On this point, in this embodiment, since the trigger signal can be applied to the intermediate electrode 6, when the capacitor Cd starts creeping discharge and is charged to a constant voltage of μ, if the trigger signal - is applied, Due to this signal, the electric field inside the capillary shows a sudden change, which starts the main discharge between the electric fi2 and 3. Therefore, since the discharge can always be started at a constant voltage, the amount of X-rays generated is constant every time. becomes.

Furthermore, the present invention is extremely advantageous in terms of insulation consumption. In the device of FIG. 1, capacitor Cd.

When each cb is 100 nF and the discharge voltage is 40 KV, the increase in the inner diameter due to consumption of the capillary per discharge reaches approximately 10-. In other words, the inner diameter of the capillary will change from 1111 m to 2 ms by about 1°0 discharges, and larger electrical energy will be injected.
The problem becomes even more serious when attempting to extract a larger amount of X-rays, as this consumption increases even further.

In this regard, in this embodiment, the capacitances of capacitors Cd and Cb are
When the discharge voltage and capillary shape are the same as in Figure 1, the consumption of the insulator is less than 1/2. In particular, when the inner diameter exceeds 2 mm, the rate of wear is further reduced. For example, the number of discharges required until the inner diameter of the through hole reached 3 mm was approximately 200 times in the apparatus shown in FIG. 1, and over 500 times in this example. The reason why the consumption of the capillary is reduced in this way is considered to be the shielding effect of the intermediate electrode, since the consumption of the intermediate electrode portion is less than that of the insulator.

FIG. 3 shows the configuration of another embodiment that actively utilizes this shielding effect. In this embodiment, the inner diameter of the through hole in the insulator is made larger from the beginning than the inner diameter of the through hole drilled in the electrode. It is. Therefore, the consumption of the capillary is extremely reduced from the beginning of use, the fluctuation in the amount of X-rays generated for each discharge is reduced, and the life of the capillary can be extended.

Incidentally, consumption of the capillary beyond its limit or deterioration of insulation due to adhesion of conductive electrode material to the insulator both determine the lifespan of the device. FIG. 4 shows the configuration of another embodiment that takes this point into consideration. In this embodiment, the insulator 1 and the intermediate electrode 6.7 are sandwiched between the electrodes 2.3 via the packing P, and the electrodes 2.3 are connected to the insulating bolts B and the nuts N
The cathode 4 is attached to the electrode 3, so that the parts involved in discharge can be disassembled and reassembled. Therefore, it is possible to replace only the portions that are significantly deformed or have significantly deteriorated insulation properties, and the life of the device can be further extended.

In this embodiment, the vacuum range is limited to a very narrow area including the capillary, so the structure is simple and it is advantageous in terms of cost. Further, the area outside the insulator may be filled with an insulating gas atmosphere such as SFg to improve the withstand voltage.

Note that the present invention is not limited to the embodiments described above, and can be modified in many ways. For example, in the above embodiment, polyethylene was used as the insulator and highly conductive carbon was used as the electrode material, but alumina porcelain may be used as the insulator and aluminum may be used as the electrode material.In short, any combination of an insulator and a conductor may be used. However, the material does not matter. Highly conductive carbon for the electrode material and low conductive carbon for the insulator (e.g. diamond fiI)
It is also possible to use carbon with good crystallinity, in which case only pure carbon molecules will form plasma in the capillary, reducing the generation efficiency of X-rays extracted from the plasma. It becomes possible to improve the performance. The reason is that when the insulator is polyethylene, the ratio of carbon to hydrogen generation is approximately 1:2, and this hydrogen component absorbs plasma energy or the generated X-rays. This is because such absorption is eliminated, while limiting the efficiency of X-ray generation.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a 4i structure of the proposed device, and FIGS. 2 to 4 are sectional views showing the structure of an embodiment of the present invention. 1: Insulator, 2: Ground electrode, 3. :High voltage electrode, 6.7:
Intermediate electrode, rt, rz, r3: voltage dividing resistor T: trigger signal.

Claims (1)

[Claims] 1. An insulator having a through hole, a pair of electrodes facing each other with the insulator in between, means for applying a discharge voltage between the electrodes, and positions of the electrodes along the opposing direction. A plasma X-ray source comprising: a cathode disposed to face the electrode; and means for applying a discharge voltage between the cathode and an electrode located further away from the electrode pair; A plasma X-ray source, characterized in that an intermediate electrode is interposed between the insulators, and means for applying a divided voltage of the discharge voltage applied between the electrodes to the intermediate electrode. 2. The plasma X-ray source according to claim 1, further comprising means for applying a trigger voltage to the intermediate electrode. 3. Claim 1 or 2, wherein the inner diameter of the through hole in the insulator is larger than the inner diameter of the through hole in the intermediate electrode.
Plasma X-ray source as described in section. 4. Claim 1 or 3'll using high conductivity carbon as an electrode material and low conductivity carbon as an insulating material
The plasma X-ray source according to any one of the above.