JPS63218131A - X-ray generating device - Google Patents

Abstract

PURPOSE:To realize a long service life of a plasma X-ray source by using a high melting point metal or high melting point metal alloy for the electrode to which a high density plasma of the plasma X-ray source contacts. CONSTITUTION:In an X-ray generating device to generate X-rays from plasma produced by making a large current flow between a pair of electrodes 4A and 4B, at least portions 4C exposed to the plasma of the pair of electrodes are composed of one of tungsten, tantalum, molybdenum, vanadium, niobium, rhenium, and zirconium, or an alloy of two or more of them. By using such a high melting point metal or a high melting point metal alloy for the electrode which contacts to a high density plasma of a plasma X-ray source, the consumption of the electrode is reduced extremely. Therefore, as well as the electrode life of the plasma X-ray source is extended extremely, a damage of the X-ray pickup window is decreased, and the long service life of the plasma X-ray source is realized.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is an X-ray exposure source for semiconductor integrated circuit button transfer. This invention relates to an X-ray source using density plasma.

[Prior art] As an X-ray source that uses high-temperature, high-density plasma, a laser-excited plasma X-ray source that instantaneously irradiates a narrowly focused laser onto metal to form high-temperature, high-density metal plasma and discharge plasma. There are plasma X-ray sources that utilize Laser-excited plasma X-ray sources are impractical because they evaporate metal, so contamination of the X-ray extraction window is a problem.

On the other hand, the plasma X-ray source A source that uses a discharge method includes a plasma focus that uses creeping discharge on the surface of an insulator to form a high-temperature, high-density plasma of an inert gas, and a plasma X-ray source that uses a discharge method to instantaneously inject gas between electrodes. There are gas injection plasma X-ray sources.

Plasma focus uses the structure of the insulator for discharge, so there is a problem that T, poles or consumables may adhere to the surface of the insulator due to the discharge, causing insulation failure on the surface of the insulator, and it may not last for a long time. It is difficult to form stable high-temperature plasma. Therefore, plasma focus type plasma
In principle, it is difficult to obtain a stable X-ray source with a long life.

Currently, the most efficient and long-life plasma X-ray source is the gas injection plasma X-ray source. This type of X-ray source is miniaturized for use in X-ray exposure, etc.
ELL Research Institute (J, S, Pearl+nan etal
,: J, Vac, Sci, Technol, .
vol, 19. No. 4 (1981) P-1190
), NTT (1,0kada et al.: J.
Vac.

Sci, Technol, vol, B4. N
1 (1985) P-243). The basic circuit configuration of this X-ray source is shown in FIG. In the figure, 1 is a capacitor, 2 is a switch, 3 is a high-speed opening/closing gas valve, 4 is an electrode, 5 is a power transmission board, 6 is an insulating board, 7 is a vacuum container, 8 is an X-ray extraction window, 1
00 is an injected gas mass, 101 is a pinched high-temperature, high-density plasma, +02 is an X-ray, and 103 is a magnetic field.

By opening the high-speed opening/closing valve 3, a cylindrical gas mass +
00 is formed between the electrodes 4.4, the switch 2 is closed, a high voltage is applied across the electrodes 4.4, and a discharge occurs. Due to the discharge, conduction occurs between the electrodes, and a large current of about 300 flows, which generates a magnetic field 103. This 6n field causes the plasma to converge at the center, forming a pinched high-temperature, high-density plasma 101. do. X-rays 102 are generated from this plasma. As mentioned above,
Because a large current flows between the electrodes and the electrodes are directly exposed to high-temperature, high-density plasma, the 7M, 4'4 wear was a problem in extending the lifespan of the wooden sword method.

To solve this problem, we decided to replace the conventionally used copper electrode with A, which has a proven track record as a switch material for large currents.
g-W alloy, (: u-W alloy, carbon is being used. However, in the case of Ag-W alloy, Cu-W alloy,
Ag and Cu in the alloy evaporated and no significant improvement was observed. On the other hand, in the case of carbon electrodes, no evaporation is observed, but because the material strength is low, there is a problem that the electrode material is scattered by small pieces due to thermal stress. As described above, conventional electrodes have a short lifespan, and the materials constituting the electrodes have the problem of contaminating the inside of the vacuum container.

On the other hand, there is also a configuration in which the portion directly exposed to high-temperature plasma, which is the biggest cause of electrode wear, is removed in a cylindrical shape.

FIG. 4 is a configuration diagram showing the electrode portion of such a configuration. In FIG. 4, a high temperature plasma 10 is placed in the center of the upper electrode 4.
1 is provided with a hole 9 for letting it escape. By adopting such a structure, excess plasma after X-ray generation can be removed through this hole, thereby reducing electrode wear. However, at present, such improvements cannot completely eliminate electrode wear.

[Problems to be Solved by the Invention] As described above, conventionally, an alloy of a low melting point metal and a high melting point metal is used in part or in whole, and the heat resistance of the alloy is low, resulting in large consumption. On the other hand, when carbon is used for the electrode, the strength is low, so small cracks occur on the electrode and small pieces are generated.

It is an object of the present invention to overcome these conventional drawbacks and to provide an X-ray generating device that exhibits significantly less electrode wear, has a long life, and is stable.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an X-ray generator that generates X-rays from plasma generated by passing a large current between a pair of electrodes. At least the part exposed to plasma is tungsten, tantalum, molybdenum, and vanadium.

It is characterized by being composed of one of niobium, rhenium, and zirconium, or an alloy of two or more of tungsten, tantalum, molybdenum, vanadium, niobium, rhenium, and zirconium.

[Function] According to the present invention, by using a refractory metal or an alloy of refractory metals in the electrode portion of the plasma X-ray source that comes into contact with high-density plasma, electrode wear is extremely reduced. Source electrode.

The lifespan is significantly extended, and the damage to the X-ray extraction window is reduced, resulting in a longer lifespan for the plasma X-ray source and dramatically improved reliability.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings.

Example 1 FIG. 1 is a diagram illustrating a first example of the present invention,
4A is an upper electrode, 4B is a lower electrode, 4C is a film coated with a high melting point metal on the electrode, 5 is a power transmission plate, 6 is an insulating plate, 100 is an injected gas mass, 101 is a pinched high-temperature, high-density plasma , 102 is an X-ray, and 103 is a magnetic field.

The electrodes 4A and 4B of this embodiment are made of stainless steel, and are coated with M in a reduced pressure atmosphere (several Toprr). was plasma sprayed to form an M0 film 4C. The outer diameter of the upper electrode 4A is 2 (1 to 50 mm), and the outer diameter of the lower electrode 4B is 10 mm.
It was within 0n++a, and plasma spraying could be performed relatively easily. The thickness of the coating film formed by plasma spraying is 1 mm. The consumption amount in 1 million discharge tests (1 discharge time 200~3QQ n5cc) is 300μ
m or less, and its surface was extremely smooth.

As described above, when a molybdenum coating film is used, an electrode life of 3 million cycles or more can be guaranteed, which is a significant improvement over conventional electrodes.

Example 2 As in Example 1, tungsten powder and tantalum powder were plasma sprayed onto a stainless steel electrode to form a coating film of an alloy of tungsten and tantalum. As a result, the amount of electrode wear is 100μ after 1 million life tests.
m or less, and M shown in Example 1. We achieved a longer lifespan than that of membranes.

The material to be thermally sprayed is molybdenum M. (Melting point=262
5℃), Niobium Nb (2500℃), Rhenium Re (
3170℃), tantalum Ta (3000℃), vanadium V (1735℃), tungsten W (3410'e
) and zirconium Zr (1750°C) have almost the same effect.

The melting point mentioned above is obtained from "Table of Physical Constants" edited by Iida et al.
All of these metals have melting points of about 2000 K or higher, so they are stable even when exposed to high-temperature plasma. Ruthenium R is a metal with a melting point above 2000
u, rhodium Rh, osmium Os, iridium Ir,
Although platinum (Pt) is available, these platinum group metals are expensive, and although they can be used for electrodes, they are not preferred in terms of cost. Although titanium has a melting point of over 2000, it has a high vapor pressure and is rapidly consumed at high temperatures.

Embodiment 3 FIG. 2 shows another embodiment of the present invention. In FIG. 2, 4 shoulders are the base of the upper electrode, 4D is a portion of the upper electrode made of a high melting point metal exposed to plasma, 4E is a lower electrode made of a high melting point metal, and 5 is a power transmission plate.

The base portion 4A of the upper electrode is made of stainless steel, the portion 4D of the upper electrode exposed to plasma is made of tungsten, and the lower electrode 4E is made of tungsten. Electric discharge machining was used to process the tungsten, and silver brazing was used to connect the stainless steel part 48 of the upper electrode to the tungsten part 4D. The lower electrode 4E is made of tungsten processed into a disk shape. As a result of conducting a discharge experiment using such an electrode, 1
The wear of the electrode after 1,000,000 discharges was less than 100 μm. Almost similar results were obtained using a sintered alloy of a high melting point metal with a similar structure.

[Effects of the Invention] As explained above, by using a high-melting point metal or an alloy of high-melting point metals in the electrode portion that comes into contact with the high-density plasma of the plasma X-ray source, 'electrode wear is extremely reduced; The lifespan of the plasma X-ray source electrodes has been significantly extended, and the damage to the
The life of the radiation source will be extended, and its reliability will be dramatically improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram of another embodiment of the present invention, Fig. 3 is a basic circuit block diagram of a plasma X-ray source, and Fig. 4 is a block diagram of a conventional plasma X-ray source.
It is a block diagram of the electrode part of a radiation source. 1...Capacitor, 2...Switch, 3...High-speed opening/closing gas valve, 4...Electrode, 48...Upper part, 4B...Lower electrode, 4G...Double pole A film coated with a high melting point metal, 4D... Upper electrode made of a high melting point metal, 4E... Lower electrode made of a high melting point metal, 5... Power transmission board, 6... Insulating plate, 7... Vacuum container, 8... X-ray extraction window, 100... Injected gas mass, lOl... pinched high-temperature/high-density plasma, 102
...X-ray, 103...6n field. 51 Diagram 1 Diagram 2

Claims (1)

[Claims] In an X-ray generator that generates X-rays from plasma generated by passing a large current between a pair of electrodes, at least a portion of the pair of electrodes exposed to the plasma is made of tungsten, tantalum, molybdenum, vanadium, niobium, etc. , rhenium, zirconium, or an alloy consisting of two or more of tungsten, tantalum, molybdenum, vanadium, niobium, rhenium, and zirconium.