JP2000091095A - X-ray generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LPX generating no breakdown and degradation of an X-ray optical element by particles dispersed from a target even in the case of generating the strong X-ray for a long time. SOLUTION: A target material 101 in a liquefied target reservoir 100 is injected from a nozzle 103 through a pipeline 102 and a feed through. The liquid column 122 of the target material injected from the nozzle 103 is irradiated with the laser beam so as to form plasma to generate X-ray. After the target material passes through a variable aperture 107 and a pipe 110, the target material is accumulated in a container 111. Thereafter, the target material is returned to the liquefied target material reservoir 100 for circulation through a container 113 after the pressure equalizing operation using each valve. The target material injected from the nozzle 103 can be continuously injected or intermittently injected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray generator suitable for use as an X-ray source used in X-ray equipment such as an X-ray microscope, an X-ray analyzer, and an X-ray exposure apparatus. More specifically, an X-ray generator (hereinafter, referred to as a laser plasma X-ray source, LPX) that irradiates a target material with laser light to convert the target material into plasma and generate X-rays from the plasma. ).

[0002]

2. Description of the Related Art Since LPX is small in spite of high brightness, it is attracting attention as a light source for a laboratory-sized X-ray apparatus (for example, an X-ray microscope or an X-ray analyzer). In recent years, it has also attracted attention as a light source for an X-ray reduction exposure apparatus.

However, in putting LPX to practical use, scattered particles emitted from plasma or a target material near the plasma pose a problem. The shape of the flying particles is ion,
They range from extremely small and light particles in the form of atoms and clusters to molten droplets ranging in diameter from several μm to several tens μm. Large and heavy scattered particles in the form of droplets damage the optical element when colliding with the X-ray optical element. In addition, small atomic scattered particles adhere to and accumulate on the X-ray optical element, and their performance (reflectance and transmittance) gradually decreases.

[0004] For atomic small and light flying particles,
By enclosing a buffer gas in a vacuum vessel and covering the periphery of the X-ray optical element with a cover, the amount of the X-ray optical element that adheres and deposits on the optical element can be significantly reduced (Japanese Patent Laid-Open No. 7-127600).
However, the collision of the scattered particles in the form of droplets having a large mass with the X-ray optical element could not be completely prevented by the conventional technology.
That is, such a droplet-like scattered particles are mechanically shut off by a shutter or the like, but since the velocity of the droplet-like scattered particles has a distribution due to its weight, etc., It cannot be completely removed.

Further, in order to remove such scattered particles having a large particle diameter, a disk-shaped target material having a diameter of about 10 cm is applied at a high speed (40,000 revolutions / minute.
At 0 m / sec), by irradiating a laser beam near the circumference, the direction of the scattered particles emitted from near the laser irradiation point is concentrated in the rotation direction by the inertia force of the disk. (LA Shmaenok et al., Pro
ceedings of the Conf.On Applications of Laser Pla
sma Radiation II, SPIE 2523, 12-14 July 1995).

However, this method has a problem in that the target must be replaced after irradiating a predetermined number of shots because the size of the disk is limited. In order to replace the target, it is necessary to break the vacuum state of the vacuum container, so that it is necessary to interrupt the operation of the apparatus using LPX, which significantly lowers the efficiency.

Further, a target material is ejected from a nozzle vibrated by a piezo element as a liquid material (for example, alcohol) at room temperature to form a row of fine droplets of about 10 μm, and a laser beam is applied to the droplets. Irradiation methods have also been used. This method can easily supply the target continuously, and because the size of the target material is small, all the droplets irradiated with the laser beam evaporate instantaneously, so there are few scattered particles with a large particle size. However, there are drawbacks in that the nozzle vibration mechanism is complicated, that it is difficult to synchronize the droplet with the laser beam, and that it is difficult to generate stable X-rays.

In order to solve the problem that it is difficult to synchronize a droplet and a laser beam, an attempt has been made to irradiate a laser beam to a liquid column portion from a nozzle outlet until a droplet is generated. (L. Malmqvist et al., Rev. Sci.
Instrum. 67, 4150 (1996)), the length of this liquid column is generally only a few mm from the nozzle outlet. For this reason, the distance between the plasma generation position and the tip of the nozzle becomes short, and ions or atoms of the target material released from the plasma collide with the nozzle, thereby shaving the tip of the nozzle. And
The shaved substance adheres to the X-ray optical element, causing deterioration of the element performance.

Attempts have been made to cool xenon (Xe), which is a gas at normal temperature, to solidify the gas into a pellet having a diameter of about 100 μm into a vacuum vessel and irradiate it with a laser beam. At this time, part of the pellet is rapidly heated and vaporized by the irradiation of the laser beam,
Most of them are shattered by shock waves due to the expansion of the plasma, and scatter around as small solid pieces. Since the vaporized xenon gas does not adhere to the optical element, it does not lead to deterioration of the element, but small particles on a solid collide with the optical element and may cause fatal damage.

Attempts have also been made to blow xenon (Xe), which is a gas at room temperature, from a nozzle and irradiate the nozzle with laser light. However, since the gas is used as the target material, the substance density is smaller than that of a solid or liquid, and the gas released into the vacuum diffuses rapidly to the surroundings. It decreases rapidly as the distance from the nozzle increases. For this reason, in order to increase the X-ray intensity, it is necessary to condense laser light near a nozzle having a high density. Then, the distance between the plasma generation position and the tip of the nozzle becomes short, resulting in the shaving of the nozzle as described above, which deteriorates the performance of the X-ray optical element.

[0011]

As described above,
In the prior art, an LPX that generates intense X-rays for a long period of time while preventing scattered particles of a target material and nozzles from colliding or adhering to an X-ray optical element is known.
Had not been put to practical use.

The present invention has been made in view of such circumstances, and it is possible to generate X-rays of high intensity for a long period of time, and even if X-rays are continuously generated for a long period of time. ,
An object of the present invention is to provide an LPX in which X-ray optical elements are not damaged or deteriorated due to particles scattered from a target.
Another object of the present invention is to provide an LPX that simplifies the configuration of a nozzle and facilitates synchronization between a target and laser light irradiation.

[0013]

A first means for solving the above-mentioned problem is to irradiate a target material placed in a container evacuated to vacuum with a laser beam, so that the target material is plasma-treated. An X-ray generation device for generating X-rays from the plasma, wherein the target material is in a liquid form and is continuously or intermittently discharged from a discharge port. Claim 1).

In the present means, since the target material is in a liquid state, the density of the target substance is higher than the gas and close to the solid density, so that high-density plasma can be generated and the X-ray intensity can be increased. Further, replenishment of the target material is facilitated, and LPX can be used stably and continuously for a long time. Furthermore, in this means, since the liquid target is ejected continuously or intermittently, the target and the laser irradiation can be easily synchronized with each other as compared with the conventional droplet target, and the target can be accurately irradiated. In addition, in this means, since the discharge port can be separated from the laser beam irradiation position, the discharge port and its peripheral members are shaved by ions and atoms emitted from the plasma, and these become scattered particles and become scattered particles on the optical element. Is less likely to adhere to and accumulate on the optical element to degrade the performance of the optical element. The target material may be liquid at room temperature, or may be liquid after heating and cooling.

Here, "intermittently" indicates intermittentness such that the liquid target is ejected only for a time corresponding to the laser irradiation time. In contrast, the conventional liquid train emits the liquid train at a much shorter interval than the laser irradiation interval, and does not mean that the means is "intermittently" emitted. As a method of intermittently discharging the target substance, for example, by opening and closing an electromagnetic valve,
There is a method of controlling ejection. In this case, the electromagnetic valve may be opened just before the laser irradiation, and closed after the laser irradiation.

When a substance having a high vapor pressure is used as the target material, if the target material is continuously discharged, the target material not irradiated with the laser, that is, the target material discharged wastefully, evaporates, and the target material in the vacuum vessel is evaporated. The pressure rises, which is not desirable. Therefore, in such a case, it is particularly important to discharge the target substance intermittently.

A second means for solving the above-mentioned problems is as follows:
An X-ray generator that irradiates a target material placed in a container that has been evacuated to vacuum with a laser beam to convert the target material into plasma and generate X-rays from the plasma. X is characterized in that the form is powdery, and the powdery target material is diffused in the solution, and the turbid liquid is continuously or intermittently discharged from the discharge port.
A line generator (claim 2).

This measure is suitable for a target material whose shape cannot be made into a tape shape. The simplest way to use the target material continuously is to tape the shape of the target substance. By irradiating a laser beam while winding the tape-shaped target material, X-rays can be continuously generated for a long time. Further, since the target material becomes thinner (for example, several μm to several tens μm) by being formed in a tape shape, most of the scattered particles penetrate in the direction of the target back surface, so that the target surface direction (laser There is also an advantage that the amount of scattered particles radiated in the (irradiation direction) can be reduced.

However, depending on the type of target material, it is difficult to form a tape. For example, boron nitride (BN), ceramics such as B ₄ C, SiC, ZrO ₂ , and SiO ₂ are such target materials. However, it is easy to powder such a material. Therefore, these materials are powdered, the powdery target member is diffused (mixed) into the solution, and the turbid liquid is continuously or intermittently discharged from the discharge port to irradiate the liquid column with laser light. In this case, the powdery target material can be turned into plasma, and X-rays from the target material can be used.

As the solution, any liquid-phase solution such as water, an organic liquid such as alcohol and oil, and an inorganic liquid such as ammonia can be appropriately selected and used. The size of the powdery target member may be smaller than the discharge port, and is preferably about several tens nm to several tens μm.

Since the solution is turned into plasma by irradiation with laser light, X-rays are also emitted from the solution substance. These X-rays can be easily removed by using a filter or a multilayer mirror. it can. For example, consider a case in which an organic diffusion pump oil (alkyl-based oil) is used as a solution, BN is used as a powdery target material, and Lyman α-rays (wavelength 4.8 nm) emitted from B ions are used. When the BN turbid liquid is irradiated with laser light, X-rays from ions such as C, O, and N are emitted from diffusion pump oil, which is a solution, and X-rays from B and N ions are emitted from BN. At this time, if a carbon thin film (for example, a thickness of 2 μm) is used as the X-ray filter, the carbon K
X-rays having a wavelength shorter than 4.5 nm, which is the absorption edge, are greatly attenuated, and only X-rays having a wavelength longer than the absorption edge are transmitted. C, O,
Since X-rays from ions such as N are all shorter than 4.5 nm, they are cut by a carbon filter,
Lyman α ray can be extracted. Also in this means, the meaning of "intermittent" is the same as in the first means.

A third means for solving the above-mentioned problem is:
The first means or the second means, wherein the ejection speed of the target material is at least 50 m / sec or more (Claim 3).

The emission speed of the scattered particles having a large particle diameter is 102 to 103 m / se depending on the laser irradiation conditions and the target material.
Since it is about c, if the ejection speed of the liquid target is set to 50 m / sec or more, the emission direction of the scattered particles changes to the downstream side of the liquid target. Therefore, the droplet-like scattered particles are reduced on the upstream side of the liquid target, and if the X-ray optical element is arranged at this position, damage to the optical element by these scattered particles can be reduced.

A fourth means for solving the above-mentioned problem is:
Any of the first to third means, wherein the liquid target or the turbid liquid is a dissolved liquid-phase metal (Claim 4).

In the present means, a liquid target or a turbid liquid which is solid at room temperature, such as zinc, lead or tin, and becomes liquid when heated is used. When heated to 419.58 ° C. or higher for zinc, 327.5 ° C. or higher for lead, and 231.97 ° C. or higher for tin, it can be made liquid. This allows these target materials to be used more than when they are used as solids (eg discs).
You can use it for a long time.

A fifth means for solving the above problem is as follows.
The fourth means is characterized in that the molten liquid phase metal is tin (Sn) or a material containing tin (Sn) (claim 5).

Since tin (Sn) has a spectrum peak near a wavelength of 13 nm, a substance containing tin is suitable as a target material of an X-ray source for soft X-ray reduction lithography using a wavelength of 13 nm. Further, tin has a relatively low melting point (231.97 ° C.) and can be easily made into a liquid state. Further, since the vapor pressure is low and the vapor pressure is low even under vacuum due to the low saturated vapor pressure, there is no adhesion or deposition on the optical element. For example, even at a temperature of around 560 ° C., which is in a liquid state, the saturated vapor pressure is about 10 ⁻¹¹ Torr, and the typical vacuum degree used for LPX (several Torr to
10 ^-6 Torr).

In this means, the molten liquid metal material may be an alloy or a compound containing tin.
For example, solder is an alloy of tin and lead, whose melting point is Sn
In the case of 60% and 40% of Pb, the temperature is 183 ° C, which is lower than that of pure tin, and it is easily liquid. Also, like tin, lead has a very low vapor pressure of 10 ⁻¹¹ Torr even at about 260 ° C., so that it does not adhere or deposit on the optical element.

A sixth means for solving the above-mentioned problem is:
Any of the first to third means, wherein the liquid target or the turbid liquid is a cooled liquefied gas (Claim 6).

For example, N ₂ , CO ₂ , Kr, Xe, etc. are gases at room temperature, but can be made liquid by cooling. It becomes liquid if between -209.86 ℃ ~-195.8 ℃ in the case of N _2, in the case of CO ₂ is -56.6 ℃ ~-78.5 ℃, K
-156.6 ° C to -153.4 ° C for r, -111.9 for Xe
If it is between ℃ and -108.1 ℃, it becomes liquid. The use of such a liquid target material does not cause debris, which is a problem when cooled into a solid pellet as described above, and does not damage the optical element.

A seventh means for solving the above-mentioned problem is as follows.
The sixth means is characterized in that the cooled liquefied gas is a rare gas or a gas containing a rare gas (claim 7).

Noble gases (Ne, Ar, Kr, Xe,
If Rn) or the like is used, the portion irradiated with the laser is vaporized and does not chemically react with the substance used in the optical element, so that it does not adhere to or accumulate on the optical element.

Eighth means for solving the above-mentioned problem is:
Any one of the first to seventh means, further comprising a circulating mechanism for circulating a liquid substance or a turbid liquid used as a target material. 8).

By circulating and using a turbid liquid containing a target material or a powdered target material, the target material or turbid liquid need not be supplied from the outside, so that it can be used continuously. Use efficiency can be greatly increased.
Especially when the target material or the turbid liquid is expensive, the running cost of the apparatus can be reduced. Circulation of the target material or the turbid liquid may be performed in the liquid phase, or may be circulated as a solid or gas in the middle. It is convenient to use a solid or gaseous substance at room temperature if the solid or gaseous substance is circulated on the way. For example, if the material is heated and liquid, such as tin, if it is to be circulated in the liquid state, it is necessary to maintain the piping system at a high temperature and to make all the circulating pumps etc. high temperature specifications. The structure becomes complicated and leads to an increase in cost. In such a case, if the material is returned to a solid and then transported, and then heated and melted before being used as a target, the circulation system is simplified, reliability is increased, and costs can be reduced. .

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a first embodiment of the present invention. In FIG. 1, 100 is a liquefied target reservoir, 101 is a target material, 102 is a pipe, 103 is a nozzle, 104 is an X stage, 105 is a Y stage, 1
06 is a Z stage, 107 is a variable aperture, 108
Is the X stage, 109 is the Y stage, 110 is the pipe,
111 is a container, 112 is a valve, 113 is a container, 11
4, 115, 116 are valves, 117 is a lens, 118
Is a window, 119 is a vacuum vessel, 120 is a laser beam, 121
Is a leak valve, and 122 is a liquid column of the target material.

A liquid target material 101 is contained in the liquefied target reservoir 100. Here, water (H ₂ O) is used as the target material. Liquefaction target reservoir 100
Is connected to a pressurizing device (in this case, a high-pressure air cylinder), and the target material 101 is compressed at a pressure of several to 100 atm. As a result, the target material 101 passes through the pipe 102, passes through the feed-through, and is ejected from the nozzle 103. The liquid column 122 of the target material ejected from the nozzle 103 is irradiated with a laser beam to generate plasma to generate X-rays.

The feedthrough is attached to the X stage 104, the Y stage 105, and the Z stage 106, and adjusts the position of the nozzle 103 so that plasma can be generated at a predetermined position. After the target material has passed through the variable aperture 107 and the pipe 110, the container 11
1 is stored. The inside of the container 111 is evacuated by a vacuum exhaust device (not shown) to about the saturated vapor pressure of the target material. The variable aperture 107 is attached to the X stage 108 and the Y stage 109.

First, the opening of the variable aperture 107 is opened to the maximum, and after the position of the nozzle 103 is determined, the target material passes through the center of the variable aperture by the X stage 108 and the Y stage 109, and the variable aperture 107 is opened. Is gradually reduced until the diameter of the opening becomes slightly larger than the diameter of the liquid column 122 of the target material. By doing so, differential evacuation between the vacuum vessel 119 and the vessel 111 can be performed.

When a predetermined amount of the target material is accumulated in the container 111, the valve 115 is gradually opened, and the container 11
3 is evacuated. At this time, the valves 112, 114, 1
16 is closed. When the pressure in the container 113 is
When it becomes the same as 1, the valve 112 is opened and the container 111 is opened.
The target material accumulated inside is flowed into the container 113. Thereafter, the valves 112 and 115 are closed, the valve 116 is gradually opened, and when the pressure in the container 113 and the liquefaction target reservoir 100 become the same, the valve 114 is opened and the container 113 is opened.
The target material therein flows into the liquefied target reservoir 100. When all the target material has been moved, the valves 116, 11
After closing the leak valve 121 and opening the leak valve 121 to reduce the pressure in the container 113 to the atmospheric pressure, the leak valve 121 is closed. As described above, the target material can be continuously circulated without interrupting the supply of the target material to the laser beam irradiation position.

Since the water used as the target material has a relatively high saturated vapor pressure, X-rays generated from the plasma may be absorbed and attenuated by the vapor in the vacuum vessel. Therefore, the target material is cooled so that the saturated vapor pressure is as low as possible. Liquefaction target pool 10
The piping 102, the nozzle 103, and the container 111 are cooled to about 1 ° C. by a cooling device. The saturated vapor pressure of 1 ° C. water is about 5 Torr. By cooling the target material, the pressure in the vessel 111 can be reduced to about 5 Torr, and the pressure in the vacuum vessel 119 can be reduced to 5 Torr, or to a lower pressure if differential evacuation with the vessel 111 is possible. it can.

When it is desired to further reduce the pressure in the vacuum vessel 119, the liquid column 122 of the target material may be covered with a member provided with openings for laser beam incidence, laser beam emission, and X-ray extraction. The opening for emitting laser light is provided to prevent laser light that did not hit the target material at the time of nozzle position adjustment from hitting the member, and may be omitted if unnecessary.

FIGS. 2A and 2B show an example of a state near the nozzle of this embodiment. In FIG. 2, reference numeral 123 denotes a transmitted laser beam, reference numerals 124a and 124b denote members, reference numeral 125 denotes a laser light entrance opening, reference numeral 126 denotes an X-ray extraction opening, reference numeral 127 denotes a laser emission opening, and other reference numerals denote the same components as those in FIG. .

A member 1 provided with a laser light entrance opening 125, an X-ray extraction opening 126, and a laser emission opening 127
24a covers the periphery of the liquid column 122. Nozzle 103
And the member 124a are in close contact with each other, there is a very small gap between the member 124a and the variable aperture 107, and the position of the variable aperture is set to the X, Y stage 108,
109 (FIG. 1). By doing so, the amount of evaporation from the liquid column 122 into the vacuum vessel 119 can be reduced, so that the pressure inside the vacuum vessel 119 can be reduced. If necessary, member 12
The inside of 4a may be exhausted by an exhaust device.

In the example shown in FIG.
As in (a), the periphery of the liquid column 122 is covered with a member 124b, and the inside of the member 124b can be evacuated (an exhaust device is not shown).

In these embodiments, when the diameter of the opening of the nozzle 103 is 200 μm and the back pressure is 35 atm, the flow rate of the target material is about 64 m / sec. Also, the nozzle opening diameter is 100μ
m, when the back pressure is 100 atm, the target material flow rate is about 150
m / sec. In this way, the flow velocity of the target substance is 50 m / s
Since ec exceeds ec, as described above, the flying direction of the scattered particles having a large particle diameter can be changed to the downstream side by the inertial force.

In the above-described embodiment, the liquid is recovered and circulated in a liquid state. However, as described in the following embodiments, the liquid may be recovered and circulated once in a solid or gaseous state. Good. Although water is used as the target substance in the above embodiment, the present invention is not limited to this. Water is a liquid at room temperature, but may be a substance that becomes liquid when heated or cooled, such as tin or krypton. In the case of a substance that becomes a liquid by heating, the container, the piping nozzle, the container, and the container may be heated to a temperature at which they are liquefied. In the case of a substance which is cooled and liquefied, the container, the piping nozzle, the container, and the container may be cooled to a temperature at which they are liquefied.

In this embodiment, water having a relatively high vapor pressure is used as the target material. However, if a substance having a low vapor pressure at room temperature is used, the differential pumping system is not used as described above. Therefore, the configuration of the apparatus becomes simpler. Such materials include oil for diffusion pumps and oil for rotary pumps.

FIG. 3 schematically shows a second embodiment of the present invention. In FIG. 3, reference numeral 300 denotes a liquefaction target pool,
Is a target material, 302 is a pipe, 303 is a nozzle, 304 is an X stage, 305 is a Y stage, 306 is a Z stage, 307 is a pipe, 308 is a motor, 309 is a propeller, 310 is a spiral fin, 311 is a container, 312 Is a valve, 313 is a container, 314, 315, 316 is a valve, 317 is a lens, 318 is a window, 319 is a vacuum container,
320 is a laser beam, 321 is a leak valve, and 322 is a liquid column of the target material.

In the present embodiment, Sn is used as the target material. In the first embodiment, even a substance that becomes a liquid by heating or cooling is circulated in a liquid state. However, in the present embodiment, the substance is circulated after being solidified once. By doing so, the portion to be heated or cooled is reduced, so that the device configuration is simplified. In the present embodiment, since the device configuration is almost the same as that of the first embodiment shown in FIG. 1, only different points will be described in detail.

The target material 30 is stored in the liquefied target pool 300.
The Sn which is 1 is put, and the liquefaction target pool 300
It is heated to a temperature at which Sn liquefies (for example, 300
° C). The pipe 302 and the nozzle 303 are also heated to a temperature at which Sn liquefies. The liquefied Sn is pressurized by the compressed nitrogen, and is ejected as a liquid from the nozzle 303 through the pipe 302. The laser beam 320 is applied to the Sn liquid column 322 ejected into the vacuum vessel 319, and X-rays are emitted.

The liquid Sn passes through the pipe 307 and the container 311
However, when the propeller 309 is rotated by the motor 308, it scatters and collides with the inner wall of the container 311 or the spiral fin 310 attached to the container 311. The temperature of the container 311 and the fin 310 is sufficiently lower than the melting point of Sn (for example, 10
° C), the inner wall of the container 311 and the fin 3
The Sn droplets that collided with 10 are immediately cooled and become solid particles. The solid particles fall while rolling on the fins 310 and collect at the bottom of the container 311. When a predetermined amount of Sn particles have accumulated, the valve 315 is opened and the inside of the container 313 is evacuated so that the pressure becomes substantially the same as that of the vacuum container 319. Thereafter, the valve 312 is opened and the container 31 is opened.
The particles of Sn accumulated in 1 are dropped into the container 313.

Thereafter, the valves 312 and 315 are closed, the valve 316 is gradually opened to make the pressure in the container 313 and the liquefaction target reservoir 300 the same, and then the valve 314 is opened.
The Sn particles are dropped from the container 313 to the liquefied target reservoir 300. When all the Sn has moved, the valve 314,
316 is closed, the leak valve 321 is opened, and the container 313 is opened.
After the internal pressure is reduced to atmospheric pressure, the leak valve 321
Close. The Sn particles that have fallen into the liquefied target pool 300 are heated to be in a liquid state, and are ejected from the nozzle 303 again.

As described above, liquid Sn of about 300 ° C. has a low saturated vapor pressure, and since solid Sn is stored in the container 311, the vapor pressure is further lower than that of liquid Sn. . For this reason, as in the first embodiment, the vacuum container 31
Since there is no need to insert an aperture between 9 and the container 311 to perform differential evacuation, the configuration of the apparatus becomes simpler.

FIG. 4 shows an outline of a third embodiment of the present invention. In FIG. 4, reference numeral 400 denotes a liquefied target pool,
Is the target material, 403 is the nozzle, 404 is the X stage, 4
05 is a Y stage, 406 is a Z stage, 407 is a pipe, 408 is a motor, 409 is a propeller, 410 is a spiral fin, 411 is a container, 412 is a valve, 413 is a container, 414 and 415 are valves, and 416 is a leak valve. ,
417 is a belt conveyor, 418 is a tray, 419, 4
20, 421 are valves, 422 is a leak valve, 423
Denotes a lens, 424 denotes a window, 425 denotes a laser beam, 426 denotes a liquid column of a target material, 427 denotes a vacuum container, and 428 denotes a container.

In the second embodiment shown in FIG. 3, the solidified target material is dropped and moved to the liquefied target material pool 300, but in this embodiment, the liquefied target pool 400 is moved by the belt conveyor 417. Transported to By doing so, the liquefied target reservoir 30
Since 0 can be arranged near the nozzle 403, it is not necessary to heat a long pipe from the liquefaction target reservoir to the nozzle as in the second embodiment.

In this embodiment, Sn is used as a target material, as in the second embodiment. The Sn is heated to about 300 ° C. and stored in the liquefied target reservoir 400 in a liquefied state. The liquefied Sn 401 is pressurized by compressed nitrogen, and the nozzle 403 is also heated to about 300 ° C.
It is jetted out as more liquid. The laser beam 425 is applied to the Sn liquid column 426 ejected into the vacuum vessel 427, and X-rays are emitted. The liquid Sn passes through the pipe 407 and the container 41
1 and solidified in the same manner as in the second embodiment, and accumulated in the container 411 as Sn particles.

When a predetermined amount of Sn particles is accumulated, the valve 414 is opened and the inside of the container 413 is evacuated to the same pressure as the inside of the vacuum container 427, and then the valve 412 is opened to drop the Sn particles into the container 413. Let it.

Thereafter, the valves 412 and 414 are closed, the leak valve 416 is opened to return the inside of the container 413 to the atmospheric pressure, and then the valve 415 is opened to transfer the Sn particles in the container 413 to the belt conveyor 417. The Sn particles are transferred to a tray 418 by a belt conveyor 417. Saucer 4
When some amount has accumulated in 18, the valve 419 is opened and the Sn particles are poured into the container 428. (At this time, the container 428
Inside is at atmospheric pressure. Thereafter, the valve 419 is closed, and the valve 421 is gradually opened so that the pressure in the container 428 and the pressure in the liquefaction target reservoir 400 become equal. Then, the valve 420 is opened to drop the Sn particles into the liquefied target reservoir 400 to be liquefied and used again as the target material.

In this way, the liquefied target reservoir 400 can be placed near the vacuum container 427, and the length of the pipe from the liquefied target reservoir 400 to the feedthrough of the vacuum container 427 can be shortened. For this reason, members that need to be heated can be grouped close together,
The configuration of the device becomes easy.

In the present embodiment, the solidified target material is transported by the belt conveyor 417 placed in the atmosphere, but this transport may be performed in a vacuum. Second, third
In the embodiment of the present invention, Sn was used as the target material.However, the present invention is not limited to this, and may be any substance, a single element such as Sn or Zn, or an alloy such as solder. It may be a compound. In the second and third embodiments, a target substance that becomes liquid by heating is used, but a substance that becomes liquid by cooling may be used.

FIG. 5 shows an outline of a fourth embodiment of the present invention. In FIG. 5, reference numeral 500 denotes a liquefaction target pool;
Is a target material, 502 is a pipe, 503 is a nozzle, 504 is an X stage, 505 is a Y stage, 506 is a Z stage, 507 is a pipe, 508 is a motor, 509 is a propeller, 510 is a spiral fin, 511 is a container, 512 Is a valve, 513 is a container, 514, 515, 516 is a valve, 517 is a lens, 518 is a window, 519 is a vacuum container,
520 is a laser beam, 521 is a leak valve, and 522 is a liquid column of the target material.

In the present embodiment, Kr (krypton) is used as the target material. Kr in liquefaction target pool 500
Has been introduced. The liquefied target reservoir 500 is controlled by a cooling device (not shown) so that Kr is liquefied at -156.6 ° C. to -153.4 ° C., and Kr is in a liquid state and the liquefied target reservoir 50 is in a liquid state.
Stored in 0. The pipe 502 and the nozzle 503 are similarly cooled to a temperature at which Kr is liquefied. Liquefied
Kr is pressurized by compressed nitrogen, and is jetted out of the nozzle 503 as a liquid through the pipe 502. The laser beam 520 is applied to the Kr liquid column 522 ejected into the vacuum vessel 519, and X-rays are emitted.

The liquid Kr passes through the pipe 507 and the container 511
However, when the propeller 509 is rotated by the motor 508, the propeller 509 scatters and collides with the inner wall of the container 511 or the spiral fin 510 attached to the container. Since the container 511 and the fins 510 are cooled to a temperature sufficiently lower than the melting point of Kr (for example, −209 ° C.) by liquid nitrogen or the like, the droplets of Kr colliding with the inner wall of the container 511 and the fins 510 are immediately cooled, and Particles.

The solid particles fall while rolling on the fins, and collect at the bottom of the container 511. When a predetermined amount of Kr particles has accumulated, the valve 515 is opened and the container 51 is opened.
3 is evacuated so that the pressure becomes substantially the same as that of the vacuum vessel 519. After that, the valve 512 is opened, and the Kr particles stored in the container 511 are dropped into the container 513. The container 513 is also cooled to a temperature sufficiently lower than the melting point of Kr (for example, −209 ° C.) by liquid nitrogen or the like, similarly to the container 511.

Then, the valves 512 and 515 are closed, the valve 516 is gradually opened to make the pressure in the container 513 and the liquefaction target reservoir 500 equal, and then the valve 514 is opened.
The Kr particles are dropped from the container 513 to the liquefied target reservoir 500. When all the Kr has been moved, the valve 514,
516 is closed, the leak valve 521 is opened, and the container 513 is opened.
After the internal pressure is reduced to about atmospheric pressure, the leak valve 521 is closed. Kr dropped into liquefied target pool 500
The particles become liquid and are ejected from the nozzle 503 again.

If the Kr particles stored in the container 511 or 513 adhere to each other and form a large lump, the Kr particles are formed into particles or agglomerates by a certain stirring or pulverizing mechanism, and then the next step. May be moved to the container. In the fourth embodiment, a liquefied target pool 500 is formed in a state where the collected target material (Kr) is solidified.
Although it is circulated, it may be circulated in a gaseous state.

FIG. 6 shows an outline of a fifth embodiment of the present invention. In FIG. 6, reference numeral 600 denotes a liquefaction target pool,
1 is a target material, 602 is a pipe, 603 is a nozzle, 604
Is an X stage, 605 is a Y stage, 606 is a Z stage, 607 is a pipe, 608 is a motor, 609 is a propeller, 610 is a spiral fin, 611 is a container, 612 is a valve, 613 is a container, 613 and 615 are valves, 616
Is a vacuum vessel, 617 is a laser beam, 618 is a lens, 6
19 is a window, and 622 is a liquid column of the target material.

Also in this embodiment, the target material
Kr (krypton) is used. Liquefaction target pool 600
Has introduced Kr. The liquefied target pool 600 is liquefied by Kr by a cooling device (not shown).
Kr is stored in the liquefied target reservoir in a liquid state. The nozzle 603 is also cooled to a temperature at which Kr is liquefied. The liquefied Kr is pressurized by the compressed nitrogen, and is ejected from the nozzle 603 as a liquid. The laser beam 617 is applied to the Kr liquid column 622 ejected into the vacuum vessel 616, and X-rays are emitted. Liquid Kr
Enters the container 611 through the pipe 607, but scatters by hitting the propeller 609 rotating by the motor 608, and collides with the spiral fin 610 attached to the inner wall of the container 611 or the container.

Since the container 611 and the fins 610 are cooled to a temperature sufficiently lower than the melting point of Kr (for example, -209 ° C.) by liquid nitrogen or the like, the Kr droplet colliding with the inner wall of the container 611 or the fin 610 is immediately cooled. And become solid particles. The solid particles fall while rolling on the fins and collect at the bottom of the container.

When a predetermined amount of Kr particles accumulate,
The valve 614 is opened to evacuate the inside of the container 613 so that the pressure becomes almost the same as that of the vacuum container 616. After that, the valve 612 is opened, and the Kr particles accumulated in the container 611 are dropped into the container 613. And a valve 612,
After closing 614, the container 613 is heated to vaporize the solid Kr particles stored in the container 613.

The pressure of the gasified Kr is changed to the liquefaction target pool 6.
When the pressure of the nitrogen gas pressurizing inside 00 becomes higher, the valve 615 is gradually opened to allow the vaporized Kr to flow into the liquefied target reservoir 600. The inflowing Kr gas is cooled again to become a liquid, and is ejected from the nozzle.

If the pressure of the pressurized nitrogen gas is very high (for example, about several tens to 100 atm) and the vaporized Kr
When it is difficult to make the pressure higher than the pressure of the nitrogen gas, a container for liquefying or solidifying the vaporized Kr is prepared, and once it is liquid or solid, it may be introduced into the liquefaction target reservoir 600. .

If the Kr particles stored in the container 611 (or the container for solidifying the vaporized Kr gas, if necessary) adhere to each other and form a large lump, some kind of stirring and pulverizing mechanism is used. After the particles are formed into particles or agglomerates, they may be moved to the next-stage container.

In this embodiment, liquefied Kr is pressurized by compressed nitrogen and jetted from the nozzle. However, liquefied Kr may be jetted by pressurized liquefied Kr using vaporized Kr.
In this way, by circulating in a vaporized state, the distance between the liquefied target reservoir and the nozzle can be reduced. For this reason, the members that control the liquefaction temperature are only the liquefaction target reservoir, the nozzle, and the short piping therebetween, and there is no need to control the long piping connecting the liquefaction target reservoir and the nozzle to the liquefaction temperature as in the fourth embodiment. Therefore, the device configuration is simplified.

In the fourth and fifth embodiments, Kr is used as the target material. However, the material is not limited to Kr, and any substance that is a gas at room temperature and becomes a liquid upon cooling, such as Xe or C
Any material such as O ₂ and N ₂ may be used.

In the above-described embodiment, the target material in the liquid phase is used. However, the target material in the form of a powder may be mixed in a solution and ejected from the nozzle as a turbid liquid. In this case, the solution may be liquid at normal temperature, or may be in a liquid phase by heating or cooling. Examples of the powdery target material include ceramics such as BN, B ₄ C, SiC, and ZrO ₂ , SiO ₂ , or Fe, Cu, Al, S
Metal particles such as n and organic fine particles such as latex may be used.

In each of the embodiments described above, the condensing diameter of the laser beam at the position of the target material is arbitrary. However, when the diameter of the liquid column portion of the target material is substantially equal to or larger than that, the diameter of the target material is reduced. Since ablation occurs in the same radial direction of the liquid column, scattered particles having a large particle diameter are not released in the direction perpendicular to the flow, which is preferable. Further, in each of the above embodiments, the target material is continuously ejected from the nozzle, but may be ejected intermittently. This occurs when the repetition frequency of the laser emission is low (for example,
10Hz or less). Further, in each of the above embodiments, the high-pressure gas is used as the pressurizing device for the target material, but the pressurizing device may be arbitrary, and may be pressurized by a compressor or a pump (for example, a gear pump).

[0078]

As described above, in the first aspect of the present invention, the target material is in a liquid form and is discharged continuously or intermittently from the discharge port. Since the density is higher than the gas and close to the solid density, high-density plasma can be generated, and the X-ray intensity can be increased. Further, replenishment of the target material is facilitated, and LPX can be used stably and continuously for a long time. further,
Since the liquid target is ejected continuously or intermittently, it is easy to synchronize the laser irradiation with the target, and the target can be accurately irradiated. In addition, since the discharge port and the laser beam irradiation position can be separated, the discharge port and its surrounding members are shaved by ions and atoms released from the plasma,
These are less likely to become scattered particles and to adhere and accumulate on the optical element to deteriorate the performance of the optical element.

According to the second aspect of the present invention, a substance which cannot be processed into a tape form is mixed into a solution in the form of a powder, and the turbid liquid is irradiated with a laser beam to continuously perform X-ray irradiation for a long time. Can be generated.

According to the third aspect of the present invention, since the ejection speed of the target material or the turbid liquid is at least 50 m / sec or more, the droplet-like scattered particles are reduced on the upstream side of the liquid target. Therefore, if the X-ray optical element is arranged at this position, damage to the optical element due to these scattered particles can be reduced.

According to the fourth aspect of the present invention, the use of the dissolved liquid-phase metal as the target member allows the X-ray to be continuously generated for a longer time than when these are used as a solid. Can be.

In the invention according to claim 5, since the molten metal material in the liquid phase is tin (Sn) or a material containing tin (Sn), it is used for soft X-ray reduction lithography using a wavelength of 13 nm. Suitable for target material of X-ray source. Further, tin has a relatively low melting point and can be easily made into a liquid state. Further, since tin has a low saturated vapor pressure, it does not easily evaporate even in a vacuum, so that it does not adhere or deposit on the optical element.

In the invention according to claim 6, since the liquid target or the turbid liquid is a cooled liquefied gas, debris which is a problem when cooled to form solid pellets does not occur, and the optical element is formed on the optical element. Do not damage.

According to the seventh aspect of the present invention, since the cooled liquefied gas is a rare gas or a gas containing a rare gas, the laser-irradiated portion is vaporized, and the material used for the optical element is chemically changed. no response. Therefore, there is no adhesion or deposition on the optical element.

In the invention according to claim 8, since a circulation mechanism for circulating and using a liquid phase substance or a turbid liquid used as a target material is provided, there is no need to supply the target material from the outside. Can be used continuously,
The use efficiency of the device can be greatly increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a first embodiment of the present invention.

FIG. 2 is a diagram showing a structure near a nozzle of the embodiment shown in FIG. 1;

FIG. 3 is a diagram showing an outline of a second embodiment of the present invention.

FIG. 4 is a diagram schematically illustrating a third embodiment of the present invention.

FIG. 5 is a diagram schematically showing a fourth embodiment of the present invention.

FIG. 6 is a diagram schematically showing a fifth embodiment of the present invention.

[Explanation of symbols]

100: Liquefied target reservoir, 101: Target material, 102:
Piping, 103 nozzle, 104 X stage, 105
Y stage, 106 ... Z stage, 107 ... variable aperture, 108 ... X stage, 109 ... Y stage, 1
10: pipe, 111: container, 112: valve, 113
... containers, 114, 115, 116 valves, 117 lenses, 118 windows, 119 vacuum vessels, 120 laser beams, 121 leak valves, 122 liquid columns of target material, 123 transmitted laser beams, 124a, Reference numeral 124b: member, 125: laser light entrance opening, 126: X-ray extraction opening, 127: laser emission opening, 300: liquefied target reservoir, 301: target material, 302: pipe, 303: nozzle, 304: X stage, 305: Y stage, 30
6 ... Z stage, 307 ... pipe, 308 ... motor, 3
09 ... propeller, 310 ... spiral fin, 311 ... container, 312 ... valve, 313 ... container, 314, 315,
316: bulb, 317: lens, 318: window, 319
… Vacuum container, 320 laser light, 321 leak valve, 322 liquid column of target material, 400 liquefied target reservoir, 401 target material, 403 nozzle, 404 X stage, 405 Y stage, 406 Z Stage 4,
07 ... pipe, 408 ... motor, 409 ... propeller, 4
10: spiral fin, 411: container, 412: valve,
413: container, 414, 415 ... valve, 416 ... leak valve, 417 ... belt conveyor, 418 ... tray,
419, 420, 421: valve, 422: leak valve, 423: lens, 424: window, 425: laser beam, 426: liquid column of target material, 427: vacuum container, 42
8: Container, 500: Liquefied target reservoir, 501: Target material, 502: Piping, 503: Nozzle, 504: X stage, 505: Y stage, 506: Z stage, 507
... pipe, 508 ... motor, 509 ... propeller, 510
... spiral fins, 511 ... containers, 512 ... valves, 51
3 ... container, 514, 515, 516 ... valve, 517 ...
Lens, 518: Window, 519: Vacuum container, 520: Laser light, 521: Leak valve, 522: Liquid column of target material, 600: Liquefied target reservoir, 601: Target material, 60
2. Piping, 603 nozzle, 604 X stage, 60
5 Y stage, 606 Z stage, 607 pipe, 608 motor, 609 propeller, 610 helical fin, 611 container, 612 valve, 613 container, 614, 615 valve, 616 vacuum container , 61
7 laser light, 618 lens, 619 window, 622
… The liquid column of the target material

Claims (8)

[Claims] 1. An X-ray generator that irradiates a target material placed in a vacuum-evacuated container with a laser beam to convert the target material into plasma and generate X-rays from the plasma. An X-ray generator, wherein the target material is in a liquid form and is discharged continuously or intermittently from a discharge port. 2. An X-ray generating apparatus that irradiates a target material placed in a container evacuated to vacuum with a laser beam to convert the target material into plasma and generate X-rays from the plasma. An X-ray generator, wherein the target material is in the form of a powder, the powdered target material is diffused in a solution, and the turbid liquid is continuously or intermittently discharged from a discharge port. . 3. The X-ray generator according to claim 1, wherein the jet speed of the target material or the turbid liquid is at least 50 m / sec or more. . 4. One of claims 1 to 3
Item 8. The X-ray generator according to Item 1, wherein the liquid target or the turbid liquid is a dissolved liquid-phase metal. 5. The X-ray generator according to claim 4, wherein the molten metal in the liquid phase is tin (Sn) or a material containing tin (Sn). Generator. 6. One of claims 1 to 3
Item 8. The X-ray generator according to Item 1, wherein the liquid target or the turbid liquid is a cooled liquefied gas. 7. The X-ray generator according to claim 6, wherein the cooled liquefied gas is a rare gas or a gas containing a rare gas. 8. One of claims 1 to 7
13. The X-ray generator according to item 12, further comprising a circulation mechanism for circulating and using the liquid phase substance or the turbid liquid used as the target material.