WO2004032211A1

WO2004032211A1 - X-ray generator and exposure device

Info

Publication number: WO2004032211A1
Application number: PCT/JP2003/010537
Authority: WO
Inventors: Hiroyuki Kondo
Original assignee: Nikon Corporation
Priority date: 2002-10-01
Filing date: 2003-08-20
Publication date: 2004-04-15
Also published as: JP2004128105A; AU2003262256A1

Abstract

An X-ray generator (1) has a spherical vacuum vessel (2). A mirror (first mirror) (10) is incorporated into an upstream-side opening (2a) in the vacuum vessel (2). This mirror (10) constitutes part of the upstream-side wall of the vacuum vessel (2). The reflecting surface (10a) of the mirror (10) is positioned in the vacuum vessel (2), with the back (10b) of the mirror (10) exposed to the atmosphere outside the vacuum vessel (2). The back (10b) of the mirror (10) has a water-cooled jacket (15) attached thereto. Since the water-cooled jacket (15) is disposed on the atmosphere-side of the mirror back (10b), the laying, etc. of a piping (15a) are easy and the arrangement is simple. Further, since the water-cooled jacket (15) is exposed to the atmosphere, replacement and maintenance are easy.

Description

Specification

X-ray generator and exposure equipment

The present invention relates to an X-ray generator provided in an X-ray apparatus such as an X-ray microscope, an X-ray analyzer, an X-ray exposure apparatus, and an exposure apparatus including the same. In particular, the present invention relates to an X-ray generator and the like having advantages such as easy replacement of a mirror. Background art

In recent years, laser-plasma X-ray sources and discharge plasma X-ray sources have attracted attention as light sources for X-ray equipment such as X-ray analyzers and X-ray exposure apparatuses.

A laser-plasma X-ray source (hereinafter referred to as LPX) focuses and irradiates a laser beam for excitation onto a target material in a vacuum vessel to generate plasma, and radiates X-rays from this plasma. is there. This LPX has a brightness comparable to that of an angel (synchrotron radiation), despite its small size. The discharge plasma X-ray source generates a discharge by applying a high pulse voltage to the electrodes, ionizes the working gas by this discharge, generates plasma, and uses X-rays radiated from the plasma. This discharge plasma X-ray source is characterized by its small size, large amount of radiated X-rays, low cost, and high conversion efficiency of X-rays to input power compared to LPX. A typical discharge plasma X-ray source is a dense plasma focus X-ray source (hereinafter referred to as DPFX). In such LPX and DPFX, the target material and members (electrodes, etc.) near the plasma scatter as atoms or ions during plasma generation (such particles are called scattered particles or debris). ). The scattered particles easily adhere to and accumulate on an X-ray mirror such as a multilayer mirror disposed around the plasma, and reduce the reflectivity of the mirror. For this reason, in LPX and DPFX, it is necessary to replace the multilayer mirror with a new mirror every certain period. In the X-ray generator equipped with the above-mentioned X-ray source, the mirror (the first mirror), to which the X-ray radiated from the plasma first enters, is attached inside the plasma generation chamber (vacuum container). I have. Therefore, there are the following problems.

(1) When replacing the first mirror, the first mirror must be removed and reattached inside the chamber, and it takes time and effort to replace the mirror.

(2) The plasma generation chamber becomes large due to the configuration including the first mirror. In addition, the temperature of the mirror rises due to the thermal load from the plasma X-ray source, so it is necessary to cool the mirror appropriately, but the cooling mechanism for that also becomes complicated. The present invention has been made in view of such a problem, and has as its object to provide an X-ray generator having advantages such as easy replacement of a mirror and an exposure apparatus having the same. Disclosure of the invention

In order to solve the above-mentioned problems, an X-ray generator according to the present invention comprises: an X-ray source that converts a target material into plasma and radiates X-rays from the plasma; a vacuum container that houses the X-ray source; And a mirror on which X-rays radiated from a radiation source are incident, wherein the mirror or a member holding the mirror constitutes a part of a wall of the vacuum vessel. .

According to the present invention, since the mirror or the member holding the mirror constitutes a part of the wall of the vacuum vessel, the deteriorated mirror can be quickly replaced with a new mirror from the atmosphere side.

In the X-ray generator of the present invention, the back surface of the member holding the mirror or the mirror may be exposed outside the vacuum vessel. In this case, since the mirror or the mirror holding member can be cooled from outside the vacuum vessel, it is easy to arrange the cooling means. Especially when the outside of the vacuum vessel is in the air, the heat of the mirror is radiated to the atmosphere from the back side, so that the temperature rise of the mirror can be suppressed. In the X-ray generator of the present invention, a mirror cooling mechanism can be provided on the back surface of the mirror or the member holding the mirror.

In this case, the temperature rise of the mirror can be suppressed by using the mirror cooling mechanism. Furthermore, since the mirror cooling mechanism can be provided on the atmosphere side (the back side of the mirror), the configuration of the cooling mechanism is simplified (for example, when the cooling mechanism is a water-cooled jacket, the piping is easily routed). Maintenance is also easier if the cooling mechanism is exposed to the atmosphere.

The X-ray generator according to the present invention further includes a laser light source for generating laser light for converting the target material into plasma, and the laser light is used for the mirror or a member holding the mirror. A part of the light may be transmitted, or the light may enter the vacuum container through an opening formed in the mirror.

In the case of a solid target, the X-rays radiated from the plasma have a strong intensity in the direction of the laser beam. Therefore, according to this means, the X-rays generated by the X-ray source can be effectively guided to the mirror, and the amount of X-rays emitted from the X-ray generator can be increased.

In the X-ray generator according to the present invention, detecting means for detecting the position and attitude of the mirror, adjusting means for adjusting the position and attitude of the mirror, and receiving a signal from the detecting means, And control means for controlling the adjusting means so as to take a predetermined position and posture.

In this case, the mirror can be accurately set to the correct position and posture. Therefore, it is possible to maintain the accuracy of the apparatus without changing the alignment of the apparatus when replacing the mirror or performing maintenance.

An exposure apparatus according to the present invention includes an X-ray generator according to any one of claims 1 to 4, an illumination optical system configured to irradiate an X-ray generated by the X-ray generator on a mask, and an X-ray reflected from the mask. And a projection optical system for projecting and imaging light on the sensitive substrate. According to the present invention, a mirror whose performance has deteriorated can be quickly and easily replaced with a new mirror, and the X-ray generator can be quickly returned to a normal state, so that the time and cost required for maintenance can be reduced and the apparatus can be operated. The rate can be improved. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram schematically showing an exposure apparatus having an X-ray generator according to one embodiment of the present invention.

FIG. 2 is a diagram showing a mirror position / posture adjustment unit in the X-ray generator of FIG.

FIG. 3 is a plan view showing another example of the mirror position / posture adjustment unit.

FIG. 4 is a diagram showing another example of the X-ray generator.

FIG. 5 (A) is a diagram showing another example of the X-ray generator, and FIG. 5 (B) is a front view of a mirror of the X-ray generator of FIG. 5 (A). BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, description will be made with reference to the drawings.

In the following description, the left side of FIG. 1 is referred to as the upstream side, and the right side of FIG. 1 is referred to as the downstream side (the optical system side at the subsequent stage) along the optical paths of the laser beam and the X-ray.

In this embodiment, an example in which the X-ray generator according to the present invention is applied to a laser plasma X-ray source will be described.

An X-ray generator 1 is arranged upstream of the exposure apparatus in FIG. The X-ray generator 1 includes a spherical vacuum vessel 2. The vacuum container 2 is provided with a vacuum pump (vacuum exhaust device) 3. Vacuum container 2 Pump 3 exhausts. When the pressure in the vacuum vessel 2 is reduced by the vacuum pump 3, the X-rays radiated from the plasma P are not attenuated.

Inside the vacuum vessel 2, a stainless steel gas jet nozzle 4 is arranged. The gas jet nozzle 4 is connected to a valve (both not shown) connected to a gas cylinder. The gas cylinder is filled with an evening get gas such as xenon (Xe). The target gas in the gas cylinder is sent to a valve via a pipe or the like, and is ejected from the gas jet nozzle 4 into the vacuum vessel 2. The ejected evening gas serves as a target material when generating plasma P.

An opening 2 a is formed on the upstream side of the vacuum vessel 2. A mirror (first mirror) 10 is incorporated in the opening 2a. The mirror 10 constitutes a part of the wall on the upstream side of the vacuum container 2. The reflecting surface 10a of the mirror 10 is located in the vacuum container 2, and the back surface 10b of the mirror 10 is exposed to the atmosphere outside the vacuum container 2. A magnetic fluid seal 9 is interposed between the opening 2a of the vacuum vessel 2 and the side peripheral surface of the mirror 10, and the two are sealed. In this example, the mirror 10 is a mirror made of low thermal expansion glass (for example, Zerodur 1 or ULE) having a paraboloidal reflecting surface 10a. A multilayer film 12 made of Mo / Si is coated on the reflection surface 10a of the mirror 10 except for a part of the center of the surface. The multilayer film 12 is configured to reflect X-rays having a wavelength of 13.5 nm. The mirror 10 is arranged so that the plasma P is located at the focal position. Among the X-rays radiated from the plasma P, the X-rays having a wavelength of 13.5 ηm are reflected by the reflecting surface 10a of the mirror 10 and become an X-ray luminous flux E, which is guided to the subsequent optical system.

A water cooling jacket (mirror cooling mechanism) 15 is attached to the back surface 10 b of the mirror 10. The piping 15a of the water cooling jacket 15 is connected to a water source pump (not shown). The water-cooling jacket 15 cools the mirror 10 whose temperature has been increased by receiving radiant heat from the plasma P. Since this water-cooled jacket 15 is provided on the air side of the mirror back 10 b, The wiring of 15a is easy and the configuration is simple. In addition, maintenance is easy because the water cooling jacket 15 is exposed to the atmosphere.

A laser light source 5 is disposed upstream of the back surface 10 b of the mirror 10. A lens 6 is arranged between the mirror 10 and the laser light source 5. The lens 6 focuses one YAG laser light L emitted from the laser light source 5 to the tip of the gas jet nozzle 4. At this time, the YAG laser light L passes through the center of the mirror 10 (the portion where the multilayer film 12 is not coated). When the focused YAG laser light L is applied to the evening gas, plasma P is generated, and from this plasma P, a line is radiated. At this time, the target gas ejected from the gas jet nozzle 4 is exhausted to the outside of the vacuum vessel 2 by the vacuum pump 3 after the plasma P is generated. In this embodiment, the lens 6 is provided separately. However, the portion of the mirror 10 through which the laser beam passes can be made convex so as to serve also as the lens, and the lens 6 can be omitted.

On the back surface 10 b side of the mirror 10, a flange portion 13 that protrudes in a flange shape is formed. The flange portion 13 is engaged with an engagement protrusion 14 formed on the outer surface of the vacuum vessel 2. A piezo element 8 (adjustment means) is mounted between the vacuum vessel 2 and the flange portion 13 of the mirror 10. The piezo element 8 is an actuating device for adjusting the mirror to a normal position and orientation after replacing the mirror. As shown in FIG. 2, the piezo element 8 is connected to a control device 33, and operates in response to a signal from the control device 33. In this embodiment, a material transparent to laser light is used as the mirror member, but an opaque material such as silicon, aluminum, or copper may be used. In this case, an opening may be provided in a portion of the mirror through which the laser beam passes, and a member (for example, quartz or the like) transparent to the laser beam may be attached to the opening. When a metal such as silicon, aluminum or copper is used as a mirror member, the cooling efficiency is increased due to high thermal conductivity.

As shown in FIG. 2, a semiconductor laser 30 and a photodiode 31 (detection means) are arranged in a vacuum vessel 2. These semiconductor lasers The position and orientation of the mirror 10 are detected by the photodiode 31. As an example, three or more semiconductor lasers 30 are arranged around the mirror 10. The photodiode 31 is disposed around the mirror 10 corresponding to each semiconductor laser 30. The semiconductor laser 30 and the photodiode 31 are arranged on the reflection surface 10a side of the mirror 10, and are arranged at positions where the X-rays reflected by the mirror 10 are not blocked. The semiconductor laser 30 and the photodiode 31 are connected to a control device 33 in the same manner as the piezo element 8, and outputs a position / posture detection signal of the mirror 10 to the control device 33. Note that FIG. 2 does not show the gas jet nozzle 4, the laser light source 5, the lens 6, etc. of FIG.

The beam emitted from each of the semiconductor lasers 30 strikes one point of the reflecting surface 10a of the mirror 10 and is reflected, and is incident on the corresponding photodiode 31. The light receiving surface of each photodiode 31 is divided into four, and a detection signal can be extracted from each of the four divided light receiving surfaces. Four detection signals from one photodiode are input to the control device 33. The control device 33 controls the piezo element 8 based on the detection signal, and adjusts the positions of the gas jet nozzle 4 and the mirror 10 and the alignment of the subsequent optical system (see FIG. 1).

Here, the overall operation of the X-ray generator 1 having the above-described configuration will be described.

One light L of the YAG laser emitted from the laser light source 5 passes through the center of the lens 6 and the mirror 10 and is focused on the gas jet nozzle 4. The target gas ejected from the gas jet nozzle 4 at supersonic speed becomes high temperature by receiving the energy of the condensed YAG laser beam L and generates plasma P. X-rays are emitted when the ions in this plasma transition to a low potential state. Among the X-rays incident on the mirror 10, the X-rays having a wavelength of about 13.5 nm are reflected by the multilayer film 12 formed on the mirror reflection surface 10 a to become an X-ray luminous flux E, which is a vacuum. It is guided from the downstream side of the container 2 to the subsequent optical system (see Fig. 1). A heat load is applied to the reflecting surface 10a of the mirror 10 by radiant heat from the plasma P. However, since the mirror 10 is cooled by the water-cooling jacket 15, the temperature rise can be kept low. Alternatively, since the back surface 10b of the mirror 10 is exposed to the atmosphere side, the heat of the mirror 10 is radiated to the atmosphere, thereby suppressing the temperature rise.

When scattered particles from the plasma P accumulate on the reflecting surface 10a of the mirror 10 due to the long-time operation of the X-ray generator 1, the X-rays reflected on the reflecting surface 10a of the mirror 10 The amount of light decreases. In this case, the original mirror needs to be replaced with a new mirror. During this replacement work, the mirror 10 constitutes a part of the wall of the vacuum vessel 2, so that the deteriorated mirror can be quickly and easily replaced with a new mirror from the atmosphere side. Therefore, the X-ray generator 1 can quickly return to the original state.

Here, the position of the newly installed mirror may be slightly different from the position of the original mirror. When such a displacement occurs, the position of the reflected light of the laser from the semiconductor laser 30 shown in FIG. 2 detected on the photodiode 31 changes. Therefore, the detection value output from the photodiode 31 also changes. Therefore, the control device 33 drives the piezo element 8 so that the output value of the photodiode 31 substantially matches the condition of the initial state when the original mirror is adjusted. In this way, a new mirror can be placed at the same position as the original mirror position. In this embodiment, a piezo element is used as the mirror position adjusting means. However, the present invention is not limited to this, and various other elements such as a motor can be used as long as the mirror position can be changed. Monkey

Returning to FIG. 1, the overall configuration of the X-ray exposure apparatus having the X-ray generator 1 will be described.

A vacuum chamber 20 is connected to the downstream side of the vacuum vessel 2. In the vacuum chamber 20, a filter 21 and an aperture plate 23 are arranged. The filter 21 is made of, for example, zirconium (Zr) having a thickness of 0.1 m. Visible · Cuts out ultraviolet light. The aperture plate 23 has a disk shape and is disposed downstream of the filter 21. At the center of the aperture plate 23, a pinhole 23a is formed. The portion around the pinhole 23a of the aperture plate 23 plays a role of blocking scattered X-rays and X-rays that are emitted directly downstream without being reflected by the mirror 10. It is also used to perform differential exhaust on the upstream and downstream sides of the pinhole to increase the degree of vacuum on the downstream side.

In the vacuum chamber 20, a gate valve 25 is provided below the opening plate 23. During maintenance such as replacement of the mirror of the X-ray generator 1, the gate valve 25 is closed to isolate the downstream illumination optical system 41 from the vacuum vessel 2. In this embodiment, the filter 21 is disposed upstream of the pinhole 23a, but the filter 21 may be disposed downstream of the pinhole 23a. By doing so, the X-rays irradiated to the filter 21 are only the X-rays reflected by the mirror 10, so that there is an advantage that the heat load due to the X-rays absorbed by the filter 21 is reduced.

An exposure chamber 40 is provided below the vacuum chamber 20. In the exposure chamber 40, an illumination optical system 41, a mask 43, a projection optical system 45, and the like are arranged. The illumination optical system 41 is composed of a fly-eye optical system reflecting mirror or the like, and shapes the X-ray light beam reflected by the mirror 10 and irradiates it toward the upper right of FIG. In the upper right of FIG. 1 of the illumination optical system 41, a reflective mask 43 is arranged. A reflection film made of a multilayer film is also formed on the reflection surface of the reflection type mask 43. A mask pattern corresponding to the pattern to be transferred to the wafer 49 is formed on the reflection film. On the downstream side of the reflective mask 43, a projection optical system 45 and a wafer 49 are arranged in this order. The projection optical system 45 includes a plurality of reflecting mirrors and the like, and reduces the X-rays reflected by the reflective mask 43 to a predetermined reduction magnification (for example, 1Z4) and projects the X-rays on the wafer 49. In FIG. 1, the dimensions of the illumination optical system 41 and the projection optical system 45 are smaller than those of the X-ray generator 1.

When performing the exposure operation, the illumination optical system 41 irradiates the reflective surface of the reflective mask 43 with X-rays. At this time, the reflection type mask 43 and the projection optical system 45 The wafer 49 is relatively synchronously scanned at a predetermined speed ratio determined by the reduction magnification of the projection optical system. Thus, the entire circuit pattern of the reflective mask 43 is transferred to each of the plurality of shot areas on the wafer 49 by the step-and-scan method. The chips of the wafer 49 are, for example, 25 × 25 mm square.

In the above embodiment, the following modifications can be made.

In the above-described embodiment, the semiconductor laser 30 and the photodiode 31 for detecting the position and orientation of the mirror 10 are arranged in the vacuum vessel 2 (see FIG. 2). Therefore, as shown in FIG. 3, the photodiodes 31a to 31d divided into four parts can be arranged on the surface on the upstream side of the aperture plate 23. In this case, if the position of the mirror 10 shifts, the X-ray does not pass through the inside of the pinhole 23a and hits one of the photodiodes 31a to 31d. Alternatively, the area irradiated on one of the photodiodes increases, and the output signal strength of each photodiode changes. The position and orientation of the mirror can be adjusted based on the detection result of the photodiode at this time. Further, the mirror position can be more precisely adjusted by increasing the number of divided photodiodes.

In this example, a photodiode is used as the detector, but other detection means may be used. For example, as shown in Fig. 3, a metal plate (for example, gold) electrically insulated from the surroundings is placed around the pinhole, and an ammeter is individually connected between each metal plate and the ground. Good. In this case, if the position of the mirror shifts and the area irradiated on each metal plate changes, the number of photoelectrons emitted from the metal plate changes, and the indicated value of each ammeter connected to each metal plate changes Therefore, the position and attitude of the mirror can be adjusted based on this. Further, the number of photoelectrons emitted from the metal plate may be monitored instead of the amount of current flowing into the metal plate. FIG. 4 is a diagram showing another example of the X-ray generator.

In the above-described embodiment, one YAG laser beam emitted from the laser light source 5 The L is transmitted through the center of the mirror 10 and condensed, but as shown in Fig. 4, it does not pass through the mirror 10 and illuminates one light L of the YAG laser from the side of the mirror 10. It can also be collected by focusing. In such a configuration, since the temperature of the mirror 10 does not rise due to the transmission of the YAG laser light L, the temperature of the multilayer film 12 on the mirror reflecting surface 10a does not easily rise. Therefore, the multilayer film 12 is hardly deteriorated, and a decrease in the reflectance of the mirror 10 can be suppressed.

FIG. 5 (A) is a diagram showing another example of the X-ray generator, and FIG. 5 (B) is a front view of a mirror of the X-ray generator of FIG. 5 (A).

In the above-described embodiments shown in FIGS. 1, 2 and 4, a flange 13 is formed on the back surface 10b side of the mirror 10, and the mirror itself forms a part of the vacuum vessel 2. As shown in FIG. 5A, a mirror holding member 16 for holding the mirror 10 ′ with respect to the vacuum vessel 2 may be used. The mirror holding member 16 has the same flange portion 13 as described above, and forms a part of the vacuum vessel 2. The mirror 10 ′ is attached to the mirror holding member 16 in the vacuum vessel 2. As shown in Fig. 5 (B), the mirror 10 'in this example is composed of a plurality of (six in the figure) segment mirrors, and all segment mirrors constitute a paraboloid of revolution. You. Each segment mirror is attached to a mirror holding member 16 via a piezo element (position adjustment mechanism) 17. The example shown in FIG. 5 is suitable for a case where a single mirror is composed of a plurality of segment mirrors instead of an integral mirror in advance.

In the above-described embodiment, a multilayer mirror has been described as an example. However, the present invention is not limited to this, and can be applied to an X-ray generator using an oblique incidence mirror. Also, although the description has been given using a laser plasma X-ray source as the X-ray generator, it is also possible to use another plasma X-ray source such as a discharge plasma X-ray source. For example, when using a discharge plasma X-ray source, excitation, single laser light source and the optical system of the eye a laser light source was focused of ³ cells for a plasma target materials as in FIG. 1 is not required.

Furthermore, when guiding EUV light radiated from the plasma into the exposure chamber 40, Although the mirror 10 is used in FIG. 1, EUV light can be guided into the exposure chamber 40 by arranging a plurality of oblique incidence mirrors between the plasma P and the filter 21. is there. In this case, the whole of the plurality of oblique incidence mirrors arranged in an annular shape can be removed so as to replace the pipe. In this case, a pipe-shaped chamber wall may be used as a holding portion, and a plurality of oblique incidence mirrors may be arranged on the inner surface of the chamber. Alternatively, as shown in FIG. It may be configured to be exposed. The invention's effect

As is apparent from the above description, according to the present invention, there is provided an X-ray generator having advantages such as shortening of a mirror replacement time or facilitation of cooling of a mirror, and an exposure apparatus having the same. it can.

Claims

1. An X-ray source that converts a target material into plasma and emits X-rays from the plasma, and a vacuum container that contains the X-ray source.

A mirror on which X-rays radiated from the X-ray source are incident;

With

Mouth

An X-ray generator, wherein the member holding the mirror or the mirror blue constitutes a part of a wall of the vacuum vessel.

2. The X-ray generator according to claim 1, wherein a back surface of the mirror or a member holding the mirror is exposed outside the vacuum vessel.

3. The X-ray generator according to claim 2, wherein a mirror cooling mechanism is provided on a back surface of the mirror or a surrounding member holding the mirror.

4. A laser light source for generating a laser beam for converting the target material into plasma is provided.

The laser beam is transmitted through the mirror or a part of a member holding the mirror, or passes through an opening formed in the mirror and enters the vacuum container. The X-ray generator according to claim 1, 2 or 3.

5. Detecting means for detecting the position and orientation of the mirror,

Adjusting means for adjusting the position and orientation of the mirror;

Control means for controlling the adjusting means so as to receive a signal from the detecting means and to take a predetermined position and posture of the mirror;

The X-ray generator according to any one of claims 1 to 4, further comprising:

6. The X-ray generator according to any one of claims 1 to 5,

An exposure apparatus comprising: an illumination optical system that irradiates a mask with X-rays generated from the X-ray generation device; and a projection optical system that projects light reflected from the mask onto a sensitive substrate. .