JP5335298B2 - Extreme ultraviolet light source device and method of generating extreme ultraviolet light - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EUV (extreme ultraviolet) light source device which evaporates a target into one with appropriate density and shape, by irradiating on it CW light (including QCW light) before irradiation of main pulse laser light. <P>SOLUTION: For the first time, CW laser light 121 is irradiated on the target 200. With this, the target 200 is heated to evaporate and to be a gaseous target 210. Then, main pulse laser light 111 is irradiated on the gaseous target 210. With this, the gaseous target 210 gets plasmolyzed to emit EUV light. Since the target 200 is vaporized to be in a gaseous state just before an irradiation point where the main pulse laser light is irradiated, the main pulse laser light can be efficiently irradiated. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an extreme ultraviolet light source device and a method for generating extreme ultraviolet light.

  For example, a semiconductor chip is generated by reducing and projecting a mask on which a circuit pattern is drawn on a resist-coated wafer and repeating processes such as etching and thin film formation. With the miniaturization of semiconductor processes, light having a shorter wavelength is required.

  Therefore, a semiconductor exposure technique using light with an extremely short wavelength of 13.5 nm and a reduction optical system has been studied. This technique is called EUVL (Extreme Ultra Violet Lithography). Hereinafter, extreme ultraviolet light is referred to as EUV light.

  Three types of EUV light sources are known: LPP (Laser Produced Plasma) type light source, DPP (Discharge Produced Plasma) type light source, and SR (Synchrotron Radiation) type light source. The LPP-type light source is a light source that generates plasma by irradiating a target material with laser light and uses EUV light emitted from the plasma. The DPP type light source is a light source that uses plasma generated by discharge. The SR type light source is a light source that uses orbital radiation. Among the above three types of light sources, the LPP type light source can increase the plasma density and can increase the collection solid angle as compared with other methods, so that there is a possibility that high output EUV light can be obtained. high.

  Since EUV light has a short wavelength and is easily absorbed by substances, EUVL employs a reflective optical system. The reflective optical system is constructed using, for example, a multilayer film using molybdenum (Mo) and silicon (Si). Since the multilayer film of Mo / Si has a high reflectance near 13.5 nm, EUVL uses 13.5 nm EUV light.

  However, since the reflectance of the multilayer film is about 70%, the output of EUV light gradually decreases as reflection is repeated. Since EUV light is reflected ten times in the exposure apparatus, the EUV light source apparatus needs to supply high-power EUV light to the exposure apparatus. Therefore, an LPP type light source is expected as an EUV light source device (Patent Document 1).

  The LPP EUV light source device uses tin (Sn), xenon (Xe), lithium (Li), or the like as a target material, and irradiates the target material with laser light. In particular, an LPP-type light source that combines a liquid metal tin droplet (target) and a carbon dioxide (CO2) pulse laser may use the minimum amount of droplets and has high emission efficiency of EUV light. For this reason, it is seen as a promising configuration.

  By minimizing the amount of droplets, the amount of debris generated can be suppressed, and adverse effects on various optical components such as EUV collector mirrors can be reduced. However, since the amount of droplets is small, the irradiation diameter of the carbon dioxide laser tends to be larger than the diameter of the droplets. Since many laser beams pass without acting on the droplets, there is room for improvement in terms of output efficiency of EUV light.

Therefore, a technique for performing preforming by changing the shape and density of the droplet by irradiating the droplet with the pre-pulse laser before irradiating the droplet with the main pulse laser (Patent Document 2,). Patent Document 3).
JP 2006-80255 A US Patent Application Publication No. 2006/0255298 JGB Publication No. 2003/96764 pamphlet

  The prior art proposes a method of irradiating a target with a pre-pulse laser before irradiation with a main pulse laser. However, since a target of a metal material such as tin has a large heat capacity, it is difficult to evaporate the entire target even when irradiated with a prepulse laser. Ablation and evaporation generated in the droplet by the irradiation of the pulse laser stay on the surface of the droplet, so that many materials are scattered in a liquid state.

  The present invention has been made paying attention to the above problem, and its purpose is to evaporate a relatively large portion of the target material in advance by irradiation with the first laser beam, and to emit the second laser beam to the gaseous target. An object of the present invention is to provide an extreme ultraviolet light source device and an extreme ultraviolet light generation method capable of increasing the generation efficiency of extreme ultraviolet light by irradiation. Further objects of the present invention will become clear from the description of the embodiments described later.

In order to solve the above problem, an extreme ultraviolet light source device according to a first aspect of the present invention is an extreme ultraviolet light source device that generates extreme ultraviolet light by irradiating a target material with laser light to generate plasma. , a chamber, a first laser light source for the a target material supplying means for supplying a target material is evaporated by irradiating a first laser beam to the target material supplied into the chamber into the chamber, wherein A second laser light source for radiating extreme ultraviolet light by irradiating the target material heated by the first laser light with the second laser light to make the target material into plasma, and the plasma converted target material A condensing mirror for condensing extreme ultraviolet light emitted from the condensing mirror, the condensing mirror reflecting the first laser light Also used as a reflecting mirror for irradiating the target material was.

A plurality of first laser beams may be prepared, and the target materials may be irradiated with the plurality of first laser beams.
A plurality of first laser beams may be irradiated to different regions of the target material.
The target materials may be irradiated with the plurality of first laser beams at different positions on the target material movement path.
The first laser light may be continuously irradiated to the target material while following the movement of the target material.
The first laser beam may be formed in a predetermined shape according to the movement path of the target material.
The intensity of the first laser beam having a predetermined shape may be spatially modulated.
You may spatially modulate the intensity | strength of the 1st laser beam of a predetermined shape so that the intensity | strength of a 1st laser beam may increase as it approaches the irradiation point irradiated with a 2nd laser beam.
Increasing the intensity when the first laser beam continues to irradiate the target material following the movement of the target material within a predetermined range, and the target material reaches before the irradiation point irradiated with the second laser beam. You may let them.
A reflecting mirror for reflecting the first laser light to irradiate the target material can also be provided.

An additive for promoting at least absorption of the first laser beam may be added to the target material.

A method for generating extreme ultraviolet light according to a second aspect of the present invention is a method for generating extreme ultraviolet light by irradiating a target material with laser light to generate plasma, and supplying the target material into a chamber. the target material is evaporated by irradiating a first laser beam, plasma and the target material is irradiated with a second laser beam to the target material is heated by the first laser beam to be supplied to the chamber And collecting the extreme ultraviolet light radiated from the plasma target material using a condensing mirror, the condensing mirror reflecting the first laser light to irradiate the target material It is also used as a reflection mirror for making it happen .

  According to the present invention, the target material is evaporated by irradiating the target material with the first laser light configured as continuous light or pseudo continuous light before the second laser light is irradiated. be able to. Therefore, according to the present invention, the gaseous target can be irradiated with the second laser light, and the generation efficiency of extreme ultraviolet light can be increased.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, as described below, EUV light is obtained by changing the state of the target by irradiating the target with a plurality of different types of laser light. More specifically, in the present embodiment, first, the target is vaporized by irradiating the target with the first laser light configured as continuous light or pseudo continuous light, and then the first laser light configured as pulsed laser light. 2 A laser target is irradiated with a gas target.

  That is, in the present embodiment, EUV light is emitted by irradiating a target (for example, a liquid target made of a metal material) with a first laser beam in the vicinity of a position before the second laser beam is irradiated. Produce a gaseous target of suitable density and shape. Thereby, the gaseous target can be sent to the irradiation position of the second laser beam, and the second laser beam can be effectively irradiated to emit the EUV light efficiently.

  In other words, a minute target (a metal droplet) having a necessary minimum amount of mass can be changed to a gaseous state in front of the irradiation point of the second laser light to reduce the density, The absorption efficiency of the second laser light can be increased. Therefore, EUV light can be efficiently emitted.

  A first embodiment will be described with reference to FIGS. FIG. 1 is an explanatory diagram showing the overall configuration of the EUV light source device 1, and FIG. 2 is an explanatory diagram showing how the state of the target changes when a plurality of laser beams are irradiated.

  The EUV light source device 1 shown in FIG. 1 includes, for example, a vacuum chamber 100, a main pulse laser light source 110, a heating evaporation laser light source 120, a droplet supply unit 130, an exhaust pump 140, as will be described later. A control unit 150 and an EUV collector mirror 160 are provided. Heating evaporation means that the target 200 is heated and evaporated by irradiating the target (droplet) 200 with laser light configured as continuous light or pseudo continuous light.

  The vacuum chamber 100 is kept in a vacuum state by the exhaust pump 140. In the vacuum chamber 100, for example, a plurality of incident windows 101 and 102 and a gate valve 103 are provided. One incident window 101 is a window for allowing main pulse laser light from the main pulse laser light source 110 to enter the vacuum chamber 100. Another incident window 102 is a window for allowing continuous light or pseudo continuous light from the laser light source 120 for heating and evaporation to enter the vacuum chamber 100. The gate valve 103 is a valve for supplying EUV light generated in the vacuum chamber 100 to an exposure apparatus (not shown). The gate valve 103 is normally open, and allows EUV light to pass toward the exposure apparatus. At the time of maintenance, the gate valve 103 is closed.

  The droplet supply unit 130 supplies the target 200 by, for example, heating and melting a metal material such as tin (Sn). The target 200 is configured as a solid or liquid droplet. In this embodiment, description will be made by taking tin as an example of the target material. However, the present invention is not limited to this, and other materials such as lithium (Li) may be used. Alternatively, it is also possible to form droplets by using materials such as argon (Ar), xenon (Xe), krypton (Kr), water, alcohol, stannane (SnH4), tin tetrachloride (SnCl4) as a liquid or ice. Good. The droplet supply unit 130 can also be called a target supply unit. In the following description, the target may be called a droplet.

  The main pulse laser light source 110 outputs a pulse laser beam 111 for exciting the target 200 supplied from the droplet supply unit 130. The main pulse laser light source 110 corresponds to a “second laser light source device”, and the pulse laser light 111 corresponds to a “second laser light”. The main pulse laser light source 110 is configured as a CO2 (carbon dioxide gas) pulse laser light source, for example. The main pulse laser light source 110 outputs a laser beam 111 having a wavelength of about 10.6 μm, for example. The main pulse laser beam 111 enters the vacuum chamber 100 via the condenser lens 112 and the incident window 101 and irradiates the gaseous target 210. In addition, although a CO2 pulse laser is mentioned as an example as a laser light source, this invention is not limited to this.

  The laser beam source 120 for heating and evaporating is a light source device for adjusting the shape and state of the droplet in advance. The heating evaporation laser light source 120 corresponds to a “first laser light source device”, and the laser light 121 corresponds to a “first laser light”. The laser light source 120 for heat evaporation outputs, for example, laser light of continuous light (CW) or pseudo continuous light (Quasi-CW). The continuous light or quasi-continuous light in the present embodiment can be defined as, for example, laser light having a peak intensity that is below the ablation threshold of the droplet surface.

  As the heat evaporation laser light source 120, for example, a laser light source such as a YAG (Yttrium Aluminum Garnet) laser can be used. However, the type of the laser light source for heating and evaporation is not particularly limited in the present invention. For example, a carbon dioxide gas laser, an Nd: YAG laser, a Yb: YAG laser, or their harmonic light may be used.

  Further, a laser diode having an oscillation wavelength from visible light to the near infrared region may be used. In the case of using laser diode light, it is easy to irradiate a minute target 200 by increasing the luminance by fiber coupling. In order to further improve the luminance, a fiber laser may be used.

  The laser beam 121 output from the heating and evaporation laser light source 120 enters the vacuum chamber 100 through the incident window 102 and irradiates the droplet target 200. In the following description, unless otherwise specified, continuous light and pseudo continuous light are collectively referred to as “continuous light” or “CW laser light”. Further, the heat evaporation laser light source 120 may be referred to as a “CW laser light source”.

  Note that the CW laser beam 121 may be introduced into the vacuum chamber 100 using a fiber without using the incident window 102. For example, when there is a possibility of spatial interference with other components of the EUV light source device 1 or when it is desired to keep the CW laser light source 120 away from a high magnetic field / high electromagnetic field environment, a CW laser using a fiber is used. The light 121 may be guided into the vacuum chamber 100.

  The control unit 150 is a device that controls the operation of the EUV light source device 1. For convenience of explanation, the control unit 150 of this embodiment controls operations of the laser light sources 110 and 120, the droplet supply unit 130, and the like. In FIG. 1, for convenience, a single control unit 150 is illustrated as controlling laser light irradiation, droplet supply, and the like, but the operation of the laser light source device and droplet supply are controlled separately. It may be configured to be controlled by an apparatus.

  The EUV collector mirror 160 is a mirror for reflecting and collecting EUV light. The EUV collector mirror 160 may be provided with a hole 161 through which the main pulse laser beam 111 passes. The surface of the EUV collector mirror 160 is configured to have at least one curvature as a whole. The surface of the EUV collector mirror 160 is configured as, for example, a concave surface such as a spheroid, a paraboloid, a spherical surface, or a concave surface having a plurality of curvatures. The EUV collector mirror 160 reflects EUV light of about 13 nm by, for example, a multilayer film (Mo / Si) composed of a molybdenum film and a silicon film.

    EUV light collected by the EUV collector mirror 160 is sent to the exposure apparatus via the gate valve 103 and the like. In order to increase the purity of EUV light, optical components such as a diffraction grating and a filter may be used.

  As illustrated in FIG. 2, the droplet supply unit 130 melts a metal material with, for example, a heating device, and injects the molten metal with vibration. Accordingly, the droplet supply unit 130 supplies the target 200 having the necessary minimum amount of material into the vacuum chamber 100 at predetermined intervals. The target 200 moves in the vacuum chamber 100 toward the lower side in FIG.

  The target 200 is irradiated with CW laser light 121 as the first laser light at a predetermined position IP1. The predetermined position can also be called, for example, a first irradiation point or a pre-laser irradiation point. The predetermined position IP1 can be set, for example, at a position before the position IP2 to which the main pulse laser beam 111 is irradiated with reference to the moving direction of the droplet. Alternatively, the position IP1 and the position IP2 can be set to substantially the same position. The position IP2 may be called, for example, a second irradiation point or a main laser irradiation point. In the figure, the position of the irradiation point is indicated by parentheses in the reference numeral of the target.

  The target 200 is irradiated with the CW laser beam 121 at the first irradiation point IP1. The beam diameter of the CW laser beam 121 is set according to the diameter of the target 200. The CW laser beam 121 irradiates and heats the target 200 for a period of about several μs to several tens of μs, for example. As a result, a part or all of the droplet-like liquid metal target 200 evaporates and changes into a gaseous target 210.

  The gaseous target 210 continuously expands and expands while moving toward the second irradiation point IP2. Then, at the second irradiation point IP2, the main pulse laser beam 111 is irradiated to the gaseous target 210 having an increased volume. As a result, the gaseous target 210 is turned into plasma and EUV light is emitted. The emitted EUV light is collected by the EUV collector mirror 160 and sent to the exposure apparatus.

  A case where a YAG laser light source is used as the CW laser light source 120 will be described as an example. When the target 200 having a diameter of about 10 μs and a diameter of about 30 μm is irradiated with a laser beam 121 of 100 watts, the target 200 can be evaporated to an appropriate density. The appropriate density means an appropriate density according to the wavelength of the main pulse laser beam 111, the type of atoms constituting the target 200, and the like. For example, when the main pulse laser light source 110 is a carbon dioxide laser light source, EUV light can be obtained with high efficiency when the density of the target reaches a gas level.

  A part or all of the target 200 evaporates to generate a gaseous target 210 having an appropriate density. The gaseous target 210 is irradiated with main pulse laser light 111 from a main pulse laser light source 110 such as a carbon dioxide laser light source. When the gaseous target 210 is irradiated with a carbon dioxide laser having a pulse width of 20 ns and an output of 100 mJ or less, the conversion efficiency for generating EUV light from the laser light can be increased to about 4%.

  On the other hand, when the pre-pulse laser beam is used as in the prior art, the irradiation time to the target 200 is shortened. Considering the evaporation process of metallic droplets such as liquid tin, when the diameter of the droplets is several tens of μm, it takes about several μs for heat transfer in the droplets. For example, consider the case of evaporating a 30 μm diameter, molten tin droplet. Tin has a melting point of 232 ° C. and a boiling point of 2270 ° C. The minimum heating time required to evaporate the tin droplets can be estimated at about 4 μs. The value of 4 μs does not take into account the laser absorptivity on the droplet surface. Considering the absorption rate of the laser wavelength, a longer heating time is required.

  However, the pulse width of the pre-pulse laser is several ns to several tens ns, which is significantly shorter than the required heating time. In order to evaporate the droplets and produce a target of appropriate density, it is necessary to heat on a longer time scale. Evaporating the droplets into a gaseous target is referred to herein as preforming.

  In order to realize appropriate preforming, it is necessary to irradiate droplets for a relatively long time (several μs) while suppressing the peak output of the laser used for preforming. However, in the conventional prepulse laser, gas and / or plasma are instantaneously expanded by ablation of the droplet surface. For example, when the pulse energy is 10 mJ and the focused size (droplet diameter) is several tens of μm with visible laser light, the ablation pressure reaches several tens to several hundreds of gigapascals. Due to such a high pressure, the base of the droplet is split and scattered, and as a result, most of the droplet does not contribute to the generation of EUV light.

  More simply expressed, in the conventional prepulse laser, the ablation and / or evaporation of the droplets stays on the surface of the droplets, and many of the droplets are scattered in a liquid state and become debris.

  Therefore, in this embodiment, as described above, as the first stage, the target 200 is irradiated with the CW laser light 121, the target 200 is evaporated, and the gaseous target 210 is changed. In the second step, the target pulse 210 is irradiated with the main pulse laser beam 111 to make the target 210 into plasma and emit EUV light.

  Therefore, in this embodiment, even when the diameter of the main pulse laser beam 111 is large, most of the necessary minimum amount of the target 200 can be changed to the gaseous target 210 to reduce the density, and the main pulse laser beam 111 can be reduced. Energy absorption can be increased. Therefore, EUV light can be extracted more efficiently than before.

  In this embodiment, by setting the irradiation conditions (for example, peak output, irradiation time, wavelength, etc.) of the CW laser light 111, the shape and density of the gaseous target 210 can be controlled to some extent. Therefore, the gaseous target 210 suitable for generation of EUV light can be obtained (preforming suitable for EUV light emission is possible), and higher conversion efficiency than conventional can be achieved.

  In the present embodiment, since the CW laser light 121 is used, the target 200 can be irradiated for a longer time than in the case where the prepulse laser light is used. Therefore, the peak output of the CW laser beam 121 can be made smaller than the peak output of the pre-pulse laser beam. Therefore, in this embodiment, most of the target 200 can be evaporated, and most of the target 200 can contribute to EUV light generation. That is, in this embodiment, the volume utilization efficiency of the target 200 can be improved and debris can be reduced as compared with the conventional technique using a prepulse laser.

  Further, in the present embodiment, since the CW laser beam 121 is used, even when the EUV light generation process is requested at a higher cycle than it is, the higher cycle can be handled without any problem.

  In this embodiment, since the gaseous target 210 is generated and the main target laser beam 111 is irradiated to the gaseous target 210, generation of debris due to the residue of the target 210 can be suppressed. Therefore, it is possible to effectively reduce the contamination or damage of various optical components in the vacuum chamber 100 and the exposure apparatus due to debris, and the reliability can be improved.

  A second embodiment will be described with reference to FIG. Each embodiment described below corresponds to a modification of the first embodiment. Therefore, the difference from the first embodiment will be mainly described. In this embodiment, the target 200 can be heated uniformly using a plurality of CW laser beams 121 (1) to 121 (4).

  FIG. 3 is an explanatory diagram showing a main part of the EUV light source apparatus 1 according to the present embodiment. In the present embodiment, a plurality of (four) CW laser light sources 120 (1) to 120 (4) are arranged around the first irradiation point IP1. The CW laser light sources 120 (1) to 120 (4) are provided, for example, 90 degrees apart in the circumferential direction. Further, in order to avoid disagreement between the opposing laser beams, they may be arranged at positions shifted from 90 degrees to several degrees. In other words, for example, they may be arranged 90 degrees apart from each other, such as 0 degrees, 90 degrees, 180 degrees, and 270 degrees, or 3 degrees, 93 degrees, and 180 degrees in order to avoid laser beams. You may arrange | position several times like 270 degree | times. In addition, although 3 degree | times was mentioned as an example of several degrees, it is only an example and this invention is not limited to the numerical value.

  Each CW laser light source 120 (1) to 120 (4) irradiates the target 200 that has reached the first irradiation point IP1 with CW laser light 121 (1) to 121 (4), respectively. As a result, the target 200 is heated and evaporated to change into a gaseous target 210.

  Configuring this embodiment like this also achieves the same effects as the first embodiment. Further, in this embodiment, the target 200 is heated from different angles by the plurality of CW laser beams 121 (1) to 121 (4). Therefore, in this embodiment, the target 200 can be heated more uniformly and evaporated without waste.

  Note that the peak outputs of the CW laser beams 121 (1) to 121 (4) can be set to be the same or different from each other. What is necessary is just to set the output of each CW laser beam 121 (1) -121 (4) according to the kind of atom which comprises the target 200, and the state and shape of the target 200. FIG.

  A third embodiment will be described with reference to FIG. In this embodiment, the CW laser beam 121 is caused to follow the movement of the target 200. FIG. 4 is an explanatory view showing a main part of the EUV light source apparatus 1 according to the present embodiment.

  A sweep mechanism is provided between the CW laser light source 120 and the target 200. The sweep mechanism includes, for example, a reflection mirror 301 and a rotation mirror 302. The CW laser light 121 emitted from the CW laser light source 120 is reflected by the reflection mirror 301 and enters the rotating mirror 302.

  The rotating mirror 302 rotates within a predetermined range set in advance according to the movement of the target 200. Therefore, the CW laser beam 121 incident on the rotating mirror 302 is reflected according to the angle of the rotating mirror 302 and irradiates the target 200. When the target 200 reaches the first position IP1a of the first irradiation point, the CW laser beam 121 is irradiated. The CW laser light in this case is indicated by reference numeral 121 (F). Then, the angle of the rotating mirror 302 changes continuously according to the movement (falling) of the target 200.

  The target 200 is continuously irradiated with the CW laser beam 121 until the target 200 reaches the final position IP1b of the first irradiation point. The CW laser beam at the final position IP1b is indicated by reference numeral 121 (L). At the last position IP1b of the first irradiation point, the density of the target 200 decreases and evaporation starts. Therefore, the target code is changed to 201 in the figure. However, when it is not necessary to distinguish between them, the target 200 and the target 201 are used without being distinguished.

  Configuring this embodiment like this also achieves the same effects as the first embodiment. Furthermore, in this embodiment, the CW laser beam 121 is swept following the movement of the target 200, so that a longer irradiation time than that of the first embodiment can be ensured. Therefore, even when the moving speed of the target 200 is fast, the target 200 can be gasified by the CW laser beam 121.

  A fourth embodiment will be described with reference to FIGS. In the present embodiment, the CW laser beam 121 is incident on the heating mirror 310 and reflected to collect the CW laser beam 121 on the target 200 and heat it. In this embodiment, a modified example will be described.

  FIG. 5 is an explanatory view schematically showing a main part of the EUV light source apparatus 1 according to the present embodiment. FIG. 5A is an explanatory diagram showing the mutual relationship between the heating mirror 310, the target 200, and the CW laser beam 121, and FIG. 5B is a plan view of FIG. 5A viewed from above.

  The heating mirror 310 has a curved mirror surface such as a spheroid, and has a relatively high reflectivity with respect to the CW laser beam 121. The heating mirror 310 is provided in the vacuum chamber 100 so as to surround the first irradiation point IP1 and so as not to prevent the movement of the target 200.

  The target 200 enters the space formed by the heating mirror 310 from the upper side in FIG. The CW laser beam 121 is set so as not to directly irradiate the target 200 but to enter the mirror surface of the heating mirror 310. The CW laser beam 121 is incident on the mirror surface of the heating mirror 310 from either the left or right direction with respect to the target 200 moving from top to bottom. Then, as shown in FIG. 5B, the CW laser beam 121 is reflected by the mirror surface of the heating mirror 310 and irradiates the target 200 from the back side.

  By making the position of the focal point formed by the mirror surface of the heating mirror 310 substantially coincide with the first irradiation point IP1, the CW laser light 121 incident on the heating mirror 310 can be collected toward the target 200.

  Furthermore, in this embodiment, the CW laser beam 121 is swept from the top to the bottom in FIG. 5 to follow the movement of the target 200. Thereby, as described in the third embodiment, the irradiation time can be lengthened.

  FIG. 6 is an explanatory diagram showing another example. In the example shown in FIG. 5, the CW laser beam 121 is incident on the heating mirror 310 from either the left or right side of the target 200. On the other hand, in the example shown in FIG. 6A, the CW laser beam 121 is incident on the heating mirror 310 from above or below the target 200. FIG. 6 shows a case where the CW laser beam 121 is incident from the lower side. As shown in FIG. 6B, the CW laser beam 121 is reflected by the heating mirror 310 and irradiates the target 200 that moves along the focal position. Also in the example shown in FIG. 6, the CW laser beam 121 can be swept according to the movement of the target 200.

  Configuring this embodiment like this also achieves the same effects as the first embodiment. Further, in this embodiment, the target 200 is not directly irradiated with the CW laser light 121 but is reflected by the heating mirror 310 to irradiate the target 200. Thereby, the target 200 can be heated more uniformly.

  A fifth embodiment will be described with reference to FIG. FIG. 7 is an explanatory diagram schematically showing the waist of the EUV light source device 1 according to the present embodiment. In the fourth embodiment, the case where the heating mirror 310 is provided in parallel with the moving direction of the target 200 has been described. On the other hand, in the present embodiment, the heating mirror 320 is disposed so as to cross the moving direction of the target 200. For this reason, the heating mirror 320 is provided with a hole 321 through which the target 200 passes.

  The CW laser beam 121 enters the mirror surface of the heating mirror 320 from below the heating mirror 320 as if looking up at the target 200. The CW laser beam 121 is reflected by the heating mirror 320 and irradiates the back side of the target 200. Configuring this embodiment like this also achieves the same effects as the first and fourth embodiments.

  A sixth embodiment will be described with reference to FIG. In this embodiment, a plurality of CW laser beams 121 (R) and 121 (F) and a heating mirror 310 are used to irradiate and heat the front surface and the back surface of the target 200.

  A case where the present invention is applied to the configuration described in FIG. 5 will be described as an example. The CW laser light source 120 (R) for backside heating is provided so as to face the mirror surface of the heating mirror 310. The CW laser beam 121 (R) emitted from the CW laser light source 120 (R) for backside heating is incident on the mirror surface of the heating mirror 310 and reflected, and irradiates the back side of the target 200.

  The CW laser light source 120 (F) for front heating is disposed so as to face the front of the target 200. Here, the back surface and the front surface indicate a relative positional relationship, and the side irradiated with the CW laser light 121 (R) is the back surface, and the side irradiated with the CW laser light 121 (F) is the front surface. The CW laser light 121 (F) emitted from the CW laser light source 120 (F) for front heating irradiates and heats the front of the target 200. Each CW laser beam 121 (R), 121 (F) can be swept according to the movement of the target 200.

  Configuring this embodiment like this also achieves the same effects as the first and fourth embodiments. Furthermore, in this embodiment, the target 200 is heated from different surfaces using a plurality of CW laser beams 121 (R) and 121 (F), and thus the target 200 can be heated and evaporated more uniformly. it can.

  A seventh embodiment will be described with reference to FIG. In this embodiment, a plurality of heating mirrors 310 (1) and 310 (2) are used to reflect the CW laser beams 121 (1) and 121 (2), respectively, and irradiate the target 200.

  FIG. 9 is an explanatory view schematically showing a main part of the EUV light source apparatus 1 according to the present embodiment. As shown in FIGS. 9A and 9B, in this embodiment, two heating mirrors 310 (1) and 310 (2) as described in FIGS. use. Each of the heating mirrors 310 (1) and 310 (2) is disposed so as to surround the target 200 from the outside and to be parallel to the moving direction of the target 200.

  Two gaps are formed between the heating mirrors 310 (1) and 310 (2) facing each other. CW laser beams 121 (1) and 121 (2) enter through these gaps, are reflected by the heating mirrors 310 (1) and 310 (2), and irradiate the target 200 from different directions. .

  As shown in FIG. 9B, the first CW laser beam 121 (1) is reflected by the mirror surface of the first heating mirror 310 (1) and irradiates one side of the target 200. The second CW laser beam 121 (2) is reflected by the mirror surface of the second heating mirror 310 (2) and irradiates the other side of the target 200. The CW laser beams 121 (1) and 121 (2) may be swept according to the movement of the target 200 to track the target 200. Also, the CW laser light 121 (1) and 121 (2) may be output from different CW laser light sources, respectively, or the CW laser light output from the same CW laser light source may be branched by an optical system to generate a CW laser. The structure which obtains the light 121 (1) and 121 (2) may be sufficient.

  Configuring this embodiment like this also achieves the same effects as the first and fourth embodiments. Further, in this embodiment, since the plurality of heating mirrors 310 (1) and 310 (2) and the plurality of CW laser beams 121 (1) and 121 (2) are used, the target 200 is heated more uniformly. Can be evaporated.

  The eighth embodiment will be described with reference to FIGS. In this embodiment, the target 200 is irradiated with the CW laser light 121 (1) and 121 (2) from either before or after the moving direction of the target 200. 10 and 11 are explanatory views schematically showing the main part of the EUV light source apparatus 1 according to the present embodiment. FIG. 10 shows an example in which the target 200 is irradiated from the rear side in the moving direction of the target 200. FIG. 11 shows an example in which the target 200 is irradiated from the front side in the moving direction of the target 200.

  The configuration example of FIG. 10 will be described first. A heating mirror 320 is provided above the first irradiation point IP1. That is, the heating mirror 320 is arranged on the rear side with respect to the moving direction of the target 200. The heating mirror 320 is arranged so as to be curved downward, and a hole 321 for allowing the target 200 to pass therethrough is provided at the center thereof.

  Rotating mirrors 330 (1) and 330 (2) are respectively provided on the left and right sides of the heating mirror 320 so as to face the heating mirror 320. Each of the rotating mirrors 330 (1) and 330 (2) rotates according to the movement of the target 200.

  The CW laser beam 121 (1) from the first CW laser light source 120 (1) is reflected by the rotating mirror 330 (1) and enters the heating mirror 320. The CW laser beam 121 (1) is reflected by the heating mirror 320 and irradiates the target 200 from the back surface of the target 200.

  Similarly, the CW laser light 121 (2) emitted from the second CW laser light source 120 (2) irradiates the back surface of the target 200 via the rotating mirror 330 (2) and the heating mirror 320. Furthermore, the CW laser beams 121 (1) and 121 (2) continue to be irradiated by tracking the target 200 by the swinging of the rotating mirrors 330 (1) and 330 (2).

  A configuration example of FIG. 11 will be described. In FIG. 11, the heating mirror 320 </ b> A is arranged on the front side with respect to the moving direction of the target 200. That is, the heating mirror 320A is provided between the first irradiation point IP1 and the second irradiation point IP2. The heating mirror 320A is provided to be curved upward.

  Rotating mirrors 330A (1) and 330A (2) are respectively provided on the left and right sides of the heating mirror 320A so as to face the heating mirror 320A. Each rotating mirror 330A (1), 330A (2) rotates according to the movement of the target 200.

  Hereinafter, as described in FIG. 10, the CW laser light 121 (1) emitted from the first CW laser light source 120 (1) passes through the rotating mirror 330 </ b> A (1) and the heating mirror 320 to the target. The front surface of 200 is irradiated. The CW laser beam 121 (2) emitted from the second CW laser light source 120 (2) irradiates the front surface of the target 200 via the rotating mirror 330A (2) and the heating mirror 320. Furthermore, the CW laser beams 121 (1) and 121 (2) continue to be irradiated by tracking the target 200 by the swinging of the rotating mirrors 330A (1) and 330A (2).

  Configuring this embodiment like this also achieves the same effects as the first and fourth embodiments. Note that the number of CW laser beams incident on the heating mirror 320 is not limited to two. For example, three, four, or five or more CW laser beams may be incident on the heating mirror 320 to heat the target 200 from more directions.

  A ninth embodiment will be described with reference to FIGS. In this embodiment, the EUV collector mirror 160 is used instead of the heating mirror. FIG. 12 is an explanatory diagram showing the overall configuration of the EUV light source apparatus 1 according to this embodiment.

  The CW laser light 121 emitted from the CW laser light source 120 is incident on the mirror surface outside the EUV collector mirror 160 and reflected to irradiate the target 200. That is, in this embodiment, the EUV collector mirror 160 is used as a reflection mirror for reflecting the CW laser beam 121.

  The EUV collector mirror 160 is formed as a multilayer film in which molybdenum and silicon are alternately laminated as described above. The EUV collector mirror 160 can reflect EUV light having a center wavelength of 13.5 nm with a reflectance of, for example, about 70%. For example, the EUV collector mirror 160 reflects the CW laser beam 121 having a wavelength of about 1.06 μm with a predetermined reflectance. Therefore, in this embodiment, the EUV collector mirror 160 is also used as a heating mirror.

  FIG. 13 is an explanatory diagram showing a modification of the present embodiment. In the example illustrated in FIG. 13, the first CW laser beam 121 (1) is incident on the EUV collector mirror 160 from the upper side (the rear side in the target moving direction). Thus, the first CW laser beam 121 (1) is reflected by the EUV collector mirror 160 and irradiates one side of the target 200.

  Further, the second CW laser beam 121 (2) irradiates the other side of the target 200 from a slightly lower side (a front side in the target moving direction). Therefore, one side and the other side of the target 200 are irradiated and heated by different CW laser beams. Furthermore, in this embodiment, the CW laser beams 121 (1) and 121 (2) are swept according to the movement of the target 200 and irradiated while tracking the target 200.

  FIG. 14 is an explanatory diagram showing another modification of the present embodiment. In the example shown in FIG. 14, the first CW laser light source 120 (1) directly irradiates one side of the target 200 and the second CW laser light source 120 (2) is EUV contrary to the example shown in FIG. The other side of the target 200 is irradiated using the condensing mirror 160.

  Configuring this embodiment like this also achieves the same effects as the first and fourth embodiments. Furthermore, in this embodiment, since the EUV collector mirror 160 is also used as a heating mirror, the number of parts can be reduced and the manufacturing cost can be reduced.

  A tenth embodiment will be described with reference to FIGS. In the present embodiment, the CW laser beam 121 (LB) is formed in a linear shape and arranged along the moving direction of the target 200.

  On the laser emission side of the CW laser light source 120, an optical system 340 for line beam shaping is provided. The optical system 340 is composed of parts such as a cylindrical lens and a slit, for example, and outputs linear laser light (line beam). Hereinafter, the linear CW laser beam 121 (LB) is also referred to as a line beam 121 (121LB).

  The line beam 121 (LB) is arranged along the moving direction of the target 200. The target 200 moves from the upper end to the lower end of the line beam 121 (LB). While passing through the line beam 121 (LB) up and down, the target 200 continues to be irradiated.

  FIG. 16 is an explanatory diagram showing one modification. As shown in FIG. 16, a heating mirror 310 may be used in addition to the line beam 121 (LB). In the example shown in FIG. 16, the heating mirror 310 is arranged on the outer peripheral side in the moving direction of the target 200 so as to surround the target 200. Then, the line beam 121 (LB) is incident on the heating mirror 310 and reflected to irradiate one side of the target 200.

  Configuring this embodiment like this also achieves the same effects as the first embodiment. Further, in this embodiment, the CW laser beam 121 (LB) is formed in a linear shape and arranged in accordance with the moving direction of the target 200. Therefore, in this embodiment, the time for irradiating the target 200 with the CW laser beam 121 (LB) can be extended. Thus, in this embodiment, the target 200 can be irradiated for a relatively long time using the CW laser beam 121 (LB) having a relatively small peak output. As a result, the target 200 can be heated and evaporated, and the gaseous target 210 having an appropriate density can be obtained.

  Furthermore, in this embodiment, since no mechanism part for sweeping the CW laser light in accordance with the movement of the target 200 is required, the number of movable parts can be reduced. Therefore, in this embodiment, the lifetime of the EUV light source device 1 can be extended.

  Note that the configuration shown in FIG. 9 and the configuration shown in FIG. 15 can be combined. That is, in FIG. 9, the CW laser beams 121 (1) and 121 (2) are configured as line beams, reflected by the heating mirrors 320 (1) and 320 (2), and irradiated on the target 200. May be.

  An eleventh embodiment will be described with reference to FIG. In this embodiment, a cylindrical heating mirror 350 and a line beam 121 (LB) are used.

  FIG. 17 is an explanatory diagram schematically showing a main part of the EUV light source apparatus 1 according to the present embodiment. FIG. 17A is a perspective view, and FIG. 17B is a cross-sectional view. The heating mirror 350 is formed in a cylindrical shape, and its inner peripheral surface is a mirror surface. The heating mirror 350 is provided with a slit 351 extending in the axial direction. The heating mirror 350 is disposed so as to surround the moving direction of the target 200.

  The line beam 121 (LB) enters the inside of the heating mirror 350 through the slit 351 and irradiates the target 200 while repeating reflection on the mirror surface. Configuring this embodiment like this also achieves the same effects as the tenth embodiment. Furthermore, in this embodiment, since the cylindrical heating mirror 350 and the line beam 121 (LB) are used, the target 200 can be heated from the entire circumference inside the heating mirror 350. Thereby, a gaseous target having a more appropriate density and shape can be obtained.

  A twelfth embodiment will be described with reference to FIG. In this embodiment, a plurality of CW laser beams 121 (LB) and 121 (2) are used, and the target 200 is irradiated at different timings.

  FIG. 18 is an explanatory view schematically showing a main part of the EUV light source apparatus 1 according to the present embodiment. In this embodiment, a plurality of CW laser light sources 120 (1) and 120 (2) are used. The CW laser light from the first CW laser light source 120 (1) is shaped into the line beam 121 (LB) by the line beam shaping optical system 340. The line beam 121 (LB) is disposed along the moving direction of the target 200.

  The CW laser beam 121 (2) from the second CW laser light source 120 (2) irradiates the target 200 after being irradiated with the line beam 121 (LB). That is, in this embodiment, the target 200 is irradiated with the line beam 121 (LB) on the upper side. Subsequently, in this embodiment, the target 200 is irradiated with CW laser light 121 (2) having a circular cross section on the lower side.

  In this embodiment, the target 200 is irradiated with the line beam 121 (LB) to raise the temperature of the target 200 to a temperature close to the evaporation temperature. The heated target is given the reference 201. Then, when the target 201 reaches the first irradiation point LP1, the target 201 is irradiated with the second CW laser beam 121 (2) to generate the gaseous target 210.

  Configuring this embodiment like this also achieves the same effects as the first and tenth embodiments. Furthermore, in this embodiment, since the CW laser beams 121 (LB) and 121 (2) are respectively incident on the target 200 in a plurality of stages, the time until the gaseous target 210 is obtained can be controlled. Thereby, before evaporating gas diffuses around, it can irradiate with the main pulse laser 111, and can make it plasma, and can radiate | emit EUV light.

  In the present embodiment, the case where the target 200 is heated in two stages has been illustrated, but the present invention is not limited to this, and a configuration in which heating is performed in three or more stages may be employed. Alternatively, the target 200 may be irradiated by overlapping the CW laser beams at the respective stages. Further, the peak output of the CW laser light at each stage does not need to be set to be the same, and can be set to different peak outputs.

  A thirteenth embodiment will be described with reference to FIG. In this embodiment, spatial intensity modulation is applied to the output of the line beam 121 (LB) shown in FIG. FIG. 19 shows how the output changes according to the length position of the line beam 121 (LB). On the upper side (entrance side) where the target 200 enters, the output of the line beam 121 (LB) is set to be relatively small. On the lower side (exit side) where the target 200 goes out of the range of the line beam 121 (LB), the output of the line beam 121 (LB) is set to be relatively high.

  Configuring this embodiment like this also achieves the same effects as the tenth embodiment. Further, in this embodiment, the output of the line beam 121 (LB) is set so as to gradually increase from the entrance side to the exit side of the target 200. Thereby, the target 200 can be gradually heated and finally the target 200 can be evaporated in a short time on the exit side of the line beam 121 (LB).

  A fourteenth embodiment will be described with reference to FIG. In the present embodiment, the output of the CW laser beam 121 is temporally changed in the third embodiment shown in FIG. At time t0 when the target 200 is first irradiated with the CW laser beam 121 (F), the peak output of the CW laser beam 121 (F) is set to P2.

  Then, at time t1 when the target 200 (201) is finally irradiated with the CW laser beam 121 (L), the peak output of the CW laser beam 121 (L) increases from P2 to P1 (P1> P2).

  Configuring this embodiment like this also achieves the same effects as the third embodiment. Further, in this embodiment, the target 200 can be evaporated and changed to the gaseous target 210 immediately before the target 200 is irradiated with the main pulse laser beam 111.

  A fifteenth embodiment will be described with reference to FIG. In this embodiment, an additive is supplied to the droplet supply unit 130. Accordingly, the droplet supply unit 130 supplies the target 200 mixed with the additive into the vacuum chamber 100. As the additive, for example, a substance that promotes absorption of laser light, such as carbon, is selected.

The block diagram of the EUV light source device which concerns on 1st Example. Explanatory drawing which shows typically the relationship between a target, CW laser beam, and main pulse laser beam. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 2nd Example. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 3rd Example. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 4th Example. Explanatory drawing which shows a modification. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 5th Example. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 6th Example. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 7th Example. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 8th Example. Explanatory drawing which shows a modification. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 9th Example. Explanatory drawing which shows a modification. Explanatory drawing which shows another modification. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 10th Example. Explanatory drawing which shows a modification. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 11th Example. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 12th Example. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 13th Example. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 14th Example. Explanatory drawing which shows the principal part of the EUV light source device which concerns on 15th Example.

Explanation of symbols

  1: EUV light source device, 100: vacuum chamber, 101, 102: entrance window, 103: gate valve, 110 main pulse laser light source, 111: main pulse laser light, 112: condenser lens, 120: CW (QCW) laser light source (Laser light source for heating evaporation), 121: CW laser light, 121 (LB): CW laser light shaped into a line beam, 130: droplet supply unit, 140: exhaust pump, 150: control unit, 160 EUV collector mirror , 161: hole, 200, 201: target, 210: gaseous target, 301: reflection mirror, 302: rotating mirror, 310, 320, 320A, 350: heating mirror, 330, 330A: rotating mirror, 340 : Optical system for line beam shaping, 351: Slit

Claims (12)

An extreme ultraviolet light source device that generates extreme ultraviolet light by irradiating a target material with laser light to generate plasma,
A chamber;
Target material supply means for supplying the target material into the chamber;
A first laser source for evaporating by irradiating a first laser beam to the target material supplied into the chamber,
A second laser light source for emitting extreme ultraviolet light by irradiating the target material heated by the first laser light with a second laser light to turn the target material into plasma;
A condensing mirror for condensing extreme ultraviolet light radiated from the plasma target material;
With
The condensing mirror is an extreme ultraviolet light source device that is also used as a reflection mirror for reflecting the first laser light to irradiate the target material .   2. The extreme ultraviolet light source device according to claim 1, wherein a plurality of the first laser beams are prepared and the target materials are irradiated with the plurality of first laser beams, respectively.   The extreme ultraviolet light source device according to claim 2, wherein each of the plurality of first laser beams is irradiated to different regions of the target material.   The extreme ultraviolet light source device according to claim 2, wherein the target materials are irradiated with the plurality of first laser beams at different positions on a movement path of the target material.   The extreme ultraviolet light source device according to claim 1, wherein the first laser light is continuously irradiated to the target material while following the movement of the target material.   The extreme ultraviolet light source device according to any one of claims 1 to 4, wherein the first laser light is formed in a predetermined shape corresponding to a movement path of the target material.   The extreme ultraviolet light source apparatus according to claim 6, wherein the intensity of the first laser beam having the predetermined shape is spatially modulated.   The extreme according to claim 7, wherein the intensity of the first laser beam having the predetermined shape is spatially modulated so that the intensity of the first laser beam increases as approaching the irradiation point irradiated with the second laser beam. Ultraviolet light source device.   When the target material continues to be irradiated with the first laser light following the movement of the target material within a predetermined range, and the target material reaches before the irradiation point irradiated with the second laser light The extreme ultraviolet light source device according to claim 1, wherein the intensity is increased.   The extreme ultraviolet light source device according to claim 1, further comprising a reflecting mirror that reflects the first laser light to irradiate the target material. The extreme ultraviolet light source device according to any one of claims 1 to 10 , wherein an additive for promoting at least the absorption of the first laser light is added to the target material. A method of generating extreme ultraviolet light by irradiating a target material with a laser beam to generate plasma,
Supplying the target material into the chamber;
The first laser beam evaporated by irradiating the target material to be supplied into the chamber,
Irradiating the target material heated by the first laser light with a second laser light to turn the target material into plasma ,
The extreme ultraviolet light radiated from the plasma target material is condensed using a condenser mirror.
Including
The method for generating extreme ultraviolet light , wherein the condensing mirror is also used as a reflection mirror for reflecting the first laser light to irradiate the target material .

Images