JP2008181760A - EUV light source, EUV exposure apparatus, and semiconductor device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EUV light source capable of supplying effectively a liquid target which generates EUV light by suppressing an effect of debris. <P>SOLUTION: The EUV light source generates plasma from a target (LQ) and emits EUV light generated by plasma, and is provided with a linear member (101). The target is a liquid and the linear member is constructed so that the target is supplied along the linear member. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light source for EUV (Extreme Ultraviolet) light and an exposure apparatus using the light source.

  In recent years, with the miniaturization of semiconductor integrated circuits, EUV (Extreme Ultraviolet) having a shorter wavelength (11 to 14 nm) is used in place of conventional ultraviolet rays in order to improve the resolution of an optical system limited by the diffraction limit of light. Projection lithography technology using light (extreme ultraviolet) has been developed. This technique is recently called EUV lithography, and is expected as a technique capable of obtaining a resolution of 70 nm or less, which cannot be realized by conventional optical lithography using light having a wavelength of about 190 nm.

  A laser plasma EUV light source (hereinafter, sometimes referred to as LPP (Laser Produced Plasma)) is particularly regarded as a promising EUV light generator used in such an exposure apparatus that uses EUV light. It is a discharge plasma EUV light source.

  LPP focuses pulse laser light on a target material (target) in a vacuum vessel, converts the target material into plasma, and uses EUV light radiated from the plasma.

  In addition, an EUV light source using discharge plasma such as Dense Plasma Focus (DPF) is small in size, has a large amount of EUV light, and is low in cost.

  As an EUV light source having a wavelength of 13.5 nm used in an EUV exposure apparatus, a device using Xe plasma using Xe gas or liquefied Xe as a target material (both laser plasma light source and discharge plasma light source) has been widely researched and developed. . The reason is that relatively high conversion efficiency (ratio of EUV light intensity obtained with respect to input energy) can be obtained, and Xe is a gas material at room temperature, so that there is a problem of contamination of optical elements due to debris (scattering particles). It is hard to occur.

  However, in order to obtain an EUV light source with higher output, there is a limit in using Xe gas as a target material, and it is desired to use a material with higher density. In order to use a higher density material, it is necessary to solve the problem of contamination of the optical element by debris.

  Here, contamination of the optical element due to debris will be described. Debris consists of a target scattered or a peripheral member sputtered by the target. In addition to debris adhering to the surface of the multilayer film and causing light absorption, the surface roughness is increased, or the multilayer film surface is scraped off by the debris, so that a multilayer film mirror used in an EUV light source ( The reflection efficiency of the condenser mirror is reduced. Further, since EUV light is absorbed by almost all substances, the inside of the EUV exposure apparatus is kept in a vacuum state. For this reason, debris is diffused widely from the EUV light source of the EUV exposure apparatus to the illumination optical system and the projection optical system, and the reflection efficiency of the multilayer mirror in these optical systems is similarly reduced. As a result, the amount of circuit printing light decreases, and the throughput of the EUV exposure apparatus decreases.

In order to obtain a higher output EUV light source, it has also been proposed to use a liquid metal as a target material (for example, Patent Document 1). However, an EUV light source that can effectively supply a liquid target that suppresses the influence of debris and generates strong EUV light has not been put into practical use.
WO2006 / 006408

  Therefore, there is a need for an EUV light source that can effectively supply a liquid target that suppresses the influence of debris and generates strong EUV light, and an EUV exposure apparatus that includes the EUV light source.

  An EUV light source according to the present invention is an EUV light source that generates plasma from a target and emits EUV light generated from the plasma. The EUV light source includes a linear member, the target is liquid, and the linear member is The target is configured to be supplied along the linear member.

  According to the present invention, an EUV light source capable of generating strong EUV light while suppressing the influence of debris can be obtained. Moreover, the EUV exposure apparatus according to the present invention using the EUV light source according to the present invention can achieve high throughput. Moreover, according to the semiconductor device manufacturing method of the present invention using the EUV exposure apparatus of the present invention, the semiconductor device can be manufactured with high throughput.

  FIG. 8 is a diagram showing a configuration of an EUV exposure apparatus according to an embodiment of the present invention.

  The EUV exposure apparatus includes an EUV light source 31, an illumination optical system 33, and a projection optical system 301, which will be described in detail later.

  The EUV light emitted from the EUV light source 31 becomes a substantially parallel light beam via a concave reflecting mirror 34 that acts as a collimator mirror, and enters an optical integrator 35 including a pair of fly-eye mirrors 35a and 35b.

  Thus, a substantial surface light source having a predetermined shape is formed in the vicinity of the reflective surface of the fly-eye mirror 35a, that is, in the vicinity of the exit surface of the optical integrator 35. The light from the substantial surface light source is deflected by the planar reflecting mirror 36 and then forms an elongated arc-shaped illumination area on the mask (reticle) M. Here, an aperture plate for forming an arcuate illumination region is not shown. The light reflected by the surface of the mask M is then reflected in turn by the multilayer reflectors M1, M2, M3, M4, M5, and M6 of the projection optical system 301 to form exposure light 1 on the surface of the mask M. An image of the pattern thus formed is formed on the wafer 2 (sensitive substrate) coated with the resist 3.

  FIG. 1 is a diagram showing a configuration of an EUV light source 31 according to an embodiment of the present invention. The EUV light source of this embodiment includes a nozzle 103 that supplies a liquid target, a linear member 101 that guides the liquid target to a laser focusing point P, a laser light source (not shown), a laser focusing lens 201, And a condensing mirror 203. The condensing mirror 203 is a multilayer film reflecting mirror.

  The liquid target is supplied to the linear member 101 by the nozzle 103 and guided to the laser condensing point P by the linear member 101. The laser light L from the laser light source is condensed at the laser condensing point P by the condenser lens 201, hits the target, and emits EUV light. The generated EUV light is condensed by the condenser mirror 203 and sent to the illumination optical system 33 of the exposure apparatus.

  Here, as shown in FIG. 1, the central axis of the nozzle 103 for supplying the target, the central axis of the laser beam, and the axis of the principal ray reflected by the condensing mirror 203 may be arranged so as to be orthogonal to each other. Good. By arranging in this way, interference with each other is prevented.

  FIG. 2 is a diagram illustrating a configuration of a target supply mechanism including the nozzle 103 and the linear member 101. When the liquid target LQ supplied from the tip of the nozzle 103 reaches the linear member 101, the liquid target LQ moves along the surface of the linear member 101 by surface tension and reaches the laser focusing point P. At the laser condensing point P, the liquid target LQ that has received the excitation laser light L becomes plasma and emits EUV light.

  By providing the linear member 101, the supply amount of the liquid target LQ can be easily managed. In order to manage the supply amount of the liquid target LQ, the liquid target LQ may be pressurized or rotated in the nozzle 103.

  FIG. 3 is a diagram illustrating an embodiment of the configuration of the nozzle 103 and the linear member 101. The tip of the linear member 101 enters the opening of the nozzle 103 and is configured to be held near the tip of the nozzle 103 by the periphery of the opening.

  FIG. 4 is a diagram illustrating another embodiment of the configuration of the nozzle 103 and the linear member 101. The tip of the linear member 101 is configured to be held near the tip of the nozzle 103 by a holding member 1031 connected to the nozzle 103.

  FIG. 5 is a diagram showing still another embodiment of the configuration of the nozzle 103 and the linear member 101. In the present embodiment, the linear member 101 is made of a metal having magnetism. By attaching the magnet 1033 to the tip of the nozzle 103, the tip of the linear member 101 is held near the tip of the nozzle 103.

  In general, the linear member 101 may be a wire made of steel, tungsten having a high melting point, or other metal.

  The cross section perpendicular to the longitudinal direction of the linear member may be circular or polygonal.

  FIG. 6 is a diagram showing another embodiment of the linear member. In the present embodiment, the linear member 1011 has a groove shape. The liquid target LQ travels in the groove. By providing the groove, it becomes easier to manage the amount of the liquid target LQ supplied from the tip of the nozzle 103.

  FIG. 7 is a view showing still another embodiment of the linear member. In the present embodiment, the linear member 1013 has a tubular shape with a hollow portion. The liquid target LQ is transmitted through the hollow portion. By providing the tube, it becomes easier to manage the amount of the liquid target LQ supplied from the tip of the nozzle 103. The linear member 1013 includes one or more openings OP for irradiating the excitation laser light L and diffusing EUV light.

Here, the liquid target LQ will be considered. Although the liquid target LQ is high in density, it is easy to suppress the amount of debris generated by controlling the supply amount. Even when the liquid target LQ becomes debris and adheres to the multilayer reflector, the reflectance decreases. Small materials, that is, materials with a low refractive index are preferred. One such material is H ₂ O.

Therefore, in the following, a case where H ₂ O is used as the liquid target LQ will be described as an example.

As the surface with H _{2 O} of the linear member 101 are distributed more quickly uniform, it may be enhanced wettability of the surface of the linear member 101. Specifically, the roughness of the surface of the linear member 101 is reduced, the surface of the linear member 101 is coated with a hydrophilic substance such as titanium oxide, or H ₂ O is linear. A substance that increases the hydrophilicity of the surface of the member 101 (for example, a surfactant) may be mixed.

The thickness of the linear member 101 is preferably about the same as the condensed diameter of the excitation laser light (several tens of micrometers to 100 micrometers) or several times as large. The thickness of the H ₂ O film transmitted through the linear member 101 is preferably as small as possible within a range that reliably exceeds the condensing diameter. If the amount of H ₂ O supplied to the linear member 101 is reduced while securing the amount necessary for light emission, the amount of excess H ₂ O that is not used to emit EUV light is reduced. The load of processing H ₂ O is reduced.

When H ₂ O is released from the tip of the nozzle 103 into the vacuum, it solidifies due to adiabatic expansion. In order to prevent solidification, as shown in FIG. 2, a temperature adjusting device 105 such as a heater is attached to the linear member 101, and the temperature of the linear member 101 is adjusted to, for example, a temperature near the boiling point of H ₂ O. May be.

By adjusting the temperature of the linear member 101, it is possible to evaporate excess H ₂ O that has not been used for light emission. By evaporating excess H ₂ O, the risk of solidified H ₂ O being sucked into the exhaust pump and damaging the exhaust pump is reduced.

Further, in order to recover excess H ₂ O that has not been used for light emission, a recovery mechanism 107 that guides H ₂ O from the linear member 101 to the recovery device is attached to the linear member 101 as shown in FIG. Also good. For example, the recovery mechanism 107 may be a wire.

By recovering the excess H _{2 O,} excess H _{2 O} can be prevented from being scattered in the EUV exposure apparatus as debris.

Although the case where H ₂ O is used as the liquid target LQ has been described, other substances can also be used. For example, a substance in which another substance (for example, the surfactant described above) is mixed in a H ₂ O solvent, a liquid organic solvent such as CH ₃ OH or C ₂ H ₅ OH, or a liquid such as Hg or Ga. Examples include pure metals or those containing impurities, liquid metal alloys such as Ga—In, Ga—In—Sn, Ga—In—Zn, Ga—Sn, and Ga—Zn, fluorinate, and similar inert liquids.

  Although the embodiment of the laser plasma light source has been described above, the present invention can also be applied to a discharge plasma light source. In the embodiment of the discharge plasma light source, the liquid target supplied from the nozzle is guided to the discharge space of the discharge plasma light source by a linear member.

  As described above, the EUV light source according to the present invention can suppress the influence of debris and generate strong EUV light. Moreover, the EUV exposure apparatus according to the present invention using the EUV light source according to the present invention can achieve high throughput.

  Hereinafter, an example of an embodiment of a semiconductor device manufacturing method according to the present invention will be described. FIG. 9 is a flowchart showing an example of the embodiment of the semiconductor device manufacturing method of the present invention. The manufacturing process of this example includes the following processes.

(1) Wafer manufacturing process for manufacturing a wafer (or wafer preparation process for preparing a wafer)
(2) Mask manufacturing process for manufacturing a mask to be used for exposure (or mask preparation process for preparing a mask)
(3) Wafer processing step for performing necessary exposure processing on the wafer (4) Chip assembly step for cutting out chips formed on the wafer one by one and making them operable (5) Chip inspection step for inspecting the completed chips Each process further includes several sub-processes.

  Among these main processes, the main process that has a decisive influence on the performance of the semiconductor device is the wafer processing process. In this step, designed circuit patterns are sequentially stacked on a wafer to form a large number of chips that operate as memories and MPUs. This wafer processing step includes the following steps.

(1) A thin film forming process for forming a dielectric thin film to be an insulating layer, a wiring portion, or a metal thin film for forming an electrode portion (using CVD or sputtering)
(2) Oxidation process for oxidizing the thin film layer and wafer substrate (3) Lithography process for forming a resist pattern using a mask (reticle) to selectively process the thin film layer and wafer substrate, etc. (4) Resist Etching process (for example, using dry etching technology) that processes thin film layers and substrates according to patterns
(5) Ion / impurity implantation diffusion process (6) Resist stripping process (7) Further inspection process for inspecting the processed wafer The wafer processing process is repeated for the required number of layers to manufacture a semiconductor device that operates as designed. To do.

  In the present embodiment, the EUV exposure apparatus according to the present invention including the EUV light source according to the present invention is used in the lithography process. Therefore, a semiconductor device can be manufactured with high throughput.

  According to the EUV light source according to the present embodiment, it becomes easy to supply a liquid target in an amount necessary for generating EUV light along the linear member. Therefore, the surplus amount of the target can be suppressed and the occurrence of debris can be suppressed.

  In the embodiment of the present invention, it is easier to manage the supply amount of the target by the groove of the linear member by providing the linear member at least partially with a groove through which the target moves.

  In the EUV light source according to the embodiment of the present invention, the supply amount of the target is managed by the hollow portion of the linear member by providing the linear member at least partially with a hollow portion in which the target moves. It becomes easier.

  The EUV light source according to the embodiment of the present invention further includes a temperature control device that controls the temperature of the linear member so as to control the temperature of the target, so that the liquid target is solidified and is contained in the EUV exposure apparatus. It can be prevented from spreading.

  The EUV light source according to the embodiment of the present invention further includes a mechanism for discharging the target from the linear member, so that the target is discharged from the linear member, so that excess target is scattered as debris in the EUV exposure apparatus. Can be prevented.

  The EUV light source according to the embodiment of the present invention includes a nozzle that supplies the target to the linear member, and thus can easily supply the target from the nozzle to the linear member.

  In the EUV light source according to the embodiment of the present invention, the nozzle includes a mechanism for holding the linear member in the vicinity of the nozzle, so that the target can be reliably supplied from the nozzle to the linear member in the vicinity thereof.

EUV light source according to an embodiment of the present invention, the target, although the H 2 _O or H _{2 O} is a solution as a solvent, the solution of H 2 _O or H _{2 O} and solvent, by managing the supply amount It is easy to suppress the amount of debris generated, and since the refractive index is low, even when it becomes debris and adheres to the multilayer film reflector, the decrease in the reflectance of the multilayer film mirror is small.

  According to the exposure apparatus according to the embodiment of the present invention, the influence of debris can be suppressed and strong EUV light can be generated, so that high throughput can be achieved.

  According to the method for manufacturing a semiconductor device according to the embodiment of the present invention, strong EUV light can be generated while suppressing the influence of debris, so that the semiconductor device can be manufactured with high throughput.

It is a figure which shows the structure of the EUV light source by one Embodiment of this invention. It is a figure which shows the structure of the target supply mechanism containing a nozzle and a linear member. It is a figure which shows one Embodiment of a structure with a nozzle and a linear member. It is a figure which shows other embodiment of a structure with a nozzle and a linear member. It is a figure which shows other embodiment of the structure of a nozzle and a linear member. It is a figure which shows other embodiment of a linear member. It is a figure which shows other embodiment of a linear member. It is a figure which shows the structure of the EUV exposure apparatus by one Embodiment of this invention. It is a flowchart which shows an example of embodiment of the semiconductor device manufacturing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Linear member, 103 ... Nozzle, 105 ... Temperature control apparatus, 107 ... Discharge mechanism, 201 ... Condensing lens, 203 ... Condensing mirror

Claims (15)

  An EUV light source that generates plasma from a target and emits EUV light generated from the plasma, includes a linear member, the target is in a liquid state, and the target is the linear member. An EUV light source configured to be supplied along the line.   The EUV light source according to claim 1, wherein the linear member includes a groove in which the target moves in at least a part thereof.   The EUV light source according to claim 1, wherein the linear member includes at least a hollow portion in which the target moves.   The EUV light source according to any one of claims 1 to 3, further comprising a temperature control device that controls the temperature of the linear member so as to control the temperature of the target.   The EUV light source according to any one of claims 1 to 4, further comprising a mechanism for discharging the target from the linear member.   The EUV light source according to any one of claims 1 to 5, further comprising a nozzle that supplies the target to the linear member.   The EUV light source according to claim 6, wherein the nozzle includes a mechanism for holding the linear member in the vicinity of the nozzle.   The EUV light source according to claim 1, wherein the linear member is a metallic wire. The EUV light source according to any one of claims 1 to 8, wherein the target is a solution containing H ₂ O or H ₂ O as a solvent.   The EUV light source according to any one of claims 1 to 8, wherein the target is a liquid organic solvent.   The EUV light source according to claim 1, wherein the target is a liquid metal.   The EUV light source according to claim 1, wherein the target is a liquid metal alloy.   The EUV light source according to claim 1, wherein the target is an inert liquid.   An EUV exposure apparatus that irradiates a mask with EUV light from an EUV light source via an illumination optical system, and exposes and transfers a pattern formed on the mask onto a sensitive substrate by a projection optical system, wherein the EUV light source is claimed. 14. An EUV exposure apparatus according to any one of items 1 to 13.   15. A method of manufacturing a semiconductor device, comprising: a step of exposing and transferring a pattern formed on a mask onto a sensitive substrate using the EUV exposure apparatus according to claim 14.

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