WO2004090957A1

WO2004090957A1 - Light source unit, illumination optical system, exposure apparatus and exposure method

Info

Publication number: WO2004090957A1
Application number: PCT/JP2004/005096
Authority: WO
Inventors: Hideki Komatsuda; Hiroyuki Kondo
Original assignee: Nikon Corporation
Priority date: 2003-04-09
Filing date: 2004-04-08
Publication date: 2004-10-21
Also published as: JP4340851B2; JP2004311814A

Abstract

A light source unit is disclosed which can focus DPP diverging light rays with a desired light intensity distribution by effectually suppressing loss of light quantity without being obstructed by structural bodies around the light-emitting point. The light source unit comprises a light source main body (11) wherein a target material is transformed into a plasma and an EUV light is emitted from the plasma, a first reflecting mirror (12a) having a through hole, and a second reflecting mirror (12b) which is arranged in the optical path between the light source main body and the first reflecting mirror and has a through hole. The light source unit focuses the EUV light on a certain point (12c) via the through hole of the second reflecting mirror, the reflective surface of the first reflecting mirror, the reflective surface of the second reflecting mirror and the through hole of the first reflecting mirror.

Description

Description Light source unit, illumination optical device, exposure apparatus and exposure method

The present invention relates to a light source unit, an illumination optical device, an exposure device, and an exposure method. More specifically, the present invention is suitable for an exposure apparatus used to manufacture a micro device such as a semiconductor device in a photolithography process using EUV light (extreme ultraviolet light) having a wavelength of about 5 to 50 nm. Related to a light source unit. Background art

In this type of exposure apparatus, further improvement in resolution is required as the circuit pattern to be transferred becomes finer, and shorter wavelength light is used as exposure light. In this specification, the term “light” refers not only to the narrow sense of light that can be seen by the naked eye, but also to the broad sense of light that includes wavelengths shorter than lmm among electromagnetic waves, including so-called infrared rays to X-rays. means. In recent years, an exposure apparatus using EUV (Extreme Ultraviolet) light having a wavelength of about 5 to 50 nm has been proposed as a next-generation apparatus (hereinafter referred to as “EU VL (Extreme Ultraviolet Lithography) exposure apparatus”). Have been.

At present, the following three types of light sources have been proposed as light sources that supply EUV light.

(1) Light source that supplies SR (synchrotron radiation)

(2) LPP (Laser Produced Plasma) light source that focuses laser light on the target and converts the target into plasma to obtain EUV light

(3) DPP (Discharge Produced Plasma) light source. When a voltage is applied between the electrodes in the presence of an electrode made of a target material or an overnight get material between the electrodes, a discharge occurs between the electrodes when a certain voltage is exceeded, and the target material is turned into plasma. This discharge causes a large current to flow between the electrodes, and the magnetic field generated by this current As a result, the plasma itself is compressed in the minute space and raises the plasma temperature. EUV light is emitted from this high-temperature plasma. A light source that supplies (excited) energy to plasma by discharge and emits EUV light is generally called a DPP light source.

In the above-described DPP light source and LPP light source, divergent light is emitted from a predetermined light emitting point, and debris (scattered particles) is also emitted with the emission of the divergent light. Hereinafter, the DPP light source and the LPP light source are collectively referred to as “plasma light source”. Therefore, it is necessary to once collect the divergent light supplied from the plasma light source, that is, the divergent plasma light, and block debris with a pinhole member arranged near the converging point. In the prior art, no structure has been proposed in which a structure around the light emitting point becomes an obstacle, and the loss of light quantity is suppressed favorably to collect the divergent light with a desired light intensity distribution.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and does not obstruct structures around a light-emitting point, suppresses light quantity loss, and collects DPP divergent light with a desired light intensity distribution. It is an object of the present invention to provide a light source unit that can be used.

Further, in the present invention, a mask pattern is formed on a photosensitive substrate by using EUV light supplied from a light source unit capable of concentrating DPP divergent light with a desired light intensity distribution while favorably suppressing a light quantity loss. An object of the present invention is to provide an exposure apparatus and an exposure method capable of transferring images with high fidelity and high throughput. Disclosure of the invention

In order to solve the above-mentioned problems, in a first embodiment of the present invention, a target material is turned into plasma, a light source body that emits EUV light from the plasma, a first reflecting mirror having a through-hole, A second reflector having a through-hole disposed in the optical path between the 1 reflector and

The EUV light is positioned at a predetermined position through the through-hole of the second reflecting mirror, the reflecting surface of the first reflecting mirror, the reflecting surface of the second reflecting mirror, and the through-hole of the first reflecting mirror. Provided is a light source unit characterized by focusing.

According to a preferred mode of the first mode, the first reflecting mirror has a concave reflecting surface You. In this case, it is preferable that the second reflecting mirror has a convex reflecting surface, a flat reflecting surface, or a concave reflecting surface. In the first embodiment, it is preferable that the through holes are formed at the center of the first reflecting mirror and the center of the second reflecting mirror, respectively.

According to a preferred mode of the first mode, the main body of the first reflecting mirror and the main body of the second reflecting mirror are formed of silicon, aluminum, or copper. Further, it is preferable that a cooling mechanism for cooling the first reflecting mirror and the second reflecting mirror is further provided. Further, it is preferable that the first reflecting mirror and the second reflecting mirror are configured to be exchangeable. Preferably, the apparatus further comprises a position measuring means for measuring the position of the reflecting surface of the first reflecting mirror and the position of the reflecting surface of the second reflecting mirror. Further, according to a preferred aspect of the first embodiment, a debris removing mechanism for removing debris emitted from the light source body in an optical path between the first reflecting mirror and the second reflecting mirror is provided. It also has more.

According to a second embodiment of the present invention, a light source body for plasmatizing a target material and emitting EUV light from the plasma, a first reflector having a through hole, and an optical path between the light source body and the first reflector With a second reflecting mirror arranged inside,

A debris removing mechanism for removing debris emitted from the light source main body in an optical path between the first reflecting mirror and the second reflecting mirror;

A light source unit that focuses the EUV light at a predetermined position via a reflecting surface of the first reflecting mirror, a reflecting surface of the second reflecting mirror, and a through hole of the first reflecting mirror. I will provide a.

According to a preferred mode of the first mode and the second mode, the debris removing mechanism has a casing for surrounding a space between the first reflecting mirror and the second reflecting mirror. In this case, it is preferable that a predetermined gas is introduced into the space. In this case, the predetermined gas is preferably helium, argon, neon, xenon, crypton, nitrogen, oxygen, or ozone. According to a preferred embodiment of the first and second embodiments, the debris removing mechanism includes a plurality of plate members having a cross section extending radially around the optical axis. In this case, the plurality It is preferable that the plate member and the casing are configured to be coolable. Further, it is preferable that a predetermined voltage is applied between the plurality of plate members and the casing. Further, it is preferable that the plurality of plate members are configured to be rotatable around the optical axis.

According to a third aspect of the present invention, there is provided a light source unit according to the first or second aspect, and a light guiding optical system for guiding EUV light from the light source unit to a surface to be irradiated. An illumination optical device is provided.

According to a fourth aspect of the present invention, there is provided an illumination optical device according to the third aspect for illuminating a reflective mask on which a predetermined pattern is formed, and a projection for forming a pattern image of the mask on a photosensitive substrate. An exposure apparatus comprising an optical system. In this case, it is preferable that the mask and the photosensitive substrate are moved relative to the projection optical system along a predetermined direction to project and expose the pattern of the mask onto the photosensitive substrate.

In a fifth aspect of the present invention, an illumination step of illuminating a reflective mask on which a predetermined pattern is formed using the illumination optical device of the third aspect, and exposing the pattern of the mask to the light through a projection optical system. And an exposure step of projecting and exposing on a reactive substrate. In this case, in the exposing step, it is preferable that the mask and the photosensitive substrate are relatively moved along the predetermined direction with respect to the projection optical system to project and expose the pattern of the mask onto the photosensitive substrate. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view schematically showing an overall configuration of an exposure apparatus having a light source unit according to an embodiment of the present invention.

FIG. 2 is a diagram showing a positional relationship between an arc-shaped exposure region (ie, an effective exposure region) formed on a wafer and an optical axis.

FIG. 3 is a diagram schematically showing an internal configuration of a light source unit and an illumination optical system of FIG.

FIG. 4 is a diagram schematically showing an internal configuration of a light source main body. FIG. 5 is a diagram schematically showing a configuration of a condensing optical system according to a numerical example of the present embodiment.

FIG. 6 is a diagram for explaining the inconvenience of a configuration in which DPP divergent light from a DPP light source body is simply condensed by one concave reflecting mirror.

FIG. 7 is a diagram for explaining the inconvenience of the configuration in which the divergent DPP light from the DPP light source body is collected by a nested oblique incidence mirror.

FIG. 8 is a diagram for explaining the inconvenience of the configuration in which the DPP divergent light from the DPP light source main body is condensed by the Schwarzschild optical system.

FIG. 9 is a diagram schematically showing an example of a cooling mechanism for cooling each reflecting mirror of the light collecting optical system.

FIG. 10 is a diagram schematically showing an example of a position measuring system for measuring the position of a reflecting surface of a reflecting mirror constituting a light collecting optical system.

FIG. 11A is a perspective view schematically showing an example of a debris removing mechanism for removing in a light path between a pair of reflecting mirrors constituting a light collecting optical system. FIG. 1 IB is a view schematically showing an example of a debris removing mechanism for removing in a light path between a pair of reflecting mirrors constituting a focusing optical system, and is a cross-sectional view along an optical axis. Is shown.

FIG. 12 is a diagram schematically showing an example in which the debris removing mechanism of the present embodiment is applied to a Schwarzschild condensing optical system.

FIG. 13 is a flowchart showing an example of a technique for obtaining a semiconductor device as a micro device. BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a view schematically showing an overall configuration of an exposure apparatus having a light source unit according to an embodiment of the present invention. FIG. 2 is a diagram showing a positional relationship between an arc-shaped exposure area (ie, an effective exposure area) formed on a wafer and an optical axis. In FIG. 1, along the optical axis direction of the projection optical system, that is, along the normal direction of the wafer serving as the photosensitive substrate. Thus, the Z axis is set in the plane of the wafer, the Y axis is set in a direction parallel to the plane of FIG. 1, and the X axis is set in the wafer plane in a direction perpendicular to the plane of FIG.

The exposure apparatus shown in FIG. 1 includes a DPP II type light source unit 1 for supplying exposure light. The EUV light supplied from the light source unit 1 is

(Not shown) and enters the illumination optical system 2. Here, the wavelength selection filter selectively transmits only EUV light near a predetermined wavelength (for example, 13.5 nm or 11.5 nm) from the EUV light supplied from the light source unit 1, It has the property of blocking transmission of wavelength light. The EUV light 3 transmitted through the wavelength selection filter passes through the illumination optical system 2 and the plane reflecting mirror 4 and is a reflective mask on which a pattern to be transferred is formed.

(Reticle) Light M.

The mask M is held by a mask stage 5 that can move in the Y direction so that the pattern surface extends along the XY plane. The movement of the mask stage 5 is configured to be measured by the laser interferometer 6. The illuminated light from the pattern of the mask M passes through a reflective projection optical system PL to form an image of the mask pattern on a wafer W as a photosensitive substrate. That is, on the wafer W, as shown in FIG. 2, for example, an elongated arc-shaped exposure region symmetrical with respect to the Y axis (that is, a static exposure region) is formed.

Referring to FIG. 2, in a circular area (image circle) IF having a radius (ΐ>) centered on the optical axis AX, the length in the X direction is LX so as to touch the image circle IF. An effective exposure area ER having an arc shape having a length of LY in the Y direction is set on the wafer W. The wafer W is arranged along the X direction and the Y direction so that the exposure surface extends along the XY plane. It is held by a dimensionally movable wafer stage 7. The movement of the wafer stage 7 is configured to be measured by a laser interferometer 8 as in the case of the mask stage 5.

Thus, scan exposure (scan exposure) is performed while moving the mask stage 5 and the wafer stage 7 along the Y direction, that is, while moving the mask M and the wafer W relative to the projection optical system PL along the Y direction. By doing so, the pattern of the mask M is transferred to one exposure area of the wafer W. Also, wafer stage By repeating scanning exposure while moving 7 two-dimensionally in the X and Y directions, the pattern of the mask に is sequentially transferred to each exposure area of the wafer W. FIG. 3 is a diagram schematically showing an internal configuration of a light source unit and an illumination optical system of FIG. FIG. 4 is a diagram schematically showing an internal configuration of the light source main body. Referring to FIG. 3, the light source unit 1 includes a light source body 11 for supplying DPP divergent light, and a condensing optical system 1 for condensing the DPP divergent light from the light source body 11 at a predetermined position. And two. As shown in FIG. 4, the light source body 11 applies a voltage between two electrodes 11 a and 11 b arranged at an interval and two electrodes 11 a and 11 b. And a power supply source 11 c for applying the power.

In the light source body 11, with the target material inserted between the power source electrode 11a and the anode electrode 11b, a voltage is applied from the power supply source 11c, and the second power source is applied. Discharge occurs between the one electrode 11a and the second electrode 11b as an anode, and the plasma generated by the discharge current is converged by electromagnetic force, resulting in a high-temperature, high-density plasma. EUV light is emitted from this plasma. Xenon (Xe) gas-tin (Sn) or the like is used as the target material.

On the other hand, as shown in Fig. 3, the condensing optical system 12 has, in order from the light source body 11 side, a convex reflecting mirror 12b having a through hole formed in the center, and a through hole formed in the center similarly. Provided with a concave reflecting mirror 12a. Here, the concave reflecting mirror 12a as the first reflecting mirror has a concave reflecting surface toward the light source body 11, and the convex reflecting mirror 12b as the second reflecting mirror is a concave reflecting mirror 1. It has a reflective surface that is convex toward 2a.

Thus, the DPP divergent light emitted from the light emitting point of the light source body 11 enters the concave reflecting mirror 12a via the through hole of the convex reflecting mirror 12b. The light reflected by the reflecting surface of the concave reflecting mirror 12a is reflected by the reflecting surface of the convex reflecting mirror 12b, and then passes through the through hole of the concave reflecting mirror 12a to a predetermined point 12c. Focus on

The EUV light from the light source unit 1 (1 1, 1 2) is focused once at the focal point 12 c, and then a pinhole member (not shown) placed near the focal point 12 c ). The EUV light that has passed through the pinhole member is converted into a substantially parallel light beam through the concave reflecting mirror 13, and is formed by a pair of fly-eye mirrors 14 a and 14 b. You will be led to Ntegre overnight. As the pair of fly-eye mirrors 14a and 14b, for example, a fly-eye mirror disclosed by the present applicant in Japanese Patent Application Laid-Open No. H11-3132638 can be used. For a more detailed configuration and operation of the fly-eye mirror, the related description in the publication can be referred to. In this way, a substantial surface light source having a predetermined shape is formed in the vicinity of the reflection surface of the second fly-eye mirror 14b, that is, in the vicinity of the emission surface of the optical integrator 14. The light from the substantial surface light source is deflected by the plane reflecting mirror 4 and forms an elongated arc-shaped illumination area on the mask M via a field stop (not shown). Light from the illuminated pattern of the mask M forms an image of the mask pattern on the wafer W via the projection optical system PL.

FIG. 5 is a diagram schematically showing a configuration of a condensing optical system according to a numerical example of the present embodiment. This numerical example shows an example of the light-converging optical system 12 whose aberration has been corrected relatively well. The following Table (1) lists the values of the specifications of the condensing optical system 12 according to the numerical example shown in FIG. In the main specifications in Table (1), λ is the wavelength of the exposure light (EUV light), Η is the light emission point (light emission area), the size of the lid (object height), and NA is the object side (light source unit side) aperture. Each represents a number. Also, in the optical component specifications in Table (1), the surface number is the order of the optical surfaces from the light source unit side, r is the radius of curvature (mm) of each optical surface, and d is the on-axis spacing of each optical surface. That is, the surface spacing (mm) is shown. It is assumed that the sign of the value of the surface distance d changes each time the light is reflected.

(table 1 )

(Main specifications)

λ = 1 3 .5 n m

H = — 1 mm to 10 mm

N A = 0.7

(Optical component specifications) Surface number rd Optical member

(Emission point) 300

1 -353.02832 -285 (Concave reflector 12a)

2 -429.74950 435 (Convex reflector 12b)

(Condensing point) As described above, in the conventional technology, the structure around the light emitting point 11d becomes an obstacle, and the light loss is suppressed well, and the DPP divergent light is condensed with the desired light intensity distribution. Has not been proposed. This will be briefly described with reference to FIGS. 6 to 8. FIG. 6 shows a configuration in which the DPP divergent light from the DPP light source main body 60 is simply condensed by one concave reflecting mirror 61. However, in the configuration shown in FIG. 6, a relatively large structure (not shown) for generating a discharge is provided around the pair of electrodes 60a and 60b. The light having received the light-condensing action is blocked by the structure before reaching the light-condensing point 62.

FIG. 7 shows a configuration in which DPP divergent light from a light emitting point 72 of a DPP light source main body (not shown) is condensed to a converging point 73 by an incident oblique incidence mirror 71. However, in the configuration shown in FIG. 7, a part of the light beam is blocked by the oblique incidence mirror 71 having a part of an ellipsoidal sphere having a focal point at the light emitting point 72 and the condensing point 73 and having a reflecting surface, so Since high-frequency undulations occur in the light intensity distribution of the received light beam, the uniformity of the illuminance on the wafer W is adversely affected.

FIG. 8 shows a configuration in which DPP divergent light from a light emitting point 80 of a DPP light source main body (not shown) is condensed to a converging point 82 by a Cyval schild optical system 81. However, in the configuration shown in FIG. 8, when the DPP diverging light from the DPP light source main body enters the concave reflecting mirror 81a of the Schwarzschild optical system 81, the central part of the light beam is focused on the convex reflecting mirror 81 of the Schwarsschild optical system 81. It is largely blocked by b. As a result, a very large light amount loss occurs in the Schwarzschild optical system 81, and the transmission efficiency becomes very poor.

On the other hand, in the present embodiment, the 0? Divergent light from the 0? Light source body 11 is convex. The light enters the concave reflecting mirror 12a through the central through hole of the surface reflecting mirror 12b. Then, the light reflected by the reflecting surface of the concave reflecting mirror 12a is reflected by the reflecting surface of the convex reflecting mirror 12b, and then passes through the central through-hole of the concave reflecting mirror 12a to a condensing point 12c. Reach. At this time, by making the light emitting point 11 d closer to the convex reflecting mirror 12 b and the concave reflecting mirror 12 a and the converging point 12 c to some extent, the central through hole of the convex reflecting mirror 12 b and the concave reflecting mirror 12 a The size of the central through-hole can be kept relatively small.

As a result, in the present embodiment, a small amount of light loss due to the central through-hole occurs at the time of reflection at the concave reflecting mirror 12a and at the time of reflection at the convex reflecting mirror 12b, but the pair of electrodes 11a and 11b The light flux is not blocked by the surrounding structure (not shown). The divergent light from the luminous source body 11 is composed of a concave reflecting mirror 12a and a convex reflecting mirror 12b along the optical axis AX, and is a relatively well-corrected condensing optic. Due to the light condensing effect of the system 12, it is possible to converge the DPP divergent light with a desired light intensity distribution without generating high-frequency undulations in the light intensity distribution of the light flux, and consequently the illuminance on the wafer W Uniformity can be ensured.

As described above, in the light source unit 1 (11, 12) of the present embodiment, the structure around the pair of electrodes 11a and 11b, that is, the structure around the light emitting point 11d becomes an obstacle. Without divergence, the DPP divergent light from the DPP light source main body 11 can be condensed at a predetermined converging point 12c with a desired light intensity distribution while suppressing the loss of light amount. Therefore, the exposure apparatus of the present embodiment uses EUV light 3 supplied from the light source unit 1 which can suppress the light quantity loss and collect the DPP divergent light with a desired light intensity distribution. The pattern of the mask M can be faithfully transferred onto the wafer W with high throughput.

In the above-described embodiment, the condensing optical system 12 for condensing the DPP divergent light from the DPP light source main body 11 includes a concave reflecting mirror 12a as a first reflecting mirror and a converging reflecting mirror 12a as a second reflecting mirror. It comprises a convex reflecting mirror 12b. However, without being limited to this, for example, a plane reflecting mirror or a concave reflecting mirror may be used as the second reflecting mirror. Further, in the present embodiment, the reflecting surfaces of the reflecting mirrors 12a and 12b are spherical. However, it is needless to say that the reflecting surfaces may be conical curves, aspheric surfaces, or free-form surfaces. In the above-described embodiment, a through-hole is formed at the center of each of the pair of reflecting mirrors constituting the condensing optical system 12. However, the present invention is not limited to this, and various modifications can be made to the formation position of the through hole of each reflecting mirror, similarly to the power arrangement of each reflecting mirror. Further, in the above-described embodiment, the DPP type light source is used as the EUV light source.

By the way, in the present embodiment, when the DPP divergent light is emitted from the DPP light source main body 11, not only debris is emitted but also heat is radiated. Therefore, the concave reflecting mirror 12a and the convex reflecting mirror 12b are not only affected by the irradiation heat of the DPP diverging light, but also have a value of 0? Radiation heat from the light source body 11 is also affected. Thus, in the present embodiment, the body of the concave reflecting mirror 12a and the material having high additivity and high thermal conductivity, such as silicon (Si), aluminum (A1), and copper (Cu), are used. Convex reflector

Preferably, a 12b body is formed. With this configuration, heat transmitted from the front surface (reflection surface) of each reflecting mirror can be quickly transmitted to the back surface, and the heat can be removed from each reflecting mirror by, for example, the action of an appropriate cooling mechanism.

FIG. 9 is a diagram schematically showing an example of a cooling mechanism for cooling each reflecting mirror of the condensing optical system. Referring to FIG. 9, heat pipes 20a and 20b are attached to the back surface of the concave reflecting mirror 12a and the back surface of the convex reflecting mirror 12b, respectively, which constitute the condensing optical system 12 so as to be in close contact with each other. ing. Thus, heat pipes 20a and 2

By the action of 0b, heat can be radiated from the concave reflecting mirror 12a and the convex reflecting mirror 12b to the outside. However, the cooling mechanism applicable to each of the reflecting mirrors 12a and 12b of the condensing optical system 12 is not limited to the configuration example of FIG.

It is also possible to adopt a structure that allows a cooling liquid (such as cold water) to pass through the inside of the body of 12b.

Further, in the present embodiment, the concave reflecting mirror 12a and the convex reflecting mirror 12b constituting the condensing optical system 12 control the influence of the radiant heat from the DPP light source main body 11 and the influence of the irradiation heat of the DPP divergent light. Therefore, it is preferable to be configured to be exchangeable. In particular, the concave reflecting mirror 12a, whose reflecting surface is directly exposed to the DPP light source Since it is expected that replacement will be required frequently, it is desirable that the configuration be easily replaceable.

In order to realize easy replacement of the concave reflecting mirror 12a and the convex reflecting mirror 12b constituting the focusing optical system 12, the position of the reflecting surface of the concave reflecting mirror 12a and the convex reflecting mirror 12b It is preferable to include a position measuring means for measuring the position of the reflecting surface. FIG. 10 is a diagram schematically showing an example of a position measuring system for measuring the position of a reflecting surface of a reflecting mirror constituting a light collecting optical system. In the position measurement system shown in Fig. 10, light from the mask 21a, 21b, 21c is transmitted to the front group 22a, 22b, 22c of the imaging optical system, and the concave reflector 12a. A mask pattern is formed on the screen (or CCD) 24a, 24b, 24c via the reflecting surface of the above and the rear group 23a, 23b, 23c of the imaging optical system.

Thus, based on the two-dimensional position information of the mask panel formed on each of the screens 24a, 24b, and 24c, a new concave reflector 12a is replaced when the concave reflector 12a is replaced. Positioning can be performed with high accuracy. At this time, it is preferable to configure the position measurement system (21 to 24) so as to detect a change in reflectance on the reflecting surface of the concave reflecting mirror 12a. With this configuration, it is possible to more accurately detect the degree of dirt on the reflecting surface of the concave reflecting mirror 12a (deterioration of the optical characteristics) caused by debris, and, consequently, to appropriately control the concave reflecting mirror 12a. They can be exchanged at the right time.

Also, when replacing the convex reflecting mirror 12b, a new convex reflecting mirror 12b is positioned with high accuracy using the position measurement system (21-24) having the same configuration as that of Fig. 10. Or the degree of dirt on the reflecting surface of the convex reflecting mirror 12b can be detected. The configuration of the measuring system for measuring the position of the reflecting surface of each reflecting mirror and detecting the degree of contamination of the reflecting surface is not limited to the configuration example shown in FIG. It is possible.

Further, as described above, when debris emitted upon emission of DPP divergent light from the DPP light source main body 11 adheres to the reflecting surfaces of the concave reflecting mirror 12a and the convex reflecting mirror 12b, the concave surface Poor reflection characteristics (optical characteristics) of reflector 12a and convex reflector 12b And the replacement frequency increases. Therefore, in the present embodiment, the debris emitted from the DPP light source body 11 is placed in an optical path between the concave reflecting mirror 12a (first reflecting mirror) and the convex reflecting mirror 12b (second reflecting mirror). It is preferable to have a debris removal mechanism for removal.

FIGS. 11A and 11B are diagrams schematically showing an example of a debris removing mechanism for removing in a light path between a pair of reflecting mirrors constituting a condensing optical system. FIG. A shows a perspective view, and FIG. 11B shows a cross-sectional view along the optical axis. Referring to FIGS. 11A and 11B, the debris removing mechanism has a cylindrical casing 25 for surrounding the space between the concave reflecting mirror 12a and the convex reflecting mirror 12b. However, a small amount of a predetermined gas having a relatively high transmittance for EUV light is introduced into this space through the gas inlet 25a.

The casing 25 is formed of a metal such as stainless steel, copper, or aluminum, and is connected to the ground potential. As introducible predetermined gas, for example, such as helium (He), argon (Ar), neon (N e), xenon (Xe), krypton (Kr), nitrogen (N _2), oxygen (0 _2), ozone ( 0 ₃ ) can be used. In addition, the debris removing mechanism includes a plurality of plate members 26 having a cross section extending radially around the optical axis AX.

The plurality of plate members 26 are formed of, for example, a metal such as stainless steel, copper, or aluminum, and are configured such that a positive potential (about several tens of volts to several kV) is applied by a power supply. In other words, a predetermined voltage is set between the plurality of plate members 26 and the casing 25. Further, the plurality of plate members 26 are configured to be integrally rotatable about the optical axis AX. Furthermore, the casing 25 and the plurality of plate members 26 are configured to be able to be cooled by a suitable cooling mechanism (not shown).

In the debris removal mechanism shown in FIGS. 11A and 11B, a part of the debris released from the plasma enters the interior space of the casing 25, but is introduced into the casing 25. Rapidly loses its kinetic energy due to collisions with the gas molecules, and floats in the interior space of the casing 25 with almost the same kinetic energy as the gas molecules. Become like The EUV light radiated from the plasma directly ionizes the floating debris or ionizes debris by collision with ionized gas molecules (atoms).

When debris is ionized negatively, the debris is attracted to a plurality of plate members 26 to which a positive potential is applied, and adheres and deposits. As a result, it is possible to reduce the adhesion of debris to the reflecting surface of the concave reflecting mirror 12a and the reflecting surface of the convex reflecting mirror 12b, and, consequently, to reduce the deterioration of the reflection characteristics and the frequency of replacement of the reflecting mirror. it can. At this time, by connecting the multilayer reflecting film coated on the surface of each of the reflecting mirrors 12a and 12b to the ground potential, the adhesion of debris to the reflecting surface can be more effectively reduced.

On the other hand, when the debris is ionized to a positive value, it adheres and deposits on the inner surface of the casing 25 connected to the ground potential. At this time, the same potential as or higher than that of the plurality of plate members 26 is applied to the multilayer reflective film coated on the surface of each of the reflecting mirrors 12a and 12b, so that the reflecting surface Adhesion and deposition of debris on the surface can be prevented. Also, an easily peelable sheet (an insulating material such as paper, resin, or ceramics, or a metal foil such as aluminum or copper) may be attached to the inner surface of the casing 25, and debris may be attached and deposited on the sheet. . In this case, it is possible to easily return to a clean environment simply by changing the sheet after waiting for a large amount of debris to adhere to the sheet.

If the EUV light from the plasma alone cannot sufficiently deionize the debris, the inside of the casing 25 is opened through an opening (or a light transmitting part) formed in a part of the casing 25. UV light may be introduced into the device, and the action of the UV light may be used to promote ionization of debris. In this case, a mercury lamp, an excimer lamp, an excimer laser, or the like can be used as a light source for supplying ultraviolet light. Alternatively, debris may be ionized by introducing an electron beam from the electron source into the casing 25.

When the debris removing mechanism shown in FIGS. 11A and 11B is used, in order to uniformize the light intensity distribution of the light beam emitted from the condensing optical system 12 during exposure, Preferably, the plurality of plate members 26 are integrally rotated around the optical axis AX. Further, in the configuration examples shown in FIGS. 11A and 11B, a positive potential is applied to the plurality of plate members 26, but the invention is not limited thereto, and a negative potential is applied to the plurality of plate members 26. It may be applied. The potential to be applied may be DC or AC. Furthermore, when an AC potential is applied, various aspects of the frequency are possible.

The debris removal mechanism is not limited to a condensing optical system with a through-hole in the second reflecting mirror as shown in Figs. 11A and 11B, but also to a second reflecting mirror like a Schwarzschild optical system. It can also be used for an optical system having no through hole. FIG. 12 is a diagram schematically showing an example in which the debris removing mechanism of the present embodiment is applied to a Schwarzschild condensing optical system. Referring to FIG. 12, an EUV light source 43 by a DPF (Dense Plasma Focus) method is arranged inside a vacuum vessel 41. The vacuum container 41 is evacuated to a vacuum (eg, 0.1 lTorr or less) by an exhaust device (not shown).

In the EUV light source 43, EUV light 45 is emitted from plasma 44 generated near the electrode. The emitted EUV light 45 is reflected by a concave reflecting mirror (first reflecting mirror) 46 coated with a Mo / Si multilayer film, and a convex reflecting mirror (second reflecting mirror) similarly coated with a Mo / Si multilayer film. After being reflected at 47, it is condensed on the pinhole 52 and guided to the subsequent optical system. The multilayer film coated on the concave reflecting mirror 46 and the convex reflecting mirror 47 is formed so as to have a peak in reflectance with respect to light having a wavelength of 13.5 nm. In other words, EUV light guided to the subsequent optical system after passing through the pinhole 52 is only light having a wavelength near 13.5 nm.

The concave reflecting mirror 46 and the convex reflecting mirror 47 are fixed in a casing 48. A gas introduction port 49 is attached to the casing 48, and He gas is introduced from the port 49 into the casing 48. In the casing 48, between the concave reflecting mirror 46 and the convex reflecting mirror 47, a plurality of aluminum blades 50 are attached so as to be parallel to the optical path. The wing 50 is configured to be rotatable about the optical axis. The rotation of the wings 50 is performed by an ultrasonic motor or an electric motor. The casing 48 is attached to the wall of the vacuum vessel 41. A vacuum vessel 42 is provided next to the vacuum vessel 41, and the vacuum vessels 41 and 42 communicate with each other only through an opening through which EUV light passes. The vacuum container 42 is evacuated separately from the vacuum container 41 by a vacuum exhaust device (not shown). By adopting such a configuration, differential evacuation can be performed between the vacuum vessels 41 and 42, and thus, deterioration of the degree of vacuum downstream of the pinhole 52 can be reduced. Can be.

The debris that has entered the casing 48 is collided and scattered by the He gas introduced from the port 49, rapidly loses its energy, and floats inside the casing 48. The debris floating in the casing 48 collides with the inner wall of the blade 50 5 casing 48 and is adsorbed. As a result, the amount of debris adhering and accumulating on the concave reflecting mirror 46 and the convex reflecting mirror 47 is greatly reduced, and a decrease in the reflectance of each reflecting mirror can be suppressed.

If the cylindrical member 51 is arranged near the EUV light beam in the vacuum container 42, debris that has entered the vacuum container 42 collides with the inner wall of the cylindrical member 51 and is adsorbed. It is possible to reduce the inflow of debris downstream of 52. Cooling the casing 48, the wings 50, and the tubular member 51 is preferable because the probability that the adsorbed debris is re-emitted is reduced, and the adsorption efficiency is further increased. As the cooling method, cooling with a refrigerant (a liquid such as water), electronic cooling of a Peltier element, or cooling with a heat pipe may be used. If the degree of vacuum downstream of the pinhole 52 is better without the tubular member 51, the installation of the tubular member 51 may be omitted. In the exposure apparatus according to the above-described embodiment, the mask is illuminated by the illumination system (illumination step), and a transfer pattern formed on the mask is exposed on the photosensitive substrate using the projection optical system (exposure step). And micro devices (semiconductor devices, imaging devices, liquid crystal display devices, thin-film magnetic heads, etc.). Hereinafter, a predetermined circuit pattern is formed on a wafer or the like as a photosensitive substrate using the exposure apparatus of the present embodiment. Thus, an example of a method for obtaining a semiconductor device as a micro device will be described with reference to the flowchart in FIG.

First, in step 301 of FIG. 13, a metal film is deposited on one lot of wafers. In the next step 302, a photoresist is applied on the metal film on the wafer of the lot. Then, in step 303, using the exposure apparatus of this embodiment, the pattern image on the mask (reticle) is sequentially exposed to each shot area on the wafer of the lot through the projection optical system. Transcribed.

Then, in step 304, the photoresist on the lot in the lot is developed, and in step 305, etching is performed on the wafer in the lot using the resist pattern as a mask. Thereby, a circuit pattern corresponding to the pattern on the mask is formed in each shot area on each wafer. Thereafter, a device such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer and the like. According to the above-described semiconductor device manufacturing method, a semiconductor device having an extremely fine circuit pattern can be obtained with good throughput. Industrial potential

As described above, the light source unit of the present invention is arranged in a light source body for supplying EUV light, a first reflecting mirror having a through hole, and an optical path between the light source body and the first reflecting mirror. And a second reflecting mirror having a through hole. As a result, the DPP divergent light from the DPP light source body is condensed to a predetermined light condensing point with a desired light intensity distribution while suppressing the loss of light amount without causing any obstacles around the light emitting point be able to. Therefore, in the exposure apparatus and the exposure method of the present invention, the mask pattern is formed by using EUV light supplied from a light source unit capable of condensing DPP divergent light with a desired light intensity distribution while favorably suppressing a light amount loss. Can be faithfully transferred onto a photosensitive substrate with high throughput, and a high-precision microdevice can be manufactured with high throughput.

Claims

The scope of the claims

1. A target material is turned into plasma, a light source body that emits EUV light from the plasma, a first reflector having a through-hole, and arranged in an optical path between the light source body and the first reflector. A second reflector having a through hole,

The EUV light is collected at a predetermined position through the through hole of the second reflecting mirror, the reflecting surface of the first reflecting mirror, the reflecting surface of the second reflecting mirror, and the through hole of the first reflecting mirror. A light source unit that emits light.

2. In the light source unit according to claim 1,

The light source unit, wherein the first reflecting mirror has a concave reflecting surface.

3. In the light source unit according to claim 2,

The light source unit, wherein the second reflecting mirror has a convex reflecting surface.

4. In the light source unit according to claim 2,

The light source unit, wherein the second reflecting mirror has a flat reflecting surface.

5. In the light source unit according to claim 2,

The light source unit, wherein the second reflecting mirror has a concave reflecting surface.

6. The light source unit according to any one of claims 1 to 5,

The light source unit, wherein the through hole is formed at a center of the first reflecting mirror and at a center of the second reflecting mirror, respectively.

7. The light source unit according to any one of claims 1 to 6, wherein: The light source unit, wherein the main body of the first reflecting mirror and the main body of the second reflecting mirror are formed of silicon, aluminum, or copper.

8. The light source unit according to any one of claims 1 to 7,

A light source unit further comprising a cooling mechanism for cooling the first reflecting mirror and the second reflecting mirror.

9. In the light source unit according to any one of claims 1 to 8,

The light source unit, wherein the first reflecting mirror and the second reflecting mirror are exchangeable.

10. The light source unit according to any one of claims 1 to 9, wherein

A light source unit further comprising a position measuring means for measuring a position of a reflecting surface of the first reflecting mirror and a position of a reflecting surface of the second reflecting mirror.

11. The light source unit according to any one of claims 1 to 10, wherein:

A light source unit, further comprising: a debris removing mechanism for removing debris emitted from the light source body in an optical path between the first reflecting mirror and the second reflecting mirror.

12. A light source body that converts the target material into plasma and emits EUV light from the plasma, a first reflector having a through-hole, and is disposed in an optical path between the light source body and the first reflector. With a second reflector,

Debris emitted from the light source body is interposed between the first reflecting mirror and the second reflecting mirror. Further comprising a debris removal mechanism for removal in the optical path of

A light source unit that focuses the EUV light at a predetermined position via a reflecting surface of the first reflecting mirror, a reflecting surface of the second reflecting mirror, and a through hole of the first reflecting mirror. .

13. The light source unit according to claim 11 or 12, wherein the debris removing mechanism includes a casing for surrounding a space between the first reflecting mirror and the second reflecting mirror. A light source unit comprising:

14. The light source unit according to claim 13, wherein:

A light source unit, wherein a predetermined gas is introduced into the space.

15. The light source unit according to claim 14, wherein:

The light source unit, wherein the predetermined gas is helium, argon, neon, xenon, krypton, nitrogen, oxygen or ozone.

16. The light source unit according to any one of claims 11 to 15, wherein

The light source unit according to claim 1, wherein the debris removing mechanism includes a plurality of plate members having a cross section extending radially around an optical axis.

17. The light source unit according to any one of claims 12 to 16, wherein

The light source unit, wherein the plurality of plate members and the casing are configured to be coolable.

18. The light source unit according to claim 16 or 17, wherein a predetermined voltage is applied between the plurality of plate members and the casing. A light source unit.

19. The light source unit according to any one of claims 16 to 18, wherein

The light source unit, wherein the plurality of plate members are configured to be rotatable about the optical axis.

20. The light source unit according to any one of claims 1 to 19, and a light guide optical system for guiding EUV light from the light source unit to a surface to be irradiated. An illumination optical device, comprising:

21. An illumination optical device according to claim 20 for illuminating a reflective mask on which a predetermined pattern is formed, and an illumination optical device for forming a pattern image of the mask on a photosensitive substrate. An exposure apparatus comprising a projection optical system.

22. In the exposure apparatus according to claim 21,

An exposure apparatus, wherein the mask and the photosensitive substrate are relatively moved with respect to the projection optical system along a predetermined direction to project and expose a pattern of the mask onto the photosensitive substrate.

23. An illuminating step of illuminating a reflective mask on which a predetermined pattern has been formed using the illumination optical device according to claim 20; and the patterning of the mask through a projection optical system. An exposure step of projecting and exposing on a photosensitive substrate.

24. In the exposure method according to claim 23,

In the exposing step, the mask and the photosensitive substrate are moved relative to the projection optical system along a predetermined direction to project the pattern of the mask onto the photosensitive substrate. An exposing method characterized by exposing.