JP4725814B2 - Light source unit, illumination optical device, exposure apparatus, and exposure method - Google Patents

Description

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

  In this type of exposure apparatus, further improvement in resolving power is required as the circuit pattern to be transferred becomes finer, and light having a shorter wavelength is used as exposure light. In addition, “light” in this specification means not only “light” in a narrow sense that can be seen with eyes, but also “light” in a broad sense including a so-called infrared ray to X-ray having a wavelength shorter than 1 mm among electromagnetic waves. To do. In recent years, an exposure apparatus using EUV (Extreme UltraViolet) light having a wavelength of about 5 to 50 nm (hereinafter referred to as “EUVL (Extreme UltraViolet Lithography) exposure apparatus”) has been proposed as a next-generation apparatus.

Currently, the following three types of light sources have been proposed as light sources for supplying EUV light.
(1) Light source for supplying SR (synchrotron radiation) (2) LPP (Laser Produced Plasma) light source for collecting EUV light by condensing laser light on the target and converting the target into plasma (3) DPP (Discharge Produced) Plasma) light source. When a voltage is applied between electrodes in the state where an electrode made of the target material or the target material exists 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 plasma itself is compressed into a minute space by the magnetic field generated by this current, raising the plasma temperature. EUV light is emitted from this high temperature plasma. A light source that supplies (excites) 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) are also emitted as the divergent light is emitted. 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 plasma divergent light, and block the debris by a pinhole member arranged in the vicinity of the condensing point. In the prior art, a structure for concentrating plasma divergent light with a desired light intensity distribution while suppressing a loss of light quantity satisfactorily due to a structure around the light emitting point is not proposed.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a light source unit capable of condensing DPP divergent light while reducing the adhesion of debris to a reflecting surface. In the present invention, the EUV light supplied from the light source unit capable of condensing the DPP divergent light while reducing the adhesion of debris to the reflecting surface is used to faithfully and mask the mask pattern on the photosensitive substrate. An object of the present invention is to provide an exposure apparatus and an exposure method capable of transferring at a high throughput.

In order to solve the above problems, in the first embodiment of the present invention, a target material is converted into plasma, and a light source body that emits EUV light from the plasma, a first reflecting mirror having a through hole, the light source body, and the first A second reflecting mirror disposed in the optical path between the first reflecting mirror,
A debris removal mechanism for removing debris emitted from the light source body in an optical path between the first reflecting mirror and the second reflecting mirror;
The EUV light is condensed at a predetermined position through 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 second aspect of the present invention, there is provided an illumination optical apparatus comprising: the light source unit of the first aspect; and a light guide optical system for guiding EUV light from the light source unit to an irradiated surface. To do.

  In the third embodiment of the present invention, the illumination optical apparatus of the second embodiment for illuminating a reflective mask on which a predetermined pattern is formed, and projection optics for forming a pattern image of the mask on a photosensitive substrate. An exposure apparatus is provided.

  In the fourth embodiment of the present invention, an illumination process of illuminating a reflective mask on which a predetermined pattern is formed using the illumination optical apparatus of the second embodiment, and the pattern of the mask is exposed to the photosensitive via a projection optical system. And an exposure step of performing projection exposure onto a substrate.

  A light source unit of the present invention includes a light source body for supplying EUV light, a first reflecting mirror having a through hole, and a second reflecting mirror disposed in an optical path between the light source body and the first reflecting mirror. And a debris removing mechanism. The debris removing mechanism removes debris emitted from the light source body in the optical path between the first reflecting mirror and the second reflecting mirror. As a result, DPP diverging light from the DPP light source body can be condensed at a predetermined position while reducing the adhesion of debris to the reflecting surface.

  Therefore, in the exposure apparatus and exposure method of the present invention, the mask pattern is made photosensitive by using EUV light supplied from a light source unit capable of condensing DPP diverging light while reducing debris adhesion to the reflecting surface. Transfer can be performed faithfully and with high throughput on the substrate, and as a result, a highly accurate microdevice can be manufactured with high throughput.

  Embodiments 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 including a light source unit according to an embodiment of the present invention. FIG. 2 is a diagram showing the positional relationship between the arc-shaped exposure area (that is, the effective exposure area) formed on the wafer and the optical axis. In FIG. 1, the Z axis along the optical axis direction of the projection optical system, that is, the normal direction of the wafer as the photosensitive substrate, the Y axis in the direction parallel to the paper surface of FIG. The X axis is set in the direction perpendicular to the paper surface of FIG.

  The exposure apparatus of FIG. 1 includes a DPP type light source unit 1 for supplying exposure light. The EUV light supplied from the light source unit 1 enters the illumination optical system 2 via a wavelength selection filter (not shown). Here, the wavelength selection filter selectively transmits only EUV light in the vicinity of a predetermined wavelength (for example, 13.5 nm or 11.5 nm) from the EUV light supplied by the light source unit 1 and blocks transmission of other wavelength light. Has characteristics. The EUV light 3 transmitted through the wavelength selection filter illuminates a reflective mask (reticle) M on which a pattern to be transferred is formed via the illumination optical system 2 and the plane reflecting mirror 4.

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

  Referring to FIG. 2, in a circular area (image circle) IF having a radius φ centered on the optical axis AX, the length in the X direction is LX and the length in the Y direction so as to contact the image circle IF. An arc-shaped effective exposure region ER with LY is set. The wafer W is held by a wafer stage 7 that can move two-dimensionally along the X and Y directions so that the exposure surface extends along the XY plane. The movement of the wafer stage 7 is measured by a laser interferometer 8 as in the mask stage 5.

  Thus, the scanning exposure (scanning exposure) is performed while moving the mask stage 5 and the wafer stage 7 along the Y direction, that is, while relatively moving the mask M and the wafer W along the Y direction with respect to the projection optical system PL. As a result, the pattern of the mask M is transferred to one exposure region of the wafer W. In addition, the pattern of the mask M is sequentially transferred to each exposure region of the wafer W by repeating scanning exposure while moving the wafer stage 7 two-dimensionally along the X direction and the Y direction.

  FIG. 3 is a diagram schematically showing the internal configuration of the light source unit and illumination optical system of FIG. FIG. 4 is a diagram schematically showing the internal configuration of the light source body. Referring to FIG. 3, the light source unit 1 includes a light source body 11 for supplying DPP diverging light and a condensing optical system 12 for condensing the DPP diverging light from the light source main body 11 at a predetermined position. ing. As shown in FIG. 4, the light source body 11 includes two electrodes 11 a and 11 b arranged at a distance, and a power supply source 11 c for applying a voltage between the two electrodes 11 a and 11 b. ing.

  In the light source body 11, the first electrode 11a as the cathode and the second electrode as the anode are received by applying a voltage from the power supply source 11c with the target material placed between the cathode electrode 11a and the anode electrode 11b. A discharge occurs between the discharge current 11b and the plasma generated by the discharge current is converged by an electromagnetic force to be a high-density plasma at a high temperature. EUV light is emitted from this plasma. As the target material, xenon (Xe) gas, tin (Sn), or the like is used.

  On the other hand, as shown in FIG. 3, the condensing optical system 12 includes, in order from the light source body 11 side, a convex reflecting mirror 12b having a through hole at the center and a concave reflecting mirror 12a having a through hole at the center. And. 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 convex toward the concave reflecting mirror 12a. Has a reflective surface.

  In this way, the DPP divergent light emitted from the light emitting point of the light source body 11 enters the concave reflecting mirror 12a through 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 condensed at a predetermined point 12c through the through hole of the concave reflecting mirror 12a.

  The EUV light from the light source unit 1 (11, 12) is once condensed at the condensing point 12c and then incident on a pinhole member (not shown) disposed in the vicinity of the condensing point 12c. The EUV light that has passed through the pinhole member becomes a substantially parallel light beam through the concave reflecting mirror 13, and is guided to the optical integrator 14 including a pair of fly-eye mirrors 14a and 14b. 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. 11-312638 can be used. For more detailed configuration and operation of the fly-eye mirror, reference can be made to related descriptions in the publication.

  Thus, a substantial surface light source having a predetermined shape is formed in the vicinity of the reflecting surface of the second fly's eye mirror 14b, that is, in the vicinity of the exit surface of the optical integrator 14. Light from a substantial surface light source is deflected by the plane reflecting mirror 4 and then 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 condensing optical system 12 with aberrations 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 of Table (1), λ is the wavelength of the exposure light (EUV light), H is the size of the light emitting point (light emitting area) 11d (object height), and NA is the object side (light source unit side) aperture. Each represents a number. Also, in the optical member specifications of 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 axial spacing of each optical surface, The surface spacing (mm) is shown. Note that the value of the surface interval d changes in sign each time it is reflected.

(Table 1)
(Main specifications)
λ = 13.5nm
H = -1mm to + 1mm
NA = 0.7

(Optical member specifications)
Surface number rd Optical member
(Light emission point) 300
1 -353.02832 -285 (concave reflector 12a)
2 -429.74950 435 (convex reflector 12b)
(Condensing point)

  As described above, in the related art, a structure around the light emitting point 11d becomes an obstacle, and a configuration for condensing DPP divergent light with a desired light intensity distribution while suppressing light loss is not proposed. This point will be briefly described with reference to FIGS. FIG. 6 shows a configuration in which DPP diverging light from the DPP light source body 60 is simply collected by one concave reflecting mirror 61. However, in the configuration shown in FIG. 6, since a relatively large structure (not shown) for generating discharge is provided around the pair of electrodes 60a and 60b, the concave reflecting mirror 61 receives the light collecting action. The light is blocked by the structure before reaching the 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 at a condensing point 73 by a nested 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 elliptical spherical surface with the light emitting point 72 and the condensing point 73 as a focal point, and receives a condensing action. High-frequency undulation occurs in the light intensity distribution of the luminous flux, which adversely affects the illuminance uniformity on the wafer W.

  FIG. 8 shows a configuration in which DPP divergent light from a light emitting point 80 of a DPP light source body (not shown) is condensed on a condensing point 82 by a Schwarzschild optical system 81. However, in the configuration shown in FIG. 8, when the DPP divergent light from the DPP light source body enters the concave reflecting mirror 81 a of the Schwarzschild optical system 81, the central portion of the light beam is caused by the convex reflecting mirror 81 b of the Schwarzschild optical system 81. Largely blocked. As a result, a very large light quantity loss occurs in the Schwarzschild optical system 81, and the transmission efficiency becomes very poor.

  On the other hand, in this embodiment, the DPP divergent light from the DPP light source body 11 enters the concave reflecting mirror 12a through the central through hole of the convex reflecting mirror 12b. Then, after 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, it reaches the condensing point 12c through the central through hole of the concave reflecting mirror 12a. At this time, by making the light emitting point 11d, the convex reflecting mirror 12b, the concave reflecting mirror 12a, and the condensing point 12c close to some extent, the sizes of the central through hole of the convex reflecting mirror 12b and the central through hole of the concave reflecting mirror 12a are relatively small. Can be kept small.

  As a result, in the present embodiment, there is a slight loss of light amount due to the central through hole upon reflection at the concave reflecting mirror 12a and reflection at the convex reflecting mirror 12b, but structures around the pair of electrodes 11a and 11b. The light beam is not blocked by (not shown). Further, the DPP divergent light from the DPP light source main body 11 is subjected to the condensing action of the condensing optical system 12 which is composed of the concave reflecting mirror 12a and the convex reflecting mirror 12b along the optical axis AX and whose aberration is corrected relatively well. Therefore, the DPP divergent light can be collected with a desired light intensity distribution without causing high-frequency undulations in the light intensity distribution of the luminous flux, and as a result, the illuminance uniformity on the wafer W 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 does not become an obstacle, and the DPP light source body 11 The DPP diverging light from the light can be condensed at a predetermined condensing point 12c with a desired light intensity distribution while suppressing a loss of light amount. Therefore, in the exposure apparatus of the present embodiment, the EUV light 3 supplied from the light source unit 1 that can condense the DPP divergent light with a desired light intensity distribution while suppressing the loss of light quantity is used. The pattern can be transferred onto the wafer W faithfully and with high throughput.

  In the above-described embodiment, the condensing optical system 12 for condensing the DPP divergent light from the DPP light source body 11 includes the concave reflecting mirror 12a as the first reflecting mirror and the convex reflecting mirror as the second reflecting mirror. 12b. However, the present invention is not limited to this, and for example, a plane reflecting mirror or a concave reflecting mirror can be used as the second reflecting mirror. Further, in the present embodiment, the reflecting surfaces of the reflecting mirrors 12a and 12b are spherical surfaces, but it goes without saying that they may be conical curves, aspherical surfaces, and free-form surfaces.

  In the above-described embodiment, a through hole is formed in the center 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 with respect to the formation positions of the through holes of the respective reflecting mirrors as in the power arrangement of the respective reflecting mirrors. In the above-described embodiment, a DPP type light source is used as the EUV light source. However, the present invention is not limited to this, and an LPP type light source can also be used.

  By the way, in this embodiment, not only debris but also heat is radiated when the DPP divergent light is emitted from the DPP light source body 11. Therefore, the concave reflecting mirror 12a and the convex reflecting mirror 12b are not only influenced by the irradiation heat of the DPP diverging light but also influenced by the radiant heat from the DPP light source body 11. Therefore, in this embodiment, the main body of the concave reflecting mirror 12a and the convex reflecting mirror 12b are made of a material having high workability and high thermal conductivity, that is, silicon (Si), aluminum (Al), copper (Cu), or the like. It is preferable to form a main body. With this configuration, heat transmitted from the front surface (reflecting surface) of each reflecting mirror can be quickly transmitted to the back surface, and heat can be removed from each reflecting mirror by the action of an appropriate cooling mechanism, for example.

  FIG. 9 is a diagram schematically showing an example of a cooling mechanism that cools each reflecting mirror of the condensing optical system. Referring to FIG. 9, the 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 constituting the condensing optical system 12, respectively. Thus, heat can be released to the outside from the concave reflecting mirror 12a and the convex reflecting mirror 12b by the action of the heat pipes 20a and 20b. However, the cooling mechanism applicable to each reflecting mirror 12a, 12b of the condensing optical system 12 is not limited to the configuration example of FIG. 9, and for example, a cooling liquid (cold water or the like) is provided inside the main body of each reflecting mirror 12a, 12b. ) Can also be adopted.

  In the present embodiment, the concave reflecting mirror 12a and the convex reflecting mirror 12b constituting the condensing optical system 12 are affected by the radiant heat from the DPP light source body 11 and the irradiation heat of the DPP diverging light. It is preferable that the configuration is possible. In particular, the concave reflecting mirror 12a whose reflecting surface is directly exposed to the DPP light source body 11 is expected to be replaced to some extent frequently.

  In order to easily exchange the concave reflecting mirror 12a and the convex reflecting mirror 12b constituting the condensing optical system 12, in order to measure the position of the reflecting surface of the concave reflecting mirror 12a and the position of the reflecting surface of the convex reflecting mirror 12b. It is preferable to provide the position measuring means. FIG. 10 is a diagram schematically illustrating an example of a position measurement system that measures the reflection surface position of the reflecting mirror that constitutes the condensing optical system. In the position measurement system shown in FIG. 10, the light from the masks 21a, 21b, and 21c is emitted from the front groups 22a, 22b, and 22c of the imaging optical system, the reflecting surface of the concave reflecting mirror 12a, and the rear group 23a of the imaging optical system. Mask patterns are formed on screens (or CCDs) 24a, 24b, and 24c through 23b and 23c, respectively.

  Thus, based on the two-dimensional position information of the mask patterns formed on the screens 24a, 24b, and 24c, the new concave reflecting mirror 12a can be positioned with high accuracy when the concave reflecting mirror 12a is replaced. 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, for example, the degree of contamination of the reflecting surface of the concave reflecting mirror 12a caused by debris (deterioration of optical characteristics) can be detected more accurately, and the concave reflecting mirror 12a can be replaced at an appropriate timing. Can do.

  Further, when replacing the convex reflecting mirror 12b, the position measuring system (21 to 24) having the same configuration as in FIG. 10 is used to position the new convex reflecting mirror 12b with high accuracy, or the convex reflecting mirror 12b. It is possible to detect the degree of dirt on the reflecting surface. Note that the configuration of the measurement system for measuring the position of the reflecting surface of each reflecting mirror and detecting the degree of dirt on the reflecting surface is not limited to the configuration example of FIG. 10, and various modifications are possible. is there.

  Further, as described above, when debris emitted upon emission of DPP divergent light from the DPP light source body 11 adheres to the reflecting surface of the concave reflecting mirror 12a or the reflecting surface of the convex reflecting mirror 12b, the concave reflecting mirror 12a or the convex reflecting mirror is used. The reflection characteristics (optical characteristics) of the mirror 12b deteriorate, and the replacement frequency increases. Therefore, in the present embodiment, debris for removing debris emitted from the DPP light source body 11 in the optical path between the concave reflecting mirror 12a (first reflecting mirror) and the convex reflecting mirror 12b (second reflecting mirror). A removal mechanism is preferably provided.

  FIG. 11 is a diagram schematically showing an example of a debris removing mechanism for removing in the optical path between a pair of reflecting mirrors constituting the condensing optical system, where (a) shows a perspective view and (b) ) Shows a cross-sectional view along the optical axis. Referring to FIG. 11, the debris removal mechanism has a cylindrical casing 25 for enclosing the space between the concave reflecting mirror 12a and the convex reflecting mirror 12b, and the space is relatively free from EUV light. A very small amount of a predetermined gas having a high transmittance is introduced through the gas inlet 25a.

The casing 25 is formed of, for example, a metal such as stainless steel, copper, or aluminum, and is connected to the ground potential. For example, helium (He), argon (Ar), neon (Ne), xenon (Xe), krypton (Kr), nitrogen (N ₂ ), oxygen (O ₂ ), ozone (O ₃ ) can be used. The debris removing mechanism includes a plurality of plate members 26 having a cross section that extends radially about 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 to be applied with a positive potential (several tens of volts to several kV) by a power source. In other words, a predetermined voltage is set between the plurality of plate members 26 and the casing 25. The plurality of plate members 26 are configured to be integrally rotatable around the optical axis AX. Further, the casing 25 and the plurality of plate members 26 are configured to be cooled by an appropriate cooling mechanism (not shown).

  In the debris removal mechanism shown in FIG. 11, a part of the debris emitted from the plasma enters the internal space of the casing 25, but rapidly loses its kinetic energy due to collision with gas molecules introduced into the casing 25. Then, it floats in the internal space of the casing 25 with almost the same kinetic energy as the gas molecules. Then, the debris floating is ionized directly by EUV light radiated from the plasma, or debris is ionized by collision with ionized gas molecules (atoms).

  When the debris is ionized negatively, the debris is attracted to and attached to and deposited on the plurality of plate members 26 to which a positive potential is applied. 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. As a result, it is possible to reduce the deterioration of reflection characteristics and the frequency of replacing the reflecting mirror. At this time, by attaching the multilayer reflective film coated on the surfaces of the reflecting mirrors 12a and 12b to the ground potential, the adhesion of debris to the reflecting surface can be further effectively reduced.

  On the other hand, when debris is ionized positively, it adheres and accumulates on the inner surface of the casing 25 connected to the ground potential. At this time, the same potential as the plurality of plate members 26 or higher potential is applied to the multilayer reflective film coated on the surfaces of the reflecting mirrors 12a and 12b, thereby attaching and depositing debris on the reflecting surface. Can be prevented. Alternatively, a sheet (an insulating material such as paper, resin, 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 adhered and deposited on the sheet. In this case, it is possible to easily return to a clean environment by simply replacing the sheet after waiting for a large amount of debris to adhere to the sheet.

  In addition, when ionization of debris cannot be sufficiently performed only by EUV light from plasma, ultraviolet rays are emitted into the casing 25 through an opening (or a light transmitting portion) formed in a part of the casing 25. It may be configured to introduce and promote debris ionization by the action of the ultraviolet rays. In this case, a mercury lamp, excimer lamp, excimer laser, or the like can be used as a light source for supplying ultraviolet rays. Alternatively, the debris may be ionized by introducing an electron beam from an electron source into the casing 25.

  When the debris removal mechanism shown in FIG. 11 is used, a plurality of plate members 26 are integrated around the optical axis AX in order to make the light intensity distribution of the light beam emitted from the condensing optical system 12 uniform during exposure. It is preferable to rotate it. In the configuration example of FIG. 11, a positive potential is applied to the plurality of plate members 26, but the present invention is not limited to this, and a negative potential may be applied to the plurality of plate members 26. Further, the applied potential may be direct current or alternating current. Furthermore, when an alternating potential is applied, various modes are possible for the frequency.

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

  In the EUV light source 43, EUV light 45 is emitted from the plasma 44 generated in the vicinity of 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 is also a convex reflecting mirror (second reflecting mirror) coated with a Mo / Si multilayer film. After being reflected at 47, the light 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 reflectance peak with respect to light having a wavelength of 13.5 nm. That is, the EUV light guided to the subsequent optical system after passing through the pinhole 52 is only light having a wavelength in the vicinity of 13.5 nm.

  The concave reflecting mirror 46 and the convex reflecting mirror 47 are fixed in the casing 48. A gas introduction port 49 is attached to the casing 48, and He gas is introduced into the casing 48 from the port 49. In the casing 48, between the concave reflecting mirror 46 and the convex reflecting mirror 47, a plurality of aluminum thin 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 wing 50 is rotationally driven by an ultrasonic motor or an electric motor. The casing 48 is attached to the wall surface of the vacuum container 41. A vacuum container 42 is installed next to the vacuum container 41, and the vacuum containers 41 and 42 communicate with each other only through an opening through which EUV light passes. The vacuum vessel 42 is evacuated separately from the vacuum vessel 41 by an unillustrated evacuation device. By adopting such a configuration, differential evacuation can be performed between the vacuum vessels 41 and 42, and deterioration of the degree of vacuum downstream of the pinhole 52 can be reduced.

  The debris that has entered the casing 48 is collided and scattered by the He gas introduced from the port 49, and rapidly loses its energy and floats in the casing 48. The debris floating in the casing 48 collides with the wings 50 and the inner wall of the casing 48 and is adsorbed. As a result, the amount of debris that adheres and accumulates 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 in the vicinity of the EUV light beam in the vacuum vessel 42, debris that has entered the vacuum vessel 42 collides with and is attracted to the inner wall of the cylindrical member 51, so that it is downstream of the pinhole 52. It is possible to reduce the inflow of debris. Cooling the casing 48, the wings 50, and the cylindrical member 51 is preferable because the probability that the adsorbed debris is re-released is reduced and the adsorption efficiency is further increased. As a cooling method, cooling with a refrigerant (liquid such as water), electronic cooling of a Peltier element, cooling with a heat pipe, or the like may be used. If the degree of vacuum on the downstream side of the pinhole 52 is better without the cylindrical member 51, the installation of the cylindrical member 51 can be omitted.

  In the exposure apparatus according to the above-described embodiment, the illumination system illuminates the mask (illumination process), and exposes the transfer pattern formed on the mask using the projection optical system onto the photosensitive substrate (exposure process). Microdevices (semiconductor elements, imaging elements, liquid crystal display elements, thin film magnetic heads, etc.) can be manufactured. Hereinafter, referring to the flowchart of FIG. 13 for an example of a method for obtaining a semiconductor device as a micro device by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of this embodiment. I will explain.

  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 lot of wafers. Thereafter, in step 303, using the exposure apparatus of the present embodiment, the pattern image on the mask (reticle) is sequentially exposed and transferred to each shot area on the wafer of one lot via the projection optical system. .

  Thereafter, in step 304, the photoresist on the one lot of wafers is developed, and in step 305, the resist pattern is etched on the one lot of wafers to form a pattern on the mask. Corresponding circuit patterns are formed in each shot area on each wafer. Thereafter, a device pattern such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer. According to the semiconductor device manufacturing method described above, a semiconductor device having an extremely fine circuit pattern can be obtained with high throughput.

It is a figure which shows schematically the whole structure of the exposure apparatus provided with the light source unit concerning embodiment of this invention. It is a figure which shows the positional relationship of the arc-shaped exposure area | region (namely, effective exposure area | region) formed on a wafer, and an optical axis. It is a figure which shows schematically the internal structure of the light source unit of FIG. 1, and an illumination optical system. It is a figure which shows schematically the internal structure of a light source main body. It is a figure which shows schematically the structure of the condensing optical system concerning the numerical example of this embodiment. It is a figure explaining the inconvenience of the structure which concentrates the DPP divergent light from a DPP light source main body simply by one concave reflecting mirror. It is a figure explaining the inconvenience of the structure which condenses the DPP divergent light from a DPP light source main body with a nested oblique incidence mirror. It is a figure explaining the inconvenience of the structure which condenses the DPP divergent light from a DPP light source main body with a Schwarzschild optical system. It is a figure which shows roughly an example of the cooling mechanism which cools each reflective mirror of a condensing optical system. It is a figure which shows roughly an example of the position measurement system which measures the reflective surface position of the reflective mirror which comprises a condensing optical system. It is a figure which shows roughly an example of the debris removal mechanism for removing in the optical path between a pair of reflective mirrors which comprise a condensing optical system, Comprising: (a) shows a perspective view, (b) shows an optical axis. FIG. It is a figure which shows roughly the example which applied the debris removal mechanism of this embodiment to the Schwarzschild condensing optical system. It is a figure which shows the flowchart about an example of the method at the time of obtaining the semiconductor device as a microdevice.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source unit 2 Illumination optical system 5 Mask stage 7 Wafer stage 11 Light source main body 11a, 11b Electrode 12 Condensing optical system 12a Concave reflector 12b Convex reflector 14 Optical integrator 14a, 14b Fly eye mirror M Mask PL Projection optical system W Wafer

Claims (13)

A light source body that converts the target material into plasma and emits EUV light from the plasma;
A first reflecting mirror having a through hole;
A second reflecting mirror disposed in an optical path between the light source body and the first reflecting mirror ;
A casing for enclosing a space between the first reflecting mirror and the second reflecting mirror; and a plurality of plate members provided in the casing and having a cross section extending radially around the optical axis. , and a debris removal mechanism for removing the optical path between the debris emitted from the light source body and the second reflecting mirror and the first reflecting mirror,
The EUV light is condensed at a predetermined position through 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. . The light source unit according to claim 1, wherein a predetermined gas is introduced into the space . The light source unit according to claim 2, wherein the predetermined gas is helium, argon, neon, xenon, krypton, nitrogen, oxygen, or ozone . The light source unit according to claim 1, wherein the plurality of plate members and the casing are configured to be cooled . The light source unit according to any one of claims 1 to 4, wherein a predetermined voltage is applied between the plurality of plate members and the casing . The light source unit according to claim 1, wherein the plurality of plate members are configured to be rotatable about the optical axis . A light source body that converts target material into plasma and emits EUV light from the plasma, a first reflecting mirror having a through hole, and a second reflection disposed in an optical path between the light source body and the first reflecting mirror With a mirror,
A plurality of plate members having a cross section extending radially around the optical axis, and for removing debris emitted from the light source body in an optical path between the first reflecting mirror and the second reflecting mirror; A debris removal mechanism,
Condensing the EUV light at a predetermined position via 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,
The light source unit , wherein the plurality of plate members are configured to be cooled . The debris removal mechanism has a casing for enclosing a space between the first reflecting mirror and the second reflecting mirror, and the casing is configured to be cooled. The light source unit described in 1. 9. An illumination optical apparatus comprising: the light source unit according to claim 1; and a light guide optical system for guiding EUV light from the light source unit to an irradiated surface. An illumination optical apparatus according to claim 9 for illuminating a reflective mask on which a predetermined pattern is formed, and a projection optical system for forming a pattern image of the mask on a photosensitive substrate. An exposure apparatus characterized by that. The exposure according to claim 10, wherein the mask and the photosensitive substrate are moved relative to the projection optical system along a predetermined direction to project and expose the mask pattern onto the photosensitive substrate. apparatus. An illumination process for illuminating a reflective mask on which a predetermined pattern is formed using the illumination optical apparatus according to claim 9, and projection exposure of the mask pattern onto the photosensitive substrate via a projection optical system An exposure method comprising an exposure step. 13. The exposure step of projecting and exposing the pattern of the mask onto the photosensitive substrate by moving the mask and the photosensitive substrate relative to the projection optical system along a predetermined direction. An exposure method according to 1.

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