JP4816769B2 - Optical element and exposure apparatus - Google Patents

Description

  The present invention is used for transferring a mask pattern onto a photosensitive substrate in a lithography process for manufacturing a device such as a semiconductor element, an imaging element (CCD, etc.), a liquid crystal display element, or a thin film magnetic head. The present invention relates to an optical element used in a projection exposure apparatus using a liquid immersion method, and an exposure apparatus using the optical element.

  When manufacturing a semiconductor element, etc., a reticle pattern image as a mask is transferred to each shot area on a wafer (or glass plate, etc.) coated with a resist as a photosensitive substrate via a projection optical system. A projection exposure apparatus is used. Conventionally, a step-and-repeat type reduction projection type exposure apparatus (stepper) has been widely used as a projection exposure apparatus, but recently, a step-and-scan system that performs exposure by synchronously scanning a reticle and a wafer. The projection exposure apparatus is also attracting attention.

  The resolution of the projection optical system provided in the projection exposure apparatus becomes higher as the exposure wavelength used becomes shorter and the numerical aperture of the projection optical system becomes larger. For this reason, with the miniaturization of integrated circuits, the exposure wavelength used in the projection exposure apparatus has become shorter year by year, and the numerical aperture of the projection optical system has also increased. The mainstream exposure wavelength is 248 nm for a KrF excimer laser, but 193 nm for an ArF excimer laser having a shorter wavelength is also in practical use.

  By the way, as the wavelength of exposure light is shortened, glass materials having a transmittance that can secure a sufficient amount of light for exposure while securing a desired imaging performance are limited, so that the space between the lower surface of the projection optical system and the wafer surface is limited. Is filled with a liquid such as water or an organic solvent, and the wavelength of exposure light in the liquid is 1 / n times that in air (n is a refractive index of the liquid, usually about 1.2 to 1.6). There has been proposed an immersion type projection exposure apparatus that improves the resolution by using (see, for example, Patent Document 1).

JP-A-10-303114

  However, in this immersion type projection exposure apparatus, exposure light and exposure light reflected light from the wafer are irradiated to the sealing member provided in the periphery of the tapered surface of the transmission optical element on the substrate side of the projection optical system, There was a problem that the sealing member deteriorated.

  An object of the present invention is to provide an optical element in which a sealing member does not deteriorate and an exposure apparatus including the optical element.

  The optical element of the present invention illuminates the mask with an exposure beam, transfers the pattern of the mask onto the substrate via the projection optical system, and interposes a predetermined liquid between the surface of the substrate and the projection optical system. An optical element used in the exposure apparatus, wherein a light shielding film is formed on a tapered surface of the transmission optical element on the substrate side of the projection optical system.

  The exposure apparatus of the present invention illuminates a mask with an exposure beam, transfers the pattern of the mask onto the substrate via the projection optical system, and interposes a predetermined liquid between the surface of the substrate and the projection optical system. In the exposure apparatus, a light shielding film is formed on a tapered surface of a transmission optical element on the substrate side of the projection optical system.

  According to the optical element of the present invention, the light shielding film irradiates the exposure member and the exposure light reflected light from the wafer onto the seal member provided around the tapered surface of the transmission optical element on the substrate side of the projection optical system. Can be prevented, and the deterioration of the seal member can be prevented.

  According to the exposure apparatus of the present invention, the light shielding film irradiates the exposure member and the exposure light reflected from the wafer onto the seal member provided on the periphery of the tapered surface of the transmission optical element on the substrate side of the projection optical system. Can be prevented, and the deterioration of the seal member can be prevented.

It is a figure which shows schematic structure of the projection exposure apparatus used in the 1st Embodiment of this invention. It is a figure for demonstrating the film | membrane formed into the front-end | tip part 4A of the optical element 4 of the projection optical system PL concerning 1st Embodiment, and the taper surface 4B. It is a figure which shows the positional relationship of the front-end | tip part 4A of the optical element 4 of the projection optical system PL concerning 1st Embodiment, the discharge nozzle for X directions, and an inflow nozzle. It is a figure which shows the positional relationship of the front-end | tip part 4A of the optical element 4 of the projection optical system PL concerning 1st Embodiment, and the discharge | emission nozzle and inflow nozzle which supply and collect | recover liquid from a Y direction. FIG. 3 is an enlarged view of a main part showing a state of supply and recovery of the liquid 7 between the optical element 4 and the wafer W according to the first embodiment. It is a front view which shows the lower end part of the projection optical system PLA of the projection exposure apparatus used in the 2nd Embodiment of this invention, the liquid supply apparatus 5, the liquid collection | recovery apparatus 6, etc. FIG. It is a figure which shows the positional relationship of the front-end | tip part 32A of the optical element 32 of the projection optical system PLA concerning 2nd Embodiment, the discharge nozzle for X directions, and an inflow nozzle. It is a figure which shows the positional relationship of the front-end | tip part 32A of the optical element 32 of the projection optical system PLA concerning 2nd Embodiment, and the discharge nozzle and inflow nozzle which supply and collect | recover liquid from a Y direction. Of the optical elements constituting the projection optical system PL of the exposure apparatus according to the third embodiment, the image of the projection optical system PL next to the first optical element LS1 and the first optical element LS1 closest to the image plane of the projection optical system PL. It is a figure which shows 2nd optical element LS2 etc. near a surface. 1 is a diagram illustrating a configuration of a transmission optical element according to Example 1. FIG. 1 is a diagram illustrating a configuration of a tester according to Example 1. FIG. FIG. 6 is a diagram illustrating a configuration of a transmission optical element according to Example 2. 6 is a diagram illustrating a configuration of a transmission optical element according to Example 3. FIG. It is a figure which shows the structure of the transmission optical element of a comparative example.

  A projection exposure apparatus according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a step-and-repeat projection exposure apparatus according to the first embodiment. In the following description, the XYZ orthogonal coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Y axis are parallel to the wafer W, and the Z axis is set in a direction orthogonal to the wafer W. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z-axis is set vertically upward.

  As shown in FIG. 1, the projection exposure apparatus according to this embodiment includes an ArF excimer laser light source as an exposure light source, and includes an illumination optical system 1 including an optical integrator (homogenizer), a field stop, a condenser lens, and the like. It has. Exposure light (exposure beam) IL made up of ultraviolet pulsed light having a wavelength of 193 nm emitted from a light source passes through the illumination optical system 1 and illuminates a pattern provided on a reticle (mask) R. The light that has passed through the reticle R passes through the telecentric projection optical system PL on both sides (or one side on the wafer W side) and reaches a predetermined projection magnification β (for example, on an exposure region on the wafer (substrate) W coated with photoresist. , Β is 1/4, 1/5, etc.) and reduced projection exposure is performed.

As the exposure light IL, KrF excimer laser light (wavelength 248 nm), F ₂ laser light (wavelength 157 nm), i-line (wavelength 365 nm) of a mercury lamp, or the like may be used.

  The reticle R is held on a reticle stage RST, and a mechanism for finely moving the reticle R in the X direction, the Y direction, and the rotation direction is incorporated in the reticle stage RST. The positions of the reticle stage RST in the X direction, the Y direction, and the rotational direction are measured and controlled in real time by a reticle laser interferometer (not shown).

  The wafer W is fixed on the Z stage 9 via a wafer holder (not shown). The Z stage 9 is fixed on an XY stage 10 that moves along an XY plane substantially parallel to the image plane of the projection optical system PL, and the focus position (position in the Z direction) and tilt angle of the wafer W are set. Control. The positions of the Z stage 9 in the X direction, the Y direction, and the rotation direction are measured and controlled in real time by a wafer laser interferometer 13 using a moving mirror 12 positioned on the Z stage 9. The XY stage 10 is placed on the base 11 and controls the X direction, Y direction, and rotation direction of the wafer W.

  The main control system 14 provided in the projection exposure apparatus adjusts the position of the reticle R in the X direction, the Y direction, and the rotational direction based on the measurement values measured by the reticle laser interferometer. That is, the main control system 14 adjusts the position of the reticle R by transmitting a control signal to a mechanism incorporated in the reticle stage RST and finely moving the reticle stage RST.

  Also, the main control system 14 adjusts the focus position (position in the Z direction) and the tilt angle of the wafer W in order to adjust the surface on the wafer W to the image plane of the projection optical system PL by the auto focus method and the auto leveling method. To do. That is, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the Z stage 9 by the wafer stage drive system 15 to adjust the focus position and the tilt angle of the wafer W. Further, the main control system 14 adjusts the position of the wafer W in the X direction, the Y direction, and the rotation direction based on the measurement values measured by the wafer laser interferometer 13. That is, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the XY stage 10 by the wafer stage drive system 15 to adjust the position of the wafer W in the X direction, Y direction, and rotation direction. .

  At the time of exposure, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the XY stage 10 by the wafer stage drive system 15 to sequentially step each shot area on the wafer W to the exposure position. . That is, the operation of exposing the pattern image of the reticle R onto the wafer W by the step-and-repeat method is repeated.

  In this projection exposure apparatus, an immersion method is applied to substantially shorten the exposure wavelength and improve the resolution. Here, in the immersion type projection exposure apparatus to which the immersion method is applied, at least while the pattern image of the reticle R is transferred onto the wafer W, the surface of the wafer W and the side of the projection optical system PL on the wafer W side. A predetermined liquid 7 is filled in between the transmissive optical element 4. The projection optical system PL includes a lens barrel 3 that houses a plurality of optical elements formed of quartz or fluorite constituting the projection optical system PL. In this projection optical system PL, the transmissive optical element 4 closest to the wafer W is formed of fluorite, and the surface of the transmissive optical element 4 (the tip 4A and the tapered surface 4B on the wafer W side (see FIG. 2)). Only the liquid 7 is in contact. As a result, corrosion of the lens barrel 3 made of metal is prevented.

Here, the base material of the transmissive optical element 4 is fluorite, and the crystal orientation of the fluorite film-forming surface is the (111) plane. Further, a magnesium fluoride (MgF ₂ ) film F1 formed of a single layer film is formed by a vacuum deposition method at the front end portion 4A on the wafer W side of the transmission optical element 4, that is, a portion through which exposure light is transmitted. Yes.

Further, a tantalum (Ta) film is formed by sputtering as the adhesion enhancing film F2 on the tapered surface 4B of the transmissive optical element 4, that is, the portion where the exposure light is not transmitted. The adhesion enhancing film F2 improves the adhesion between the tapered surface 4B of the transmissive optical element 4 and a metal dissolution preventing film (dissolution preventing film) F3 described later. On the surface of the adhesion enhancing film F2, a metal film made of gold (Au) as a metal dissolution preventing film (dissolution preventing film) F3 for preventing dissolution in the liquid 7 is formed by sputtering to 150 nm. The film is formed with a thickness of. Further, the surface of the metal dissolution preventing film (dissolution preventing film) F3 is made of carbon dioxide as a metal dissolution preventing film protective film (dissolution preventing film protective film) F4 for protecting the metal dissolution preventing film (dissolution preventing film). A silicon (SiO ₂ ) film is formed by a sputtering method. Here, the solubility of the metal dissolution preventing film (dissolution preventing film) F3 formed on the tapered surface 4B of the transmission optical element 4 in pure water is 2 ppt or less, and the filling density is 95% or more.

  As the liquid 7, pure water that can be easily obtained in large quantities at a semiconductor manufacturing factory or the like is used. Since pure water has a very low impurity content, it can be expected to clean the surface of the wafer W.

  FIG. 3 shows two pairs of the transmission optical element 4 of the projection optical system PL, the front end portion 4A and the tapered surface 4B on the wafer W side and the wafer W, and the front end portion 4A and the tapered surface 4B on the wafer W side sandwiched in the X direction. It is a figure which shows the positional relationship with a discharge nozzle and an inflow nozzle. FIG. 4 shows two pairs of discharges sandwiching the front end 4A and the tapered surface 4B on the wafer W side of the transmission optical element 4 of the projection optical system PL, and the front end 4A and the tapered surface 4B on the wafer W side in the Y direction. It is a figure which shows the positional relationship with a nozzle and an inflow nozzle. The projection exposure apparatus according to this embodiment includes a liquid supply device 5 that controls the supply of the liquid 7 and a liquid recovery device 6 that controls the discharge of the liquid 7.

  The liquid supply device 5 includes a liquid 7 tank (not shown), a pressure pump (not shown), a temperature control device (not shown), and the like. Further, as shown in FIG. 3, the liquid supply apparatus 5 includes a discharge nozzle 21 a having a thin tip on the + X direction side of the tip 4 </ b> A on the wafer W side and the tapered surface 4 </ b> B via the supply pipe 21. A discharge nozzle 22 a having a thin tip portion is connected to the tip end portion 4 A on the wafer W side and the −X direction side of the taper surface 4 B through 22. Further, as shown in FIG. 4, the liquid supply apparatus 5 includes a discharge nozzle 27a having a thin tip on the + Y direction side of the tip 4A on the wafer W side and the taper surface 4B via the supply pipe 27. A discharge nozzle 28a having a thin tip portion is connected to the tip end portion 4A on the wafer W side and the −Y direction side of the tapered surface 4B via the pin 28. The liquid supply device 5 adjusts the temperature of the liquid 7 by a temperature control device, and at least one of the discharge nozzles 21a, 22a, 27a, 28a has at least one of the supply pipes 21, 22, 27, 28. The temperature-adjusted liquid 7 is supplied onto the wafer W through one supply pipe. The temperature of the liquid 7 is set by the temperature control device to be approximately the same as the temperature in the chamber in which the projection exposure apparatus according to this embodiment is housed, for example.

  The liquid recovery apparatus 6 includes a liquid 7 tank (not shown), a suction pump (not shown), and the like. In addition, in the liquid recovery apparatus 6, as shown in FIG. 3, inflow nozzles 23 a and 23 b having wide tip portions on the −X direction side of the tapered surface 4 </ b> B through the recovery pipe 23 are tapered through the recovery pipe 24. Inflow nozzles 24a and 24b having wide tip portions are connected to the + X direction side of the surface 4B. The inflow nozzles 23a, 23b, 24a, and 24b are arranged in a fan-like shape with respect to an axis that passes through the center of the tip 4A on the wafer W side and is parallel to the X axis. Further, in the liquid recovery apparatus 6, as shown in FIG. 4, inflow nozzles 29 a and 29 b having wide tip portions on the −Y direction side of the taper surface 4 </ b> B through the recovery pipe 29 are tapered through the recovery pipe 30. Inflow nozzles 30a and 30b having wide tip portions are connected to the + Y direction side of the surface 4B. The inflow nozzles 29a, 29b, 30a, and 30b are arranged in a fan-like shape with respect to an axis that passes through the center of the tip 4A on the wafer W side and is parallel to the Y axis.

  The liquid recovery apparatus 6 includes at least one recovery pipe in the recovery pipes 23, 24, 29, 30 from at least one inflow nozzle in the inflow nozzles 23a and 23b, 24a and 24b, 29a and 29b, 30a and 30b. The liquid 7 is recovered from the wafer W via

  Next, a method for supplying and collecting the liquid 7 will be described. In FIG. 3, when the wafer W is moved stepwise in the direction of the arrow 25A indicated by the solid line (−X direction), the liquid supply device 5 uses the supply pipe 21 and the discharge nozzle 21a to move the wafer W of the transmissive optical element 4 through. The liquid 7 is supplied between the side tip 4A and the tapered surface 4B and the wafer W. The liquid recovery apparatus 6 includes a liquid 7 supplied between the wafer W side tip 4A and the tapered surface 4B and the wafer W from the wafer W via the recovery pipe 23 and the inflow nozzles 23a and 23b. Recover. In this case, the liquid 7 flows on the wafer W in the direction of the arrow 25B (−X direction), and the space between the wafer W and the transmission optical element 4 is stably filled with the liquid 7.

  On the other hand, in FIG. 3, when the wafer W is stepped in the direction of the arrow 26A indicated by the chain line (+ X direction), the liquid supply device 5 uses the supply pipe 22 and the discharge nozzle 22a to move the wafer of the transmissive optical element 4 The liquid 7 is supplied between the W-side tip 4A and the tapered surface 4B and the wafer W. The liquid recovery device 6 recovers the liquid 7 supplied between the wafer W side tip 4A and the tapered surface 4B and the wafer W by the liquid supply device 5 via the recovery pipe 24 and the inflow nozzles 24a and 24b. . In this case, the liquid 7 flows on the wafer W in the direction of the arrow 26B (+ X direction), and the space between the wafer W and the transmission optical element 4 is stably filled with the liquid 7.

  Further, when stepping the wafer W in the Y direction, the liquid 7 is supplied and recovered from the Y direction. That is, in FIG. 4, when the wafer W is stepped in the direction of the arrow 31A indicated by the solid line (−Y direction), the liquid supply device 5 supplies the liquid 7 via the supply pipe 27 and the discharge nozzle 27a. To do. The liquid recovery device 6 recovers the liquid 7 supplied between the wafer W side tip 4A and the tapered surface 4B and the wafer W by the liquid supply device 5 through the recovery pipe 29 and the inflow nozzles 29a and 29b. . In this case, it flows in the direction of the arrow 31B (−Y direction) over the exposure region, and the space between the wafer W and the transmissive optical element 4 is stably filled with the liquid 7.

  Further, when the wafer W is stepped in the + Y direction, the liquid supply device 5 supplies the liquid 7 via the supply pipe 28 and the discharge nozzle 28a. The liquid recovery device 6 recovers the liquid 7 supplied between the front end 4A on the wafer W side and the wafer W by the liquid supply device 5 via the recovery pipe 30 and the inflow nozzles 30a and 30b. In this case, the liquid 7 flows in the + Y direction on the exposure region, and the space between the wafer W and the transmissive optical element 4 is stably filled with the liquid 7.

  In addition to the nozzle that supplies and recovers the liquid 7 from the X direction or the Y direction, for example, a nozzle that supplies and recovers the liquid 7 from an oblique direction may be provided.

  Next, a method for controlling the supply amount and the recovery amount of the liquid 7 will be described. FIG. 5 is a view showing a state in which the liquid 7 is supplied and recovered between the transmission optical element 4 constituting the projection optical system PL and the wafer W. FIG. As shown in FIG. 5, when the wafer W is moving in the direction of the arrow 25A (−X direction), the liquid 7 supplied from the discharge nozzle 21a flows in the direction of the arrow 25B (−X direction) It is collected by the inflow nozzles 23a and 23b. Even when the wafer W is moving, in order to keep the amount of the liquid 7 filled between the transmissive optical element 4 and the wafer W constant, the supply amount and the recovery amount of the liquid 7 are made equal. Further, the liquid 7 is always filled between the transmissive optical element 4 and the wafer W by adjusting the supply amount and the recovery amount of the liquid 7 based on the moving speed of the XY stage 10 (wafer W).

According to the projection exposure apparatus of the first embodiment, the metal film is formed on the surface of the adhesion enhancing film formed on the tapered surface 4B of the transmission optical element 4 on the wafer W side of the projection optical system PL. Since the film is formed, the metal film can be adhered to the transmission optical element 4. Further, since the silicon dioxide (SiO ₂ ) film is formed on the surface of the metal film, damage to the metal film which is soft and has low scratch resistance can be prevented, and the metal film can be protected. Accordingly, the penetration and erosion of the liquid 7 interposed between the surface of the wafer W and the projection optical system PL can be prevented and the optical performance of the projection optical system PL can be maintained. . Further, since the transmission optical element 4 is not dissolved by the liquid 7, the performance of the projection exposure apparatus can be maintained. Furthermore, since it is not necessary to frequently replace the transmission optical element 4, the throughput of the projection exposure apparatus can be maintained high.

  Further, since the metal film is formed on the tapered surface 4B of the transmissive optical element 4, that is, the portion through which the exposure light IL does not pass, the metal film formed on the surface of the transmissive optical element 4 blocks the exposure light IL. The exposure can be continued in an optimum state.

Further, according to the projection exposure apparatus according to the first embodiment, a magnesium fluoride (MgF ₂ ) film, which is a single layer film, is formed on the front end portion 4A of the transmission optical element 4 on the wafer side. It is possible to prevent the transmission optical element from being dissolved. In addition, since the interface can be reduced when compared with a multilayer film, adverse effects due to chemical reactions that can occur when liquid enters from the interface of the protective layer of the magnesium fluoride (MgF ₂ ) film can be minimized. . Further, it can be easily formed as compared with the case where a film formed of a multilayer film is formed.

  Further, the refractive index n of pure water for exposure light having a wavelength of about 200 nm is about 1.44, and the ArF excimer laser light having a wavelength of 193 nm is shortened to 1 / n on the wafer W, that is, 134 nm. Therefore, high resolution can be obtained.

  Further, according to the projection exposure apparatus according to the first embodiment, since the two discharge nozzles and the inflow nozzles which are reversed in the X direction and the Y direction are provided, the wafer is moved in the + X direction and the −X direction. Even when moving in the + Y direction or the −Y direction, the space between the wafer and the optical element can be stably filled with the liquid.

  Further, since the liquid flows on the wafer, the foreign matter can be washed away by the liquid even when the foreign matter is adhered on the wafer. In addition, since the liquid is adjusted to a predetermined temperature by the liquid supply device, the temperature of the wafer surface is also constant, and a decrease in overlay accuracy due to thermal expansion of the wafer that occurs during exposure can be prevented. Therefore, even when there is a time difference between alignment and exposure as in the EGA (Enhanced Global Alignment) system, it is possible to prevent a decrease in overlay accuracy due to thermal expansion of the wafer.

  Further, according to the projection exposure apparatus according to the first embodiment, since the liquid flows in the same direction as the direction in which the wafer is moved, the liquid that has absorbed the foreign matter and the heat is directly below the surface of the transmissive optical element. The liquid can be recovered by the liquid recovery device without staying on the exposure area.

  In the projection exposure apparatus according to the first embodiment, a metal film composed of a film formed of gold (Au) is used as the metal dissolution preventing film (dissolution preventing film). Au), platinum (Pt), silver (Ag), nickel (Ni), tantalum (Ta), tungsten (W), palladium (Pd), molybdenum (Mo), titanium (Ti) and chromium (Cr) You may use the metal film comprised by the film | membrane formed by at least one.

  Further, in the projection exposure apparatus according to the first embodiment, an adhesion enhancing film composed of a film formed of tantalum (Ta) is used, but at least tantalum (Ta) and chromium (Cr) are used. You may use the adhesion strengthening film | membrane comprised with the film | membrane formed by one.

In the projection exposure apparatus according to the first embodiment, a metal dissolution prevention film protective film (dissolution prevention film protection film) composed of a film formed of silicon dioxide (SiO ₂ ) is used. , Silicon dioxide (SiO ₂ ), yttrium oxide (Y ₂ O ₃ ), neodymium fluoride (Nd ₂ F ₃ ), chromium oxide (Cr ₂ O ₃ ), tantalum pentoxide (Ta ₂ O ₅ ), niobium pentoxide ( Nb ₂ O ₅ ), titanium dioxide (TiO ₂ ), zirconium dioxide (ZrO ₂ ), hafnium dioxide (HfO ₂ ), and a film formed of at least one of lanthanum oxide (La ₂ O ₃ ) A metal dissolution prevention film protective film (dissolution prevention film protection film) may be used. That is, since a metal dissolution prevention film protective film (dissolution prevention film protection film) can be selected, the substrate of the transmission optical element, the environment in which the transmission optical element is installed, the surface of the substrate and the projection optical system Based on the type of liquid interposed between the two, an optimal metal dissolution preventing film protective film (dissolution preventing film protective film) can be selected. Further, in the projection exposure apparatus according to the first embodiment, a silicon dioxide (SiO ₂ ) film, which is a metal dissolution prevention film protective film (dissolution prevention film protection film), is formed by a dry film formation method such as a sputtering method. Although the film is formed, the film may be formed by a wet film formation method.

  Further, on the tapered surface of the transmission optical element according to the first embodiment, an adhesion strengthening film, a metal dissolution prevention film (dissolution prevention film), a metal dissolution prevention film protective film (dissolution prevention film protection film) However, only a metal dissolution prevention film (dissolution prevention film) may be formed. Further, an adhesion strengthening film and a metal dissolution preventing film (dissolution preventing film) may be formed, and a metal dissolution preventing film (dissolution preventing film) and a metal dissolution preventing film protective film (dissolution preventing film protecting film). ) May be formed.

  Further, in the projection exposure apparatus according to the first embodiment, the transmissive optical element 4 closest to the wafer W is formed of fluorite, and an adhesion enhancing film, a metal dissolution preventing film (on the taper surface) Dissolution prevention film) and metal dissolution prevention film protection film (dissolution prevention film protection film) are formed. The transmission optical element 4 closest to the wafer W is formed of quartz glass, and the adhesion is enhanced on the tapered surface. A film, a metal dissolution prevention film (dissolution prevention film), and a metal dissolution prevention film protective film (dissolution prevention film protection film) may be formed.

  Next, a projection exposure apparatus according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a front view showing the lower part of the projection optical system PLA of the step-and-scan projection exposure apparatus according to the second embodiment, the liquid supply device 5, the liquid recovery device 6, and the like. In the following description, the XYZ orthogonal coordinate system shown in FIG. 6 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Y axis are parallel to the wafer W, and the Z axis is set in a direction orthogonal to the wafer W. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z-axis is set vertically upward. In FIG. 6, the same components as those in the projection exposure apparatus according to the first embodiment are denoted by the same reference numerals as those used in the first embodiment.

  In this projection exposure apparatus, the transmission optical element 32 at the lowermost end of the lens barrel 3A of the projection optical system PLA is left in the Y direction (non-scanning direction), leaving only the portion necessary for the scanning exposure at the tip 32A on the wafer W side. It is cut into a long and narrow rectangle. At the time of scanning exposure, a pattern image of a part of the reticle (not shown) is projected onto a rectangular exposure area directly below the tip end portion 32A on the wafer W side, and the reticle (not shown) is projected to the projection optical system PLA. In synchronization with the movement at the speed V in the −X direction (or + X direction), the wafer W moves through the XY stage 10 at the speed β · V (β is the projection magnification) in the + X direction (or −X direction). To do. Then, after the exposure to one shot area is completed, the next shot area is moved to the scanning start position by stepping the wafer W, and the exposure to each shot area is sequentially performed by the step-and-scan method.

The base material of the transmission optical element 32 is fluorite, and the crystal orientation of the fluorite film-forming surface is the (111) plane. Further, a magnesium fluoride (MgF ₂ ) film composed of a single layer film is formed by a vacuum deposition method at the front end portion 32A on the wafer W side of the transmissive optical element 32, that is, a portion through which exposure light is transmitted. .

Further, a tantalum (Ta) film is formed by sputtering as an adhesion strengthening film on the tapered surface 32B of the transmissive optical element 32, that is, the portion where the exposure light is not transmitted. The adhesion enhancing film improves the adhesion between the tapered surface 32B of the transmissive optical element 32 and a metal dissolution preventing film (dissolution preventing film) described later. Further, a gold (Au) film is formed on the surface of the adhesion enhancing film by sputtering as a metal dissolution preventing film (dissolution preventing film) for preventing dissolution in the liquid 7. In addition, on the surface of the metal dissolution prevention film (dissolution prevention film), silicon dioxide (dissolution prevention film protection film) is used as a metal dissolution prevention film protection film (dissolution prevention film protection film) for protecting the metal dissolution prevention film (dissolution prevention film). SiO ₂ ) is formed by sputtering. Here, the solubility in pure water of the metal dissolution preventing film (dissolution preventing film) formed on the tapered surface 32B of the transmissive optical element 32 is 2 ppt or less, and the filling density is 95% or more.

  In the second embodiment as well, the liquid immersion method is applied as in the first embodiment, so that the liquid 7 is filled between the transmission optical element 32 and the surface of the wafer W during the scanning exposure. . As the liquid 7, pure water is used. Supply and recovery of the liquid 7 are performed by the liquid supply device 5 and the liquid recovery device 6, respectively.

  FIG. 7 shows the positional relationship between the surface of the transmissive optical element 32 of the projection optical system PLA (tip portion 32A and tapered surface 32B on the wafer W side) and the discharge nozzle and the inflow nozzle for supplying and collecting the liquid 7 in the X direction. FIG. As shown in FIG. 7, the liquid supply device 5 includes three discharge nozzles 21 a to 21 c on the + X direction side of the tip 32 </ b> A that is elongated in the Y direction and the tapered surface 32 </ b> B via the supply pipe 21. Three discharge nozzles 22a to 22c are connected to the −X direction side of the distal end portion 32A and the tapered surface 32B. Further, in the liquid recovery apparatus 6, as shown in FIG. 7, two inflow nozzles 23 a and 23 b are provided on the −X direction side of the tip end portion 32 </ b> A and the tapered surface 32 </ b> B via the recovery pipe 23. The two inflow nozzles 24a and 24b are connected to the + X direction side of the tip portion 32A and the tapered surface 32B.

  When scanning exposure is performed by moving the wafer W in the scanning direction (−X direction) indicated by the solid arrow, the liquid supply device 5 includes the transmission optical element 32 via the supply pipe 21 and the discharge nozzles 21a to 21c. The liquid 7 is supplied between the tip 32A and the tapered surface 32B and the wafer W. The liquid recovery device 6 recovers the liquid 7 supplied between the tip 32A and the tapered surface 32B and the wafer W by the liquid supply device 5 via the recovery pipe 23 and the inflow nozzles 23a and 23b. In this case, the liquid 7 flows on the wafer W in the −X direction, and the space between the transmissive optical element 32 and the wafer W is filled with the liquid 7.

  When scanning exposure is performed by moving the wafer W in the direction indicated by the chain line arrow (+ X direction), the liquid supply device 5 is connected to the transmission optical element 32 via the supply pipe 22 and the discharge nozzles 22a to 22c. The liquid 7 is supplied between the tip 32A and the tapered surface 32B and the wafer W. The liquid recovery apparatus 6 recovers the liquid 7 supplied between the tip 32A and the tapered surface 32B and the wafer W by the liquid supply apparatus 5 via the recovery pipe 24 and the inflow nozzles 24a and 24b.

  In this case, the liquid 7 flows on the wafer W in the + X direction, and the space between the transmissive optical element 32 and the wafer W is filled with the liquid 7. Further, by adjusting the supply amount and the recovery amount of the liquid 7, the liquid 7 is stably filled between the transmission optical element 32 and the wafer W even during the scanning exposure. When stepping the wafer W in the Y direction, the liquid 7 is supplied and recovered from the Y direction by the same method as in the first embodiment.

  FIG. 8 is a diagram showing the positional relationship between the distal end portion 32A and the tapered surface 32B of the transmission optical element 32 of the projection optical system PLA and the discharge nozzle and the inflow nozzle for the Y direction. As shown in FIG. 8, when the wafer W is moved stepwise in the non-scanning direction (−Y direction) orthogonal to the scanning direction, the discharge nozzle 27a and the inflow nozzles 29a and 29b arranged in the Y direction are used. Supply and recovery of the liquid 7 is performed. When the wafer is moved stepwise in the + Y direction, the liquid 7 is supplied and recovered using the discharge nozzle 28a and the inflow nozzles 30a and 30b arranged in the Y direction. Similarly to the first embodiment, when the step movement is performed in the Y direction, the liquid 7 is adjusted between the transmission optical element 32 and the wafer W by adjusting the supply amount of the liquid 7 according to the moving speed of the wafer W. 7 can continue to be satisfied.

According to the scanning projection exposure apparatus according to the second embodiment, the metal film is formed on the surface of the adhesion enhancing film formed on the tapered surface 32B of the transmission optical element 32 on the wafer W side of the projection optical system PLA. Therefore, the metal film can be brought into close contact with the transmission optical element 32. Further, since the silicon dioxide (SiO ₂ ) film is formed on the surface of the metal film, damage to the metal film which is soft and has low scratch resistance can be prevented, and the metal film can be protected. Therefore, it is possible to prevent the liquid 7 interposed between the surface of the wafer W and the projection optical system PLA from penetrating and eroding the transmission optical element 32, and to maintain the optical performance of the projection optical system PLA. . Further, since the transmission optical element 32 is not dissolved by the liquid 7, the performance of the scanning projection exposure apparatus can be maintained. Further, since it is not necessary to frequently replace the transmission optical element 32, the throughput of the scanning projection exposure apparatus can be maintained high.

  Further, since the metal film is formed on the tapered surface 32B of the transmissive optical element 32, that is, the portion where the exposure light does not pass, the metal film formed on the surface of the transmissive optical element 32 does not shield the exposure light, Exposure can be continued in an optimum state.

Further, according to the scanning projection exposure apparatus according to the second embodiment, a magnesium fluoride (MgF ₂ ) film, which is a single layer film, is formed on the front end portion of the transmission optical element on the wafer side. It is possible to prevent the transmission optical element from being dissolved. In addition, since the interface can be reduced when compared with a multilayer film, adverse effects due to chemical reactions that can occur when liquid enters from the interface of the protective layer of the magnesium fluoride (MgF ₂ ) film can be minimized. . Further, it can be easily formed as compared with the case where a film formed of a multilayer film is formed.

  Further, the refractive index n of pure water for exposure light having a wavelength of about 200 nm is about 1.44, and the ArF excimer laser light having a wavelength of 193 nm is shortened to 1 / n on the wafer W, that is, 134 nm. Therefore, high resolution can be obtained.

  Further, according to the projection exposure apparatus according to the second embodiment, since the two pairs of discharge nozzles and inflow nozzles reversed in the X direction and the Y direction are provided, the wafer W is moved in the + X direction, −X direction. Even when moving in the direction, + Y direction, or −Y direction, the space between the wafer W and the optical element 32 can be stably filled with the liquid 7. That is, by flowing the liquid in a direction corresponding to the moving direction of the wafer W, the space between the wafer W and the tip of the projection optical system PL can be continuously filled with the liquid 7.

  Further, since the liquid 7 flows on the wafer W, the foreign substance can be washed away by the liquid 7 even when the foreign substance is adhered on the wafer W. In addition, since the liquid 7 is adjusted to a predetermined temperature by the liquid supply device 5, the temperature of the surface of the wafer W is also constant, and it is possible to prevent a decrease in overlay accuracy due to thermal expansion of the wafer W that occurs during exposure. it can. Therefore, even when there is a time difference between alignment and exposure as in the EGA (Enhanced Global Alignment) system, it is possible to prevent a decrease in overlay accuracy due to thermal expansion of the wafer.

  In the scanning projection exposure apparatus according to the second embodiment, the liquid 7 flows in the same direction as the direction in which the wafer W is moved. Can be recovered by the liquid recovery device 6 without staying on the exposure region immediately below the tip portion 32A of the liquid crystal.

  In the projection exposure apparatus according to the second embodiment, a metal film composed of a film formed of gold (Au) is used as the metal dissolution prevention film (dissolution prevention film). Au), platinum (Pt), silver (Ag), nickel (Ni), tantalum (Ta), tungsten (W), palladium (Pd), molybdenum (Mo), titanium (Ti) and chromium (Cr) You may use the metal film comprised by the film | membrane formed by at least one.

  In the projection exposure apparatus according to the second embodiment, an adhesion enhancing film composed of a film formed of tantalum (Ta) is used, but at least tantalum (Ta) and chromium (Cr) are used. You may use the adhesion strengthening film | membrane comprised with the film | membrane formed by one.

In addition, in the projection exposure apparatus according to the second embodiment, a metal dissolution prevention film protective film (dissolution prevention film protection film) composed of a film formed of silicon dioxide (SiO ₂ ) is used. , Silicon dioxide (SiO ₂ ), yttrium oxide (Y ₂ O ₃ ), neodymium fluoride (Nd ₂ F ₃ ), chromium oxide (Cr ₂ O ₃ ), tantalum pentoxide (Ta ₂ O ₅ ), niobium pentoxide ( Nb ₂ O ₅ ), titanium dioxide (TiO ₂ ), zirconium dioxide (ZrO ₂ ), hafnium dioxide (HfO ₂ ), and a film formed of at least one of lanthanum oxide (La ₂ O ₃ ) A metal dissolution prevention film protective film (dissolution prevention film protection film) may be used. Further, in the projection exposure apparatus according to the second embodiment, a silicon dioxide (SiO ₂ ) film, which is a metal dissolution prevention film protective film (dissolution prevention film protection film), is formed by a dry film formation method such as a sputtering method. Although the film is formed, the film may be formed by a wet film formation method.

  Further, on the tapered surface of the transmission optical element according to the second embodiment, an adhesion enhancing film, a metal dissolution preventing film (dissolution preventing film), a metal dissolution preventing film protective film (dissolution preventing film protecting film) However, only a metal dissolution prevention film (dissolution prevention film) may be formed. Further, an adhesion strengthening film and a metal dissolution preventing film (dissolution preventing film) may be formed, and a metal dissolution preventing film (dissolution preventing film) and a metal dissolution preventing film protective film (dissolution preventing film protecting film). ) May be formed.

  In the projection exposure apparatus according to the second embodiment, the transmissive optical element 32 closest to the wafer W is formed of fluorite, and an adhesion enhancing film, a metal dissolution preventing film ( Dissolution prevention film) and metal dissolution prevention film protection film (dissolution prevention film protection film) are formed. The transmission optical element 4 closest to the wafer W is formed of quartz glass, and the adhesion is enhanced on the tapered surface. A film, a metal dissolution prevention film (dissolution prevention film), and a metal dissolution prevention film protective film (dissolution prevention film protection film) may be formed.

  In the second embodiment, the number and shape of the nozzles are not particularly limited. For example, the liquid 7 may be supplied or recovered with two pairs of nozzles on the long side of the tip 32A. Good. In this case, the discharge nozzle and the inflow nozzle may be arranged side by side so that the liquid 7 can be supplied and recovered from either the + X direction or the −X direction. Good.

When F ₂ laser light is used as exposure light, a fluorine-based liquid such as fluorine-based oil or perfluorinated polyether (PFPE) that can transmit the F ₂ laser light may be used as the liquid.

  In each of the above-described embodiments, the metal dissolution preventing film (dissolution preventing film) is formed on the tapered surface of the transmission optical element on the wafer side of the projection optical system. A metal dissolution preventing film (dissolution preventing film) may be formed on a surface other than the tapered surface of the element.

  Further, in each of the above-described embodiments, a metal dissolution preventing film made of gold (Au), that is, a film formed of metal, is formed on the tapered surface of the transmission optical element on the wafer side of the projection optical system. However, a dissolution preventing film composed of a film formed of a substance having a solubility in water of 2 ppt or less or a substance having a filling density of 95% or more may be formed.

  Further, in each of the above-described embodiments, an adhesion strengthening film, a metal dissolution prevention film (dissolution prevention film), and a metal dissolution prevention film protective film (dissolution prevention film protection film) are formed by sputtering. Alternatively, the film may be formed by vacuum deposition or CVD.

In each of the above-described embodiments, a magnesium fluoride (MgF ₂ ) film is formed on the wafer-side tip of the transmission optical element, but instead of this, lanthanum fluoride (LaF ₃ ), strontium fluoride (SrF ₂ ), yttrium fluoride (YF ₃ ), ruthenium fluoride (LuF ₃ ), hafnium fluoride (HfF ₄ ), neodymium fluoride (NdF ₃ ), gadolinium fluoride (GdF ₃ ), ytterbium fluoride (YbF _3), dysprosium fluoride (DyF _3), aluminum fluoride (AlF _3), cryolite (Na ₃ AlF _6), chiolite (5NaF · 3AlF _3), aluminum oxide (Al ₂ O _3), silicon dioxide ( SiO ₂ ), titanium dioxide (TiO ₂ ), magnesium oxide (MgO), hafnium dioxide (HfO ₂ ), chromium oxide (Cr ₂ O ₃ ), zirconium dioxide (ZrO ₂ ), tantalum pentoxide (Ta ₂ O ₅ ) and pentafluoride film or an oxide composed of at least one in the niobium oxide (Nb ₂ O ₅₎ Film may be deposited.

In each of the above-described embodiments, a magnesium fluoride (MgF ₂ ) film is formed on the front end of the transmission optical element on the wafer side by vacuum deposition, but instead of this, ion beam assisted deposition, gas At least one of cluster ion beam assisted deposition, ion plating, ion beam sputtering, magnetron sputtering, bias sputtering, ECR sputtering, RF sputtering, thermal CVD, plasma CVD, and photo CVD You may form into a film by the film-forming method.

When a fluoride film is formed on the front end of the transmissive optical element on the wafer side, vacuum deposition, ion beam assisted deposition, gas cluster ion beam assisted deposition, ion plating are the most suitable film formation methods. Law. However, magnesium fluoride (MgF ₂ ) and yttrium fluoride (YF ₃ ) may be formed by sputtering. Further, when an oxide film is formed on the front end portion of the transmissive optical element on the wafer side, all the above-described film forming methods can be used.

In addition, a fluoride film or an oxide film, particularly lanthanum fluoride (LaF ₃ ), which is formed at the tip of the transmission optical element on the wafer side, uses fluorite whose crystal orientation is the (111) plane as the base of the optical element. When the material is used, heteroepitaxial growth is performed by forming a film on the film forming surface. In this case, the formed dissolution preventing film is very dense and has a crystal structure with very few defects.

  Next, an exposure apparatus according to a third embodiment of the present invention will be described with reference to the drawings. The exposure apparatus according to this embodiment is an immersion exposure apparatus to which an immersion method is applied in order to improve the resolution by substantially shortening the exposure wavelength and substantially increase the depth of focus. FIG. 9 shows the first optical element LS1 closest to the image plane of the projection optical system PL, the first optical element LS1, among the optical elements formed of a plurality of fluorites constituting the projection optical system PL of the exposure apparatus according to the present embodiment. It is a figure which shows 2nd optical element LS2 etc. which are close to the image surface of projection optical system PL after 1 optical element LS1.

  This exposure apparatus fills the space between the lower surface T1 of the first optical element LS1 closest to the image plane of the projection optical system PL and the substrate P among the plurality of optical elements constituting the projection optical system PL with the first liquid LQ1. A first liquid immersion mechanism is provided. The substrate P is provided on the image plane side of the projection optical system PL, and the lower surface T1 of the first optical element LS1 is disposed so as to face the surface of the substrate P. The first liquid immersion mechanism includes a first liquid supply mechanism 90 that supplies the first liquid LQ1 between the lower surface T1 of the first optical element LS1 and the substrate P, and a first liquid supplied by the first liquid supply mechanism 90. And a first liquid recovery mechanism 91 that recovers the liquid LQ1.

  The exposure apparatus also includes a second liquid LQ2 for filling a space between the first optical element LS1 and the second optical element LS2 close to the image plane of the projection optical system PL after the first optical element LS1. An immersion mechanism is provided. The second optical element LS2 is disposed above the first optical element LS1, and the upper surface T2 of the first optical element LS1 is disposed so as to face the lower surface T3 of the second optical element LS2. The second liquid immersion mechanism includes a second liquid supply mechanism 92 that supplies the second liquid LQ2 between the first optical element LS1 and the second optical element LS2, and a second liquid supply mechanism 92 that is supplied by the second liquid supply mechanism 92. And a second liquid recovery mechanism 93 that recovers the liquid LQ2.

  The lens barrel PK is provided with a facing surface 89 that faces the peripheral region of the upper surface T2 of the first optical element LS1. A first seal member 94 is provided between the peripheral area of the upper surface T <b> 2 and the facing surface 89. The first seal member 94 is composed of, for example, an O-ring (for example, “Kalrez” manufactured by DuPont Dow) or a C-ring. The first seal member 94 prevents the second liquid LQ2 disposed on the upper surface T2 from leaking out to the outside of the upper surface T2, and thus from the lens barrel PK. A second seal member 95 is provided between the side surface C2 of the second optical element LS2 and the inner side surface PKC of the lens barrel PK. The second seal member 95 is constituted by, for example, a V ring. The second seal member 95 restricts the second fluid LQ2, the moist gas generated by the second fluid LQ2 and the like from flowing above the second optical element LS2 inside the lens barrel PK.

  A third seal member 96 is provided between the side surface C1 of the first optical element LS1 and the inner side surface PKC of the barrel PK. The third seal member 96 is constituted by, for example, a V ring. The third seal member 96 restricts the first fluid LQ1, the moist gas generated by the first fluid LQ1, and the like from flowing above the first optical element LS1 inside the lens barrel PK.

  On the side surface (tapered surface) C1 of the first optical element LS1 and the side surface (tapered surface) C2 of the second optical element LS2, a light shielding film made of gold (Au) with a thickness of 150 nm is formed. Accordingly, exposure light and exposure from the wafer are applied to the first seal member 94, the second seal member 95, and the third seal member 96 provided on the periphery of the tapered surface of the transmission optical element on the substrate side of the projection optical system by the light shielding film. Irradiation of light reflected light can be prevented, and deterioration of the seal member can be prevented.

In the third embodiment, the side surface (tapered surface) C1 of the first optical element LS1 and the side surface (tapered surface) C2 of the second optical element LS2 are made of a metal film using gold (Au). A light-shielding film is formed, but the light-shielding film made of metal film is gold (Au), platinum (Pt), silver (Ag), nickel (Ni), tantalum (Ta), tungsten (W), palladium (Pd) The film may be formed of at least one of molybdenum (Mo), titanium (Ti), and chromium (Cr). Further, the light shielding film may be formed of a metal oxide film. In this case, the metal oxide film is composed of zirconium dioxide (ZrO ₂ ), hafnium dioxide (HfO ₂ ), titanium dioxide (TiO ₂ ), tantalum pentoxide (Ta ₂ O ₅ ), silicon oxide (SiO), and chromium oxide ( It is constituted by a film formed of at least one of Cr ₂ O ₃ ).

  In each of the above embodiments, the space between the wafer surface and the transmission optical element formed by the fluorite on the wafer side of the projection optical system is filled with liquid. You may make it interpose a liquid in a part between transmission optical elements formed with the fluorite on the wafer side.

  In each of the above-described embodiments, pure water is used as the liquid 7. However, the liquid is not limited to pure water, and has a high refractive index as much as possible because it is transmissive to exposure light. A thing (for example, cedar oil) stable to the photoresist applied to the surface can also be used.

  In each of the above-described embodiments, an exposure apparatus that locally fills a space between the projection optical system PL and the wafer (substrate) W is disclosed in Japanese Patent Laid-Open No. 6-124873. An immersion exposure apparatus for moving a stage holding a substrate to be exposed in the liquid tank, or a liquid tank having a predetermined depth on the stage as disclosed in JP-A-10-303114. The present invention is also applicable to an immersion exposure apparatus that is formed and holds a substrate therein.

  Further, according to the present invention, as disclosed in JP-A-10-163099, JP-A-10-214783, JP-T 2000-505958, etc., substrates to be processed such as wafers are separately placed. The present invention can also be applied to a twin stage type exposure apparatus having two stages that can move independently in the XY directions.

  FIG. 10 is a diagram illustrating a configuration of the transmissive optical element 50 according to the first embodiment. As shown in FIG. 10, a tantalum (Ta) film having a thickness of 10 nm is formed on a substrate of fluorite 52 by sputtering, and an adhesion enhancing film 53 is formed. The adhesion enhancing film 53 functions to improve the adhesion between the fluorite 52 and the metal film 54 formed on the surface of the adhesion enhancing film 53. Moreover, although the film thickness required in order to strengthen adhesive force is 10 nm or more, the effect as adhesive force can be acquired also in the film thickness of 3-5 nm.

  Next, a 200 nm thick metal film 54 made of gold (Au) is formed on the surface of the adhesion enhancing film 53 as a dissolution protective film for preventing dissolution in water by sputtering.

  Here, the density of the metal film 54 can be obtained from the critical angle of X-ray diffraction, and when formed by sputtering, the filling density of the metal film 54 is 97% or more. Further, the solubility of the metal film 54 in water is 1 ppt or less when formed by sputtering.

Next, on the surface of the metal film 54 on the substrate of the fluorite 52 heated to 200 ° C., silicon dioxide (SiO 2) is used as a dissolution preventing film protective film for improving the mechanical strength of the metal film 54 by using a sputtering method. ₂ ) A film 55 is formed to a thickness of 50 nm. Here, the heating film formation in which the fluorite 52 substrate is heated to about 200 ° C. can form a film having higher mechanical strength than the non-heating film formation. The heating for forming the silicon dioxide (SiO ₂ ) film 55 is to uniformly heat the entire fluorite substrate in order to prevent damage and surface shape change due to thermal shock of the fluorite substrate having a large coefficient of thermal expansion. To do. Moreover, when heating or cooling a fluorite substrate, it is necessary to heat or cool at a rate of 50 ° C./hour or less. The silicon dioxide (SiO ₂ ) film 55 has minute defects that allow water clusters to pass therethrough. However, since the metal film 54 is insoluble in water, water does not enter the substrate of the fluorite 52.

An experiment was performed using the transmission optical element 50. FIG. 11 is a diagram showing a configuration of the tester 80 according to this embodiment. As shown in FIG. 11, the tester 80 includes a sample holder 81, a circulation pump 82, a heavy water supply device 83, and a buffer tank 84. One surface of the sample holder 81 is released, and an O-ring 85 is provided on the release surface. The surface on which the adhesion enhancing film 53, the metal film 54, and the silicon dioxide (SiO ₂ ) film 55 of the transmission optical element 50 are formed on the release surface of the sample holder 81 is sealed by an O-ring 85. The heavy water supplied from the heavy water supply device 83 by the circulation pump 82 flows into the sample holder 81 through the buffer tank 84. Here, the buffer tank 84 is installed so that the vibration of the circulation pump 82 is not transmitted to the sample holder 81. Further, by flowing heavy water (D ₂ O) instead of pure water (H ₂ O), it is possible to measure the amount of heavy water that permeates in the depth direction from the surface of the transmission optical element 50 after the water resistance test. it can.

The tester 80 was set so that the moving speed of heavy water on the transmission optical element 50 was 50 cm / second, and a 30-day water resistance test was performed. As a result, the film formed on the surface of the transmissive optical element 50 was not peeled off, and no change was observed in the appearance of the transmissive optical element 50. Moreover, as a result of evaluating the penetration of heavy water in the depth direction from the surface of the transmission optical element 50 by secondary ion mass spectrometry (SIMS), heavy water penetrates the silicon dioxide (SiO ₂ ) film 55. However, heavy water did not penetrate into the metal film 54.

  FIG. 12 is a diagram illustrating a configuration of the transmission optical element 58 according to the second embodiment. As shown in FIG. 12, a 200 nm thick metal film 60 made of gold (Au) is formed on the fluorite 59 substrate by sputtering as a dissolution protective film for preventing dissolution in water. Here, the density of the metal film 60 can be obtained from the critical angle of X-ray diffraction. When the film is formed by sputtering, the filling density of the metal film 60 is 97% or more. Further, the solubility of the metal film 60 in water is 1 ppt or less when formed by sputtering.

Next, on the surface of the metal film 60 on the substrate of the fluorite 59 heated to 200 ° C., silicon dioxide (SiO 2) as a dissolution preventing film protective film for improving the mechanical strength of the metal film 60 by using a sputtering method. ₂ ) A film 61 is formed to a thickness of 50 nm. Here, the heating film formation in which the substrate of fluorite 59 is heated to about 200 ° C. can form a film having higher mechanical strength than the non-heating film formation. In addition, the heating when forming the silicon dioxide (SiO ₂ ) film 61 uniformly heats the entire fluorite substrate in order to prevent the fluorite substrate having a high coefficient of thermal expansion from being damaged due to thermal shock and the change of the surface shape. To do. Moreover, when heating or cooling a fluorite substrate, it is necessary to heat or cool at a rate of 50 ° C./hour or less. The silicon dioxide (SiO ₂ ) film 61 has minute defects that allow water clusters to pass through. However, since the metal film 60 is insoluble in water, water does not enter the substrate of the fluorite 59.

An experiment was performed using the transmission optical element 58. Similarly to Example 1, the moving speed of heavy water on the transmission optical element 58 was set to 50 cm / sec using the tester 80 shown in FIG. As a result, the film formed on the surface of the transmission optical element 58 was not peeled off, and no change was observed in the appearance of the transmission optical element 58. In addition, as a result of evaluating the penetration of heavy water in the depth direction from the surface of the transmission optical element 58 by secondary ion mass spectrometry (SIMS), heavy water penetrates the silicon dioxide (SiO ₂ ) film 61. However, heavy water did not penetrate into the metal film 60.

  FIG. 13 is a diagram illustrating a configuration of the transmission optical element 65 according to the third embodiment. As shown in FIG. 13, a tantalum (Ta) film having a thickness of 10 nm is formed on a substrate of fluorite 66 by sputtering, and an adhesion strengthening film 67 is formed. The adhesion enhancing film 67 functions to improve the adhesion between the fluorite 66 and the metal film 68 formed on the surface of the adhesion enhancing film 67. Moreover, although the film thickness required in order to strengthen adhesive force is 10 nm or more, the effect as adhesive force can be acquired also in the film thickness of 3-5 nm.

  Next, a 200 nm thick metal film 68 made of gold (Au) is formed on the surface of the adhesion strengthening film 67 as a dissolution protective film for preventing dissolution in water by sputtering.

Here, the density of the metal film 67 can be obtained from the critical angle of X-ray diffraction, and when the film is formed by sputtering, the filling density of the metal film 67 is 97% or more. The solubility of the metal film 67 in water is 1 ppt or less when formed by sputtering.

  An experiment was performed using the transmission optical element 65. Similarly to Example 1, the moving speed of heavy water on the transmission optical element 65 was set to 50 cm / second using the tester 80 shown in FIG. As a result, the film formed on the surface of the transmissive optical element 65 did not peel off, and no change was observed in the appearance of the transmissive optical element 65. Moreover, as a result of evaluating penetration of heavy water in the depth direction from the surface of the transmission optical element 65 by secondary ion mass spectrometry (SIMS), heavy water did not penetrate.

  In each of the above-described embodiments, the sputtering method is used as the film forming method. However, the adhesion enhancing film, the metal film, and the anti-dissolving film protective film may be formed by using a vacuum evaporation method or a CVD method. .

Comparative example

FIG. 14 is a diagram illustrating a configuration of a transmission optical element 70 according to a comparative example. As shown in FIG. 14, a 200 nm silicon dioxide (SiO ₂ ) film 72 is formed on the fluorite 71 substrate on the fluorite 71 substrate heated to 200 ° C. by sputtering. In addition, the heating when forming the silicon dioxide (SiO ₂ ) film 72 is performed by heating the entire fluorite substrate uniformly in order to prevent the fluorite substrate having a large coefficient of thermal expansion from being damaged due to thermal shock and the change in surface shape. To do. Moreover, when heating or cooling a fluorite substrate, it is necessary to heat or cool at a rate of 50 ° C./hour or less.

An experiment was performed using the transmission optical element 70. Similarly to Example 1, the moving speed of heavy water on the transmission optical element 70 was set to 50 cm / second using the tester 80 shown in FIG. As a result, the silicon dioxide (SiO ₂ ) film 72 has minute defects that allow water clusters to pass therethrough, so that heavy water passes through the film formed on the surface of the transmission optical element 70, and the heavy water that has passed therethrough. However, since the surface of fluorite 71 was etched, a large amount of etch pits were generated.

  According to the transmission optical element concerning Example 1-Example 3, when compared with the transmission optical element concerning a comparative example, penetration and erosion of heavy water can be prevented without changing the optical characteristic.

  Next, the performance evaluation test and test results of the light shielding film in the third embodiment will be described. First, an optical element A in which a gold film having a thickness of 150 nm was formed on a quartz glass substrate and an optical element B of quartz glass itself were prepared. Next, the transmittance at the ArF wavelength of the optical element A and the optical element B was measured.

The measurement result of optical element A is 0.0% (average value measured five times)
The measurement result of optical element B is 90.8% (average value measured five times)
By forming a gold film, it was possible to completely shield the light. Therefore, it is possible to prevent the seal member from being deteriorated by forming a light shielding film on the tapered surface of the optical element.

  R ... reticle, PL ... projection optical system, W ... wafer, 1 ... illumination optical system, 4, 32 ... transmission optical element, 4A, 32A ... tip of transmission optical element on wafer side, 4B, 32B ... transmission optical element Tapered surface, 5 ... Liquid supply device, 6 ... Liquid recovery device, 7 ... Liquid, 9 ... Z stage, 10 ... XY stage, 14 ... Main control system, 21, 22 ... Supply pipe, 21a-21c, 22a-22c ... Discharge nozzle, 23, 24 ... recovery tube, 23a, 23b, 24a, 24b ... inflow nozzle, 80 ... tester, 81 ... sample holder, 82 ... circulating pump, 83 ... heavy water supply device, 84 ... buffer tank, 85 ... O ring.

Claims (6)

Used in an exposure apparatus that illuminates a mask with an exposure beam, transfers the mask pattern onto a substrate via a projection optical system, and interposes a predetermined liquid between the surface of the substrate and the projection optical system. An optical element,
An optical element, wherein a light shielding film is formed on a tapered surface of a transmission optical element on the substrate side of the projection optical system.   The optical element according to claim 1, wherein the light shielding film is formed of a metal film or a metal oxide film. The metal film includes gold (Au), platinum (Pt), silver (Ag), nickel (Ni), tantalum (Ta), tungsten (W), palladium (Pd), molybdenum (Mo), titanium (Ti) and The metal oxide film is composed of at least one of chromium (Cr), and the metal oxide film includes zirconium dioxide (ZrO ₂ ), hafnium dioxide (HfO ₂ ), titanium dioxide (TiO ₂ ), and tantalum pentoxide. _3. The optical element according to claim 2, comprising a film formed of at least one of (Ta ₂ O ₅ ), silicon oxide (SiO), and chromium oxide (Cr ₂ O ₃ ). An exposure apparatus that illuminates a mask with an exposure beam, transfers a pattern of the mask onto a substrate via a projection optical system, and interposes a predetermined liquid between the surface of the substrate and the projection optical system. ,
An exposure apparatus, wherein a light shielding film is formed on a tapered surface of a transmission optical element on the substrate side of the projection optical system.   5. The exposure apparatus according to claim 4, wherein the light shielding film is formed of a metal film or a metal oxide film. The metal film includes gold (Au), platinum (Pt), silver (Ag), nickel (Ni), tantalum (Ta), tungsten (W), palladium (Pd), molybdenum (Mo), titanium (Ti) and The metal oxide film is composed of at least one of chromium (Cr), and the metal oxide film includes zirconium dioxide (ZrO ₂ ), hafnium dioxide (HfO ₂ ), titanium dioxide (TiO ₂ ), and tantalum pentoxide. 6. The exposure apparatus according to claim 5, wherein the exposure apparatus comprises a film formed of at least one of (Ta ₂ O ₅ ), silicon oxide (SiO), and chromium oxide (Cr ₂ O ₃ ).

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