JP4168880B2 - Immersion solution - 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 immersion solution used in a projection exposure apparatus using an immersion method.

  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

  When a step-and-repeat type projection exposure apparatus is configured by this immersion type projection exposure apparatus, the projection optical system and the liquid come into contact with each other, so that the tip of the projection optical system in contact with the liquid is eroded by the liquid. There is a possibility that the desired optical performance cannot be obtained.

  Further, when a step-and-scan type projection exposure apparatus is constituted by an immersion type projection exposure apparatus, exposure is performed while moving the wafer, so that the projection optical system and the wafer are also moved while the wafer is moved. It must be filled with liquid. Therefore, there is a possibility that the tip of the projection optical system in contact with the liquid may be eroded by the liquid, and a desired optical performance cannot be obtained.

An object of the present invention is to provide an immersion solution that does not erode the tip of a projection optical system in an immersion type projection exposure apparatus.

The immersion solution according to claim 1, wherein the surface of the substrate of the immersion type projection exposure apparatus that illuminates the mask with an exposure beam and transfers the pattern of the mask onto the substrate via a projection optical system, and the projection optics. An immersion solution interposed between an optical element formed of fluorite on the substrate side of the system, wherein the immersion solution contains fluorine ions or fluoride ions.

  According to the immersion solution according to the first aspect, since the optical element formed of fluorite is not eroded, the optical performance of the projection optical system is not changed and the desired optical performance is maintained. be able to.

  Further, the immersion solution according to claim 2 is characterized in that PH is 6 or less. Since the immersion solution according to claim 2 has high acidity, weakly acidic pollutants are not dissolved and optical elements formed by fluorite are not eroded. The desired optical performance can be maintained without changing the optical performance.

Further, the immersion solution according to claim 3 illuminates the mask with an exposure beam and transfers the pattern of the mask onto the substrate via a projection optical system and the surface of the substrate of the immersion type projection exposure apparatus. An immersion solution interposed between the projection optical system and an optical element formed of fluorite on the substrate side, wherein the immersion solution contains ammonium ions.

  According to the immersion solution of the third aspect, since the optical element formed of fluorite is not eroded, the optical performance of the projection optical system is not changed and the desired optical performance is maintained. be able to.

  Further, the immersion solution according to claim 4 is characterized in that PH is 8 or more. The immersion solution according to claim 4 has a high alkalinity and thus does not dissolve weak alkaline contaminants and does not erode optical elements formed by fluorite. The desired optical performance can be maintained without changing the optical performance.

Further, the immersion solution according to claim 5 illuminates the mask with an exposure beam and transfers the pattern of the mask onto the substrate via a projection optical system and the surface of the substrate of the immersion type projection exposure apparatus. a liquid immersion solution interposed between the optical element formed by fluorite of the substrate side of the projection optical system, for the immersion solution, characterized in that it is constituted by the buffer solution.

  According to the immersion solution of claim 5, even when an acidic or alkaline contaminant is mixed from the outside, the pH change of the solution can be prevented and the optical element formed by fluorite is eroded. Therefore, the desired optical performance can be maintained without changing the optical performance of the projection optical system.

  According to the immersion solution of the present invention, since the optical element formed of fluorite does not erode, the optical performance of the projection optical system is not changed, and the desired optical performance can be maintained. .

  Hereinafter, an immersion exposure machine system including a projection exposure apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an immersion exposure machine system including a step-and-repeat projection exposure apparatus according to the first embodiment. In FIG. 1, exposure light (exposure light) composed of ultraviolet pulse light having a wavelength of 193 nm emitted from an illumination optical system 1 including an ArF excimer laser light source, an optical integrator (homogenizer), a field stop, a condenser lens, and the like as an exposure light source. The beam IL illuminates a pattern provided on the reticle (mask) R. The reticle R pattern is a wafer coated with a photoresist at a predetermined projection magnification β (β is, for example, 1/4, 1/5, etc.) via a telecentric projection optical system PL on both sides (or one side on the wafer W side). The projection is reduced and projected onto an exposure area on the (substrate) W.

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. Hereinafter, taking the Z axis parallel to the optical axis AX of the projection optical system PL, taking the Y axis perpendicular to the paper surface of FIG. 1 in the plane perpendicular to the Z axis, and taking the X axis parallel to the paper surface of FIG. explain.

  The reticle R is held on the 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 two-dimensional position and rotation angle of the reticle stage RST are measured in real time by a laser interferometer (not shown), and the main control system 14 positions the reticle R based on the measured values.

  On the other hand, the wafer W is fixed on a Z stage 9 for controlling the focus position (position in the Z direction) and the tilt angle of the wafer W 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 XY stage 10 is placed on a base 11. The Z stage 9 controls the focus position (position in the Z direction) and the tilt angle of the wafer W, and adjusts 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. The XY stage 10 positions the wafer W in the X direction and the Y direction. The two-dimensional position and rotation angle of the Z stage 9 (wafer W) are measured in real time by the laser interferometer 13 as the position of the movable mirror 12. Based on this measurement result, control information is sent from the main control system 14 to the wafer stage drive system 15, and based on this, the wafer stage drive system 15 controls the operations of the Z stage 9 and the XY stage 10. During exposure, each shot area on the wafer W is sequentially moved to the exposure position, and the operation of exposing the pattern image of the reticle R is repeated in a step-and-repeat manner.

  In this projection exposure apparatus, an immersion method is applied to improve the resolution by substantially shortening the exposure wavelength. Therefore, at least during the transfer of the pattern image of the reticle R onto the wafer W, the immersion solution is provided between the surface of the wafer W and the front end surface (lower surface) of the optical element 4 on the wafer side of the projection optical system PL. Satisfy 7 The projection optical system PL is configured by housing a plurality of optical elements formed of quartz or fluorite in a lens barrel 3. In the projection optical system PL, the optical element 4 closest to the wafer W is formed of fluorite, and only the optical element 4 is configured to come into contact with the immersion solution 7. As a result, corrosion of the lens barrel 3 made of metal is prevented. Here, the immersion solution 7 is a solution containing fluorine ions or fluoride ions, and the pH is adjusted to 6 or less.

  The immersion solution 7 is temperature-controlled on the wafer W via a predetermined discharge nozzle or the like by a liquid supply device 5 including a tank for storing the immersion solution, a pressure pump, a temperature control device, and the like. The liquid is recovered from the wafer W through a predetermined inflow nozzle or the like by the liquid recovery device 6 including a tank for storing the immersion solution and a suction pump. The temperature of the immersion solution 7 is set to be approximately the same as the temperature in the chamber in which the projection exposure apparatus of this example is accommodated, for example. The discharge nozzle 21a has a narrow tip so that the tip of the optical element 4 of the projection optical system PL is sandwiched in the X direction, and two inflow nozzles 23a and 23b (see FIG. 2) have a wide tip. The discharge nozzle 21 a is connected to the liquid supply device 5 via the supply pipe 21, and the inflow nozzles 23 a and 23 b are connected to the liquid recovery device 6 via the recovery pipe 23.

  Further, the pair of discharge nozzles 21a and the pair of inflow nozzles 23a and 23b are rotated by approximately 180 °, and the two pairs of nozzles disposed so as to sandwich the tip of the optical element 4 in the Y direction. A discharge nozzle and an inflow nozzle are also arranged.

  FIG. 2 shows the positional relationship between the tip portion 4A and the wafer W of the optical element 4 of the projection optical system PL shown in FIG. 1, and two pairs of discharge nozzles and inflow nozzles that sandwich the tip portion 4A in the X direction. In FIG. 2, the discharge nozzle 21a is arranged on the + X direction side of the tip 4A, and the inflow nozzles 23a and 23b are arranged on the −X direction side. The inflow nozzles 23a and 23b are arranged in a fan-like shape with respect to an axis that passes through the center of the tip portion 4A and is parallel to the X axis. Then, another pair of discharge nozzles 22a and inflow nozzles 24a and 24b are arranged in an arrangement in which the pair of discharge nozzles 21a and the inflow nozzles 23a and 23b are rotated by approximately 180 °, and the discharge nozzle 22a passes through the supply pipe 22. The inflow nozzles 24 a and 24 b are connected to the liquid recovery apparatus 6 via the recovery pipe 24.

  FIG. 3 shows the positional relationship between the tip portion 4A of the optical element 4 of the projection optical system PL of FIG. 1 and two pairs of discharge nozzles and inflow nozzles that sandwich the tip portion 4A in the Y direction. In FIG. 3, the discharge nozzle 27 a is disposed on the + Y direction side of the front end portion 4 </ b> A, and the inflow nozzles 29 a and 29 b are disposed on the −Y direction side, and the discharge nozzle 27 a is connected to the liquid supply device 5 via the supply pipe 27. The inflow nozzles 29 a and 29 b are connected to the liquid recovery apparatus 6 through the recovery pipe 29. In addition, another pair of discharge nozzles 28a and inflow nozzles 30a and 30b are disposed in an arrangement in which the pair of discharge nozzles 27a and inflow nozzles 29a and 29b are rotated by approximately 180 °, and the discharge nozzle 28a passes through the supply pipe 28. The inflow nozzles 30 a and 30 b are connected to the liquid recovery apparatus 6 via the recovery pipe 30. The liquid supply device 5 supplies a temperature-controlled immersion solution between the tip 4A of the optical element 4 and the wafer W via at least one of the supply pipes 21, 22, 27, and 28, and recovers the liquid. The apparatus 6 recovers the immersion solution via at least one of the recovery tubes 23, 24, 29, 30.

  Next, a method for supplying and collecting the immersion solution 7 will be described. In FIG. 2, when the wafer W is step-moved in the direction of the arrow 25A indicated by the solid line (−X direction), the body supply device 5 uses the supply tube 21 and the discharge nozzle 21a to move the tip of the optical element 4 An immersion solution 7 is supplied between 4A and the wafer W. Then, the liquid recovery apparatus 6 recovers the immersion solution 7 from the wafer W via the recovery pipe 23 and the inflow nozzles 23a and 23b. At this time, the immersion solution 7 flows on the wafer W in the direction of the arrow 25B (the −X direction), and the space between the wafer W and the optical element 4 is stably filled with the immersion solution 7.

  On the other hand, when the wafer W is stepped in the direction of the arrow 26A indicated by the two-dot chain line (+ X direction), the liquid supply apparatus 5 uses the supply pipe 22 and the discharge nozzle 22a to tip the optical element 4A 4A. The immersion solution 7 is supplied between the wafer W and the liquid W, and the liquid recovery device 6 recovers the immersion solution 7 using the recovery pipe 24 and the inflow nozzles 24a and 24b. At this time, the immersion solution 7 flows on the wafer W in the direction of the arrow 26B (+ X direction), and the space between the wafer W and the optical element 4 is filled with the immersion solution 7. As described above, in the projection exposure apparatus of this example, since two pairs of discharge nozzles and inflow nozzles which are inverted with respect to each other in the X direction are provided, the wafer W is moved in either the + X direction or the −X direction. However, the space between the wafer W and the optical element 4 can be stably filled with the immersion solution 7.

  Further, since the immersion solution 7 flows on the wafer W, there is an advantage that even if foreign matter is adhered on the wafer W, the foreign matter can be washed away by the immersion solution 7. In addition, since the immersion solution 7 is adjusted to a predetermined temperature by the liquid supply device 5, the temperature of the surface of the wafer W is adjusted, the overlay accuracy due to the thermal expansion of the wafer due to the heat generated during exposure, etc. Can be prevented. Therefore, even when there is a time difference between alignment and exposure as in EGA (Enhanced Global Alignment), it is possible to prevent the overlay accuracy from being lowered due to thermal expansion of the wafer. . Further, in the projection exposure apparatus of this example, since the immersion solution 7 flows in the same direction as the direction in which the wafer W is moved, the immersion solution that has absorbed foreign matter and heat is applied to the tip 4A of the optical element 4. It can collect | recover, without making it stay on the exposure area | region directly under.

  Further, when the wafer W is moved stepwise in the Y direction, the immersion solution 7 is supplied and recovered from the Y direction. That is, when the wafer is stepped in the direction of the arrow 31A indicated by the solid line in FIG. 3 (−Y direction), the liquid supply device 5 supplies the immersion solution via the supply pipe 27 and the discharge nozzle 27a. The liquid recovery apparatus 6 recovers the immersion solution using the recovery pipe 29 and the inflow nozzles 29a and 29b, and the immersion solution moves in the direction of the arrow 31B on the exposure area immediately below the tip 4A of the optical element 4. It flows in (−Y direction). In addition, when the wafer is moved stepwise in the + Y direction, the supply pipe 28, the discharge nozzle 28a, the recovery pipe 30 and the inflow nozzles 30a and 30b are used to supply and recover the immersion solution. The solution flows in the + Y direction on the exposure region immediately below the tip portion 4A. As a result, similarly to the case where the wafer W is moved in the X direction, the wafer W is moved between the front end portion 4A of the optical element 4 and the wafer W regardless of whether the wafer W is moved in the + Y direction or the −Y direction. Can be filled with the immersion solution 7.

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

Next, a method for controlling the supply amount and the recovery amount of the immersion solution 7 will be described. FIG. 4 shows the supply and recovery of the immersion solution between the optical element 4 of the projection optical system PL and the wafer W. In FIG. 4, the wafer W is in the direction of the arrow 25A (the -X direction). The immersion solution 7 supplied from the discharge nozzle 21a flows in the direction of the arrow 25B (−X direction) and is collected by the inflow nozzles 23a and 23b. In order to keep the amount of the immersion solution 7 existing between the optical element 4 and the wafer W constant even during the movement of the wafer W, in this example, the supply amount Vi (m ³ / s) and the recovery of the immersion solution 7 are collected. The supply amount Vi of the immersion solution 7 and the recovery amount Vo are adjusted so as to be equal to the amount Vo (m ³ / s) and proportional to the moving speed v of the XY stage 10 (wafer W). That is, the main control system 14 determines the supply amount Vi and the recovery amount Vo of the immersion solution 7 by the following equations.

Vi = Vo = D · v · d (1)
Here, as shown in FIG. 1, D is the diameter (m) of the tip of the optical element 4, v is the moving speed (m / s) of the XY stage 10, and d is the working distance (working distance) of the projection optical system PL. ) (M). Since the speed v when the XY stage 10 is moved stepwise is set by the main control system 14 and D and d are input in advance, supply of the immersion solution 7 based on the equation (1) By adjusting the amount Vi and the recovery amount Vo, the immersion solution 7 is always filled between the optical element 4 and the wafer W in FIG.

  Note that the working distance d of the projection optical system PL is desirably as small as possible in order to allow the immersion solution 7 to stably exist between the projection optical system PL and the wafer W. However, since the surface of the wafer W may come into contact with the optical element 4 if the working distance d is too small, it is necessary to have a certain margin. Therefore, the working distance d is set to about 2 mm as an example.

  In the projection exposure apparatus according to the first embodiment, since the immersion solution is a solution containing fluorine ions or fluoride ions, the optical element 4 formed of fluorite is not eroded. Further, since the acidity of the immersion solution is high, weakly acidic contaminants do not dissolve, and the optical element 4 formed of fluorite is not eroded by the contaminants. Therefore, the desired optical performance can be maintained without changing the optical performance of the projection optical system, so that the operation of the apparatus is not stopped to replace the eroded optical element, and the final product is made efficient. Can be produced well. In addition, since the optical element on the wafer side of the projection optical system can be prevented from being eroded by the immersion solution, the optical characteristics of the projection optical system can be stabilized, and the quality of the final product produced can be improved. It can be stabilized.

  Next, an immersion exposure system that includes a projection exposure apparatus according to the second embodiment of the present invention will be described. The projection exposure apparatus according to the second embodiment uses pure water as the immersion solution and circulates the immersion solution between the surface of the wafer W and the optical element 4 on the substrate side of the projection optical system PL. A circulation system is provided, and an ion exchange member and a filter are installed in the circulation system. Other configurations are the same as those of the immersion exposure apparatus system including the projection exposure apparatus according to the first embodiment.

  As shown in FIG. 5, a membrane filter 40 and an ion exchange member 42 having a filter pore diameter of 1 μm or less are arranged in the collection tube 23, and a membrane filter 41 and an ion exchange member 42 having a filter pore diameter of 1 μm or less are arranged in the collection tube 24. An exchange member 43 is arranged. Further, as shown in FIG. 6, a membrane filter 44 and an ion exchange member 46 having a filter pore diameter of 1 μm or less are arranged in the collection tube 29, and a membrane filter 45 having a filter pore diameter of 1 μm or less is arranged in the collection tube 30. An ion exchange member 47 is disposed.

  Therefore, immediately before the immersion solution is recovered by the liquid recovery device 6, the particles and solids present in the immersion solution can be removed by the membrane filters 40, 41, 44, 45. It is possible to prevent the optical element from being damaged by the immersion solution. Further, since ions dissolved from the outside can be removed by the ion exchange members 42, 43, 46, and 47, the pH of the solution can be kept constant, and the optical element is prevented from being eroded by the immersion solution. be able to. Thereby, the change of the optical performance of a projection optical system can be prevented, and desired optical performance can be maintained. Pure water can be easily obtained in large quantities at a semiconductor manufacturing factory or the like, and has the advantage that it does not adversely affect the photoresist, optical lenses, etc. on the wafer. In addition, pure water has no adverse effect on the environment, and since the impurity content is extremely low, it can be expected to clean the surface of the wafer.

  Next, an immersion exposure system including a projection exposure apparatus according to the third embodiment of the present invention will be described. FIG. 7 is a front view showing a lower part of the projection optical system PLA of the step-and-scan projection exposure apparatus according to the third embodiment, the liquid supply apparatus 5, the liquid recovery apparatus 6, and the like. In FIG. 7, the same components as those of 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 lowermost optical element 32 of the lens barrel 3A of the projection optical system PLA is cut into a rectangular shape elongated in the Y direction (non-scanning direction), leaving only the portion of the tip 32A necessary for scanning exposure. It has been. In the projection optical system PLA, the optical element 32 is made of fluorite. At the time of scanning exposure, a pattern image of a part of the reticle is projected onto a rectangular exposure area immediately below the tip 32A, and the reticle (not shown) moves in the −X direction (or + X direction) with respect to the projection optical system PLA. In synchronization with the movement at V, the wafer W moves through the XY stage 10 in the + X direction (or -X direction) at a velocity β · V (β is the projection magnification). 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.

  Also in this example, the immersion solution 7 is filled between the optical element 32 and the surface of the wafer W by applying the immersion method during the scanning exposure. Supply and recovery of the immersion solution 7 are performed by the liquid supply device 5 and the liquid recovery device 6, respectively. The immersion solution 7 is a solution containing fluorine ions or fluoride ions, and the pH is adjusted to 6 or less, as in the first embodiment.

  FIG. 8 shows the positional relationship between the tip 32A of the optical element 32 of the projection optical system PLA and the discharge nozzle and the inflow nozzle for supplying and recovering the immersion solution 7 in the X direction. In FIG. 8, the shape of the tip 32A of the optical element 32 is a rectangle elongated in the Y direction, and there are three on the + X direction side so that the tip 32A of the optical element 32 of the projection optical system PLA is sandwiched in the X direction. Discharge nozzles 21a to 21c are arranged, and two inflow nozzles 23a and 23b are arranged on the −X direction side.

  The discharge nozzles 21 a to 21 c are connected to the liquid supply device 5 via the supply pipe 21, and the inflow nozzles 23 a and 23 b are connected to the liquid recovery device 6 via the recovery pipe 23. Further, the discharge nozzles 22a to 22c and the inflow nozzles 24a and 24b are arranged in an arrangement in which the discharge nozzles 21a to 21c and the inflow nozzles 23a and 23b are rotated by approximately 180 °. The discharge nozzles 21a to 21c and the inflow nozzles 24a and 24b are alternately arranged in the Y direction, the discharge nozzles 22a to 22c and the inflow nozzles 23a and 23b are alternately arranged in the Y direction, and the discharge nozzles 22a to 22c are supply pipes. The inflow nozzles 24 a and 24 b are connected to the liquid recovery apparatus 6 via the recovery pipe 24.

  When scanning exposure is performed by moving the wafer W in the scanning direction (−X direction) indicated by the solid line arrow, the supply pipe 21, the discharge nozzles 21a to 21c, the recovery pipe 23, and the inflow nozzles 23a and 23b are connected. The liquid supply device 5 and the liquid recovery device 6 are used to supply and recover the immersion solution 7, and the immersion solution 7 is caused to flow in the −X direction so as to fill between the optical element 32 and the wafer W. When scanning exposure is performed by moving the wafer W in the direction indicated by the two-dot chain line arrow (+ X direction), the supply pipe 22, the discharge nozzles 22a to 22c, the recovery pipe 24, and the inflow nozzles 24a and 24b are provided. In use, the immersion solution 7 is supplied and recovered, and the immersion solution 7 is caused to flow in the + X direction so as to fill between the optical element 32 and the wafer W. When the wafer W is scanned in either the + X direction or the −X direction by switching the flow direction of the immersion solution 7 according to the scanning direction, the tip 32A of the optical element 32 and the wafer W Can be filled with the immersion solution 7, and high resolution can be obtained.

Further, the supply amount Vi (m ³ / s) and the recovery amount Vo (m ³ / s) of the immersion solution 7 are determined by the following equations.

Vi = Vo = DSY · v · d (2)
Here, DSY is the length (m) of the tip 32A of the optical element 32 in the X direction. Thus, the space between the optical element 32 and the wafer W can be stably filled with the immersion solution 7 even during scanning exposure.

  The number and shape of the nozzles are not particularly limited. For example, the immersion solution 7 may be supplied or recovered with two pairs of nozzles on the long side of the tip 32A. In this case, the discharge nozzle and the inflow nozzle are arranged side by side so that the immersion solution 7 can be supplied and recovered from either the + X direction or the −X direction. May be. When stepping the wafer W in the Y direction, the immersion solution 7 is supplied and recovered from the Y direction as in the first embodiment.

FIG. 9 shows the positional relationship between the tip 32A of the optical element 32 of the projection optical system PLA and the discharge nozzle and inflow nozzle for the Y direction. In FIG. 9, when the wafer is step-moved in the non-scanning direction (−Y direction) orthogonal to the scanning direction, the immersion nozzles 27a and the inflow nozzles 29a and 29b arranged in the Y direction are used for liquid immersion. When the working solution 7 is supplied and recovered, and the wafer is stepped in the + Y direction, the discharge nozzle 28a and the inflow nozzles 30a and 30b arranged in the Y direction are used. Supply and collect. Further, the supply amount Vi of the immersion solution 7 ^(m 3 / s), and the recovery amount Vo ^(m 3 / s) is determined by the following equation.

Vi = Vo = DSX · v · d (3)
Here, DSX is the length (m) in the Y direction of the tip 32A of the optical element 32. Similarly to the first embodiment, when the step movement in the Y direction is performed, the supply amount of the immersion solution 7 is adjusted in accordance with the moving speed v of the wafer W, so that the optical element 32 and the wafer W can be moved. The space can be continuously filled with the immersion solution 7.

  When the wafer W is moved as described above, the immersion solution is allowed to flow in a direction corresponding to the moving direction, so that the immersion solution 7 is used between the wafer W and the tip of the projection optical system PL. You can keep filling.

  In the projection exposure apparatus according to the third embodiment, since the immersion solution is a solution containing fluorine ions or fluoride ions, the optical element 32 formed of fluorite is not eroded. Further, since the acidity of the immersion solution is high, weakly acidic contaminants are not dissolved, and the optical element 32 formed of fluorite is not eroded by the contaminants. Therefore, the desired optical performance can be maintained without changing the optical performance of the projection optical system, so that the operation of the apparatus is not stopped to replace the eroded optical element, and the final product is made efficient. Can be produced well. In addition, since the optical element on the wafer side of the projection optical system can be prevented from being eroded by the immersion solution, the optical characteristics of the projection optical system can be stabilized, and the quality of the final product produced can be improved. It can be stabilized.

  Next, an immersion exposure apparatus system including a projection exposure apparatus according to the fourth embodiment of the present invention will be described. The projection exposure apparatus according to the fourth embodiment uses pure water as the immersion solution, and circulates the immersion solution between the surface of the wafer W and the optical element 4 on the substrate side of the projection optical system PL. A circulation system is provided, and an ion exchange resin and a filter are installed in the circulation system. Other configurations are the same as those of the immersion exposure apparatus system including the projection exposure apparatus according to the third embodiment.

  As shown in FIG. 10, a membrane filter 40 and an ion exchange member 42 having a filter pore diameter of 1 μm or less are arranged in the collection tube 23, and a membrane filter 41 and an ion exchange member having a filter pore diameter of 1 μm or less are arranged in the collection tube 24. An exchange member 43 is arranged.

  Note that the immersion exposure system according to the fourth embodiment is arranged in the Y direction with respect to the distal end portion 32A of the optical element 32 as in the immersion exposure system according to the third embodiment. The immersion nozzle is supplied and recovered using the discharge nozzles 27a, 28a and the inflow nozzles 29a, 29b, 30a, 30b. The immersion solution recovered from the inflow nozzles 29a, 29b, 30a, 30b is liquid. A membrane filter and an ion exchange member are disposed at a position immediately before being collected by the collection device 6.

  Accordingly, the particles and solids present in the immersion solution can be removed by the membrane filters 40 and 41 immediately before the immersion solution is recovered by the liquid recovery device 6. It is possible to prevent the optical element from being damaged. Moreover, since ions dissolved from the outside can be removed by the ion exchange members 42 and 43, the pH of the solution can be kept constant, and the optical element can be prevented from being eroded by the immersion solution. Thereby, the change of the optical performance of a projection optical system can be prevented, and desired optical performance can be maintained. Pure water can be easily obtained in large quantities at a semiconductor manufacturing factory or the like, and has the advantage that it does not adversely affect the photoresist, optical lenses, etc. on the wafer. In addition, pure water has no adverse effect on the environment, and since the impurity content is extremely low, it can be expected to clean the surface of the wafer.

  In the first and third embodiments described above, the immersion solution is a solution containing fluorine ions or fluoride ions, and a solution having a pH adjusted to 6 or less is used. Instead, a solution containing ammonium ions as the immersion solution and having a pH adjusted to 8 or more may be used.

  When the immersion solution is a solution containing ammonium ions, the optical element formed by fluorite does not erode, so that the optical performance of the projection optical system does not change and the desired optical performance is obtained. Can be maintained. Moreover, since the pH is adjusted to 8 or more, the alkalinity is high and weak alkaline contaminants do not dissolve. Therefore, since the optical element formed of fluorite is not eroded, the optical performance of the projection optical system is not changed, and the desired optical performance can be maintained.

  In the second and fourth embodiments described above, a membrane filter having a filter pore diameter of 1 μm or less is used as the filter. Among filter filters, activated carbon filters, hollow fiber filters, ultrafiltration filters, etc. One filter having a filter pore diameter of 1 μm or less may be used. Moreover, you may comprise a filter combining two or more in a membrane filter, a filter paper, an activated carbon filter, a hollow fiber filter, an ultrafiltration filter, etc.

  In the above-described embodiment, the space between the wafer surface and the optical element formed by the fluorite on the wafer side of the projection optical system is filled with the immersion solution. An immersion solution may be interposed between a portion of the optical element formed of fluorite on the wafer side.

  In the above-described embodiment, the membrane filter and the ion exchange member are disposed immediately before the immersion solution 7 is recovered by the liquid recovery device 6. However, the arrangement position is the immersion solution. As long as it is within the circulation system, it can be appropriately changed.

In the above-described embodiment, a dissolution preventing film may be formed on the surface of the optical element formed of fluorite on the wafer side of the projection optical system. In this case, when the immersion solution is a solution containing a high ammonium ion of the solution or alkalinity including high fluorine ions or fluoride ions acidity is magnesium fluoride (MgF _2), 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 ), thiolite (5NaF ・ 3AlF ₃ ), etc. It is preferable to do. Even when such a dissolution preventing film is formed, it is possible to prevent the dissolution preventing film from being dissolved by the immersion solution.

  In the above-described embodiment, an exposure apparatus that locally fills the space between the projection optical system PL and the wafer (substrate) W with a liquid is employed, but this 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 can also be applied to an immersion exposure apparatus that 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.

  A solution in which fluorine ions or fluoride ions were dissolved was circulated through the closed circulation system, and a lens without a coat or a lens with a thin film was constantly exposed to this aqueous solution for about 10 hours. Even after pulling up the sample after the experiment and drying it naturally, no water mark was observed on the sample. After the experiment, the surface of the lens was examined by step measurement and SEM, and no change such as dissolution was confirmed. The transmittance was measured, but no change was observed before and after the experiment. Further, the transmittance and reflectance of the sample coated with a thin film were measured, and no change was observed before and after the experiment.

  Table 1 shows the measurement results of the transmittance of lenses formed of uncoated fluorite and lenses formed of uncoated quartz before and after the experiment. Note that ArF excimer laser light (wavelength 193 nm) was used as measurement light.

また、以下に、実験前後における蛍石に薄膜として酸化アルミニウム(Al₂O₃)をコートしたレンズ、蛍石に薄膜としてフッ化ランタン(LaF₃)をコートしたレンズ、蛍石に薄膜としてフッ化マグネシウム(MgF₂)をコートしたレンズの透過率の測定結果を表２に示す。なお、測定光として、ＡｒＦエキシマレーザ光（波長１９３ｎｍ）を用いた。

In addition, the following is a lens coated with aluminum oxide (Al ₂ O ₃ ) as a thin film before and after the experiment, a lens coated with lanthanum fluoride (LaF ₃ ) as a thin film, and fluorite as a thin film. Table 2 shows the measurement results of the transmittance of the lens coated with magnesium (MgF ₂ ). Note that ArF excimer laser light (wavelength 193 nm) was used as measurement light.

  A solution in which ammonium ions were dissolved was circulated in a closed circulation system, and a lens without a coat and a lens with a thin film were constantly exposed to this aqueous solution for about 10 hours. Even after pulling up the sample after the experiment and drying it naturally, no water mark was observed on the sample. After the experiment, the surface of the lens was examined by step measurement and SEM, and no change such as dissolution was confirmed. The transmittance was measured, but no change was observed before and after the experiment. Further, the transmittance and reflectance of the sample coated with a thin film were measured, and no change was observed before and after the experiment.

  A buffer solution in which hydrofluoric acid and ammonium fluoride were mixed to adjust the pH to 7 or less was circulated in a closed circulation system, and uncoated lenses and thin film coated lenses were always exposed to this aqueous solution for about 10 hours. Even after pulling up the sample after the experiment and drying it naturally, no water mark was observed on the sample. After the experiment, the surface of the lens was examined by step measurement and SEM, and no change such as dissolution was confirmed. The transmittance was measured, but no change was observed before and after the experiment. Further, the transmittance and reflectance of the sample coated with a thin film were measured, and no change was observed before and after the experiment.

  A buffer solution adjusted to pH 7 to 9 by mixing borax and hydrochloric acid in a closed circulation system was circulated, and uncoated lenses and thin film coated lenses were always exposed to this aqueous solution for about 10 hours. Even after pulling up the sample after the experiment and drying it naturally, no water mark was observed on the sample. After the experiment, the surface of the lens was examined by step measurement and SEM, and no change such as dissolution was confirmed. The transmittance was measured, but no change was observed before and after the experiment. Further, the transmittance and reflectance of the sample coated with a thin film were measured, and no change was observed before and after the experiment.

  A buffer solution in which borax and sodium carbonate were mixed in the closed circulation system and the pH was adjusted to 9 to 11 was circulated, and uncoated lenses and thin film coated lenses were always exposed to this aqueous solution for about 10 hours. Even after pulling up the sample after the experiment and drying it naturally, no water mark was observed on the sample. After the experiment, the surface of the lens was examined by step measurement and SEM, and no change such as dissolution was confirmed. The transmittance was measured, but no change was observed before and after the experiment. Further, the transmittance and reflectance of the sample coated with a thin film were measured, and no change was observed before and after the experiment.

  A buffer solution in which PH is adjusted to 2 to 8 by mixing disodium hydrogen phosphate and citric acid in a closed circulation system is circulated, and an uncoated lens and a lens coated with a thin film are kept in this aqueous solution for about 10 hours. Exposed. Even after pulling up the sample after the experiment and drying it naturally, no water mark was observed on the sample. After the experiment, the surface of the lens was examined by step measurement and SEM, and no change such as dissolution was confirmed. The transmittance was measured, but no change was observed before and after the experiment. Further, the transmittance and reflectance of the sample coated with a thin film were measured, and no change was observed before and after the experiment.

  An ion exchange resin was installed in a part of the closed circulation system, and pure water was circulated for about 10 hours. When the solution was sampled several times during the experiment and the pH was measured, the pH was 6.9 to 7.2 and was kept constant. Further, when the sampled water was analyzed by ion chromatography, neither a cation nor an anion could be confirmed. Further, even when the sampled water was dropped on the silicon wafer and allowed to dry naturally, no water mark was observed on the silicon wafer.

  An ion exchange resin was installed in a part of the closed circulation system to circulate pure water, and the lens and the lens coated with the thin film were always exposed to this water for about 10 hours. Even after pulling up the sample after the experiment and drying it naturally, no water mark was observed on the sample. After the experiment, when the lens surface was examined by step measurement and SEM, no change such as dissolution was confirmed. Further, when the transmittance and reflectance of the sample coated with the thin film were measured, there was no change before and after the experiment.

  A membrane filter (pore diameter 0.45 μm) was attached to a part of the closed circulation system, and pure water was circulated for about 10 hours. After the experiment, when the particulate matter in the aqueous solution was measured with a particle size distribution meter, the presence of the particulate matter could not be confirmed. It was confirmed that the particulate matter was removed by the filter. Further, even when the sampled water was dropped on the silicon wafer and allowed to dry naturally, no water mark was observed on the silicon wafer.

It is a figure which shows schematic structure of the immersion exposure machine system containing the projection exposure apparatus concerning the 1st Embodiment of this invention. It is a figure which shows the positional relationship of the front-end | tip part of the optical element of the projection optical system of FIG. 1, 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 of the optical element of the projection optical system of FIG. 1, and the discharge nozzle and inflow nozzle which supply and collect | recover the liquid for immersion from a Y direction. FIG. 2 is an enlarged view of a main part showing a state of supply and recovery of an immersion solution between the optical element of FIG. 1 and a wafer. It is a figure for demonstrating the solution circulation system for immersion of the projection exposure apparatus contained in the immersion exposure machine system concerning the 2nd Embodiment of this invention. It is a figure for demonstrating the solution circulation system for immersion of the projection exposure apparatus contained in the immersion exposure machine system concerning the 2nd Embodiment of this invention. It is a front view which shows the lower end part of the projection optical system of the projection exposure apparatus used in the 3rd Embodiment of this invention, a liquid supply apparatus, a liquid collection | recovery apparatus, etc. FIG. It is a figure which shows the positional relationship of the front-end | tip part of the optical element of the projection optical system of FIG. 7, 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 of the optical element of the projection optical system of FIG. 7, and the discharge nozzle and inflow nozzle which supply and collect | recover the liquid for immersion from a Y direction. It is a figure for demonstrating the solution circulation system for immersion of the projection exposure apparatus contained in the immersion exposure machine system concerning the 4th Embodiment of this invention.

Explanation of symbols

R ... Reticle PL ... Projection optical system W ... Wafer 1 ... Illumination optical system 4, 32, 105 ... Optical element 5 ... Liquid supply device 6 ... Liquid recovery device 7 ... Solution for immersion 9 ... Z stage 10 ... XY stage 14 ... Main control systems 21, 22 ... supply pipes 21a to 21c, 22a to 22c ... discharge nozzles 23, 24 ... recovery pipes 23a, 23b, 24a, 24b ... inflow nozzles 40, 41, 44, 45 ... filters 42, 43, 46, 47 ... Ion exchange member

Claims (5)

It is formed by the surface of the substrate of an immersion type projection exposure apparatus that illuminates the mask with an exposure beam and transfers the pattern of the mask onto the substrate via a projection optical system and the fluorite on the substrate side of the projection optical system An immersion solution interposed between the optical elements,
The immersion solution contains a fluorine ion or a fluoride ion.   The immersion solution according to claim 1, wherein PH is 6 or less. It is formed by the surface of the substrate of an immersion type projection exposure apparatus that illuminates the mask with an exposure beam and transfers the pattern of the mask onto the substrate via a projection optical system and the fluorite on the substrate side of the projection optical system An immersion solution interposed between the optical elements,
The immersion solution contains ammonium ions.   4. The immersion solution according to claim 3, wherein PH is 8 or more. It is formed by the surface of the substrate of an immersion type projection exposure apparatus that illuminates the mask with an exposure beam and transfers the pattern of the mask onto the substrate via a projection optical system and the fluorite on the substrate side of the projection optical system An immersion solution interposed between the optical elements,
The immersion solution is constituted by a buffer solution.

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