JP2005085842A - Aligner and method for manufacturing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner which can prevent the deterioration of throughput and can reduce costs, and provide a method for manufacturing a device. <P>SOLUTION: In the aligner, the center of parallel plates used for seal glasses is displaced from the center of the other optical element i.e. the center of a lighting area, as a feature of the invention. A mechanism which rotates or slides or moves the seal glasses is arranged. As a result, a region on the seal glasses which is irradiated with laser light is changed, and a part in which glass material is not used can be restrained to a minimum. Further, time duration which stops job of the aligner can be reduced remarkably by automating slide and rotation movements of the seal glasses. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure apparatus and a device manufacturing method.

  2. Description of the Related Art Conventionally, a reduction projection exposure apparatus has been used in a manufacturing process of a semiconductor element formed from a very fine pattern such as LSI or VLSI. As the mounting density of semiconductor elements has increased, further miniaturization of patterns has been required, and at the same time as the development of resist processes, the miniaturization of exposure apparatuses has been addressed.

  As means for improving the resolution of the exposure apparatus, there are a method of changing the exposure wavelength to a shorter wavelength and a method of increasing the numerical aperture (NA) of the projection optical system. In general, it is known that the resolution is proportional to the exposure wavelength and inversely proportional to the NA. In addition, efforts have been made to ensure the depth of focus of the projection optical system while improving the resolution.

  In general, since the depth of focus is proportional to the exposure wavelength and inversely proportional to the square of NA, the improvement in resolution and the securing of the depth of focus are contradictory issues. As a method for solving such a problem, a phase shift reticle method, a FLEX (Focus Latitude enhancement Exposure) method, and the like have been proposed.

With regard to the exposure wavelength, KrF excimer lasers having an oscillation wavelength of about 248 nm from i-line of 365 nm have recently become mainstream, and further, ArF excimer lasers and F ₂ lasers having an oscillation wavelength of about 193 nm as next-generation exposure light sources. (157m) is being developed.

  Further, from the viewpoint of manufacturing cost of semiconductor elements, further improvement in throughput in the exposure apparatus has been attempted. For example, there are a method of shortening the exposure time per shot by increasing the output of the exposure light source, or a method of increasing the number of elements per shot by expanding the exposure area.

  Furthermore, in recent years, in order to cope with an increase in the chip size of a semiconductor element, scanning exposure is performed while synchronizing a mask and a wafer from a so-called stepper of a step-and-repeat method that sequentially prints and moves a mask pattern. A step-and-scan type exposure apparatus that sequentially moves shots is being transferred. This step-and-scan type exposure apparatus has a feature that the exposure area can be expanded without increasing the size of the projection optical system because the exposure field is slit-shaped.

As described above, when ultraviolet rays are used as an exposure light source, ammonium sulfate (NH ₄ ) ₂ SO ₄ or silicon dioxide SiO ₂ adheres to the surface of the optical element disposed in the optical path as a result of using the apparatus for a long time. A phenomenon occurs in which the optical characteristics are significantly deteriorated. This is generated by causing a chemical reaction when ammonia NH ₃ , sulfurous acid SO ₂ , Si compound and the like contained in the surrounding environment are irradiated with ultraviolet rays. Conventionally, in order to prevent such deterioration of the optical element, the entire optical path is purged with an inert gas such as clean dry air or nitrogen.

Furthermore, it is known that in an ArF excimer laser having far ultraviolet light, particularly a wavelength near 193 nm, there are a plurality of oxygen (O ₂ ) absorption bands in the band near the wavelength. In addition, oxygen absorbs the light to generate ozone (O ₃ ). This ozone further increases the absorption of light and significantly reduces the transmittance. The product adheres to the surface of the optical element, reducing the efficiency of the optical system.

Therefore, in the optical path of the exposure optical system of a projection exposure apparatus that uses far ultraviolet rays as a light source such as an ArF excimer laser, there is a method of suppressing the oxygen concentration present in the optical path to a low level by purging with an inert gas such as nitrogen. It is taken. Furthermore, when an F ₂ laser having a shorter wavelength than ArF is used, the absorption coefficient of oxygen is very large, so that exposure light is absorbed when oxygen is contained in the air, and is used as an exposure light source. Can not do it. For this reason, a technique is used in which exposure of exposure light is prevented by eliminating air in the exposure apparatus, filling with an atmospheric gas such as helium or nitrogen, and keeping the oxygen concentration low.

  However, replacing the atmospheric gas in the exposure apparatus as described above with helium or nitrogen gas causes a reduction in throughput due to the time required for the atmospheric gas replacement. In addition, since a large amount of replacement gas is required and the structure of the exposure apparatus chamber is complicated, there are significant problems in terms of cost. Therefore, it is preferable to replace the minimum range on the optical path of the laser beam with an inert gas such as nitrogen gas or helium gas.

  In order to minimize the gas replacement area, Patent Document 1 proposes a method in which an illumination optical system and a projection optical system on the optical path are housed in a plurality of casings, and the interior is replaced with gas. It is possible to replace all the optical paths from the light source to the wafer by providing a housing for coupling between the housings and providing a path for supplying a replacement gas therein.

Japanese Patent Laid-Open No. 06-21600

  When the optical element on the optical path from the laser beam exit to the wafer surface is housed in the housing, seal glass (parallel plate) that transmits the laser light is used for the laser beam entrance and exit of the housing. And often sealed.

  However, as the wavelength of laser light has been shortened and the output has been increased, the deterioration of these sealing glasses has become a problem. In this case, the deterioration of the seal glass means a change in refractive index or a deterioration of the coating. In particular, the seal glass used at the exit of the laser body used as the light source device is significantly deteriorated, and is always a place requiring maintenance. In addition, there are not a few seal glasses used at positions where the energy density of the laser is high, and there are similar problems. The occurrence of the replacement work of these seal glasses is a factor that significantly reduces the throughput of the apparatus because it is necessary to temporarily stop the job of the exposure apparatus.

  In addition, since the step-and-scan exposure apparatus has a rectangular illumination range, there is a disadvantage in that a large area that is not used in a circular seal glass that is normally used is large and cost considerations are taken into consideration. .

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an exposure apparatus and a device manufacturing method capable of preventing throughput deterioration and reducing costs.

  In order to achieve the above object, the exposure apparatus according to the present invention is characterized in that the center of the parallel plate used for the seal glass is decentered from the center of another optical element, that is, the center of the illumination range. Then, a mechanism for rotating or sliding the seal glass is provided. Thereby, it is possible to change the range irradiated with the laser beam on the seal glass and minimize the unused portion of the glass material. Also, by automating the slide and rotation of the seal glass, the time for stopping the job of the exposure apparatus can be greatly reduced.

  According to the present invention, it is possible to prevent the deterioration of the throughput by reducing the replacement work of the seal glass. Further, since it is possible to reduce the unused range of the glass material, it is advantageous in terms of cost.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a diagram schematically showing a step-and-scan type exposure apparatus according to an embodiment of the present invention as seen from the side.

In FIG. 1, reference numeral 1 denotes a light source which emits pulses with a KrF excimer laser having an oscillation wavelength near 248 nm, an ArF excimer laser having an oscillation wavelength near 193 nm, or an F ₂ laser having an oscillation wavelength near 157 nm. is there.

  The laser beam from the light source 1 is guided to the first illumination optical system housed in the casing 3 placed on the gantry 2b via the laser beam routing unit 2a, reflected by the internal mirror 3a, and a predetermined beam. The light is incident on the optical integrator 3d from the molding optical system 3b and the mirror 3c for molding into a shape. In the vicinity of the exit surface of the optical integrator 3d, a switching unit 4a for a secondary light source housed in the housing 4 is disposed.

  The light from the secondary light source is collected by the condenser lens 5 a housed in the housing 5 and enters the variable blind 6 a housed in the housing 6. In the variable blind 6a, a light shielding plate is disposed in the vicinity of a surface orthogonal to the optical axis including the condensing point formed by the condensing lens 5a so that the illumination area of the pattern surface of the mask 8 can be arbitrarily set. Yes.

  FIG. 2 shows a state where the mask 8 is illuminated. Light from the variable blind 6 a enters the second illumination optical system housed in the housing 7. The second illumination optical system includes condenser lenses 7a and 7c and a mirror 7b.

  The light from the second illumination optical system illuminates a part of the pattern 8a formed on the mask 8 with a slit light beam 8b, and the projection optical system 11 shown in FIG. Reduce the projection of the part. At this time, as shown by the arrows shown in FIG. 1, the mask 8 and the wafer 12 are scanned in opposite directions with respect to the projection optical system 11 and the slit-shaped light beam 8b at the same speed ratio as the reduction ratio of the projection optical system 11. The pattern 8a on the entire surface of the mask 8 is transferred to one chip area or a plurality of chip areas on the wafer 12 by repeating multi-pulse exposure by pulse emission from the light source 1. A half mirror 32 is arranged in the optical path of the second illumination optical system. The half mirror 32 guides a part of the illumination light to the photoelectric sensor 33 that detects the amount of light, and the output of the light source 1 is adjusted so that the exposure amount per shot becomes a desired value based on the detection result of the photoelectric sensor 33. The

  Reference numeral 10 denotes a mask stage, which scans in the direction of the arrow by a drive system (not shown) while holding the mask and the mask chuck 9 holding the mask. A bar mirror 15 is fixed to the mask stage 10, and a laser interferometer 16 detects the speed of the mask stage 10. The mask stage 10 and the laser interferometer 16 are both mounted on a support surface plate 17. Note that the support surface plate 17 is fixed on a lens barrel surface plate 20 that holds the projection optical system 11 from the floor via a support column 18 and a damper 19.

  A wafer stage 14 scans in the direction of the arrow by a drive system (not shown) while holding the wafer 12 and the wafer chuck 13 holding the wafer 12. Reference numeral 21 denotes a bar mirror fixed to the wafer stage 14, and reference numeral 22 denotes a laser interferometer for detecting the speed of the wafer stage 14, which is fixed to the lens barrel surface plate 20. The wafer stage 14 is placed on a stage surface plate 24 via a damper 23 from the floor.

  Further, the relative distance in the vertical direction in the drawing between the lens barrel surface plate 20 and the stage surface plate 24 is measured by a laser interferometer 25 fixed to the lens barrel surface plate 20. As described above, the laser interferometers 22 and 25 guarantee the positional relationship between the lens barrel surface plate 20 and the wafer stage 24, that is, the predetermined relative positional relationship between the mask 8 and the wafer 12.

  The casings 2a, 3, 4, 5, 6, and 7, which are each block of the illumination system, have a sealed structure and are supported by a gantry (not shown). The housings and the mask stage cover 31 are connected by sealing members 26, 27, 28, 29, and 30 made of fluororubber. Each casing is provided with a path through which gas passes, and has a so-called serial purge structure, and is purged with nitrogen. The purge gas may be helium. When a KrF excimer laser is used as the light source, clean dry air may be used.

  FIG. 3 is a detailed view when the present invention is used in the laser beam routing section 2a.

  In FIG. 3, reference numeral 41 denotes a seal glass portion that holds a seal glass 41a and has a mechanism that can rotate around an axis parallel to the optical axis. The inside of the light source 1 and the purge space of the laser beam routing part 2a are divided by the seal glass 41a as a boundary. Reference numeral 43 denotes a cylindrical lens unit for converting the laser light emitted from the light source into an actual exposure shape. Reference numerals 42 a and 43 a represent the shapes of the laser beams when passing through the seal glass portion 42 and the cylindrical lens portion 43.

  Since the energy density of 42a is higher than that of 43a, the sealing glass 42 is irradiated with excessive energy and deteriorates in a short period (several weeks to several months), which causes a decrease in illuminance and deterioration in image performance. Become. Reference numeral 44 denotes a phase adjusting plate for reducing the generation of interference fringes by randomizing the phase of parallel and coherent laser light from the light source. The phase difference adjusting plate is preferably arranged behind the cylindrical lens portion in order to prevent deterioration.

  FIG. 4 shows a range through which the laser light of the seal glass passes.

  By not matching the center of the seal glass with the center of the laser light, the seal glass can be rotated and moved to an area where the laser light passes through an unused area of the seal glass. This rotating mechanism (not shown) is provided with a positioning mechanism at the time of rotation, and it is possible to accurately move an unused place of the seal glass to a laser beam passage portion. Thereby, when deterioration of the seal glass occurs, it is possible to return the apparatus to a usable state in a minimum time. Further, since the unused range of the seal glass can be reduced, it is advantageous in terms of cost.

  A mechanism for driving the rotating mechanism may be provided and automatically driven. The switching timing in this case is most easily set based on the usage time of the apparatus. An upper limit value of the device usage time is set in advance in the main control system, and the seal glass portion is set to be automatically driven when the usage time of the device reaches the upper limit value.

  As shown in FIG. 5, the use time of the apparatus is the time when the light source actually oscillates the laser in this case. Data of the time when the laser was oscillating is sent from the light source to the main control system of the scanner, and when the preset time is reached here, a signal is sent from the main control system to the seal glass drive control system, The seal glass driving unit is driven.

  Further, the switching timing may be determined based on the total exposure amount as shown in FIG. A half mirror is installed inside the illumination system, and the laser beam taken out by the half mirror is monitored by a photoelectric sensor. The monitored exposure amount data is sent to the main control system. When the total amount of the exposure amount reaches a preset upper limit value, a signal is output from the main control system to the seal glass drive control unit so that the seal glass drive unit is driven. The photoelectric sensor in this case may use the photoelectric sensor 33 shown in FIG. For further simplicity, the illuminance of the laser beam obtained by the photoelectric sensor at the time of starting the apparatus is recorded, and switching is performed when a preset lower limit value or reduction rate of the illuminance is reached.

  In order to omit the means for determining the switching timing, the seal glass may always be rotated when the apparatus is used.

  As a method of arranging the sealing glass of the rotating mechanism, a slide plate 51 as shown in FIG. 7 or a turret 52 as shown in FIG. 8 in which a plurality of sealing glasses 53 having a shape larger than the laser beam are arranged is used. May be. The shape of the seal glass takes the positioning error into consideration, and it is possible to minimize the cost of the glass material by using a minimum size.

  In the above embodiment, the sealing glass for the laser beam exit port has been described. However, the sealing glass is suitable for all sealing glass provided in a place with a high energy density.

  The present invention is not limited to the exposure apparatus, and can be applied to a device manufacturing method. For example, a step of applying a resist to an object to be exposed such as a wafer, a step of exposing an object to be exposed such as a wafer using the exposure apparatus as described above, a step of developing the exposed object to be exposed, etc. The device manufacturing method is within the applicable range of the present invention.

It is a figure explaining the structure of the projection exposure apparatus which concerns on this invention. It is a figure explaining that the illumination area | region on the mask of the exposure apparatus which concerns on this invention is set with a variable blind. It is a figure explaining the structure of the laser beam routing part which concerns on embodiment of this invention. It is a figure explaining the area | region through which the laser beam of seal glass passes. It is a figure explaining the control method in the case of performing the drive timing of a seal glass drive part based on the usage time of an apparatus. It is a figure explaining the control method in the case of performing the drive timing of a seal glass drive part based on an integrated exposure amount. It is a figure explaining the structure at the time of arrange | positioning sealing glass on a slide plate. It is a figure explaining the structure at the time of arrange | positioning seal glass on a turret.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Base 3 Case 3a Mirror 3b Molding optical system 3c Mirror 3d Optical integrator 4 Case 4a Secondary light source switching part 5 Case 5a Condensing lens 6 Case 6a Variable blind 7 Case 7a Condensing lens 7b Mirror 7c Condensing lens 8 Mask 8a Mask pattern 8b Slit-shaped light beam 9 Mask chuck 10 Mask stage 11 Projection lens 12 Wafer 13 Wafer chuck 14 Wafer stage 15 Bar mirror 16 Laser interferometer 17 Pointing platen 18 Post 19 Damper 20 Lens barrel platen 21 Bar mirror DESCRIPTION OF SYMBOLS 22 Laser interferometer 23 Damper 24 Stage surface plate 25 Laser interferometer 26-30 Sealing member 31 Mask stage cover part 32 Half mirror 33 Photoelectric sensor 41 Seal glass part 42 Seal glass 42a Seal glass part Center 42c laser light having a center 43 the cylindrical lens portion 43a the cylindrical lens portion of the laser beam during the passage shape 44 phase adjusting plate 51 slide plate 52 turret plate 53 seal glass shape 42b seal glass over-time of the laser beam

Claims (10)

An exposure apparatus that illuminates a mask with an exposure light from an exposure light source via an illumination optical system, and projects and exposes a pattern formed on the mask onto a photosensitive substrate via a projection optical system,
An optical element disposed on an optical path of exposure light from the exposure light source to the projection optical system is disposed in a plurality of cases, and the inside can be replaced with an inert gas or clean dry air. An exposure apparatus characterized in that an optical element disposed at a laser beam incident port or a laser beam emitting part port of the previous casing is decentered from the center of another optical element.   The exposure apparatus according to claim 1, wherein the optical element is capable of changing a range in which illumination light on the optical element passes by rotating or translating.   The exposure apparatus according to claim 2, wherein the optical element includes a mechanism for determining a position when the optical element rotates or translates.   3. The exposure apparatus according to claim 2, wherein the optical element is disposed only in a range through which illumination light passes when rotated or translated.   3. An exposure apparatus according to claim 2, further comprising a mechanism for automatically driving rotation or parallel movement of the optical element.   6. The exposure apparatus according to claim 5, further comprising means for measuring the illuminance of the illumination light, wherein the optical element is automatically driven based on a measurement result of the illuminance of the illumination light.   6. The exposure apparatus according to claim 5, wherein the automatic driving of the optical element is always performed when the apparatus is used.   6. The exposure apparatus according to claim 5, wherein the optical element is automatically driven based on a preset parameter.   9. The exposure apparatus according to claim 8, wherein the parameter is any one of a use time of the exposure apparatus, an integrated exposure amount, an oscillation pulse number, or a combination thereof.   10. A device manufacturing method comprising: exposing an object to be exposed using the exposure apparatus according to claim 9; and developing the exposed object to be exposed.

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