WO2000068980A1 - Method and apparatus for exposure - Google Patents

Abstract

A projection optic system (PL) is heated by the irradiation with exposure light (L) from a lighting system (2) before a reticle (R) is set up on a reticle stage (14). The reticle is then placed on the reticle stage and irradiated. As a result, before a projection of the reticle pattern onto a wafer, the projection optic system is preheated to a saturation point at which the reticle pattern is actually exposed, so that the temperature change of the optic system is reduced during the actual exposure. Further, the preheating in the absence of the reticle reduces the storage of light energy in the reticle, thus reducing the thermal expansion of the reticle, the variation of such expansion and the distortion of the projected image.

Description

 Description Exposure method and exposure apparatus Background art

 1. Technical Field of the Invention

 The present invention relates to an exposure method and an exposure apparatus for manufacturing fine circuit patterns such as “semiconductor integrated circuits and liquid crystals”.

 2. Conventional technology

 A microfabricated element represented by a semiconductor element or a liquid crystal display element is usually manufactured by using a photolithographic process. In this process, a pattern image of a mask (including a reticle, hereinafter referred to as a reticle) is transferred onto a substrate (wafer, glass plate, etc.) coated with a photosensitive material (resist) via a projection optical system. A projection exposure apparatus that transfers the image to a projection (shot) area is used.

In recent years, as a projection exposure apparatus of this type, a wafer is placed on a two-dimensionally movable stage, and the wafer is stepped (stepped) by this stage. A so-called step-and-repeat or step-and-scan exposure apparatus, which repeats an operation of sequentially exposing regions, particularly a reduction projection type exposure apparatus (stepper or scan-ninda stepper) is frequently used. In such an apparatus, for example, a semiconductor element has a circuit pattern transferred onto a wafer, and is formed as a circuit by post-processing. Recently, high-density integration of integrated circuits (miniaturization of circuit patterns) is required. Accordingly, in order to obtain higher resolution, laser light in the ultraviolet region has been increasingly used as exposure light. Depending on the wavelength, such ultraviolet light may be absorbed by a glass material used in an optical system or a gas present in an optical path. Therefore, when performing projection exposure, a suitable transmittance having a high transmittance to the exposure light is appropriate. It is necessary to use a glass material and purge (closely fill) the optical path with an appropriate gas that does not absorb the exposure light. In the former, mainly calcium fluoride (fluorite: C a F _2), magnesium fluoride (M g F _2), etc., in the latter helium (H e), nitrogen (N ₂₎ or the like is used. On the other hand, in the exposure apparatus, a part of the exposure light transmitted through the projection optical system is absorbed by an optical element such as a lens. The optical element generates heat by absorbing the exposure light, and the heat generation causes thermal expansion. In particular, in an optical system using a short wavelength laser such as an excimer laser, the power of incident light is large and the amount of light absorbed by the optical element is large. Moreover, optical glass materials that transmit short-wavelength light (eg, fluorite) generally have a large coefficient of thermal expansion. Therefore, when a short wavelength laser is used as the exposure light, the thermal expansion becomes larger as compared with the case of lithography in a longer wavelength region. The thermal expansion of the optical element due to this exposure changes the imaging characteristics of the projection optical system when finally printing a circuit pattern on the wafer. For example, it causes a phenomenon that the sharpness of the projected image is degraded or the projection magnification fluctuates. In addition, the phenomenon that the projected image is distorted (distortion) due to uneven thermal expansion also occurs.

 The present invention has been made in view of the above problems, and has as its object to provide an exposure method and an exposure apparatus that can eliminate fluctuations in irradiation of a projection optical system during exposure due to absorption of exposure light. Disclosure of the invention

 In the present invention, the following configuration is adopted to solve the above-mentioned problems. In the following, referring to FIG. 1, according to the exposure method of the present invention, an illumination optical system (2) is used to irradiate exposure light (L) onto a mask (R) installed on a mask stage (10). In an exposure method in which the pattern on the mask is projected onto the surface of the substrate (W) via the projection optical system (PL) and exposed, the exposure light is used by the illumination optical system before the mask is set on the mask stage. A technology is employed that includes a preheating step of irradiating the projection optical system to heat the projection optical system, and an exposure step of exposing the mask by placing the mask on a mask stage immediately after the preheating step.

In the exposure apparatus of the present invention, the illumination optical system (2) irradiates the exposure light (L) onto the mask (R) provided on the mask stage (10), and the pattern on the mask is In an exposure apparatus that projects and exposes the surface of a substrate (W) via a projection optical system (PL), a mask transport system (20A, 20B) for transporting a mask to a mask stage, a mask transport system and A control system (16) for controlling the illumination optical system, wherein the control system comprises: Before the mask is set on the mask stage, the projection optical system is irradiated with exposure light by an illumination optical system and heated, and immediately after this, the mask is set on the mask stage by a mask transport system and the illumination optical system is set. The technique of performing exposure by means of is adopted. In these exposure methods and exposure apparatuses, before the mask (R) is set on the mask stage (10), the projection optical system (PL) is irradiated with the exposure light (L) by the illumination optical system (2). (Hereinafter referred to as preheating), and immediately after that, the mask is set on the mask stage for exposure, so that the mask pattern is not projected onto the wafer (the mask is not projected on the projection optical path). (Existing state), the projection optical system can be heated to the saturation point reached when the mask pattern is actually exposed, and the thermal fluctuation of the optical system during the actual exposure can be suppressed. In addition, since preheating is performed when the mask is not loaded, the energy of the illuminating light beam does not need to be stored in the mask, and thermal expansion of the mask and its fluctuation and distortion of the projected image can be reduced.

 Further, in the exposure method of the present invention, a mask (R) is arranged in the first chamber (RC) having a small amount of impurities that attenuate the exposure light (L), and the mask is irradiated with the exposure light, and the projection optical system ( In the exposure method for exposing a substrate (W) with exposure light via the PL), a mask is carried into the second chamber (19) connected to the first chamber, and the concentration of impurities in the second chamber is determined. And a step of moving the mask in the second chamber into the first chamber after the preheating step. I have.

 Further, in the exposure apparatus of the present invention, an illumination optical system (2) for irradiating the mask (R) disposed in the first chamber (RC) with a small amount of impurities for attenuating the exposure light (L) with the exposure light; A projection optical system (PL) for irradiating exposure light onto a substrate (W) to which the pattern is to be transferred, a second chamber connected to the first chamber and into which a mask is loaded prior to the first chamber (19) controlling the removal device and the heating device that heats the projection optical system so that the concentration of impurities in the second chamber is equal to or less than a predetermined allowable value; And a control system (16) that performs heating in almost parallel.

In these exposure methods and exposure apparatuses, the projection optical system (PL) is preheated almost in parallel with the control of the impurity concentration in the second chamber (19) to a predetermined allowable value or less. As a result, a reduction in processing capacity due to removal of impurities and execution of preheating can be reduced. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is an overall configuration diagram showing an embodiment of an exposure apparatus according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, an embodiment of an exposure method and an exposure apparatus according to the present invention will be described with reference to FIG.

FIG. 1 shows a step-and-scan projection exposure apparatus according to the present embodiment. The projection exposure apparatus irradiates the pattern formed on the reticle R with the exposure light L in the ultraviolet wavelength region emitted from the exposure light source 1 via the illumination optical system 2, and forms a projection optical system including a plurality of optical elements. Projection exposure is performed on the surface of the wafer (substrate) W, which is the substrate to be exposed, via the system PL. In the present embodiment, those in the exposure light source 1 generates an exposure light L wavelength range shorter than the wavelength of A r F excimer laser (1 2 0~ 1 9 0 nm ), for example, F ₂ laser (Wavelength: 157 nm) A light source is used.

The illumination optical system 2 uses the exposure light L from the exposure light source 1 to oscillate the mirror 3, the half mirror HM, the fly lens as an optical integrator (homogenizer) or the rod 'Integrator FI, the reflective mirror 5A, and the half mirror. It irradiates the reticle R via a transmission mirror or beam splitter 4, relay lenses 6A and 6B, field stop 7, reflection mirror 5B, condenser lens 8, and the like. The irradiation area of the exposure light L on the reticle R is defined by the field stop 7 into, for example, a rectangular shape extending in a direction perpendicular to the moving direction of the reticle R during scanning exposure. The exposure light L transmitted through the reticle R enters, for example, a projection optical system PL that is telecentric on both sides, and the projection optical system PL converts a part of the pattern of the reticle R, that is, a pattern in a rectangular irradiation area, into a projection magnification. The projection is reduced onto the wafer W at / 3 (for example, / 3 = 1 Z4 or 1 Z5). The projection optical system PL may be any one of a dioptric optical system, a catoptric optical system, and a catoptric optical system, but in the present embodiment, the first optical A primary image (width image) of the reticle pattern is formed by the system, and a plurality of reflective elements (primary mirror) are arranged on the optical axis on which the plurality of refractive elements are arranged, each having an opening through which exposure light L passes. A catadioptric optical system that re-images the intermediate image using a second optical system including In addition, a part of the exposure light L emitted from the optical integrator FI is reflected by the semi-transmissive mirror 4 and detected by the integral overnight sensor 15A including a photoelectric detector or the like.

 The reticle R is placed on the reticle stage 10 at the time of exposure, for example, by vacuum suction or the like. The wafer W is also set on the wafer holder 13 by vacuum suction or the like.

 The wafer W and the wafer holder 13 can be moved by a wafer stage 14, and the wafer stage 14 sequentially moves each shot area (for example, the area of an LSI chip) on the wafer W directly below the projection optical system PL. Is controlled by the exposure controller 17 and the control system 16 so that the pattern image of the reticle R is transferred onto the wafer W.

 The exposure light L reflected on the wafer W passes through the projection optical system P L ゃ reticle R and the like, is reflected by the semi-transparent mirror 14, and is detected by the reflected light monitor 15B.

Reticle stage 10 and wafer stage 14 are housed in reticle-side chamber (casing, first chamber) RC and wafer-side chamber WC, respectively. Further, the insides of these chambers RC and WC are filled with a gas (a specific atmosphere) having a high transmittance to the exposure light L or in a vacuum state. In this embodiment, the chambers RC and WC are each filled with helium. Further, the illumination optical system 2 has all the optical elements housed in a sub-chamber (or lens barrel) IU, and the light source 1, the illumination optical system 2 (sub-chamber IU), and the projection optical system PL Each gas is replaced (purged) with a gas having a high transmittance to the exposure light L, for example, helium. One end of the illumination optical system 2 (sub-chamber IU) is connected to the light source 1, the other end is connected to the reticle-side chamber RC, and the projection optical system PL has one end connected to the reticle-side chamber RC. The end is connected to the wafer-side chamber WC. Thus, the exposure light L generated from the light source 1 passes through only the helium-substituted optical path without being exposed to air (particularly oxygen). Reach C W.

 To avoid absorption and attenuation of the exposure light L on the optical path, the part connecting the projection optical system PL and the illumination optical system 2 is replaced (purged) with a gas or vacuum having a high transmittance for the exposure light L, It is necessary to prevent the power of the exposure light L from being lost. Therefore, in order to carry in and out the reticle R, a spare room (second room) 19 for the above-mentioned replacement is provided on a path for carrying in and out the reticle R from outside the purge area to the inside of the purge area. In this embodiment, helium is used as the gas.

 The preliminary chamber 19 is provided between the reticle-side chamber RC and the outside (such as a reticle library), and is connected to the reticle-side chamber RC via a shutter 22a. The space 22 inside the reticle-side chamber RC adjacent to the spare room 19 and the space 18 outside the reticle chamber are inside and outside the purged area, respectively. It is isolated from the spare room 19 by 1 22a. The space 18 and the space 22 are both sealed so that gas does not enter and exit, but the spare room 19 has an air supply port 21a and an exhaust port 21b connected to it. The gas in the spare room 19 can be replaced. In other words, the air supply port 21a, the exhaust port 21b, and the shirts 18a, 22a are used as replacement devices for replacing the atmosphere in the preparatory chamber 19 with the atmosphere in the reticle-side chamber RC. Function. Although not shown, a sensor for detecting the concentration of impurities (oxygen, water vapor, organic matter, and the like) is provided in the preliminary chamber 19, and in this embodiment, the impurity concentration in the preliminary chamber 19 is set to a predetermined value. Reticle side chamber RC, or the same as reticle side chamber RC, or even if shutter 22a is opened, the impurity concentration in reticle side chamber RC increases until it does not increase. Shall not be opened. Further, in this embodiment, one end of the spare room 19 is connected to the external space 18, but may be connected to another spare room. Further, the transfer path between the reticle cassette or reticle library and the reticle-side chamber RC may be substantially entirely replaced with helium or the like. In this case, the light irradiating section 23 used for optical cleaning of the reticle is placed in a purge area separate from the preparatory chamber 19

(Housing or spare room).

In addition, the first reticle loader (reticle transfer system, first transfer system) 2 OA and the second reticle loader (reticle transfer system, second transfer system) 20 B are the space 18 and They are installed in series so as to penetrate the space 22. The first reticle loader 2 OA carries the reticle R between the space 18 and the space 19 and the second reticle loader 20 B carries the reticle R between the space 19 and the space 22. . That is, the first reticle port 2OA and the second reticle loader 20B carry in and out the reticle R between the space 18 outside the purge area and the space 22 inside the purge area, and the reticle. Functions as a reticle transport system that leads to stage 10.

 The first reticle loader 20A, the second reticle loader 20B, and the shutters -18a and 22a are all controlled by the control system 16. Similarly, a suction system (not shown) such as a vacuum pump connected to the exhaust port 21 b and a supply source of a purge gas (not shown) connected to the air supply port 21 a are also controlled by the control system 16. Is done. In addition, in order to supply helium into the spare chamber 19 and reduce the impurity concentration below the allowable value, both the air supply port 21a and the exhaust port 21b are opened to supply and exhaust helium. It may be performed in parallel. Alternatively, the inside of the preliminary chamber 19 may be evacuated through the exhaust port 21b with the air supply port 21a closed, and then helium may be supplied from the air supply port 21a.

 The preliminary chamber 19 is provided with a light irradiator (light washing device) 23 that irradiates a part of the exposure light L to the loaded reticle R and removes impurities adhering to the surface of the reticle R. . The light irradiating section 23 is composed of a window or optical member made of a glass material transparent to the exposure light L, and a part of the exposure light L branched by the half mirror HM is transmitted through a reflection mirror M or the like. be introduced. The light irradiating section 23 is positioned above the preliminary chamber 19 so that the entire surface of the reticle R in the preliminary chamber 19 is irradiated with the exposure light L. Although not shown in FIG. 1, the optical path between the half mirror (beam splitter) HM and the light irradiating section 23 that branches a part of the exposure light L is also replaced (purged) with helium. Is reduced.

In the present embodiment, the entire surface of the reticle R is irradiated with the exposure light L by the light irradiation unit 23, but at least one of the first and second reticle loaders 20A and 20B is used. The reticle R may be irradiated with the exposure light L over the entire surface of the reticle R by relatively moving the reticle R with respect to the irradiation area of the exposure light L by using. In addition, it is not necessary to always arrange the half mirror HM in the optical path of the illumination optical system 2; — The HM may be inserted into and removed from the illumination optical path so that it is only placed in the optical path when the projection optical system PL is preheated (and the reticle is washed with light). Further, a light source for light cleaning (for example, an ultraviolet lamp, etc.) is prepared separately from the power supply 1 for exposure, and the reticle R is irradiated with illumination light having a wavelength of, for example, about 140 to 250 nm. Light may be washed. In this case, a light source for light cleaning may be prepared in the spare room 19, or may be arranged outside the spare room 19, and the illumination light may be guided into the spare room 19 using, for example, an optical fiber. Is also good.

 Next, an exposure method in the projection exposure apparatus of the present embodiment will be described in the order of steps.

 [Transport to the spare room]

 First, the first reticle loader 20 A is controlled by the control system 16, the reticle R is loaded to the space 18 outside the page area, and the shirt 18 a in the spare room 19 is opened. Then, carry it into the spare room 19. At this time, the shirt 22a is closed, and the space between the preparatory room 19 and the space 22 of the reticle side chamber RC is shut off.

[Light cleaning of reticle]

 After the reticle R is loaded into the spare room 19, the shutter 18a is closed, and the inside of the spare room 19 is replaced (purged) with helium to make it a sealed state. After that, while exposing the exposure light L from the exposure light source 1, a part of the branched exposure light L is irradiated from the light irradiation part 23 to the reticle R in the spare room 19, and adheres to the surface of the reticle R. The impurities are removed by the exposure light L.

 In this case, taking into account the deterioration of the reticle R due to the exposure light L, the exposure light L irradiated for light cleaning is set to a light amount and irradiation time that are sufficiently effective to remove impurities and as small as possible. You. This step (optical cleaning of the reticle) is a step for enabling more accurate transfer of the reticle pattern, but is not necessarily performed, and may be appropriately performed as necessary.

 [Replacement of gas]

After the completion of the light cleaning, the gas currently filled in the preparatory chamber 19 is sucked and discharged from the exhaust port 21b, and the helium gas filled in the purge area (the reticle chamber RC) is discharged. Fill in the spare room 19 from the air supply port 21a. At this time, impurities blown out of the reticle R by the light cleaning are simultaneously discharged from the exhaust port 2 lb.

The gas is replaced (or evacuated) until the gas composition (or degree of vacuum) in the preliminary chamber 19 reaches the same level as in the purge area (for example, the reticle-side chamber RC). In this embodiment, the use of the F ₂ laser beam as the exposure light L, and substitution level of the preliminary chamber 1 9, acid by 〇 ₂ concentration meter provided in the preparatory chamber 1 9 (not shown) Judgment is made from the elemental density state. On the other hand, when evacuation is performed, the air supply port 21a is closed, and the gas in the spare chamber 19 is sucked from the exhaust port 21b to perform evacuation.

 In this embodiment, in order to perform the light cleaning of the reticle R using the exposure light L, the inside of the preliminary chamber 19 is replaced with helium prior to the light cleaning of the reticle R. At this time, in order to minimize the attenuation of the exposure light L, it is desirable that the impurity concentration in the preliminary chamber 19 be equal to or less than the allowable value described above. However, this method requires a short light cleaning time. It takes time to replace the surface. Conversely, when the impurity concentration exceeds the allowable value, the time required for optical cleaning is prolonged, but the time required for replacement work is reduced. Therefore, in this embodiment, it is desirable to determine the impurity concentration in the preliminary chamber 19 so that the time required for the replacement and the light cleaning is minimized. Further, in the present embodiment, the inside of the preliminary chamber 19 is sealed to perform optical cleaning. However, the optical cleaning is performed while circulating helium by opening both the air supply port 21a and the exhaust port 21b. May go.

Further, in this embodiment, the light cleaning is performed after replacing the inside of the preliminary chamber 19 with helium. However, during this replacement work, the light cleaning is started, the light cleaning is completed, and the light in the preliminary chamber 19 is removed. The replacement operation may be completed when the impurity concentration becomes equal to or less than the above-described allowable value. In this case, the replacement work and the light cleaning can be performed in parallel, and there is no need to perform the replacement work again after the light cleaning, thereby shortening the transport time of the reticle R and improving the throughput of the exposure apparatus. It becomes possible. When light cleaning is performed using illumination light that does not attenuate in the preliminary chamber 19 or has relatively small attenuation, light cleaning may be started before the replacement is started. Further, when the evacuation (vacuum evacuation) of the preliminary chamber 19 is started prior to the cleaning of the helium or the like, the optical cleaning may be started before the evacuation or during the evacuation. In addition, instead of replacing the inside of the preliminary chamber 19 with helium, etc., The same applies to the case where

 (Preliminary exposure)

 During the above light cleaning or gas replacement, the exposure light L from the exposure light source 1 is irradiated from the illumination optical system 2 to the projection optical system PL (preliminary exposure), and the projection optical system PL is saturated in advance. Heat to the temperature (preheating). In the present embodiment, the preheating of the projection optical system PL is performed, and transfer of the reticle pattern (main exposure to be described later) is started in a state where the temperature reaches a saturation point. Therefore, it is desirable that the projection optical system PL be designed so that desired optical performance is obtained when the temperature reaches the saturation point. Note that the estimation of the irradiation light amount or the saturation rise temperature of the projection optical system PL by the main control system 16 is determined in advance by, for example, a condition setting experiment. Accordingly, the main control system 16 can determine the pre-exposure light amount and the pre-exposure time for the projection optical system PL via the process program in order to guide the projection optical system PL to the saturation temperature.

 The irradiation conditions of the exposure light L (preliminary exposure light amount, preliminary exposure time, etc.) at the time of the preliminary exposure are determined according to the pattern density of the reticle R to be used. This is because, during the main exposure, the proportion of the exposure light L that passes through the reticle R and reaches the projection optical system PL changes depending on the pattern density of the reticle R.

 Based on the above calculated values, in the actual exposure operation, a command is sent to the illumination field stop in the light source 1 and the illumination optical system 2, and the exposure time (number of pulses and pulse energy) per shot and the size of the illumination area The temperature of the projection optical system PL is adjusted by changing the height.

 In addition, since the composition of the purge gas greatly affects the absorption of the exposure light, particularly in the vacuum ultraviolet region, the replacement of the gas in the preliminary chamber 19 must be performed with sufficient accuracy. It takes a certain time to carry in and out reticle R using 9. However, in this embodiment, by performing the pre-exposure using this time, there is an advantage that a decrease in the throughput (throughput) due to the execution of the pre-exposure can be reduced. [Transport to reticle stage]

Immediately after the gas is replaced to a sufficient level and the pre-exposure is completed, the shutter 22a is opened, and the reticle R is moved by the second reticle loader 20B. —Removal into space 2 2 inside reticle area (in reticle side chamber RC). At this time, by setting the pressure of the helium gas in the reticle-side chamber RC higher than that in the preparatory chamber 19, the inflow of gas from the preparatory chamber 19 can be suppressed. As a result, the reticle R is carried in and out of the spare room 19 without changing the gas composition or the degree of vacuum in the reticle side chamber RC.

 (Main exposure)

 The reticle R is loaded on the reticle stage 10 by the second reticle loader 20B, and the wafer W is loaded on the wafer holder 13 so that the main exposure can be performed. In this state, fine adjustment for obtaining a desired projection image, such as alignment adjustment of reticle R, baseline calibration for wafer W, and focus calibration is performed.

 At this time, since the projection optical system PL has already been heated to some extent (saturation point), the irradiation with the exposure light L at the time of exposure does not further increase the temperature and cause thermal expansion. Therefore, the fine adjustment is performed in substantially the same state as the actual exposure state, so that it can be performed with higher accuracy, and the fluctuation of the projection magnification of the reticle pattern and the distortion of the circuit pattern are further reduced.

 After the above steps are completed, the reticle pattern is exposed on the wafer W. As described above, in the projection exposure apparatus of the present embodiment, the preliminary exposure is performed using the gas replacement time in the preliminary chamber 19, so that no new apparatus is required, cost reduction and maintenance performance are reduced. Reduction of the drop is easily realized. Another advantage is that it does not depend on the temperature gradient caused by uneven irradiation in the reticle R.

 Furthermore, in the case of UV short-wavelength lithography, the exposure light source 1 has a large energy per photon, but the reticle R, which is a consumable item, has a higher durability than the glass material for the projection optical system PL. Generally, inferior glass materials are used. However, according to the present embodiment, the reticle R is not irradiated with the exposure light L during the pre-exposure, so that the temperature of the entire optical system can be adjusted without imposing a load on the reticle R.

In this embodiment, the projection optical system PL is pre-irradiated and its temperature is kept at a high temperature. It is preferable that the projection optical system PL to be used is designed in advance from the design and manufacturing stages so that the performance in the above-mentioned high temperature state is good. In addition, a mechanism that moves at least one of the plurality of optical elements that make up the projection optical system PL to adjust its optical characteristics (for example, including the focal position, projection magnification, and aberrations (such as distortion)), or two optical elements A mechanism or the like for changing the pressure in the sealed space between the elements to adjust the optical characteristics thereof may be provided.

 In the present embodiment, the operation of loading the reticle R into the reticle-side chamber RC when the temperature of the projection optical system PL is sufficiently lower than its saturation temperature has been described. When exchanging the reticle R when it is almost at the saturation point, for example, after the reticle R on the reticle stage 10 is carried out to the outside via the preparatory chamber 19, the next reticle is transferred via the preparatory chamber 19 This is also effective when the reticle stage 10 is placed on the reticle stage 10.

 Further, in this embodiment, the same gas (helium in this embodiment) is used for the reticle-side chamber RC and the preparatory chamber 19, but different gases may be used if the exposure light L is less absorbed. May be used. However, it is necessary that the impurity concentration in the preliminary chamber 19 be set to the same level as that of the reticle-side chamber R C, or to such an extent that the impurity concentration in the reticle-side chamber R C does not increase even when the shutter 22 a is opened. The gas used in at least one of the reticle-side chamber RC and the spare chamber 19 may be a gas obtained by mixing a plurality of gases at a predetermined ratio.

 Further, in this embodiment, the projection optical system PL is pre-heated by irradiating the exposure light L. However, illumination light different from the exposure light L may be used, or a heater or the like may be used for the projection optical system PL. May be attached.

 The present invention also includes the following embodiments.

 (1) In the above embodiment, the optical member of the projection optical system that is thermally stabilized by the preliminary irradiation (preliminary exposure) is a lens system. However, this technology uses, for example, a reflecting mirror or a prism to absorb the exposure light. This is also effective for an optical system including a member that generates heat.

(2) In the reticle transport system, a spare chamber 19 for replacing the atmosphere is provided to carry the reticle R into and out of the reticle side chamber RC, but the wafer transport system that transports the wafer W to the wafer stage 14 is provided. Unloads wafer W to wafer-side chamber WC In order to insert the wafer, a spare chamber for the wafer for which the atmosphere is similarly replaced may be provided.

(3) The application of the exposure apparatus is not limited to the exposure apparatus for semiconductor manufacturing. For example, an exposure apparatus for a liquid crystal for exposing a liquid crystal display element pattern to a square glass plate, a plasma display, a thin film The present invention can be widely applied to an exposure apparatus for manufacturing a magnetic head, an image sensor, a micromachine, and the like.

 (4) As the type of the exposure apparatus, not only the scanning exposure method (including the step-and-scan method) as in the above embodiment but also the static exposure method (including the step-and-repeat method). Can also be applied.

(5) Not only the F ₂ laser (157 nm) but also g-line (436 nm), i-line (365 nm), KrF excimer laser (248 nm), A r F excimer one the (193 nm), a r _2, single-tHE (126 nm), X-ray, a wavelength especially may be employed EUV light or the like of 13. 4 nm or 1 1. 5 nm. The EUV exposure apparatus uses a reflective reticle, a plurality of (for example, about 3 to 6) reflective elements (mirrors), and only the image plane side (wafer side) is telecentric. The system is used and the optical path is vacuum. In addition, instead of the above-mentioned excimer laser light, a single-wavelength laser in the infrared or visible range oscillated from a DFB semiconductor laser or a fiber laser, for example, is doped with erbium (or both erbium and yttrium). Harmonics amplified by a fiber amplifier and wavelength-converted to ultraviolet light using a nonlinear optical crystal may be used as illumination light for exposure. As an example, assuming that the oscillation wavelength of a single-wavelength laser is in the range of 1.544 to 1.553 zm, it is the 8th harmonic in the range of 193 to 194 nm, that is, almost the same wavelength as the ArF excimer laser. comprising ultraviolet light is obtained, when the oscillation wavelength 1. in the range of 57~1. 58 / zm, 1 0 harmonic in the range of 157 ~ 158 nm, i.e. ultraviolet to be substantially the same wavelength as the F ₂ laser Light is obtained.

 Considering the properties of the glass material used for the projection optical system, it is particularly preferable to use an exposure light source having a wavelength of 120 to 190 nm.

(6) The magnification of the projection optical system is not limited to the reduction system, but may be any of the same magnification and the enlargement system. (7) The projection optical system PL has a reticle pattern formed by a first optical system including a plurality of refraction elements and a pair of reflection elements, as disclosed in, for example, Japanese Patent Application Laid-Open No. H10-1040513. A catadioptric optical system that forms a primary image (intermediate image) and re-images the intermediate image by a second optical system including a plurality of refractive elements, or US Pat. No. 5,650,877 and US Pat. A catadioptric optical system that does not form an intermediate image, such as that disclosed in US Pat. No. 5,559,338, may be used.

 (8) When a linear stage (refer to U.S. Pat. Nos. 5,628,853 and 5,528,118) is used for the wafer stage and the reticle stage, air bearing is used. Either an air levitation type or a magnetic levitation type using Lorentz force or reactance force may be used. The stage may be a type that moves along a guide, or may be a guideless type that does not have a guide.

 (9) The reaction force generated by the movement of the wafer stage is mechanically released to the floor (ground) using a frame member (as described in US Pat. No. 5,528,118). May be.

 (10) The reaction force generated by the movement of the reticle stage is mechanically released to the floor (ground) using a frame member (as described in US Pat. No. 5,874,820). You may.

 (11) An illumination optical system and a projection optical system composed of a plurality of lenses are incorporated into the main body of the exposure apparatus for optical adjustment, and a reticle stage consisting of many mechanical parts. The exposure apparatus of the present embodiment can be manufactured by connecting the piping and performing further adjustments (electrical adjustment, operation confirmation, etc.). It is desirable that the exposure apparatus be manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

(12) The semiconductor device has the following steps: a step of designing the function of the device and a performance; a step of manufacturing a reticle based on this design step; a step of manufacturing a wafer from a silicon material; It is manufactured through a step of exposing a pattern to a wafer, a step of assembling a device (including a dicing step, a bonding step, and a package step), an inspection step, and the like. Further, according to the present invention, the following effects can be obtained. (1) Before the reticle is installed on the reticle stage, the projection optical system is irradiated with exposure light by the illumination optical system and heated, and immediately after this, the reticle is installed on the reticle stage and exposed. Therefore, before the reticle is guided on the exposure optical path, the heat generated by the absorption of the projection optical system can be saturated. Therefore, during actual exposure of the circuit pattern, focus calibration and the like are performed in a state where the thermal expansion is stable, and even when the exposure light is irradiated thereafter, the magnification of the projection circuit pattern changes, the distortion of the projected image, and the like. The time fluctuation can be suppressed as much as possible.

 Further, as a means for reducing a decrease in exposure accuracy, an adjustment mechanism existing in the exposure apparatus can be effectively used in combination. Further, the time required for the reticle placed on the light-collecting surface to receive light is shortened, so that the life of the reticle due to optical damage is not reduced.

 (2) In the preheating step, by changing the irradiation conditions of the exposure light according to the density of the reticle pattern used, the projection optical system takes into account the proportion of the exposure light that passes through the reticle and reaches the projection optical system. By heating the system, a high-precision preliminary exposure corresponding to the actual exposure can be performed.

 (3) When the reticle is transported to the preparatory chamber where the atmosphere is replaced, the time required for loading and unloading the reticle is used to preheat the projection optical system. ) Is prevented from decreasing. In addition, no new equipment is required for preheating, which prevents new costs.

 (4) By performing light cleaning in which the reticle is irradiated with light capable of removing impurities adhering to the reticle in the pre-chamber, the reticle can be pre-cleaned in the pre-chamber and the impurities adhering to the reticle can be cleaned. The influence of the exposure on exposure is suppressed. Accordingly, more accurate reticle transfer can be performed.

 (5) By performing the replacement step after the light cleaning step, the impurities blown off by the light cleaning can be discharged to the outside of the preliminary chamber at the time of replacement. Therefore, the inflow of impurities into the casing during the second transfer step is prevented.

 (6) A part of the exposure light from the illumination optical system is branched and irradiated to the reticle in the preparatory room to perform the light cleaning, so that there is no need to separately install a light cleaning light source, and the cost increases. Is suppressed.

(7) Set the wavelength of the exposure light from 120 nm to 190 nm and specify the wavelength within the casing. By the atmosphere to a clear gas to the exposure light, in the case of using the ultraviolet short-wavelength light source such as F ₂ lasers, decrease in light intensity due to absorption of exposure light on the gas on the optical path is suppression, As a result, in pre-exposure and main exposure, efficient irradiation with little loss is possible.

Claims

The scope of the claims 1. An exposure method for irradiating exposure light onto a mask placed on a mask stage by an illumination optical system and projecting and exposing a pattern on the mask to a substrate surface via a projection optical system,  A preheating step of heating the projection optical system by irradiating the projection optical system with exposure light by the illumination optical system in a state before the mask is placed on the mask stage;  An exposing step of exposing the mask by setting the mask on the mask stage immediately after the preheating step.  2. The exposure method according to claim 1, wherein in the preheating step, irradiation conditions of the exposure light are changed according to a density of a pattern of the mask to be used.  3. The inside of the casing that houses the mask stage is filled or vacuumed with a specific atmosphere,  A first transfer step of transferring the mask from the outside and temporarily storing the mask in a spare chamber provided between the casing and the outside in a state where the flow of the atmosphere between the casing and the spare chamber is blocked;  After the first transfer step, a replacement step of replacing the atmosphere in the preliminary chamber with the specific atmosphere or vacuum in a state where the flow of the atmosphere between the outside and the preliminary chamber is interrupted, And a second transporting step of transporting the wafer to the mask stage from  The exposure method according to claim 1, wherein the preheating step is performed during the replacement step.  4. The inside of the casing containing the mask stage is filled or vacuumed with a specific atmosphere.  A first transfer step of transferring the mask from the outside and temporarily storing the mask in a spare chamber provided between the casing and the outside in a state where the flow of the atmosphere between the casing and the spare chamber is blocked; A replacement step of replacing the atmosphere in the pre-chamber with the specific atmosphere or vacuum in a state where the flow of the atmosphere between the outside and the pre-chamber is interrupted after the first transfer step; A second transfer step of transferring the mask from the preliminary chamber to the mask stage after the replacement step,  The exposure method according to claim 2, wherein the preheating step is performed during the replacement step.  5. A light cleaning step of irradiating the mask with light capable of removing impurities adhering to the mask is provided between the first transfer step and the second transfer step. The exposure method according to claim 3, wherein:  6. The exposure method according to claim 5, wherein the replacement step is performed after the light cleaning step.  7. The exposure method according to claim 5, wherein in the light cleaning step, a part of the exposure light from the illumination optical system is branched and applied to the mask in the spare room.  8. The exposure light according to any one of claims 1 to 7, wherein the wavelength of the exposure light is from 120 nm to 190 nm, and the specific atmosphere is a gas transparent to the exposure light. The exposure method according to any one of the above.  9. A method of disposing a mask in a first chamber having a small amount of impurities that attenuate exposure light, irradiating the mask with the exposure light, and exposing a substrate with the exposure light via a projection optical system,  The mask is carried into a second chamber connected to the first chamber, and the projection optical system is heated substantially in parallel with the impurity concentration in the second chamber being equal to or lower than a predetermined allowable value. The first step,  A second step of moving the mask in the second chamber into the first chamber after the first step.  10. The exposure method according to claim 9, wherein a concentration of the impurity in the second chamber is substantially equal to a concentration of the impurity in the first chamber.  11. The exposure method according to claim 9, wherein a gas having low absorption of the exposure light is supplied into the first chamber and the second chamber, respectively.  12. The exposure method according to claim 11, wherein the projection optical system is heated by irradiating the exposure light. 13 3. In order to keep the concentration of the impurity below the allowable value, the absorption of the exposure light 10. The exposure method according to claim 9, wherein the second chamber is replaced with a small amount of gas, and light cleaning of the mask in the second chamber is started before the completion of the replacement.  1 4. An exposure apparatus that irradiates exposure light onto a mask placed on a mask stage by an illumination optical system and projects and exposes a pattern on the mask onto a substrate surface via a projection optical system.  A mask transport system that transports the mask to the mask stage,  A control system for controlling the mask transport system and the illumination optical system,  This control system irradiates the projection optical system with exposure light by the illumination optical system and heats it before the mask is set on the mask stage. An exposure apparatus characterized in that a mask is set on a mask stage and exposure is performed by an illumination optical system.  15 5. A casing in which the inside is filled with a specific atmosphere or a vacuum state, and the mask stage is housed,  A spare chamber provided between the casing and the outside,  A replacement device that replaces the atmosphere in the preliminary chamber with the specific atmosphere or vacuum while blocking the flow of the atmosphere between the outside and the preliminary chamber,  A first transfer system for transferring the mask from the outside to the preliminary chamber and temporarily storing the mask in a state where the flow of the atmosphere between the casing and the preliminary chamber is shut off; and A second transfer system for transferring the mask from the preliminary chamber to the mask stage in a state where the flow of the atmosphere is interrupted,  15. The heating system according to claim 14, wherein the control system performs the heating of the projection optical system by the illumination optical system when the mask is transported to the preliminary chamber by the first transport system. Exposure equipment.  16. The exposure according to claim 15, further comprising a light cleaning device that irradiates the mask in the preliminary chamber with light capable of removing impurities attached to the mask. 17. The exposure apparatus according to claim 16, wherein the light cleaning apparatus branches a part of the exposure light from the illumination optical system and irradiates the light to the mask in the preliminary chamber. 18. A first chamber having a small amount of impurities that attenuate exposure light, and the first chamber is disposed in the first chamber. An illumination optical system that irradiates the exposure light onto a mask to be transferred, and a projection optical system that irradiates the exposure light onto a substrate onto which a pattern of the mask is to be transferred, the exposure apparatus being connected to the first chamber, A second chamber into which the mask is carried in prior to the first chamber, a removing device for adjusting the concentration of the impurity in the second chamber to a predetermined allowable value or less, a heating device for heating the projection optical system,  An exposure apparatus, comprising: a control system that controls the removal apparatus and the heating apparatus, and that removes impurities in the second chamber and heats the projection optical system substantially in parallel.  19. A method for manufacturing a device, comprising a step of transferring a device pattern onto a sensitive substrate using the exposure apparatus according to any one of claims 14 to 18.