WO2002049084A1

WO2002049084A1 - Exposure method and system, and device producing method

Info

Publication number: WO2002049084A1
Application number: PCT/JP2001/010937
Authority: WO
Inventors: Naomasa Shiraishi
Original assignee: Nikon Corporation
Priority date: 2000-12-15
Filing date: 2001-12-13
Publication date: 2002-06-20
Also published as: JPWO2002049084A1; AU2002221133A1

Abstract

An exposure method and system capable of providing stable imaging characteristics even when gas other than a purge gas remains on the light path of exposure light, or even when the residual concentration of gas other than the purge gas varies. Vacuum-UV-region exposure light (IL) from an exposure light source (1) illuminates a reticle (R) to transfer the reticle's pattern image onto a wafer (W) via a projection optical system (PL). The reticle (R) and the wafer (W) are respectively housed in a reticle stage room (40) and a wafer stage room (60) that are air-tight rooms, the inside of the projection optical system (PL) is turned to an air-tight room, and purge gas transmitting the exposure light (IL) is supplied to those air-tight rooms from a gas purifying device (71). For example, imaging characteristics of the projection optical system (PL) are adjusted via an imaging characteristic controller (57) according to the residual concentration of gas other than the purge gas in the projection optical system (PL) so as to offset variation amounts of imaging characteristics caused by this residual concentration.

Description

Description Exposure method and apparatus, and device manufacturing method 'technical field.

The present invention transfers a mask pattern onto a photosensitive substrate during a photolithography process for manufacturing various devices such as a semiconductor device, an imaging device (CCD), a liquid crystal display device, or a thin film magnetic head. And an exposure method used for the method. Background art

In the photolithography process for forming fine patterns of electronic devices such as semiconductor integrated circuits and liquid crystal displays, a reticle (or photo) as a mask drawn by enlarging the pattern to be formed by a factor of about 4 to 5 times. A method of reducing and transferring a pattern of a mask or the like onto a wafer (or a glass plate or the like) as a substrate to be exposed using a projection exposure apparatus of a batch exposure type or a scanning exposure type is used.

In a projection exposure apparatus used for transferring the fine pattern, the exposure wavelength has been shifted to a shorter wavelength side in order to cope with miniaturization of a semiconductor integrated circuit. At present, the exposure wavelength is mainly 248 nm of KrF excimer laser, but ArF, which can be regarded as a shorter wavelength, substantially a vacuum ultraviolet region (VUV: Vacuum Ultra traviolet). Excimer lasers of 193 nm are also entering the stage of practical use. Then, it is shorter F ₂ laser and the wavelength 1 5 7 nm, also made suggestions of a projection exposure apparatus using exposure light source in the vacuum ultraviolet region, such as A r ₂ lasers having a wavelength of 1 2 6 nm. As described above, in recent projection exposure apparatuses, light in the vacuum ultraviolet region having a wavelength of about 200 nm or less has been used as exposure light. However, the light in the vacuum ultraviolet region has a small number of types of high-transmittance optical materials that can be used as illumination optical systems of projection exposure apparatuses, refractive members (lenses, etc.) of projection optical systems, and reticle substrates. Currently, optical materials that can be used are limited to fluoride crystals such as fluorite, magnesium fluoride, and lithium fluoride. In addition, vacuum ultraviolet light emits oxygen, water vapor, and hydrocarbons. Since the absorption by gas such as elemental gas (hereinafter referred to as “absorptive gas”) is extremely large, in a projection exposure apparatus using vacuum ultraviolet light, it is necessary to remove the absorptive gas from the optical path through which the exposure light passes. It is necessary to replace the gas in the optical path with a gas such as nitrogen or a rare gas that absorbs relatively little of the exposure light (hereinafter referred to as “low-absorbing gas”). The gas used to actually replace the gas in the optical path among the low-absorbing gases is called "purge gas".

Regarding the allowable residual concentration of the absorbing gas, for example, for oxygen, it is necessary to keep the average concentration of the exposure light in the optical path below the allowable level on the order of ppm. If the residual concentration of the absorbing gas exceeds the allowable level as described above, the exposure energy on the wafer as the substrate to be exposed will be significantly reduced. Also, depending on the type of the absorbing gas, its refractive index is significantly different from that of the above-mentioned purge gas. Therefore, if an absorbing gas different from the type of the purge gas remains on the optical path, the refractive index on the optical path fluctuates depending on the residual concentration, and the imaging characteristics of the projection optical system greatly fluctuate. As a result, the transferred image may be degraded. Furthermore, this difference in refractive index occurs not only between the absorbing gas and the low-absorbing gas, but also between two low-absorbing gases (eg, helium and nitrogen). Therefore, it is desirable that the residual concentration of the gas other than the purge gas that replaces the optical path of the exposure light be kept as low as possible even if it is a low-absorbing gas.

The residual gas having a different refractive index from the purge gas not only changes the refractive index of the optical path of the exposure light, but also changes the wavelength of a measurement beam for a laser interferometer for position measurement of a reticle stage or a wafer stage. This has an adverse effect on the reticle and wafer position measurement accuracy.

In addition, since the projection exposure apparatus is required to have an alignment accuracy of about 1 Z4 of its resolution, an alignment mechanism for aligning the reticle and the wafer with high accuracy is provided. In particular, when a light beam having an exposure wavelength is used for alignment (position detection) of a reticle, the optical system of the alignment sensor for detecting the position of the reticle has a high transmittance for a light beam having an exposure wavelength. Must have. In addition, when the exposure wavelength is in the vacuum ultraviolet region of about 200 nm or less, absorption due to a trace amount of organic or silane-based impurities or a photochemical reaction between the exposure light and the impurities may occur. The resulting fogging material build-up and reduced lens transmission are serious problems. Therefore, a member that generates impurities, for example, a plastic substrate used in an electric circuit for processing an output signal of a photoelectric detector (such as an imaging device) installed on a detection surface of an alignment optical system, is used. It is necessary to avoid disposing it in a space including the optical path of the exposure light. Therefore, the photoelectric detector, which was conventionally arranged in the space including the optical path of the exposure light, should also be installed in the atmosphere outside the space.However, there is also a problem that the vacuum ultraviolet light does not pass through the normal atmosphere. is there.

In view of the above, the present invention provides an exposure apparatus capable of obtaining a stable imaging characteristic even if a gas other than the purge gas remains on the optical path of the exposure light, or even if the residual concentration of the gas other than the purge gas fluctuates. The primary purpose is to provide technology.

A second object of the present invention is to provide an exposure technique that can use an alignment system suitable for using illumination light having a wavelength range similar to that of short-wavelength exposure light such as a vacuum ultraviolet region. .

In addition, the present invention has an adverse effect on the optical path when the purge gas is supplied on the optical path using illumination light having a wavelength range similar to the short-wavelength exposure light such as a vacuum ultraviolet region. A third object is to provide an exposure technique capable of setting an alignment system for a reticle or a wafer without giving it. Disclosure of the invention

A first exposure apparatus according to the present invention is an exposure apparatus that exposes a second object (W) via a first object () with an exposure beam having a wavelength of 200 nm or less, wherein the first object or the second object is exposed. An alignment optical system (90, 92) that collects alignment light having substantially the same wavelength as the exposure beam that has passed through the mark (RM) above, and is collected by the alignment optical system. A mark detection system having a photoelectric detector (94) for detecting the alignment light is provided, and the refraction members in the alignment optical system are all formed of an optical material that transmits the exposure beam.

According to the present invention, the transmittance of the alignment optical system of the mark detection system using alignment light (illumination light) substantially equal to the exposure beam in the vacuum ultraviolet region is increased, and the illumination efficiency is increased. An alignment can be made. In this case, an example of the optical material that transmits the exposure beam is fluorite or quartz to which fluorine is added.

Further, it is desirable to replace the gas on at least a part of the optical path of the alignment light and the gas inside the partition (40) in which the photoelectric detector is housed with a gas that transmits the exposure beam. Thereby, the SN ratio of the detection signal of the photoelectric detector can be increased.

Furthermore, it is desirable to provide an intake port (40a) for inhaling gas inside the partition in a region of the partition adjacent to the photoelectric detector (94). As a result, degassed (absorptive gas) from the photoelectric detector is exhausted from the intake port, so that there is no adverse effect such as a decrease in transmittance on the optical path of the exposure beam.

Further, a part of the alignment optical system may include a hollow member (80) provided with a reflection member for reflecting the alignment light on an inner wall thereof. As a result, the alignment light can be transmitted efficiently.

The alignment optical system further includes a light-sending optical system (8) for irradiating alignment light having substantially the same wavelength as the exposure beam to a mark on the first object or the second object. The light transmitting optical system may include a hollow member (80) provided with a reflecting member for reflecting the alignment light on the inner wall thereof. In the case where, for example, a beam split from the exposure beam is guided as alignment light by the light transmitting optical system, it is not necessary to separately provide a light source for the alignment light.

Next, a first exposure method according to the present invention is directed to an exposure method for exposing a second object (W) via an exposure beam through a first object (R) and a projection optical system (PL). Replacing the gas in at least a part of the optical path with a first gas that transmits the exposure beam, and measuring the concentration of a second gas different from the first gas remaining in the at least a part of the optical path, The imaging characteristic of the projection optical system is adjusted according to the residual concentration of the second gas.

In the present invention, when the second gas remains in the optical path of the exposure beam, the refractive index of the optical path fluctuates in accordance with the residual concentration, and the image forming characteristic of the projection optical system (for example, Aberrations such as distortion) fluctuate. Therefore, as an example, the imaging characteristics of the projection optical system are adjusted so as to cancel the fluctuation amount of the imaging characteristics. Thus, the imaging characteristics can be stably maintained in a desired state.

In particular, when the exposure beam is vacuum ultraviolet light having a wavelength of about 200 nm or less, the type of the first gas (low-absorbing gas) that transmits the exposure beam is limited, and the type of the first gas is low on the optical path. Even when a certain amount of gas other than the first gas is mixed, stable imaging characteristics can be obtained by the present invention.

In this case, when the residual concentration of the second gas exceeds a predetermined level, it is desirable to replace the gas in at least a part of the optical path with the first gas. As a result, the fluctuation amount of the imaging characteristic does not become too large, and the imaging characteristic can always be maintained in a desired state.

Further, the second gas may be a gas that transmits the exposure beam. Even if the second gas is a low-absorbing gas that transmits the exposure beam, as in the case of the first gas, the difference in the refractive index between the first and second gases causes a difference in the light path. The present invention is effective because the refractive index fluctuates.

In these cases, assuming that the first gas is nitrogen, by way of example, the second gas is at least one gas selected from the group consisting of oxygen, carbon dioxide, steam, neon, and helium.

On the other hand, if the first gas is helium, as an example, the second gas is at least one gas selected from the group consisting of oxygen, nitrogen, carbon dioxide, water vapor, neon, argon, and krypton. is there.

Next, a second exposure method of the present invention is directed to an exposure method for exposing a second object (W) via an exposure beam through a first object (R) and a projection optical system (PL). Replacing the gas in at least a part of the optical path with a first gas that transmits the exposure beam, remaining in at least a part of the optical path, and transmitting the exposure beam and different from the first gas The second gas is measured for concentration, and when the residual concentration of the second gas exceeds a predetermined level, the gas in at least a part of the optical path is replaced with the first gas.

According to the present invention, when the residual concentration of the exposure beam of the second gas, which is composed of the low-absorbent gas but is different from the first gas, on the optical path increases, the gas on the optical path Is replaced by the first gas, the fluctuation of the refractive index in the optical path increases, As a result, the imaging characteristics can be easily maintained in a desired state. In this case, assuming that the first gas is nitrogen, as an example, the second gas is at least one of neon and helium.

On the other hand, if the first gas is helium, by way of example, the second gas is at least one gas selected from the group consisting of nitrogen, neon, argon, and krypton.

Next, a second exposure apparatus of the present invention is an exposure apparatus that exposes a second object (W) via a first object (R) and a projection optical system (PL) with an exposure beam. An imaging characteristic adjusting device (54 al, 54 a 2, 57) for adjusting the imaging characteristic, and exposing the gas of at least a part of the optical path of the exposure beam to the second object to the exposure object. A gas supply mechanism (71) that replaces the beam with a first gas that passes through the beam, and a gas sensor (7) that measures the concentration of a second gas that is different from the first gas and remains in at least a part of the optical path. 2) and a control system (10) for adjusting the imaging characteristics of the projection optical system via the imaging characteristic adjusting device based on the measurement values of the gas sensor.

Further, a third exposure apparatus of the present invention is an exposure apparatus that exposes a second object (W) via a first object (R) and a projection optical system (PL) with an exposure beam. A gas supply mechanism (71) for replacing gas in at least a part of the optical path to the second object with a first gas that transmits the exposure beam, and a gas supply mechanism that remains in at least a part of the optical path and exposes the gas. A gas sensor that transmits the beam and measures the concentration of a second gas different from the first gas, and a gas supply mechanism that controls the gas supply mechanism, and based on the measured value of the gas sensor, A control mechanism (10) for re-substituting the gas in a part of the optical path with the first gas.

With these exposure apparatuses, the exposure method of the present invention can be performed.

Next, the device manufacturing method of the present invention includes a step of transferring the device pattern (R) onto the workpiece (W) by using any of the exposure methods of the present invention. According to the present invention, since stable imaging characteristics can be obtained, various devices can be mass-produced with high accuracy. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a partially cutaway configuration view showing a projection exposure apparatus according to an example of an embodiment of the present invention. FIG. 2 is a sectional view showing the configuration of the projection optical system PL in FIG. FIG. 3 is an enlarged view, partially cut away, showing the configuration of the reticle alignment microscope 86 in FIG. FIG. 4 is a diagram illustrating an example of a manufacturing process when a semiconductor device is manufactured using the projection exposure apparatus according to the embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to the drawings. In this example, the present invention is applied to a projection exposure apparatus using vacuum ultraviolet light (VUV light) as an exposure beam.

FIG. 1 is a schematic configuration diagram showing a projection exposure apparatus of this example. In FIG. 1, for example, an exposure light source 1 and an exposure main body are placed in a clean room on a floor F1 on a certain floor of a semiconductor device manufacturing factory. The gas purifier 71 is installed in the machine room on the floor F2 below that floor. As the exposure light source 1, an F ₂ laser (fluorine laser) having an oscillation wavelength of 157 nm in the vacuum ultraviolet region is used. Other exposure light sources include a Kr ₂ laser (krypton dimer laser) with an oscillation wavelength of 146 nm, an Ar ₂ laser (argon dimer laser) with an oscillation wavelength of 126 nm, and an A with an oscillation wavelength of 193 nm. The present invention is also effective when a substantially vacuum ultraviolet light source such as an rF excimer laser, a harmonic generator of a YAG laser, or a harmonic generator of a semiconductor laser is used. Furthermore, when using a light source such as a KrF excimer laser (wavelength: 248 nm) or a mercury lamp (i-line, g-line, etc.) as the exposure light source, especially when it is desired to use the exposure light more efficiently To which the present invention can be applied.

Exposure light IL as an exposure beam emitted from the exposure light source 1 passes through a beam matching unit (BMU) 2 including a relay lens 21, a mirror 22 for bending the optical path, and relay lenses 23 and 24. And enters the illumination optical system 3. The exposure light IL incident on the illumination optical system 3 is disposed on the exit surface side of a flyer lens 31 (an optical integrator of a rod type can be used instead) as an optical integrator. Aperture stop for illumination system (σ stop) 32, The light reaches the field stop 36 via the first relay lens group 33, the mirror 34, and the second relay lens group 35. The exposure light IL that has passed through the field stop 36 passes through the first condenser lens group 37, the mirror 38 for bending the optical path, and the second condenser lens group 39 to pass through the pattern area of the reticle R as a mask. Light up.

The beam matching unit 2 and the illumination optical system 3 of the present example are respectively housed in sub-chambers 20 and 30 as highly airtight partitions (airtight chambers). In this case, the boundary between the two sub-chambers 20 and 30 may be connected to each other. For example, a parallel flat glass may be installed at the boundary or a relay lens 24 may be used instead of the parallel flat glass. The two sub-champers 20 and 30 may be isolated from each other by installing a suitable optical member and sealing the periphery thereof. This is the same for the following hermetic rooms. The airtight chamber may have some gaps as long as the outside air does not enter the sub-chambers 20 and 30.

In FIG. 1, a light beam transmitted through a reticle R forms an image of a pattern of the reticle R on a wafer W as a substrate to be exposed via a projection optical system PL. The reticle R and the wafer W correspond to the first object and the second object of the present invention, and the wafer W is, for example, a semiconductor (silicon or the like) or S〇I (silicon on insulator) or the like. It is a disk-shaped substrate. The inside of the projection optical system PL is an airtight chamber isolated from the outside air. Hereinafter, the Z axis is taken parallel to the optical axis AX of the projection optical system PL, the X axis is taken parallel to the plane of Fig. 1 in a plane perpendicular to the Z axis, and the Y axis is taken perpendicular to the plane of Fig. 1. explain. First, the reticle R is held on a reticle stage 41 mounted movably in the X and Y directions on a reticle base 42, and the two-dimensional position of the reticle stage 41 is determined by a laser interferometer 4 3 and a movable mirror arranged corresponding to the reticle stage control based on the measured values and the control information from the main control system 10 on the floor F2 that controls the overall operation of the device. A system (not shown) controls the position and speed of the reticle stage 41. A reticle stage system 4 is composed of a reticle base 42, a reticle stage 41, and a driving mechanism (not shown). The reticle stage system 4 is a reticle stage chamber 40 as a highly airtight partition (airtight chamber). Is housed inside.

On the other hand, the wafer W is moved to the wafer stage (Z level) via a wafer holder (not shown). The wafer stage 61 is mounted on the wafer base 62 so as to be movable in the X and Y directions. The two-dimensional position of the wafer stage 61 is measured by the laser interferometer 63 and a movable mirror corresponding to the laser interferometer 63, and is based on the measured values and control information from the main control system 10. A stage control system (not shown) controls the position and speed of the wafer stage 61 in the X and Y directions. Also, the wafer stage 61 is provided with information on focus positions (positions in the optical axis AX direction) at a plurality of measurement points on the surface of the wafer W from an auto focus sensor (not shown, an optical sensor of an oblique incidence type). The focus position of the wafer W and the tilt angles around the X-axis and the Y-axis are controlled by the servo method so that the surface of the wafer W is focused on the image plane of the projection optical system PL during the exposure. The wafer stage system 6 is composed of the wafer base 62, the wafer stage 61, and a driving mechanism (not shown). The wafer stage system 6 is a wafer stage chamber as a highly airtight partition (airtight chamber). Stored in 60.

At the time of exposure, the reticle R and the wafer W are projected onto one shot area on the wafer W via the projection optical system PL through the projection optical system PL, and the reticle R and the wafer W are projected in the Y direction using the speed ratio of the projection optical system PL as a speed ratio. The operation of synchronously moving the wafer W and the operation of stepping the wafer W are repeated in a step-and-scan manner. As described above, the projection exposure apparatus of this embodiment is of the scanning exposure type, but it goes without saying that the present invention is also effective for a batch exposure type projection exposure apparatus such as a stepper. Above the reticle stage 41 in the reticle stage room 40, an imaging type reticle alignment microscope 86 as an alignment system for the reticle R is arranged. The reticle alignment microscope 86 of this example uses light having the same wavelength as the exposure light IL as alignment light. Therefore, the illumination light IL 1 for alignment that is branched from the optical path of the exposure light IL by the half mirror 81 arranged between the relay lens 23 and the relay lens 24 in the beam matching unit 2 The light is guided to a reticle alignment microscope 86 via an alignment light transmitting system 8 disposed in a long and narrow airtight chamber 80 provided between the chamber 20 and the reticle stage chamber 40. The alignment light transmission system 8 is on the beam matching unit 2 side And a lens 82, an optical path bending mirror 83, 84, and a lens 85.

In this regard, when the exposure wavelength is a long wavelength exceeding 200 nm, light branched from the exposure light can be guided to the alignment system through a flexible optical fiber bundle. However, in the case where the exposure light IL in the vacuum ultraviolet region is used as in this example, it is difficult to obtain a cheap optical fiber that can transmit the illumination light in that wavelength region with a small loss of light amount at present. In this example, the illumination light is transmitted through an alignment light transmission system 8 consisting of a refraction member and a reflection member.

Further, the projection optical system PL of this example incorporates an imaging characteristic adjustment mechanism (detailed later) for adjusting (controlling) the imaging characteristics such as distortion and astigmatism within a predetermined range. I have. The main control system 10 sends control information S2 to the imaging characteristic controller 57 to adjust the imaging characteristics so that the imaging characteristics of the projection optical system PL fall within a predetermined target range.

When the vacuum ultraviolet light is used as the exposure light IL as in this example, the exposure light IL such as oxygen, water vapor, carbon dioxide (CO _2, etc.), and hydrocarbon-based (organic) gas is emitted from the optical path. It is necessary to eliminate “absorbent gas”, which is a gas that has a strong absorption rate for water. On the other hand, the gas that transmits the exposure beam, that is, in this example, the “low-absorbing gas” that has low absorption of the exposure light I in the vacuum ultraviolet region includes nitrogen and rare gases (helium, neon, argon, krypton, xenon, radon ), And their mixtures. The projection exposure apparatus of this example uses the “purge gas” selected from these low-absorbing gases based on, for example, the required stability of the imaging characteristics and the operation cost, and uses the exposure light source 1 A gas exchange mechanism (gas supply mechanism) is provided to replace the gas on the entire optical path of the exposure light IL from the wafer to the wafer W as the substrate to be exposed. In FIG. 1, the optical paths of the exposure light IL from the exposure light source 1 to the wafer W are the first sub-chamber 20 and the second sub-chamber 30 as an airtight chamber, the reticle stage chamber 40, and the projection optical system PL, respectively. , And are divided into optical paths inside the Jehachi stage room 60. The gas exchange mechanism of this example is composed of a gas purifying device 71 installed on the floor F2, a plurality of sub-chambers 20 as sub-chambers, a sub-chamber 30 and a reticle stage room 4 from the gas purifying device 71. 0, inside projection optical system PL, and wafer stage An air supply pipe 11 A to 15 A with an electromagnetic valve for supplying a purge gas to each of the chambers 60, and an exhaust pipe 11 1 B to 5 B with an electromagnetic valve for collecting the gas in the hermetic chamber, And an impurity concentration meter 72 (gas sensor) for measuring the residual concentration of a predetermined impurity gas other than the purge gas in the gas collected and installed in the exhaust pipes 11 B to 15 B. In FIG. 1, only the air supply pipe 14A and the exhaust pipe 14B for the projection optical system PL are connected to the gas purification device 71 to make the drawing easier to see, but the other air supply pipes 11A to 13A , 15A, and the exhaust pipes 11B to 13B, 15B are similarly connected to the gas purifier 71, respectively. Furthermore, an impurity concentration meter similar to the impurity concentration meter 72 is installed in each of the exhaust pipes 11B to 13B and 15B.

Further, the gas purifier 71 of this example has an exhaust factory pipe 16A for releasing the gas having an increased impurity concentration from the collected gas to the outside at any time, and a high-purity purge gas to the outside gas. A gas supply pipe 16B for refilling the gas purifier 71 from a source (not shown) is connected.

When the type of par purge gas for replacing the gas inside the sub-chamber 20 to the wafer stage chamber 60 depending on the exposure wavelength, for example, for an F ₂ laser having a wavelength of 1 57 nm as the exposure light IL, the wavelength Since nitrogen gas has a high transmittance in the atmosphere, inexpensive nitrogen gas can be used as the purge gas. However, the interior of the purge gas of the projection optical system PL, and nitrogen or other low refractive index as compared with the gas, therefore the density rocking Ragya temperature is desirably _c specifically the use of high optical stability helium to changes In addition, helium gas has a thermal conductivity that is about three times higher than that of neon and about six times that of nitrogen gas, and is excellent in temperature stability. And about 1/8 of nitrogen gas.

At present, optical materials for refractive members (such as lenses) having good transmittance for vacuum ultraviolet light are fluorite (CaF ₂ ), magnesium fluoride (MgF ₂ ), and lithium fluoride ( (LiF) etc., but fluoride crystals generally have a large coefficient of thermal expansion, and the lens may expand due to a rise in temperature due to absorption of exposure light, resulting in poor imaging characteristics. I am concerned. Also in this regard, if helium is used as a purge gas, helium has a high thermal conductivity and also has a cooling effect on the lens. Since it is excellent, it is possible to suppress the deterioration of the imaging characteristics due to the expansion of the lens. Nitrogen can also be used as a purge gas for the optical path of the exposure light I inside the wafer stage chamber 60 ゃ reticle stage chamber 40. However, the optical path of the laser interferometer 63 for measuring the position of the wafer W and the optical path of the laser interferometer 43 for measuring the position of the reticle R are refracted in order to maintain high measurement accuracy. It is desirable that the fluctuation of the rate (optical path length) be small. Therefore, even as a purge gas for the optical path of the laser sensitometers 43 and 63, that is, a purge gas inside the reticle stage chamber 40 and the wafer stage chamber 60, the refractive index is low, and density fluctuations and temperature fluctuations occur. It is desirable to use helium which has a small change in the optical path length with respect to.

In the case of using the wavelength 1 2 7 nm argon dimer laser (A r ₂ Les monodentate) as the exposure light IL, since nitrogen also becomes absorptive gas, gas that can be used as the purge gas, such as helium Of rare gases.

Next, the operation of the gas exchange mechanism including the gas purifying device 71 will be described by taking as an example a case where the gas inside the projection optical system PL is replaced with a purge gas. In FIG. 1, gas collected from inside the projection optical system PL through the exhaust pipe 14B enters an impurity concentration meter 72 such as a mass spectrometer, and the concentration (residual concentration) of the impurity gas in the gas is reduced. The measured information is output to the main control system 10 as a signal S1. In this case, the purge gas and the impurity gas correspond to the first and second gases, respectively, of the present invention, and the impurity gas is one of the above-mentioned absorptive gases which is a management target gas remaining in the optical path of the exposure light. It is. When the impurity gas remains in the projection optical system PL, not only the transmittance of the exposure light passing through the projection optical system PL but also the image forming characteristics of the projection optical system PL are affected by the refractive index of the impurity gas. Effect. Therefore, unlike other airtight chambers, the concentration of impurity gas is measured. In particular, in the present embodiment, the residual concentration of a specific low-absorbency gas other than the purge gas contained in the impurity gas is measured (details will be described later).

The gas that has passed through the impurity concentration meter 72 in the exhaust pipe 14 B is collected by the gas purifier 71. The gas purifier 71 has a HEPA filter (high-efficiency part iculate ai rf ilter) and a chemical filter for removing fine foreign matter such as dust. Oxygen, water vapor, carbon dioxide, and Absorbing gases such as organic and organic gases are removed by the chemical filter. In the gas purifying device 71, the absorbing gas in the impurity gas is removed, and the gas from which the absorbing gas has been removed is supplied into the projection optical system PL through the air supply pipe 14A. At that time, the residual concentration of absorbent gas as an impurity has been suppressed, for example, to 1 ppm or less, respectively.

Since vacuum ultraviolet light is also absorbed by water vapor, it is desirable to provide a removal device for removing water vapor in the gas purification device 71.

In these cases, the interior of the projection optical system PL, the air supply pipe 14A, and the exhaust pipe 14B naturally have an airtight structure. However, especially for the lens holding structure at the end of the projection optical system PL on the reticle side or wafer side, it is difficult to achieve both the mechanical accuracy required from the imaging performance of the projection optical system PL and a completely airtight structure. In some cases, a small amount of external gas (air) enters the space (such as the lens barrel of the projection optical system PL) to which the purge gas is supplied from the lens holding structure. The main components of the gas (air) to be mixed are nitrogen, oxygen, argon, etc. The oxygen in this is purified using a simple adsorbent whose main component is a powder of a metal such as iron or magnesium. It can be easily absorbed (removed) by a vessel.

On the other hand, it is difficult to remove nitrogen and argon present in air at about 1% by such a simple adsorbent.A small amount of gas such as nitrogen or argon mixed in the purge gas is not removed. There is a risk of accumulation.

Similarly, for other airtight chambers (subchambers 20, 30; reticle stage chamber 40, wafer stage chamber 60), purge gas from which absorbent gas has been removed using gas purifier 71. Has replaced the gas inside. At this time, the electromagnetic valves of the air supply pipes 11A to 15A and the exhaust pipes 11B to 15B are opened and closed in order to independently supply the purge gas to each of the plurality of hermetic chambers. As described above, in this example, the purge gas is supplied to each of the hermetic chambers independently using one gas purifier 71, but the gas purifier 71 is individually supplied to all the hermetic chambers. A purge gas may be supplied completely independently by installing a gas purifier similar to that described above. In addition to this, for example, the sub-chambers 20 and 30 and the reticle stage chamber 40 are regarded as one hermetic chamber as a whole, and a common gas purifying device 71 is used. The purge gas may be supplied in common. For example, when the optical path of the exposure light IL is divided into a plurality of parts and different types of purge gas are supplied to each of the divided optical paths, a gas purifying device may be provided for each type of purge gas.

Further, as described above, regarding the projection optical system PL, the residual concentration of a specific low-absorbing gas other than the purge gas is measured. For example, when helium is used as the purge gas, other low-absorbing gases do not absorb the exposure light much, but since their refractive index is larger than that of helium, they are projected due to an increase in their residual concentration. The refractive index of the optical path in the optical system PL may increase, and the imaging performance of the projection optical system PL may deteriorate. Further, these low-absorbing gases are hardly chemically reacted, and it is difficult to sufficiently remove them with the above-described chemical filter in the gas purification device 71.

Nevertheless, in order to remove these low-absorbing gases, as an example, the gas collected in the gas purifier 71 shown in Fig. 1 and passed through the chemical filter can be cooled by a refrigerator using a Stirling engine or the like. The gas is supplied to a low-absorbing gas removing device (not shown) such as a cooling device such as a cryopump, and the entire gas is converted to the boiling point of these gases (185.9 ° C in argon, nitrogen Then, cool down to less than 195.8 ° C) to liquefy and remove these gases (all low-absorbing gases except for the helium), and supply the high-purity purge gas thus obtained to each hermetic chamber. do it.

Such a low-absorbing gas removing apparatus is large, consumes large power, and is a source of vibration. Therefore, it is not preferable to install the apparatus near the exposure apparatus. In addition, since nitrogen and rare gases, which are low-absorbing gases, hardly absorb exposure light, even if they are mixed in the purge gas, the transmittance is maintained at a high level, and there is no problem such as a decrease in exposure amount. . Therefore, in this example, in order to obtain stable imaging characteristics without using such a low-absorbing gas removing device, for example, when helium is used as a purge gas, the gas inside the projection optical system PL is When a predetermined low-absorbing gas containing nitrogen or a rare gas (other than helium) is mixed, its concentration is measured, and the state of the projection optical system 5 is positively changed based on the measured value. Therefore, the deterioration (aberration fluctuation) of the imaging characteristics is corrected.

Therefore, the impurity concentration meter 72 composed of the mass spectrometer etc. In the gas inside the projection optical system PL that is supplied through the filter, the concentration (residual concentration) of a specific low-absorbing gas other than the above-mentioned absorbing gas in addition to the above-mentioned absorbing gas is measured, and the measurement information is sent to the signal S. Output as 1 to the main control system 10. When the purge gas is helium, the low-absorbency gas whose concentration is to be measured is nitrogen and a rare gas other than helium. The measurement information of the concentration indicates the concentration of each low-absorbing gas in the gas in the projection optical system PL, and the refractive index of the gas in the projection optical system PL can be calculated from the concentration information. It becomes possible. The main control system 10 predicts the amount of change in the imaging characteristics (distortion, etc.) of the projection optical system PL from the calculated refractive index, and sends it to the imaging characteristic controller 57 so as to cancel the amount of change. The control information S2 is sent, and a predetermined optical member in the projection optical system PL is driven accordingly. As a result, even if another kind of low-absorbing gas is mixed in the purge gas in the projection optical system PL, the imaging characteristics of the projection optical system PL can be improved without using an expensive low-absorbing gas removing device. Exposure can be maintained with high accuracy while maintaining a desired state.

The low-absorbing gases that are expected to be mixed under actual use conditions are nitrogen and argon, which have a large composition in the atmosphere. , Nitrogen and argon, or only nitrogen.

Here, an example of the imaging characteristic adjusting mechanism of the projection optical system PL will be described with reference to FIG.

FIG. 2 is a cross-sectional view showing a detailed configuration of the projection optical system PL. In FIG. 2, the projection optical system PL has, as an example, four lens holders 55a to 55a in a cylindrical lens barrel 51. The first lens group L 11, L 12, the second lens group L 21, L 22, the third lens group L 31, L 32, and the fourth lens group through 5 5 d The lenses L 41 and L 42 are held. Note that the configuration of the lens groups is an example, and the number of the lens groups, the number of lenses in each lens group, and the like are arbitrary. The lens barrel 51 has an airtight structure, and the reticle stage chamber 40 side (upper side in FIG. 2) has a transmission window made of a fluoride crystal such as fluorite in order to transmit an exposure light beam and maintain airtightness. 5 2 are arranged. Further, a transmission window 53 having a similar configuration is arranged on the wafer stage chamber 60 side (the lower side in FIG. 2). Further, although not shown in FIG. 2, An air supply pipe 14 A and an exhaust pipe 14 B in FIG. 1 are connected to the lens barrel 51.

In FIG. 2, the first lens holder 55a is connected to a lens barrel 51 via, for example, three holding mechanisms 54a1 and 54a2 (the third holding mechanism is not shown, the same applies hereinafter). Similarly, the second to fourth lens holders 55b, 55c, and 55d also have three holding mechanisms 54b1, 54b2, and 54c respectively. 1, 54 c 2 and the holding mechanism 54 d 1, 54 d 2 are held in the lens barrel 51. Each of these holding mechanisms 5 4 al to 5 4 d 2 includes a small movable member such as a piezo element or a motorized micro-mechanism therein, whereby the lens holders 55 a to 55 d respectively The position of the projection optical system PL in the direction of the optical axis and the inclination angle around two orthogonal axes on a plane perpendicular to the optical axis can be adjusted within a predetermined minute range. In addition, by further increasing the degree of freedom of driving by the holding mechanism, for example, a predetermined lens holder in the lens holders 55a to 55d is displaced in two directions orthogonal to a plane perpendicular to the optical axis, or You may make it rotate around an axis. The holding mechanisms 54a1 to 54d2 are driven by the imaging characteristic controller 57 independently of each other.

Then, in accordance with the control information S 2 from the main control system 10 in FIG. 1, the positions and inclination angles of the lens holders 55 a to 55 d are determined by the imaging characteristic controller 57 so that the control information S 2 Is set to the state specified by. Since the control information S 2 is generated so as to offset the fluctuation amount of the imaging characteristics due to the residual concentration of the low absorption gas measured by the impurity concentration meter 72 in FIG. 1, the projection optical system The imaging characteristics (aberration characteristics) of the system PL are maintained in a desired state.

Note that the fluctuation of the imaging state of the projection optical system PL (the fluctuation of aberration) is not caused only by the change of the composition of the gas in the optical path. This is performed based on other factors, such as fluctuations in atmospheric pressure and the history of exposure energy absorbed by the projection optical system PL. In addition, it is possible to determine from the design data of the projection optical system PL which lens block should be moved and how much with respect to the history of gas composition, atmospheric pressure fluctuation, and exposure energy. In order to increase the control accuracy, the imaging state is evaluated while actually varying the gas composition, atmospheric pressure, exposure energy history, etc. using the projection optical system PL, and the control parameters are determined based on the results. One night is determined, and this control parameter is stored as a table You may.

To substantially control the imaging characteristics of the projection optical system PL, the wavelength of the exposure light may be shifted in addition to driving the optical elements in the projection optical system PL. The position of the wafer 1 (reticle R) and the position of the wafer stage 61 (wafer W) (for example, the position in the Z direction) may be controlled.

Although the projection optical system PL of this example is a refractive system, in order to satisfactorily correct chromatic aberration by using a small number of optical materials in the vacuum ultraviolet region, the projection optical system PL is, for example, disclosed in International Publication (W 0) 00 / As disclosed in 39623, as a straight cylindrical catadioptric system configured by arranging a plurality of refractive lenses along one optical axis and two concave mirrors each having an opening near the optical axis. Alternatively, a catadioptric system or the like having an optical axis bent in a V-shape may be used. In these configurations, the concave mirror (reflection member) may be movable in order to adjust the imaging characteristics.

Note that there is a limit to aberration correction as described above, and when the purge gas is helium and the concentration of other nitrogen or argon becomes a certain level or more, for example, 100 ppm or more, the correction is no longer performed. Becomes difficult. In this case, when the concentration of nitrogen or argon or the like in the impurity concentration meter 72 shown in FIG. 1 becomes equal to or higher than a predetermined concentration (for example, 100 ppm as described above), the gas was collected by the gas purification device 71. The gas may be discharged to the outside through the exhaust pipe 16A, and a new high-purity purge gas may be supplied to the gas purifier 71 through the air supply pipe 16B instead. Then, the gas inside the projection optical system PL may be replaced with the supplied high-purity purge gas. Thereby, the imaging characteristics can be maintained in a desired state.

Instead of replenishing the gas purifying device 71 with the purge gas through the pipe 16 B, a purge gas cylinder (for example, a helium cylinder) is connected to the gas purifying device 71, and if necessary, The gas may be replenished from the cylinder.

In the embodiment described above, the projection optical system PL is targeted for gas replacement with a purge gas (particularly helium), measurement of the concentration of a low-absorbent gas (nitrogen or a rare gas) other than the purge gas, and information based on the measurement information. The method of correcting the imaging characteristics has been described. In this regard, as described above, the wafer stage chamber 60 ゃ the reticle stage chamber 40 also has an example. For example, when gas is being replaced with helium as a purge gas and other low-absorbing gas is mixed, the refractive index of the optical path of the laser interferometers 63 and 43 fluctuates, and the interferometer Adversely affect measured values. Therefore, similarly to the above embodiment, the residual concentration of the low-absorbent gas other than the purge gas in the return gas from the exhaust pipes 15B and 13B was measured, and the measured value of the interferometer was determined based on the measured value. Is desirably corrected. Thereby, control accuracy of wafer stage 61 and reticle stage 41 can be improved.

'' Next, in a projection exposure apparatus, it is necessary to perform exposure by superimposing circuit patterns on multiple layers on a semiconductor wafer, so that the wafer W and the pattern image of the reticle R must be accurately superimposed. is there. Therefore, an alignment sensor for detecting alignment marks formed on the wafer W and the reticle R for alignment is required. Therefore, in FIG. 1, a reticle alignment microscope 86 for detecting an alignment mark (reticle mark) of reticle R is disposed above reticle stage 41, and wafer W is also provided on the lower side surface of projection optical system PL. An alignment sensor (not shown) for detecting the above alignment mark is provided. These alignment sensors are also mounted on a conventional exposure apparatus and are not unique to this example. However, when the exposure light source is in the vacuum ultraviolet region as in the projection exposure apparatus of this example, For the alignment sensor, a configuration corresponding to that is also adopted. Hereinafter, the configuration of a reticle alignment microscope (hereinafter, referred to as an “RA microscope”) 86 as the mark detection system of the present example will be described with reference to FIG.

FIG. 3 is an enlarged view of a main part showing the configuration of the RA microscope 86 of the present example. In FIG. 3, the reticle stage 41 accommodates the reticle stage chamber 40 containing the reticle stage system. The RA microscope 86 is arranged above the. As described above, since the RA microscope 86 uses light in the same wavelength range as the exposure light IL as the alignment ¾, in FIG. 1, the illumination for the alignment branched from the optical path of the exposure light IL in the beam matching unit 2 The light IL 1 is guided to an RA microscope 86 via an alignment light transmission system 8 arranged in a long and narrow airtight chamber 80.

In addition, as the elongated airtight chamber 80, a hollow pipe in which a metal film such as aluminum is coated on the inner surface as a reflective film may be used. The material of this pipe is glass The metal film (reflection film) on the inner surface can be formed by a method such as MOC VD (organic metal CVD). And for the optical path of such a hollow pipe, F

2 In order to transmit the laser light, replacement with a purge gas is necessary. For example, one end of the hollow pipe (for example, the RA microscope 86 side) is connected to the other end (the beam matching unit 2 side) from the other end. As the pressure, the gas can be caused to flow by this pressure difference, and the inside can be replaced with a purge gas.

In FIG. 3, the illumination light IL 1 guided to the RA microscope 86 in the reticle stage room 40 passes through a mirror 87, a relay lens 88, and reaches a beam splitter 89 for branching. The illumination light IL1 reflected by the illuminates the alignment mark (reticle mark) RM on the pattern surface (lower surface) of the reticle R via the objective lens 90 and the mirror 91 for epi-illumination. Then, the illumination light IL 1 transmitted around the reticle mark RM passes through the projection optical system PL and illuminates a reference mark (not shown) provided near the wafer W on the wafer stage 61 in FIG. I do. The light reflected from the reference mark is returned to the reticle R again via the projection optical system PL.

In FIG. 3, the illumination light IL 1 reflected by the reticle mark RM and the illumination light IL 1 reflected by the reference mark on the wafer stage side and returned to the reticle R side are the mirror 91 and the object lens 90. After passing through the beam splitter 89, the illumination light IL 1 transmitted through the beam splitter 89 passes through a field lens 92 to a two-dimensional image sensor 94 such as a CCD in the image pickup device 95 (photoelectric detection). An image of the reticle mark RM and an image of the reference mark on the wafer stage side are formed thereon. At this time, since the illumination light IL 1 is at the exposure wavelength, the image of the reference mark via the projection optical system PL and the image of the reticle mark RM are placed on the image sensor 94 without providing an optical system for correction. Is formed. A cover glass 93 is disposed on the incident surface side of the imaging device 94 of the imaging device 95. The electric signal from the image pickup device 94 is supplied to a drive circuit 96 installed outside the reticle stage chamber 40 (the gas inside the reticle stage 40 is replaced with a purge gas), where it is amplified and the image signal S is amplified. It becomes 3 and is supplied to the main control system 10 in FIG. In this case, an electric signal cable between the imaging element 94 and the driving circuit 96 is provided on a partition of the reticle stage chamber 40, for example, a current introducer for a vacuum device. It is connected via a type connector (MS connector). As a result, the electric signal of the imaging element 94 can be supplied to the drive circuit 96 while maintaining the airtightness in the reticle stage chamber 40.

The main control system 10 in FIG. 1 processes the image signal S3 to determine the amount of displacement in the X and Y directions between the reticle mark; M and the corresponding reference mark. Similarly, the amount of misalignment between another reticle mark on reticle R and the corresponding reference mark is detected, and the positional relationship of reticle R with respect to the coordinate system of wafer stage system 6 is determined based on these misalignments. Is calculated, and reticle alignment is performed by this.

The drive circuit 96 is installed outside the reticle stage chamber 40 as in this example because of the organic gas (degassing) released from various electric components included in the drive circuit 96. This is to prevent a decrease in the transmittance of the exposure light. Therefore, when components that minimize degassing are used for the drive circuit 96, the drive circuit 96 can also be arranged in the reticle stage chamber 40. In this case, wiring for transmitting the image signal S3 from the drive circuit 96 is connected via a current introducer type connector (MS connector).

Further, in this case, it is preferable to provide a means for forcibly exhausting gas near the drive circuit 96 as a measure against a small amount of degassing and heat radiation from the electric components in the drive circuit 96. This exhaust system can be realized, for example, by disposing an end of a pipe branched from the exhaust pipe 13B of the reticle stage chamber 40 near the drive circuit 96. As another method, an exhaust port 40 a communicating with the exhaust pipe 13 B in the partition wall of the reticle stage chamber 40 may be arranged near the drive circuit 96. In addition, even when the drive circuit 96 is installed outside the reticle stage room 40, there is a possibility of degassing from the imaging device 95 (the imaging device 94). The exhaust port 40a may be arranged near the imaging device 95.

Further, the RA microscope 86 of the present example is arranged in the reticle stage chamber 40, but the RA microscope 86 is arranged in an airtight chamber like the alignment light transmission system 8. You may. In other words, mirror 87, relay lens 88, beam splitter 89, objective lens 90, mirror for epi-illumination provided in RA microscope 86 91, the field lens 92 and the imaging device 95 may be arranged in an airtight room. The optical system (reticle alignment optical system) in the above-mentioned alignment light transmission system 8 and RA microscope 86 is an optical system that uses illumination light having the same wavelength as the exposure light IL in the vacuum ultraviolet region. All of the optical materials of the refraction member such as the lens that constitutes the above use a fluoride crystal such as fluorite that transmits vacuum ultraviolet light. In addition to fluorite, crystals such as lithium fluoride, magnesium fluoride, strontium fluoride, lithium monolithium) aluminum and fluoride, lithium, strontium and aluminum monofluoride, etc. Fluoride glass made of zirconium-barium mulanthanum aluminum, quartz glass doped with fluorine, quartz glass doped with hydrogen in addition to fluorine, quartz glass containing OH groups, and fluorine (4) Improved quartz such as quartz glass containing an H group may be used.

For a thin member such as a cover glass 93 for protecting the imaging surface of the imaging element 94, for example, fluorine-doped quartz in which the transmittance of vacuum ultraviolet light is improved by adding fluorine is used. It is also possible to use.

When the wavelength of the exposure light is close to 200 nm, fluorine-doped quartz can be used as an optical material of a refractive member such as a lens.

In the above embodiment, a part of the exposure light IL branched in the beam matching unit 2 is used as the alignment light, but a configuration is provided in which a dedicated light source for emitting the alignment light is separately provided. There may be.

Further, the magnification of the projection optical system PL in the above embodiment may be not only reduced (for example, 1/4, 1Z5, etc.) but also any of 1: 1 and enlargement. It is also possible to use X-rays as the exposure beam. In this case, a reflective optical system (a reticle of a reflective type should be used) may be used as the projection optical system.

Then, the illumination optical system and projection optical system composed of multiple lenses are incorporated into the exposure apparatus main body to perform optical adjustment, and a reticle stage and a wafer stage consisting of many mechanical parts are attached to the exposure apparatus main body to perform wiring and piping. Connect and adjust further

(Electrical adjustment, operation confirmation, etc.), the projection exposure apparatus of the present embodiment can be manufactured. In the manufacture of projection exposure equipment, temperature and cleanliness are controlled. It is desirable to perform in a clean room.

Next, an example of a semiconductor device manufacturing process using the projection exposure apparatus of the above embodiment will be described with reference to FIG.

FIG. 4 shows an example of a semiconductor device manufacturing process. In FIG. 4, first, a wafer W is manufactured from a silicon semiconductor or the like. Thereafter, a photoresist is applied on the wafer W (step S10), and the wafer W is loaded on the wafer stage of the projection exposure apparatus of FIG. In the next step S12, reticle R1 is picked up on the reticle stage shown in FIG. 1 and this reticle R1 is moved below the illumination area, so that the entire pattern of reticle R1 on wafer W is transferred. Scan exposure is performed on the shot area SE of the first row. The wafer W is, for example, a wafer having a diameter of 300 mm (12-inch wafer). The size of the shot area SE is, for example, 25 mm in the non-scanning direction and 33 mm in the scanning direction. This is a rectangular area. Next, in step S14, a predetermined pattern is formed in each shot region SE of the wafer W by performing development, etching, ion implantation, and the like. Next, in step S16, a photoresist is applied on the wafer W, and then in step S18, another reticle R2 is loaded on the reticle stage shown in FIG. Moving downward, the pattern of the reticle R2 is scanned and exposed on each shot area SE on the wafer W. Then, in step S20, a predetermined pattern is formed in each shot area of the wafer W by performing development, etching, ion implantation, and the like of the wafer W. The above-described exposure step to pattern formation step (step S16 to step S20) are repeated as many times as necessary to manufacture a desired semiconductor device. And the wafer

Through the dicing process (step S22), which separates each chip CP on the W one by one, the bonding process and the packaging process (step S24), the semiconductor device .SP as a product is Manufactured.

The application of the exposure apparatus of the present invention is not limited to an exposure apparatus for manufacturing a semiconductor device. For example, a liquid crystal display element formed on a square glass plate, or a display apparatus such as a plasma display. The present invention can be widely applied to an exposure apparatus and an exposure apparatus for manufacturing various devices such as an imaging device (such as a CCD), a micro machine, a thin film magnetic head, and a DNA chip. Furthermore, the present invention The present invention can also be applied to an exposure step (exposure apparatus) when manufacturing a mask (a photomask, a reticle, etc.) on which a device mask pattern is formed using a photolithographic process.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention. In addition, all disclosures in Japanese Patent Application No. 2000-3802 7708, filed on February 15, 2000, including the specification, claims, drawings, and abstract Is incorporated herein by reference as it is. Industrial applicability

In the present invention, when the refraction member of the mark detection system is formed of an optical material that transmits the exposure beam, when the alignment light having a wavelength range similar to the short wavelength exposure light such as a vacuum ultraviolet region is used. It is possible to realize an alignment system suitable for.

When an intake port is provided in the vicinity of the photoelectric detector, a purge gas is supplied on the optical path using alignment light having a wavelength range similar to a short wavelength exposure beam such as a vacuum ultraviolet region. In that case, an alignment system for the mask or substrate can be installed without adversely affecting the optical path.

Further, in the present invention, when the first gas (purge gas) is supplied to the optical path of the exposure beam and the imaging characteristic is adjusted according to the residual concentration of the second gas in the optical path, the first gas (purge gas) may be placed on the optical path of the exposure beam. Even if a gas other than the purge gas remains in the chamber, or the residual concentration of the gas other than the purge gas fluctuates, stable imaging characteristics can always be obtained. Therefore, it is possible to greatly relax the specification of the amount of the other gas mixed with the purge gas, and it is possible to realize a stable exposure apparatus.

Further, in the present invention, when the residual concentration of the second gas that transmits the exposure beam other than the first gas (purge gas) in the optical path of the exposure beam exceeds an allowable level, the gas in the optical path is replaced with the purge gas. Even in the case of re-substitution, desired imaging characteristics can be obtained. According to these inventions, an exposure apparatus is used in comparison with a method in which a low-absorbing gas such as nitrogen or argon is liquefied and removed using a cooling device that is expensive, consumes large power, and is a vibration source. Necessary surface of a clean room that can be miniaturized and houses the exposure equipment And the manufacturing cost and operating cost of the exposure apparatus can be reduced.

Claims

The scope of the claims

1. An exposure apparatus that exposes a second object through a first object with an exposure beam having a wavelength of 200 nm or less,

An alignment optical system that collects alignment light having substantially the same wavelength as the exposure beam, having passed through a mark on the first object or the second object;

A mark detection system having a photoelectric detector for detecting the alignment light collected by the alignment optical system,

An exposure apparatus, wherein the refraction members in the alignment optical system are all formed of an optical material that transmits the exposure beam.

2. The exposure apparatus according to claim 1, wherein the optical material transmitting the exposure beam is fluorite or quartz doped with fluorine.

3. The gas on at least a part of the optical path of the alignment light and the gas inside the partition wall in which the photoelectric detector is housed are replaced with a gas that transmits the exposure beam. 3. The exposure apparatus according to range 1 or 2.

4. The exposure apparatus according to claim 3, wherein a suction port for sucking gas inside the partition is provided in a region of the partition close to the photoelectric detector.

5. The method according to any one of claims 1 to 4, wherein a part of the alignment optical system includes a hollow member provided with a reflection member for reflecting the alignment light on an inner wall thereof. Exposure equipment.

6. The alignment optical system further includes: a light transmission optical system that irradiates alignment light having substantially the same wavelength as the exposure beam to a mark on the first object or the second object. 5. The exposure apparatus according to claim 1, further comprising a hollow member provided with a reflection member for reflecting the alignment light on an inner wall thereof.

7. An exposure method for exposing a second object with an exposure beam via a first object and a projection optical system,

A gas in at least a part of the optical path of the exposure beam is replaced with a first gas that transmits the exposure beam, and the gas remaining in the at least a part of the optical path is replaced. Measure the concentration of the second gas different from the one gas,

An exposure method, comprising: adjusting an imaging characteristic of the projection optical system according to a residual concentration of the second gas.

8. The exposure according to claim 7, wherein when the residual concentration of the second gas exceeds a predetermined level, the gas in the at least part of the optical path is replaced with the first gas. Method.

9. The exposure method according to claim 7, wherein the second gas is a gas that transmits the exposure beam.

10. The exposure beam is ultraviolet light having a wavelength of 200 nm or less,

The first gas is nitrogen;

9. The exposure method according to claim 7, wherein the second gas is at least one gas selected from the group consisting of oxygen, carbon dioxide, water vapor, neon, and helium.

1 1. The exposure beam is ultraviolet light with a wavelength of 20 O 'nm or less,

The first gas is helium;

9. The method according to claim 7, wherein the second gas is at least one gas selected from the group consisting of oxygen, nitrogen, carbon dioxide, water vapor, neon, argon, and krypton. Exposure method.

1 2. An exposure method for exposing a second object through a first object and a projection optical system with an exposure beam,

Replacing the gas in at least a part of the optical path of the exposure beam with a first gas that transmits the exposure beam;

Measuring the concentration of a second gas that remains in the at least a part of the optical path and transmits the exposure beam, and is different from the first gas;

An exposure method, wherein when the residual concentration of the second gas exceeds a predetermined level, the gas in at least a part of the optical path is replaced with the first gas.

1 3. The first gas is nitrogen,

13. The exposure method according to claim 12, wherein the second gas is at least one of neon and helium.

1 4. The first gas is helium,

The exposure method according to claim 12, wherein the second gas is at least one gas selected from a gas group consisting of nitrogen, neon, argon, and krypton.

15. An exposure apparatus that exposes a first object and a second object via a projection optical system with an exposure beam,

An imaging characteristic adjustment device for adjusting the imaging characteristic of the projection optical system,

A gas supply mechanism that replaces a gas in at least a part of an optical path of the exposure beam to the second object with a first gas that transmits the exposure beam;

A gas sensor for measuring a concentration of a second gas different from the first gas remaining in the at least a part of the optical path;

An exposure apparatus comprising: a control system that adjusts an imaging characteristic of the projection optical system via the imaging characteristic adjustment device based on a measurement value of the gas sensor.

16. An exposure apparatus that exposes a first object and a second object via a projection optical system with an exposure beam,

A gas sensor that remains in at least a part of the optical path and transmits the exposure beam, and measures a concentration of a second gas different from the first gas;

An exposure apparatus, comprising: a control mechanism that controls the gas supply mechanism, and that replaces the gas in the at least a part of the optical path with the first gas based on a measurement value of the gas sensor.

17. A device manufacturing method comprising a step of transferring a device pattern onto a workpiece using the exposure method according to any one of claims 7 to 14.