JP2006024849A - Exposure apparatus and manufacturing method of device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure apparatus for enhancing the spatial isolation of adjacent spaces while suppressing increase in the partial pressure of helium. <P>SOLUTION: The exposure apparatus introducing light from a light source onto a body to be exposed via first and second spaces includes a gas supply port for supplying a prescribed gas into an intake between the first and second spaces, and there is a minimum cross-sectional area in the intake, which is smaller than the end of the intake at the first space side and the end of the intake at the second space side, and relations of Lmin-Lall/10<Lin<Lmin+Lall/10 are satisfied. In the inequality, Lall is a distance from the end of the intake at the first space side to the end of the intake at the second space side, Lmin is a distance from the end at the first space side to the minimum cross-sectional area part, and Lin is a distance from the end at the first space side to the center of the gas supply port. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exposure apparatus for transferring a fine circuit pattern, in particular, a configuration in which exposure light passes through a vacuum, such as an extreme ultraviolet (exposure apparatus using light having a wavelength of 13 to 15 nm, an X-ray exposure apparatus, etc. The present invention relates to an exposure apparatus having

  Conventionally, reduction projection exposure using ultraviolet rays has been performed as a printing (lithography) method for manufacturing fine semiconductor elements such as semiconductor memories and logic circuits.

  The minimum dimension that can be transferred by reduction projection exposure is proportional to the wavelength of light used for transfer and inversely proportional to the numerical aperture of the projection optical system. For this reason, in order to transfer a fine circuit pattern, the wavelength of exposure light has been shortened, and ultraviolet light used as a mercury lamp i-line (wavelength 365 nm), KrF excimer laser (wavelength 248 nm), and ArF excimer laser (wavelength 193 nm). The wavelength of is getting shorter.

  However, semiconductor elements are rapidly miniaturized, and there is a limit in lithography using ultraviolet light. Therefore, a reduction projection exposure apparatus using extreme ultraviolet light (EUV light) having a wavelength of about 10 to 15 nm, which is shorter than ultraviolet light, has been developed in order to efficiently burn a very fine circuit pattern of less than 0.1 μm. Has been.

  In the EUV light region, absorption by a substance becomes very large. Therefore, a lens optical system using light refraction as used in visible light or ultraviolet light is not practical, and a reflective optical system is used. As for the reticle, a reflective reticle in which a pattern to be transferred by an absorber is formed on a mirror is used.

  As a reflection type optical element that constitutes an exposure apparatus using EUV light, there are a multilayer mirror and a grazing incidence total reflection mirror. Since the real part of the refractive index is slightly smaller than 1 in the EUV region, total reflection occurs when used at an oblique incidence where EUV light is incident on the surface. Usually, a high reflectivity of several tens of percent or more can be obtained at an oblique incidence within several degrees as measured from the surface. However, the degree of freedom in optical design is small, and it is difficult to use a total reflection mirror for a projection optical system.

  As a mirror for EUV light used at an incident angle close to normal incidence, a multilayer mirror in which two kinds of substances having different optical constants are alternately stacked is used. Molybdenum and silicon are alternately laminated on the surface of a glass substrate polished to a precise surface shape. The thickness of the layer is, for example, about 0.2 nm for the molybdenum layer, about 0.5 nm for the silicon layer, and about 20 layers. The sum of the thicknesses of two kinds of substances is called a film cycle. In the above example, the film period is 0.2 nm + 0.5 nm = 0.7 nm.

  When EUV light is incident on such a multilayer mirror, EUV light having a specific wavelength is reflected.

When the incident angle is θ, the wavelength of the EUV light is λ, and the film period is d, the Bragg equation is approximately 2 × d × sin θ = λ
Only EUV light with a narrow bandwidth centered at λ that satisfies the above relationship is efficiently reflected. The bandwidth at this time is about 0.6 to 1 nm.

  The reflectivity of the reflected EUV light is about 0.7 at the maximum, and the EUV light that is not reflected is absorbed in the multilayer film or the substrate, and most of the energy becomes heat.

  Multilayer mirrors have a greater light loss than visible light mirrors, so it is necessary to minimize the number of mirrors. In order to realize a wide exposure area with a small number of mirrors, only a thin arc-shaped area (ring field) separated by a certain distance from the optical axis is used to simultaneously scan the reticle and wafer to transfer a large area. A method (scan exposure) is performed.

  As shown in FIG. 10, a schematic projection exposure apparatus using EUV light includes an EUV light source, an illumination optical system, a reflective reticle, a projection optical system, a reticle stage, a wafer stage, an alignment optical system, and a vacuum. It consists of systems.

  For example, a laser plasma light source is used as the EUV light source. This irradiates the target material supplied by the target supply device placed outside the vacuum vessel with high-intensity pulsed laser light, generates high-temperature plasma, and uses EUV light with a wavelength of, for example, about 13 nm. Is. As the target material, a metal thin film, an inert gas, a droplet, or the like is used, and is supplied into the vacuum container by means such as a gas jet. In order to increase the average intensity of emitted EUV light, the repetition frequency of the pulse laser should be high, and it is usually operated at a repetition frequency of several kHz.

  The illumination optical system includes a plurality of multilayer films or oblique incidence mirrors, an optical integrator, and the like. The first stage collecting mirror serves to collect EUV light emitted from the laser plasma almost isotropically. The optical integrator has a role of uniformly illuminating the mask with a predetermined numerical aperture. In addition, an aperture for limiting an area illuminated by the reticle surface to an arc shape is provided at a position conjugate with the reticle of the illumination optical system.

  The projection optical system uses a plurality of mirrors. Although the use efficiency of EUV light is higher when the number of mirrors is smaller, aberration correction becomes difficult. The number of mirrors necessary for aberration correction is about 4 to 6. The shape of the reflecting surface of the mirror is a convex or concave spherical or aspherical surface. The numerical aperture NA is about 0.1 to 0.2.

  The mirror is made by grinding and polishing a substrate made of a material such as low expansion coefficient glass or silicon carbide, which has high rigidity and high hardness, and a low coefficient of thermal expansion. A multilayer film such as silicon is formed. When the incident angle is not constant depending on the location in the mirror plane, as is clear from the Bragg equation described above, the wavelength of EUV light whose reflectivity increases depending on the location in a multilayer film with a constant film period shifts. Therefore, it is necessary to provide a film period distribution so that EUV light having the same wavelength is efficiently reflected in the mirror plane.

  The reticle stage and wafer stage have a mechanism for scanning synchronously at a speed ratio proportional to the reduction magnification. Here, X is the scanning direction in the reticle or wafer surface, Y is the direction perpendicular thereto, and Z is the direction perpendicular to the reticle or wafer surface.

  The reticle is held by a reticle chuck on the reticle stage. The reticle stage has a mechanism that moves at high speed in the X direction. In addition, a fine movement mechanism is provided in the X direction, the Y direction, the Z direction, and the rotation direction around each axis so that the reticle can be positioned. The position and orientation of the reticle stage are measured by a laser interferometer, and the position and orientation are controlled based on the result.

  The wafer is held on the wafer stage by a wafer chuck. The wafer stage has a mechanism that moves at high speed in the X direction, like the reticle stage. In addition, a fine movement mechanism is provided in the X direction, the Y direction, the Z direction, and the rotation direction around each axis so that the wafer can be positioned. The position and orientation of the wafer stage are measured by a laser interferometer, and the position and orientation are controlled based on the result.

  The alignment detection mechanism measures the positional relationship between the reticle position and the optical axis of the projection optical system, and the positional relationship between the wafer position and the optical axis of the projection optical system, and the projected image of the reticle matches the predetermined position on the wafer. Thus, the position and angle of the reticle stage and wafer stage are set.

  Further, the focus position in the Z direction is measured on the wafer surface by the focus position detection mechanism, and by controlling the position and angle of the wafer stage, the wafer surface is always kept at the image formation position by the projection optical system during exposure.

  When one scan exposure is completed on the wafer, the wafer stage is stepped in the X and Y directions and moved to the next show scanning exposure start position, and the reticle stage and wafer stage are again proportional to the reduction magnification of the projection optical system. The synchronous scanning is performed in the X direction at the speed ratio.

  In this manner, the operation of synchronously scanning the reduced projection image of the reticle while it is formed on the wafer is repeated (step-and-scan). Thus, the reticle transfer pattern is transferred onto the entire wafer surface.

EUV light is strongly absorbed by the gas. For example, when EUV light having a wavelength of 13 nm propagates 1 m in a space filled with 10 Pa of air, the transmittance of the EUV light is about 50%. Similarly, when EUV light propagates 1 m through a space filled with the following gas at 10 Pa, the transmittance is about 88% for helium, which is a relatively high transmittance, about 71% for argon, and about 98% for hydrogen. is there. In order to avoid absorption by gas, a gas such as helium having a high transmittance is substituted, and a pressure and oxygen of at least 10 ⁻¹ Pa or less, preferably 10 ⁻³ Pa or less, in most spaces where EUV light propagates, It is necessary to keep the partial pressure of a gas having a low permeability such as water as low as possible.

Further, when molecules containing carbon such as hydrocarbons remain in the space where the optical element irradiated with EUV light is placed, carbon gradually adheres to the surface of the optical element due to light irradiation, and this absorbs EUV light. However, there is a problem that the reflectance decreases. In order to prevent this carbon adhesion, the partial pressure of the molecule containing carbon in the space where the optical element irradiated with EUV light is placed is kept at a pressure of at least 10 ⁻⁴ Pa or less, preferably 10 ⁻⁶ Pa or less. It is considered necessary to be.

  However, the exposure apparatus repeats the act of carrying in a semiconductor wafer coated with a resist, which is a photosensitive agent, from outside the exposure apparatus, transferring information on the reticle, and carrying it out. Since the wafer stage has a driving mechanism such as a moving mechanism for performing scanning exposure and a mechanism for transporting the wafer, the surface area is very large. For this reason, outgas from these parts does not easily disappear, and it is difficult to achieve a high vacuum. Furthermore, the resist applied to the wafer is an organic substance even though it is heated and baked before exposure, and when it is brought into vacuum, the organic compound constituting it from the resist and the carbon compound that is the decomposed substance thereof And the like will occur and diffuse into the vacuumed device. In addition, the wafer is carried into the exposure apparatus from the atmosphere, but it is difficult to eliminate the air component including moisture adhering to the wafer within a short time due to the carry-in of the wafer. Desorb and diffuse. Due to the outgas from these wafers and resists, it is very difficult to maintain the high vacuum state as described above.

  In that case, it is possible to increase the vacuum state using a large-capacity exhaust pump or the like, but the problem is that component, and as described above, molecules containing carbon and moisture are especially in the exposure apparatus such as mirrors and Spreading into the space where the reticle is installed must be avoided.

In Patent Document 1, in a place where exposure light is condensed, such as on a wafer surface, a conical opening (a wafer surface having no constriction or an opening having an opening cross-sectional area that decreases toward a reticle surface) is disclosed. There has been proposed a technique for suppressing outgas from the wafer surface and from the wafer stage space by supplying helium to eject helium molecules onto the wafer surface.
JP 2000-58443 A

  However, in the configuration of Patent Document 1, since the opening area becomes the smallest in the vicinity of the wafer surface, most of the helium supplied inside the opening is ejected to the projection optical system, and the pressure inside the projection optical system increases. As a result, the transmittance of the EUV light is reduced, causing a decrease in throughput.

In order to solve this problem, an exposure apparatus according to one aspect of the present invention is an exposure apparatus that guides and exposes light from a light source onto an object to be exposed through a first space and a second space. And a gas supply port for supplying a predetermined gas into a vent between the first space and the second space. Here, in the vent, the vent on the first space side of the vent is provided. There is a minimum cross-sectional area portion having a cross-sectional area smaller than a cross-sectional area of the end portion and smaller than a cross-sectional area of the end portion of the vent on the second space side, and an end of the vent port on the first space side The distance from the first space side end to the second space side end of the vent is Lall, the distance from the first space side end to the minimum cross-sectional area is Lmin, and the first space side end. When the distance from the center of the gas supply port to Lin,
Lmin−Lall / 10 <Lin <Lmin + Lall / 10
It is characterized by satisfying. Here, it is desirable that the gas supply port is provided in the minimum cross-sectional area.

  Moreover, it is desirable to provide a cooling mechanism for cooling the vent hole, and it is desirable to further include a radiation shield so as to surround the vent hole and the cooling mechanism. Here, it is preferable that at least one optical element that guides light from the light source to the object to be exposed is provided, and the radiation shield is disposed between the cooling mechanism and the at least one optical element.

  Moreover, it is desirable to provide a temperature adjustment mechanism for adjusting the temperature of the radiation shield. Moreover, it is desirable that the temperature of the cooling member included in the cooling mechanism is 40K or more and 200K or less.

  The predetermined gas is preferably argon, helium, hydrogen, or a mixed gas thereof. Furthermore, it is desirable to control the pressure in the vent to about 0.1 to 10 Pa.

  Moreover, it is desirable to have a means for measuring the pressure in the first space and / or the second space, and adjust the amount of gas supplied from the gas supply port based on the measurement result.

  It is desirable that light from the light source to the object to be exposed passes through the vent hole.

  The vent is preferably disposed between the light source and an illumination optical system that guides light from the light source to a reticle.

  The vent is preferably disposed in a projection optical system that guides light from a reticle illuminated with light from the light source to the object to be exposed.

  In addition, the vent may be provided between a projection optical system that guides light from a reticle illuminated with light from the light source to the object to be exposed and a space surrounding a reticle stage on which the reticle is placed, and / or the projection. Desirably, the optical system is disposed between a space surrounding the wafer stage on which the object to be exposed is placed. Moreover, it is desirable to have a flow path for exhausting the gas in the vent.

  Preferably, each of the separated spaces has a means for measuring pressure, and the pressure in the vent is controlled based on the measurement result of the means for measuring pressure. In addition, it is desirable to have means for measuring the flow rate of the gas supplied into the opening, and to control the pressure in the opening based on the measurement result of the means for measuring the flow rate.

  A device manufacturing method according to one aspect of the present invention includes a step of exposing the object to be exposed using the exposure apparatus according to any one of the above, and a step of developing the exposed object to be exposed. It is characterized by having.

  According to the exposure apparatus of the present invention, the atmospheres constituting different spaces can be substantially separated, and the amount of carbon compound adhering to the mirror can be reduced.

The exposure apparatus of the present embodiment is an exposure apparatus that guides light from a light source onto an object to be exposed through a first space and a second space, and exposes the first space and the second space. A gas supply port for supplying a predetermined gas in the air vent between them, and the inside of the vent is smaller than the cross-sectional area of the end portion on the first space side of the vent and the vent of the vent There is a minimum cross-sectional area portion having a cross-sectional area smaller than a cross-sectional area of the end portion on the second space side, from the end portion on the first space side of the vent hole to the end portion on the second space side of the vent hole The distance from the end of the first space to the minimum cross-sectional area is Lmin, and the distance from the end of the first space to the center of the gas supply port is Lin. When
Lmin−Lall / 10 <Lin <Lmin + Lall / 10
It is characterized by satisfying. Further, the second space is any one of a space including a light source, a space including a reticle stage, and a space including a wafer stage, and the gas supply port is closer to the second space than the minimum area portion. It is characterized by being arranged in.

  Briefly described with reference to FIG. 2, the distance from the space A (first space) side end of the air vent connecting space A and space B to the space B (second space) side end. Corresponds to the length shown in FIG. 2, that is, the length (depth) of the vent in the Y direction. Lmin is a distance between the portion where the cross-sectional area of the ventilation port is minimized (minimum cross-sectional area) and the end on the space A side is represented by Lmin, and a supply port for supplying an inert gas (preferably helium) The distance from the (inlet) to the end on the space A side is represented by Lin. In FIG. 2, Lin≈Lmin, and a gas supply port is provided in the minimum cross-sectional area. This form is most preferable, but the gas supply port may be provided at a position slightly shifted from the minimum cross-sectional area (may be shifted to about All / 10). In addition, when the space B (second space) is a space that causes contamination, the gas supply port is provided at the position of the minimum cross-sectional area or closer to the space B than the minimum cross-sectional area. Is preferred.

  In addition, the description in the examples describes only a configuration in which Lin is substantially half of Lall, but of course not limited thereto. Preferably, Lin is greater than Lall / 10 and less than 9 Lall / 10. Further, as shown in FIG. 6, when Lmin is not limited to one place but is within a certain range (when Lmin is not a predetermined value but a predetermined range), Lmin may be an arbitrary value within the range. .

  The following embodiments will be described in detail with reference to the drawings.

  FIG. 1 shows an overall view of an EUV exposure apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, 1 is a pulse laser for excitation, 2 is a condensing lens, 3 is a target gas supply device, 4 is plasma, 5 is EUV light (extreme ultraviolet light, that is, light having a wavelength of 13 to 14 nm), and 6 is a light source mirror. , 71 is a space separation purge unit (here, purge is to fill a certain space with a predetermined gas, and the space separation purge unit referred to here substantially separates two spaces, ie, two spaces. The unit is a unit for allowing the gas to flow back and forth between the two spaces separately, and the two spaces can be purged separately), 7 is an illumination system first mirror, 8 is an illumination system second Mirror, 72 is a space separation purge unit that also serves as an angle-of-view restriction aperture, 10 is an illumination system third mirror, 73 is a space separation purge unit, and 11 is a reflective reticle (transfer pattern portion, ie, transfer pattern portion). The reflectance (50% or more, preferably 60% or more) with respect to the light irradiated to the desired portion is a reflectance (10% or less, preferably 1) with respect to the light irradiated to the non-transfer pattern portion, that is, the portion that is not to be transferred. % May be referred to as a reflective mask or a reflective original), 12 is a reticle holding device, 13 is a reticle stage, 14 is a reticle alignment optical system, 15 is a projection system first mirror, 16 Is a projection system second mirror, 17 is a projection system third mirror, 18 is an aperture limiting aperture, 19 is a projection system fourth mirror, 20 is projection EUV light, 74 is a space separation purge unit, and 21 is a wafer (object to be exposed). , 22 represents a wafer chuck, 23 represents a wafer stage, and 24 represents a wafer alignment optical system. Here, the illumination system has three mirrors and the projection system has four mirrors. However, the present embodiment is not limited to this. The number of illumination system mirrors, the number of projection system mirrors, and the like. Any number of sheets may be used.

  A laser plasma light source is used as the EUV light source. For example, the target material supplied by the target supply device 3 placed outside the vacuum vessel is irradiated with high-intensity pulsed laser light generated from the excitation pulse laser 1 to generate high-temperature plasma, which is emitted from this, for example. EUV light having a wavelength of about 13 nm (13 to 14 nm) is used. As the target material, a metal thin film, an inert gas, a droplet, or the like is used, and is supplied into the vacuum container by means such as a gas jet. In order to increase the average intensity of emitted EUV light, the repetition frequency of the pulse laser should be high, and it is usually operated at a repetition frequency of several kHz.

  The illumination optical system includes a plurality of multilayer films or oblique incidence mirrors, an optical integrator, and the like. The first-stage light source mirror 6 provided in the in-light source device collects EUV light emitted from the laser plasma almost isotropically. The illumination system first mirror 7 is an optical integrator and has a role of illuminating the mask with a predetermined numerical aperture substantially uniformly. The space separation purge unit 72 functions as an aperture for limiting the area illuminated by the reticle surface to an arc shape at a position conjugate with the reticle of the illumination optical system.

  The projection optical system uses a plurality of mirrors. Although the use efficiency of EUV light is higher when the number of mirrors is smaller, aberration correction becomes difficult. The number of mirrors necessary for aberration correction is at least two, preferably about 4 to 8 (preferably 6). The shape of the reflecting surface of the mirror is a convex or concave spherical or aspherical surface (preferably all aspherical surfaces). The numerical aperture NA is about 0.1 to 0.2 (preferably 0.15 or more).

  The mirror is made by grinding and polishing a substrate made of a material such as low expansion coefficient glass or silicon carbide, which has high rigidity and high hardness, and a low coefficient of thermal expansion. A multilayer film such as silicon is formed.

  The reticle stage 13 and the wafer stage 23 have a mechanism for scanning in synchronization with a speed ratio proportional to the reduction magnification. Here, the scanning direction in the reticle or wafer surface is defined as the X direction (axis), the direction perpendicular to the reticle or wafer surface is defined as the Z direction (axis), and the direction perpendicular to the X and Z directions (axis) is defined as the Y direction.

  The reticle 11 is held by the reticle chuck 12 on the reticle stage 13. The reticle stage 13 has a mechanism that moves at high speed in the X direction. Furthermore, it has a translation mechanism in each of the X direction, the Y direction, and the Z direction, and a fine movement mechanism in the rotational direction around each axis so that the position (and posture) of the reticle 11 can be determined with respect to the six axes. It has become. The position and orientation of the reticle stage 13 are measured by a laser interferometer (not shown), and the position and orientation of the reticle stage (reticle) are controlled based on the result.

  The wafer 21 is held on the wafer stage 23 by the wafer chuck 22. The wafer stage 23 has a mechanism that moves at high speed in the X direction, like the reticle stage 13. Furthermore, it has a translational movement mechanism in each of the X direction, the Y direction, and the Z direction, and a fine movement mechanism in the rotation direction around each axis, and the wafer 21 can be positioned with respect to the six axes. The position and orientation of the wafer stage 23 are measured by a laser interferometer (not shown), and the position and orientation of the wafer stage (wafer) are controlled based on the result.

The alignment detection mechanism 14 measures the positional relationship between the position of the reticle and the optical axis of the projection optical system, and the positional relationship between the position of the wafer and the optical axis of the projection optical system, and the projected image of the reticle is placed at a predetermined position on the wafer. Positions and angles of the reticle stage 13 and the wafer stage 23 so that they coincide (the position of the projected image of the reticle formed by the projection optical system is within the depth of focus within the exposure area). Is set. In the case of a step-and-repeat type exposure apparatus (so-called stepper), the inside of the exposure area here means one shot area, and in the case of a step-and-scan type exposure apparatus (so-called scanner), This is a light irradiation region, that is, a slit-shaped light irradiation region whose length in the scanning direction on the wafer is shorter than the width in the direction perpendicular to the scanning direction. )
Further, the focus position in the Z direction is measured on the wafer surface by the focus position detection mechanism 24, and the position and angle of the wafer stage are controlled, so that the wafer surface is always kept at the image formation position by the projection optical system during exposure.

  When one scan exposure is completed on the wafer 21, the wafer stage 23 is stepped in the X and Y directions and moved to the next show scanning exposure start position, and the reticle stage 13 and the wafer stage 23 are again connected to the projection optical system. Synchronous scanning is performed in the X direction at a speed ratio proportional to the reduction magnification.

  In this manner, the operation of synchronously scanning the reduced projection image of the reticle while it is formed on the wafer is repeated (step-and-scan). Thus, the reticle transfer pattern is transferred onto the entire wafer surface.

  As described above, a laser plasma light source is used as the EUV light source. In order to maintain a certain density of the target material, irradiate high-intensity pulsed laser light, and generate high-temperature plasma, metal thin film, inert gas, droplets and other molecules that become the target material diffuse, It adheres to the mirror constituting the exposure apparatus and causes a decrease in the reflectivity of the mirror. In addition, due to the outgas from the drive mechanism / constituent member such as the wafer stage and the reticleage, the exposure light intensity is lowered and the reflectance is lowered due to the adhesion of the carbon compound to the mirror. Also, from the resist applied to the wafer, an organic material of the resist material and a carbon compound that is a decomposed material are generated and diffused in a vacuum apparatus, and the organic material and the carbon compound are in the optical path. Since EUV light is absorbed or attached to the mirror to reduce the reflectance of the mirror, the exposure light intensity is reduced.

  In this embodiment, the optical path space surrounding the optical path of the exposure light from the light source to the wafer is separated into five spaces (if there is a plurality). In the present embodiment, a light source space 91, a reticle stage space 94, a wafer stage space 95, and an illumination optical system space 92 (mainly optical elements that mainly guide light from the light source to the reticle) are spaces in which generation sources such as outgas exist. Projection optical system space 93 (including mainly optical elements that guide light from the reticle to the wafer), partition walls 81, 82, 83, 84, 85, and space separation purge unit 71, 72, 73, 74 are used to substantially separate (substantially block the passage of gas between the two spaces), thereby reducing the amount of outgas entering the illumination optical system space and the projection optical system space. By reducing (preferably eliminating), the adverse effect of outgassing on the illumination optical system and projection optical system is reduced (preferably eliminated). Of course, each of the illumination optical system space 92 and the projection optical system space 93 may be separated into a plurality of spaces. In particular, the projection optical system space 93 is preferably provided with a space separation purge unit at or near the position where the reticle pattern forms an intermediate image. Specifically, when the projection optical system has a six-surface mirror, and the reticle pattern is intermediately imaged between the fourth and fifth mirrors from the reticle side on the optical path, the beam diameter Therefore, a space separation purge unit is arranged at that position, and the projection optical system space is separated into a space including the first, second, third, and fourth mirrors and a space including the fifth and sixth mirrors. Such a configuration is preferable. Of course, the arrangement position of the space separation purge unit is preferably a place where the beam diameter can be reduced like the intermediate imaging position, so that the intermediate imaging position is between the third and fourth mirrors. May be arranged at that position, or in the vicinity of two mirrors that are back-to-back (the surface opposite to the reflecting surface of the mirror is opposite) (specifically, 2 in the vertical direction). A space separation purge unit may be arranged between the two mirrors and in the vicinity of the two mirrors in the horizontal direction). In other words, among the plurality of mirrors included in the projection optical system, the mirror closest to the space separation purge unit used for separating the projection optical system space and the mirror closest to the second are back-to-back as described above. What is necessary is just to comprise so that it may be two mirrors.

  Here, it is preferable that the light source space 91, the reticle stage space 94, and the wafer stage space 95 containing the outgas generation source have no configuration except for the light source mirror. In particular, it is desirable not to arrange optical elements such as lenses and mirrors in the reticle stage space and wafer stage space.

  Here, exhaust devices 51, 52, 53, 54, 55 including a turbo molecular pump are connected to each of the above-described spaces. In particular, in the light source space 91, reticle stage space 94, and wafer stage space 95 where a generation source such as outgas exists, it is desirable that an exhaust device including a turbo molecular pump is disposed.

  Further, pressure sensors S1, S2, S3, S4, and S5 are provided to measure the pressure in each space. S1 is a light source space 91, S2 is an illumination optical system space 92, S3 is a projection optical system space 93, S4 is a reticle stage space 94, and S5 is a pressure of a wafer stage space 95.

  Valves 61, 62, 63, 64 capable of adjusting the flow rate are connected to the space separation purge unit, and high-purity helium is supplied, and the flow rate is measured by flow meters F1, F2, F3, F4.

  2 and 3 show details of the space separation purge units 71 to 74 shown in FIG. FIG. 2 is a diagram in which a space separation purge unit is provided at a condensing location, and FIG. 3 is a diagram in which a space separation purge unit is provided in a transmission location. The direction in which the exposure light passes is the Y direction, an opening exists on a plane parallel to the XZ plane as shown in the figure, and the exposure light passes through a partition that separates the space A and the space B in a direction parallel to the Y axis. The opening for penetrating. This aperture is provided so that the exposure light is not obstructed in the portion where the exposure light is collected and passed, and the aperture cross-sectional area is the smallest in the middle part from the end of the aperture to the smallest. This part is called a constriction. The position of the constriction is not necessarily near the center, and it is preferable to optimize the position of the constriction between the opening end and the opening end for convenience of design.

  A helium inflow port is provided at a position where the opening area becomes the smallest, helium is supplied from the inflow port, and exhaust units (not shown) are individually provided in the space A and the space B. The particle A constituting the space A is a particle containing molecules such as outgas generated in the space A, and the particle B constituting the space B enters the particle space A containing molecules such as outgas generated in the space B. Can be suppressed.

  With this configuration, helium is supplied to the constricted portion having the smallest opening cross-sectional area as compared with the case where helium is supplied into the cylindrical opening where the constriction does not exist. Therefore, the portion where the pressure is increased is limited to the vicinity of the constricted portion. In order to achieve this, the space where the pressure rises is minimized while the space is substantially separated (the state where there is substantially no gas flow between the two spaces) (the increase of the average pressure in the spaces A and B) Can be suppressed). The pressure difference of the supplied helium can be reduced by about two orders of magnitude in the A space and the B space compared to the constricted portion due to the partial pressure.

  Also, in places where exposure light is collected, such as on the reticle surface or wafer surface, a conical opening (a wafer surface without a constriction or an opening having an opening cross-sectional area that decreases toward the reticle surface, in other words, In the case where helium is supplied in the same manner when the constriction is present at the end of the opening), the opening area can be minimized in the vicinity of the wafer surface and the reticle surface. This is considered advantageous for suppressing the entrance of the atmosphere in the stage space into the projection optical system and illumination optical system. However, when a conical opening is used, the amount of helium leaking from the opening to the reticle surface side and the wafer surface side is reduced. Therefore, in order to obtain the effect of separating the space and suppressing the adverse effect of outgassing on the optical element, the amount of helium supplied in the opening must be increased, and the partial pressure in the opening of the supplied gas is increased. (Density) is increased, which causes a decrease in transmittance.

  The effect of using this method will be described with reference to FIGS. FIG. 4 is a view for explaining dimensions of parts having the same outer shape as the space separation purge unit 71 of FIG. The thickness of the opening is 400 mm, the diameter of the opening is φ48 mm at the opening end, and the diameter at the center of the opening is φ10 mm. A flow path for supplying helium is provided in this φ10 mm portion, and helium is supplied. Under such conditions, a simulation was performed using a DSMC (Direct Simulation Monte Carlo) method. The space A and the space B are each provided with an exhaust device equivalent to 0.46 m 3 / sec, and the space A is maintained at about 6 Pa with a carbon compound. In this case, the amount of carbon compound entering B space (partial pressure of carbon compound in space B / partial pressure of carbon compound in space A) and the amount of helium in the vicinity of the constriction in the opening with respect to the number of helium inflow molecules. FIG. 5 is a graph showing the partial pressure. The partial pressure of helium near the constriction gradually increases with the number of helium inflow particles. In addition, when the partial pressure of helium near the constriction is a comma number Pa or more, the pressure ratio of the carbon compound decreases, and the effect of suppressing the entry of the atmosphere from the space A to the space B due to the supply of helium in the constricted portion is confirmed. Can do. Thus, by setting the pressure of the constricted portion to 0.1 Pa or more, it is possible to obtain an effect for substantially separating by the partition wall and the space separation purge unit.

  On the contrary, if the pressure of the constricted portion is set to 10 Pa or more, the partial pressure of helium in the spaces A and B becomes 0.1 Pa or more, which causes a decrease in the transmittance. Therefore, the pressure of the constricted portion is about 0.1 to 10 Pa. It is preferable to set to.

  In addition, for the inflow amount of helium, the inflow amount may be controlled based on the result of measuring the inflow amount in each of the valves 61, 62, 63, 64 with the flow meters F1, F2, F3, F4. The inflow amount of helium may be controlled based on the pressure values of pressure gauges S1, S2, S3, S4, and S5 that measure the pressure in each space.

  In FIG. 1, a space separation unit 72 is provided in a part of the illumination optical system. This is provided in order to prevent outgas from the drive mechanism from propagating through the illumination optical system because the projection optical system includes a portion for driving a filter for controlling the mirror position and exposure amount. .

  Further, as shown in FIG. 6, a constriction for narrowing the opening is provided near the center from the opening end to the opening end of the cylindrical opening, and a flow path for supplying helium to the constricted portion is provided. A similar effect can be obtained by supplying helium. Further, in FIG. 6, a constriction is provided at one position with respect to the cylindrical opening, but the structure is such that the opening is expanded stepwise so that the opening area of the constriction near the center gradually approaches the opening area of the opening end. However, the same effect can be obtained.

  The gas supplied into the opening may be other than helium, or a gas having a high transmittance with respect to EUV light, such as hydrogen or argon.

  Another embodiment is shown in FIGS. FIG. 7 is a view showing a case where an exhaust port is provided at a position opposite to a helium inlet (flow path) for supplying helium in a constricted portion in the opening. By providing an exhaust port at a position opposite to the inflow port, if the helium supplied to the opening is difficult to diffuse into the spaces A and B, a helium wall can be formed in a constricted portion in the form of an air curtain. A, the entry of the particle A containing the outgas inside the space A into the space B and the entry of the particle B containing the outgas inside the space B into the space A are suppressed without increasing the partial pressure of helium in the space B. It is possible.

  Further, as shown in FIG. 8, a flow path may be provided at a position facing the constriction in order to supply helium. In addition, although two flow paths are provided in the figure, several inlets may be provided in the same opening. It may be a position having the same opening cross-sectional area (that is, the same position in the Y direction in FIG. 2), or helium inlets may be provided at two positions having different opening cross-sectional areas.

  Moreover, as shown in FIG. 11, it is possible to further suppress the ingress of outgas by cooling the member forming the constriction by a cryo refrigerator. Here, the cryocooler and the constriction member are connected by a cryopanel (cooling member), and the temperature of the constriction member is set between 40K and 200K so that the helium gas to be supplied is not adsorbed from the space A. Since the outgas entering the B can be adsorbed, the amount of the outgas entering the space B can be further reduced by about one digit. When using a cryocooler, it is preferable to surround the constricted member and the cooling part of the cryocooler with a heat insulating radiation shield in order to suppress cooling of the mirror and the chamber. Furthermore, the temperature of the mirror and the chamber can be kept constant by adjusting the temperature of the adiabatic radiation shield. Alternatively, the mirror temperature may be positively controlled using this cryorefrigerator.

  In the present invention, the gas supplied from the opening is limited to one type, but as shown in FIG. 9, valves 161 and 162 which are not in contact with the reticle stage space or wafer stage space in the space division purge unit are used. Two types of gas may be switched and supplied depending on the application (Here, if there is no problem even if ozone or other gas enters the reticle stage space or wafer stage space, the valves in all the space division units are used. The gas supplied may be switchable). Here, the space division purge units 71 and 72 are space division purge units used to divide the light source space and the illumination optical system space, and the illumination optical system space and the projection optical system space. The gas supplied from the valves 161 and 162 can be switched between helium as the purge gas and ozone as the cleaning gas.

  For example, helium with high transmittance is supplied at the time of exposure, and ozone gas used for mirror cleaning is supplied at other maintenance, etc., and switched to provide an air supply port for the mirror cleaning gas. May be used. Further, according to this configuration, it is possible to clean the mirror while suppressing mixing of the cleaning gas into the stage space while suppressing mixing of the outgas from the stage space into the illumination optical system and the projection optical system. Can do.

  In FIG. 8, the same kind of gas is supplied from individual flow paths, but different gases may be supplied to a plurality of flow paths.

  In the case of switching, it is preferable to reduce the inflow amount of helium after the inflow amount of the cleaning gas reaches a predetermined amount. If the amount of inflow supplied to the constriction is less than the predetermined amount of inflow, it becomes impossible to suppress the flow of gas between the spaces. For example, in the wafer stage space and the reticle stage space, This is because the intrusion amount of the atmosphere into the projection optical system and the illumination optical system is temporarily increased, and the adhesion of the carbon compound to the mirror is temporarily promoted.

  According to the above embodiment, the exposure apparatus of this embodiment suppresses adhesion (preferably minimizes) of the carbon compound to the mirror by substantially separating the atmosphere constituting the space. Is possible.

  Further, the mirror can be cleaned during maintenance by switching and supplying the cleaning gas by the space separation unit.

  Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described with reference to FIGS. FIG. 12 is a flowchart for explaining how to fabricate devices (ie, semiconductor chips such as IC and LSI, LCDs, CCDs, and the like). In the present embodiment, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), a device circuit is designed. In step 2 (mask production), a mask on which the designed circuit pattern is formed is produced. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the mask and the wafer. Step 5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer created in step 4. The assembly process (dicing, bonding), packaging process (chip encapsulation), and the like are performed. Including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

  FIG. 13 is a detailed flowchart of the wafer process in Step 4. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the wafer. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus to expose a circuit pattern on the mask onto the wafer. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer. According to the device manufacturing method of the present embodiment, it is possible to manufacture a higher quality device than before. Thus, the device manufacturing method using the exposure apparatus and the resulting device also constitute one aspect of the present invention.

1 is a diagram illustrating the configuration of an EUV exposure apparatus according to Embodiment 1. FIG. The enlarged view of the space division purge unit of Example 1 The enlarged view of the modification of the space division | segmentation purge unit of Example 1. FIG. The schematic diagram which shows the dimension of the space division | segmentation purge unit of Example 1. FIG. Graph showing the effect of purging helium The enlarged view of the modification of the space division | segmentation purge unit of Example 1. FIG. The schematic diagram which shows the modification of Example 1 The schematic diagram which shows the modification of Example 1 Schematic diagram showing Example 2 Configuration diagram of a conventional EUV apparatus The schematic diagram which shows the modification of Example 1 It is a flowchart for demonstrating manufacture of devices (semiconductor chips, such as IC and LSI, LCD, CCD, etc.). 13 is a detailed flowchart of the wafer process in Step 4 shown in FIG. 12.

Claims (16)

An exposure apparatus that guides and exposes light from a light source on an object to be exposed through a first space and a second space,
A gas supply port for supplying a predetermined gas into a vent between the first space and the second space;
here,
The minimum cross-sectional area having a cross-sectional area smaller than the cross-sectional area of the end portion on the first space side of the vent hole and smaller than the cross-sectional area of the end portion on the second space side of the vent hole in the vent hole. Part
The distance from the end of the vent on the first space side to the end of the vent on the second space is Lall, and the distance from the end of the first space to the minimum cross-sectional area is Lmin, when the distance from the end of the first space side to the center of the gas supply port is Lin,
Lmin−Lall / 10 <Lin <Lmin + Lall / 10
An exposure apparatus characterized by satisfying   2. The exposure apparatus according to claim 1, wherein the gas supply port is provided in the minimum sectional area.   The exposure apparatus according to claim 1, further comprising a cooling mechanism that cools the vent hole.   The exposure apparatus according to claim 3, further comprising a radiation shield so as to surround the vent and the cooling mechanism. Comprising at least one optical element for guiding light from the light source to the object to be exposed;
The exposure apparatus according to claim 4, wherein the radiation shield is disposed between the cooling mechanism and the at least one optical element.   6. The exposure apparatus according to claim 4, further comprising a temperature adjusting mechanism for adjusting the temperature of the radiation shield.   The exposure apparatus according to any one of claims 3 to 6, wherein a temperature of a cooling member included in the cooling mechanism is 40K or more and 200K or less.   8. The exposure apparatus according to claim 1, wherein the predetermined gas is any one of argon, helium, hydrogen, or a mixed gas thereof.   9. The exposure apparatus according to claim 1, wherein the pressure in the vent is controlled to about 0.1 to 10 Pa.   The apparatus has a means for measuring pressure in the first space and / or the second space, and adjusts an amount of gas supplied from the gas supply port based on a result of the measurement. The exposure apparatus according to any one of 1 to 9.   The exposure apparatus according to claim 1, wherein light from the light source to the object to be exposed passes through the vent hole.   The exposure apparatus according to claim 1, wherein the vent is disposed between the light source and an illumination optical system that guides light from the light source to a reticle.   12. The exposure according to claim 1, wherein the vent is disposed in a projection optical system that guides light from a reticle illuminated with light from the light source to the object to be exposed. apparatus.   Between the projection optical system for guiding the light from the reticle illuminated by the light from the light source to the object to be exposed and the space surrounding the reticle stage on which the reticle is placed and / or the projection optical system. 12. The exposure apparatus according to claim 1, wherein the exposure apparatus is disposed between a space surrounding a wafer stage on which the object to be exposed is placed.   The exposure apparatus according to claim 1, further comprising a flow path for exhausting the gas in the vent. 16. A device manufacturing method comprising: exposing the object to be exposed using the exposure apparatus according to claim 1; and developing the exposed object to be exposed.

Images