JP2005244012A - Optical system, aligner employing it, and process for fabricating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner bringing about a desired optical performance by reducing deformation of an optical member due to thermal expansion which causes degradation in image formation performance. <P>SOLUTION: The optical system including a first optical element and a second optical element comprises a first control means for controlling the first optical element to a first temperature, and a second control means for controlling the second optical element to a second temperature wherein the first temperature and the second temperature are different from each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure apparatus that exposes an object to be processed such as a single crystal substrate for a semiconductor wafer and a glass substrate for a liquid crystal display (LCD). The present invention is particularly suitable for an exposure apparatus that performs exposure using ultraviolet rays or extreme ultraviolet (EUV) light as an exposure light source.

  When a fine semiconductor element such as a semiconductor memory or a logic circuit is manufactured using a photolithography technique, a circuit pattern drawn on a reticle or a mask (these terms are used interchangeably in this application). Conventionally, a reduction projection exposure apparatus that projects a circuit pattern by projecting the image onto a wafer or the like by a projection optical system has been used.

  The minimum dimension (resolution) that can be transferred by the reduction projection exposure apparatus is proportional to the wavelength of light used for exposure and inversely proportional to the numerical aperture (NA) of the projection optical system. Therefore, the shorter the wavelength, the better the resolution. For this reason, with the recent demand for miniaturization of semiconductor elements, the exposure light has been shortened, and an ultra-high pressure mercury lamp (i-line (wavelength: about 365 nm)), KrF excimer laser (wavelength: about 248 nm), ArF excimer. The wavelength of ultraviolet light used with lasers (wavelength about 193 nm) has become shorter.

  However, semiconductor elements are rapidly miniaturized, and there is a limit in lithography using ultraviolet light. Therefore, in order to efficiently transfer a very fine circuit pattern of 0.1 μm or less, a reduction projection exposure apparatus using extreme ultraviolet (EUV) light having a wavelength shorter than that of ultraviolet light and having a wavelength of about 10 nm to 15 nm ( Hereinafter, it is referred to as “EUV exposure apparatus”).

  As exposure light becomes shorter in wavelength, the absorption of light by a substance becomes very large. Therefore, it is difficult to use a refraction element utilizing refraction of light such as that used in visible light or ultraviolet light, that is, a lens. There is no glass material that can be used in the wavelength region of light, and a reflective optical system that uses only light reflection, that is, a mirror (for example, a multilayer mirror) to form an optical system is used.

The mirror does not reflect all of the exposure light, but absorbs 30% or more of the exposure light incident on the mirror per mirror. The absorbed exposure light is divided into heat and deforms the surface shape of the mirror, causing deterioration of optical performance (particularly imaging performance). Therefore, the mirror is made of a low thermal expansion material having a very small linear expansion coefficient, for example, a linear expansion coefficient of 5 ppb / K in order to reduce the change in the mirror shape due to temperature change (Patent Documents 1 and 2).
JP 2003-188097 A JP 2003-267789 A

  However, since the EUV exposure apparatus uses a wavelength that is an order of magnitude smaller than that of conventional ultraviolet rays, the deformation of the surface shape of the mirror needs to be an order of magnitude smaller than that of the conventional one, and only a deformation of about 0.1 nm rms or less is allowed. Not. For example, if the linear expansion coefficient of the mirror is 5 ppb / K and the thickness of the mirror is 100 mm, the shape of the mirror surface changes by 0.1 nm due to a temperature rise of only 0.2 ° C., and the EUV exposure apparatus The allowable value of the deformation of the surface shape of the mirror is reached.

  Therefore, the present invention provides an optical system that can reduce the change in optical characteristics of an optical system having a mirror even if the temperature of the mirror slightly changes, or an exposure apparatus that includes such an optical system. For illustrative purposes.

  In order to achieve the above object, an exposure apparatus according to an aspect of the present invention is an optical system including a first optical element and a second optical element, and controls the first optical element to a first temperature. 1 control means and second control means for controlling the second optical element to a second temperature, wherein the first temperature and the second temperature are different from each other.

  Here, when the temperature at which the linear expansion coefficient of the first optical element becomes zero is the first zero crossing temperature, and the temperature at which the linear expansion coefficient of the second optical element becomes zero is the second zero crossing temperature, More preferably, the first zero crossing temperature and the second zero crossing temperature are different from each other.

  Further, when the temperature at which the linear expansion coefficient of the first optical element becomes zero is defined as the first zero crossing temperature, the difference between the first zero crossing temperature and the first temperature is preferably within 1.5 degrees. . Further, when the temperature at which the linear expansion coefficient of the second optical element becomes zero is defined as the second zero crossing temperature, the difference between the second zero crossing temperature and the second temperature is preferably within 1.5 degrees. .

  Further, when the temperature at which the linear expansion coefficient of the first optical element becomes zero is the first zero crossing temperature, and the temperature at which the linear expansion coefficient of the second optical element becomes zero is the second zero crossing temperature, More preferably, the difference between the zero crossing temperature and the second zero crossing temperature is 0.1 degrees or more.

  Further, when the temperature at which the linear expansion coefficient of the first optical element becomes zero is the first zero crossing temperature, and the temperature at which the linear expansion coefficient of the second optical element becomes zero is the second zero crossing temperature, The difference between the temperature and the second temperature is preferably 6.0 degrees or less.

  An exposure apparatus according to one aspect of the present invention is characterized in that an object to be exposed is exposed using light from a light source using the above-described optical system. Moreover, you may make it have the illumination optical system which guides the light from a light source to an original, and the above-mentioned optical system which guides the light from the said original to an to-be-exposed body.

  An exposure apparatus according to another aspect of the present invention includes a vacuum chamber having a vacuum atmosphere therein, a first optical element disposed in the vacuum chamber and having a linear expansion coefficient of zero at a first zero crossing temperature, A second optical element that is disposed in the vacuum chamber and has a linear expansion coefficient of zero at a second zero crossing temperature, and a first that controls the temperature of the first optical element to be the first temperature using radiation. Control means, and second control means for controlling the temperature of the second optical element to be a second temperature using radiation, and the light from the light source is the first optical element and the second optical element. An exposure apparatus that leads to an object to be exposed via the first and second control means, wherein the first temperature and the second temperature are different from each other by using the first control means and the second control means. .

  An exposure apparatus according to another aspect of the present invention includes a vacuum chamber having a vacuum atmosphere therein, a first optical element disposed in the vacuum chamber and having a linear expansion coefficient of zero at a first zero crossing temperature, A second optical element that is disposed in the vacuum chamber and has a linear expansion coefficient of zero at a second zero crossing temperature, and a first that controls the temperature of the first optical element to be the first temperature using radiation. Control means, and second control means for controlling the temperature of the second optical element to be a second temperature using radiation, and the light from the light source is the first optical element and the second optical element. An exposure apparatus that guides an object to be exposed through the first and second control means, wherein a difference between the first zero-crossing temperature and the first temperature is within 1.5 degrees using the first control means and the second control means. Yes, the difference between the second zero crossing temperature and the second temperature is 1 Within 5 degrees, the difference between the first zero crossing temperature and the second zero crossing temperature is not less than 0.1 degrees and not more than 6 degrees, and the first temperature and the second temperature are different from each other. It is characterized by that.

  Here, you may comprise so that the light from the said light source may be EUV light with a wavelength of 20 nm or less.

  The device manufacturing method of the present invention is characterized by comprising the steps of exposing the object to be exposed using the exposure apparatus described above and developing the exposed object to be exposed.

  Here, the claim of the device manufacturing method that exhibits the same operation as the operation of the above-described exposure apparatus extends to the intermediate and final device itself. Such devices include semiconductor chips such as LSI and VLSI, CCDs, LCDs, magnetic sensors, thin film magnetic heads, and the like.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, the optical system which can reduce the deformation | transformation by the thermal expansion of the optical member which will deteriorate imaging performance is realizable.

  First, the principle capable of reducing the mirror shape change with respect to the temperature change will be described. The shape of an optical element such as a mirror changes as the temperature changes. The amount of change changes in proportion to the linear expansion coefficient of the material constituting the mirror. Therefore, if the linear expansion coefficient is 0 (zero), the shape of the mirror does not change even if the temperature changes. However, no material having such a linear expansion coefficient of 0 has been found. However, there are materials that have a linear expansion coefficient of 0 at a predetermined temperature. Therefore, in the present embodiment, the mirror (optical element) is made of a material whose linear expansion coefficient becomes 0 (zero) at or near the temperature actually used. As a result, it is possible to reduce the amount of change in the shape of the mirror with respect to the temperature change, and in turn, it is possible to reduce deterioration (change) in the optical performance of the optical system including the mirror.

Here, regarding a mirror material having a temperature at which the linear expansion coefficient becomes zero (zero crossing temperature) Tz, the linear expansion coefficient CTE can be expressed by the following mathematical expression in the vicinity of the temperature Tz.
CTE (T) = A (T−Tz) (ppb / K): T... Temperature (° C.)
Here, CTE (T) is a linear expansion coefficient CTE (a function of temperature T), A is a gradient of CTE (T) with respect to temperature T, and Tz is a temperature at which the linear expansion coefficient of the material constituting the mirror is 0. Represents. As is clear from this mathematical expression, if the above materials are used while being controlled at a temperature in the vicinity of the temperature Tz at which the linear expansion coefficient becomes zero, the change in the surface shape of the mirror accompanying the temperature change is reduced. As a result, the optical characteristics of the optical system including the mirror can be stabilized without depending on the temperature change.

  However, when producing a mirror material, it is very difficult to manufacture at a constant temperature at which the linear expansion coefficient of the material becomes zero. As a result, the temperature at which the linear expansion coefficient of the mirror material becomes zero varies. For example, even if the mirror material is manufactured so that the temperature at which the linear expansion coefficient becomes zero becomes 23 ° C., the temperature at which the linear expansion coefficient of the actually manufactured mirror material becomes zero is about 20 ° C. to 26 ° C. There is a possibility of variation in the range of (22-24 ° C or 22.5-23.5 ° C). For this reason, in an optical system using a plurality of mirrors, when the entire optical system is managed at the same temperature, there are mirrors where the temperature at which the linear expansion coefficient of the mirror is zero and the temperature of the entire optical system are close to those that are not. Arise. For a mirror with a large difference between the temperature of the entire optical system (set temperature of the mirror) and the temperature at which the linear expansion coefficient becomes zero, the linear expansion coefficient of the material of the mirror becomes large. There is a problem in that the amount of deformation of the mirror due to heat increases, and as a result, the optical system having the mirror becomes an optical system in which aberrations are likely to occur with respect to temperature changes.

  Therefore, in this embodiment, in an exposure apparatus including a plurality of mirrors using a material having a temperature at which the linear expansion coefficient becomes zero, the linear expansion coefficient (generated by a manufacturing error) of each mirror material becomes zero. An exemplary object of the present invention is to provide an optical system capable of reducing the amount of change in the shape of a mirror with respect to a temperature change, an exposure apparatus including the same, and a device manufacturing method. .

  Hereinafter, an exposure apparatus which is an exemplary embodiment of the present invention will be described with reference to the accompanying drawings. Here, FIG. 1 is a schematic block diagram that shows an exposure apparatus 500 as the present embodiment.

  The exposure apparatus 500 of the present embodiment is formed on the mask 520 by using, for example, a step-and-scan method or a step-and-repeat method using EUV light (for example, wavelength 13.4 nm) as exposure illumination light. The projection exposure apparatus exposes the processed circuit pattern to the object to be processed 540. Such an exposure apparatus is suitable for a lithography process of sub-micron or quarter micron or less, and in the present embodiment, a step-and-scan type exposure apparatus (also referred to as “scanner”) will be described as an example. Here, the “step and scan method” means that the wafer is continuously scanned (scanned) with respect to the mask to expose the mask pattern onto the wafer, and the wafer is stepped after the exposure of one shot is completed. The exposure method moves to the next exposure area. The “step-and-repeat method” is an exposure method in which the wafer is stepped and moved to the exposure area of the next shot for every batch exposure of the wafer.

  Referring to FIG. 1, an exposure apparatus 500 includes an illumination apparatus 510, a mask stage 525 on which a mask 520 is placed, a wafer stage 545 on which an object 540 is placed, and an image of the mask 520 described above. A projection optical system 530 formed on the body, an alignment detection mechanism 550, and a focus position detection mechanism 560 are included.

  Further, as shown in FIG. 1, since EUV light has a low transmittance with respect to the atmosphere, at least an optical path through which the EUV light passes (that is, the entire optical system) is a vacuum atmosphere VC.

  The illumination device 510 is an illumination device that illuminates the mask 520 with arc-shaped EUV light (for example, a wavelength of 13.4 nm) with respect to the arc-shaped field of the projection optical system 530. The illumination device 510 includes an EUV light source 512, an illumination optical system 514, and the like. Have

  As the EUV light source 512, for example, a laser plasma light source is used. In this method, a target material in a vacuum vessel is irradiated with high-intensity pulsed laser light to generate high-temperature plasma, and EUV light having a wavelength of, for example, about 13 nm is emitted from the target material. As the target material, a metal film, a gas jet, a droplet, or the like is used. In order to increase the average intensity of the 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 514 includes a condenser mirror 514a (which may be a concave mirror or a convex mirror) and an optical integrator 514b. The condensing mirror 514a plays a role of collecting EUV light emitted from the laser plasma almost isotropically. The optical integrator 514b has a role of uniformly illuminating the mask 520 with a predetermined numerical aperture.

  The mask 520 is a reflective mask on which a circuit pattern (or image) to be transferred is formed. This mask is supported and fixed to a mask stage using an electrostatic chuck or the like, and is driven integrally with the mask stage. The diffracted light emitted from the mask 520 is reflected by the projection optical system 530 and projected onto the object to be processed 540. The mask 520 and the workpiece 540 are arranged in an optically conjugate relationship. Since the exposure apparatus 500 is a step-and-scan exposure apparatus, the pattern of the mask 520 is reduced and projected onto the object 540 by scanning the mask 520 and the object 540.

  The mask stage 525 supports the mask 520 and is connected to a moving mechanism (not shown). The mask stage 525 may employ any structure known in the art. A moving mechanism (not shown) is configured by a linear motor or the like, and can move the mask 520 by driving the mask stage 525 at least in the X direction. The exposure apparatus 500 scans the mask 520 and the workpiece 540 in synchronization with each other in consideration of the magnification of the projection optical system. Here, X is a scanning direction within the surface of the mask 520 or the object to be processed 540, Y is a direction perpendicular thereto, and Z is a direction substantially perpendicular to the surface of the mask 520 or the object to be processed 540.

  The projection optical system 530 uses a plurality of reflection mirrors (that is, multilayer mirrors) to reduce and project the pattern on the mask 520 surface onto the object to be processed 540 that is an image plane. The number of the plurality of mirrors is about 4 to 6. FIG. 1 shows an example of four mirror systems M1, M2, M3, and M4 in the order in which light is reflected from the mask side. In order to realize a wide exposure area with a small number of mirrors of about 4 to 8 (preferably an even number such as 4, 6, 8, etc.), it is separated by a certain distance from the optical axis. Using only a thin arc-shaped region (ring field), the mask 520 and the object to be processed 540 are simultaneously scanned to transfer the pattern on the mask surface to a large area on the object to be processed. The numerical aperture (NA) of the projection optical system 530 is about 0.2 to 0.3.

  The object to be processed 540 is a wafer in the present embodiment, but widely includes liquid crystal substrates and other objects to be processed. A photoresist is applied to the object to be processed 540. The photoresist coating process includes a pretreatment, an adhesion improver coating process, a photoresist coating process, and a prebaking process. Pretreatment includes washing, drying and the like. The adhesion improver coating process is a surface modification process for improving the adhesion between the photoresist and the base (that is, a hydrophobic process by application of a surfactant), and an organic film such as HMDS (Hexmethyl-disilazane) is used. Coat or steam. Pre-baking is a baking (baking) step, but is softer than that after development, and removes the solvent.

  Wafer stage 545 supports object 540 to be processed by wafer chuck 545a. For example, the wafer stage 545 moves the object 540 in the XYZ directions using a linear motor. The wafer stage 545 on which the object to be processed 540 is placed is scanned in synchronization with the aforementioned mask stage in consideration of the projection magnification of the projection optical system. Further, the position of the mask stage 525 and the position of the wafer stage 545 are monitored by, for example, a laser interferometer or the like, and both are driven at a constant speed ratio.

  The alignment detection mechanism 550 measures the positional relationship between the position of the mask 520 and the optical axis of the projection optical system 530, and the positional relationship between the position of the object 540 and the optical axis of the projection optical system 530, and The positions and angles of the mask stage 525 and the wafer stage 545 are set so that the projected image coincides with a predetermined position of the object 540 to be processed.

  The focus position detection mechanism 560 measures the focus position in the Z direction on the surface of the object to be processed 540 and controls the position and angle of the wafer stage 545, so that the surface of the object to be processed 540 is always projected by the projection optical system 530 during exposure. Keep at the imaging position.

  In the exposure, the EUV light emitted from the illumination device 510 illuminates the mask 520 and forms a pattern on the surface of the mask 520 on the surface of the object to be processed 540. In the present embodiment, the image surface is an arc-shaped (ring-shaped) image surface, and the entire surface of the mask 520 is exposed by scanning the mask 520 and the object to be processed 540 at the speed ratio of the reduction ratio.

  Next, the characteristics of the linear expansion coefficient of each mirror material of the projection optical system 530 in FIG. 1 and the temperature of each mirror will be described with reference to FIGS.

  FIG. 2 is a diagram illustrating an example of the temperature dependence of the linear expansion coefficient of the mirror material, in which the horizontal axis represents temperature T (° C.) and the vertical axis represents linear expansion coefficient CTE (Coefficient of Thermal Expansion). The mirror material used in the present invention has a temperature at which the linear expansion coefficient CTE becomes zero, and the temperature is denoted as Tz (° C.).

The linear expansion coefficient CTE changes almost linearly at a temperature near Tz (° C.).
For example, in the case of a material with Tz = 23.0 ° C. and a slope A of −1.25 [ppb / K / K],
It is approximated by CTE = −1.25 × (T−23.0) [ppb / K]. In that case, by controlling the mirror temperature in the vicinity of 23.0 ° C., deformation due to temperature change (heat) can be reduced.

  When the mirror temperature deviates from Tz, the CTE gradually increases, so the amount of deformation of the mirror due to unit temperature change (heat) increases, and the amount of aberration generated thereby increases.

  Here, as described above, since it is very difficult to manufacture the materials constituting the plurality of mirrors at the same temperature at which the linear expansion coefficient becomes zero, when using a plurality of mirrors, It is assumed that the value of the temperature Tz at which the linear expansion coefficient of each mirror material becomes zero varies (is different from each other).

  Therefore, in this embodiment, by controlling the temperature of a plurality of mirrors having different linear expansion coefficients to be different from each other so that each mirror has an optimum temperature, each mirror and the optical system including these mirrors are controlled. Deterioration (change) in optical performance of the system is suppressed. The temperature of the mirror (control target temperature when controlling the mirror temperature) is preferably a temperature at which the linear expansion coefficient of the material of each mirror becomes zero, but is within 1.5 ° C. (preferably 1.0). It may be deviated as long as it is within ℃, more preferably within 0.5 ℃.

  A specific numerical example is as shown in FIG. FIG. 3 shows a temperature Tz at which the linear expansion coefficient of each of the mirrors M1 to M4 in Examples 1 to 4 becomes zero, and a target temperature Tc of each mirror when the temperature of each mirror is controlled. As shown in FIG. 3, a target value (control target temperature) for each mirror is set for each mirror, and each mirror is cooled (or / and / or) by a cooling mechanism (not shown) so as to reach the target value. The temperature is controlled by heating.

  At that time, among a plurality of mirrors (four mirrors in this embodiment), a control target temperature of one mirror and a control target temperature of another mirror are set to be different from each other. Specifically, as in the first to third embodiments in FIG. 3, the temperature at which the linear expansion coefficient of each mirror material becomes zero may be different from each other. Different control target temperatures are set, and control is performed so that the temperatures are different from each other. In the fourth embodiment, temperature control is performed so that both M1 and M2 having the same linear expansion coefficient of 0 have the same temperature (temperature at which the linear expansion coefficient becomes 0).

  As described above, a plurality of mirrors constituting the optical system (projection optical system and / or illumination optical system of the exposure apparatus) (in this embodiment, two mirrors having different temperatures at which the linear expansion coefficient becomes 0 are different from each other. When controlling the temperature of each of the four mirrors), each mirror temperature (control target temperature of each mirror) is controlled so as to be a temperature Tz at which the linear expansion coefficient of each mirror material becomes zero. The amount of change in shape with respect to the temperature change of the mirror is reduced.

  However, if the temperature Tz at which the linear expansion coefficient of the material of each mirror becomes zero coincides with each mirror temperature (control target temperature of each mirror), the amount of aberration of the entire optical system having each mirror increases (optical) When the wavefront measurement result of the system is very bad or a certain aberration of the optical system is large), the temperature at which the mirror temperature (mirror control target temperature) and the linear expansion coefficient of the mirror material become zero The mirror temperature may be controlled so that Tz differs from each other. However, the difference between the mirror temperature and the temperature Tz at which the linear expansion coefficient of the mirror material becomes zero is desirably within 1.5 degrees (preferably within 1.0 degree, more preferably within 0.5 degree). .

  Furthermore, an optical system having such a mirror has a high light absorption rate in each mirror, such as an illumination optical system or projection optical system of an exposure apparatus using EUV light (5% or more, preferably 10% or more, (More preferably 25% or more) When applied to an optical system, the temperature of the optical system may be determined as follows. In the case of such an optical system having a high light absorption rate in each mirror, a mirror closer to the light source on the optical path (which may be called the reticle side in the case of a projection optical system) increases the amount of light absorption and It is desirable that the temperature of the mirror close to the light source is close to the temperature at which the linear expansion coefficient becomes zero, because temperature changes and deformation easily occur. Conversely, the closer the mirror is to the object to be exposed (substrate such as a wafer), the smaller the amount of light absorption and the less likely the temperature change or deformation of the mirror occurs (if any). It may be slightly deviated from the temperature at which the linear expansion coefficient of the mirror material becomes zero. Specifically, the temperature of the mirror closest to the light source is within 1.5 degrees (preferably within 1.0 degree, more preferably within 0.1 degree) from the zero crossing temperature (the temperature at which the linear expansion coefficient of the mirror material becomes zero). The temperature of the mirror on the object to be exposed is adjusted so that the deviation from the zero-crossing temperature of the mirror is within 2.0 degrees or 3.0 degrees. The control target temperature may be set so that specific aberrations such as aberration, distortion, and astigmatism are within a desired range.

  As described above, regarding the material of each mirror, it is desirable to set the control target temperature of each mirror in the vicinity of the temperature at which the linear expansion coefficient becomes 0. However, if the control target temperature between the mirrors is too large, the control is performed. Therefore, the difference in temperature target value (control target temperature) between the mirror controlled to the highest temperature and the mirror controlled to the lowest temperature is 6 degrees or less (preferably 3 degrees or less, more preferably 1.5 degrees or less). ) Is desirable.

  On the other hand, when the difference between the maximum value and the minimum value of the temperature at which the linear expansion coefficient becomes zero among the plurality of mirrors is Tdif, the mirror that is controlled to the highest temperature and the mirror that is controlled to the lowest temperature, The difference in target temperature values is greater than (Tdif−0.1) degrees and / or greater than 0.1 degrees (more preferably 0.4 degrees).

  By adjusting the temperature of each mirror in this way, the amount of aberration change with respect to the temperature change of the optical system including these mirrors can be reduced. In addition, when the temperatures of the materials constituting the plurality of mirrors of the optical system are different from each other (the temperature at which the coefficient of linear expansion is zero among the materials constituting the plurality of mirrors) The difference from the lowest value is 0.1 degree or more, more preferably 0.3 degree or more, and still more preferably 1.0 degree or more. By doing so, the effect of reducing the expansion of each mirror due to a temperature change and reducing the amount of aberration of the optical system caused by the thermal deformation of the mirror due to exposure and the thermal deformation becomes significant.

  Of course, it is not necessary to set different control target temperatures for all of the mirrors, the temperature at which the linear expansion coefficient of the first mirror among the plurality of mirrors constituting the optical system becomes zero, and the linear expansion coefficient of the second mirror. When the temperature at which the value becomes zero is different, the control target temperature of the first mirror and the control target temperature of the second mirror may be different from each other. At this time, the control target temperature of the third mirror and / or the control target temperature of the fourth mirror may be the same as the control target temperature of the first mirror. Also, as in M2 and M3 in the fourth embodiment, different control target temperatures may be set even if the temperatures at which the linear expansion coefficients are zero are the same, or M1 in the third embodiment. Although the temperatures at which the linear expansion coefficient becomes zero are different from each other like M2 and M2, the control target temperature may be the same.

  Next, the aforementioned cooling mechanism will be briefly described. As the cooling mechanism, there is one as shown in FIG. In addition, any known cooling mechanism may be used. 6 includes an optical member (a mirror in FIG. 6) in a space (vacuum atmosphere) surrounded by a vacuum chamber, and EUV light (13 to 14 nm) or the like on the surface side of the optical member. The exposure light is irradiated. A temperature detection unit that detects the temperature of the optical member using a temperature sensor, and a temperature control unit that receives a temperature detection result from the temperature detection unit and sends a command to a Peltier element control unit that controls the Peltier element (mirror temperature) Control unit). Here, one of the Peltier elements is arranged opposite to the above-mentioned optical member (mirror), a radiation plate for adjusting the temperature of the optical member by radiation is arranged, and a cooling jacket is arranged on the other side of the Peltier element Has been. The cooling jacket is controlled so as to have a substantially constant temperature by the heat medium flowing from the heat medium circulation device through the heat medium pipe. In such a configuration, by controlling the temperature of the cooling jacket and the above-described Peltier element, the temperature of the radiation plate is adjusted, and consequently, the temperature of the optical member (mirror) is adjusted (cooled).

  Here, since the temperature sensor is provided on the back side of the mirror, the temperature of the back side of the mirror is detected instead of the front side of the mirror that is actually irradiated with the exposure light. Of course, the temperature sensor detects the temperature of the rear surface side of the mirror and / or the side surface of the mirror and / or the front surface side of the mirror (providing a temperature sensor that can detect the temperature of the non-irradiated area of the exposure light or the surface of the mirror in a non-contact manner). You may make it do. Then, the temperature distribution of the mirror may be calculated based on the detection results, and the control target temperature may be determined based on the temperature distribution, or the output of a predetermined temperature sensor and the control target temperature (temperature distribution may be associated in advance). The control target temperature may be determined based on the relationship. Thus, the control target temperature of the mirror is determined, and the temperature of the mirror is adjusted using a radiation member (radiation plate) so that the mirror has a desired temperature.

  Here, the control target temperature Tc is, of course, the control target value of the mirror temperature. Here, “the temperature of the mirror (optical element)” refers to the average temperature of the entire mirror, the average temperature in the thickness direction with respect to the light irradiation area of the mirror, or within a predetermined area of the mirror (predetermined). The average temperature in the thickness direction is acceptable. However, of course, the control target temperature is not limited to this, and may be the surface temperature of the mirror, the surface temperature on the back side of the mirror, or the temperature of the point (area) at which the temperature is measured by the temperature sensor. It may be a numerical value calculated based on a plurality of detected values from a plurality of temperature sensors. However, since the purpose is to reduce the amount of deformation accompanying the temperature change of the mirror, the control target temperature Tc is preferably the average temperature of the entire mirror or the average temperature in the thickness direction with respect to the light irradiation region of the mirror. .

  Further, in the description of Examples 1 to 4 in FIG. 3 or other descriptions, it is considered that the control target temperature of each mirror is substantially equivalent to the actual temperature of the optical element (mirror). The target temperature and the (actual) temperature of the optical element may be used interchangeably within a consistent range, and may be interpreted as interchangeable terms.

  Next, an embodiment of a device manufacturing method using the above-described exposure apparatus 500 will be described with reference to FIGS. FIG. 4 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. 5 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. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition or the like. 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 500 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 500 and the resulting device also constitute one aspect of the present invention.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist. For example, the present invention can also be applied to an exposure apparatus including a reflecting mirror that exposes light other than EUV light, such as g-line, h-line, i-line, ArF excimer laser, and F ₂ laser. Further, it can be applied not only to the imaging mirror of the projection optical system but also to a mask. Further, it can be applied not only to the projection optical system but also to the illumination optical system.

1 is a schematic block diagram showing an exemplary embodiment of an exposure apparatus as one aspect of the present invention. It is a figure which shows the example of the temperature dependence of the linear expansion coefficient of mirror material. It is a figure which shows the temperature from which the linear expansion coefficient of each mirror material of the projection optical system in the Example of FIG. It is a flowchart for demonstrating manufacture of devices (semiconductor chips, such as IC and LSI, LCD, CCD, etc.). 5 is a detailed flowchart of the wafer process in Step 4 shown in FIG. 4. It is the schematic of the radiation cooling mechanism of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 500 Exposure apparatus 510 Illumination apparatus 512 EUV light source 514 Illumination optical system 520 Mask 530 Projection optical system M1 1st mirror M2 2nd mirror M3 3rd mirror M4 4th mirror Tz Temperature at which the linear expansion coefficient becomes zero Tc Control target temperature of the mirror CTE linear expansion coefficient

Claims (12)

An optical system including a first optical element and a second optical element,
First control means for controlling the first optical element to a first temperature; and second control means for controlling the second optical element to a second temperature;
The optical system, wherein the first temperature and the second temperature are different from each other.   When the temperature at which the linear expansion coefficient of the first optical element becomes zero is the first zero-crossing temperature, and the temperature at which the linear expansion coefficient of the second optical element becomes zero is the second zero-crossing temperature, the first zero-crossing temperature. The optical system according to claim 1, wherein a temperature and the second zero crossing temperature are different from each other.   When a temperature at which the linear expansion coefficient of the first optical element becomes zero is defined as a first zero crossing temperature, a difference between the first zero crossing temperature and the first temperature is within 1.5 degrees. The optical system according to claim 1 or 2.   When a temperature at which the linear expansion coefficient of the second optical element becomes zero is a second zero crossing temperature, a difference between the second zero crossing temperature and the second temperature is within 1.5 degrees. The optical system according to claim 1.   When the temperature at which the linear expansion coefficient of the first optical element becomes zero is the first zero-crossing temperature, and the temperature at which the linear expansion coefficient of the second optical element becomes zero is the second zero-crossing temperature, the first zero-crossing temperature. The optical system according to claim 1, wherein a difference between a temperature and the second zero crossing temperature is 0.1 degrees or more.   When the temperature at which the linear expansion coefficient of the first optical element becomes zero is the first zero crossing temperature, and the temperature at which the linear expansion coefficient of the second optical element becomes zero is the second zero crossing temperature, The optical system according to claim 1, wherein a difference from the second temperature is 6.0 degrees or less.   An exposure apparatus that exposes an object to be exposed using light from a light source using the optical system according to claim 1.   An exposure apparatus comprising: an illumination optical system that guides light from a light source to an original; and an optical system according to claim 1 that guides light from the original to an object to be exposed. A vacuum chamber having a vacuum atmosphere inside;
A first optical element disposed in the vacuum chamber and having a linear expansion coefficient of zero at a first zero crossing temperature;
A second optical element disposed in the vacuum chamber and having a linear expansion coefficient of zero at a second zero crossing temperature;
First control means for controlling the temperature of the first optical element to be a first temperature using radiation;
Second control means for controlling the temperature of the second optical element to be a second temperature by using radiation, and the light from the light source is received through the first optical element and the second optical element. An exposure apparatus that leads to an exposure body,
An exposure apparatus characterized in that the first temperature and the second temperature are different from each other using the first control means and the second control means. A vacuum chamber having a vacuum atmosphere inside;
A first optical element disposed in the vacuum chamber and having a linear expansion coefficient of zero at a first zero crossing temperature;
A second optical element disposed in the vacuum chamber and having a linear expansion coefficient of zero at a second zero crossing temperature;
First control means for controlling the temperature of the first optical element to be a first temperature using radiation;
Second control means for controlling the temperature of the second optical element to be a second temperature by using radiation, and the light from the light source is received through the first optical element and the second optical element. An exposure apparatus that leads to an exposure body,
Using the first control means and the second control means, a difference between the first zero crossing temperature and the first temperature is within 1.5 degrees, and the second zero crossing temperature and the second temperature are The difference between the first zero-crossing temperature and the second zero-crossing temperature is 0.1 degrees or more and 6 degrees or less, and the first temperature and the second temperature are An exposure apparatus characterized by being different from each other.   The exposure apparatus according to claim 7, wherein the light from the light source is EUV light having a wavelength of 20 nm or less.   12. A device manufacturing method comprising: exposing the object to be exposed using the exposure apparatus according to claim 7; and developing the exposed object to be exposed.

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