JP2006135203A - Temperature-controlling radiation member and exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature-controlling radiation member which is manufactured easily even when its shape is complex, and has a toughness and a high workability, and further, is excellent in its temperature controllability performed by radiation. <P>SOLUTION: The temperature-controlling radiation member for cooling a temperature-controlled unit disposed in a vacuum chamber by subjecting it to radiation has a metal or silicon main body having a radiation face whose surface is coated with a ceramic film, and has a heat-exchanger attaching portion for connecting the main body with a heat exchanger. It is desirable to coat selectively the temperature-control performing region of the radiation face with the ceramics film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radiation temperature adjusting member used in a vacuum, and more particularly to a radiation temperature adjusting member capable of efficiently cooling an optical element in an EUV exposure apparatus.

In recent years, with the demand for further miniaturization of semiconductor integrated circuits, further improvement in the resolution of optical systems limited by the diffraction limit of light has been demanded. As one of the solutions, development of a projection lithography technique using EUV light (Extreme Ultraviolet) having a wavelength shorter than that of ultraviolet rays has been advanced.
The EUV exposure apparatus is mainly composed of an EUV light source, an illumination optical system, a mask stage, an imaging optical system, a wafer stage, and the like. Since the wavelength of EUV light (5 to 20 nm) is absorbed and attenuated by the atmosphere, the optical path of the EUV light of the apparatus is maintained in a vacuum atmosphere. Further, since the refractive index of the substance is very close to 1 in the wavelength range of EUV light (particularly 11 to 14 nm), an optical element utilizing refraction cannot be used. Therefore, an EUV exposure apparatus uses a grazing incidence mirror using total reflection, a multilayer film reflecting mirror having a multilayer film formed on a reflection surface, and the like.

These mirrors absorb energy and generate heat when irradiated with EUV light. Therefore, in order to ensure stable transfer position accuracy in the EUV exposure apparatus, it is indispensable to suppress the deformation of the mirror due to the temperature rise. In this regard, the present inventor has disclosed a configuration of an exposure apparatus capable of effectively cooling an optical element in an EUV exposure apparatus in Patent Document 1.
JP 2004-153064 A

  When the mirror is cooled by the cooling mechanism using the liquid cooling pipe in the EUV exposure apparatus as described above, vibration caused by the turbulent flow of the cooling medium can be transmitted from the pipe to the mirror. Further, in the EUV exposure apparatus, since the mirror is in a vacuum atmosphere, cooling from the object surface by convection cannot be performed. For this reason, it has been studied to dispose a radiation cooling plate in the EUV exposure apparatus and cool the mirror in a vacuum atmosphere in a contacted manner by radiation.

As the material of the radiation cooling plate, ceramics (for example, alumina or the like) is advantageous in view of the high radiation rate. However, it has been pointed out that the following disadvantages occur when the radiation cooling plate is made of ceramics.
First, if the shape of the radiant cooling plate is complicated, sintering becomes difficult and the manufacturing difficulty increases. Secondly, ceramic thin plates are brittle and fragile. In particular, since the thickness of the radiant cooling plate is about 3 mm, when forming screw holes or the like for mounting a heat exchanger or positioning in an exposure apparatus, the radiant cooling plate is often cracked or chipped. Low workability has also been a problem. Thirdly, since the thermal conductivity of ceramics is not so high, temperature unevenness is likely to occur in a region where radiation temperature control is performed. In addition, since the radiation cooling plate made of ceramics emits radiation with high efficiency even outside the region where radiation temperature control is performed, temperature control control may be difficult due to the transfer of unnecessary heat with the surroundings.

  The present invention has been made to solve the above-described problems of the prior art, and its purpose is to make it easy to manufacture even in a complicated shape, to be robust and to have high workability, and to control the temperature control by radiation. It is to provide an excellent radiation temperature control member.

The invention according to claim 1 is a radiation temperature adjusting member for cooling the temperature control unit disposed in the vacuum chamber by radiation, and is made of metal or silicon having a radiation surface with a ceramic coating on the surface. And a heat exchanger mounting portion for connecting the main body to a heat exchanger.
The invention of claim 2 is characterized in that, in the invention of claim 1, the ceramic coating is selectively applied to a region of the radiation surface where radiation temperature control is performed.

The invention of claim 3 is the invention of claim 1 or claim 2, wherein the main body is made of aluminum, tungsten, molybdenum, zinc, silver, copper, gold, beryllium, magnesium, rhodium, iridium, ruthenium, sodium, potassium, Or it is formed with the alloy which has any one or more of the said metals as a main component.
The invention of claim 4 is the invention according to any one of claims 1 to 3, wherein the ceramic coating is formed of any one of aluminum nitride, alumina, titanium oxide, silica, and tungsten carbide. To do.

According to a fifth aspect of the present invention, in any of the first to fourth aspects of the present invention, the surface of the main body is subjected to a gloss treatment.
An exposure apparatus according to a sixth aspect of the invention includes a radiation cooling device using the radiation temperature adjusting member according to any one of the first to fifth aspects.

  The radiation temperature control member of the present invention forms a radiation surface by applying a ceramic film to the surface of a metal or silicon body. While the ceramic coating on the radiation surface is excellent in emissivity, the emissivity of the main body made of metal or silicon is low, so the transfer of unnecessary heat other than the ceramic coating is significantly reduced, and the temperature control unit by radiation is reduced. Temperature control is easy. Moreover, since the heat conductivity of the main body is high, heat is efficiently transferred from the heat exchanger to the ceramic coating, and the occurrence of temperature unevenness on the radiation surface is also suppressed.

  Furthermore, since the radiation temperature adjusting member of the present invention is made of metal or silicon, it is robust and has high workability. That is, the radiation temperature control member of the present invention can be easily manufactured even if it has a complicated shape, and a screw hole can be easily formed in the mounting portion of the heat exchanger.

(Description of the first embodiment)
1 and 2 are views showing a radiation temperature adjusting member according to the first embodiment of the present invention (corresponding to the radiation temperature adjusting member of claims 1 to 5). The radiation temperature adjusting member 1 is arranged in a vacuum chamber of an EUV exposure apparatus together with a circular glass substrate 2 (radiation rate 0.9) which is a temperature adjusting unit. In the first embodiment, the radiation temperature adjusting member 1 is disposed at a distance of 2 mm from the back surface of the circular glass substrate 2.

The main body portion of the radiation temperature adjusting member 1 is formed of a metal flat plate having a thickness of 4 mm. The overall shape of the main body portion is formed in a circle having substantially the same dimensions as the circular glass substrate, and three protrusions 3 are formed at equal intervals on the outer periphery of the main body portion. Each projection 3 is formed with a screw hole 3a for fixing the radiation temperature adjusting member 1 to the mount 8.
The material of the main body portion of the radiation temperature adjusting member 1 is preferably a metal having a high thermal conductivity or silicon. When the body portion is made of metal, a single metal having a thermal conductivity of 100 W / mK or more (for example, aluminum, tungsten, molybdenum, zinc, silver, copper, gold, beryllium, magnesium, rhodium, iridium, ruthenium, sodium, The main body portion is preferably formed of potassium) or an alloy mainly composed of one or more of the above metals.

However, considering the manufacturing cost of the radiation temperature control member 1, the toxicity of the material, the stability as a product, etc., the material of the main body portion is particularly preferably aluminum, tungsten, molybdenum, or zinc. In the first embodiment, the main body portion of the radiation temperature adjusting member 1 is made of aluminum.
In general, the emissivity of metal and silicon is low, so when the material of the main body is the above metal (single metal, alloy) or silicon, the emissivity is about 0.1 in both cases. Become. In addition, since the transfer of unnecessary radiant heat in the main body part is suppressed as the emissivity of the main body part decreases, it is preferable to perform a gloss treatment on the main body part of the radiation temperature adjusting member 1.

  A ceramic coating 4 is applied to a surface (radiation surface) facing the circular glass substrate 2 in the main body portion. In the present specification, the ceramic coating 4 includes a glass coating. The ceramic coating 4 is preferably formed of oxides such as alumina, titanium oxide, and silica, nitrides such as aluminum nitride, and carbides such as tungsten carbide. However, in order to conduct heat conduction efficiently with a thinner film thickness, the ceramic coating 4 is formed of aluminum nitride (radiation factor 0.6, thermal conductivity 80 to 200 W / mK), which has a thermal conductivity as high as that of metal. It is particularly preferable to do this.

  Further, the ceramic coating 4 can be obtained by (1) a method of forming a film-forming material on the radiation surface by sputtering or vapor deposition, (2) a method of directly injecting the film-forming material on the radiation surface by plasma spraying, (3) In addition, the glass material glaze can be baked onto the radiation surface. In the above method, the metal of the main body portion and the ceramic are directly bonded, and thus the adhesion is high. Alternatively, (4) a ceramic plate having a thickness of several hundreds μm to 1 mm is manufactured, and the ceramic plate is bonded to the radiation temperature control member 1 with a bonding material having a high thermal conductivity such as indium (thermal conductivity 82 W / mK). You may adhere to. In the methods (1) to (4), the ceramic coating 4 can be formed in a thickness range of 1 μm to 1 mm. However, from the viewpoint of efficient heat transfer between the main body portion and the ceramic coating 4, the thickness of the ceramic coating 4 is particularly preferably set in the range of 10 μm to 400 μm.

  Further, the ceramic coating 4 on the radiation surface is selectively selected in an optimized range in consideration of various conditions (displacement and heat transfer characteristics of the temperature control unit, arrangement of the temperature control unit and the radiation temperature control member, etc.). Formed. In the first embodiment, as a result of simulating the heat transfer efficiency from the optically effective area 2a on the surface of the circular glass substrate 2, an aluminum nitride ceramic coating 4 is formed with a film thickness of 200 μm on the entire radiation surface by plasma spraying. did. When the ceramic coating 4 is selectively formed on a part of the radiation surface, the ceramic coating 4 may be formed only in a predetermined range using a shielding plate, or the ceramic coating 4 is once formed on the entire radiation surface. Then, unnecessary portions may be removed by grinding or the like.

  On the other hand, a screw hole 5 as a heat exchanger mounting portion is formed in the vicinity of the center of the heat exchanger mounting surface (back surface of the radiation surface) in the main body portion. And the casing 7 which incorporates the heat exchanger unit 6 is being fixed with the volt | bolt 5a in the center of the heat exchanger mounting surface of a main-body part. The heat exchanger unit 6 includes, for example, a Peltier element and a liquid cooling pipe for exhaust heat (detailed illustration of the heat exchanger unit 6 is omitted).

  The radiation temperature adjustment member 1 of 1st Embodiment is comprised as mentioned above, and demonstrates the effect | action below. In the first embodiment, the emissivity of the circular glass substrate 2 is 0.9, and the emissivity of the ceramic coating 4 of the radiation temperature adjusting member 1 is 0.6. Therefore, it is possible to perform sufficiently efficient exhaust heat by radiation between the circular glass substrate 2 and the radiation temperature adjusting member 1 during the irradiation of EUV light, and the optical performance of the thermal deformation of the circular glass substrate 2 does not change. I was able to suppress it.

  Further, in the radiation temperature adjusting member 1, the radiation rate of the region where the radiation temperature is adjusted (the range of the ceramic coating 4) is 0.6, but the radiation rate of the main body is about 0.1. Therefore, since the transfer of unnecessary radiant heat in the main body portion is suppressed during cooling, the temperature controllability by the radiant temperature adjusting member 1 is kept good. Furthermore, since the aluminum main body has a high thermal conductivity, heat transfer from the heat exchanger unit 6 to the ceramic coating 4 is good, and there is little temperature unevenness in the region where radiation temperature control is performed.

Furthermore, since the main body portion of the radiation temperature adjusting member 1 is aluminum, there is no problem in formability and strength, and tapping with a tap can be easily performed. Further, the ceramic coating 4 could be easily formed by thermal spraying of aluminum nitride.
On the other hand, when the radiation temperature control member having the same shape as that of the first embodiment is formed by sintering with alumina or the like, cracks or chips occurred during sintering or screw hole formation, resulting in poor yield. Also, when this ceramic radiation temperature control member is used, the radiation rate is high except for the part that faces the circular glass substrate, so it was difficult to control the temperature control because unnecessary radiant heat was transferred. .

(Description of Second Embodiment)
3 and 4 are views showing a radiation temperature adjusting member according to a second embodiment of the present invention (corresponding to the radiation temperature adjusting member of claims 1 to 5). The second embodiment is a modification of the first embodiment, and the same reference numerals are given to the same components as those in the first embodiment, and the description thereof will be omitted.
The radiation temperature adjusting member 10 according to the second embodiment is disposed in a vacuum chamber of an EUV exposure apparatus together with the circular glass substrate 2. The main body portion of the radiation temperature adjusting member 10 is formed of a metal flat plate having a thickness of 2 mm. The main body portion has a circular portion 11 having substantially the same dimensions as the circular glass substrate, and a rectangular arm portion 12 having a base end connected to the circular portion 11. Further, the distal end side of the arm portion 12 is bent vertically upward in the figure, and the longitudinal section of the main body portion is L-shaped. A screw hole 5 is opened in the bent portion on the distal end side of the arm portion 12, and a casing 7 containing the heat exchanger unit 6 is fixed to the arm portion 12 with a bolt 5 a. Note that the radiation temperature adjusting member 10 is fixed to the exposure apparatus at the bent portion of the arm portion 12 (illustration of the fixing portion with the exposure apparatus is omitted).

  In the second embodiment, the upper surface side of the circular portion 11 is disposed to face the circular glass substrate 2 with an interval of 0.5 mm, and the upper surface side of the circular portion 11 constitutes a radiation surface. In the second embodiment, as a result of simulating the heat transfer efficiency from the optically effective area 2 a on the surface of the circular glass substrate 2, the area where the radiation temperature is adjusted is set to be an ellipse that is moved in the opposite direction of the arm portion 12. A ceramic coating 4 of alumina (radiation rate 0.9, thermal conductivity 38 W / mK) was formed to a thickness of 100 μm by plasma spraying in the region where radiation temperature control is performed.

  Also in the radiation temperature adjusting member 10 of the second embodiment described above, it is possible to perform sufficiently efficient exhaust heat by radiation almost the same as in the first embodiment, and the optical performance does not change due to thermal deformation of the circular glass substrate 2. It was possible to suppress to a certain extent. In addition, since the transmission and reception of unnecessary radiant heat in the main body portion is suppressed, and the temperature unevenness in the region where the radiant temperature is controlled is small, the controllability of the temperature control by the radiant temperature control member 10 is kept good. Furthermore, in the second embodiment, the formability, workability, and strength of the radiation temperature adjusting member 10 were all good.

  On the other hand, when the radiation temperature control member having the same shape as that of the second embodiment is formed of alumina or the like, a bent plate must be formed by sintering. The yield was very bad. Also, when this ceramic radiation temperature control member is used, the radiation rate is high except for the part that faces the circular glass substrate, so it was difficult to control the temperature control because unnecessary radiant heat was transferred. .

(Description of the third embodiment)
FIG. 5 schematically shows an EUV light lithography system 100 according to a third embodiment of the present invention (corresponding to the exposure apparatus of claim 6). The projection exposure apparatus of the third embodiment uses EUV light having a wavelength of about 5 to 20 nm as exposure illumination light. The projected image is obtained by using the image optical system 101, and a reduced image of the pattern of the reflective mask 102 is formed on the wafer 103. In FIG. 5, the optical axis of the image optical system 101 extends in the Z direction. The Y direction is a direction perpendicular to the paper surface.

  Exposure of the EUV light lithography system 100 is typically done by step scanning. Here, the mask pattern is projected onto a continuous portion (exposure area), and the mask stage 104 and the wafer stage 105 move in phase with each other during exposure. Scanning of the reflective mask 102 and the wafer 103 is performed in the direction of one degree of freedom with respect to the image optical system 101. When all areas of the reflective mask 102 are exposed to the respective areas of the wafer, pattern exposure onto the die of the wafer 103 is complete. Next, the exposure proceeds stepwise to the next die on the wafer 103.

  Since EUV light used for illumination light at the time of exposure has low permeability to the atmosphere, the optical path through which the EUV light passes is surrounded by a vacuum chamber 106 that is kept in a vacuum by a vacuum pump 107. EUV light is generated by a laser plasma X-ray source comprising a laser source 108 (acting as an excitation light source) and a xenon gas supply device 109. The laser plasma X-ray source is surrounded by a vacuum chamber 110. EUV light generated by the laser plasma X-ray source passes through the window 111 of the vacuum chamber 110. The window 111 may be an opening through which the laser plasma X-ray source can pass without interference. Note that the vacuum chamber 110 is preferably separated from the vacuum chamber 106 because dust tends to be generated by the nozzle 112 that discharges xenon gas.

  The laser source 108 generates laser light having a wavelength equal to or shorter than ultraviolet light, such as a YAG laser or an excimer laser. The laser light from the laser source 108 is condensed and applied to the flow of xenon gas emitted from the nozzle 112. When laser light is irradiated on the flow of xenon gas, the laser light sufficiently warms the xenon gas and generates plasma. When the xenon gas molecules excited by the laser fall into a low energy state, photons of EUV light are emitted.

  The parabolic mirror 113 and the condensing mirror 114 constitute an illumination system of the apparatus shown in FIG. The parabolic mirror 113 and the condensing mirror 114 are each provided with a multilayer film that reflects EUV light on the surface. In addition, the radiation temperature control member of the said 1st Embodiment or 2nd Embodiment is arrange | positioned in the vicinity of the parabolic mirror 113 and the condensing mirror 114, respectively (illustration of a radiation temperature control member is abbreviate | omitted).

  The parabolic mirror 113 is disposed in the vicinity of the xenon gas emitting part, and constitutes a condensing optical system that condenses EUV light generated by the plasma. The EUV light is reflected by the multilayer film and reaches the condenser mirror 114 through the window 111 of the vacuum chamber 110. The condensing mirror 114 condenses and reflects the EUV light to the reflective mask 102 to illuminate a predetermined portion of the reflective mask 102.

When EUV light is reflected by the reflective mask 102, the EUV light is “patterned” by pattern data from the reflective mask 102. The patterned EUV light reaches the wafer 103 through the projection system 101.
The image optical system 101 according to the third embodiment includes four reflecting mirrors: a concave first mirror 115a, a convex second mirror 115b, a convex third mirror 115c, and a concave fourth mirror 115d. Each of the mirrors 115a to 115d is provided with a multilayer film that reflects EUV light. The mirrors 115a to 115d of this embodiment are arranged so that their optical axes coincide with each other. In addition, the radiation temperature control member of the said 1st Embodiment or 2nd Embodiment is each arrange | positioned also near each mirror 115a-115d (illustration of a radiation temperature control member is abbreviate | omitted).

  In order to prevent the optical paths determined by the respective mirrors 115a to 115d from being obstructed, the first mirror 115a, the second mirror 115b, and the fourth mirror 115d are provided with appropriate notches (in FIG. (The broken line part of each indicates the notch part). The EUV light reflected by the reflective mask 102 is sequentially reflected from the first mirror 115a to the fourth mirror 115d to form an image with a reduced mask pattern. In this case, an image is formed at a predetermined reduction ratio β (for example, 1/4, 1/5, 1/6) within the exposure area of the wafer 103. The image optical system 101 is set to be telecentric on the image side (wafer side).

  The reflective mask 102 is supported downwardly at least in the XY plane by a movable mask stage 104. The wafer 103 is preferably supported by a wafer stage 105 movable in the X, Y, and Z directions. When exposing the die on the wafer, EUV light is irradiated onto a predetermined area of the reflective mask 102 by the illumination system, and the reflective mask 102 and the wafer 103 are reduced in size relative to the image optical system 101. It moves at a predetermined speed according to the rate. In this way, the mask pattern is exposed to a predetermined exposure range on the wafer 103.

  At the time of exposure, it is preferable that the wafer 103 is disposed behind the partition 116 so that gaseous dust generated from the resist on the wafer 103 by irradiation of EUV light does not affect the mirrors 115a to 115d. An opening 116a is formed in the partition 116, and EUV light is irradiated from the mirror 115d to the wafer 103 through the opening 116a. The space in the partition 116 is evacuated by a vacuum pump 117. This is to prevent deterioration in optical performance due to gaseous dust generated from the resist.

In the exposure apparatus of the third embodiment, the mirror is efficiently cooled in a non-contact manner by the radiation temperature adjusting member of the first embodiment or the second embodiment. The reliability and productivity of the apparatus can be further improved.
(Supplementary items of the embodiment)
As mentioned above, although this invention has been demonstrated by said embodiment, the technical scope of this invention is not limited to the said embodiment. In the above embodiment, an example of a projection exposure apparatus using EUV light has been described. However, the radiation temperature adjusting member of the present invention is also applied to an exposure apparatus using a charged particle beam and an optical apparatus using X-rays. be able to. The radiation temperature adjusting member of the present invention can be widely applied not only to the mirror of the exposure apparatus but also to cooling the member arranged in the vacuum chamber in a non-contact manner.

  The present invention can be applied to, for example, a radiation cooling apparatus used in an exposure apparatus using EUV light, a charged particle beam, and an optical apparatus using X-rays.

The top view of the radiation temperature control member which concerns on 1st Embodiment Longitudinal sectional view of a radiation temperature control member according to the first embodiment The top view of the radiation temperature control member which concerns on 2nd Embodiment Side view of the radiation temperature control member according to the second embodiment Outline side view of exposure apparatus of third embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiation temperature adjustment member 2 Circular glass substrate 2a Optical effective area | region 3 Protrusion part 3a Screw hole 4 Ceramic coating 5 Screw hole 5a Bolt 6 Heat exchanger unit 7 Casing 8 Base 8a Bolt 10 Radiation temperature adjustment member 11 Circular part 12 Arm part DESCRIPTION OF SYMBOLS 100 EUV light lithography system 101 Image optical system 102 Reflective mask 103 Wafer 104 Mask stage 105 Wafer stage 106 Vacuum chamber 107 Vacuum pump 108 Laser source 109 Xenon gas supply device 110 Vacuum chamber 111 Window 112 Nozzle 113 Parabolic mirror 114 Collection Optical mirrors 115a to 115d Mirror 116 Parabolic mirror 116a Aperture 117 Vacuum pump

Claims (6)

A radiation temperature control member for cooling the temperature control unit disposed in the vacuum chamber by radiation,
A radiation temperature adjusting member comprising: a metal or silicon main body having a radiation surface with a ceramic coating on the surface; and a heat exchanger mounting portion for connecting the main body to a heat exchanger.   The radiant temperature adjusting member according to claim 1, wherein the ceramic film is selectively applied to a region where the radiant temperature of the radiant surface is adjusted.   The main body is formed of aluminum, tungsten, molybdenum, zinc, silver, copper, gold, beryllium, magnesium, rhodium, iridium, ruthenium, sodium, potassium, or an alloy containing one or more of the above metals as a main component. The radiation temperature adjusting member according to claim 1 or 2, wherein   The radiation temperature-adjusting member according to any one of claims 1 to 3, wherein the ceramic coating is formed of any one of aluminum nitride, alumina, titanium oxide, silica, and tungsten carbide.   The radiant temperature adjusting member according to any one of claims 1 to 4, wherein a gloss treatment is applied to a surface of the main body. An exposure apparatus comprising a radiation cooling device using the radiation temperature adjusting member according to claim 1.

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