JP2008153396A - Illuminance equalizing apparatus, exposure apparatus, exposure method, and semiconductor device manufacturing method - Google Patents

Abstract

An illuminance uniforming optical system that efficiently removes impurities is provided.
An illuminance uniformity optical system (351a, 351b) according to the present invention includes a plurality of optical elements (3511a, 3511b), and irradiates light to the plurality of optical elements to emit light from the plurality of optical elements. Is an illuminance equalizing optical system that collects light and equalizes the illuminance, and an adsorption element (1011) that adsorbs impurities is disposed between the plurality of optical elements.
[Selection] Figure 3

Description

  The present invention relates to an illuminance equalizing apparatus, an exposure apparatus using the illuminance equalizing apparatus, and a semiconductor device manufacturing method using the exposure apparatus.

In recent years, with the miniaturization of semiconductor integrated circuits, EUV (Extreme Ultraviolet) having a shorter wavelength (11 to 14 nm) is used instead of conventional ultraviolet rays in order to improve the resolution of an optical system limited by the diffraction limit of light. A projection lithography technique using light (extreme ultraviolet rays) has been developed (for example, Patent Document 1). This technique is recently called EUV lithography, and is expected as a technique capable of obtaining a resolution of 70 nm or less, which cannot be realized by conventional optical lithography using light having a wavelength of about 190 nm.
Japanese Patent Laid-Open No. 2003-14893

  In an exposure apparatus using EUV light, a target material (target) of an EUV light source or a peripheral member sputtered by the target is scattered as particles, contaminating the optical element, for example, reducing the reflectance. Arise. Such scattered particles are called debris. In addition to debris, an oxide film or a carbon film is likely to be formed on the surface of the multilayer film of the reflecting mirror in the exposure apparatus due to moisture, carbon monoxide, carbon dioxide and organic gas. Substances that reduce the reflectivity of the reflecting mirror in the exposure apparatus, including debris and the above substances, are collectively referred to as impurities.

  Thus, impurities need to be reduced as much as possible because they lower the reflectivity of the optical element and lower the throughput of the exposure apparatus.

  Accordingly, there is a need for an illumination uniformizing optical system that efficiently removes impurities. There is also a need for an exposure apparatus and a semiconductor manufacturing method that can realize high throughput.

  The illuminance uniformizing optical system according to the present invention is characterized in that an adsorption element that adsorbs impurities is arranged in a portion where the illuminance on the surface is relatively low.

  In the illuminance uniformizing optical system according to the present invention, since the adsorption element is disposed in a portion where the illuminance on the surface is relatively low, the influence on the illuminance of the adsorption element can be reduced.

  An illuminance uniformity optical system according to the present invention includes a plurality of optical elements, and illuminance uniformity optics that irradiates the plurality of optical elements with light and collects the light from the plurality of optical elements to equalize the illuminance. An adsorption element that adsorbs impurities is arranged between the plurality of optical elements.

  In the illuminance uniformizing optical system according to the present invention, since the adsorption element is arranged between the plurality of optical elements constituting the illuminance uniforming optical system, most of the light path is not obstructed by the adsorption element. The influence on the illuminance of the adsorption element can be reduced.

  An illuminance equalizing optical system according to an embodiment of the present invention includes a fly-eye mirror.

  In the illuminance uniformizing optical system according to the present embodiment, since the adsorption element is arranged between the plurality of optical elements constituting the fly-eye mirror, most of the light path is not hindered by the adsorption element, The influence on the illuminance of the adsorption element can be reduced.

  An illuminance uniformizing optical system according to another embodiment of the present invention is characterized in that the adsorption element is made of metal, glass, or ceramic.

  According to this embodiment, since the gas released from the adsorption element is small, the degree to which the inside of the exposure apparatus is contaminated by the adsorption element is small.

  An illuminance uniformizing optical system according to another embodiment of the present invention further includes a cooling device for cooling the adsorption element.

  According to this embodiment, the adsorption efficiency of the adsorption element can be improved by maintaining the adsorption element at a low temperature by the cooling device.

  An illuminance uniformizing optical system according to another embodiment of the present invention is characterized by further comprising a device for supplying a gas to the periphery of the adsorption element so that impurities are easily adsorbed by the adsorption element.

  According to this embodiment, since the flow of impurities is hindered by the gas, the impurities are easily adsorbed by the adsorption element.

  An illumination uniformizing optical system according to another embodiment of the present invention is characterized in that the gas is an inert gas.

  According to this embodiment, the gas does not cause a carbon film or an oxide film on the surface of the multilayer reflector in the exposure apparatus.

  An illumination uniformizing optical system according to another embodiment of the present invention is characterized in that the gas is an oxidizing gas.

  According to this embodiment, when a carbon film already exists on the reflecting mirror in the exposure apparatus, the carbon film can be removed by oxidation.

  An illumination uniformizing optical system according to another embodiment of the present invention is characterized in that the gas is a reducing gas.

  According to this embodiment, when an oxide film already exists on the reflecting mirror in the exposure apparatus, the oxide film can be removed by reduction.

  An illuminance uniformizing optical system according to another embodiment of the present invention further includes a device that applies an electric field or a magnetic field to the impurities around the adsorption element so that the impurities are easily adsorbed by the adsorption element. It is characterized by.

  According to this embodiment, by applying an electric field or a magnetic field, the flow of impurities in the exposure apparatus can be changed so that the impurities can be easily adsorbed by the adsorption element.

  An exposure apparatus according to the present invention includes the illuminance uniformizing optical system according to the present invention.

  According to the exposure apparatus of the present invention, since impurities in the exposure apparatus are reduced, a reduction in the reflection efficiency of the multilayer film reflecting mirror is prevented. Therefore, the high throughput of the exposure apparatus can be maintained.

  The exposure method according to the present invention is characterized in that exposure transfer is performed using the exposure apparatus according to the present invention.

  According to the exposure method of the present invention, high throughput can be maintained.

  A method for manufacturing a semiconductor device according to the present invention includes a step of performing exposure transfer using the exposure apparatus according to the present invention.

  In the semiconductor device manufacturing method according to the present invention, since the high throughput of the exposure apparatus can be maintained, the semiconductor device can be manufactured with a high throughput.

  According to the present invention, it is possible to obtain an illuminance uniformizing optical system that efficiently removes impurities, an exposure apparatus that can achieve high throughput, and a semiconductor manufacturing method.

  FIG. 1 is a diagram showing a configuration of an EUV exposure apparatus according to an embodiment of the present invention.

  The EUV exposure apparatus includes an EUV light source 31, an illumination optical system 33, and a projection optical system 41, which will be described in detail later.

  The EUV light emitted from the EUV light source 31 becomes a substantially parallel light beam via a concave reflecting mirror 34 that acts as a collimator mirror, and enters an illuminance uniformizing optical system (optical integrator) 35 including a pair of fly-eye mirrors 35a and 35b. To do. Here, the fly-eye mirror 35b close to the EUV light source 31 on the optical path is referred to as a first fly-eye mirror, and the fly-eye mirror 35a far from the EUV light source 31 is referred to as a second fly-eye mirror.

  Thus, a substantial surface light source having a predetermined shape is formed in the vicinity of the reflective surface of the fly-eye mirror 35a, that is, in the vicinity of the exit surface of the optical integrator 35. The light from the substantial surface light source is deflected by the planar reflecting mirror 36 and then forms an elongated arc-shaped illumination area on the mask (reticle) M. Here, an aperture plate for forming an arcuate illumination region is not shown. The light reflected by the surface of the mask M is then reflected in turn by the multilayer reflectors M1, M2, M3, M4, M5, and M6 of the projection optical system 41 to form exposure light 1 on the surface of the mask M. An image of the pattern thus formed is formed on the wafer 2 (sensitive substrate) coated with the resist 3.

  As EUV light sources, laser plasma EUV light sources (hereinafter sometimes referred to as LPP (Laser Produced Plasma)) and discharge plasma EUV light sources are particularly promising. LPP focuses pulse laser light on a target material (target) in a vacuum vessel, converts the target material into plasma, and uses EUV light radiated from the plasma. In addition, an EUV light source using discharge plasma such as Dense Plasma Focus (DPF) is small in size, has a large amount of EUV light, and is low in cost.

  FIG. 2 is a diagram showing a configuration of the EUV light source 31 according to an embodiment of the present invention. The EUV light source of the present embodiment is an LPP type EUV light source. In an LPP type EUV light source, a target is supplied in a vacuum, for example, by a nozzle 205, and the target is irradiated with a pulsed laser L condensed by a laser condenser lens 201 at a condensing point P to generate high-temperature plasma. Utilize EUV light, for example 13.5 nanometers, which is generated and emitted from it. As the target material, a metal thin film, an inert gas, a droplet, or the like is used. The generated EUV light is condensed by the condenser mirror 203 and sent to the illumination optical system 33 of the exposure apparatus.

  Here, as shown in FIG. 2, the central axis of the nozzle 205 for supplying the target, the central axis of the laser beam, and the principal ray axis reflected by the condensing mirror 203 may be arranged so as to be orthogonal to each other. Good. By arranging in this way, interference with each other is prevented.

  Here, contamination of the optical element due to debris will be described. Debris consists of a target scattered or a peripheral member sputtered by the target. If debris adheres to the surface of the multilayer film or the multilayer film surface is scraped off by debris, the surface roughness of the optical element will increase, the coherence of light will change, or light will be absorbed. The reflection efficiency of the multilayer film reflecting mirror (condensing mirror) used for the EUV light source is lowered. Further, since EUV light is absorbed by almost all substances, the inside of the EUV exposure apparatus is kept in a vacuum state. For this reason, debris is diffused widely from the EUV light source of the EUV exposure apparatus to the illumination optical system and the projection optical system, and the reflection efficiency of the multilayer mirror in these optical systems is similarly reduced. As a result, the throughput of the EUV exposure apparatus decreases. As described above, impurities such as debris reduce the throughput of the exposure apparatus, and therefore must be reduced as much as possible.

  FIG. 3 is a diagram showing a configuration of the illuminance uniforming optical system 351 according to the first embodiment of the present invention. FIG. 3A is a diagram showing the configuration of the second fly-eye mirror 35a, and FIG. 3B shows the first fly-eye mirror 351b, the second fly-eye mirror 351a, and the condenser mirror 351c. It is sectional drawing which shows a structure. The condenser mirror 351c is not shown in FIG.

  As shown in FIG. 3, the first fly-eye mirror 351b and the second fly-eye mirror 351a are each composed of a large number of reflective elements 3511b and 3511a. The light collimated by the concave reflecting mirror 34 is divided into wavefronts by a number of reflecting elements 3511b of the first fly-eye mirror 351b, and the light from each reflecting surface is condensed to form a plurality of light source images. Each of the reflective elements of the second fly-eye mirror 351a is positioned in the vicinity of the position where the plurality of light source images are formed. As described above, the illuminance uniformizing optical system 351 forms a large number of light source images as secondary light sources based on the light collimated by the concave reflecting mirror 34.

  As shown in FIG. 3, in the present embodiment, a foil trap for adsorbing impurities between the reflective elements 3511b of the first fly-eye mirror 351b and between the reflective elements 3511a of the second fly-eye mirror 351a. 1011 is provided. In the present embodiment, the foil trap 1011 is arranged in a certain direction so that the respective surfaces are parallel to each other.

  The foil traps 1011 may be arranged between the reflecting elements here, but may be arranged selectively, such as every other piece or every plural pieces.

  The foil trap 1011 may be bonded between the reflective elements using an adhesive. Alternatively, the plurality of arranged reflective elements may be sandwiched and joined from both ends. Further, a cross-shaped, slatted, or interdigital foil trap may be arranged close to the reflective element. When the adhesive is not used, there is no possibility that the reflectance of the reflective element is lowered by the gas released from the adhesive.

  As shown in FIG. 3B, the dimensions, particularly the height, of the foil trap 1011 are such that impurities can be effectively adsorbed without blocking the light path as much as possible. In the fly-eye mirror, since the illuminance at the periphery of each reflective element is low, even when the light path is interrupted, the influence on the overall illuminance is small. As described above, in the fly-eye mirror, by disposing the foil trap (adsorption element) between the plurality of reflection elements, it is possible to effectively adsorb and remove impurities without reducing the overall illuminance. By removing the impurities in the illuminance uniforming optical system, it is possible to prevent the multilayer film reflecting mirror of the projection optical system 41 from being contaminated by the impurities.

  Normally, when the foil trap is installed in the optical path space of the exposure apparatus, it causes a reduction in light brightness and uneven illumination. In the exposure apparatus, the throughput decreases when the luminance of light decreases. Further, in the exposure apparatus, if the illuminance in the mask irradiation area is non-uniform, the apparent aberration increases and the line width abnormality of the mask pattern projected on the wafer increases. As a result, the defective product rate of the burned semiconductor device is increased. On the other hand, in the present embodiment, impurities can be efficiently removed while suppressing a decrease in luminance of EUV light and uneven illuminance as much as possible.

  FIG. 4 is a diagram showing a configuration of an illuminance uniforming optical system 353 according to the second embodiment of the present invention. FIG. 4A is a diagram showing a configuration of the second fly-eye mirror 353a, and FIG. 4B is a diagram of the first fly-eye mirror 353b, the second fly-eye mirror 353a, and the condenser mirror 353c. It is sectional drawing which shows a structure. The condensing mirror 353c is not shown in FIG.

  In the present embodiment, the arrangement direction of the foil traps 1013 in the second fly's eye mirror 353a is different from the arrangement direction of the foil traps 1011 in the second fly's eye mirror 351a of the first embodiment.

  As shown in FIG. 4B, the dimensions, particularly the height, of the foil trap 1013 can effectively adsorb impurities without blocking the light path as much as possible. In the fly-eye mirror, since the illuminance at the periphery of each reflective element is low, even when the light path is blocked, the influence on the overall illuminance is small. As described above, in the fly-eye mirror, by disposing the foil trap (adsorption element) between the plurality of reflection elements, it is possible to effectively adsorb and remove impurities without reducing the overall illuminance. By removing the impurities in the illuminance uniforming optical system, it is possible to prevent the multilayer film reflecting mirror of the projection optical system 41 from being contaminated by the impurities.

  FIG. 5 is a plan view showing the configuration of the first fly-eye mirror 355b according to the third embodiment of the present invention. In the present embodiment, the foil trap 1015 is installed at a position corresponding to a portion with low illuminance in the first fly-eye mirror 355b. Specifically, the condensing mirror 203 of the light source 31 has a support column that holds the condensing mirror 203, and the shadow of the support column exists as a low illuminance portion in the first fly-eye mirror 355b. As shown in FIG. 5, a foil trap 1015 is disposed in this portion. In the present embodiment, the foil trap 1015 is arranged away from the first fly-eye mirror 355b. The foil trap 1015 may be supported by a support that does not obstruct the light path. In the present embodiment, since the foil trap 1015 is disposed in a portion where the illuminance is originally low, the influence of the foil trap 1015 on the overall illuminance is small.

  In all the above embodiments, the material of the foil trap is preferably a metal, glass, ceramic, or the like that emits relatively little gas. Increasing the roughness of the surface of the foil trap increases the contact area and improves the adsorption efficiency. Therefore, activated carbon or porous ceramic (porous ceramic) may be used as the material for the foil trap. In addition, the adsorption efficiency is improved by keeping the foil trap at a low temperature. In order to keep the foil trap at a low temperature, a Peltier element or the like is used as an example.

  In all the embodiments described above, gas may be supplied in the vicinity of the illuminance homogenizing optical system provided with the foil trap so as to prevent the impurity from progressing and be easily adsorbed by the foil trap. As the gas to be used, for example, a gas that absorbs less EUV light, such as helium, argon, or nitrogen, or an inert gas that does not cause a carbon film or an oxide film on the reflecting mirror surface is preferable. When a carbon film already exists on the reflecting mirror in the exposure apparatus, an oxidizing gas such as oxygen, water, or nitric oxide may be used to remove the carbon film by oxidation. Alternatively, when an oxide film already exists on the reflecting mirror in the exposure apparatus, a reducing gas such as hydrogen or carbon monoxide may be used to remove the oxide film by reduction.

  In all the embodiments described above, when the impurity is ionized so as to be easily adsorbed by the foil trap, the traveling direction of the impurity may be changed by applying an electric field or a magnetic field to the impurity. When the impurity is not ionized, the impurity may be ionized by irradiating the impurity with an electron beam or a laser beam in advance.

  In the above description, the embodiment in which the present invention is applied to an EUV exposure apparatus has been described. However, the present invention can also be applied to an exposure apparatus that uses light of other wavelengths.

  As described above, according to the illuminance uniformizing optical system of the present invention, impurities can be efficiently removed while suppressing a decrease in luminance of EUV light and uneven illuminance as much as possible. Further, according to the exposure apparatus according to the present invention provided with the illuminance uniformizing optical system according to the present invention, impurities in the exposure apparatus are reduced, so that a reduction in the reflection efficiency of the multilayer film reflecting mirror is prevented. Therefore, the high throughput of the exposure apparatus can be maintained.

  Hereinafter, an example of an embodiment of a semiconductor device manufacturing method according to the present invention will be described. FIG. 6 is a flowchart showing an example of the embodiment of the semiconductor device manufacturing method of the present invention. The manufacturing process of this example includes the following processes.

(1) Wafer manufacturing process for manufacturing a wafer (or wafer preparation process for preparing a wafer)
(2) Mask manufacturing process for manufacturing a mask to be used for exposure (or mask preparation process for preparing a mask)
(3) Wafer processing step for performing necessary exposure processing on the wafer (4) Chip assembly step for cutting out chips formed on the wafer one by one and making them operable (5) Chip inspection step for inspecting the completed chips Each process further includes several sub-processes.

  Among these main processes, the main process that has a decisive influence on the performance of the semiconductor device is the wafer processing process. In this step, designed circuit patterns are sequentially stacked on a wafer to form a large number of chips that operate as memories and MPUs. This wafer processing step includes the following steps.

(1) A thin film forming process for forming a dielectric thin film to be an insulating layer, a wiring portion, or a metal thin film for forming an electrode portion (using CVD or sputtering)
(2) Oxidation process for oxidizing the thin film layer and wafer substrate (3) Lithography process for forming a resist pattern using a mask (reticle) to selectively process the thin film layer and wafer substrate, etc. (4) Resist Etching process (for example, using dry etching technology) that processes thin film layers and substrates according to patterns
(5) Ion / impurity implantation diffusion process (6) Resist stripping process (7) Further inspection process for inspecting the processed wafer The wafer processing process is repeated for the required number of layers to manufacture a semiconductor device that operates as designed. To do.

  In the present embodiment, the lithography apparatus according to the present invention including the illuminance uniformizing optical system according to the present invention is used in the lithography process. Therefore, since the high throughput of the exposure apparatus can be maintained, a semiconductor device can be manufactured with a high throughput.

It is a figure which shows the structure of the EUV exposure apparatus by one Embodiment of this invention. It is a figure which shows the structure of the EUV light source by one Embodiment of this invention. It is a figure which shows the structure of the illumination intensity equalization optical system by the 1st Embodiment of this invention. It is a figure which shows the structure of the illumination intensity equalization optical system by the 2nd Embodiment of this invention. It is a figure which shows the structure of the illumination intensity equalization optical system by the 3rd Embodiment of this invention. It is a flowchart which shows an example of embodiment of the semiconductor device manufacturing method of this invention.

Explanation of symbols

351b, 353b, 355b ... first fly-eye mirror, 351a, 353a ... second fly-eye mirror, 1011, 1013, 1015 ... foil trap

Claims (14)

  An illuminance homogenizing optical system, wherein an adsorption element that adsorbs impurities is disposed in a portion of the surface where the illuminance is relatively low.   An illuminance uniformizing optical system that includes a plurality of optical elements, irradiates light to the plurality of optical elements, condenses light from the plurality of optical elements, and equalizes illuminance, and the plurality of optical elements An illuminance uniforming optical system characterized in that an adsorption element for adsorbing impurities is disposed between the two.   The illuminance uniforming optical system according to claim 1, further comprising a fly-eye mirror.   The illuminance uniforming optical system according to claim 1, wherein the adsorption element has a thin plate shape.   The illuminance uniforming optical system according to claim 1, wherein the adsorption element is made of metal, glass, or ceramic.   The illuminance uniformizing optical system according to claim 1, further comprising a cooling device for cooling the adsorption element.   The illuminance uniformizing optical according to any one of claims 1 to 6, further comprising a device for supplying a gas around the adsorption element so that impurities are easily adsorbed by the adsorption element. system.   The illuminance uniforming optical system according to claim 7, wherein the gas is an inert gas.   The illuminance uniforming optical system according to claim 7, wherein the gas is an oxidizing gas.   The illuminance uniforming optical system according to claim 7, wherein the gas is a reducing gas.   11. The apparatus according to claim 1, further comprising a device that applies an electric field or a magnetic field to the impurities around the adsorption element so that the impurities are easily adsorbed by the adsorption element. Illuminance equalization optical system. An exposure apparatus comprising the illuminance equalizing optical system according to claim 1.   An exposure method comprising performing exposure transfer using the exposure apparatus according to claim 12.   A method of manufacturing a semiconductor device, comprising the step of performing exposure transfer using the exposure apparatus according to claim 12.

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