Patent Application
20110259374
1. Field of the Invention
The present invention relates to a cleaning apparatus and a cleaning method for cleaning an object by supplying a hydrogen radical to the object, and a lithography apparatus that includes such a cleaning apparatus.
2. Description of the Related Art
Concerning the lithography apparatus, Japanese Patent Application Laid-Open No. 2007-184577 discusses a configuration that cleans a part of the apparatus using a hydrogen radical. In the configuration discussed therein, the hydrogen radical is generated by supplying hydrogen-containing gas to a heated catalyst (e.g., tungsten heated to 1500 to 3000 kelvins). The generated hydrogen radical is supplied to a portion to be cleaned via a pipe and a flow-rate adjusting shutter.
However, the cleaning apparatus has the following problem. Specifically, an oxide on a catalyst surface evaporates when the catalyst is heated, and the evaporated oxide adheres to an inner wall of a supply path such as the pipe. The oxide that adheres to the inner wall reacts with the hydrogen radical, causing deactivation of the hydrogen radical. Water generated by the reaction then oxidizes the catalyst again.
This phenomenon is referred to as a Water Vapor Cycle (Langmuir Cycle). For example, when tungsten W is used as a catalyst, the following reactions occur:
WOx+2H (hydrogen radical)→H2O+W
When these reactions are repeated, supply efficiency of the hydrogen radical decreases because the hydrogen radical is continuously deactivated. The decreased supply efficiency of the hydrogen radical leads to a longer period of time necessary for cleaning. For example, in the case of the lithography apparatus, productivity (throughput) is reduced.
The present invention is directed to a cleaning apparatus for cleaning an object by supplying a hydrogen radical to the object, which can reduce adhesion of an oxide to an inner wall of a supply path of the hydrogen radical.
According to an aspect of the present invention, a cleaning apparatus for cleaning an object by supplying a hydrogen radical to the object includes a generation unit configured to generate the hydrogen radical by supplying gas to a heated catalyst, a limitation unit configured to limit supply of gas from the generation unit to the object, and an exhaust unit configured to exhaust gas around the catalyst without passing it through the object in a state where the supply of the gas is limited by the limitation unit.
Further features and aspects of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to explain the principles of the invention.
Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings.
The catalyst 1 enables generation of a hydrogen radical by reaction with the gas from the supply unit 3. The catalyst 1 contains, for example, at least one of tungsten, platinum, tantalum, molybdenum, nickel, and rhenium.
The supply unit 3 is configured to supply, to the catalyst 1, a gas that can generate a hydrogen radical by reaction with the catalyst 1. The supply unit 3 can also be configured to supply, to the catalyst 1, a reducing gas that can reduce an oxide of the catalyst 1. In this case, the supply unit 3 is only required to selectively supply two gases.
The gas that can generate the hydrogen radical by reaction with the catalyst 1 contains, for example, at least one of hydrogen and ammonia. The reducing gas contains, for example, at least one of a hydrogen radical, ethanol, carbon monoxide, methane, and propane. The gas from the supply unit 3 is advisably supplied to the vicinity of the catalyst 1.
The heating unit can heat the catalyst 1, and contains, for example, a power source for supplying a current to the catalyst 1. The “heating” includes a form of causing the catalyst itself to generate heat.
The cleaning apparatus 27 includes a shutter 7 (limitation unit) that can limit supplying of gas from around the catalyst 1 to the object 11, and an exhaust unit 5 that can exhaust the gas around the catalyst 1 without passing it through the object 11 in the gas-supply limited state by the shutter 7. The shutter 7 can be driven by a driving mechanism (not illustrated). A known technology can be applied to the driving mechanism. The limitation unit can be a gate valve.
The “gas-supply limited state by the shutter” includes not only a state where the shutter 7 completely blocks supplying of the gas but also a state where the shutter 7 limits supplying of the gas by reducing conductance of a gas supply path including the housing 21 and the pipe 9. Hereinafter, the case where the shutter 7 completely blocks supply of the gas is described. However, the present invention is not limited to this case.
In the present exemplary embodiment, the shutter 7 is arranged in the housing 21. However, the location of the shutter 7 is not limited to this. The shutter 7 is only required to be arranged between the catalyst 1 and the object 11. When arranged in the supply path 9, the shutter 7 is advisably arranged as close as possible to the catalyst 1.
The exhaust unit 5 is only required to exhaust the gas around the catalyst 1 without passing it through the object 11. For example, the exhaust unit 5 is arranged on a catalyst side with respect to the shutter 7.
In addition to the configuration described above at least a part of the supply unit 3, the exhaust unit 5, the pipe 9, the shutter 7, and the inner wall of the housing 21 can be made of a material that can suppress deactivation of the hydrogen radical. For example, a material such as SiO2 where an annihilation probability of the hydrogen radical is 0.2 or less is applied. The annihilation probability of 0.2 of the hydrogen radical means that hydrogen atoms are annihilated by 90% when the hydrogen atoms collide with a surface of the material ten times.
A cleaning method using the cleaning apparatus is described.
The former cleaning method is described. First, in step S10, the shutter 7 is closed. In step S20, the exhaust unit 5 starts exhaust of gas in the housing 21. This results in removal of gas present in the housing 21 and able to oxidize the catalyst 1.
In step S30, the supply unit 3 starts supplying of gas into the housing 21. As the gas to be supplied, for example, hydrogen is used. In step S40, the heating unit starts heating of the catalyst 1. In this housing, tungsten as the catalyst 1 is heated to 1100° C. to 2000° C.
An oxide (tungsten oxide) present on a surface of the tungsten starts to evaporate at 1100° C. or more, and hence the evaporated oxide is exhausted via the exhaust unit 5. In other words, the oxide can be prevented from adhering to an inner wall of the pipe 9. Oxidation of the tungsten can also be suppressed because H2O able to oxidize the tungsten is exhausted.
Timing of steps S10 to S40 can arbitrarily be changed. The timing is only required to enable exhaust of the evaporated oxide.
Through steps S10 to S40, before a hydrogen radical is supplied to the object 11 to clean it, the supply unit 3 supplies hydrogen in the closed state of the shutter 7, and the exhaust unit 5 exhausts gas. After a passage of a predetermined period of time, in step S50, the supplying of gas by the supply unit 3 is stopped. This step can be omitted.
In step S60, the exhaust of the gas by the exhaust unit 5 is stopped. This step is executed to prevent the hydrogen radical generated during the cleaning from being exhausted without heading toward the object 11. Step S60 can be executed simultaneously with or after the start of the cleaning.
The processing then proceeds to cleaning of the object by the hydrogen radical. In step S70, the supply unit 3 starts supplying of hydrogen. In this case, the tungsten as the catalyst 1 is heated to 1600° C. or more. The oxide on the tungsten surface has been removed in steps S10 to S40, hence the oxide can be prevented from evaporating from the tungsten surface and adhering to the inner wall of the supply path such as the pipe 9.
In step S80, the shutter 7 is opened to supply the generated hydrogen radical to the object 11, thereby performing cleaning.
After a predetermined period of time for the cleaning passes, the shutter 7 is closed to stop the supplying of the hydrogen radical, thereby completing the cleaning. When the hydrogen radical is continuously supplied to the object 11 on a steady basis, the cleaning can be stopped according to a cleaning stop command.
The latter cleaning method is described. First, in step S10, the shutter 7 is closed.
In step S20, the exhaust unit 5 starts exhaust of gas in the housing 21. This results in removal of gas present in the housing 21 which can oxidize the catalyst 1.
In step S30, the supply unit 3 starts supplying of gas into the housing 21. As the gas to be supplied, gas (reducing gas) that can reduce the oxide of the catalyst 1 is used. As such a gas, for example, gas containing at least one of a hydrogen radical, ethanol, carbon monoxide, methane, and propane is used. In step S40, the heating unit starts heating of the catalyst 1. In this case, tungsten as the catalyst 1 can be heated to 1100° C. or less.
Step S20 can be executed simultaneously with or after step S30.
Through steps S10 to S40, before a hydrogen radical is supplied to the object 11 to clean it, the supply unit 3 supplies the hydrogen radical in a state where the shutter 7 is closed, and the exhaust unit 5 exhausts gas. After a predetermined period of time for reducing the oxide + of the catalyst 1 passes, in step S50, the supplying of the gas by the supply unit 3 is stopped. This step is executed to prevent the hydrogen radical generated during the cleaning and the reducing gas from mixing to damage the object 11. When damage by the reducing gas is sufficiently small which can be permitted, this step can be omitted.
In step S60, the exhaust of the gas by the exhaust unit 5 is stopped. This step is executed to prevent the hydrogen radical generated during the cleaning from being exhausted without heading toward the object 11. Step S60 can be executed simultaneously with or after the start of the cleaning.
The processing then proceeds to cleaning of the object by the hydrogen radical. In step S70, the supply unit 3 starts supplying of hydrogen. In this case, the tungsten as the catalyst 1 is heated to 1600° C. or more. The oxide on the tungsten surface has been removed in steps S10 to S40, and hence the oxide can be prevented from evaporating from the tungsten surface and adhering to the inner wall of the supply path such as the pipe 9.
In step S80, the shutter 7 is opened to supply the generated hydrogen radical to the object 11, thereby performing cleaning.
After a predetermined period of time for the cleaning passes, the shutter 7 is closed to stop the supplying of the hydrogen radical, thereby completing the cleaning. When the hydrogen radical is continuously supplied to the object 11 on a steady basis, the cleaning can be stopped according to a cleaning stop command.
As a first modified example, in addition to the components described above, the cleaning apparatus 27 can include an inner wall heating unit that heats a part of the supply unit 3, the exhaust unit 5, the pipe 9, the shutter 7, and the housing 21.
When the oxide on the surface of the catalyst 1 evaporates, a part of the oxide may adhere to the inner wall of the housing 21 without being exhausted. In the present modified example, heating the inner wall to a high temperature by the inner wall heating units 23 prevents adhesion of the oxide, thereby suppressing deactivation of the hydrogen radical when the hydrogen radical collides with the inner wall.
While gas is supplied to the heated catalyst in the closed state of the shutter 7 and the exhaust unit 5 exhausts gas, the inner wall heating units 23 can heat the housing 21. However, timing of heating by the inner wall heating units 23 is not limited to this. The inner wall heating units 23 can perform heating during cleaning of the object 11.
As a second modified example, in addition to the configuration of the first modified example, the cleaning apparatus 27 can include a cooling unit that cools the shutter 7.
In the present modified example, the shutter 7 is configured to retract from the supply path of the hydrogen radical. While gas is supplied to the heated catalyst in the closed state of the shutter 7 and the exhaust unit 5 exhausts gas, the cooling unit 25 can cool the shutter 7. Retracting the shutter 7 during cleaning of the object 11 prevents reduction of supply efficiency of the hydrogen radical caused by the oxide that has adhered to the shutter 7. The shutter 7 is not required to completely retract from a space including the supply path. It suffices that the shutter 7 can be driven in a manner that a surface of the shutter 7 to which the oxide has adhered does not face the space including the supply path.
A cleaning method using the cleaning apparatus according to the modified example is described.
In the present modified example, in step S11, cooling of the shutter is started. Timing of step S11 is not limited to that illustrated in
In step S12, the inner wall heating units 23 start heating of the inner wall of the housing. Timing of step S12 is not limited to that illustrated in
The second exemplary embodiment is different from the first exemplary embodiment in that a supply unit 3 includes a hydrogen radical generation unit 28 configured to supply a hydrogen radical. The hydrogen radical generation unit 28 can be similar in configuration to the hydrogen radical generation unit of the first exemplary embodiment.
The hydrogen radical generation unit 28 includes a housing 22, a catalyst 2 arranged in the housing 22, a supply unit 4 that supplies gas to the catalyst 2, and a heating unit (not illustrated) that heats the catalyst 2. The cleaning apparatus 28 includes a shutter 8 (limitation unit) that can limit supply of a hydrogen radical to the supply unit 3, and an exhaust unit 6 that can exhaust gas around the catalyst 2 without passing it through a supply unit 3 when the shutter 8 limits the supply. A detailed configuration of these components is similar to that of the hydrogen radical generation unit of the first exemplary embodiment and description thereof is omitted.
A method of generating a hydrogen radical by the hydrogen radial generation unit 28 is similar to that of the first exemplary embodiment described above with reference to
As an example, the cleaning apparatus is applied to a pattern transfer apparatus. The pattern transfer apparatus transfers a pattern to a substrate. The pattern transfer apparatus generally uses a particle beam such as light or an electron beam. The above cleaning apparatus is suitably used for a cleaning apparatus of an optical member that can control the particle beam. As an example, the cleaning apparatus is applied to an illumination optical unit or a projection optical unit of an EUV exposure device that uses extreme ultraviolet light having a wavelength of about 13 nanometers to transfer a pattern.
The light source unit includes a laser 35, a light emitting medium 61, and a condensing mirror 60. The light emitting medium 61 is irradiated with a laser beam from the laser 35 to extract the extreme ultraviolet light. The extracted ultraviolet light is condensed by the condensing mirror 60. The extreme ultraviolet light from the condensing mirror 60 is reflected by a multilayer film mirror 64 that serves as the illumination optical unit, and guided to the reticle 66.
The extreme ultraviolet light reflected on the surface of the reticle 66 is reflected by a multilayer film mirror 65 that serves as the projection optical unit, and guided to a wafer 30. The projection optical unit functions to project the pattern on the reticle onto the wafer in a reduced form.
In the EUV exposure device, a foreign object may adhere to the multilayer film mirror included in the illumination optical unit or the projection optical unit. Such a foreign object is, for example, carbon, which is caused by outgas discharged from the member included in the EUV exposure device or a carbon compound discharged from a resist (photosensitizing agent) applied on the wafer. Adhesion of the foreign object causes reduction of a reflectance ratio of the extreme ultraviolet light.
In the present exemplary embodiment, the EUV exposure device includes the cleaning apparatus 27. A hydrogen radical is supplied from the cleaning apparatus 27 to the multilayer film mirror, and reacts with the foreign object. As a result, the foreign object can be removed.
According to the present exemplary embodiment, a period of time for cleaning can be shortened, and thus productivity (throughput) of the pattern transfer apparatus can be enhanced.
An example of a device manufacturing method that uses pattern transfer is described. As such a device, for example, a semiconductor device or a liquid crystal display device is manufactured. The semiconductor device is manufactured through a front-end process of fabricating an integrated circuit on the wafer and a back-end process of completing, as a product, the integrated circuit chip fabricated on the wafer in the front-end process. The front-end process includes a process of exposing the wafer on which the photosensitizing agent has been applied by the exposure device, and a process of developing the wafer. The back-end process includes an assembly process (dicing and bonding) and a packaging process (sealing). The liquid crystal display device is manufactured through a process of fabricating a transparent electrode. The process of fabricating the transparent electrode includes a process of applying a photosensitizing agent on a glass substrate on which a transparent conductive film has been deposited, a process of exposing the glass substrate on which the photosensitizing agent has been applied by the exposure device, and a process of developing the glass substrate. According to the present exemplary embodiment, the device manufacturing method enables manufacturing of a device higher in quality than a conventional one.
According to the present invention, in the cleaning apparatus that cleans the object by supplying the hydrogen radical to the object, adhesion of an oxide to the inner wall of the supply path of the hydrogen radical can be reduced.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures, and functions.
This application claims priority from Japanese Patent Application No. 2010-102521 filed Apr. 27, 2010, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-102521 | Apr 2010 | JP | national |
