Embodiments described herein relate generally to an extreme ultraviolet radiation exposure apparatus and a method of lithography thereby.
Research and development on an extreme ultraviolet (EUV) radiation exposure apparatus and method of lithography thereby using ultra-short wavelength of 13.5 nanometers as a next-generation exposure technology has been promoted for manufacturing post-22-nanometer-generation advanced semiconductor device. Because this EUV radiation exposure technology enables a semiconductor device with extremely narrow line-width, the technology is regarded as “ultimate exposure technology”.
Conventionally, because a vacuum chamber of an EUV radiation exposure apparatus is kept vacuous, the EUV radiation exposure apparatus for performing EUV lithography has a problem of contamination by carbon against optical elements such as an EUV-light reflecting mirror which is used in reduced projection lithography. When a wafer covered with photoresist is introduced into the vacuum chamber of the apparatus and EUV light radiates the wafer to form a pattern of the photoresist, solvent remained in the apparatus evaporates or resin constituting the photoresist is decomposed or desorbed, so that degas including organic compounds is emitted in the vacuum chamber. The degas including organic compounds is easy to be charged and adheres to surfaces as foreign substances because the vacuum chamber of the EUV radiation exposure apparatus is vacuous. Accordingly, a technique that uses hydrogen (hydrogen radicals) to clean the foreign substances in the vacuum chamber of the EUV radiation exposure apparatus is disclosed.
In general, according to one embodiment, an EUV radiation exposure apparatus includes a vacuum chamber, an EUV radiation exposing light source installed in the vacuum chamber, and an ionizer that generates positive or negative ions.
Exemplary embodiments of an EUV radiation exposure apparatus will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the following embodiments.
When EUV light from an EUV radiation exposure head 20 is radiated to a photoresist R1 on a surface of a wafer 10, the EUV radiation exposure apparatus according to the embodiment of the present invention radiates ionizer light by an ionizer 40 to degas including organic compounds, which is generated after the EUV light radiation, to neutralize charged degas. As shown in
That is, the EUV radiation exposure apparatus according to the embodiment of the present invention includes the EUV radiation exposure head 20 for exposing photoresist R1 that is arranged to face the wafer 10 to which the photoresist R1 is coated, the ionizer 40 that is attached to the EUV radiation exposure head 20 and has two ion generation ports 40a and 40b on both side surfaces thereof, respectively, and the chamber 30 that houses these elements therein. The inside of the chamber 30 is kept at a desired degree of vacuum by a vacuum suction device 31. The ionizer 40 is installed in the vacuum chamber and is driven in conjunction with driving of the EUV radiation exposure head 20 and generates positive or negative ions. Polarity of the ions applied by the ionizer 40 is determined according to a type of the photoresist R1.
By moving the mask 23 and the wafer stage S in the mask moving direction DM and the wafer-stage moving direction DW, respectively, exposure is sequentially performed, the photoresist R1 in an exposure area 11 reacts due to exposure energy of the exposure light L1, and a latent image pattern is formed, as shown by a top view of the wafer 10 in an exposure process in
The ionizer 40 has the ion generation ports 40a and 40b, which are arranged on opposite side surfaces on upstream and downstream sides of the EUV radiation exposure head 20, respectively, in the mask moving direction DM and the wafer-stage moving direction DW as shown in
The ionizer 40 having a radiation wavelength range from 115 nanometers to 400 nanometers, and an operation temperature range from 10° C. to 40° C. (a storage temperature range from 0° C. to 60° C.) and a humidity equal to or lower than 80% (a storage humidity range equal to or lower than 85%) in the case of an air cooling method by a cooling fan was used. A window material thereof was MgF2. An input voltage thereof was AC 100 volts to 240 volts.
The EUV radiation exposing light source 21 is attached to the EUV radiation exposure head 20 that is formed to be capable of relatively moving with respect to the wafer 10, and the ionizer 40 is also fixed to the EUV radiation exposure head 20. This configuration realizes elimination of charges at an appropriate position with respect to an exposure position without the need of alignment.
In this case, the EUV radiation exposing light source having a luminescence peak near a wavelength of 13.5 nanometers, power from 10 watts to 120 watts, and a frequency about from 2 kHz to 10 kHz is used.
The ionizer 40 is activated or deactivated according to the activation and deactivation of the EUV radiation exposing light source 21. The ionizer 40 can be activated or deactivated with a delay time according to the activation and deactivation of the EUV radiation exposing light source 21. With this configuration, elimination of charges from degas can be realized immediately after generation of the degas due to exposure and a state where the degas is difficult to reattach to the apparatus can be obtained.
In the embodiment mentioned above, as ionizer light, that is, electron beams obtained from the ionizer 40, electron beams of a wavelength of 160 nanometers are used. However, electron beams of a wavelength from 115 nanometers to 400 nanometers can be used. Preferably, electron beams of a wavelength from 150 nanometers to 180 nanometers can be used. When the electron beams of a wavelength from 115 nanometers to 400 nanometers are used, the photoresist for EUV radiation exposure does not react thereto and thus there is no influence on pattern formation even when ionizer light is radiated to the photoresist. Particularly when electron beams of a wavelength from 150 nanometers to 180 nanometers are used, charges can be eliminated efficiently.
For example, a polymer bound PAG resist or a resist using a polyhydroxystyrene (PHS) or acrylic base resin is used as the photoresist R1. In this case, the film thickness of the photoresist R1 is set from 30 nanometers to 60 nanometers.
A method of lithography using the EUV radiation exposure apparatus is explained next.
As shown in
In this case, the wafer 10 to which a polymer bound PAG resist is applied in a film thickness of about 50 nanometers using a spinner and which is prebaked at a temperature from 80° C. to 120° C. for about 1 minute is used.
As shown in
Regarding turn-on and turn-off of the EUV radiation exposing light source 21 of the EUV radiation exposure head 20 and turn-on and turn-off of the ionizer 40, the timing charts show driving states of the EUV radiation exposing light source of the EUV radiation exposure head and the ionizer in the lithography method according to the present embodiment in
While elimination of charges by the ionizer 40 was performed in this way, the degree of vacuum in the chamber was changed and a relation between the degree of vacuum and the charge elimination time was measured. The obtained result is shown in
A relation between the charge elimination time and the distance between a light-source output window and a charged plate in a case where the degree of vacuum in the chamber was fixed to 0.01 Pascal and the distance was increased was also measured. The obtained result is shown in
According to the first embodiment, when EUV light radiation is performed to the photoresist R1 applied onto the surface of the wafer 10 using the EUV radiation exposure head 20, soft X-ray radiation using the ionizer 40 is always performed to degas including organic compounds generated after the EUV light radiation. As shown by the timing chart of
As explained above, soft X-ray radiation is performed by the ionizer 40 to degas including organic compounds that is generated from the photoresist R1 after EUV light radiation in the EUV radiation exposure apparatus, thereby eliminating charges to suppress attachment of generated degas onto the photoresist and to the inside of the apparatus. As a result, an effect that the use amount of hydrogen to be used for cleaning can be reduced by suppressing attachment of the degas to the inside of the apparatus can be obtained. Particularly when the apparatus is used in high vacuum, the apparatus is easily charged and contamination of the optical elements is serious. However, with the configuration according to the present embodiment, elimination of charges can be performed quite easily and contamination is suppressed. Therefore, the configuration is particularly effective for the EUV radiation exposure apparatus according to the present embodiment, which is used in high vacuum.
In the present embodiment, because the ion generation port 40a that is provided on the downstream side of the EUV radiation exposure head 20 among the ion generation ports 40a and 40b of the ionizer 40 is driven, degas generated by exposure can be efficiently subject to charge elimination immediately after generation of the degas. When the wafer stage moves in the opposite direction, the ion generation port 40b provided at the opposite position to the ion generation port 40a is driven to realize efficient charge elimination. When both of the ion generation ports 40a and 40b are driven and charges are eliminated on the upstream and downstream sides of the EUV radiation exposure head, more reliable charge elimination can be performed.
In the EUV radiation exposure apparatus according to the present embodiment, the ion generation ports 40a and 40b of the ionizer 40 are provided on the upstream and downstream sides of the EUV radiation exposure head 20, respectively. Therefore, even when the exposure order, that is, the driving direction of the EUV radiation exposure head 20 is changed, the charge elimination function can be achieved quite easily only by selecting which one of the ion generation ports 40a and 40b is to be driven.
In the EUV radiation exposure apparatus according to the present embodiment, the EUV radiation exposure head 20 is fixed and the mask 23 and the wafer 10 are moved so that the generation position of degas is fixed. Therefore, the vacuum suction device 31 can be installed to achieve the best recovery condition of degas. Alternatively, exposure can be sequentially performed while the EUV radiation exposure head 20 is moved. With this configuration, transport of the wafer can be avoided and thus factors of contamination can be reduced.
While an ionizer is brought into an always-on state in the embodiment described above, ions are radiated in a pulsed manner with a certain time shifted from timings where the EUV radiation exposing light source 21 is turned on as shown by the timing charts showing driving timings of an EUV radiation exposing light source and an ionizer in
According to the present embodiment, because soft X-ray radiation is performed in a pulsed manner, charge elimination is realized more efficiently. A shift time during which the driving timings of the EUV radiation exposing light source and the ionizer are shifted is preferably about one-third to a half of a pulse width after driving of the EUV radiation exposing light source.
For comparison, cross-sectional views schematically illustrating a configuration of an EUV radiation exposure apparatus not using the ionizer and a configuration of a method of lithography by the EUV radiation exposure apparatus are shown in
On the other hand, in the EUV radiation exposure apparatus according to the embodiments of the present invention, when EUV light radiation is performed from the EUV radiation exposure head 20 to the photoresist R1 on the surface of the wafer 10, soft X-ray radiation is performed by the ionizer 40 to degas including organic compounds, which is generated after the EUV light radiation, thereby neutralizing charged degas. With the soft X-ray radiation by the ionizer 40, the degas is neutralized to eliminate charges in the chamber 30 immediately after generation as shown in
As described above, in the EUV radiation exposure apparatus according to the embodiments of the present invention, radiation of EUV light to the photoresist in the EUV radiation exposure apparatus decomposes or desorbs a resin constituting the photoresist, whereby degas including organic compounds is generated. Because the inside of the EUV radiation exposure apparatus is in vacuum, the degas including the organic compounds is easily charged and is attached to various interfaces in the apparatus due to charging, thereby causing contamination. Accordingly, in the above embodiments, the ionizer 40 using vacuum ultraviolet light is mounted on the EUV radiation exposure head 20 to suppress the contamination. By mounting the ionizer 40 on the EUV radiation exposure head 20 in the EUV radiation exposure apparatus, the degas including organic compounds that is generated from the photoresist R1 and is charged after radiation of EUV light is subject to charge elimination at the same time as generation. By the charge elimination, the degas becomes difficult to attach to the interfaces and contamination in the apparatus can be suppressed. Accordingly, the frequency of cleaning in the apparatus can be reduced and the use amount of hydrogen to be used for cleaning can be reduced.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
This application is based upon and claims the benefit of priority from Provisional U.S. Patent Application No. 61/937,098, filed on Feb. 7, 2014; the entire contents of all of which are incorporated herein by reference.
Number | Date | Country | |
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61937098 | Feb 2014 | US |