Patent Application
20120175533
1. Technical Field
This disclosure relates to an extreme ultraviolet (EUV) light source apparatus, a method for controlling the extreme ultraviolet light source apparatus, and a recording medium with a program of the method recorded thereon.
2. Related Art
In recent years, as semiconductor production processes become capable of producing semiconductor devices with increasingly fine feature sizes, as photolithography has been making rapid progress toward finer fabrication. In the next generation, microfabrication of semiconductor devices with sizes of 60 nm to 45 nm, and further, feature sizes of 32 nm and finer will be required. Accordingly, in order to meet the demand for microfabrication at 32 nm and finer, an exposure apparatus is needed in which a system for generating EUV light at a wavelength of approximately 13 nm is combined with a reduced projection reflective optical system.
Three kinds of systems for generating EUV light are generally known, including Laser Produced Plasma (LLP) type system in which plasma is generated by irradiating a target material with a laser beam, a Discharge Produced Plasma (DPP) type system in which plasma is generated by electric discharge is used, and an Synchrotron Radiation (SR) type system in which orbital radiation is used to generate plasma.
An extreme ultraviolet light source apparatus according to one aspect of this disclosure, having a laser apparatus configured to irradiate a target material, wherein the target material is turned into plasma and emits extreme ultraviolet light. The apparatus may include a burst control unit configured to control irradiation of the target material with the laser beam which is outputted successively in pulses from the laser apparatus, such that upon irradiation of the target material, the extreme ultraviolet light is emitted successively in pulses, and wherein the burst control unit is configured to prevent extreme ultraviolet light from being emitted from the target material by preventing the laser beam from irradiating the target material when the successive pulsed emission is paused.
A method according to another aspect of this disclosure for controlling a light source apparatus in which a target material is irradiated with a laser beam from a laser apparatus and the target material is turned into plasma and which emits extreme ultraviolet light may include: irradiating the target material with the laser beam outputted from the laser apparatus successively in pulses such that the extreme ultraviolet light is emitted successively in pulses; and preventing the laser beam from irradiating the target material, thereby preventing the target material from being turned into plasma by the laser beam while the laser beam is outputted from the laser apparatus successively in pulses when the successively pulsed emission is paused.
A recording medium according to yet another aspect of this disclosure with a program recorded thereon for controlling a light source apparatus in which a target material is irradiated with a laser beam from a laser apparatus and the target material is turned into plasma and which emits extreme ultraviolet light may include a program which causes the light source apparatus to control irradiation of the target material with the laser beam outputted successively in pulses from the laser apparatus such that the extreme ultraviolet light is emitted successively in pulses upon irradiation of the target material, and prevent extreme ultraviolet light from being emitted from the target material by preventing the laser beam from irradiating the target material when the successive pulsed emission is paused.
Hereinafter, selected embodiments for implementing the present disclosure will be described in detail with reference to the accompanying drawings. In the subsequent description, each drawing merely illustrates shape, size, positional relationship, and so on, schematically to the extent that each drawing enables the content of this disclosure to be understood. The present disclosure is not limited to the shape, the size, the positional relationship, and so on, illustrated in each drawing. In certain instances, part of hatching along a section is omitted in the drawings in order to show the configuration clearly. Further, numerical values indicated hereafter are merely preferred examples of the present disclosure; thus, the present disclosure is not limited to the indicated numerical values.
A first embodiment of the present disclosure is described below in detail with reference to the drawings. In the description to follow, an LPP type EUV light source apparatus will be illustrated as an example, but without being limited thereto, the embodiment may also be applied to a DPP type EUV light source apparatus or to an SR type light source apparatus. In the first embodiment, a case in which a target material is turned into plasma with single-stage laser irradiation will be illustrated as an example, but without being limited thereto, the configuration may be such that the target material is turned into plasma with multiple-stage laser irradiation, for example. Further, the first embodiment may be applied to a laser apparatus, a laser processing apparatus, and so forth.
In the present disclosure, the term “successive light emission operation (period)” may refer to an operation (period) in which EUV light is emitted successively; the term “successive light emission pause operation (period)” may refer to an operation (period) in which emission of the EUV light is paused; and the term “burst operation (period)” may refer to an operation (period) in which the successive light emission operation and the successive light emission pause operation alternate with each other.
In the configuration shown in
A focusing mirror M2, which may be an off-axis paraboloidal mirror, and the EUV collector mirror M3 having a through-hole provided at substantially the center thereof may be provided in the EUV chamber 10. The focusing mirror M2 may reflect the pulse laser beam L1 incident thereon via the window W1 with high reflectance. The pulse laser beam L1 reflected with high reflectance may pass through the through-hole in the EUV collector mirror M3 and be focused in a plasma generation site P10. The focusing mirror M2 may be disposed outside the EUV chamber 10. In this case, the pulse laser beam L1 reflected by the optical system including the mirror M1, for example, may be reflected by the focusing mirror M2, may then pass through the window W1 and the through-hole in the EUV collector mirror M3, and may be focused in the plasma generation site P10.
A target supply unit 11 for supplying the target material in the form of a droplet 13 may be provided in the EUV chamber 10. For example, the target supply unit 11 may be configured to output the droplet 13 to the plasma generation site P10 in the EUV chamber 10. The target supply unit 11 may control timing at which and/or a direction to which the droplet 13 is outputted so that the droplet 13 may be irradiated with the pulse laser beam L1 in the plasma generation site P10. Without being limited thereto, however, the driver laser 1 may control timing at which and/or a direction to which the pulse laser beam L1 is outputted so that the pulse laser beam L1 may be focused on the droplet 13 in the plasma generation site P10. The target material may be supplied into the EUV chamber 10 in the form of a solid target, such as a wire, a ribbon, a disc, and so forth, without being limited to the form of the droplet. In this case, the EUV chamber 10 may preferably be provided with a mechanism for rotating the wire, the ribbon, the disc, and so forth, periodically or on-demand.
When the target material is Sn, the light L may be emitted radially from plasma generated as the target material is irradiated with the pulse laser beam L1, and the light L may include EUV light L10 at a wavelength of for example, approximately 13.5 nm. Of the light L emitted from the plasma, the EUV light L10 may be selectively reflected by the EUV collector mirror M3, as described above. The reflected EUV light L10 may be focused at a pinhole PH such that an image of the EUV light L10 may be transferred at the pinhole PH. Thereafter, the EUV light L10 may pass through the pinhole PH and be outputted to the exposure apparatus 20.
A beam dump LDP1 for absorbing a laser beam that has passed the plasma generation site P10 may be provided on an extension along a beam path of the pulse laser beam L1. A target collection unit DP1 for collecting the target material that has not been turned into plasma may be provided on an extension along a trajectory of the droplet 13.
An EUV light source controller C may be configured to control the EUV light source apparatus 100. The EUV light source controller C may be configured to control oscillation and/or amplification by the driver laser 1 via for example a laser controller C2. The EUV light source controller C, for example, may be configured to cause the laser controller C2 to output an oscillation timing control signal S2 to the oscillator 2 to thereby control the oscillation timing of the pulse laser beam L1. Further, the EUV light source controller C may be configured to output a target generation signal S4 to the target supply unit 11 to thereby control output of the droplet 13. In addition, the EUV light source controller C may be configured to control a posture of the focusing mirror M2 via a mirror controller C3 to thereby control a location at which the laser beam may be focused by the focusing mirror M2.
An imaging unit 12 may capture an image around the plasma generation site P10. Information based on the image captured by the imaging unit 12 may be inputted to the EUV light source controller C. Alternatively, the information may be inputted to the mirror controller C3. The information may contain, for example, timing at which and a trajectory along which the droplet 13 passes the plasma generation site P10, the plasma generated in the plasma generation site P10, and so forth, in the form of an image and an imaging time thereof. Based on the information from the imaging unit 12, the EUV light source controller C or the mirror controller C3 may output a mirror actuation control signal S3 to a mirror actuator M2a to control the posture of the focusing mirror M2 such that the pulse laser beam L1 may be focused in the plasma generation site P10. Further, based on the information from the imaging unit 12, the EUV light source controller C may control timing at which the droplet 13 is outputted from the target supply unit 11 and the timing at which the pulse laser beam L1 is outputted from the driver laser 1 so that the droplet 13 may be irradiated with the pulse laser beam L1 in the plasma generation site P10.
The EUV light source controller C may include a burst control unit C1. The burst control unit C1 may perform burst control processing in which the EUV light L10 is emitted in bursts based on a burst emission instruction signal S1 from the exposure apparatus 20. Here, emission in burst means emission in a burst operation. In the burst operation, a period in which the EUV light L10 is successively emitted in pulses at a constant rate (successive light emission period) and a period in which emission of the EUV light 10 is paused (successive light emission pause period) alternate with each other. The exposure apparatus 20 may perform exposure processing using averaged energy of the EUV light L10 emitted in bursts.
In the first embodiment, the burst control unit C1 may be configured to control timing at which the driver laser 1 outputs the pulse laser beam L1 (oscillation timing) so that the droplet 13 is irradiated with the pulse laser beam L1, during the successive light emission period of the burst operation. Meanwhile, during the successive light emission pause period, the burst control unit C1 may modify the oscillation timing control signal S2 to thereby cause the oscillation timing of the pulse laser beam L1 to be shifted. In a state in which the oscillation timing of the pulse laser beam L1 is shifted, the droplet 13 is not irradiated with the pulse laser beam L1; thus, generation of the light L containing the EUV light L10 may be paused.
That is, as shown in
Here, referring to a timing chart shown in
Thereafter, the burst control unit C1 of the EUV light source controller C may determine whether or not a successive light emission period T2 is occurring at a given moment (Step S104). If the successive light emission period T2 is occurring (Step S104, Yes), the burst control unit C1 may output to the oscillator 2 the oscillation timing control signal S2 which may cause the pulse laser beam L1 to be oscillated at the oscillation trigger timing determined in Step S103 (Step S105). With this, the droplet 13 may be irradiated with the pulse laser beam L1 outputted from the driver laser 1, whereby the EUV light L10 may be generated.
Meanwhile, if the successive light emission period T2 is not occurring (Step S104, No), that is, if a successive light emission pause period T1 is occurring, the burst control unit C1 may delay the oscillation trigger timing determined in Step S103 by the period Δt1, for example (Step S106: see (d) in
Thereafter, the EUV light source controller C may determine whether or not a burst light emission indication signal S1 indicating completion of exposure is inputted from the exposure apparatus 20 (Step S107). If the exposure is not complete (Step S107, No), the processing may return to Step S102 and continue with the above-described burst operation. If the exposure is complete (Step S107, Yes), the EUV light source controller C may stop generation of the droplet 13 (Step S108), and the processing may be terminated.
As in the first embodiment, when generation of the EUV light L10 is paused by shifting the oscillation timing of the pulse laser beam L1 during the successive light emission pause period T1, the following advantages may be expected:
1. Damage to an optical element, such as the EUV collector mirror M3 in the EUV chamber 10, may be reduced. As a result, the lifetime of the EUV light source apparatus may be extended.
2. Since the driver laser 1 is in the successive light emission operation during the burst operation, the optical system of the driver laser 1 may be thermally stabilized. With this, the droplet 13 may be irradiated with the pulse laser beam L1 at a stable location with stable energy. As a result, stable EUV light L10 may be emitted.
3. Since the driver laser 1 is in the successive light emission operation during the burst operation, the heat load variation in the driver laser 1 may be reduced. With this, damage to the optical element or the like used in the driver laser 1 caused by the heat load variation may be reduced. As a result, lifetime of the optical element may be extended.
When the oscillation of the pulse laser beam L1 is paused during the successive light emission pause period T1, the following problems with the driver laser 1 may occur in some cases:
1. Sudden heat load variation may occur to an optical element or the like at the start of the successive light emission period T2.
2. Sudden heat load variation may also occur when a duty ratio between the successive light emission period T2 and the successive light emission pause period T1 is modified.
3. Resulting from the above, a focusing condition of the pulse laser beam L1 may become unstable, or the following capability in the energy control may deteriorate. As a result, stable EUV light may not be obtained.
In the first embodiment, however, the pulse laser beam L1 may be oscillated continuously during the burst operation, which may make it possible to stabilize the focusing condition of the pulse laser beam L1 during the successive light emission period T2, and to improve the following capability in the energy control. As a result, the EUV light emission control may be performed with stability.
In the above-described first embodiment, generation of the EUV light L10 may be paused by shifting the oscillation timing of the pulse laser beam L1 while the pulse laser beam L1 is oscillated continuously. Without being limited thereto, however, generation of the EUV light L10 may be paused by shifting a beam axis of the pulse laser beam L1, for example, while the pulse laser beam L1 is oscillated continuously. Hereinafter, this case will be described as a first modification of the first embodiment.
As shown in
Shifting of the beam axis of the pulse laser beam L1 may be achieved by, as shown in
As shown in (c) of
Here, referring to a flowchart shown in
Thereafter, the burst control unit C1 of the EUV light source controller C may determine whether or not the successive light emission period T2 is occurring at a given moment (Step S204). If the successive light emission period T2 is occurring (Step S204, Yes), the burst control unit C1 may determine whether or not the beam axis CI of the pulse laser beam L1 is shifted at that moment (Step S205). Then, when the beam axis of the pulse laser beam L1 is shifted to the beam axis CIa (Step S205, No), the burst control unit C1 may shift back the beam axis CIa of the laser pulse beam (Step S206), and thereafter output to the oscillator 2 the oscillation timing control signal S2 for causing the pulse laser beam L1 to be oscillated at the oscillation trigger timing determined in Step S203 (Step S209). With this, the droplet 13 may be irradiated with the pulse laser beam L1 outputted from the driver laser 1, whereby the EUV light L10 may be generated.
Meanwhile, if the successive light emission period T2 is not occurring (Step S204, No), that is, if the successive light emission pause period T1 is occurring, the burst control unit C1 may determine whether or not the beam axis of the pulse laser beam L1 is shifted at a given moment (Step S207). Then, when the beam axis of the pulse laser beam L1 in not shifted (Step S207, No), the burst control unit C1 may cause the beam axis of the pulse laser beam L1 to be shifted to the beam axis CIa (Step S208), and then may output to the oscillator 2 the oscillation timing control signal S2 for causing the pulse laser beam L1 to be oscillated at the oscillation trigger timing determined in Step S203 (Step S209). With this, the droplet 13 may not be irradiated with the pulse laser beam L1 outputted from the driver laser 1, whereby generation of the EUV light L10 may be paused.
Subsequently, the EUV light source controller C may determine whether or not the burst light emission indication signal S1 indicating completion of the exposure has been inputted from the exposure apparatus 20 (Step S210). If the exposure is not complete (Step S210, No), the processing may return to Step S202, and the above-described burst operation may be continued. Meanwhile, if the exposure is complete (Step S210, Yes), the EUV light source controller C may stop the generation of the droplet 13 (Step S211), and the processing may be terminated.
In the first modification of the first embodiment, generation of the EUV light L10 may be paused by shifting the beam axis of the pulse laser beam L1 during the successive light emission pause period T1, whereby the following advantages may be expected in some cases:
1. Damage to an optical element such as the EUV collector mirror M3 in the EUV chamber 10 may be reduced. As a result, the lifetime of the EUV light source apparatus may be extended.
2. Since the driver laser 1 may be in the successive light emission operation during the burst operation, the optical system in the driver laser 1 may be thermally stable. With this, the droplet 13 may be irradiated with the pulse laser beam L1 at a stable location with stable energy. As a result, stable EUV light L10 may be emitted.
3. Since the driver laser 1 may be in the successive light emission operation during the burst operation, the heat load variation of the driver laser 1 may be reduced. With this, damage to the optical element or the like used in the driver laser 1 caused by the heat load variation may be reduced. As a result, the lifetime of the optical element may be extended.
Generation of the EUV light L10 may be paused by shifting a focus of the pulse laser beam L1 while the pulse laser beam L1 is oscillated continuously. Hereinafter, this case will be described as a second modification of the first embodiment.
As shown in
Shifting of the focus of the pulse laser beam L1 may be achieved by, as shown in
As shown in (c) of
Here, referring to a flowchart shown in
Thereafter, the burst control unit C1 of the EUV light source controller C may determine whether or not the successive light emission period T2 is occurring at a given moment (Step S304). If the successive light emission period T2 is occurring (Step S304, Yes), the burst control unit C1 may determine whether or not the focus of the pulse laser beam L1 is shifted at that moment (Step S305). Then, when the focus of the pulse laser beam L1 is shifted to the focus F1a (Step S305, No), the burst control unit C1 may shift the focus F1a of the pulse laser beam L1 back to the focus F1 (Step S306), and thereafter output to the oscillator 2 the oscillation timing control signal S2 for causing the pulse laser beam L1 to be oscillated at the oscillation trigger timing determined in Step S303 (Step S309). With this, the droplet 13 may be irradiated with the pulse laser beam L1 outputted from the driver laser 1, whereby the EUV light L10 may be generated.
Meanwhile, if the successive light emission period T2 is not occurring (Step S304, No), that is, if the successive light emission pause period T1 is occurring, the burst control unit C1 may determine whether or not the focus of the pulse laser beam L1 is shifted at that moment (Step S307). Then, when the focus of the pulse laser beam L1 is not shifted (Step S307, No), the burst control unit C1 may cause the focus of the pulse laser beam L1 to be shifted to the focus F1a (Step S308), and thereafter output to the oscillator 2 the oscillation timing control signal S2 for causing the pulse laser beam L1 to be oscillated at the oscillation trigger timing determined in Step S303 (Step S309). With this, the droplet 13 may not be turned into plasma even when being irradiated with the pulse laser beam L1, whereby generation of the EUV light L10 may be paused.
Thereafter, the EUV light source controller C may determine whether or not the burst light emission indication signal S1 indicating completion of the exposure has been inputted from the exposure apparatus 20 (Step S310). If the exposure is not complete (Step S310, No), the processing may return to Step S302 and the above-described burst operation may be continued. Meanwhile, if the exposure is complete (Step S310, Yes), the EUV light source controller C may stop generation of the droplet 13 (Step S311), and the process may be terminated.
In the second modification of the first embodiment, generation of the EUV light L10 may be paused by shifting the focus of the pulse laser beam L1 during the successive light emission pause period T1, whereby the following advantages may be expected in some cases:
1. Damage to an optical element such as the EUV collector mirror M3 in the EUV chamber 10 may be reduced. As a result, the lifetime of the EUV light source apparatus may be extended.
2. Since the driver laser 1 may be in the successive light emission operation during the burst operation, the optical system in the driver laser 1 may be thermally stable. With this, the droplet 13 may be irradiated with the pulse laser beam L1 at a stable location with stable energy. As a result, stable EUV light L10 may be emitted.
3. Since the driver laser 1 may be in the successive light emission operation during the burst operation, the heat load variation of the driver laser 1 may be reduced. With this, damage to the optical element or the like used in the driver laser 1 caused by the heat load variation may be reduced. As a result, the lifetime of the optical element may be extended.
A second embodiment of the present disclosure is described below in detail with reference to the drawings. In the second embodiment, a case in which the target material may be turned into plasma with two-stage laser irradiation will be illustrated as an example. Note that the second embodiment may also be applied to a laser apparatus, a laser processing apparatus, and so forth.
Here, the pre-plasma may be plasma with low electron temperature and/or low electron density, neutral particles, or a mixed state of the neutral particles and the plasma with low electron temperature and/or low electron density, which have been generated from a surface of a collection of the target material, such as the droplet 13. A target in this pre-plasma PP state may be irradiated with the pulse laser beam L1, whereby the target may be turned into plasma with relatively high electron temperature and/or relatively high electron density. It is known that a relatively large amount of EUV light may be obtained from the plasma with relatively high electron temperature and/or relatively high electron density. That is, the pre-plasma may be further heated by the laser pulse beam, whereby the EUV light L10 may be generated with high conversion efficiency (CE).
Here, as shown in
Note that in place of the pre-plasma PP, a fragmented material (fragment) group of the target material generated by crushing the droplet 13 may be used to generate the plasma. For generating the fragmented material (fragment) group of the target material, a pulse laser beam with a lower pulse energy than the pre-pulse laser beam LP for generating the pre-plasma may be used for the pre-pulse laser beam LP. As shown in
In the second embodiment, under the control by the EUV light source controller C, the laser controller C2 may control oscillation of the pre-pulse laser 30. At this time, as shown in
For example, in the case of the pre-plasma irradiation, if it is during the successive light emission period T2 in
Meanwhile, if it is during the successive light emission pause period T1, the pre-pulse laser beam oscillation trigger may not be generated; therefore, the pre-plasma PP may not be generated (see (b) and (c) of
Here, the burst control processing according to the second embodiment will be described in detail with reference to a flowchart shown in
Thereafter, the burst control unit C1 of the EUV light source controller C may determine whether or not the successive light emission period T2 is occurring at a given moment (Step S404). If the successive light emission period T2 is occurring (Step S404, Yes), the burst control unit C1 may cause the pre-pulse laser beam LP to be oscillated (Step S405), and then cause the pulse laser beam L1 to be oscillated (Step S406). With this, the droplet 13 may be irradiated with the pre-pulse laser beam LP, and the pre-plasma PP may be generated; then, the pre-plasma PP may be irradiated with the pulse laser beam L1, and the EUV light L10 may be generated.
Meanwhile, if the successive light emission period T2 is not occurring (Step S404, No), that is, if the successive light emission pause period T1 is occurring, the pre-pulse laser beam LP may not be oscillated, and only the pulse laser beam L1 may be oscillated (Step S406). With this, the EUV light L10 may not be generated.
Thereafter, the EUV light source controller C may determine whether or not the burst light emission indication signal S1 indicating completion of exposure has been inputted from the exposure apparatus 20 (Step S407). If the exposure is not complete (Step S407, No), the processing may return to Step S402 and the above-described burst operation may be continued. If the exposure is complete (Step S407, Yes), the EUV light source controller C may stop generation of the droplet 13 (Step S408), and the processing may be terminated.
In Second embodiment, generation of the EUV light L10 may be paused by stopping oscillation of the pre-pulse laser beam LP during the successive light emission pause period T1 of the burst oscillation period, whereby the following advantages may be expected in some cases:
1. Damage to an optical element such as the EUV collector mirror M3 in the EUV chamber 10 may be reduced. As a result, the lifetime of the EUV light source apparatus may be extended.
2. Since the driver laser 1 may be in the successive light emission operation during the burst operation, the optical system in the driver laser 1 may be thermally stable. With this, the droplet 13 may be irradiated with the pulse laser beam L1 at a stable location with stable energy. As a result, stable EUV light L10 may be emitted.
3. Since the driver laser 1 may be in the successive light emission operation during the burst operation, the heat load variation of the driver laser 1 may be reduced. With this, damage to the optical element or the like used in the driver laser 1 caused by the heat load variation may be reduced. As a result, the lifetime of the optical element may be extended.
In the above-described second embodiment, generation of the EUV light L10 may be paused by stopping oscillation of the pre-pulse laser beam LP. Without being limited thereto, however, as in the pulse laser beam L1 in the first embodiment, generation of the EUV light L10 may be paused by shifting the oscillation timing of the pre-pulse laser beam LP (see
As shown in (b) of
Here, the burst control processing according to the first modification of the second embodiment will be described in detail with reference to a flowchart shown in
Thereafter, the burst control unit C1 of the EUV light source controller C may determine whether or not the successive light emission period T2 is occurring at a given moment (Step S504). If the successive light emission period T2 is occurring (Step S504, Yes), the burst control unit C1 may cause the pre-pulse laser beam LP to continue being oscillated (Step S505), and then cause the pulse laser beam L1 to be oscillated (Step S506). With this, the pre-plasma PP generated by being irradiated with the pre-pulse laser beam LP may be irradiated with the pulse laser beam L1, whereby the EUV light L10 may be generated.
Meanwhile, if the successive light emission period T2 is not occurring (Step S504, No), that is, if a successive light emission pause period T1 is occurring, the oscillation timing of the pre-pulse laser beam LP may be shifted (Step S507), and thereafter the pre-pulse laser beam LP may be oscillated (Step S505), and the pulse laser beam L1 may be oscillated (Step S506). In this case, although both the pre-pulse laser beam LP and the pulse laser beam L1 may be oscillated, the EUV light L10 may not be emitted.
Thereafter, the EUV light source controller C may determine whether or not the burst light emission indication signal S1 indicating completion of the exposure has been inputted from the exposure apparatus 20 (Step S508). If the exposure is not complete (Step S508, No), the processing may return to Step S502 and the above-described burst operation may be continued. If the exposure is complete (Step S508, Yes), the EUV light source controller C may stop generation of the droplet 13 (Step S509), and the processing may be terminated.
In the first modification of the second embodiment, generation of the EUV light L10 may be paused by shifting the oscillation timing of the pre-pulse laser beam LP during the successive light emission pause period T1, whereby the following advantages may be expected in some cases:
1. Damage to an optical element such as the EUV collector mirror M3 in the EUV chamber 10 may be reduced. As a result, the lifetime of the EUV light source apparatus may be extended.
2. Since the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation during the burst operation, the optical systems in the driver laser 1 and in the pre-pulse laser 30 may be thermally stable. A stable pulse laser beam L1 and a stable pre-pulse laser beam LP are outputted, and stable EUV light L10 may be emitted.
3. Since the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation during the burst operation, the heat load variation of the driver laser 1 and of the pre-pulse laser 30 may be reduced. With this, damage to the optical elements or the like used in the driver laser 1 and in the pre-pulse laser 30 caused by the heat load variation may be reduced. As a result, the lifetime of the optical elements may be extended.
In the first modification of the second embodiment, generation of the EUV light L10 may be paused by shifting the oscillation timing of the pre-pulse laser beam LP while the pre-pulse laser beam LP and the pulse laser beam L1 may be oscillated continuously. In a second modification of the second embodiment, as in the pulse laser beam L1 in the first modification of the first embodiment, a beam axis CI1 of the pre-pulse laser beam LP may be shifted to a beam axis CI1a (see
As shown in (c) of
The burst control processing according to the second modification of the second embodiment will be described in detail below with reference to a flowchart shown in
Thereafter, the burst control unit C1 of the EUV light source controller C may determine whether or not the successive light emission period T2 is occurring at a given moment (Step S604). If the successive light emission period T2 is occurring (Step S604, Yes), the burst control unit C1 may determine whether or not the beam axis of the pre-pulse laser beam LP is shifted at that moment (Step S605). Then, when the beam axis of the pre-pulse laser beam LP is shifted to the beam axis CI1a (Step S605, No), the burst control unit C1 may shift the beam axis of the pre-pulse laser beam LP back to the beam axis CI1 (Step S606), and thereafter cause the pre-pulse laser beam LP to be oscillated at the oscillation trigger timing determined in Step S603 (Step S609) and cause the pulse laser beam L1 to be oscillated (Step S610). With this, the droplet 13 may be irradiated with the pre-pulse laser beam LP, whereby the pre-plasma PP may be generated, and the pre-plasma PP may be irradiated with the pulse laser beam L1, whereby the EUV light L10 may be generated.
Meanwhile, if the successive light emission period T2 is not occurring (Step S604, No), that is, if the successive light emission pause period T1 is occurring, the burst control unit C1 may determine whether or not the beam axis of the pre-pulse laser beam LP is shifted at a given moment (Step S607). Then, when the beam axis of the pre-pulse laser beam LP is not shifted (Step S607, No), the burst control unit C1 may cause the beam axis of the pre-pulse laser beam LP to be shifted (Step S608), and thereafter cause the pre-pulse laser beam LP to be oscillated at the oscillation trigger timing determined in Step S603 (Step S609) and the pulse laser beam L1 to be oscillated (Step S610). In this case, the droplet 13 may not be irradiated with the pre-pulse laser beam LP outputted from the pre-pulse laser 30, whereby generation of the EUV light L10 may be paused.
Thereafter, the EUV light source controller C may determine whether or not the burst light emission indication signal S1 indicating completion of the exposure has been inputted from the exposure apparatus 20 (Step S611). If the exposure is not complete (Step S611, No), the processing may return to Step S602 and the above-described burst operation may be continued. If the exposure is complete (Step S611, Yes), the EUV light source controller C may stop generation of the droplet 13 (Step S612), and the processing may be terminated.
In the second modification of the second embodiment, generation of the EUV light L10 may be paused by shifting the beam axis of the pre-pulse laser beam LP during the successive light emission pause period T1, whereby the following advantages may be expected in some cases:
1. Damage to an optical element such as the EUV collector mirror M3 in the EUV chamber 10 may be reduced. As a result, the lifetime of the EUV light source apparatus may be extended.
2. Since the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation during the burst operation, the optical systems of the driver laser 1 and of the pre-pulse laser 30 may be thermally stable. A stable pulse laser beam L1 and a stable pre-pulse laser beam LP are outputted, and stable EUV light L10 may be emitted.
3. Since the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation during the burst operation, the heat load variation in the driver laser 1 and in the pre-pulse laser 30 may be reduced. With this, damage to the optical elements or the like used in the driver laser 1 and in the pre-pulse laser 30 caused by the heat load variation may be reduced. As a result, the lifetime of the optical elements may be extended.
As in the pulse laser beam L1 according to the second modification of the first embodiment, generation of the EUV light L10 may be paused by shifting a focus F10 of the pre-pulse laser beam LP to a focus F10a (see
As shown in (c) of
The burst control processing according to the third modification of the second embodiment will be described in detail below with reference to a flowchart shown in
Thereafter, the burst control unit C1 of the EUV light source controller C may determine whether or not the successive light emission period T2 is occurring at a given moment (Step S704). If the successive light emission period T2 is occurring (Step S704, Yes), the burst control unit C1 may determine whether or not the focus of the pre-pulse laser beam LP is shifted at that moment (Step S705). Then, when the focus of the pre-pulse laser beam LP is shifted to the focus F10a (Step S705, No), the burst control unit C1 may shift the focus of the pre-pulse laser beam LP back to the focus F10 (Step S706), and thereafter cause the pre-pulse laser beam LP to be oscillated at the oscillation trigger timing determined in Step S703 (Step S709) and the pulse laser beam L1 to be oscillated (Step S710). With this, the droplet 13 may be irradiated with the pre-pulse laser beam LP, whereby the pre-plasma PP may be generated, and the pre-plasma PP may be irradiated with the pulse laser beam L1, whereby the EUV light L10 may be generated.
Meanwhile, if the successive light emission period T2 is not occurring (Step S704, No), that is, if the successive light emission pause period T1 is occurring, the burst control unit C1 may determine whether or not the focus of the pre-pulse laser beam LP is shifted at that moment (Step S707). Then, when the focus of the pre-pulse laser beam LP is not shifted (Step S707, No), the burst control unit C1 may cause the focus of the pre-pulse laser beam LP to be shifted to the focus F10a (Step S708), and thereafter cause the pre-pulse laser beam LP to be oscillated at the oscillation trigger timing determined in Step S703 (Step S709) and the pulse laser beam L1 to be oscillated (Step S710). In this case, the droplet 13 may not be turned into the pre-plasma by being irradiated with the pre-pulse laser beam LP, whereby generation of the EUV light L10 may be paused.
Thereafter, the EUV light source controller C may determine whether or not the burst light emission indication signal S1 indicating completion of the exposure has been inputted from the exposure apparatus 20 (Step S711). If the exposure is not complete (Step S711, No), the processing may return to Step S702 and the above-described burst operation may be continued. If the exposure is complete (Step S711, Yes), the EUV light source controller C may stop generation of the droplet 13 (Step S712), and the processing may be terminated.
In the third modification of the second embodiment, generation of the EUV light L10 may be paused by shifting the focus of the pre-pulse laser beam LP during the successive light emission pause period T1, whereby the following advantages may be expected in some cases:
1. Damage to an optical element such as the EUV collector mirror M3 in the EUV chamber 10 may be reduced. As a result, the lifetime of the EUV light source apparatus may be extended.
2. Since the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation during the burst operation, the optical systems of the driver laser 1 and of the pre-pulse laser 30 may be thermally stable. A stable pulse laser beam L1 and a stable pre-pulse laser beam LP may be outputted, and stable EUV light L10 may be emitted.
3. Since the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation during the burst operation, the heat load variation in the driver laser 1 and in the pre-pulse laser 30 may be reduced. With this, damage to the optical elements or the like used in the driver laser 1 and in the pre-pulse laser 30 caused by the heat load variation may be reduced. As a result, lifetime of the optical elements may be extended.
In the second embodiment and the modifications thereof, burst-emission of the EUV light L10 may be achieved by controlling the pre-pulse laser beam LP. However, the present disclosure is not limited to the second embodiment and the modifications thereof. For example, burst-emission of the EUV light L10 may be achieved by shifting oscillation timing of both the pre-pulse laser beam LP and the pulse laser beam L1, by shifting the beam axes of both the pre-pulse laser beam LP and the pulse laser beam L1, or by shifting the foci of both the pre-pulse laser beam LP and the pulse laser beam L1. These methods may be effective when the foci of the pre-pulse laser beam LP and of the pulse laser beam L1 substantially coincide with each other. For example, when the droplet serving as the target is mass-limited (approximately 10 μm in diameter), the extent of the target material diffused by being irradiated with the pre-pulse laser beam LP may be close to the original position of the droplet. In this case, even when the pre-pulse laser beam LP is controlled so that the droplet may not be irradiated therewith, the droplet may be irradiated with the pulse laser beam L1; thus, the burst control may be difficult. In such a case, burst-emission of the EUV light L10 may be achieved by performing the above-mentioned simultaneous control.
An example of an EUV light source apparatus in which a pre-pulse laser beam LP and a pulse laser beam L1 may strike a droplet 13 coaxially and foci of the pre-pulse laser beam LP and of the pulse laser beam L1 may be made to substantially coincide with each other, as mentioned above, is shown in
In the EUV light source apparatus 200D shown in
When the pre-pulse laser beam LP and the pulse laser beam L1 strike the droplet 13 substantially coaxially, the focusing mirror M2 can be used as the focusing mirror common to both laser beams. As a result, simplification and size-reduction of the apparatus may be facilitated, and further, the beam axes or the foci of the pre-pulse laser beam LP and of the pulse laser beam L1 may be shifted simultaneously only by operating the focusing mirror M2. The control of the focusing mirror M2 may be carried out, for example, by a mirror actuation control signal S3a outputted from the mirror controller C3.
Next, a third embodiment of this disclosure will be described. In the third embodiment, as in the second embodiment, an EUV light source apparatus, in which the pre-pulse laser beam LP may be oscillated by the pre-pulse laser 30 and the generated pre-plasma PP may be irradiated with the pulse laser beam L1, may generate EUV light L10. In the third embodiment, in such EUV light source apparatus, generation of the EUV light L10 may be paused by stopping output of the droplet 13 during the successive light emission pause period T1 in a state in which the driver laser 1 and the pre-pulse laser 30 are in the successive light emission operation during the burst operation. Note that the third embodiment, as in the first embodiment, may be applied to an EUV light source apparatus in which the pre-pulse laser beam LP is not employed.
In the third embodiment, as shown in
In the third embodiment, the burst control unit C1 of the EUV light source controller C may output the target generation signal S4 to the target supply unit 11 to thereby control supply of the droplet 13. In particular, the burst control unit C1 may control an output period and an output pause period of the droplet 13 (see
In the third embodiment, generation of the EUV light L10 may be paused by stopping output of the droplet 13 during the successive light emission pause period T1, whereby the following advantages may be expected in some cases:
1. Damage to an optical element such as the EUV collector mirror M3 in the EUV chamber 10 may be reduced. As a result, the lifetime of the EUV light source apparatus may be extended.
2. Since the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation during the burst operation, the optical systems in the driver laser 1 and in the pre-pulse laser 30 may be thermally stable. A stable pulse laser beam L1 and a stable pre-pulse laser beam LP may be outputted and stable EUV light L10 may be emitted.
3. Since the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation during the burst operation, the heat load variation in the driver laser 1 and in the pre-pulse laser 30 may be reduced. With this, damage to the optical elements or the like used in the driver laser 1 and in the pre-pulse laser 30 caused by the heat load variation may be reduced. As a result, lifetime of the optical elements may be extended.
4. Since the droplet may not be outputted during the successive light emission pause period T1, the amount of the target material to be consumed may be reduced.
In the above-described third embodiment, generation of the EUV light L10 may be paused by stopping output of the droplet 13. However, without being limited thereto, generation of the EUV light L10 may be paused by shifting the generation timing of the droplet 13 while the pre-pulse laser beam LP and the pulse laser beam L1 may be oscillated continuously. Hereinafter, this case will be described as a first modification of the third embodiment.
As shown in
In (a) of
In the first modification of the third embodiment, generation of the EUV light L10 may be paused by shifting the output timing of the droplet 13 during the successive light emission pause period T1, whereby the following advantages may be expected in some cases:
1. Damage to an optical element such as the EUV collector mirror M3 in the EUV chamber 10 may be reduced. As a result, the lifetime of the EUV light source apparatus may be extended.
2. Since the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation during the burst operation, the optical systems of the driver laser 1 and of the pre-pulse laser 30 may be thermally stable. A stable pulse laser beam L1 and a stable pre-pulse laser beam LP may be outputted and stable EUV light L10 may be emitted.
3. Since the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation during the burst operation, the heat load variation in the driver laser 1 and in the pre-pulse laser 30 may be reduced. With this, damage to the optical elements or the like used in the driver laser 1 and in the pre-pulse laser 30 caused by the heat load variation may be reduced. As a result, the lifetime of the optical elements may be extended.
The droplet 13 may be prevented from being irradiated with the pre-pulse laser beam LP by being accelerated or decelerated after it is outputted, whereby generation of the EUV light L10 may be paused. Hereinafter, a third modification of the third embodiment will be described.
In an EUV light source apparatus 300A shown in
For example, as shown in
With this, emission of the EUV light L10 may be paused during the successive light emission pause period T1 while the driver laser 1 and the pre-pulse laser 30 are in the successive light emission operation.
As shown in
Alternatively, the charging electrode voltage application signal S7 may continually be in the ON state, and the acceleration electric field application signal S8 may be in the ON state during the successive light emission period T2 and in an OFF state during the successive light emission pause period T1. In this case, the charged droplet 13 may be decelerated during the successive light emission pause period T1. Alternatively, the acceleration electric field application signal S8 may continually be in the ON state, and the charging electrode voltage application signal S7 may be in the ON state during the successive light emission period T2 and in the OFF state during the successive light emission pause period T1. In this case, compared to the droplet 13 during the successive light emission period T2, the droplet 13 during the successive light emission pause period T1 may be decelerated. At this time, the acceleration electric field application signal S8 may be in the OFF state during the successive light emission pause period T1. That is, the charging electrode voltage application signal S7 and the acceleration electric field application signal S8 may be in the ON state during the successive light emission period T2 and in the OFF state during the successive light emission pause period T1. In this case, compared to the droplet 13 during the successive light emission period T2, the droplet 13 during the successive light emission pause period T1 may be decelerated.
Summarizing these, six control patterns a1 through a6 shown in
Further, the acceleration/deceleration controller C5 may be configured to apply a deceleration voltage application signal in place of the acceleration electric field application signal S8 to the acceleration/deceleration mechanism 50 to decelerate a charged target.
In a third modification of the third embodiment, the trajectory of the charged droplet 13 may be shifted, whereby the droplet 13 is prevented from being irradiated with the pre-pulse laser beam LP.
In an exemplary EUV light source apparatus 300C shown in
For example, as shown in
In the third modification of the third embodiment, emission of the EUV light L10 may be paused during the successive light emission pause period T1 while the driver laser 1 and the pre-pulse laser 30 may be in the successive light emission operation.
As shown in
Further, in the above-described third modification of the third embodiment, the charged droplet 13 may be deflected during the successive light emission pause period T1, whereby the trajectory thereof may be shifted. However, without being limited thereto, as shown in
Such deflection of the trajectory of the droplet 13 may be achieved by, as shown in
Alternatively, as shown in
Summarizing these, six control patterns b1 through b6 shown in
Here, as in an EUV light source apparatus 300D according to a fourth modification of the third embodiment shown in
The charging electrode 40, the acceleration/deceleration mechanism 50, and the deflection mechanism 60 may be configured as separate units from the target supply unit 11 or integrated, in part or in the entirety thereof, with the target supply unit 11.
Further, in the above-described third embodiment and the modifications thereof, a method in which the output port of the target supply unit 11 is successively opened or closed in a predetermined cycle using a piezoelectric element, whereby the droplet 13 is outputted successively. However, without being limited thereto, a so-called drop-on-demand method may be adopted in which output of the droplet 13 may be started or stopped at a desired timing. In the drop-on-demand method, an output charging electrode, which may be turned ON/OFF, may be provided to the output port of the target supply unit 11. In such a case, the droplet 13 may be pulled out through the output port and outputted by electrostatic force generated as the output charging electrode is turned ON.
In particular, a target supply mechanism in which the drop-on-demand method may be employed may have the configuration shown in
The target supply unit 11 may be filled with liquid metal, such as molten Sn, serving as the target material. Here, as pulsed positive high voltage is applied to the output charging electrode 41, the liquid metal may be pulled out as the droplet 13 by the electrostatic force. At this time, the droplet 13 may be positively charged. In this way, the output charging electrode 41 may also function as the charging electrode 40 of
Note that the EUV chamber 10 may be grounded so as not to influence the trajectory of the outputted droplet 13. Further, the target supply unit 11 and the EUV chamber 10 are connected to each other with an insulating material 42 therebetween. This is because the droplet 13 may return toward the target supply unit 11 after being outputted therefrom if the vicinity of the connection part between the target supply unit 11 and the EUV chamber 10 are grounded.
In this case, when the droplet 13 is outputted, the droplet 13 may be always charged by the output charging electrode 41. Thus, the deflection control according to the above-mentioned control pattern a1 or a4 may be adopted.
It should be noted that the above-described first through third embodiments and the modifications thereof may be appropriately combined. For example, an embodiment or a modification in which the pre-pulse laser beam LP is used may be applied to an embodiment or a modification in which only the pulse laser beam L1 is used.
Further, various controllers (EUV light source controller C including burst control unit C1, laser controller C2, mirror controller C3, and so forth) of the above-described embodiments and the modifications thereof may be achieved, for example, using an information processing device 1000 as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-177063 | Jul 2009 | JP | national |
The present application is a continuation of PCT/JP2010/062854 filed Jul. 29, 2010, which claims priority from Japanese Patent Application No. 2009-177063 filed Jul. 29, 2009.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2010/062854 | Jul 2010 | US |
| Child | 13349355 | US |
