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公开(公告)号:US06650666B2
公开(公告)日:2003-11-18
申请号:US10027210
申请日:2001-12-21
申请人: Ronald L. Spangler , Robert N. Jacques , John A. Rule , Frederick A. Palenschat , Igor V. Fomenkov , John M. Algots , Jacob P. Lipcon , Richard L. Sandstrom
发明人: Ronald L. Spangler , Robert N. Jacques , John A. Rule , Frederick A. Palenschat , Igor V. Fomenkov , John M. Algots , Jacob P. Lipcon , Richard L. Sandstrom
IPC分类号: H01S310
CPC分类号: G03F7/70575 , G03F7/70025 , G03F7/70041 , G03F7/70333 , G03F7/70933 , H01S3/02 , H01S3/036 , H01S3/038 , H01S3/0385 , H01S3/0404 , H01S3/041 , H01S3/08036 , H01S3/097 , H01S3/0971 , H01S3/0975 , H01S3/104 , H01S3/105 , H01S3/1055 , H01S3/1305 , H01S3/1312 , H01S3/134 , H01S3/137 , H01S3/22 , H01S3/2207 , H01S3/225
摘要: An electric discharge laser with fast wavelength correction. Fast wavelength correction equipment includes at least one piezoelectric drive and a fast wavelength measurement system and fast feedback response times. In a preferred embodiment, equipment is provided to control wavelength on a slow time frame of several milliseconds, on a intermediate time from of about one to five milliseconds and on a very fast time frame of a few microseconds. Preferred techniques include a combination of a relatively slow stepper motor and a very fast piezoelectric driver for tuning the laser wavelength using a tuning mirror. A preferred control technique is described (utilizing a very fast wavelength monitor) to provide the slow and intermediate wavelength control with the combination of a stepper motor and a piezoelectric driver. Very fast wavelength control is provided with a piezoelectric load cell in combination with the piezoelectric driver. Preferred embodiments provide (1) fast feedback control based on wavelength measurements, (2) fast vibration control, (3) active damping using the load cell and an active damping module, (4) transient inversion using feed forward algorithms based on historical burst data. A preferred embodiment adapts the feed forward algorithms to current conditions. Another preferred embodiment measures tuning mirror position to permit wavelength pretuning and active wavelength tuning.
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公开(公告)号:US06853653B2
公开(公告)日:2005-02-08
申请号:US10036925
申请日:2001-12-21
申请人: Ronald L. Spangler , Jacob P. Lipcon , John A. Rule , Robert N. Jacques , Armen Kroyan , Ivan Lalovic , Igor V. Fomenkov , John M. Algots
发明人: Ronald L. Spangler , Jacob P. Lipcon , John A. Rule , Robert N. Jacques , Armen Kroyan , Ivan Lalovic , Igor V. Fomenkov , John M. Algots
IPC分类号: B41C20060101 , B41C1/00 , G03F7/20 , H01L21/027 , H01S3/036 , H01S3/038 , H01S3/04 , H01S3/041 , H01S3/08 , H01S3/081 , H01S3/097 , H01S3/0971 , H01S3/0975 , H01S3/10 , H01S3/102 , H01S3/104 , H01S3/105 , H01S3/1055 , H01S3/11 , H01S3/13 , H01S3/134 , H01S3/137 , H01S3/139 , H01S3/22 , H01S3/223 , H01S3/225 , H01J3/10
CPC分类号: G03F7/70575 , G03F7/70025 , G03F7/70041 , G03F7/70333 , G03F7/70933 , H01S3/036 , H01S3/038 , H01S3/0385 , H01S3/0404 , H01S3/041 , H01S3/08009 , H01S3/08036 , H01S3/0812 , H01S3/097 , H01S3/0971 , H01S3/0975 , H01S3/1024 , H01S3/104 , H01S3/105 , H01S3/1055 , H01S3/13 , H01S3/1305 , H01S3/134 , H01S3/139 , H01S3/22 , H01S3/2207 , H01S3/223 , H01S3/225 , H01S3/2251 , H01S3/2256 , H01S3/2258
摘要: An integrated circuit lithography technique called spectral engineering by Applicants, for bandwidth control of an electric discharge laser. In a preferred process, a computer model is used to model lithographic parameters to determine a desired laser spectrum needed to produce a desired lithographic result. A fast responding tuning mechanism is then used to adjust center wavelength of laser pulses in a burst of pulses to achieve an integrated spectrum for the burst of pulses approximating the desired laser spectrum. The laser beam bandwidth is controlled to produce an effective beam spectrum having at least two spectral peaks in order to produce improved pattern resolution in photo resist film. Line narrowing equipment is provided having at least one piezoelectric drive and a fast bandwidth detection control system having a time response of less than about 2.0 millisecond. In a preferred embodiment, a wavelength tuning mirror is dithered at dither rates of more than 500 dithers per second in phase with the repetition rate of the laser. In one case, the piezoelectric drive was driven with a square wave signal and in a second case it was driven with a sine wave signal. In another embodiment, the maximum displacement was matched on a one-to-one basis with the laser pulses in order to produce a desired average spectrum with two peaks for a series of laser pulses. Other preferred embodiments utilize three separate wavelength tuning positions producing a spectrum with three separate peaks.
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公开(公告)号:US07382815B2
公开(公告)日:2008-06-03
申请号:US10915517
申请日:2004-08-09
申请人: Ronald L. Spangler , Jacob P. Lipcon , John A. Rule , Robert N. Jacques , Armen Kroyan , Ivan Lalovic , Igor V. Fomenkov , John M. Algots
发明人: Ronald L. Spangler , Jacob P. Lipcon , John A. Rule , Robert N. Jacques , Armen Kroyan , Ivan Lalovic , Igor V. Fomenkov , John M. Algots
IPC分类号: H01S5/00
CPC分类号: G03F7/70575 , G03F7/70025 , G03F7/70041 , G03F7/70333 , G03F7/70933 , H01S3/036 , H01S3/038 , H01S3/0385 , H01S3/0404 , H01S3/041 , H01S3/08009 , H01S3/08036 , H01S3/0812 , H01S3/097 , H01S3/0971 , H01S3/0975 , H01S3/1024 , H01S3/104 , H01S3/105 , H01S3/1055 , H01S3/13 , H01S3/1305 , H01S3/134 , H01S3/139 , H01S3/22 , H01S3/2207 , H01S3/223 , H01S3/225 , H01S3/2251 , H01S3/2256 , H01S3/2258
摘要: An integrated circuit lithography technique called spectral engineering by Applicants, for bandwidth control of an electric discharge laser. In a preferred process, a computer model is used to model lithographic parameters to determine a desired laser spectrum needed to produce a desired lithographic result. A fast responding tuning mechanism is then used to adjust center wavelength of laser pulses in a burst of pulses to achieve an integrated spectrum for the burst of pulses approximating the desired laser spectrum. The laser beam bandwidth is controlled to produce an effective beam spectrum having at least two spectral peaks in order to produce improved pattern resolution in photo resist film. Line narrowing equipment is provided having at least one piezoelectric drive and a fast bandwidth detection control system having a time response of less than about 2.0 millisecond. In a preferred embodiment, a wavelength tuning mirror is dithered at dither rates of more than 500 dithers per second in phase with the repetition rate of the laser. In one case, the piezoelectric drive was driven with a square wave signal and in a second case it was driven with a sine wave signal. In another embodiment, the maximum displacement was matched on a one-to-one basis with the laser pulses in order to produce a desired average spectrum with two peaks for a series of laser pulses. Other preferred embodiments utilize three separate wavelength tuning positions producing a spectrum with three separate peaks.
摘要翻译: 一种称为光电工程的集成电路光刻技术,用于放电激光器的带宽控制。 在优选的方法中,使用计算机模型来模拟光刻参数以确定产生所需光刻结果所需的所需激光光谱。 然后使用快速响应的调谐机构来调整脉冲串中的激光脉冲的中心波长,以实现接近所需激光光谱的脉冲串的集成光谱。 控制激光束带宽以产生具有至少两个光谱峰值的有效光束光谱,以便在光致抗蚀剂膜中产生改进的图案分辨率。 提供了具有至少一个压电驱动器和具有小于约2.0毫秒的时间响应的快速带宽检测控制系统的线窄设备。 在优选实施例中,波长调谐镜以与激光器的重复频率相位的每秒超过500次抖动的抖动速率抖动。 在一种情况下,用方波信号驱动压电驱动,在第二种情况下,它是用正弦波信号驱动的。 在另一个实施例中,最大位移与激光脉冲在一对一的基础上匹配,以便为一系列激光脉冲产生具有两个峰值的所需平均光谱。 其它优选实施例利用三个独立的波长调谐位置,产生具有三个独立峰值的光谱。
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公开(公告)号:US07298770B2
公开(公告)日:2007-11-20
申请号:US10912933
申请日:2004-08-05
申请人: Ronald L. Spangler , Jacob P. Lipcon , John A. Rule , Robert N. Jacques , Armen Kroyan , Ivan Lalovic , Igor V. Fomenkov , John M. Algots
发明人: Ronald L. Spangler , Jacob P. Lipcon , John A. Rule , Robert N. Jacques , Armen Kroyan , Ivan Lalovic , Igor V. Fomenkov , John M. Algots
CPC分类号: G03F7/70575 , G03F7/70025 , G03F7/70041 , G03F7/70333 , G03F7/70933 , H01S3/036 , H01S3/038 , H01S3/0385 , H01S3/0404 , H01S3/041 , H01S3/08009 , H01S3/08036 , H01S3/0812 , H01S3/097 , H01S3/0971 , H01S3/0975 , H01S3/1024 , H01S3/104 , H01S3/105 , H01S3/1055 , H01S3/13 , H01S3/1305 , H01S3/134 , H01S3/139 , H01S3/22 , H01S3/2207 , H01S3/223 , H01S3/225 , H01S3/2251 , H01S3/2256 , H01S3/2258
摘要: An integrated circuit lithography technique called spectral engineering by Applicants, for bandwidth control of an electric discharge laser. In a preferred process, a computer model is used to model lithographic parameters to determine a desired laser spectrum needed to produce a desired lithographic result. A fast responding tuning mechanism is then used to adjust center wavelength of laser pulses in a burst of pulses to achieve an integrated spectrum for the burst of pulses approximating the desired laser spectrum. The laser beam bandwidth is controlled to produce an effective beam spectrum having at least two spectral peaks in order to produce improved pattern resolution in photo resist film. Line narrowing equipment is provided having at least one piezoelectric drive and a fast bandwidth detection control system having a time response of less than about 2.0 millisecond. In a preferred embodiment, a wavelength tuning mirror is dithered at dither rates of more than 500 dithers per second in phase with the repetition rate of the laser. In one case, the piezoelectric drive was driven with a square wave signal and in a second case it was driven with a sine wave signal. In another embodiment, the maximum displacement was matched on a one-to-one basis with the laser pulses in order to produce a desired average spectrum with two peaks for a series of laser pulses. Other preferred embodiments utilize three separate wavelength tuning positions producing a spectrum with three separate peaks.
摘要翻译: 一种称为光电工程的集成电路光刻技术,用于放电激光器的带宽控制。 在优选的方法中,使用计算机模型来模拟光刻参数以确定产生所需光刻结果所需的所需激光光谱。 然后使用快速响应的调谐机构来调整脉冲串中的激光脉冲的中心波长,以实现接近所需激光光谱的脉冲串的集成光谱。 控制激光束带宽以产生具有至少两个光谱峰值的有效光束光谱,以便在光致抗蚀剂膜中产生改进的图案分辨率。 提供了具有至少一个压电驱动器和具有小于约2.0毫秒的时间响应的快速带宽检测控制系统的线窄设备。 在优选实施例中,波长调谐镜以与激光器的重复频率相位的每秒超过500次抖动的抖动速率抖动。 在一种情况下,用方波信号驱动压电驱动,在第二种情况下,它是用正弦波信号驱动的。 在另一个实施例中,最大位移与激光脉冲在一对一的基础上匹配,以便为一系列激光脉冲产生具有两个峰值的所需平均光谱。 其它优选实施例利用三个独立的波长调谐位置,产生具有三个独立峰值的光谱。
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公开(公告)号:US06532247B2
公开(公告)日:2003-03-11
申请号:US09794782
申请日:2001-02-27
申请人: Ronald L. Spangler , Robert N. Jacques , George J. Everage , Stuart L. Anderson , Frederick A. Palenschat , Igor V. Fomenkov , Richard L. Sandstrom , William N. Partlo , John M. Algots , Daniel J. W. Brown
发明人: Ronald L. Spangler , Robert N. Jacques , George J. Everage , Stuart L. Anderson , Frederick A. Palenschat , Igor V. Fomenkov , Richard L. Sandstrom , William N. Partlo , John M. Algots , Daniel J. W. Brown
IPC分类号: H01S322
CPC分类号: G03F7/70025 , G03F7/70041 , G03F7/70333 , G03F7/70575 , G03F7/70933 , H01S3/02 , H01S3/036 , H01S3/038 , H01S3/0385 , H01S3/0404 , H01S3/041 , H01S3/08036 , H01S3/097 , H01S3/0971 , H01S3/0975 , H01S3/104 , H01S3/105 , H01S3/1055 , H01S3/1305 , H01S3/1312 , H01S3/134 , H01S3/137 , H01S3/22 , H01S3/2207 , H01S3/225
摘要: An electric discharge laser with fast wavelength correction. Fast wavelength correction equipment includes at least one piezoelectric drive and a fast wavelength measurement system and fast feedback response times. In a preferred embodiment, equipment is provided to control wavelength on a slow time frame of several milliseconds, on a intermediate time from of about one to three millisecond and on a very fast time frame of a few microseconds. Techniques include a combination of a relatively slow stepper motor and a very fast piezoelectric driver for tuning the laser wavelength using a tuning mirror. A preferred control technique is described (utilizing a very fast wavelength monitor) to provide the slow and intermediate wavelength control and a piezoelectric load cell in combination with the piezoelectric driver to provide the very fast (few microseconds) wavelength control.
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公开(公告)号:US20100074295A1
公开(公告)日:2010-03-25
申请号:US12592228
申请日:2009-11-20
申请人: William N. Partlo , Alexander I. Ershov , German Rylov , Igor V. Fomenkov , Daniel J.W. Brown , Christian J. Wittak , Rajasekhar M. Rao , Robert A. Bergstedt , John Fitzgerald , Richard L. Sandstrom , Vladimir B. Fleurov , Robert N. Jacques , Ed Danielewicz , Robin Swain , Edmond Arriola , Mike Wyatt , Walter Crosby
发明人: William N. Partlo , Alexander I. Ershov , German Rylov , Igor V. Fomenkov , Daniel J.W. Brown , Christian J. Wittak , Rajasekhar M. Rao , Robert A. Bergstedt , John Fitzgerald , Richard L. Sandstrom , Vladimir B. Fleurov , Robert N. Jacques , Ed Danielewicz , Robin Swain , Edmond Arriola , Mike Wyatt , Walter Crosby
IPC分类号: H01S3/22
CPC分类号: H01S3/0057 , G03F7/70341 , G03F7/70583
摘要: An apparatus and method are disclosed which may comprise a pulsed gas discharge laser lithography light source which may comprise a seed laser portion providing a seed laser output light beam of seed pulses; an amplifier portion receiving the seed laser output light beam and amplifying the optical intensity of each seed pulse to provide a high power laser system output light beam of output pulses; the amplifier portion may comprise a ring power amplifier comprising amplifier portion injection optics comprising at least one beam expanding prism, a beam reverser and an input/output coupler; the beam expansion optics and the output coupler may be mounted on an optics assembly with the beam expansion optics rigidly mounted with respect to the optics assembly and the input/output coupler mounted for relative movement with respect to the optics assembly for optical alignment purposes.
摘要翻译: 公开了一种可以包括脉冲气体放电激光光刻光源的装置和方法,脉冲气体放电激光光刻光源可以包括提供种子脉冲的种子激光输出光束的种子激光部分; 接收种子激光输出光束并放大每个种子脉冲的光强度的放大器部分,以提供输出脉冲的大功率激光系统输出光束; 放大器部分可以包括环形功率放大器,其包括放大器部分注入光学器件,其包括至少一个光束扩展棱镜,光束反向器和输入/输出耦合器; 光束扩展光学器件和输出耦合器可以安装在光学组件上,其中光束扩展光学器件相对于光学组件刚性地安装,并且输入/输出耦合器被安装成相对于用于光学对准目的的光学组件的相对运动。
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公开(公告)号:US20080197297A1
公开(公告)日:2008-08-21
申请号:US11471434
申请日:2006-06-20
申请人: Robert P. Akins , Richard L. Sandstrom , William N. Partlo , Igor V. Fomenkov , Thomas D. Steiger , John Martin Algots , Norbert Bowering , Robert N. Jacques , Frederick Palenschat , Jun Song
发明人: Robert P. Akins , Richard L. Sandstrom , William N. Partlo , Igor V. Fomenkov , Thomas D. Steiger , John Martin Algots , Norbert Bowering , Robert N. Jacques , Frederick Palenschat , Jun Song
IPC分类号: G01J3/10
CPC分类号: B82Y10/00 , G03F7/70033 , H05G2/003 , H05G2/008
摘要: An EUV light source apparatus and method are disclosed, which may comprise a pulsed laser providing laser pulses at a selected pulse repetition rate focused at a desired target ignition site; a target formation system providing discrete targets at a selected interval coordinated with the laser pulse repetition rate; a target steering system intermediate the target formation system and the desired target ignition site; and a target tracking system providing information about the movement of target between the target formation system and the target steering system, enabling the target steering system to direct the target to the desired target ignition site. The target tracking system may provide information enabling the creation of a laser firing control signal, and may comprise a droplet detector comprising a collimated light source directed to intersect a point on a projected delivery path of the target, having a respective oppositely disposed light detector detecting the passage of the target through the respective point, or a detector comprising a linear array of a plurality of photo-sensitive elements aligned to a coordinate axis, the light from the light source intersecting a projected delivery path of the target, at least one of the which may comprise a plane-intercept detection device. The droplet detectors may comprise a plurality of droplet detectors each operating at a different light frequency, or a camera having a field of view and a two dimensional array of pixels imaging the field of view. The apparatus and method may comprise an electrostatic plasma containment apparatus providing an electric plasma confinement field at or near a target ignition site at the time of ignition, with the target tracking system providing a signal enabling control of the electrostatic plasma containment apparatus. The apparatus and method may comprise a vessel having and intermediate wall with a low pressure trap allowing passage of EUV light and maintaining a differential pressure across the low pressure trap. The apparatus and method may comprise a magnetic plasma confinement mechanism creating a magnetic field in the vicinity of the target ignition site to confine the plasma to the target ignition site, which may be pulsed and may be controlled using outputs from the target tracking system.
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公开(公告)号:US07643528B2
公开(公告)日:2010-01-05
申请号:US11973671
申请日:2007-10-10
申请人: William N. Partlo , Alexander I. Ershov , German Rylov , Igor V. Fomenkov , Daniel J. W. Brown , Christian J. Wittak , Rajasekhar M. Rao , Robert A. Bergstedt , John Fitzgerald , Richard L. Sandstrom , Vladimir B. Fleurov , Robert N. Jacques , Ed Danielewicz , Robin Swain , Edward Arriola , Michael Wyatt , Walter Crosby
发明人: William N. Partlo , Alexander I. Ershov , German Rylov , Igor V. Fomenkov , Daniel J. W. Brown , Christian J. Wittak , Rajasekhar M. Rao , Robert A. Bergstedt , John Fitzgerald , Richard L. Sandstrom , Vladimir B. Fleurov , Robert N. Jacques , Ed Danielewicz , Robin Swain , Edward Arriola , Michael Wyatt , Walter Crosby
IPC分类号: H01S3/22
CPC分类号: H01S3/0057 , G03F7/70341 , G03F7/70583
摘要: An apparatus and method which may comprise a pulsed gas discharge laser which may comprise a seed laser portion; an amplifier portion receiving the seed laser output and amplifying the optical intensity of each seed pulse; a pulse stretcher which may comprise: a first beam splitter operatively connected with the first delay path and a second pulse stretcher operatively connected with the second delay path; a first optical delay path tower containing the first beam splitter; a second optical delay path tower containing the second beam splitter; one of the first and second optical delay paths may comprise: a plurality of mirrors defining the respective optical delay path including mirrors located in the first tower and in the second tower; the other of the first and second optical delay paths may comprise: a plurality of mirrors defining the respective optical delay path including mirrors only in one of the first tower and the second tower.
摘要翻译: 一种可包括可包括种子激光器部分的脉冲气体放电激光器的装置和方法; 接收种子激光输出并放大每个种子脉冲的光强度的放大器部分; 脉冲展开器,其可以包括:与第一延迟路径可操作地连接的第一分束器和与第二延迟路径可操作地连接的第二脉冲展开器; 包含第一分束器的第一光学延迟路径塔; 包含第二分束器的第二光学延迟路径塔; 第一和第二光学延迟路径中的一个可以包括:多个反射镜,其限定相应的光学延迟路径,包括位于第一塔架和第二塔架中的反射镜; 第一和第二光学延迟路径中的另一个可以包括:多个反射镜限定相应的光学延迟路径,其仅包括在第一塔架和第二塔架之一中的镜子。
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公开(公告)号:US20090080476A1
公开(公告)日:2009-03-26
申请号:US11973671
申请日:2007-10-10
申请人: William N. Partlo , Alexander I. Ershov , German Rylov , Igor V. Fomenkov , Daniel J.W. Brown , Christian J. Wittak , Rajasekhar M. Rao , Robert A. Bergstedt , John Fitzgerald , Richard L. Sandstrom , Vladimir B. Fleurov , Robert N. Jacques , Ed Danielewicz , Robin Swain , Edward Arriola , Mike Wyatt , Walter Crosby
发明人: William N. Partlo , Alexander I. Ershov , German Rylov , Igor V. Fomenkov , Daniel J.W. Brown , Christian J. Wittak , Rajasekhar M. Rao , Robert A. Bergstedt , John Fitzgerald , Richard L. Sandstrom , Vladimir B. Fleurov , Robert N. Jacques , Ed Danielewicz , Robin Swain , Edward Arriola , Mike Wyatt , Walter Crosby
CPC分类号: H01S3/0057 , G03F7/70341 , G03F7/70583
摘要: An apparatus and method which may comprise a pulsed gas discharge laser which may comprise a seed laser portion; an amplifier portion receiving the seed laser output and amplifying the optical intensity of each seed pulse; a pulse stretcher which may comprise: a first beam splitter operatively connected with the first delay path and a second pulse stretcher operatively connected with the second delay path; a first optical delay path tower containing the first beam splitter; a second optical delay path tower containing the second beam splitter; one of the first and second optical delay paths may comprise: a plurality of mirrors defining the respective optical delay path including mirrors located in the first tower and in the second tower; the other of the first and second optical delay paths may comprise: a plurality of mirrors defining the respective optical delay path including mirrors only in one of the first tower and the second tower.
摘要翻译: 一种可包括可包括种子激光器部分的脉冲气体放电激光器的装置和方法; 接收种子激光输出并放大每个种子脉冲的光强度的放大器部分; 脉冲展开器,其可以包括:与第一延迟路径可操作地连接的第一分束器和与第二延迟路径可操作地连接的第二脉冲展开器; 包含第一分束器的第一光学延迟路径塔; 包含第二分束器的第二光学延迟路径塔; 第一和第二光学延迟路径中的一个可以包括:多个反射镜,其限定相应的光学延迟路径,包括位于第一塔架和第二塔架中的反射镜; 第一和第二光学延迟路径中的另一个可以包括:多个反射镜限定相应的光学延迟路径,其仅包括在第一塔架和第二塔架之一中的镜子。
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公开(公告)号:US07087914B2
公开(公告)日:2006-08-08
申请号:US10803526
申请日:2004-03-17
申请人: Robert P. Akins , Richard L. Sandstrom , William N. Partlo , Igor V. Fomenkov , John Martin Algots , Robert N. Jacques , Frederick Palenschat , Jun Song
发明人: Robert P. Akins , Richard L. Sandstrom , William N. Partlo , Igor V. Fomenkov , John Martin Algots , Robert N. Jacques , Frederick Palenschat , Jun Song
IPC分类号: H01J35/20
CPC分类号: B82Y10/00 , G03F7/70033 , H05G2/003 , H05G2/008
摘要: An EUV light source apparatus and method are disclosed, which may comprise a pulsed laser providing laser pulses at a selected pulse repetition rate focused at a desired target ignition site; a target formation system providing discrete targets at a selected interval coordinated with the laser pulse repetition rate; a target steering system intermediate the target formation system and the desired target ignition site; and a target tracking system providing information about the movement of target between the target formation system and the target steering system, enabling the target steering system to direct the target to the desired target ignition site. The target tracking system may provide information enabling the creation of a laser firing control signal, and may comprise a droplet detector comprising a collimated light source directed to intersect a point on a projected delivery path of the target, having a respective oppositely disposed light detector detecting the passage of the target through the respective point, or a detector comprising a linear array of a plurality of photo-sensitive elements aligned to a coordinate axis, the light from the light source intersecting a projected delivery path of the target, at least one of the which may comprise a plane-intercept detection device. The droplet detectors may comprise a plurality of droplet detectors each operating at a different light frequency, or a camera having a field of view and a two dimensional array of pixels imaging the field of view. The apparatus and method may comprise an electrostatic plasma containment apparatus providing an electric plasma confinement field at or near a target ignition site at the time of ignition, with the target tracking system providing a signal enabling control of the electrostatic plasma containment apparatus. The apparatus and method may comprise a vessel having and intermediate wall with a low pressure trap allowing passage of EUV light and maintaining a differential pressure across the low pressure trap. The apparatus and method may comprise a magnetic plasma confinement mechanism creating a magnetic field in the vicinity of the target ignition site to confine the plasma to the target ignition site, which may be pulsed and may be controlled using outputs from the target tracking system.
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