Some implementations described herein provide a dual-feedback control system for laser beam targeting in a lithography system such as an EUV lithography system. In addition to using feedback from a high-frequency quad-cell sensor to adjust a target position of the pre-pulse laser beam based on a first portion of a phase of a wavefront of the pre-pulse laser beam, the dual-feedback control system uses feedback from a low-frequency camera sensor to adjust the target position of the pre-pulse laser beam based on a second portion of the phase of the wavefront.

A method for generating secondary radiation includes providing a target material in a target region, and applying a pulse sequence comprising laser pulses to the target material in the target region. Interaction of the target material with the pulse sequence generates secondary radiation. The pulse sequence includes a prepulse and a main pulse trailing the prepulse. A pulse energy of the prepulse is between 2 J und 200 J. A pulse duration of the prepulse is between 200 fs and 5 ps. A pulse energy of the main pulse is between 2 mJ and 50 mJ. A pulse duration of the main pulse is between 15 fs and 300 fs. A pulse time interval between the prepulse and the main pulse is between 1 ps and 1 ns.

An EUV light generation system includes a prepulse laser device outputting prepulse laser light to be radiated to a target supplied into a chamber; a main pulse laser device outputting main pulse laser light to be radiated to a diffusion target generated by the radiation of the prepulse laser light; a first actuator adjusting an irradiation position of the prepulse laser light; a second actuator adjusting an irradiation position of the main pulse laser light; an EUV sensor detecting EUV energy; a laser energy sensor detecting laser energy of the main pulse laser light; a target sensor imaging the diffusion target; and a controller controlling, after controlling the first actuator based on a characteristic value of the diffusion target calculated from an image of the diffusion target, the second actuator so that a ratio of the EUV energy to the laser energy detected by the laser energy sensor becomes large.

A method for generating secondary radiation includes providing a target material in a target region, and applying a pulse sequence of laser pulses to the target material in the target region. Secondary radiation is generated as a result of interaction of the target material with the pulse sequence. The pulse sequence has a pulse train of at least two pre-pulses and a main pulse following the pulse train. A total energy of the pre-pulses of the pulse train is between 0.2 mJ and 10 mJ. A temporal pulse interval between successive pre-pulses of the pulse train is between 50 ps and 500 ns. A pulse energy of the main pulse is between 2 mJ and 50 mJ. A pulse duration of the main pulse is between 15 fs and 300 fs. A temporal pulse interval between the pulse train and the main pulse is between 1 ns and 1 s.

An EUV light generation system includes a prepulse laser device outputting prepulse laser light to be radiated to a target supplied into a chamber; a main pulse laser device outputting main pulse laser light to be radiated to a diffusion target generated by the radiation of the prepulse laser light; a first actuator adjusting an irradiation position of the prepulse laser light; a second actuator adjusting an irradiation position of the main pulse laser light; an EUV sensor detecting EUV energy; a laser energy sensor detecting laser energy of the main pulse laser light; a target sensor imaging the diffusion target; and a controller controlling, after controlling the first actuator based on a characteristic value of the diffusion target calculated from an image of the diffusion target, the second actuator so that a ratio of the EUV energy to the laser energy detected by the laser energy sensor becomes large.

Some implementations described herein provide a dual-feedback control system for laser beam targeting in a lithography system such as an EUV lithography system. In addition to using feedback from a high-frequency quad-cell sensor to adjust a target position of the pre-pulse laser beam based on a first portion of a phase of a wavefront of the pre-pulse laser beam, the dual-feedback control system uses feedback from a low-frequency camera sensor to adjust the target position of the pre-pulse laser beam based on a second portion of the phase of the wavefront.