Method and apparatus for controlling droplet in extreme ultraviolet light source

A lithography method in semiconductor fabrication, comprising:

• generating a plurality of first drops of a target material through a first nozzle group selected from a plurality of nozzles to form a first elongated droplet, wherein an actuator is driven to generate one of the first drops for a first time period;
• generating a first laser pulse to convert the first elongated droplet into a first plasma that generates a first extreme ultraviolet (EUV) radiation;
• reflecting the first EUV radiation by a collector mirror having an optical axis;
• and
• generating a plurality of second drops of the target material through a second nozzle group selected from the plurality of nozzles to form a second elongated droplet, wherein the second elongated droplet is oblique with the optical axis of the collector mirror at a different angle than the first elongated droplet, and the actuator is driven to generate one of the second drops for a second time period, and the second time period is different than the first time period, wherein the first nozzle group includes a plurality of first nozzles arranged along a first direction, and the second nozzle group includes a plurality of second nozzles arranged along a second direction that is oblique or offset from the first direction.

A lithography method in semiconductor fabrication, comprising:

• generating a plurality of first drops of a target material through a first nozzle group selected from a plurality of nozzles to form a first elongated droplet, wherein an actuator is driven to generate a first one of the first drops for a first time period, and the first one, a second one, and a third one of the first drops are generated sequentially through a first one, a second one, and a third one of the nozzles of the first nozzle group;
• generating a first laser pulse to convert the first elongated droplet into a first plasma that generates a first extreme ultraviolet (EUV) radiation;
• reflecting the first EUV radiation by a collector mirror;
• and
• generating a plurality of second drops of the target material through a second nozzle group selected from the plurality of nozzles to form a second elongated droplet, wherein the actuator is driven to generate one of the second drops for a second time period, and the second time period is different than the first time period, and wherein a longitudinal axis of the second elongated droplet is oblique to a longitudinal axis of the first elongated droplet.