Light source for lithography exposure process

A method for generating light in a lithography exposure process, comprising:

• detecting a flow velocity of targets from a fuel target generator at a first detection position and a second detection position;
• adjusting the flow velocity of the targets in response to the detected flow velocity when the detected flow velocity is different from a predetermined value;
• and
• irradiating at least one laser on the targets with a laser generator to generate plasma that emits light;
• wherein the operation of irradiating the at least one laser on the targets comprises:
• irradiating a pre-pulse laser on the targets to expand the targets;
• detecting conditions of expanded targets;
• and
• adjusting a parameter of the laser generator according to the detected flow velocity and the conditions;
• wherein the operation of detecting the flow velocity of the targets comprises:
• projecting a first light curtain and a second light curtain at the first detection position and the second detection position, respectively, on a moving path;
• receiving light reflected from one of the targets when the one of the targets passes through the first detection position and the second detection position;
• measuring a time difference between a time when the light reflected from the target at the first detection position is detected and a time when the light reflected from the target at the second detection position is detected;
• and
• determining a flow velocity of the targets by dividing a distance between the first detection position and the second detection position by the measured time difference.

A method for generating light in a lithography exposure process, comprising:

• measuring a period of time during which one of targets from a fuel target generator passes through two detection positions;
• exciting the targets with a laser generator so as to generate plasma that emits light, wherein the operation of exciting the targets with a laser generator comprises:
• irradiating a pre-pulse laser on the targets to expand the targets;
• detecting length of expanded targets;
• and
• adjusting at least one parameter of the laser generator according to the measured period of time and the length of expanded targets, when the measured period of time is different from a predetermined value, wherein the parameter of the laser generator which is adjusted according to the measured period of time comprises a frequency for generating a laser for illuminating the targets.