Target expansion rate control in an extreme ultraviolet light source

An apparatus comprising:

• a chamber that defines an initial target location that receives a first beam of radiation and a target location that receives a second beam of radiation;
• a target material delivery system configured to provide target material to the initial target location, the target material comprising a material that emits extreme ultraviolet (EUV) light when converted to plasma;
• an optical steering system configured to:
• direct a first beam of radiation from an optical source toward the initial target location to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target, and
• direct a second beam of radiation from the optical source toward the target location to convert at least part of the modified target to plasma that emits EUV light;
• a measurement system configured to measure a size of the modified target;
• and
• a control system connected to the target material delivery system, the optical source, the optical steering system, and the measurement system, wherein the control system is configured to:
• receive the measured size from the measurement system;
• analyze the received measured size;
• and
• send one or more signals to the optical source to control an amount of radiant exposure delivered to the target material from the first beam of radiation based on the analysis of the measured size.

A method comprising:

• providing a target material that comprises a component that emits extreme ultraviolet (EUV) light when converted to plasma;
• directing a first beam of radiation toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target;
• directing a second beam of radiation toward the modified target, the second beam of radiation converting at least part of the modified target to plasma that emits EUV light;
• measuring a set of distinct characteristics associated with one or more of the target material and the modified target relative to the first beam of radiation;
• analyzing each of the measured characteristics in the set and determining how the first beam of radiation interacts with the target material to form the modified target based on the combined analysis of each of the measured characteristics;
• and
• controlling an amount of radiant exposure delivered to the target material from the first beam of radiation based on the determination to within a predetermined range of radiant exposures.

An apparatus comprising:

• a chamber that defines an initial target location that receives a first beam of radiation and a target location that receives a second beam of radiation;
• a target material delivery system configured to provide target material to the initial target location, the target material comprising a material that emits extreme ultraviolet (EUV) light when converted to plasma;
• an optical source configured to produce the first beam of radiation and the second beam of radiation;
• an optical steering system configured to:
• direct the first beam of radiation toward the initial target location to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target, and
• direct the second beam of radiation toward the target location to convert at least part of the modified target to plasma that emits EUV light;
• a measurement system that includes a set of measurement sub-systems, each measurement sub-system configured to measure a characteristic associated with one or more of the target material and the modified target relative to the first beam of radiation;
• and
• a control system connected to the target material delivery system, the optical source, the optical steering system, and the measurement system, wherein the control system is configured to:
• receive the measured characteristic from each of the measurement sub-systems of the measurement system;
• analyze the received characteristics;
• and
• send one or more signals to the optical source to control an amount of radiant exposure delivered to the target material from the first beam of radiation based on the analysis of the measured received characteristics.

A method comprising:

• providing a target material that comprises a component that emits extreme ultraviolet (EUV) light when converted to plasma;
• directing a first beam of radiation toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target;
• directing a second beam of radiation toward the modified target, the second beam of radiation converting at least part of the modified target to plasma that emits EUV light;
• measuring one or more characteristics associated with one or more of the target material and the modified target relative to the first beam of radiation;
• analyzing the measured one or more characteristics associated with one or more of the target material and the modified target relative to the first beam of radiation;
• and
• controlling a geometric expansion rate of the modified target based on the analysis of the one or more measured characteristics to thereby increase an amount of EUV light converted from the plasma due to the interaction between the modified target and the second beam of radiation.