Reduce mask defect impact by contamination decompose

A method comprising:

• cleaning a surface of a reticle in a first exposure device by irradiating the surface of the reticle by extreme ultraviolet (EUV) radiation of a first EUV source for an irradiation time;
• irradiating an entire surface of the reticle by an EUV beam at the first exposure device to clean the surface of the reticle;
• focusing a reflected light from the entire surface of the reticle onto an image detector to generate a detected reflected image;
• monitoring the detected reflected image during the irradiation time;
• and
• stopping the cleaning when an increase in each point of the detected reflected image is below a threshold value in a specific amount of time,
• after the cleaning, transferring the reticle from the first exposure device to a second exposure device for lithography operation;
• projecting a layout pattern of the reticle in the second exposure device, using an EUV radiation of a second EUV source onto a photo resist layer of a wafer;
• wherein the reticle is a reflective reticle.

A system comprising:

• a main controller;
• an analyzer module coupled to the main controller;
• a rapid exchange device having an extendable robot arm;
• a first exposure device comprising:
• a first reticle stage for holding a reticle;
• and
• a first EUV light source;
• a second exposure device comprising:
• a second reticle stage;
• a second EUV light source;
• a stage for holding a wafer;
• an imaging device mounted over the stage, wherein in response to a command from the main controller, the imaging device is configured to capture an image of a developed photo resist pattern on a surface of the wafer and to transfer the captured image to the analyzer module, and wherein the analyzer module is configured to determine a CDU of the photo resist pattern on the wafer;
• and
• an optical system;
• and
• a development system configured to develop the photo resist layer of the wafer after a projection of a layout pattern of the reticle to generate the photo resist pattern on the wafer,
• wherein:
• the main controller is configured to command the first EUV light source to turn on, to irradiate EUV radiation from the first EUV light source, and to clean a surface of the reticle in the first reticle stage of the first exposure device by irradiating the surface of the reticle by the EUV radiation of the first EUV source for a predetermined irradiation time,
• after the cleaning, the main controller is configured to command the rapid exchange device to transfer the reticle, by the extendable robot arm, from the first exposure device to the second reticle stage of the second exposure device for lithography operation, and
• after the transferring, the main controller is configured to command the second EUV light source to turn on, to irradiate EUV radiation from the second EUV light source, and to project the layout pattern of the reticle, through the optical system, onto the photo resist layer of a wafer.