Method and system for inspecting an EUV mask
A structure for grounding an extreme ultraviolet mask (EUV mask) is provided to discharge the EUV mask during the inspection by an electron beam inspection tool. The structure for grounding an EUV mask includes at least one grounding pin to contact conductive areas on the EUV mask, wherein the EUV mask may have further conductive layer on sidewalls or/and back side. The inspection quality of the EUV mask is enhanced by using the electron beam inspection system because the accumulated charging on the EUV mask is grounded. The reflective surface of the EUV mask on a continuously moving stage is scanned by using the electron beam simultaneously. The moving direction of the stage is perpendicular to the scanning direction of the electron beam.
1. A method for inspecting an EUV mask by using a charged particle beam, wherein the EUV mask comprises a reflective surface, the charged particle beam is an electron beam, and the reflective surface comprises a patterned reflective surface area and a peripheral area, the method comprising:
grounding the EUV mask via the peripheral area, wherein the peripheral area is electrically connected to the patterned reflective surface area;
moving continuously a stage, wherein the stage is for supporting the EUV mask, and simultaneously scanning the patterned reflective surface area of the EUV mask by using the charged particle beam; and
receiving signal electrons emanated from the patterned reflective surface area of the EUV mask;
wherein, the stage's moving direction is perpendicular to a scanning direction of the electron beam, the EUV mask is inspected by a low voltage scanning electron microscope; and
wherein, said step of grounding the EUV mask is performed by slightly contacting a grounding pin to a conductive layer on one side wall of the EUV mask, wherein a trench is formed in the side wall of the EUV mask.
2. The method for inspection an EUV mask by using a charged particle beam according to claim 1 , wherein said conductive layer is coated within said trench.
3. A system for inspecting an EUV mask, wherein the EUV mask comprises a reflective surface, the charged particle beam is an electron beam, and the reflective surface comprises a patterned reflective surface area and a peripheral area, the system comprising:
a source for providing an electron beam;
an objective lens for focusing the electron beam on the patterned reflective surface area of the EUV mask;
a detector for receiving signal electrons emanated from the patterned reflective surface area of the EUV mask;
a stage for supporting the EUV mask; and
means for grounding the EUV mask via the peripheral area, wherein the peripheral area is electrically connected to the patterned reflective surface area,
wherein the patterned reflective surface area of the EUV mask is scanned by the electron beam when the stage moves continuously;
wherein, the stage's moving direction is perpendicular to a scanning direction of the electron beam, the system is a low voltage scanning electron microscope; and
wherein, said means for grounding the EUV mask includes a grounding pin contacting a conductive layer on one side wall of the EUV mask, wherein a trench is formed in the side wall of the EUV mask.
4. The system for inspecting an EUV mask according to claim 3 , wherein said conductive layer is coated within said trench.