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, 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 grounding of the EUV mask is performed by moving a slider to drop an arm structure placed above the slider via a prop structure for moving a grounding pin attached to the arm structure from a first position to a second position to contact the EUV mask.
2. The method for inspecting an EUV mask by using a charged particle beam according to claim 1 , wherein the charged particle beam is an electron beam.
3. The method for inspecting an EUV mask by using a charged particle beam according to claim 2 , wherein a stage's moving direction is perpendicular to a scanning direction of the electron beam.
4. The method for inspecting an EUV mask by using a charged particle beam according to claim 3 , wherein the EUV mask is inspected by a low voltage scanning electron microscope.
5. The method for inspection an EUV mask by using a charged particle beam according to claim 4 , wherein said step of grounding the EUV mask is performed by contacting the grounding pin to the reflective surface of the EUV mask.
6. The method for inspection an EUV mask by using a charged particle beam according to claim 4 , wherein said step of grounding the EUV mask is performed by contacting the grounding pin to a back surface of the EUV mask, and a conductive layer is on the back surface of the EUV mask and electrically connecting to the reflective surface of the EUV mask.
7. The method for inspection an EUV mask by using a charged particle beam according to claim 6 , wherein the grounding pin contacts the back surface of the EUV mask.
8. A system for inspecting an EUV mask, wherein the EUV mask comprises a reflective surface, 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;
a grounding pin; and
a grounding pin control structure including:
a slider; and
an arm structure with a prop structure, wherein said arm structure is placed above said slider via said prop structure,
wherein said grounding pin is attached to said arm structure, and said slider moves to drop said arm structure for moving said ground pin from a first position to a second position to contact the peripheral area of the EUV mask, 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.
9. The system for inspecting an EUV mask according to claim 8 , wherein a stage's moving direction is perpendicular to a scanning direction of the electron beam.
10. The system for inspecting an EUV mask according to claim 9 , wherein the system is a low voltage scanning electron microscope.
11. The system for inspecting an EUV mask according to claim 10 , wherein the grounding pin contacts the reflective surface of the EUV mask.
12. The system for inspecting an EUV mask according to claim 10 , wherein the grounding pin contacts a back surface of the EUV mask, and a conductive layer is on the back surface of the EUV mask and electrically connecting to the reflective surface of the EUV mask.
13. The system for inspecting an EUV mask according to claim 12 , wherein the grounding pin contacts the back surface of the EUV mask.