Patent Number: 
Section: claims

1. A scanning electron microscope (“SEM”) comprising:an electron gun for producing an electron beam directed toward a sample;a secondary electron (“SE”) detector for detecting secondary electrons reflected from the sample in response to the electron beam;a dual-layer shield disposed around and enclosing the SE detector, the shield comprising:a magnetic shielding lamina layer; anda metallic foil layer. 2. The SEM of claim 1 wherein the magnetic shielding lamina layer comprises a highly ferro-magnetic material. 3. The SEM of claim 1 wherein the metallic foil layer comprises a highly reflective conductor. 4. The SEM of claim 1 wherein the magnetic shielding lamina layer comprises a nickel-iron alloy. 5. The SEM of claim 1 wherein the magnetic shielding lamina layer comprises one of steel plate and platinum. 6. The SEM of claim 1 wherein the metallic foil layer comprises aluminum foil. 7. The SEM of claim 1 wherein the metallic foil comprises at least one of gold foil, copper foil, and silver foil. 8. The SEM of claim 1 wherein the shield comprises the first layer disposed over the second layer. 9. The SEM of claim 1 wherein the shield comprises the second layer disposed over the first layer. 10. An apparatus for shielding a secondary electron (“SE”) detector of a scanning electron microscope (“SEM”) from effects of electromagnetic interference (“EMI”), the apparatus comprising:a dual-layer shield disposed around and enclosing the SE detector, the shield comprising:a first layer comprising a magnetic shielding lamina; anda second layer comprising a metallic foil. 11. The apparatus of claim 10 wherein the magnetic shielding lamina comprises a nickel-iron alloy. 12. The apparatus of claim 10 wherein the magnetic shielding lamina comprises one of steel plate and platinum. 13. The apparatus of claim 10 wherein the metallic foil comprises aluminum foil. 14. The apparatus of claim 10 wherein the metallic foil layer comprises at least one of gold foil, copper foil, and silver foil. 15. The apparatus of claim 10 wherein the shield comprises the magnetic shielding lamina layer disposed over the metallic foil layer. 16. The apparatus of claim 10 wherein the shield comprises the metallic foil layer disposed over the magnetic shielding lamina layer. 17. A method of shielding a secondary electron (“SE”) detector of a scanning electron microscope (“SEM”) from effects of electromagnetic interference (“EMI”), the method comprising:providing a first shielding layer around the SE detector; andproviding a second shielding layer over the first shielding layer. 18. The method of claim 17 wherein one of the first and second layers comprises a metallic foil layer and the other one of the first and second layers comprises a magnetic shielding lamina. 19. The method of claim 18 wherein the metallic foil layer comprises one of aluminum, copper, gold, and silver. 20. The method of claim 18 wherein the magnetic shielding lamina comprises one of a nickel-iron alloy, steel plate, and platinum.