Claims
- 1. An electron beam source comprising:
(a) a photocathode comprising a photoemitter material having a work function, the photocathode comprising a beam receiving portion and an electron emitting portion; (b) a first light source to direct a first light beam onto the beam receiving portion of the photocathode to emit an electron beam from the electron emitting portion, the first light beam having a wavelength λ1 such that hc/λ1 is at least about the work function of the photoemitter material, where ‘h’ is Planck's constant and ‘c’ is the speed of light; and (c) a second light source to direct a second light beam onto the beam receiving portion of the photocathode, the second light beam having a wavelength λ2 such that hc/λ2 is less than about the work function of the photoemitter material.
- 2. An electron beam source according to claim 1 further comprising a wavelength dependent mirror to reflect the first light beam therefrom and pass the second light beam therethrough, such that the first and second light beams are collimated to overlap at the beam receiving portion of the photocathode.
- 3. An electron beam source according to claim 1 wherein the second light source generates a second light beam having a diameter of at least about 2 times a diameter of the first light beam.
- 4. An electron beam source according to claim 1 wherein the first light source is adapted to direct a plurality of first light beamlets onto a plurality of beam receiving portions of the photocathode, and the second light source is adapted to direct a second light beam that contiguously covers the beam receiving portions of the photocathode.
- 5. An electron beam source according to claim 1 wherein the first light source is adapted to direct a first light beam having a wavelength of less than about 257 nm, and the second light source is adapted to direct a second light beam having a wavelength of at least about 1060 nm.
- 6. An electron beam apparatus for generating or inspecting a pattern on a substrate, the apparatus comprising:
(a) a vacuum chamber; (b) a substrate support to support a substrate; (c) an electron beam source to provide an electron beam in the vacuum chamber, the electron beam source comprising:
(i) a photocathode comprising a photoemitter material having a work function, the photocathode comprising a beam receiving portion and an electron emitting portion, (ii) a first light source adapted to direct a first light beam onto the beam receiving portion of the photocathode to emit an electron beam from the electron emitting portion, the first light beam having a wavelength λ1 such that hc/λ1 is at least about the work function of the photoemitter material, where ‘h’ is Planck's constant and ‘c’ is the speed of light, and (iii) a second light source adapted to direct a second light beam onto the beam receiving portion of the photocathode, the second light beam having a wavelength λ2 such that hc/λ2 is less than about the work function of the photoemitter material; and (d) an electron beam focuser and scanner to focus and scan the electron beam across the substrate to generate or inspect a pattern on the substrate.
- 7. An electron beam apparatus according to claim 6 further comprising a wavelength dependent mirror adapted to reflect the first light beam therefrom and pass the second light beam therethrough, such that the first and second light beams are collimated to overlap at the beam receiving portion of the photocathode.
- 8. An electron beam apparatus according to claim 6 wherein the second light source is adapted to generate a second light beam having a diameter of at least about 2 times a diameter of the first light beam.
- 9. An electron beam apparatus according to claim 6 wherein the first light source is adapted to direct a plurality of first light beamlets onto a plurality of beam receiving portions of the photocathode, and the second light source is adapted to direct a second light beam that contiguously covers the beam receiving portions of the photocathode.
- 10. An electron beam apparatus according to claim 6 wherein the first light source is adapted to direct a first light beam having a wavelength of less than about 257 nm, and the second light source is adapted to direct a second light beam having a wavelength of at least about 1060 nm.
- 11. A method of generating an electron beam from an electron beam source comprising a photocathode having a beam-receiving portion and an electron emitting portion, the method comprising:
(a) providing a photocathode comprising a photoemitter material having a work function, the photocathode; (b) directing a first light beam onto the beam receiving portion of the photocathode to emit an electron beam from the electron emitting portion, the first light beam having a wavelength λ1 such that hc/λ1 is at least about the work function of the photoemitter material, where ‘h’ is Planck's constant and ‘c’ is the speed of light; and (c) directing a second light beam onto the beam receiving portion of the photocathode, the second light beam having a wavelength λ2 such that hc/λ2 is less than about the work function of the photoemitter material.
- 12. A method according to claim 11 further comprising reflecting the first light beam from a wavelength dependent mirror and passing the second light beam through the wavelength dependent mirror, such that the first and second light beams are collimated to overlap at the beam receiving portion of the photocathode.
- 13. A method according to claim 11 comprising generating a second light beam having a diameter of at least about 2 times a diameter of the first light beam.
- 14. A method according to claim 11 comprising directing a plurality of first light beamlets onto a plurality of beam receiving portions of the photocathode, and directing a second light beam that contiguously covers the beam receiving portions of the photocathode.
- 15. A method according to claim 11 comprising directing a first light beam having a wavelength of less than about 257 nm, and directing a second light beam having a wavelength of at least about 1060 nm.
- 16. A method according to claim 11 further comprising
(a) supporting a substrate in a vacuum zone; and (b) modulating and scanning the electron beam across the substrate to generate or inspect a pattern on the substrate.
GOVERNMENT SUPPORT
[0001] This invention was made with Government support under Contract Number N00019-97-C-2010 and Contract Number N66001-99-C-9624 awarded by the Defense Advanced Research Projects Agency of the Department of Defense and the Naval Air Systems Command (NAVAIR) of the Department of the Navy. The Government has certain rights in the invention.