The invention relates to a particle-optical apparatus with a predetermined final vacuum pressure. To that end a vacuum chamber of said apparatus is via a first restriction connected to a volume where vapour or gas is present at a known pressure and via a second restriction to a vacuum pump. By making the ratio of the two conductances, associated with said restrictions, a calibrated ratio, the final pressure of the vacuum chamber is a predetermined final pressure. This eliminates the need for e.g. vacuum gauges and control systems, resulting in a more compact design of such apparatus.
Description
The invention will now be elucidated with figures, where corresponding numbers refer to corresponding features.
FIG. 1 schematically shows a particle-optical apparatus according to the invention where gas is admitted to the vacuum chamber from a volume at atmospheric pressure.
FIG. 2 schematically shows a particle-optical apparatus according to the invention where gas is admitted to the vacuum chamber from a volume at reduced pressure.
Claims
1. Particle-optical apparatus, comprising;
a vacuum chamber for containing a sample to be examined, said vacuum chamber in working being pumped down to a final pressure by a vacuum pump connected to the vacuum chamber,means for the admission of a gas or vapour to the vacuum chamber, the gas or vapour being admitted from a volume with a known pressure,where the connection of the vacuum pump to the vacuum chamber represents a first gas conductance, andthe means for the admission of the gas represent a second gas conductance, characterized in thatthe ratio of the first conductance divided by the second conductance is a calibrated ratio, said ratio calibrated to such a value that the vacuum chamber has a predetermined final pressure.
2. Particle-optical apparatus according to claim 1, in which the vacuum pump has a final pressure at least 5 times lower than the final pressure of the vacuum chamber.
3. Particle-optical apparatus according to claim 1, in which the vacuum chamber is sealed from atmosphere by a vacuum seal, said vacuum seal causing a leakage, and the means for admitting gas or vapour admit an amount of gas or vapour larger than the leakage over the seal.
4. Particle-optical apparatus according to claim 3, in which the means for admitting gas or vapour admit an amount of gas or vapour at least 5 times larger than the leakage over the seal.
5. Particle-optical apparatus according to claim 1, in which the predetermined pressure is a predetermined pressure between 0.1 and 50 mbar.
6. Particle-optical apparatus according to claim 1, in which the pressure of the volume from which the gas or vapour is admitted is atmospheric pressure.
7. Particle-optical apparatus according to claim 1, in which the volume from which the gas or vapour is admitted is connected to an inlet of a vacuum pump.
8. Particle-optical apparatus according to claim 7, in which the volume from which the gas or vapour is admitted is also connected to the outlet of another pump.
9. Particle-optical apparatus according to claim 1, in which the vapour is water vapour.
10. Particle-optical apparatus according to claim 1, in which the gas is air.
11. Particle-optical apparatus according to claim 1, in which the analysis of the sample comprises the irradiation of the sample with a beam of charged particles.
12. Particle-optical apparatus according to claim 11, in which the beam of charged particles is a focussed beam of charged particles.
13. Particle-optical apparatus according to claim 11, in which the beam of charged particles is a beam of electrons.
14. Particle-optical apparatus according to claim 11, in which the beam of charged particles is a beam of ions.
15. Particle-optical apparatus according to claim 11, in which the admitted gas comprises a precursor material for the deposition of material.
16. Particle-optical apparatus according to claim 11, in which the admitted gas comprises an etching gas.
17. Particle-optical apparatus, comprising;
a vacuum chamber for containing a sample to be examined, said vacuum chamber in working being pumped down to a final pressure by a vacuum pump connected to the vacuum chamber,an opening in the vacuum chamber for the admission of a gas or vapour to the vacuum chamber, the gas or vapour being admitted from a gas or vapour source having a known pressure,where the connection of the vacuum pump to the vacuum chamber represents a first gas conductance, andthe connection from the gas or vapour source having a known pressure to the vacuum chamber represents a second gas conductance,characterized in thatthe ratio of the first conductance divided by the second conductance is a calibrated ratio, said ratio calibrated to such a value that the vacuum chamber has a predetermined final pressure.
18. The particle-optical device of claim 17 in which the gas or vapour source with a known pressure comprises a volume with a known pressure.
19. Particle-optical apparatus according to claim 17, in which the predetermined pressure is a predetermined pressure between 0.1 and 50 mbar.
20. A method of providing a predetermined pressure in a vacuum chamber, comprising:
admitting a gas or vapour to the vacuum chamber, the gas or vapour being admitted from a volume with a known pressure through an inlet path, the inlet path having a second conductance, andremoving gas or vapour from the vacuum chamber through a connection to a vacuum pump, a connection from the vacuum chamber to the vacuum pump representing a first conductance;the quotient of the first conductance divided by the second conductance being a calibrated ratio, said ratio calibrated to such a value that the vacuum chamber has a predetermined final pressure.
21. A method according to claim 20, in which the vacuum pump has a final pressure at least 5 times lower than the final pressure of the vacuum chamber.
22. A method according to claim 20, in which the vacuum chamber is sealed from atmosphere by a vacuum seal, said vacuum seal causing a leakage, and the inlet path admits an amount of gas or vapour larger than the leakage over the seal.
Patent Application
20070176102
