Particle optical apparatus with a predetermined final vacuum pressure
AssigneeFEI Company
InventorsHendrik Nicolaas Slingerland, William Ralph Knowles
Life of this patent
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Abstract
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.
Claims22
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, and
- the means for the admission of the gas represent a second gas conductance, characterized in that
- the 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.
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, and
- the connection from the gas or vapour source having a known pressure to the vacuum chamber represents a second gas conductance,
- characterized in that
- the 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.
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, and
- removing 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.
Dependencies are inferred from the claim text.