Patent Number: 
Section: claims

1. A charged particle beam apparatus comprising:a charged particle source;a charged particle optics which focuses a charged particle beam emitted from the charged particle source on a sample and performs scanning; andmeans of vacuum pumping which evacuates the charged particle optics,wherein:the means of vacuum pumping has a differential pumping structure with two or more vacuum chambers connected through an opening in series,a pump made of non-evaporable getter alloy is placed in an upstream vacuum chamber with a high degree of vacuum, anda gas absorbing surface of the non-evaporable getter alloy is fixed without contact with another part. 2. The charged particle beam apparatus according to claim 1, wherein the non-evaporable getter pump has a deposition of non-evaporable getter alloy on one side of a metal sheet. 3. The charged particle beam apparatus according to claim 1, wherein the non-evaporable getter pump is placed in the upstream vacuum chamber and the pump surface on which the non-evaporable getter alloy is deposited is on the vacuum side and the pump surface on which the non-evaporable getter alloy is not deposited is fixed in contact with an inner wall surface of the vacuum chamber with a high degree of vacuum. 4. The charged particle beam apparatus according to claim 1, wherein the side of the non-evaporable getter pump on which non-evaporable getter alloy is deposited has some areas without non-evaporable getter alloy and means for fixation is provided on the area and fixed in the upstream vacuum chamber. 5. The charged particle beam apparatus according to claim 1, wherein an additional chamber for the upstream vacuum chamber is provided and pellets made by binding non-evaporable getter alloy particles is placed in the additional chamber. 6. The charged particle beam apparatus according to claim 5, wherein a porous mesh is placed between the upstream vacuum chamber and the additional chamber. 7. The charged particle beam apparatus according to claim 5, wherein a heater is located on the lower surface of the additional chamber. 8. The charged particle beam apparatus according to claim 5, wherein a vacuum gauge is provided in the additional chamber. 9. The charged particle beam apparatus according to claim 5, wherein an opening between the additional chamber and the upstream vacuum chamber is in a position higher than the pellets. 10. The charged particle beam apparatus according to claim 1,wherein:the means of vacuum pumping has a differential pumping structure which is comprised of three or more vacuum chambers connected through an opening in series,a pump made of non-evaporable getter alloy is placed in an upstream vacuum chamber with a high degree of vacuum,a vacuum chamber which lies downstream of the upstream vacuum chamber and has a lower degree of vacuum than the upstream vacuum chamber is connected with a vacuum chamber which lies downstream of the downstream vacuum chamber and has a lower degree of vacuum than the downstream vacuum chamber through a valve which is able to adjust flow rate, anda turbo-molecular pump is provided to evacuate the vacuum chamber which has the lowest degree of vacuum. 11. A charged particle beam apparatus comprising:a charged particle source;a charged particle optics which focuses a charged particle beam emitted from the charged particle source on a sample and performs scanning; andmeans of vacuum pumping which evacuates the charged particle optics,wherein:the means of vacuum pumping has a differential pumping structure with two or more vacuum chambers connected through an opening in series, anda second pump made of grained non-evaporable getter alloy with particles on the order of less than 10 millimeters is placed in an upstream vacuum chamber with a high degree of vacuum. 12. The charged particle beam apparatus according to claim 11,wherein:a first pump made of non-evaporable getter alloy with finer particles than the grained non-evaporable getter alloy is placed in a first vacuum chamber with a high degree of vacuum located most upstream, anda second pump made of the grained non-evaporable getter alloy is placed in a second vacuum chamber which is located downstream of the first vacuum chamber and has a lower degree of vacuum than the first vacuum chamber. 13. The charged particle beam apparatus according to claim 12, wherein a gas absorbing surface of the non-evaporable getter alloy of the first pump is fixed without contact with another part, and the non-evaporable getter alloy particles of the second pump are held around a heater by mesh texture metal. 14. The charged particle beam apparatus according to claim 12, wherein the non-evaporable getter alloy of the second pump is comprised of particles of about 3 mm square. 15. The charged particle beam apparatus according to claim 14, wherein a surface of the non-evaporable getter alloy of the second pump has a convexo-concave shape with cycles of several microns to several dozen microns and has an increased effective surface area. 16. The charged particle beam apparatus according to claim 11, wherein the means of vacuum pumping has a differential pumping structure which is comprised of three or more vacuum chambers connected through an opening in series, and the vacuum chambers are connected by a rough pumping port and vacuum is controlled by a separate valve for each chamber. 17. The charged particle beam apparatus according to claim 1, wherein the charged beam source is a thermal field emitter electron gun. 18. A charged particle beam apparatus comprising:an ion source;an ion illumination optics which focuses an ion beam emitted from the ion source on a sample and performs scanning; andmeans of vacuum pumping which evacuates the ion illumination optics,a surface of the sample being processed by irradiation with the ion beam,wherein:the means of vacuum pumping has a differential pumping structure with two or more vacuum chambers connected through an opening in series,a pump made of non-evaporable getter alloy is placed in an upstream vacuum chamber with a high degree of vacuum, anda gas absorbing surface of the non-evaporable getter alloy is fixed without contact with another part. 19. The charged particle beam apparatus according to claim 18, wherein the non-evaporable getter pump has a deposition of non-evaporable getter alloy on one side of a metal sheet. 20. The charged particle beam apparatus according to claim 18, wherein the non-evaporable getter pump is placed in the upstream vacuum chamber and the pump surface on which the non-evaporable getter alloy is deposited is on the vacuum side and the pump surface on which the non-evaporable getter alloy is not deposited is fixed in contact with an inner wall surface of the vacuum chamber with a high degree of vacuum.