| 摘要 |
A charged particle beam instrument (such as a scanning electron microscope or SEM) 10 is disclosed comprising a charged particle optical column 12, a voltage source, a detector 14 and a sample holder 18. The column 12 is operable to direct a beam of primary charged particles (such as electrons) at a sample 20 on the sample holder 18 to cause secondary charged particles (such as secondary electrons) to be released from the sample. The voltage source operates to draw the secondary charged particles towards the detector 14 and the detector detecting the secondary charged particles. The instrument also has a further voltage source 16 variable between a first voltage that draws the secondary charged particles away from the sample, so as to prevent at least some of them from colliding with the sample 20 or sample holder 18, and a second voltage that draws the secondary charged particles towards the sample, so as to prevent at least some of them from colliding with the column 12. This increases the number of secondary charged particles detected by the detector 14. This further voltage source 16 can be applied to an electrode 17 positioned between the sample 20 and the optical column 12, the objective lens of the column or the sample holder 18. |
