Charged particle beam instrument

Abstract

A charged particle beam instrument is offered which can easily perform an in situ observation in a gaseous atmosphere. The charged particle beam instrument () is used to perform an observation of a specimen (S) placed in a gaseous atmosphere and has a specimen chamber (), a gas supply portion () for supplying a gas into the specimen chamber (), a venting portion () for venting the specimen chamber (), a gaseous environment adjuster (), and a gas controller () for controlling the gaseous environment adjuster (). This adjuster () has a gas inflow rate adjusting valve () for adjusting the flow rate of the gas supplied into the specimen chamber () and a first vacuum gauge (CG) for measuring the pressure of the gas supplied into the specimen chamber (). The gas controller () sets a target value of pressure for the gas supplied into the specimen chamber () based on a predetermined relational expression indicating a relationship between the reading of the first vacuum gauge (CG) and the pressure inside the specimen chamber () and on a corrective coefficient for correcting the reading of the first vacuum gauge (CG) according to the species of the gas supplied into the specimen chamber () and controls the gas inflow rate adjusting valve () such that the reading of the first vacuum gauge (CG) reaches the target value of pressure.