Charged particle beam instrument with a specimen pre-evacuation chamber

摘要

A charged particle beam instrument is offered which has a specimen pre-evacuation chamber where damage and scattering of a specimen can be prevented. The charged particle beam instrument (100) includes the specimen chamber (10), the specimen pre-evacuation chamber (20) connected with the specimen chamber (10) via a gate valve (12), an outflow flow rate adjusting valve (70) for adjusting the flow rate of gas exhausted from the specimen pre-evacuation chamber (20), and a controller (82) for controlling the outflow flow rate adjusting valve (70). The controller (82) performs an operation for controlling the adjusting valve (70) to a first degree of opening, an operation for making a decision as to whether the difference between a first pressure in the pre-evacuation chamber (20) measured by the pressure gauge (30) before the adjusting valve (70) is controlled to the first degree of opening and a second pressure in the pre-evacuation chamber (20) measured by the pressure gauge (30) after the adjusting valve (70) has been controlled to the first degree of opening is greater than a first reference value, and an operation for controlling the adjusting valve (70) to a second degree of opening smaller than the first degree of opening if the decision is affirmative to indicate that the difference between the first and second pressures is greater than the first reference value.