走査型電子顕微鏡における電子ビーム偏向による像ノイズの低減

抄録

This paper addresses Scanning Electron Microscope (SEM). In detail, the image noise caused by the transient vibration due to the step moving of the specimen stage disturbs high throughput of the inspection, and the acoustic noise disturbs the correct shape observation of the specimen.
This paper shows a way to solve this image noise problem with the feedforward compensator using the electron beam deflection that has no risk of the oscillation. Firstly, the mechanisms how those vibrations cause the image noises are explained, and it is shown that the signal to compensate the transient vibration by step moving of the stage can be made from the low path filtered acceleration of the specimen chamber, and the signal to compensate the acoustic noise can be made from the band path filtered displacement of the specimen stage. Secondary, an electron beam deflection compensator, which uses two signals of the accelerometers, is designed. Finally, this feedforward compensator is implemented to SEM, and remarkable reductions of the image noises in the step moving of the stage and under the condition of the acoustic noise, are shown.