Image quality improvement using helium gas in low voltage variable pressure scanning electron microscopy

An effective combination of the low voltage and variable pressure (VP) scan ning electron microscopy (SEM) are discussed. In low voltage VP-SEM, helium gas is utilized for reducing the amount of scatter of the primary electron beam. Most samples can receive various benefits obtained from the combinat ion of low voltage and low vacuum observation. Compared to a back-scattered electron (BSE) image in air, signal-to-noise ratio (SNR) of a BSE image ta ken with helium gas is 5.4 times under a pressure of 50 Pa and an accelerat ing voltage of 1.5 kV.