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Thermal field electron gun immersed in magnetic lens field

Abstract：To enhance the probe beam curent of scanning electron microscopes and related devices，a thermal field electron gun immersed in a magnetic lens field was designed to collct electrons emitted from the cathode and increase the effective emittd beam current. The optical properties of the magnetic fieldimmersed thermal field electron gun were theoretically analyzed，and the performanceof three magnetic lens configurations-single polepiece，double polepiece with axial gap，and double polepiece with radial gap—was simulated and compared. A magnetic field-immersed electron gun was subsequently developed based on the double polepiece with axial gap lens，and the variations in beam spot size，beam current，and angular current density in response to the magnetic immersion lens were examined. Experimental measurements of the magnetic field distribution of the immersion lens and the efective emitted beam current of the magnetic field-immersed electron gun were conducted using a dedicated platform.Results demonstrate thatthe measured magnetic field distribution closely matches simulation predictions.The efective emitted beam current reached 44.97nA at a low acceleration voltage of 3.3kV and 638.12 nA at a high acceleration voltage of ，representing an approximate fourfold increase compared with conventional thermal field electron guns.

Key words： electron optics; thermal field electron gun; magnetic immersion lens; double polepiece lens

1引言

高亮度和高分辨一直是电子显微镜、电子束缺陷检测和电子束曝光机等电子束设备发展的目标。（剩余17807字）