A Concentric Circular Type in-situ Vacuum Sealed Lateral Feas Employing E-Beam Evaporator
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A CONCENTRIC CIRCULAR TYPE IN-SITU VACUUM SEALED LATERAL FEAS EMPLOYING E-BEAM EVAPORATOR Moo-Sup Lim, Min-Koo Han, and *Yearn-Ik Choi School of Electrical Eng., Seoul Nat’l Univ., San 56-1, Shilimdong, Seoul, 151-742, Korea *Dep. of molecular Sci. and Tech., Ajou Univ., Suwon 442-749, Kyung-ki do, Korea
ABSTARCT In this paper, we propose concentric circular lateral field emitter structure which is more stable in fabricating and maintaining vacuum conditions. The new FEAs have concentric circular shape while our previous FEAs are stripe type. The anode is formed at inner circle and the cathode is outer circle respectively. We use Molybdenum or Silicon dioxide as a sealing material. After we fabricating tips, Molybdenum or Silicon dioxide is deposited with e-beam evaporator at base pressure of 3.5×10-6 Torr. In this process, the micro-cavity remains vacuum cavity without filling Molybdenum or oxide due to step coverage of evaporation. It should be noted that the vacuum level of the micro-cavity can be identical to the base pressure of the e-gun evaporator chamber. All of the two types of new FEAs show good reproducibility in fabricating and maintaining vacuum conditions. Field emitter structure that the anode is located at inner circle shows superior field emission characteristics. The measurements of long term stability for the anode current show that oxide is the most promising material for in-situ vacuum sealing. INTRODUCTION Vacuum field emitter arrays(FEAs) have attracted a considerable interest for high frequency, high temperature and flat pannel display applications[1,2]. Various field emitter structures have been reported to improve field emission characteristics. These reserches are focused on field emission characteristics such as emission current density, low turn-on voltage, and current stability. However, it is well known that FEAs can be operated in high-vacuum environment of about 1*10-6 Torr[3]. Therefore, most of these FEAs require an additional vacuum environments to measure its characteristics. Recently, the studys on vacuum package for FED(Field emission display) is investigated by some reserchers[4,5]. But there are few reports on sealing method for FEAs, although it is very important to apply FEAs for practical applications. We have reported in-situ vacuum sealed lateral FEAs emplyoing e-gun evaporator[6]. The structure had basically stripe shape and we used Molybdenum as sealing material. Our experiment showed that some large portion about 40% of the FEAs were failed to be sealed. It was thought that the structure had rectangular shape, and the crack of evaporated Molybdenum occurred at rectangular edges of the FEAs due to mechenical stress and poor adhesion. In this paper, we propose concentric circular type lateral field emitter structure to improve sealing and maintaining vacuum conditions. The new FEAs have concentric circular shape to reduce mechanical stress between various thin films, while our previous FEAs are stripe type. We use silicon dioxide(oxide) and Molybdenum as sealing materia
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