Surface Modification of Si Field Emitter Arrays for Vacuum Sealing
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Surface Modification of Si Field Emitter Arrays for Vacuum Sealing M. Nagao, H. Tanabe1, T. Kobayashi2, T. Matsukawa, S. Kanemaru, and J. Itoh Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba-shi, Ibaraki 305-8568, JAPAN 1 2
Dai Nippon Printing Co.,Ltd, 250-1 Wakashiba, Kashiwa-shi, Chiba 277-0871, JAPAN Musashi Institute of Technology, 1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557, JAPAN
ABSTRACT Vacuum packaging is a very important issue for vacuum microelectronics devices, especially for field emission displays. Emission current from the field emitter array (FEA), however, is known to decrease significantly after the vacuum packaging process. The current decrease is caused by heating treatment in the vacuum sealing process. In the present paper, the effect of the heating treatment on Si FEA was investigated and CHF3 plasma treatment was proposed for avoiding the problem. The Si FEA was exposed to plasma for 15sec and emission characteristics were measured before and after the vacuum sealing process using frit. It was confirmed that CHF3 plasma treatment was very effective for avoiding the emission degradation of the Si FEA. Details of the heating damage and CHF3 plasma treatment are described. INTRODUCTION Si field emitter array (FEA) is one of the most attractive devices in vacuum microelectronics because of its possibility in monolithic integration with various circuits. We have already developed a MOSFET-structured Si FEA1, which offers stable emission and can be controlled by a relatively low voltage. But its superior performance was demonstrated only in a ultra-high vacuum (UHV) chamber. For practical application of such devices, especially for field emission displays (FEDs), vacuum packaging is important technology. It is well known that emission current of FEAs decrease after the vacuum packaging process.2, 3 The vacuum packaging of the FED device is currently carried out using the frit sealing process. This process needs high temperature heating of about 450°C, and could damage the emitter surface seriously. Influence of the heating process on Spindt-type Mo-FEA has already been reported.4 Influence on Si FEA has not, however, been investigated so much. In the present study, the effect of the heating process on Si FEAs was investigated and surface modification of Si FEA was proposed in order to avoid the degradation of emission characteristics.
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EXPERIMENTS Gated cone-shaped Si FEAs were fabricated by the conventional method using reactive ion etching (RIE) and thermal oxidation sharpening.5 The FEAs having 1000 tips were mounted on TO-5 header. The FEAs were operated in DC bias mode at a pressure of 5x10-7 Pa for a few hours to stabilize the emission. After stabilization, current voltage curves were measured. Then the Si FEAs were taken out of the chamber to perform heating treatment at the temperature of 300oC for an hour in order to simulate the vacuum packaging process. The heating process was performed in 1 atm N2 gas ambient. After that, the emission characteristics in UHV were measur
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