Journal of Vacuum Science & Technology B, Vol.22, No.6, 2912-2916, 2004
Full MEMS monolithic microcolumn for wafer-level arrayal
Recently, an advanced microcolumn concept for improved throughput was proposed. However, due to the complexity of the approach, the miniaturization was limited. In addition, microcolumns must run under ultrahigh vacuum conditions in order to obtain stable electron emission at the field-emission tip. Both signal and power lines need to be connected through the ultrahigh vacuum chamber. Therefore, increases in the number of microcolumn arrays necessitated more wiring from the external control unit to the internal units, and the number of wires can become prohibitive. To solve this problem, a new concept, exploiting the possibility of an arrayed microcolumn which uses microelectromechanical systems (MEMS) technology has been developed. This paper describes a monolithic (3 X 3 arrayed) microcolumn, which consists of a cold field-emission tip, an input lens, an einzel lens, and novel deflectors for multiple-arrayed microcolumns. We also describe its fabrication process, which relies on improved microfabrication and MEMS technology, most notably multiwafer anodic bonding techniques and copper electroplating for the double metallization process. This paper describes an electro-optical analysis and an optimization using an equivalent circuit and a newly proposed simulation tool. We focus on the production possibilities for microcolumns constructed using MEMS technology. The emission current of the fabricated tungsten and molybdenum cold field-emission tip was several microamperes for an applied gate voltage of 100 V. The probe current, which was measured in the sample grid of the wafer stage, was about 1 nA. The amount of electron-beam deflection was proportional to the applied voltage at the deflector, and operated at about I mum/V. 2004 American Vacuum Society.