Proposal of a miniaturized Orbitron pump for MEMS applications

The principle of the Orbitron pump is described. Its miniaturization is simulated. The application of such an ultra high vacuum pump is based on the availability of electron sources with good resistance against mbar vacuum levels. Especially field emitter cathodes are well suited to supply the active ionizing current. This electron current orbits around an anode. Ions generated along the electron path are extracted to the cathode. This is made from getter material e.g. titanium, which is sputtered by the impinging ions and in turn coats the internal surface of the pump. This generates an active getter film for chemical pumping. Employing a cathode - extractor separation smaller than I mu m allows to start the pump at a pressure as low as I mbar in the cavity. Using electron beam induced deposition, it was shown that a field emitter - extractor configuration can be built with dimensions of < 2 mu m in length, width and height. This miniaturized electron gun supplies the required current for the pump of e.g. 100 mu A. Employing micromechanical technologies, the Orbitron pump can be built and integrated into a MEMS device to supply UHV in a volume of < I Mio mu m(3) on a chip. Connecting the pump with a load vacuum volume, miniature electronic, optical, or mechanical devices, which require a continuous vacuum or even UHV, can be pumped down on chip and operated by only electrical controls.