Pulsed vacuum and etching systems: Theoretical design considerations for a pulsed vacuum system and its application to XeF₂ etching of Si

Rekindled interest has developed in pulsed vacuum systems due to their use for Xenon Difluoride (XeF₂) etching systems and their usefulness in the fabrication of MEMS and nanostructures. Despite numerous applications of pulsed vacuum systems, little information is available in the literature on their design considerations. In this paper mathematical models and their experimental verification are presented for various important design considerations of pulsed vacuum systems. Control of the chambers' pressures and pulse durations are typically the most important design considerations for processes involving pulsed vacuum systems. Pressure sensors give the exact pressure, but accurate chamber volumes are unknown. Thus a methodology is developed for accurate determination of chamber volumes that involves the introduction of a calibrated volume into a chamber. Then it is demonstrated that allowing a known pressure and volume of gas to move between two chambers leads to accurate temporal control of the chambers' pressures. Furthermore, by varying chambers' volumes, configurations, pressures, and the conductances between the chambers it is shown that the pulse duration could be accurately controlled. Though the model and demonstrations are presented in the context of a pulsed XeF₂ etching system, they are general and useful for all pulsed vacuum systems.