Integrated sub-micron vacuum gaps in semiconductor devices

We present characterization results of integrated vacuum gaps in semiconductors and report the highest breakdown field of dielectric layers ever recorded within microfabricated semiconductor devices. Difficulties associated with the characterization of vacuum gaps in the presence of high electric fields could be overcome by using cylindrical capacitors with silicon electrodes that were manufactured with standard semiconductor technology. With this approach, breakdown fields of up to 6 × 109 V/m were achieved. The vacuum gaps of 175(5) nm were significantly smaller than the mean free path of electrons within the gap such that a breakdown due to avalanche discharge was avoided. As the voltage was increased, initially a field emission current was observed that followed a Fowler-Nordheim tunneling behavior. The tunneling current started to increase at voltages about four times greater as compared to equivalent dielectric layers of silicon oxide. At higher voltages, a mechanical breakdown occurred, where the pillars that formed the central electrode of the capacitor snapped due to electrostatic forces. We provide characteristics of thin vacuum layers, which could be useful for device design in micro- and nanoelectromechanical systems as well as semiconductor devices.