A method of etching an underlying inorganic substrate through a patterned photoresist, including exposing a structure comprising said inorganic substrate and patterned photoresist to a plasma etchant generated from a plasma source gas including at least one fluorine-comprising gas and sulfur dioxide. The size and configuration of the at least one sterilization barrier formed from a non-porous material are adapted to allow at least 50% of the sterilization gas, that would pass between a sterilization gas-containing exterior and the sealed interior portion when a pressure difference is created there between, to pass through the non-porous material. The first supply of high pressure fluid is in fluid communication with the clean side of the membrane during a cleaning process. The vehicle is capable of movement in any direction by rotating the axis of the drive wheels to a position which is perpendicular to the desired direction of travel. The device includes a DC offset correcting unit for removing the DC offset using an HPF function and controlling a feedback path according to a control signal to stop the HPF function and a signal generator for generating the control signal for controlling the HPF function, wherein the control signal is a signal for controlling formation and cutting-off of the feedback path.