Methods, systems, and articles of manufacture consistent with the present invention improve display systems by providing a non-intrusive user interface where an application displays data in a designated area of a display screen that otherwise hides the data from view. A digital pre-distorter system uses a reduced transmitter observation receiver bandwidth combined with a high transmit path sampling rate to linearize a power amplifier across a broad spectrum that may extend to beyond about five times a bandwidth of a signal input to the system. A first metal layer is formed in the contact hole preferentially with respect to formation of the first metal layer on a surface of the interlevel dielectric film opposite the integrated circuit substrate. If the sacrificial layer is removed using an etchant, the sacrificial layer at the bottom of the fixing portion is protected from the etchant by the sidewall and accordingly, the sacrificial layer except the area surrounded by the sidewall is removed. The method comprises supplying a pump and pumping water to provide a continuous flow of water from the aquarium to one or a plurality of removable filter cartridges.