Uneven adsorption of polyethylene glycol (PEG) along a submicron feature enabling the occurrence of void-free deposition has been identified and we have developed a simplified 1-D model to explain the phenomenon based on the distribution of hydrodynamic driving force along the trench depth. We also verified this new model based on the uneven PEG adsorption via an electrochemical quartz crystal microbalance study. The model shows that with only moderate PEG concentration, void-free deposition can be realized. Some parameters used in the modeling were developed from chronopotentiometry and rotating disc electrode experiments.