Lithium metal (Li) is electrochemically-grown at the lithium phosphorus oxynitride glass electrolyte (LiPON)/copper (Cu) thin film interface. The plated lithium morphology depends on the current densities, and larger current densities bring about smaller-sized precipitation of Li with larger coverage ratio by the precipitates. Both scanning electron microscopy and in-situ optical microscopy observations reveal that the lithium tends to grow at the lithium pre-plated place. Large potential drop was observed at the initial lithium plating process, suggesting that the nucleation process requires large activation energy at the initial lithium plating process at the LiPON/Cu interface. The resultant morphology-controlled in-situ prepared Li provides stable and low-resistive Li/LiPON interface compared with the vacuum-evaporated Li thin film.