Patent ID: 7122416

Claim:
A method for forming a filled trench in a semiconductor layer of a semiconductor substrate, with the effect of trench voids minimized, the method comprising the steps of: forming a trench in the semiconductor layer through a first face thereof, the trench defining an open mouth, relieving the trench adjacent the open mouth thereof for preventing the commencement of bridging of the trench with a filling material at a level adjacent the first face of the semiconductor layer as the trench is being subsequently filled, the trench being relieved adjacent the open mouth by shaping at least one side of the trench adjacent the open mouth so that the trench tapers inwardly adjacent the open mouth, the at least one side being shaped by forming at least two tapered portions adjacent the open mouth defining respective tapering planes, each tapered portion transitioning from an adjacent tapered portion, and one of the tapered portions transitioning from the side of the trench at an angle thereto, the tapering planes defined by the respective tapered portions converging towards the other side of the trench in a direction into the trench, and defining respective different relief angles with a central plane bisecting the trench and extending longitudinally along the trench through the open mouth, and filling the relieved trench through the open mouth with the filling material.