Patent ID: 9659874
Date: 2017-05-23
CPC Classifications: H01L

Claim:
1. A method of forming a deep trench in a semiconductor substrate, the method comprising: forming a first mask pattern over the semiconductor substrate, wherein the first mask pattern has a first opening exposing a portion of the semiconductor substrate; forming a second mask pattern over the first mask pattern, wherein the second mask pattern has a second opening substantially aligned with the first opening to expose the portion of the semiconductor substrate, and the second opening has a width greater than a width of the first opening to further expose a portion of the first mask pattern; removing the portion of the semiconductor substrate, the portion of the first mask pattern, and another portion of the semiconductor substrate beneath the portion of the first mask pattern to form the deep trench; and forming a filling material in the deep trench, the filling material having a void that is lower than an upper surface of the semiconductor substrate.