Solution to wafer edge silicon needle defect of deep trench process

In design and manufacturing of power MOS microelectronic device, deep trench process is used for some special request. The trench depth reaches to scores of micrometer. some are often used in deep trench etching step. Wafer edge generates silicon grass defect. It becomes the major source of particle during the post wet clean steps, which impact line yield and contaminate wet etching tools. The paper introduces two solutions for solving this defect by optimizing trench-photo process. One is inverted trapezoid process and the other is negative resist process. Both solutions in lithography are aimed at wafer edge protection. The deep trench etching step is to protect the underground material from being damaged, and results to solve the wafer edge silicon grass defect of deep trench process.