An anisotropic U-shaped SF6-based plasma silicon trench etching investigation

Anisotropic etching of silicon has been studied in SF6/O-2/He plasma using a multivariable experimental design. It has been found that the main monitored responses of the etching process such as silicon etch rate, selectivity of silicon over oxide, etch uniformity and etch anisotropy were influenced by a combination of independent variables. The most important variables were RF power, chamber pressure, total gas flow and oxygen content (i.e., percentage of the O-2 flow in the total gas flow). The physical and chemical explanations have been based upon the etching models obtained with the Response Surface Methodology (RSM). The models were subsequently used to optimise the etching process for trench isolation applications. The optimal values of process parameters for U-shaped 4 mu m trench etching with anisotropy of 0.97 have been found. Applications of the trenches obtained have been tested at low/high doped multilayer structures. (C) 1998 Elsevier Science B.V. All rights reserved.