3D via etch development for 3D circuit integration in FDSOI

This paper describes the development of the 3D via etch process.The oxide via etch was developed in a Trikon Technologies low pressure, high density, helicon-based cluster tool. A response surface design-of-experiments (DOE) was performed varying etch pressure and wafer bias to examine their effect on etch profile and etch rates. An anisotropic etch is essential for high packing density. There was an excellent fit between the data and the model. Low pressure and high bias were required to give vertical profiles. Higher etch pressure caused excessive polymer deposition resulting in etch stop. Low wafer bias could not remove the deposited polymer fast enough, also resulting in etch stop.