Contamination issues in plasma etching of non-volatile materials: managing by-product deposition

One of the major difficulties in plasma etching of materials such as Pt, Ir, IrO₂, BST, SBT and PZT is particulate contamination resulting from the eventual flaking of nonvolatile etch by-products deposited on the reactor walls above the plane of the wafer. In-situ plasma removal of these low volatility materials has proven to be ineffective in most cases. Consequently, significant effort has been focused on managing the thickness and quality of the deposited by-products. Experiments and finite-element modeling have been used to determine reactor design criteria such as height and width to maximize the number of wafers which can be processed prior to the unacceptable yield losses associated with the flaking of the deposited etch by-products. Consequences of varying etch chemistry are also discussed