Patent ID: 8609548

Claim:
A method for etching features into an etch layer in a plasma processing chamber, wherein the etch layer is a silicon based etch layer, wherein the etch features are through silicon vias, comprising a plurality of cycles, wherein each cycle comprises: a deposition phase, comprising: providing a flow of deposition gas; forming a plasma from the deposition gas in the plasma processing chamber; providing a first bias during the deposition phase to provide an anisotropic deposition, wherein the bias during deposition phase is between 400 to 800 volts; and stopping the flow of the deposition gas into the plasma processing chamber; an etching phase, comprising: providing a flow of an etch gas; forming a plasma from the etch gas in the plasma processing chamber; providing a second bias during the etch phase, wherein the first bias is greater than the second bias, wherein the bias during the etch phase is between 0 to 200 volts; and stopping the flow of the etch gas into the plasma processing chamber; and ramping a parameter in either the deposition phase or the etch phase in a first direction over at least three cycles and ramping the parameter is a second direction opposite the first direction over at least three cycles.