Method of isotropically dry etching a polysilicon containing runner with pulsed power

Claim 1

A method of isotropically dry etching a WSi x /polysilicon sandwich structure atop a silicon substrate wafer containing integrated semiconductor circuits, the sandwich structure having an overlying photoresist masking portion, the method being conducted within a parallel plate reactor which in operation provides intermittent pulses of power over the parallel plates, the method comprising: injecting gases to within the reactor to provide a reactive gas mixture at a preselected pressure within the reactor, the reactive gas mixture comprising SF 6 , Cl 2 , and O 2 in approximate respective volume ratios of 10.0±5%:2.0±5%:3.0±5%; applying preselected intermittent pulses of a preselected amount of power to the parallel plates to ionize the reactive gas mixture into a plasma state, such intermittent pulses being defined by an RFon period, an RFoff period, and an RFrepeat period; the RFon period being that time period during which the preselected amount of power is applied to the plates, the RFoff period being that time period when a significantly reduced amount of power or no power is applied to the parallel plates, the RFrepeat period being the sum of a single RFon period and a single consecutively following RFoff period; subjecting the wafer to the intermittent pulses and reactive gas mixture at the preselected pressure for a preselected amount of time to isotropically etch the WSi x and polysilicon beneath the photoresist masking portion at substantially the same rate and provide a WSi x /polysilicon runner having substantially vertical sides and having resist overhang projecting laterally from the vertical sides of the WSi x /polysilicon runner.

Claim 2

A method of isotropically dry etching a WSi x /polysilicon sandwich structure atop a silicon substrate wafer containing integrated semiconductor circuits, the sandwich structure having an overlying photoresist masking portion, the method being conducted within a parallel plate reactor which in operation provides intermittent pulses of power over the parallel plates, the method comprising: injecting gases to within the reactor to provide a reactive gas mixture at a preselected pressure within the reactor, the reactive gas mixture comprising SF 6 , Cl 2 , and O 2 in approximate respective volume ratios of 10.0±5%:2.0±5%:3.0±5%; applying preselected intermittent pulses of a preselected amount of power to the parallel plates to ionize the reactive gas mixture into a plasma state, such intermittent pulses being defined by an RFon period, an RFoff period, and an RFrepeat period; the RFon period being that time period during which the preselected amount of power is applied to the plates, the RFoff period being that time period when a significantly reduced amount of power or no power is applied to the parallel plates, the RFrepeat period being the sum of a single RFon period and a single consecutively following RFoff period; subjecting the wafer to the intermittent pulses and reactive gas mixture at the preselected pressure for a preselected amount of time to isotropically etch the WSi x and polysilicon beneath the photoresist masking portion at substantially the same rate and provide a WSi x /polysilicon runner having substantially vertical sides and having resist overhang projecting laterally from the vertical sides of the WSi x /polysilicon runner.