Process for etching oxide using a hexafluorobutadiene and manifesting a wide process window

A method of etching a hole in an oxide layer overlying a nitride layer having a nitride corner, a minimum width of said hole being 0.40 μm or less and a depth of said hole being at least 0.7 μm, comprising the steps of:

• flowing into a plasma reactor a first gas mixture comprising a first amount of a primary fluorocarbon comprising hexafluorobutadiene and a second amount of a chemically inactive diluent gas;
• from a first oscillatory power supply biasing a pedestal electrode supporting a substrate including said oxide layer overlying said nitride layer and a mask layer overlying said oxide layer to define said hole to be etched in said oxide layer;
• and
• from a second oscillatory power supply exciting said first gas mixture into a plasma to thereby etch said oxide layer selectively to said nitride layer;
• wherein said first and second amounts and power levels of said first and second power supplies are chosen to provide a process window in said first amount of ±20% in which selectivity of etching oxide to nitride is at least 10 and no etch stop occurs in said hole.

A method of etching a hole through an oxide layer to an underlying non-oxide layer, comprising the steps of:

• flowing into a plasma reactore a first gas mixture comprosing a first amount of hexafluorobutadiene and a second amount of a chemically inactive diluent gas;
• from a first oscillatory power supply biasing with a first power level a pedestal electrode supporting a substrate including said oxide layer overlying said non-oxide layer and a mas layer overylying said oxide layer to define a hole to be etched ni said oxide layer;
• from a second oscillatory power supply exciting with a second power level said first gas mixture into a plasma to thereby etch said oxide layer;
• and
• before said non-oxide layer has been reached reducing at least one of said first and second power levels.

A method of etching an oxide layer over a silicon-containing non-oxide layer in a capacitively coupled reactor, comprising the steps of:

• flowing into a plasma reactor a gas mixture comprising a first amount of a fluorocarbon gas including at least one of hexafluorobutadiene, hexafluorocyclobutene, and hexafluorobenzene and a second amount of a chemically inactive gas, said second amount being at least 15 times said first amount;
• and
• supporting a substrate containing said oxide layer over said non-oxide layer on a pedestal electrode;
• and
• applying RF power to said pedestal electrode to thereby excite said gas mixture into a plasma to thereby etch said oxide layer selectively to said non-oxide layer, wherein said plasma etches a hole in said oxide layer having an aspect ratio of at least 7/4 and wherein no etch stop occurs in said hole.

A method of etching a hole in an oxide layer overlying a nitride layer and having aspect ratio of at least 7/4, comprising the steps of:

• flowing into a plasma reactor a first gas mixture comprising a first amount of a primary fluorocarbon comprising hexafluorobutadiene and a second amount of a chemically inactive diluent gas;
• from a first oscillatory power supply biasing a pedestal electrode supporting a substrate including said oxide layer overlying said nitride layer and a mask layer overlying said oxide layer to define said hole to be etched in said oxide layer;
• and
• from a second oscillatory power supply exciting said first gas mixture into a plasma to thereby etch said oxide layer selectively to said nitride layer;
• wherein said first and second amounts and power levels of said first and second power supplies are chosen to provide in etching said hole a selectivity of etching oxide to nitride of at least 10 and no etch stop occurs in said hole.