Methods for etching tungsten stack structures
AssigneeInternational Business Machines Corporation
InventorMunir D. Naeem
Life of this patent
Estimating the term…
Abstract
The invention encompasses methods for etching and/or over-etching tungsten stack structures, especially tungsten-polysilicon stack structures. The etching methods of the invention preferably employ a Cl2/NF3 etchant, optionally including O2 and/or helium. The over-etching methods of the invention preferably use a NF3/N2/O2 etchant. The methods of the invention enable effective etching of tungsten-polysilicon stacks where topographic variation is present across the substrate and/or where other tungsten stacks of different structure are also being etched.
Claims17
A method of etching at least one stack structure on a substrate, said stack structure comprising at least one layer of tungsten metal over at least one layer of polycrystalline silicon, said method comprising:
- a) providing a first stack of material layers in a first area of said substrate, said first stack comprising a patterned mask over at least one layer of tungsten over at least one layer of polycrystalline silicon wherein portions of said tungsten layer are exposed at first spaces in said patterned mask,
- b) contacting said first stack with a first gaseous etchant composition comprising Cl2, O2 and NF3 under reactive ion etching conditions to etch exposed portions of said tungsten layer.
A method of over-etching at least one stack structure on a substrate, said stack structure comprising at least one layer of tungsten metal over at least one layer of polycrystalline silicon, said method comprising:
- a) providing a first stack of material layers in a first area of said substrate, said first stack comprising a patterned mask over at least one layer of tungsten over at least one layer of polycrystalline silicon wherein portions of said tungsten layer are exposed at first spaces in said patterned mask, and
- b) contacting said stack with a gaseous etchant composition comprising N2, NF3 and O2 under reactive ion etching conditions to etch tungsten at said first spaces selective to said polycrystalline silicon layer.
A method of etching at least one stack structure on a substrate, said stack structure comprising at least one layer of tungsten metal over at least one layer of polycrystalline silicon, said method comprising:
- a) providing (i) a first stack of material layers in a first area of said substrate, said first stack comprising a patterned mask over at least one layer of tungsten over at least one layer of polycrystalline silicon over at least one layer of oxide wherein portions of said tungsten layer are exposed at first spaces in said patterned mask, and (ii) a second stack in a second area of said substrate, said second stack comprising a patterned mask over at least one layer of tungsten over at least one layer of oxide, said second stack being substantially free of any polycrystalline silicon layers between said tungsten layer and said oxide layer of said second stack, wherein portions of said tungsten layer are exposed at spaces in said patterned mask,
- b) contacting said first stack with a first gaseous etchant composition comprising Cl2 and NF3 under reactive ion etching conditions to etch exposed portions of said tungsten layer.
Dependencies are inferred from the claim text.