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Reactive ion etching of openings in insulating layers of nitride and oxide using block-out masks is achieved without thinning of the nitride when defining fine geometry patterns.
English (United States)
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Masking Technique for Reactive Ion Etching
Reactive ion etching of openings in insulating layers of nitride and oxide
using block-out masks is achieved without thinning of the nitride when defining
fine geometry patterns.
A 1600-1800 Angstrom thick layer of pyro oxide is deposited over the silicon
nitride layer, followed by a layer of resist which is patterned to uncover the
portions of the layers to be etched. The pyro oxide and nitride are then etched in
a CF(4) plasma, stopping at the surface of the underlying SiO(2), and the resist is
stripped in oxygen.
A resist block-out mask is then formed to uncover portions of underlying
SiO(2) which are to be etched to open up the substrate for diffusion while
protecting other SiO(2) areas where no diffusion is desired. The resist mask is
not precisely aligned with the previous openings in the pyro oxide and nitride
The underlying SiO(2) is then reactively ion etched in a diode system through
the resist mask with a gas mixture which does not significantly attack silicon.
The overlying pyro oxide layer protects the silicon nitride layer from being thinned
during the SiO(2) etching process.
This block-out resist masking and etching process can be repeated to open
up other SiO(2) areas for appropriate device fabrication purposes.