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Process And Structure for Optical Waveguide Elements Embedded in Silicon

IP.com Disclosure Number: IPCOM000102412D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Voldman, SH: AUTHOR

Abstract

By using etching techniques which are selective for specific silicon (Si) crystal faces, a three-dimensional optical waveguide structure is embedded in a Si substrate.

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Process And Structure for Optical Waveguide Elements Embedded in Silicon

       By using etching techniques which are selective for
specific silicon (Si) crystal faces, a three-dimensional optical
waveguide structure is embedded in a Si substrate.

      Referring to the figure, a trench of width W is defined by
photolithography on single crystal Si substrate 12.  A trench of
depth d1 is anisotropically etched in Si 12. Silicon dioxide (SiO2)
is deposited conformally and anisotropically etched to form sidewall
coating 14 and then to expose Si substrate 12 at the bottom of the
trench. Preferential etching of the Si crystal face in the lateral
dimension is used to remove Si a lateral distance l and vertical
distance h = d2-d1.  Then SiO2 16 is conformally deposited.
Anisotropic etching of SiO2 is used to expose Si substrate 12.
Silicon nitride (Si3N4) is deposited conformally to fill regions 18
and anisotropic etching is used to expose Si substrate 12 again.
Then, Si 12 is etched to depth d3.  This process, beginning with
conformal SiO2 deposition, is repeated to form lower chambers 20 and
22 which are also lined with SiO2 and filled with Si3N4 .  Then, SiO2
24 is conformally deposited to fill the trench.  Finally, after
planarization, reflowable glass 26 is applied as a passivation layer.

      The two symmetrical sets of waveguide structures have Si3N4
dimensions of h and l and dielectric constant n which define a mode
of propagation.  SiO2 thickness t i...