Browse Prior Art Database

Buried Symmetric Rib Optical Waveguide Process and Structure

IP.com Disclosure Number: IPCOM000102414D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Voldman, SH: AUTHOR

Abstract

A process is described to form an optical waveguide structure below the surface of a silicon (Si) substrate and having a raised rib structure which permits coupling to surface elements. By placing the larger structure below the surface, surface area becomes available for construction of other devices, e.g., transistors. Waveguides constructed by this process have few sidewall defects and thus become efficient transmission lines.

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Buried Symmetric Rib Optical Waveguide Process and Structure

       A process is described to form an optical waveguide
structure below the surface of a silicon (Si) substrate and having a
raised rib structure which permits coupling to surface elements.  By
placing the larger structure below the surface, surface area becomes
available for construction of other devices, e.g., transistors.
Waveguides constructed by this process have few sidewall defects and
thus become efficient transmission lines.

      Referring to the figure, an opening of width W is defined by
photomasking and single crystal Si 10 is anisotropically etched to
depth d1.  Silicon dioxide (SiO2) is deposited conformally, then
etched anisotropically to form trench sidewall coating 12 and to
expose Si 10 at the bottom of the trench.  Then, Si 10 is etched
anisotropically to depth d2.  An etchant selective for the crystal
face of Si 10 exposed on the trench sidewall is used to form a
symmetric cavity.  SiO2 14 is conformally deposited next to form an
isolation layer.  Silicon nitride (Si3N4) 16 is conformally deposited
to fill the embedded waveguide cavity and the upper rib structure.
After planarization, a reflowable glass 18 may be applied as
passivation. Continued

      Materials used in the process may be varied but relationship of
dielectric constants must be held as follows:
           Region      Dielectric Constant      Relationships
           16   ...