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Polishing of Optical Waveguides on Si Substrate

IP.com Disclosure Number: IPCOM000115867D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Tong, F: AUTHOR

Abstract

Polishing of Si O sub 2 waveguides on Si substrate can be very difficult, owing largely to the damages incurred by the chipped pieces of Si during grinding process. Depending on the grid size used during grinding, the damage can be as large as 6&mu.m, largely distorting the beam profile emitting from the waveguide interfaces. In particular to our receiver chipset where the end face is polished at a 45 degree angle, there exist a very fragile SiO sub 2 overhanging wedge of about 20 &mu.m thick. Here, a polishing technique that uses chemo-mechanical polishing is developed which offers both high precision, quality and yield.

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Polishing of Optical Waveguides on Si Substrate

      Polishing of Si O sub 2 waveguides on Si substrate can be very
difficult, owing largely to the damages incurred by the chipped
pieces of Si during grinding process.  Depending on the grid size
used during grinding, the damage can be as large as 6&mu.m, largely
distorting the beam profile emitting from the waveguide interfaces.
In particular to our receiver chipset where the end face is polished
at a 45 degree angle, there exist a very fragile SiO sub 2
overhanging wedge of about 20 &mu.m thick.  Here, a polishing
technique that uses chemo-mechanical polishing is developed which
offers both high precision, quality and yield.

Preparation - To provide strong mechanical support, the sample is
sandwiched between two pieces Si of roughly equal dimensions.  The
width of the Si pieces have to be longer than that of the sample.
This is to provide protection at the edges of the sample.  Thin
layers (~20 &mu.m) of crystal bond are used to glue the Si
pieces with the sample.  For a 45 degrees polishing, the "sandwich"
is
placed on the jig on top of an optical flat as shown in the Figure.
Since the jig is often made of metal which has a very different
polishing rate from the Si, a flat piece of Si or SiO sub 2 is bonded
to the bottom of the jig (Figure).  Also, a thin layer of crystal
bond is applied to the grooves of the "sandwich" as shown.  This is
done to protect the Si O sub 2 surfaces from the Si debris during
grindi...