New Method for Fabricating Silicon-On-Insulator Structures Using Selective Epitaxial Lateral Growth

New Method for Fabricating Silicon-On-Insulator Structures Using Selective Epitaxial Lateral Growth

       The problem of using selective epitaxial lateral growth
technique to fabricate silicon-on-insulator (SOI) structure is that
the thickness of the epi grown on the top of the insulator is
proportional to the dimensions of the insulator island.  It is very
difficult to grow a thin epitaxial film on the top of the insulator
(oxide or nitride) because the lateral epi growth rate is equal to
the vertical epi growth rate.  Although it can be polished back to
get a thinner film while growing a thick film, the film thickness is
not controllable due to the lack of the end-point or reference point
for polish stop.  Disclosed is a method using the selective epitaxial
lateral growth and chem-mech polish techniques to fabricate a
controllable, thin epitaxial film on the top of the insulator film,
therefore, a complete SOI structure can be obtained.  The structure
can be used to fabricate SOI CMOS, bipolar, or BiCMOS integrated
circuits.  Details of the fabrication process are described and
illustrated below.

      Process sequence
Grow oxide for the bottom insulator.
Deposit nitride on the oxide. The thickness of the nitride will
determine the thickness of the Si epitaxial film.
Masking step to form pattern for oxide island.
Etch nitride and oxide to define oxide island.
Grow epi selectively to the height of the insulator.
Oxidize the top of the epi film.
Remove the n...