Browse Prior Art Database

Maskless Method for Shallow Trench Planarization

IP.com Disclosure Number: IPCOM000101950D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Galli, CA: AUTHOR [+3]

Abstract

A procedure is proposed whereby a self-aligned etch stop mask is employed to form shallow, wide and planarized trenches in a substrate. The disclosed process achieves a good surface planarization without the need for an additional photoresist block-out mask.

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Maskless Method for Shallow Trench Planarization

       A procedure is proposed whereby a self-aligned etch stop
mask is employed to form shallow, wide and planarized trenches in a
substrate.  The disclosed process achieves a good surface
planarization without the need for an additional photoresist
block-out mask.

      Planarization (by chemical-mechanical polishing) of wafers
having only sparsely (or unevenly) populated features to be polished
is made difficult by the unwanted removal of materials in the
background of such features due to "dishing out" of the polishing
pad.  This problem can be avoided by using an etching block (a
photoresist mask) in the background to protect the wanted material
during polishing, e.g., a nitride etch stopper can be formed in the
wide trench area when planarizing a poly- silicon wafer, but this
requires the use of an additional photolithographic step to form the
etch stop layer.  This layer can, however, be formulated,
self-aligned to the feature to be polished without an additional
photomask by the method illustrated in Figs. 1 to 5, using silicon
planarization as an example.  The disclosed method is equally useable
for other materials, such as a Si02 shallow trench.

      The wafer with trenches 1 and Si3N4 surface 2 is shown in Fig.
1 after a polysilicon deposition 3.  It is then coated with a layer
of Si3N4 4 of proper thickness and a thicker photoresist coating 5,
which is reflowed to smooth out the surface topogr...