US 5,516,625 AGranted

Fill and etchback process using dual photoresist sacrificial layer and two-step etching process for planarizing oxide-filled shallow trench structure

AssigneeHarris Corporation

InventorsJeanne M. McNamara, Deborah K. Rodriguez, David H. Leebrick

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Abstract

To planarize an oxide-filled shallow trench-isolated semiconductor architecture, a composite photoresist sacrificial layer is initially formed on the oxide-filled structure. The composite photoresist layer contains photoresist plugs which are reflowed to fill depressions in the oxide fill layer overlying the trench, and an overlying photoresist layer which effectively planarizes the depression-filled trench oxide layer. Respective photoresist and oxide selective etching chemistries are then successively applied to first etch the composite sacrificial photoresist layer and then etch the trench fill oxide layer down to the surface of an etch stop polysilicon layer. Since the thickness of the polysilicon etch stop layer is initially formed so as to extend above the mesa layer of the trench-isolated semiconductor structure by a relatively nominal height, after planarization, the top surface of the trench fill oxide layer still extends above the surface of the mesa to prevent shorting of a subsequently formed polysilicon gate layer with underlying mesa material, while being sufficiently low enough to avoid sidewall stringer formation.

Claims12

Dependent claims

A method of forming a semiconductor structure comprising the steps of:

(a) providing a substrate having a top surface and a trench which extends from said top surface into said substrate;
(b) non-selectively forming a first layer of a first material on the structure provided in step (a) such that said first layer of said first material fills said trench and is formed on said top surface of said substrate, and wherein a depression extends from a top surface of said first layer of said first material, said depression overlying said trench;
(c) filling the depression in said first layer of said first material with a second layer of a second material such that said second layer of said second material has a top surface that substantially coincides with the top surface of said first layer of said first material;
(d) non-selectively forming a third layer of said second material on the structure resulting from step (c) such that said third layer of said second material forms a planarizing top layer structure overlying said first and second layers;
(e) etching second material of said third layer and said second layer down to the surface of said first layer;
(f) etching first material of said first layer down to the top surface of said substrate, so as to leave second material of said second layer overlying first material filling said trench;
and
(g) removing second material of said second layer overlying first material filling said trench.

5 more elements

A method of forming a semiconductor structure comprising the steps of:

(a) non-selectively forming a trench fill material layer on a trench-patterned semiconductor structure, said trench-patterned semiconductor structure containing mesa regions on which an etch stop layer has been formed and a trench pattern which extends from a top surface said trench-patterned semiconductor structure down to a prescribed depth therein, said trench fill material layer being substantially conformal with the topography of the trench-patterned surface of the underlying semiconductor structure, such that the top surface of said trench fill material layer has depressions which overlie said trench pattern, said trench fill material layer having a thickness sufficient to ensure that said depressions are located above the top surface of said mesa regions;
(b) selectively forming a plurality of photoresist plugs which fill the depressions in the top surface of said trench fill material layer and extend above the top surface of said trench fill material layer, so as to allow said photoresist plugs to be reflowed into a generally smooth and substantially planar shape that blends into an intended planar surface contour with the top surface of said trench fill material layer;
(c) reflowing said photoresist plugs into a shape which smoothly conforms with the top surface of the oxide layer;
(d) non-selectively forming a planarizing photoresist layer on the structure resulting from step (c), so as to form a composite photoresist sacrificial layer structure containing said planarizing photoresist layer and reflowed photoresist plugs;
(e) etching said composite photoresist sacrificial layer down to and terminating at the top surface of the trench fill material layer, so as to produce a planarized surface containing the top surface of said trench fill material and planarized top surface portions of said reflowed photoresist plugs that have formed in the depressions in the top surface of said trench fill material overlying said trench pattern;
(f) anisotropically etching said trench fill material layer down to and terminating at the surface of said etch stop layer, which leaves a plurality of reflowed photoresist plugs overlying said trench pattern and being coplanar with the top surface of said etch stop layer;
(g) removing said plurality of reflowed photoresist plugs overlying said trench pattern;
and
(h) removing said etch stop layer.

6 more elements

Dependencies are inferred from the claim text.