Fabrication of trenches with multiple depths on the same substrate
First Claim
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1. A method of forming an isolation structure on an integrated circuit substrate, comprising:
- providing a substrate configured so that it includes;
a silicon layer that overlies a buried oxide layer;
a pad oxide layer overlying the silicon layer; and
a nitride layer overlying the pad oxide layer;
forming a first pattern mask over the substrate such that a first pattern of apertures is formed the first pattern mask;
first etching of the nitride layer through apertures defined by the first pattern mask to form a fist set of trenches in the nitride layer having a first depth;
removing the first pattern mask;
forming a second pattern mask over the substrate that defines a second pattern of apertures in the second pattern mask;
second etching of the of the substrate through the apertures defined by the second pattern mask to form a second set of trenches of a second depth in the substrate and to extend the depth of exposed portions of the first set of trenches to a third depth; and
third etching of the of the substrate through the apertures defined by the second pattern mask to form to extend the depths of the second set of trenches to a fourth depth and to further extend the depth of exposed portions of the second set of trenches.
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Abstract
Dual trench depths are achieved on the same wafer by forming an initial trench having a depth corresponding to the difference in final depths of the shallow and deep trenches. A second mask is used to open areas for the deep trenches over the preliminary trenches and for the shallow trenches at additional locations. Etching of the shallow and deep trenches then proceeds simultaneously.
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Citations
10 Claims
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1. A method of forming an isolation structure on an integrated circuit substrate, comprising:
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providing a substrate configured so that it includes;
a silicon layer that overlies a buried oxide layer;
a pad oxide layer overlying the silicon layer; and
a nitride layer overlying the pad oxide layer;
forming a first pattern mask over the substrate such that a first pattern of apertures is formed the first pattern mask;
first etching of the nitride layer through apertures defined by the first pattern mask to form a fist set of trenches in the nitride layer having a first depth;
removing the first pattern mask;
forming a second pattern mask over the substrate that defines a second pattern of apertures in the second pattern mask;
second etching of the of the substrate through the apertures defined by the second pattern mask to form a second set of trenches of a second depth in the substrate and to extend the depth of exposed portions of the first set of trenches to a third depth; and
third etching of the of the substrate through the apertures defined by the second pattern mask to form to extend the depths of the second set of trenches to a fourth depth and to further extend the depth of exposed portions of the second set of trenches. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification