Formation of shallow trench isolation (STI)
First Claim
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1. A method of forming a shallow trench isolation comprising the steps of:
- providing a substrate having predetermined active areas and passive regions;
forming a pad oxide layer over said substrate;
forming a nitride layer over said pad oxide layer;
forming organic BARC layer over said nitride layer;
forming a first photoresist layer over said organic BARC layer;
patterning said first photoresist layer to form a first photoresist mask defining openings for at least one shallow trench to be formed in said substrate;
etching said organic BARC layer, said nitride layer and said pad oxide layer through said openings in said first photoresist mask to expose a portion of said substrate;
etching said exposed portion of said substrate to form a shallow trench in said substrate;
removing said first photoresist mask;
forming a conformal layer of oxide on the inside walls of said shallow trench;
filling said shallow trench with isolation oxide;
forming a second photoresist layer over said substrate;
patterning said second photoresist layer to form a second photoresist mask defining reverse openings corresponding to at least one active area in said substrate;
etching said isolation oxide through said reverse openings in said second photoresist mask until said organic BARC layer over said active area is reached;
removing said second photoresist mask over said substrate;
performing chemical mechanical polishing of said isolation oxide until stopping on said organic BARC layer on said substrate;
removing said organic BARC layer and said nitride layer;
performing well implanting over said substrate using pad oxide as a screen oxide;
growing low temperature oxide to anneal the surface of said substrate;
removing said pad oxide and said low temperature oxide; and
growing gate oxide layer over said substrate.
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Abstract
A method is disclosed to form a shallow trench isolation (STI) having reduced junction leakage by avoiding undercutting near the shoulder of the trench. This is accomplished by using the pad oxide as a screen oxide and not removing it by wet dip etch as is normally practiced. Instead, an extra layer of low temperature oxide is added through thermal growth, and then the resulting composite is removed together with minimal undercutting at the shoulder corners of the trench. Subsequently, gate oxide is grown thermally to complete the forming of the STI.
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Citations
33 Claims
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1. A method of forming a shallow trench isolation comprising the steps of:
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providing a substrate having predetermined active areas and passive regions;
forming a pad oxide layer over said substrate;
forming a nitride layer over said pad oxide layer;
forming organic BARC layer over said nitride layer;
forming a first photoresist layer over said organic BARC layer;
patterning said first photoresist layer to form a first photoresist mask defining openings for at least one shallow trench to be formed in said substrate;
etching said organic BARC layer, said nitride layer and said pad oxide layer through said openings in said first photoresist mask to expose a portion of said substrate;
etching said exposed portion of said substrate to form a shallow trench in said substrate;
removing said first photoresist mask;
forming a conformal layer of oxide on the inside walls of said shallow trench;
filling said shallow trench with isolation oxide;
forming a second photoresist layer over said substrate;
patterning said second photoresist layer to form a second photoresist mask defining reverse openings corresponding to at least one active area in said substrate;
etching said isolation oxide through said reverse openings in said second photoresist mask until said organic BARC layer over said active area is reached;
removing said second photoresist mask over said substrate;
performing chemical mechanical polishing of said isolation oxide until stopping on said organic BARC layer on said substrate;
removing said organic BARC layer and said nitride layer;
performing well implanting over said substrate using pad oxide as a screen oxide;
growing low temperature oxide to anneal the surface of said substrate;
removing said pad oxide and said low temperature oxide; and
growing gate oxide layer over said substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of forming a shallow trench isolation comprising:
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providing a substrate having predetermined active areas and passive regions;
forming over said substrate a pad oxide layer, a nitride layer, and a organic BARC layer in the given order;
etching through said organic BARC layer, said nitride layer, said pad oxide layer, and into said substrate to form a shallow trench in said substrate;
growing an oxide lining layer on the inside walls of said shallow trench;
depositing isolation oxide in said shallow trench;
performing reverse etching of said isolation oxide over wide active regions on said substrate until organic BARC layer is reached;
performing chemical-mechanical polishing of said isolation oxide until stopping on said organic BARC layer on said substrate;
removing said organic BARC layer and nitride layer;
performing well implanting over said substrate using pad oxide as a screen oxide;
growing low temperature oxide to anneal the surface of said substrate;
removing said pad oxide and said low temperature oxide; and
growing gate oxide layer over said substrate. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification