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US 6,146,981 AGranted
Method of manufacturing buried contact in SRAM
AssigneeUnited Microelectronics Corp.
InventorMing I. Chen
Life of this patent
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Abstract
A method of manufacturing a buried contact in an SRAM includes retaining a portion of the gate oxide layer adjacent to the source/drain region when a buried contact opening is formed. The retained gate oxide layer protects the substrate by acting as a buffer region, thus preventing the over-etching of substrate, which would form a deep trench. Consequently, contact resistance between the buried contact and the source/drain region is lowered, and leakage current at the junction is prevented.
Claims17
A method of manufacturing a buried contact of an SRAM, comprising the steps of:
- providing a substrate, wherein the substrate has a device isolation structure;
- forming an oxide layer and a first conductive layer over the substrate;
- performing a first photolithographic and etching operation on the first conductive layer to form a first opening in the first conductive layer at a desired buried contact region such that the first opening exposes a portion of the oxide layer, wherein the portion of the oxide layer gets thinner due to over-etching effect in the first photolithographic and etching operation;
- performing a second photolithographic and etching operation on the portion of the oxide layer in the first opening to form a second opening that exposes the substrate such that a reserving portion of the oxide layer in the first opening adjacent to a desired source/drain region is retained;
- forming a second conductive layer such that the second conductive layer is electrically connected to the substrate through the second opening;
- performing a third photolithographic and etching operation on the second conductive layer, the first conductive layer, the oxide layer, and the substrate to form a conductive line and a gate such that a third opening between the conductive line and the gate is also formed, wherein the third opening exposes a portion of the oxide layer over the desired source/drain region and exposes the substrate over a portion of the desired buried contact region, wherein the reserving portion of the oxide layer and a portion of the substrate there-underneath are removed to form a trench in the substrate while the portion of the oxide layer over the desired source/drain region is over etched;
- and
- performing an ion implantation to implant ions into the substrate through the third opening and the trench to form a buried contact and a source/drain electrode region in the substrate at the desired buried contact region and the desired source/drain region.
5 more elements
A method of manufacturing a buried contact of an SRAM, comprising the steps of:
- providing a substrate, wherein the substrate has a device isolation structure;
- forming an oxide layer and a first conductive layer over the substrate;
- performing a first photolithographic and etching operation on the first conductive layer to form a first opening in the first conductive layer at a desired buried contact region, wherein the first opening exposes a portion of the oxide layer, at which the portion of the oxide layer gets thinner due to over-etching effect in the first photolithographic and etching operation;
- performing a second photolithographic and etching operation on the portion of the oxide layer in the first opening to form a second opening that exposes a portion of the substrate, wherein a reserving portion of the oxide layer in the first opening adjacent to a desired source/drain region is retained;
- forming a second conductive layer such that the second conductive layer is electrically connected to the substrate through the second opening;
- and
- performing a third photolithographic and etching operation on the second conductive layer, the first conductive layer, the oxide layer, and the substrate to form a conductive line and a gate such that a third opening between the conductive line and the gate is also formed, wherein the third opening exposes a portion of the oxide layer over the desired source/drain region and exposes the substrate over a portion of the desired buried contact region, wherein the reserving portion of the oxide layer and a portion of the substrate there-underneath are removed to form a trench in the substrate while the portion of the oxide layer over the desired source/drain region is over etched.
4 more elements
Dependencies are inferred from the claim text.