United Silicon Incorporated

United Microelectronics Corp.

Chin-Hung Tseng

Chih-hsun Chu

A method for recovering the alignment mark on a substrate to the top of a dielectric layer. The method includes the steps of forming a dielectric layer over a substrate, and then forming a cap layer over the dielectric layer. The cap layer fills the trench in the dielectric layer directly above the alignment mark and covers the area surrounding the trench. Thereafter, a global planarization is carried out to remove the top portion of the cap layer. Finally, the remaining portion of the cap layer is removed to expose the dielectric layer so that an alignment mark re-emerges on top of the dielectric layer.

Method for restoring an alignment mark after planarization of a dielectric layer

A method for fabricating a dielectric layer in an alignment marker area is provided. A wafer having an alignment marker area is formed. The alignment marker area has large trenches and small trenches formed in the wafer. A dielectric layer is formed over the wafer. Portions of the dielectric layer directly above the large trenches in the alignment marker area are removed to form trench structures.

Method of fabricating dielectric layer in alignment marker area

A method of manufacturing a shallow trench isolation alignment mark comprises the steps of first providing a silicon wafer whose surface has an alignment mark formed thereon. Next, a silicon nitride layer is formed over the silicon wafer, and then shallow trenches are formed. At least one of the shallow trenches is positioned at a distance of about 2000 .ANG. to 10000 .ANG. from the edge of the alignment mark. Thereafter, an oxide layer is formed over the silicon nitride layer, and then a chemical-mechanical polishing operation is conducted to remove a portion of the oxide layer and silicon nitride layer above the alignment mark. Altogether, a layer of silicon nitride having a thickness of about 600 .ANG. is removed from the top of the alignment mark. Finally, the silicon nitride layer is also removed. By forming a shallow trench at a distance of between 2000 .ANG. to 10000 .ANG. from the edge of an alignment mark, accurate overlaying of mask can be achieved without the need for performing additional oxide clearout operations.

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Hsinchu, Taiwan

Chin-Hung Tseng