Formation of finely controlled shallow trench isolation for ulsi process

Abstract

A method for forming planarized shallow trench isolation is described. A nitride layer is deposited over the surface of a semiconductor substrate. A plurality of isolation trenches are etched through the nitride layer into the semiconductor substrate wherein there are at least one wide trench and at least one narrow trench. A first oxide layer is deposited over the first nitride layer and within the isolation trenches wherein the first oxide layer fills the isolation trenches. A capping nitride layer is deposited overlying the first oxide layer. A second oxide layer is deposited overlying the capping nitride layer. The second oxide layer is polished away wherein the second oxide layer and the capping nitride layer are left only within the wide trench. The first and second oxide layers are dry etched away with an etch stop on the capping nitride layer within the wide trench and the first nitride layer wherein the second oxide layer is completely removed. Thereafter, the first oxide layer is overetched to leave the top surface of the first oxide layer just above the bottom surface of the first nitride layer and the capping nitride layer within the wide trench. The capping nitride layer and the first nitride layer are removed completing the formation of shallow trench isolation regions in the fabrication of an integrated circuit device.