Method of forming self-aligned contact structure with locally etched gate conductive layer

A method of forming a self-aligned contact with a locally etched conductive layer, comprising the steps of:

• (a) preparing a semiconductor substrate, the substrate having a plurality of separated gate structures formed thereon, wherein each of the gate structures comprises a first conductive layer formed on the substrate, a second conductive layer formed on the first conductive layer, and an insulating layer formed on the second conductive layer;
• (b) using a bit-line contact node photomask at the side of each gate structure used to form a bit-line contact to form a covering layer, which has at least an opening so as to expose parts of the gate structures until the top surface of the substrate is exposed;
• (c) using an etchant that has a higher etching rate to the second conductive layer than to the insulating layer and the first conductive layer to etch the second conductive layer of the exposed side of each gate structure;
• (d) removing the covering layer;
• (e) forming a sidewall spacer on each side of each gate structure;
• (f) forming a dielectric layer that covers the substrate;
• (g) performing a lithographic process and an etching process to remove the dielectric layer of the side of each gate structure used to form the bit-line contact until the top surface of the substrate is exposed so as to from a self-aligned contact;
• and
• (h) forming a metal layer that covers the etched surface of the dielectric layer and the sidewall spacers of the gate structures and forming a self-aligned contact between the metal layer and the top surface of the exposed substrate.

A method of forming a self-aligned contact window with a locally etched conductive layer, comprising the steps of:

• (a) preparing a semiconductor substrate, the substrate having a plurality of separated gate structures formed thereon, wherein each of gate structures comprises a first conductive layer formed on the substrate, a second conductive layer formed on the first conductive layer, and an insulating layer formed on the second conductive layer;
• (b) using a bit-line node photomask on the gate structures to form a covering layer that has at least a round opening so as to expose parts of the gate structures until the surface of the substrate is exposed, wherein the opening is the region used to form self-aligned contact windows;
• (c) using an etchant that has a higher etching rate to the second conductive layer than to the insulating layer and the first conductive layer to etch the second conductive layer of the exposed side of each gate structure;
• (d) removing the covering layer;
• (e) forming a sidewall spacer at each side of each gate structure;
• (f) forming a dielectric layer that covers the substrate;
• (g) performing a lithographic process and an etching process to remove the dielectric layer of the side of each gate structure used to form the bit-line contact until the top surface of the substrate is exposed so as to from a self-aligned contact window;
• and
• (h) forming a metal layer that covers the etched surface of the dielectric layer and the sidewall spacers of the gate structures and forming a self-aligned contact between the metal layer and the top surface of the exposed substrate.