Method of forming node contact opening

A method of forming a node contact opening, which is suitable for, comprising the steps of:

• providing a substrate having a dielectric layer formed thereon;
• performing a first etching step on the dielectric layer to form an opening, wherein a polymer layer is formed on a sidewall of the opening during the first etching step, and the thickness of the polymer formed on the sidewall of the opening is thicker than thickness of the polymer formed on the bottom of the opening, and wherein the first etching step comprises using an etchant comprising C4F8, Ar and CH2F2 so as to form the polymer layer during the first etching step;
• and
• performing a second etching step with the polymer layer on the sidewall of the opening used as a mask, wherein the dielectric layer exposed by the polymer layer is etched until the substrate is exposed so as to form a node contact opening.

A method of forming a capacitor of a DRAM, comprising the steps of:

• providing a substrate having a dielectric layer formed thereon;
• performing a first etching step on the dielectric layer to form an opening, wherein a polymer layer is formed on a sidewall of the opening during the first etching step, and wherein the first etching step comprises using an etchant comprising C4F8, Ar and CH2F2 so as to form the polymer layer during the first etching step;
• performing a second etching step using the polymer layer on the sidewall of the opening as a mask, wherein the dielectric layer exposed by the polymer layer is etched until the substrate is exposed so as to form a node contact opening;
• forming a first conductive layer over the substrate and filled within the node contact opening, wherein the first conductive layer serves as a bottom electrode of the capacitor
• forming a dielectric film over the first conductive layer;
• and
• forming a second conductive layer over the dielectric film, wherein the second conductive layer serves as a top electrode of the capacitor.

A method of forming a node contact opening, which is suitable for, comprising the steps of:

• providing a substrate having a dielectric layer formed thereon;
• performing a first etching step on the dielectric layer to form an opening, wherein a polymer layer is formed on a sidewall of the opening during the first etching step, and the thickness of the polymer formed on the sidewall of the opening is thicker than thickness of the polymer formed on the bottom of the opening;
• and
• performing a second etching step with the polymer layer on the sidewall of the opening used as a mask, wherein the dielectric layer exposed by the polymer layer is etched until the substrate is exposed so as to form a node contact opening, and wherein the second etching step comprises using an etchant comprising CHF3 and CO.

A method of forming a capacitor of a DRAM, comprising the steps of:

• providing a substrate having a dielectric layer formed thereon;
• performing a first etching step on the dielectric layer to form an opening, wherein a polymer layer is formed on a sidewall of the opening during the first etching step;
• performing a second etching step using the polymer layer on the sidewall of the opening as a mask, wherein the dielectric layer exposed by the polymer layer is etched until the substrate is exposed so as to form a node contact opening, and wherein the second etching step comprises using an etchant comprising CHF3 and CO that provides a high selectivity between the polymer layer and the dielectric layer;
• forming a first conductive layer over the substrate and filled within the node contact opening, wherein the first conductive layer serves as a bottom electrode of the capacitor;
• forming a dielectric film over the first conductive layer;
• and
• forming a second conductive layer over the dielectric film, wherein the second conductive layer serves as a top electrode of the capacitor.