Method of forming metal contact holes in semiconductor fabrication

A method for forming at least a metal contact hole through at least a dielectric layer on a substrate, comprising the steps of:

• (1) coating a photoresist layer over the dielectric layer and then forming an opening in the photoresist layer at a position over where the metal contact hole is to be formed;
• (2) performing a wet isotropic etching process on the dielectric layer through the opening so as to form a first recess portion in the dielectric layer;
• (3) performing a dry isotropic etching process on the dielectric layer through the opening and the first recess portion so as to extend the first recess portion, forming a second recess portion;
• (4) performing a dry anisotropic etching process on the dielectric layer through the opening and the second recess portion so as to form a third recess portion beneath the second recess portion, wherein the second recess portion and the third recess portion in combination form the metal contact hole;
• and
• (5) removing the photoresist layer.

A method for forming at least a metal contact hole through at least an oxide layer on a substrate, comprising the steps of:

• (1) coating a photoresist layer over the oxide layer and then forming an opening in the oxide layer at a position over where the metal contact hole is to be formed;
• (2) performing a wet isotropic etching process on the oxide layer through the opening so as to form a first recess portion in the oxide layer;
• (3) performing a dry isotropic etching process on the dielectric layer through the opening and the first recess portion so as to extend the first recess portion, forming a second recess portion;
• (4) performing a dry anisotropic etching process on the dielectric layer through the opening and the second recess portion so as to form a third recess portion beneath the second recess portion, wherein the second recess portion and the third recess portion in combination form the metal contact hole;
• and
• (5) removing the photoresist layer.